Technology and basic methods of welding cast iron
Composition and Properties of Iron
examine the properties of cast iron, which determine the specificity
Marking of Iron
Iron is marked by the letters MF and ...
Basic Information on Weldability and Technological Advice
introduction of technological recommendations for welding of cast iron
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
gives a graphical scheme to see the thermal effect on the weld, the temperature distribution
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
high rate of cooling after welding is observed
The Technological Process of Hot Welding
technology process of welding cast iron. The choice of welding
Cold Welding of Cast Iron with Simple Electrodes
composition description of the electrodes, wires, and methods of producing cast iron in the weld
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color
for joints having sufficient ductility in the cold state, apply the electrodes to ensure receipt of the weld metal alloys based on copper and nickel
Welding of Cast Iron
Showing posts with label welding of cast iron. Show all posts
Showing posts with label welding of cast iron. Show all posts
1:46 AM
1:29 AM
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color
for joints having sufficient ductility in the cold state, apply the electrodes to ensure receipt of the weld metal alloys based on copper and nickel
Cold welding electrodes, cast iron, providing the receipt of the weld metal non-ferrous and special alloys
For joints that have a sufficiently high ductility in the cold state, apply the electrodes to ensure receipt of the weld metal alloys based on copper and nickel. Copper and nickel do not form compounds with carbon, but their presence in the alloy reduces the solubility of carbon in iron and promotes graphitization. So, getting into the zone of partial melting, adjacent to the seam, they reduce the probability of bleaching. In addition, the ductility of the weld metal contributes to a partial relaxation of welding stresses, and therefore reducing the likelihood of cracking in the HAZ. For welding of cast iron used mednozheleznye, mednonikelevye and iron-nickel electrodes.
There are several types of copper and iron electrodes.
One. The copper rod with a braided sheet thickness 0.25 - 0.3 mm, which is in the form of 5-7 mm width tape wound on a core of the helix. Applied to the ionizing electrode or a thick coating. The electrode with a rod made of a combination of wire, which is a core of steel wire, tightly pressed into a copper tube manufactured on the machines for the production of cored wire.
It may also be another option: a copper core with a steel shell. All varieties of iron content in the weld metal should not exceed 10-15%, because otherwise the seam formed (in large quantities) is very solid inclusions of iron with high carbon content, adversely affect the workability and reduce the ductility of the joint.
Two. The beam of the electrodes, consisting of one or two copper rods and a steel electrode with a protective coating of any brand. The beam connected to the four or five places and the copper wire on the end inserted into the electrode, we catch for a good contact between all the bars.
Three. The most advanced among the copper-iron electrodes - electrodes OZCH grade-1, representing a copper rod with a diameter of 4-5 mm, on which a coating consisting of a dry powder coating SSSI-13 (50%) and iron powder (50%), zameshennyh on liquid glass.
Copper-iron alloy in the joint can also be obtained when welding copper electrodes on a special layer of flux, which consists of calcined borax (50%), caustic soda (20%), iron scale (15%) and iron powder (15%). Flux poured a layer thickness of about 10 mm, the arc melted, continue stirring as the arc between copper electrode and the molten flux.
Welding electrodes, copper and iron of all kinds should be carried out in such a way as to avoid strong heating of the welded parts: the lowest possible currents, providing a stable arcing, short sections of randomly, with interruptions for cooling the workpiece.
The main advantage of these electrodes - the possibility of forging weld metal in the hot state to reduce the level of welding stresses. Forging is required, since this decreases the risk of cracking in the weld zone.
The general lack of copper-iron electrodes - a heterogeneous structure of joint: soft copper base and a solid component of the inclusion of iron, hinder or prevent the processing of obtaining a high purity of the treated surface. Some have better machinability joints, electrodes made of mark Anch-1, a core consisting of austenitic steel grade St-04H18N9 and the copper shell. The electrode coated ftoristokaltsievogo type.
The most efficient use of copper-iron electrode for welding defects not through individual or small leaks, creating a leak responsible for casting purposes, including working under pressure (flanges, bearings).
Copper-nickel electrodes in production is mainly used for welding casting defects detected during the machining of cast iron on the working surfaces, where the local increase in hardness is not allowed. The positive properties of these electrodes is that the nickel and copper do not dissolve carbon and do not form a structure having a high hardness after heating and rapid cooling. Whitening zone of partial melting at small sizes it is virtually absent, as copper and nickel - elements - grafitizatory, getting into this area to have a positive effect: at the same time, nickel and iron have unlimited solubility, facilitating reliable fusion.
For the manufacture of electrodes and the use of copper-nickel alloys: Monel - Metal containing 65-75% Ni, 27-30% Cu, 2-3% Fe and 1.2-1.8% Mn (eg, NMZhMts 28-2, 5-1,5), Constantan, containing ~ 60% Ni and ~ 40% Cu (MNMts 40-1,5), nichrome (Cr20Ni80).
The disadvantages of these alloys - their high cost and scarcity, as well as a large shrinkage, leading to the formation of hot cracks. Hot cracks sometimes look like a solid mesh, which reduces the strength of the weld. In this regard, these alloys are not recommended for welding cracks in the products that carry the power load. Welding same individual small bowls can get good results, as it provides a possibility of subsequent machining.
Are used in industrial electrodes makes MOF-1 with the rod of monel metal, and MOF-2 with a rod of constantan. Both brands have a kind of Electrode coatings F. Weld perform electrodes with a diameter of 3-4 mm, thread, seam, short sections, with the reciprocating movement of the electrode, preventing overheating of parts, which are recommended to cool breaks. Bead while hot should be carefully prokovyvat light strikes the hammer. For welding some small defects on the machined surfaces of castings responsible use of gray and ductile cast iron defects identified on the machined surfaces of products and equipment for repair of cast iron, iron-nickel electrodes are also used with the core of an alloy containing 40-60% Ni and 60 -40% Fe.
When welding electrodes so provided a sufficiently high strength and a toughness of the weld metal. Iron-nickel electrodes offer certain advantages, among which, besides high strength can be attributed less than that of copper-nickel alloys, casting shrinkage, surfacing with a one-color iron. An example of this type of electrode can serve as electrodes TSCH brand-OF rod with wire Sv-08N50 and coated with dolomite (35%), fluorspar (25%), graphite, black (10%) and ferrosilicon (30%), liquid zameshennyh glass.
You should always keep in mind that all the electrodes containing nickel, scarce and can be used for welding cast iron is limited, such as welding of small shells, exposed in the last machining operation, the details of large size and high stiffness.
See also:
Welding of Cast Iron
Composition and Properties of Iron
Marking of Iron
Basic Information on Weldability and Technological Advice
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
The Technological Process of Hot Welding
Cold Welding of Cast Iron with Simple Electrodes
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color
Cold welding electrodes, cast iron, providing the receipt of the weld metal non-ferrous and special alloys
For joints that have a sufficiently high ductility in the cold state, apply the electrodes to ensure receipt of the weld metal alloys based on copper and nickel. Copper and nickel do not form compounds with carbon, but their presence in the alloy reduces the solubility of carbon in iron and promotes graphitization. So, getting into the zone of partial melting, adjacent to the seam, they reduce the probability of bleaching. In addition, the ductility of the weld metal contributes to a partial relaxation of welding stresses, and therefore reducing the likelihood of cracking in the HAZ. For welding of cast iron used mednozheleznye, mednonikelevye and iron-nickel electrodes.
There are several types of copper and iron electrodes.
One. The copper rod with a braided sheet thickness 0.25 - 0.3 mm, which is in the form of 5-7 mm width tape wound on a core of the helix. Applied to the ionizing electrode or a thick coating. The electrode with a rod made of a combination of wire, which is a core of steel wire, tightly pressed into a copper tube manufactured on the machines for the production of cored wire.
It may also be another option: a copper core with a steel shell. All varieties of iron content in the weld metal should not exceed 10-15%, because otherwise the seam formed (in large quantities) is very solid inclusions of iron with high carbon content, adversely affect the workability and reduce the ductility of the joint.
Two. The beam of the electrodes, consisting of one or two copper rods and a steel electrode with a protective coating of any brand. The beam connected to the four or five places and the copper wire on the end inserted into the electrode, we catch for a good contact between all the bars.
Three. The most advanced among the copper-iron electrodes - electrodes OZCH grade-1, representing a copper rod with a diameter of 4-5 mm, on which a coating consisting of a dry powder coating SSSI-13 (50%) and iron powder (50%), zameshennyh on liquid glass.
Copper-iron alloy in the joint can also be obtained when welding copper electrodes on a special layer of flux, which consists of calcined borax (50%), caustic soda (20%), iron scale (15%) and iron powder (15%). Flux poured a layer thickness of about 10 mm, the arc melted, continue stirring as the arc between copper electrode and the molten flux.
Welding electrodes, copper and iron of all kinds should be carried out in such a way as to avoid strong heating of the welded parts: the lowest possible currents, providing a stable arcing, short sections of randomly, with interruptions for cooling the workpiece.
The main advantage of these electrodes - the possibility of forging weld metal in the hot state to reduce the level of welding stresses. Forging is required, since this decreases the risk of cracking in the weld zone.
The general lack of copper-iron electrodes - a heterogeneous structure of joint: soft copper base and a solid component of the inclusion of iron, hinder or prevent the processing of obtaining a high purity of the treated surface. Some have better machinability joints, electrodes made of mark Anch-1, a core consisting of austenitic steel grade St-04H18N9 and the copper shell. The electrode coated ftoristokaltsievogo type.
The most efficient use of copper-iron electrode for welding defects not through individual or small leaks, creating a leak responsible for casting purposes, including working under pressure (flanges, bearings).
Copper-nickel electrodes in production is mainly used for welding casting defects detected during the machining of cast iron on the working surfaces, where the local increase in hardness is not allowed. The positive properties of these electrodes is that the nickel and copper do not dissolve carbon and do not form a structure having a high hardness after heating and rapid cooling. Whitening zone of partial melting at small sizes it is virtually absent, as copper and nickel - elements - grafitizatory, getting into this area to have a positive effect: at the same time, nickel and iron have unlimited solubility, facilitating reliable fusion.
For the manufacture of electrodes and the use of copper-nickel alloys: Monel - Metal containing 65-75% Ni, 27-30% Cu, 2-3% Fe and 1.2-1.8% Mn (eg, NMZhMts 28-2, 5-1,5), Constantan, containing ~ 60% Ni and ~ 40% Cu (MNMts 40-1,5), nichrome (Cr20Ni80).
The disadvantages of these alloys - their high cost and scarcity, as well as a large shrinkage, leading to the formation of hot cracks. Hot cracks sometimes look like a solid mesh, which reduces the strength of the weld. In this regard, these alloys are not recommended for welding cracks in the products that carry the power load. Welding same individual small bowls can get good results, as it provides a possibility of subsequent machining.
Are used in industrial electrodes makes MOF-1 with the rod of monel metal, and MOF-2 with a rod of constantan. Both brands have a kind of Electrode coatings F. Weld perform electrodes with a diameter of 3-4 mm, thread, seam, short sections, with the reciprocating movement of the electrode, preventing overheating of parts, which are recommended to cool breaks. Bead while hot should be carefully prokovyvat light strikes the hammer. For welding some small defects on the machined surfaces of castings responsible use of gray and ductile cast iron defects identified on the machined surfaces of products and equipment for repair of cast iron, iron-nickel electrodes are also used with the core of an alloy containing 40-60% Ni and 60 -40% Fe.
When welding electrodes so provided a sufficiently high strength and a toughness of the weld metal. Iron-nickel electrodes offer certain advantages, among which, besides high strength can be attributed less than that of copper-nickel alloys, casting shrinkage, surfacing with a one-color iron. An example of this type of electrode can serve as electrodes TSCH brand-OF rod with wire Sv-08N50 and coated with dolomite (35%), fluorspar (25%), graphite, black (10%) and ferrosilicon (30%), liquid zameshennyh glass.
You should always keep in mind that all the electrodes containing nickel, scarce and can be used for welding cast iron is limited, such as welding of small shells, exposed in the last machining operation, the details of large size and high stiffness.
See also:
Welding of Cast Iron
Composition and Properties of Iron
Marking of Iron
Basic Information on Weldability and Technological Advice
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
The Technological Process of Hot Welding
Cold Welding of Cast Iron with Simple Electrodes
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color
1:21 AM
Cold Welding of Cast Iron with Simple Electrodes
composition description of the electrodes, wires, and methods of producing cast iron in the weld
Cold welding of cast iron with simple electrodes designed for welding cast iron hot, does not provide positive results, since at high cooling rates, corresponding to the given conditions of welding, a structure of white cast iron in the weld and heat affected zone of high-temperature region, and is a sharp hardening of the metal base stations heat-affected zone, heated in the welding process temperature above Ac 3 . The resulting strain with the ability to exceed the deformation of the weld metal and heat affected zone, resulting in cracks.
To prevent bleaching is necessary to provide such a composition of the weld metal, for which these conditions will be obtained structure of gray cast iron with the most favorable form of graphite inclusions. This can be achieved by introducing into the weld metal is sufficiently large amount of iron and alloying grafitizatorov elements contributing to the spheroidization of carbides (magnesium). An example of such electrodes can serve as electrodes EMCH brands, the rod which is iron with a high (up to 5.2%) silicon content, covering a two-layer: first layer - dopant, the second - provides gas and slag protection:
1st layer
Graphite - 41%
Silikomagny - 40%
Iron scale - 14%
Aluminum (powdered) - 5%
2nd layer
Marble - 50%
Fluorspar - 50%
(The relative weight of each layer - 15-20%)
When these electrodes welding of cast iron parts with wall thickness up to 12 mm without preheating can get the seams and weld zone without bleaching and quenching. Slow the rate of cooling at the eutectic temperature promotes the reaction between iron powder and aluminum dross, which flows with heat release. When welding electrodes, these massive parts for defect-free welds have to warm up to a temperature of 400 ° C depending on the thickness and hardness of cast iron products. To improve the workability and the slight increase in ductility of the weld metal using electrodes made of nickel-iron, such as Ni-resist or nikrosilalya.. composition of the electrode rods of nickel pig iron,%
The electrodes are made of nickel iron joints ensure receipt, having a good workability. Coating applied to the rods of nickel pig iron is recommended the following composition: 55% of silicon carbide, barium carbonate 23.7%, 21.3% sodium silicate. The coating thickness should be 0.5-0.8 mm in the direction of the use of rods with a diameter of 7-8 mm. Welding is performed in several layers, with the reciprocating movement of the electrode. The main drawback of the nickel-iron electrodes - an increased tendency to hot cracking.
Get in the weld metal and weld metal can be cast iron, using special welding materials, which provide a doping electrode surface. Examples of such materials can serve as electrodes, which rod is made of low carbon wire, such as stamps, or CB-08 CB-08A in accordance with GOST 2246-70, and the dopant coating contains a sufficient number of elements grafitizatorov - carbon and silicon. The most characteristic mark EMCHS electrodes, the core of which consists of a low-carbon electrode wire and the coating of three layers:
1st layer
Graphite - 50% Silikomagny - 41% Hematite - 6% Aluminum (powder) - 1.5% Bentonite - 1.5%
2nd layer:
Marble - 50% of fluorspar - Bentonite 47.5% - 2.5%
Third layer
Graphite - 100%
The electrodes are made by sequential deposition coating, zameshennoy liquid glass, the thickness of each layer should provide the relative weight of 1st layer of 25 - 30% of 2 - and third - 10-15%. As can be seen from the above coating composition, the 1st layer is the alloying, 2nd slag and gaseous, 3rd - gas protection. Graphite and silikomagny belonging to the 1st layer are grafitizatorami, and magnesium, to some extent contributes to spheroidization of graphite, hematite, and aluminum, engaging in interaction, contribute to some reduction in the rate of cooling at the eutectic temperature, thereby obtaining the structure in the weld cast iron.
The application of these electrodes for welding of cast iron products with a relatively small thickness of the welded metal (up to 8 - 10 mm) allows to obtain high quality welds without preheating of the product; at large thicknesses should be used for semi welding. And cold welding of cast iron for semi automatic, semiautomatic and mainly use a special flux cored wires to ensure getting in the seam of gray cast iron. For cold-welding products with relatively small wall thickness (in place of welding) wire is recommended brands HRE-1, the welding-wire for semi CFR-2.
Mechanized welding flux cored wire produces weld metal and weld metal, similar in composition and structure of welded cast iron. When tea leaves large defects in iron castings, which is necessary to fix a large amount of metal afloat, as well as in the manufacture of large bulky items from high-strength cast iron with nodular graphite can be used electroslag welding plate electrodes, representing a cast iron plate with the contents of the corresponding elements grafitizatorov ( carbon and silicon) is equal to the last content in the electrode rods grades A and B, and 0,04 - 0,08% Mg.
In electroslag welding of cast iron used fluoride and non-oxidative desulfurizing flux. Slow cooling of the weld metal and heat affected zone, which is characteristic for electroslag welding produces welds with no bleached and hardened areas, cracks, pores and other defects. Electroslag welding provides a satisfactory mechanical properties of welded joints of cast iron and its good workability.
In addition to the total heat applied during welding for semi variety of ways, in some cases, when the rigidity of the product is relatively small, we can restrict ourselves to local heating to the desired temperature. During the welding process is necessary to pay attention to the fact that the product is not in the weld cooled below the set temperature heating.
Cold welding electrodes, cast iron, provides in low-carbon steel weld metal
If you run surfacing on cast iron electrodes designed for welding of carbon or low alloy structural steels, the 1-m layer, even with a relatively small percentage of participation of the base metal will high-carbon steel, which is at cooling rates that occur in welding without preheating the product, acquires sharp hardening. Therefore, the metal 1 layer will have a high hardness, low deformation capacity and will be prone to the formation of cold cracks and porosity. In the 2nd layer, of course, the share of iron is reduced, but the carbon content in it will be still at a high level, which will also lead to hardening and eventual cracking. Subsequent layers of the share of iron to be insignificant, and the weld metal will have a certain level of plasticity.
In connection with the foregoing, such steel electrodes can be used only for decorative welding of the small size of defects, if the weld is not subject to requirements to ensure the strength, density and workability of the cutting tool. In order to reduce the stake of the base metal in the weld and heat affected zone sizes, including the areas of bleaching and quenching, small diameter electrodes are used (for the 1st layer of 3 mm, for the 2nd and subsequent 3-4 mm) at low currents [Isv = (20-25) de, without overheating the base metal.
First performed facing the 1st layer. Welding is performed in short segments, ridges small sections [F = (6-8) de] randomly at intervals to cool the weld and heat affected zone to a temperature of 50-60 ° C. In a second layer applied to the 2nd transverse ridges, then 3 - First, after the third layer can be applied to multiple modes of higher energy per unit length, but also with interruptions to the heating zone was a small iron. To reduce the stresses are useful in forging middle-class.
When welding low-carbon iron electrodes the most general weak spot weld - the weld zone at the fusion boundary. The fragility of this area and the presence of cracks in it often leads to peeling of the seam of the base metal. To increase the strength of the welded joint, when it is not imposed on other requirements (such as repairing frames, frames, brackets and other load-bearing elements of thick-walled structures), used steel studs, which are partially unload the weakest part of the weld - a line of fusion.
Studs are threaded, they vvertyvayut the body part to be welded. Size of studs are usually dependent on the thickness of the workpiece. Practice, the following recommendations: diameter 0.3-0.4 stud thickness of parts, but not exceeding 12 mm, depth 1.5 diameter rods vvertyvaniya them, but no more than half the thickness of the workpiece, the height of the protruding part of 0,75-1,2 diameter studs. Studs are placed in a checkerboard pattern on the beveled edges of the parts in a row on the surface of the part on each side of the junction, the distance between them must be equal to 6.4 diameters of the pins.
Welding is performed in the following order. First scald each pin and the surface of the veneer edges electrodes 3 mm in diameter at low currents. Then, on the edge of the first hairpin coated bead and fill in a breaker, as in the previous case. To reduce the carbon content in the weld metal invited to perform welding on a layer of flux containing 30% iron scale (eg, borax 50%, 20% caustic soda, iron dross 30%). Carbon entering the weld pool, in the high part of it is actively oxidized and removed from it in the form of carbon monoxide, are not soluble in the metal. As a result, the concentration of carbon at the time of solidification of the weld pool is reduced. Hardness of weld metal decreases, the deformation capacity increases.
However, for more complete burning of the effect of carbon is necessary to use welding regimes, characterized by relatively high energy per unit length, which, however, affects the heat-affected zone: it formed a significant-sized areas of bleaching and quenching, leading to the formation of cracks. When welding cast iron with a fairly high content of elements grafitizatorov with a small wall thickness of welded parts can get positive results.
More successful was the other way. In the weld metal is introduced strong karbidoobrazovatel - vanadium. In this case, the carbides are formed mainly of the element does not dissolve in iron and having a non-solid form of fine particles. Metal base in this case is decarburized and enough plastic. An example is the mark electrodes TSCH-4 with a rod of low carbon wire marks, or CB-08 CB-08A and cover the following composition: 12% of marble, fluorspar 16%, 66% ferrovanadium, ferrosilicon 4% and 2% potash, liquid glass 30 % by weight of dry mixture. The metal deposited by these electrodes have the following composition: 0.15% C, up to 0,6% Si; 0,5% Mn; 8,5-10,5% V; sulfur and phosphorus to 0.04% each. These electrodes first veneer edge at low currents [Isv = (20-25) de]. Welding is performed by parallel ridges with overlapping each previous half its width. After a 2-layer current strength increased by 15-20%, a breaker completely filled electrodes UONI-13/45.
Scope of the electrodes - Welding of damaged parts and welding defects in castings from gray and ductile iron. If necessary, you can also weld connections of gray and ductile cast iron to steel. Welds made these electrodes have satisfactory workability, density and relatively high strength. By ways of ensuring the receipt of the weld metal of low carbon steel may also include mechanized welding short sections of the electrode wire Sv-08GS marks, or St-08G2S diameter of 0,8-1 mm in carbon dioxide. Welding current of 50-75 A, arc voltage 18-21 V, welding speed 10-12 m / h
See also:
Welding of Cast Iron
Composition and Properties of Iron
Marking of Iron
Basic Information on Weldability and Technological Advice
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
The Technological Process of Hot Welding
Cold Welding of Cast Iron with Simple Electrodes
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color
Cold welding of cast iron with simple electrodes designed for welding cast iron hot, does not provide positive results, since at high cooling rates, corresponding to the given conditions of welding, a structure of white cast iron in the weld and heat affected zone of high-temperature region, and is a sharp hardening of the metal base stations heat-affected zone, heated in the welding process temperature above Ac 3 . The resulting strain with the ability to exceed the deformation of the weld metal and heat affected zone, resulting in cracks.
To prevent bleaching is necessary to provide such a composition of the weld metal, for which these conditions will be obtained structure of gray cast iron with the most favorable form of graphite inclusions. This can be achieved by introducing into the weld metal is sufficiently large amount of iron and alloying grafitizatorov elements contributing to the spheroidization of carbides (magnesium). An example of such electrodes can serve as electrodes EMCH brands, the rod which is iron with a high (up to 5.2%) silicon content, covering a two-layer: first layer - dopant, the second - provides gas and slag protection:
1st layer
Graphite - 41%
Silikomagny - 40%
Iron scale - 14%
Aluminum (powdered) - 5%
2nd layer
Marble - 50%
Fluorspar - 50%
(The relative weight of each layer - 15-20%)
When these electrodes welding of cast iron parts with wall thickness up to 12 mm without preheating can get the seams and weld zone without bleaching and quenching. Slow the rate of cooling at the eutectic temperature promotes the reaction between iron powder and aluminum dross, which flows with heat release. When welding electrodes, these massive parts for defect-free welds have to warm up to a temperature of 400 ° C depending on the thickness and hardness of cast iron products. To improve the workability and the slight increase in ductility of the weld metal using electrodes made of nickel-iron, such as Ni-resist or nikrosilalya.. composition of the electrode rods of nickel pig iron,%
The electrodes are made of nickel iron joints ensure receipt, having a good workability. Coating applied to the rods of nickel pig iron is recommended the following composition: 55% of silicon carbide, barium carbonate 23.7%, 21.3% sodium silicate. The coating thickness should be 0.5-0.8 mm in the direction of the use of rods with a diameter of 7-8 mm. Welding is performed in several layers, with the reciprocating movement of the electrode. The main drawback of the nickel-iron electrodes - an increased tendency to hot cracking.
Get in the weld metal and weld metal can be cast iron, using special welding materials, which provide a doping electrode surface. Examples of such materials can serve as electrodes, which rod is made of low carbon wire, such as stamps, or CB-08 CB-08A in accordance with GOST 2246-70, and the dopant coating contains a sufficient number of elements grafitizatorov - carbon and silicon. The most characteristic mark EMCHS electrodes, the core of which consists of a low-carbon electrode wire and the coating of three layers:
1st layer
Graphite - 50% Silikomagny - 41% Hematite - 6% Aluminum (powder) - 1.5% Bentonite - 1.5%
2nd layer:
Marble - 50% of fluorspar - Bentonite 47.5% - 2.5%
Third layer
Graphite - 100%
The electrodes are made by sequential deposition coating, zameshennoy liquid glass, the thickness of each layer should provide the relative weight of 1st layer of 25 - 30% of 2 - and third - 10-15%. As can be seen from the above coating composition, the 1st layer is the alloying, 2nd slag and gaseous, 3rd - gas protection. Graphite and silikomagny belonging to the 1st layer are grafitizatorami, and magnesium, to some extent contributes to spheroidization of graphite, hematite, and aluminum, engaging in interaction, contribute to some reduction in the rate of cooling at the eutectic temperature, thereby obtaining the structure in the weld cast iron.
The application of these electrodes for welding of cast iron products with a relatively small thickness of the welded metal (up to 8 - 10 mm) allows to obtain high quality welds without preheating of the product; at large thicknesses should be used for semi welding. And cold welding of cast iron for semi automatic, semiautomatic and mainly use a special flux cored wires to ensure getting in the seam of gray cast iron. For cold-welding products with relatively small wall thickness (in place of welding) wire is recommended brands HRE-1, the welding-wire for semi CFR-2.
Mechanized welding flux cored wire produces weld metal and weld metal, similar in composition and structure of welded cast iron. When tea leaves large defects in iron castings, which is necessary to fix a large amount of metal afloat, as well as in the manufacture of large bulky items from high-strength cast iron with nodular graphite can be used electroslag welding plate electrodes, representing a cast iron plate with the contents of the corresponding elements grafitizatorov ( carbon and silicon) is equal to the last content in the electrode rods grades A and B, and 0,04 - 0,08% Mg.
In electroslag welding of cast iron used fluoride and non-oxidative desulfurizing flux. Slow cooling of the weld metal and heat affected zone, which is characteristic for electroslag welding produces welds with no bleached and hardened areas, cracks, pores and other defects. Electroslag welding provides a satisfactory mechanical properties of welded joints of cast iron and its good workability.
In addition to the total heat applied during welding for semi variety of ways, in some cases, when the rigidity of the product is relatively small, we can restrict ourselves to local heating to the desired temperature. During the welding process is necessary to pay attention to the fact that the product is not in the weld cooled below the set temperature heating.
Cold welding electrodes, cast iron, provides in low-carbon steel weld metal
If you run surfacing on cast iron electrodes designed for welding of carbon or low alloy structural steels, the 1-m layer, even with a relatively small percentage of participation of the base metal will high-carbon steel, which is at cooling rates that occur in welding without preheating the product, acquires sharp hardening. Therefore, the metal 1 layer will have a high hardness, low deformation capacity and will be prone to the formation of cold cracks and porosity. In the 2nd layer, of course, the share of iron is reduced, but the carbon content in it will be still at a high level, which will also lead to hardening and eventual cracking. Subsequent layers of the share of iron to be insignificant, and the weld metal will have a certain level of plasticity.
In connection with the foregoing, such steel electrodes can be used only for decorative welding of the small size of defects, if the weld is not subject to requirements to ensure the strength, density and workability of the cutting tool. In order to reduce the stake of the base metal in the weld and heat affected zone sizes, including the areas of bleaching and quenching, small diameter electrodes are used (for the 1st layer of 3 mm, for the 2nd and subsequent 3-4 mm) at low currents [Isv = (20-25) de, without overheating the base metal.
First performed facing the 1st layer. Welding is performed in short segments, ridges small sections [F = (6-8) de] randomly at intervals to cool the weld and heat affected zone to a temperature of 50-60 ° C. In a second layer applied to the 2nd transverse ridges, then 3 - First, after the third layer can be applied to multiple modes of higher energy per unit length, but also with interruptions to the heating zone was a small iron. To reduce the stresses are useful in forging middle-class.
When welding low-carbon iron electrodes the most general weak spot weld - the weld zone at the fusion boundary. The fragility of this area and the presence of cracks in it often leads to peeling of the seam of the base metal. To increase the strength of the welded joint, when it is not imposed on other requirements (such as repairing frames, frames, brackets and other load-bearing elements of thick-walled structures), used steel studs, which are partially unload the weakest part of the weld - a line of fusion.
Studs are threaded, they vvertyvayut the body part to be welded. Size of studs are usually dependent on the thickness of the workpiece. Practice, the following recommendations: diameter 0.3-0.4 stud thickness of parts, but not exceeding 12 mm, depth 1.5 diameter rods vvertyvaniya them, but no more than half the thickness of the workpiece, the height of the protruding part of 0,75-1,2 diameter studs. Studs are placed in a checkerboard pattern on the beveled edges of the parts in a row on the surface of the part on each side of the junction, the distance between them must be equal to 6.4 diameters of the pins.
Welding is performed in the following order. First scald each pin and the surface of the veneer edges electrodes 3 mm in diameter at low currents. Then, on the edge of the first hairpin coated bead and fill in a breaker, as in the previous case. To reduce the carbon content in the weld metal invited to perform welding on a layer of flux containing 30% iron scale (eg, borax 50%, 20% caustic soda, iron dross 30%). Carbon entering the weld pool, in the high part of it is actively oxidized and removed from it in the form of carbon monoxide, are not soluble in the metal. As a result, the concentration of carbon at the time of solidification of the weld pool is reduced. Hardness of weld metal decreases, the deformation capacity increases.
However, for more complete burning of the effect of carbon is necessary to use welding regimes, characterized by relatively high energy per unit length, which, however, affects the heat-affected zone: it formed a significant-sized areas of bleaching and quenching, leading to the formation of cracks. When welding cast iron with a fairly high content of elements grafitizatorov with a small wall thickness of welded parts can get positive results.
More successful was the other way. In the weld metal is introduced strong karbidoobrazovatel - vanadium. In this case, the carbides are formed mainly of the element does not dissolve in iron and having a non-solid form of fine particles. Metal base in this case is decarburized and enough plastic. An example is the mark electrodes TSCH-4 with a rod of low carbon wire marks, or CB-08 CB-08A and cover the following composition: 12% of marble, fluorspar 16%, 66% ferrovanadium, ferrosilicon 4% and 2% potash, liquid glass 30 % by weight of dry mixture. The metal deposited by these electrodes have the following composition: 0.15% C, up to 0,6% Si; 0,5% Mn; 8,5-10,5% V; sulfur and phosphorus to 0.04% each. These electrodes first veneer edge at low currents [Isv = (20-25) de]. Welding is performed by parallel ridges with overlapping each previous half its width. After a 2-layer current strength increased by 15-20%, a breaker completely filled electrodes UONI-13/45.
Scope of the electrodes - Welding of damaged parts and welding defects in castings from gray and ductile iron. If necessary, you can also weld connections of gray and ductile cast iron to steel. Welds made these electrodes have satisfactory workability, density and relatively high strength. By ways of ensuring the receipt of the weld metal of low carbon steel may also include mechanized welding short sections of the electrode wire Sv-08GS marks, or St-08G2S diameter of 0,8-1 mm in carbon dioxide. Welding current of 50-75 A, arc voltage 18-21 V, welding speed 10-12 m / h
See also:
Welding of Cast Iron
Composition and Properties of Iron
Marking of Iron
Basic Information on Weldability and Technological Advice
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
The Technological Process of Hot Welding
Cold Welding of Cast Iron with Simple Electrodes
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color
1:16 AM
The Technological Process of Hot Welding
technology process of welding cast iron. The choice of welding
The technological process of hot welding consists of the following: I - Preparation for welding products; II - pre-heating parts; III - Welding; IV - subsequent cooling.
Preparation for welding depends on the type of the corrected defect. However, in all cases, the preparation of the defective site is thoroughly cleaned of dirt and cutting to form cavities that provide access to manipulate the electrode and the arc is struck. To prevent leakage of flowable metal weld pool, and in some cases to make the weld metal, the corresponding form, weld position is formed. Forming perform three depending on the size and location correct flaws with the graphite plates, held together forming a mass consisting of quartz sand, zameshennogo liquid glass, or other molding materials, as well as in flasks molding materials used in the manufacture of Lisino.
After forming the needed drying forms a gradual increase in temperature from 60 to 120 ° C, then spend a further heating of welding at a speed of 120-150 ° per hour v.pechah, furnaces or temporary heating devices. Slow cooling after welding is achieved by insulating layer harboring products (sheets of asbestos and backfilling with sand, slag or other) or by cooling with the furnace, furnace. Methods of heating and heating devices are used depending on the nature of production (elimination of casting defects, repair welding, etc.). For example, in mass production in the foundry of automobile and tractor plants should be used conveyor furnace for maintenance work easy heating in muffle furnaces or furnaces with an open hood, and for one-time repair of large products manufactured temporary heating devices of refractory bricks, including the furnace -holes in the earthen floor of the shop. Welding using a consumable electrode and a rod of iron grades A or B.
The composition of coatings deposited on the alloy rods with a diameter of 5-20 mm, are stabilizing and alloying materials. As the last typically use graphite, silicon carbide, ferrosilicon, calcium silicon, and other silikomagny containing elements - grafitizatory. Hot welding of cast iron can perform at high current (Isv = (60 - 100) de) without interruption until the end of welding defects, with larger amounts of brew defect two welders working alternately. Hot welding electrode to ensure good contact with the iron electrode and a shield to protect the welder's hands from thermal burns.
Hot welding of cast iron, you can use a carbon arc welding electrode. If possible, maneuvering the thermal effects on the base metal welding of carbon electrode is intermediate between gas welding and welding consumable electrode. Welded with direct current straight polarity carbon electrodes with a diameter of 8-20 mm. The diameter of the electrode and the power of the welding current is selected depending on the thickness of base metal as a filler rods are used. For transfer of refractory oxides in the low-melting compounds are used in the flux of boron-based, mostly technical anhydrous (calcined) borax.
Hot welding of cast iron by hand, especially bulky items - hard work. A very innovative way to facilitate labor and increase productivity - mechanized welding flux cored wire. The composition of such components of the charge is introduced, which allow to obtain the composition of the weld metal, which is cast iron.
Hot welding of cast iron produces weld joints, weld metal equivalent (in mechanical properties, density, workability, etc.), but this is time consuming and expensive process. At the same time, in some cases virtually welded joints of cast iron is not imposed such requirements. Often, for example, it is sufficient to provide only the strength balance or just a good workability and density of the welds. With the help of various metallurgical and technological means you can get welded joints of cast iron with certain properties when welding with low or no heating without preheating (ie, using for semi or cold welding).
See also:
Welding of Cast Iron
Composition and Properties of Iron
Marking of Iron
Basic Information on Weldability and Technological Advice
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
The Technological Process of Hot Welding
Cold Welding of Cast Iron with Simple Electrodes
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color
The technological process of hot welding consists of the following: I - Preparation for welding products; II - pre-heating parts; III - Welding; IV - subsequent cooling.
Preparation for welding depends on the type of the corrected defect. However, in all cases, the preparation of the defective site is thoroughly cleaned of dirt and cutting to form cavities that provide access to manipulate the electrode and the arc is struck. To prevent leakage of flowable metal weld pool, and in some cases to make the weld metal, the corresponding form, weld position is formed. Forming perform three depending on the size and location correct flaws with the graphite plates, held together forming a mass consisting of quartz sand, zameshennogo liquid glass, or other molding materials, as well as in flasks molding materials used in the manufacture of Lisino.
After forming the needed drying forms a gradual increase in temperature from 60 to 120 ° C, then spend a further heating of welding at a speed of 120-150 ° per hour v.pechah, furnaces or temporary heating devices. Slow cooling after welding is achieved by insulating layer harboring products (sheets of asbestos and backfilling with sand, slag or other) or by cooling with the furnace, furnace. Methods of heating and heating devices are used depending on the nature of production (elimination of casting defects, repair welding, etc.). For example, in mass production in the foundry of automobile and tractor plants should be used conveyor furnace for maintenance work easy heating in muffle furnaces or furnaces with an open hood, and for one-time repair of large products manufactured temporary heating devices of refractory bricks, including the furnace -holes in the earthen floor of the shop. Welding using a consumable electrode and a rod of iron grades A or B.
The composition of coatings deposited on the alloy rods with a diameter of 5-20 mm, are stabilizing and alloying materials. As the last typically use graphite, silicon carbide, ferrosilicon, calcium silicon, and other silikomagny containing elements - grafitizatory. Hot welding of cast iron can perform at high current (Isv = (60 - 100) de) without interruption until the end of welding defects, with larger amounts of brew defect two welders working alternately. Hot welding electrode to ensure good contact with the iron electrode and a shield to protect the welder's hands from thermal burns.
Hot welding of cast iron, you can use a carbon arc welding electrode. If possible, maneuvering the thermal effects on the base metal welding of carbon electrode is intermediate between gas welding and welding consumable electrode. Welded with direct current straight polarity carbon electrodes with a diameter of 8-20 mm. The diameter of the electrode and the power of the welding current is selected depending on the thickness of base metal as a filler rods are used. For transfer of refractory oxides in the low-melting compounds are used in the flux of boron-based, mostly technical anhydrous (calcined) borax.
Hot welding of cast iron by hand, especially bulky items - hard work. A very innovative way to facilitate labor and increase productivity - mechanized welding flux cored wire. The composition of such components of the charge is introduced, which allow to obtain the composition of the weld metal, which is cast iron.
Hot welding of cast iron produces weld joints, weld metal equivalent (in mechanical properties, density, workability, etc.), but this is time consuming and expensive process. At the same time, in some cases virtually welded joints of cast iron is not imposed such requirements. Often, for example, it is sufficient to provide only the strength balance or just a good workability and density of the welds. With the help of various metallurgical and technological means you can get welded joints of cast iron with certain properties when welding with low or no heating without preheating (ie, using for semi or cold welding).
See also:
Welding of Cast Iron
Composition and Properties of Iron
Marking of Iron
Basic Information on Weldability and Technological Advice
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
The Technological Process of Hot Welding
Cold Welding of Cast Iron with Simple Electrodes
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color
1:13 AM
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
high rate of cooling after welding is observed
Effect of cooling rate on the structure of the weld metal and heat affected zone.
In the case of low cooling rates in the area and pig-iron weld heat-affected zone can be ensured the preservation of gray cast iron structure with a certain part of it.
At high cooling rate in almost any part of iron in the weld and the HAZ region 2 will take place whitening. Welding cast iron is heated. (300-400 ° C) reduces the rate of cooling. At this temperature, the heat in the weld and the HAZ region 2, depending on the number of grafitizatorov can be obtained either white or gray cast iron.
At high heating (600-650 ° C) cooling rate at the eutectic temperature is very low, bleaching is not happening. Slowing down the cooling leads to the disintegration of austenite to ferrite or pearlite formation ferrite-metal base.
Thus, the most effective means to prevent bleaching of the weld metal and heat affected zone of high land, as well as a sharp hardening of HAZ in the area - a high pre-heated cast iron or collateral to a temperature of 600-650 ° C. The welding is called with the heated hot welding cast iron. High heating and cooling also contribute to the slow elimination of cracks and voids due to increase in the lifetime of the bath and the degassing of the best, and to reduce the temperature gradient, thermal stresses.
Welding is heated to temperatures of 300-400 ° C called for semi, and without pre-heating - cold welding of cast iron. If for semi and cold welding of cast iron is widely used metallurgical and technological means of exposure to the metal in order to improve the quality of welded joints. Among them are:
- Weld metal alloying elements - so that at a given cooling rate obtained in the joint structure of gray cast iron;
- Weld metal alloying elements such as would allow for the seam in the pearlite-ferritic structure characteristic of low-carbon steel, by binding to excess carbon in the carbides are more stable than cementite, and uniformly distributed in the metal;
introduction of oxygen-containing components of welding consumables in order to maximize carbon oxidation (burning it) and get in the weld metal of low carbon steel;
application of welding materials, providing in the weld metal to obtain the various non-ferrous metals: copper-nickel, copper and iron, iron-nickel, etc., with high plasticity and having a melting point close to the melting point of iron.
Hot welding of cast iron
The most radical way to combat the formation of bleached and hardened parts of the weld and heat affected zone and the formation of pores and cracks is heated to a temperature of product 600-650 ° C and slow cooling after welding it.
See also:
Welding of Cast Iron
Composition and Properties of Iron
Marking of Iron
Basic Information on Weldability and Technological Advice
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
The Technological Process of Hot Welding
Cold Welding of Cast Iron with Simple Electrodes
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color
Effect of cooling rate on the structure of the weld metal and heat affected zone.
In the case of low cooling rates in the area and pig-iron weld heat-affected zone can be ensured the preservation of gray cast iron structure with a certain part of it.
At high cooling rate in almost any part of iron in the weld and the HAZ region 2 will take place whitening. Welding cast iron is heated. (300-400 ° C) reduces the rate of cooling. At this temperature, the heat in the weld and the HAZ region 2, depending on the number of grafitizatorov can be obtained either white or gray cast iron.
At high heating (600-650 ° C) cooling rate at the eutectic temperature is very low, bleaching is not happening. Slowing down the cooling leads to the disintegration of austenite to ferrite or pearlite formation ferrite-metal base.
Thus, the most effective means to prevent bleaching of the weld metal and heat affected zone of high land, as well as a sharp hardening of HAZ in the area - a high pre-heated cast iron or collateral to a temperature of 600-650 ° C. The welding is called with the heated hot welding cast iron. High heating and cooling also contribute to the slow elimination of cracks and voids due to increase in the lifetime of the bath and the degassing of the best, and to reduce the temperature gradient, thermal stresses.
Welding is heated to temperatures of 300-400 ° C called for semi, and without pre-heating - cold welding of cast iron. If for semi and cold welding of cast iron is widely used metallurgical and technological means of exposure to the metal in order to improve the quality of welded joints. Among them are:
- Weld metal alloying elements - so that at a given cooling rate obtained in the joint structure of gray cast iron;
- Weld metal alloying elements such as would allow for the seam in the pearlite-ferritic structure characteristic of low-carbon steel, by binding to excess carbon in the carbides are more stable than cementite, and uniformly distributed in the metal;
introduction of oxygen-containing components of welding consumables in order to maximize carbon oxidation (burning it) and get in the weld metal of low carbon steel;
application of welding materials, providing in the weld metal to obtain the various non-ferrous metals: copper-nickel, copper and iron, iron-nickel, etc., with high plasticity and having a melting point close to the melting point of iron.
Hot welding of cast iron
The most radical way to combat the formation of bleached and hardened parts of the weld and heat affected zone and the formation of pores and cracks is heated to a temperature of product 600-650 ° C and slow cooling after welding it.
See also:
Welding of Cast Iron
Composition and Properties of Iron
Marking of Iron
Basic Information on Weldability and Technological Advice
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
The Technological Process of Hot Welding
Cold Welding of Cast Iron with Simple Electrodes
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color
1:10 AM
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
gives a graphical scheme to see the thermal effect on the weld, the temperature distribution
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
To assess the influence of the thermal cycle of welding on the structure and properties of different zones of welded joints consider the state diagram of the pseudobinary Fe - C - Si, linking it with the distribution of temperature in the weld and heat affected zone (Fig.). The seam is a metal was completely melted. Depending on the cooling rate structure it will be a white or gray cast iron with different amounts of structural and free carbon.
Section 1 (incomplete fusion) is characterized by the presence in it of both liquid and solid phases. The solid phase is austenite with maximum carbon content (up to 2.14%). After rapid cooling of the liquid phase forms a white iron in austenite areas, the formation of martensite.
Section 2 is limited to the eutectic and eutectoid temperatures. Its structure is largely dependent on the initial structure of cast iron and can consist of austenite and cementite or austenite and graphite (depending on the cooling rate and composition of pig iron) With the rapid cooling of the metal base structure becomes hardened.
Section 3 (incomplete recrystallization) due to rapid heating and short duration of stay of the metal in the temperature range of ferrite - the basis of the structural components of cast iron at room temperature - do not have time to completely dissolve. After cooling in this area may experience some grain refinement. With the rapid cooling of the metal base may become partially hardened.
Section 4 is the part of the heat-affected zone, which was heated to 500 ° C to a temperature of c 1 . At long stay in this temperature range may occur due to partial graphitization of the cementite decomposition and spheroidization of carbides. However, in the heat of welding in the area marked structural changes are observed.
Section 5 is characterized by the initial structure of welded iron.
See also:
Welding of Cast Iron
Composition and Properties of Iron
Marking of Iron
Basic Information on Weldability and Technological Advice
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
The Technological Process of Hot Welding
Cold Welding of Cast Iron with Simple Electrodes
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
To assess the influence of the thermal cycle of welding on the structure and properties of different zones of welded joints consider the state diagram of the pseudobinary Fe - C - Si, linking it with the distribution of temperature in the weld and heat affected zone (Fig.). The seam is a metal was completely melted. Depending on the cooling rate structure it will be a white or gray cast iron with different amounts of structural and free carbon.
Section 2 is limited to the eutectic and eutectoid temperatures. Its structure is largely dependent on the initial structure of cast iron and can consist of austenite and cementite or austenite and graphite (depending on the cooling rate and composition of pig iron) With the rapid cooling of the metal base structure becomes hardened.
Section 3 (incomplete recrystallization) due to rapid heating and short duration of stay of the metal in the temperature range of ferrite - the basis of the structural components of cast iron at room temperature - do not have time to completely dissolve. After cooling in this area may experience some grain refinement. With the rapid cooling of the metal base may become partially hardened.
Section 4 is the part of the heat-affected zone, which was heated to 500 ° C to a temperature of c 1 . At long stay in this temperature range may occur due to partial graphitization of the cementite decomposition and spheroidization of carbides. However, in the heat of welding in the area marked structural changes are observed.
Section 5 is characterized by the initial structure of welded iron.
See also:
Welding of Cast Iron
Composition and Properties of Iron
Marking of Iron
Basic Information on Weldability and Technological Advice
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
The Technological Process of Hot Welding
Cold Welding of Cast Iron with Simple Electrodes
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color
12:40 AM
Basic Information on Weldability and Technological Advice
introduction of technological recommendations for welding of cast iron
Basic information on weldability and technological advice.
Welding heating and subsequent cooling so alter the structure and properties of iron in the zone of fusion and heat affected zone, which is a defect-free welds with the required level of properties is very difficult. In this regard, iron refers to materials having a bad technology weldability. However, welding of cast iron has a very wide distribution as a means to fix the marriage of cast iron castings, cast iron repair products and sometimes in the manufacture of structures. High-grade weld should at least have the necessary level of mechanical properties, density (impermeability) and satisfactory workability (handled cutting tool). Depending on the conditions of the compound may be brought to him and other requirements (eg, one-color, heat resistance, etc.).
Reasons for the difficulty in obtaining high-quality welds, the following.
1. Cooling rate of weld metal and heat affected zone corresponding to the thermal cycle of welding, lead to bleaching of iron, ie, the appearance of areas with secretions cementite one form or another in varying amounts. The high hardness of bleached areas of practice makes it impossible to handle cast iron cutting tool.
2. Due to the uneven heating of the local metal welding stresses arise, which are due to the very low ductility of cast iron lead to the formation of cracks in the weld and heat affected zone. The presence of bleached areas with high density (7,4-7,7 g/cm3) than gray cast iron (6,9-7,3 g/cm3), creates additional structural stresses that contribute to cracking.
3. Intensive gas evolution from the weld pool, which continues at the stage of crystallization may lead to the formation of pores in the weld metal.
4. Increased fluidity of cast iron makes it difficult to hold the molten metal from leaking and forming a seam.
5. The presence of silicon, and sometimes other elements in the metal promotes the formation of the weld pool on the surface of refractory oxides, leading to the formation of fusions.
See also:
Welding of Cast Iron
Composition and Properties of Iron
Marking of Iron
Basic Information on Weldability and Technological Advice
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
The Technological Process of Hot Welding
Cold Welding of Cast Iron with Simple Electrodes
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color
Basic information on weldability and technological advice.
Welding heating and subsequent cooling so alter the structure and properties of iron in the zone of fusion and heat affected zone, which is a defect-free welds with the required level of properties is very difficult. In this regard, iron refers to materials having a bad technology weldability. However, welding of cast iron has a very wide distribution as a means to fix the marriage of cast iron castings, cast iron repair products and sometimes in the manufacture of structures. High-grade weld should at least have the necessary level of mechanical properties, density (impermeability) and satisfactory workability (handled cutting tool). Depending on the conditions of the compound may be brought to him and other requirements (eg, one-color, heat resistance, etc.).
Reasons for the difficulty in obtaining high-quality welds, the following.
1. Cooling rate of weld metal and heat affected zone corresponding to the thermal cycle of welding, lead to bleaching of iron, ie, the appearance of areas with secretions cementite one form or another in varying amounts. The high hardness of bleached areas of practice makes it impossible to handle cast iron cutting tool.
2. Due to the uneven heating of the local metal welding stresses arise, which are due to the very low ductility of cast iron lead to the formation of cracks in the weld and heat affected zone. The presence of bleached areas with high density (7,4-7,7 g/cm3) than gray cast iron (6,9-7,3 g/cm3), creates additional structural stresses that contribute to cracking.
3. Intensive gas evolution from the weld pool, which continues at the stage of crystallization may lead to the formation of pores in the weld metal.
4. Increased fluidity of cast iron makes it difficult to hold the molten metal from leaking and forming a seam.
5. The presence of silicon, and sometimes other elements in the metal promotes the formation of the weld pool on the surface of refractory oxides, leading to the formation of fusions.
See also:
Welding of Cast Iron
Composition and Properties of Iron
Marking of Iron
Basic Information on Weldability and Technological Advice
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
The Technological Process of Hot Welding
Cold Welding of Cast Iron with Simple Electrodes
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color
12:38 AM
Marking of Iron
Iron is marked by the letters MF and ...
Marking of Iron
Iron is marked with the letters and numbers, midrange, the first of which characterizes the strength of this brand of cast iron in tension, the second - at a bend (kg / mm 2 ). The most widely used brands of cast iron: SCH12-28; SCH15-32-36 SCH18, SCH 21-40, 24-44 MF, MF 28-48, 32-52 MF, MF 38-60, with the top five brands are perlite- ferritic base metal, the last three - pearlite. The strength of gray cast iron of all grades in compression is much higher than the tensile strength. For example, a cast iron SCh 24-44, having a tensile strength of 24 kgf / mm 2 , the compressive strength of 85 kgf / mm 2 . To increase the strength of cast iron with graphite inclusion gives a spherical shape by the introduction of magnesium into the ladle before pouring. In this cast, and takes some flexibility. High-strength cast iron mark the letters and numbers, HF, the first of which describes the temporary resistance of cast iron in tension (kgf/mm2), the second - elongation (%). For example, HF or HF 60-2 40-10.
Ductile iron mark the letters and numbers, CN, marking the time when the resistance tension (kgf/mm2) and elongation (%). Examples of brands of cast iron can serve as a CN 38-8; CN 35-10, CN 37-12, CN 06.30 with ferritic steel base and the CN 45-6, 50-4, and CN CN 60-3 having a ferrite-pearlite base .
In this part of the structure of iron is largely dependent on the cooling rate.
In this part of iron, such as the constancy of the total content of carbon and silicon, as well as other elements in its composition, can be hardened, and the pearlite-ferritic iron.
See also:
Welding of Cast Iron
Composition and Properties of Iron
Marking of Iron
Basic Information on Weldability and Technological Advice
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
The Technological Process of Hot Welding
Cold Welding of Cast Iron with Simple Electrodes
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color
Marking of Iron
Iron is marked with the letters and numbers, midrange, the first of which characterizes the strength of this brand of cast iron in tension, the second - at a bend (kg / mm 2 ). The most widely used brands of cast iron: SCH12-28; SCH15-32-36 SCH18, SCH 21-40, 24-44 MF, MF 28-48, 32-52 MF, MF 38-60, with the top five brands are perlite- ferritic base metal, the last three - pearlite. The strength of gray cast iron of all grades in compression is much higher than the tensile strength. For example, a cast iron SCh 24-44, having a tensile strength of 24 kgf / mm 2 , the compressive strength of 85 kgf / mm 2 . To increase the strength of cast iron with graphite inclusion gives a spherical shape by the introduction of magnesium into the ladle before pouring. In this cast, and takes some flexibility. High-strength cast iron mark the letters and numbers, HF, the first of which describes the temporary resistance of cast iron in tension (kgf/mm2), the second - elongation (%). For example, HF or HF 60-2 40-10.
Ductile iron mark the letters and numbers, CN, marking the time when the resistance tension (kgf/mm2) and elongation (%). Examples of brands of cast iron can serve as a CN 38-8; CN 35-10, CN 37-12, CN 06.30 with ferritic steel base and the CN 45-6, 50-4, and CN CN 60-3 having a ferrite-pearlite base .
In this part of the structure of iron is largely dependent on the cooling rate.
In this part of iron, such as the constancy of the total content of carbon and silicon, as well as other elements in its composition, can be hardened, and the pearlite-ferritic iron.
See also:
Welding of Cast Iron
Composition and Properties of Iron
Marking of Iron
Basic Information on Weldability and Technological Advice
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
The Technological Process of Hot Welding
Cold Welding of Cast Iron with Simple Electrodes
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color
12:34 AM
Composition and Properties of Iron
examine the properties of cast iron, which determine the specificity
Composition and properties
For cast irons are alloys of iron with carbon content exceeding 2.14%, in these alloys is usually present as silicon, and some amount of manganese, sulfur and phosphorus, and sometimes other elements introduced as alloying additives to impart specific properties of cast iron. These alloying elements include nickel, chromium, magnesium, etc.
Depending on the structure of cast irons are divided into white and gray. In white cast iron all the carbon is connected to the chemical compound iron carbide Fe 3 C - cementite. In gray cast iron is a significant part of the carbon in the structure-free state in the form of graphite. If the gray cast iron well to machining, White has a very high hardness and cutting tool can not be processed. Therefore, the white cast irons are used for the manufacture of products is extremely rare, they are used mainly as intermediate for the so-called malleable cast iron. Getting a white or gray cast iron depends on its composition and cooling rate.
Depending on the structure of cast irons are classified as high-strength (nodular) and malleable. According to the degree of doping irons are divided into simple, low-alloy (up to 2.5% alloying elements), srednelegirovannye (2.5 - 10% alloying elements) and high (over 10% alloying elements). The most widely used are simple and low-alloyed gray cast iron.
Cast iron became widespread as a structural material in engineering, metallurgy and other industries due to a number of advantages over other materials, such as in the first place should be mentioned are: low cost, good casting properties. Products made from it have a sufficiently high strength and wear resistance due to friction at work and are less than steel sensitivity to stress concentrators. Along with these advantages the product made from gray cast iron is well handled by the cutting tool. This, together with good casting properties to evaluate iron as a highly technological material.
The main process of forming the structure of cast iron - the process of graphitization (emphasis in structural carbon-free form), since it determines not only the number, shape and distribution of graphite in the structure, but also a metal base (matrix) of iron. Depending on the degree of graphitization of the matrix can be pearlite-cementite (n-f-C), pearlite (P), pearlitic-ferritic (P B-F) and ferritic (F). Pearlite eutectoid cementite is called, the rest of the cement - the structural-free. Some of the elements introduced in the cast (in order of potency: C, Si, Ni, Co, Cu), promote graphitization, while others - prevent (S, V, Cr, Sn, Mo, Mn). The greatest effect is grafitiziruyuschee carbon and silicon, the smallest - cobalt and copper.
The most severely retard the process of graphitization (have a bleaching action), sulfur, vanadium, tin. Therefore, in gray cast irons always contain a significant amount of silicon.
See also:
Welding of Cast Iron
Composition and Properties of Iron
Marking of Iron
Basic Information on Weldability and Technological Advice
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
The Technological Process of Hot Welding
Cold Welding of Cast Iron with Simple Electrodes
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color
Composition and properties
For cast irons are alloys of iron with carbon content exceeding 2.14%, in these alloys is usually present as silicon, and some amount of manganese, sulfur and phosphorus, and sometimes other elements introduced as alloying additives to impart specific properties of cast iron. These alloying elements include nickel, chromium, magnesium, etc.
Depending on the structure of cast irons are divided into white and gray. In white cast iron all the carbon is connected to the chemical compound iron carbide Fe 3 C - cementite. In gray cast iron is a significant part of the carbon in the structure-free state in the form of graphite. If the gray cast iron well to machining, White has a very high hardness and cutting tool can not be processed. Therefore, the white cast irons are used for the manufacture of products is extremely rare, they are used mainly as intermediate for the so-called malleable cast iron. Getting a white or gray cast iron depends on its composition and cooling rate.
Depending on the structure of cast irons are classified as high-strength (nodular) and malleable. According to the degree of doping irons are divided into simple, low-alloy (up to 2.5% alloying elements), srednelegirovannye (2.5 - 10% alloying elements) and high (over 10% alloying elements). The most widely used are simple and low-alloyed gray cast iron.
Cast iron became widespread as a structural material in engineering, metallurgy and other industries due to a number of advantages over other materials, such as in the first place should be mentioned are: low cost, good casting properties. Products made from it have a sufficiently high strength and wear resistance due to friction at work and are less than steel sensitivity to stress concentrators. Along with these advantages the product made from gray cast iron is well handled by the cutting tool. This, together with good casting properties to evaluate iron as a highly technological material.
The main process of forming the structure of cast iron - the process of graphitization (emphasis in structural carbon-free form), since it determines not only the number, shape and distribution of graphite in the structure, but also a metal base (matrix) of iron. Depending on the degree of graphitization of the matrix can be pearlite-cementite (n-f-C), pearlite (P), pearlitic-ferritic (P B-F) and ferritic (F). Pearlite eutectoid cementite is called, the rest of the cement - the structural-free. Some of the elements introduced in the cast (in order of potency: C, Si, Ni, Co, Cu), promote graphitization, while others - prevent (S, V, Cr, Sn, Mo, Mn). The greatest effect is grafitiziruyuschee carbon and silicon, the smallest - cobalt and copper.
The most severely retard the process of graphitization (have a bleaching action), sulfur, vanadium, tin. Therefore, in gray cast irons always contain a significant amount of silicon.
See also:
Welding of Cast Iron
Composition and Properties of Iron
Marking of Iron
Basic Information on Weldability and Technological Advice
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
The Technological Process of Hot Welding
Cold Welding of Cast Iron with Simple Electrodes
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color
2:31 AM
Welding of Cast Iron
Cast iron is an alloy of iron with carbon (more than 2,11-2,14%), which usually also contains silicon (3%), manganese (1%), sulfur, phosphorus, and may contain alloying elements - chromium, nickel , vanadium, aluminum, magnesium, iron, etc., without alloying or heat treatment - rather brittle material with low strength, hardness and ductility.
Carbon may be present in the iron in the form of cementite Fe 3 C and graphite. By the number of cementite and the form of graphite irons are divided into the following types:
In gray iron the entire carbon or most of it is present as graphite. Color break - gray. Grey cast iron due to the high casting properties is used as base material for casting. In contrast to the white iron lends itself well to metal processing.
Ductile cast iron is obtained by casting and subsequent heat treatment of white cast iron with the formation of flaky graphite. Ductile iron is mainly used in the manufacture of automobiles, agricultural machinery and tractors.
Halfway (bleached) iron - a cast-iron, in which carbon is present in the form of graphite, and in the form of cementite. Used as a friction material for use in conditions of dry friction for increased wear resistance of parts.
In ductile iron containing spheroidal graphite formed during the crystallization process. Typically used for the production of critical parts in machinery for the manufacture of high-water pipes, oil and gas pipelines.
Weldability of cast iron
Cast iron has poor weldability processing:
Welding of cast iron
Welding of cast iron can be carried out or covered with carbon electrodes, cored wires, equipment for gas welding and other methods.
There are three main technological areas of welding cast iron:
When welding cast iron for semi improved graphitization of the metal is achieved by the introduction of the welding zone grafitiziruyuschih substances (silicon, titanium, aluminum) and preheat the product with a lower temperature than the hot welding.
Cold welding of cast iron is performed in cases where the iron in the weld metal is not provided, and can be applied in some cases, when the weld metal is required to obtain iron - using grafitiziruyuschih substances at low or medium-sized defects in the non-through defects or defects of the small extent of cross-cutting and depth.
Arc welding to produce pig iron in the weld metal
The process of hot-iron welding is carried out in several stages:
At the end of molding requires dry form, with a gradual increase in temperature from 60 to 120 ° C. Further details of the shape of the heating is performed at 120-150 ° C in a furnace, forge, a special pit or other heating device. After welding, for slow cooling of the product is covered by a layer of thermal insulation (asbestos sheets and backfill of dry sand, slag, charcoal, etc.) or cooled with the heating device. Large parts can cool down from 3 to 5 days.
For manual arc welding hot iron melting electrodes are applied with rods of iron grades A or B, as well as carbon electrodes can be used. Hot welding is done continuously at high currents up to the end of the welding defect. If significant amounts of welding performed alternating welder. Cover the cast bar has a diameter of 5-20 mm alloying (silicon carbide, graphite, calcium silicon, ferrosilicon, etc.) and stabilizing materials. Electrode holder shall be provided with a shield to protect the welder's hands from the heat radiation. Welding of carbon electrodes (diameter 8-20 mm) is performed on a direct current straight polarity.
TABLE. The composition of iron rods for welding and hot for semi
TABLE. Modes of arc welding of cast iron carbon electrode
Hot welding of cast iron allows you to weld cast iron, almost no different from the basic metal products (density, mechanical properties, machinability, etc.). However, it has some drawbacks:
To prevent bleaching of iron in the weld metal can be introduced by a large number of grafitizatorov and alloying elements. For example, welding electrodes brand EMCH have iron rod with a high silicon content (up to 5.2%) and two-layer coating, which is the first layer of alloying, and the second is designed to provide protection of the gas and slag.
TABLE. The composition of electrode coatings brands EMCH
In cold welding electrodes brand EMCH products of cast iron with a wall thickness of 12 mm is possible to obtain joints and weld zone without bleached and hardened areas.
When welding electrodes brand EMCH massive products of iron to produce defect-free welds require pre-heating to T = 400 ° C depending on the hardness and thickness of cast iron products.
The electrodes of nickel pig iron can obtain welds with good machinability, but it increases the likelihood of hot cracking. Welding is carried out in several layers with a reciprocating movement of the electrode.
TABLE. The composition of the electrode rods of nickel pig iron (%)
The electrodes provide brand EMCHS doping through the coating. Their core consists of a low carbon wire, and coated with three layers: the alloying, gas and slag-forming, gas protection. When the thickness of the workpiece 8 to 10 mm for defect-free welds by means of these electrodes can be used cold welding, and for thick - hot welding.
Semi-automatic hot and cold for semi welding cast iron is performed, usually with flux cored wire PP-Anch-1, PP-Anch-2, PP-Anch-3, etc. The wires contain a set of modifying elements introduced into the charge as a ligature on the basis silicon.
TABLE. The mechanical properties of the metal iron, welded with flux cored wire
Gas welding
Gas welding cast iron is considered a reliable method of obtaining the metal seams, little different from the basic metal products. Compared with arc welding with heating and cooling in gas welding - a long and uniform, so that provided the best conditions for the graphitization of carbon and decreases the likelihood of bleached areas in the weld and heat affected zone.
Desirable to perform gas welding with preheating (general or local). Bevel the edges is one-sided (V-shaped), with an opening angle of 90 °. The edges are thoroughly cleaned of dirt, rust and oil with a brush or a sandblaster and heated gas flame.
Filler rods are usually cast iron rods following brands:
For gas welding of metal is necessary to use flux, which performs the following functions:
It is essential that the welding flame is normal or carburizing, since oxidative flame leads to a strong local burnout of silicon with the formation of grains in the weld seam of white cast iron. The metal should be well warmed up. Welding is performed in the down position quickly, and for large parts preferably two burners simultaneously. To prevent the formation of pores in the weld metal must constantly stir welding bath filler rod end, making it easier to exit the dissolved gases.
During the welding filler rod is dipped into a bath only when it warms up to temperature end of the light-red heat, as the immersion of unheated rods can cause bleached areas. Rods are removed from the weld pool as little as possible and only to cover its flux.
Allowed periodic removal of the flame kernel to the weld pool surface, but the replacement part of the flame must always cover the surface of the bath. If excessive delay in one area of the flame is burning out of carbon and silicon, which can lead to bleaching of iron.
Welding of cast iron parts of complex shape (with holes, bridges, unequal in different parts of the section) to avoid the appearance of defects caused by the uneven heating, should be performed only with the general pre-heated.
Upon completion of welding of the product cover layer of asbestos for a slow cooling.
Electroslag welding
In electroslag welding of cast iron as electrodes use a cast iron plate, and as a flux - fluoride and non-oxidative desulfurizing flux. Electroslag welding allows to obtain satisfactory properties of the joints of cast iron, hardened and bleached without the parts, pores, cracks and other defects.
See also:
welding equipment
welding wire
manual arc welding technology
semi-automatic welding
gas welding
electroslag welding
Welding of metals:
welding of cast iron
welding of aluminum
welding of titanium
 |
| cast iron parts |
- white;
- gray;
- malleable;
- half-hearted;
- ductile iron.
In gray iron the entire carbon or most of it is present as graphite. Color break - gray. Grey cast iron due to the high casting properties is used as base material for casting. In contrast to the white iron lends itself well to metal processing.
Ductile cast iron is obtained by casting and subsequent heat treatment of white cast iron with the formation of flaky graphite. Ductile iron is mainly used in the manufacture of automobiles, agricultural machinery and tractors.
Halfway (bleached) iron - a cast-iron, in which carbon is present in the form of graphite, and in the form of cementite. Used as a friction material for use in conditions of dry friction for increased wear resistance of parts.
In ductile iron containing spheroidal graphite formed during the crystallization process. Typically used for the production of critical parts in machinery for the manufacture of high-water pipes, oil and gas pipelines.
Weldability of cast iron
Cast iron has poor weldability processing:
- rapid cooling of the weld and heat affected zone leads to the bleached areas (areas with secretions of cementite with high hardness), which is extremely difficult to follow the machining of metal;
- due to the high brittleness of cast iron when it is non-uniform heating and cooling of the high probability of occurrence of cracks in the weld and heat affected zone;
- Iron is a flowable alloy, which makes it difficult to hold the molten metal flowing and makes the formation of joint;
- because of the intense emission of gas from the liquid weld pool, and continuing on the stage of crystallization in the weld can be formed pores;
- the oxidation of silicon, and sometimes other elements on the surface of the weld pool can form refractory oxides, leading to lack of penetration.
Welding of cast iron
Welding of cast iron can be carried out or covered with carbon electrodes, cored wires, equipment for gas welding and other methods.
There are three main technological areas of welding cast iron:
- welding, providing the production of pig iron in the weld metal;
- welding, providing reception in the weld metal of low carbon steel;
- welding, providing reception in the weld metal non-ferrous alloys.
- Hot welding - with pre-heating temperature 600-650 ° C;
- for semi welding - the temperature of preliminary heating up to 400-450 ° C;
- Cold welding - without preheating.
When welding cast iron for semi improved graphitization of the metal is achieved by the introduction of the welding zone grafitiziruyuschih substances (silicon, titanium, aluminum) and preheat the product with a lower temperature than the hot welding.
Cold welding of cast iron is performed in cases where the iron in the weld metal is not provided, and can be applied in some cases, when the weld metal is required to obtain iron - using grafitiziruyuschih substances at low or medium-sized defects in the non-through defects or defects of the small extent of cross-cutting and depth.
Arc welding to produce pig iron in the weld metal
The process of hot-iron welding is carried out in several stages:
- preparation of workpiece;
- preheating;
- welding;
- followed by slow cooling.
 |
| Shaping places for hot welding of cast iron |
For manual arc welding hot iron melting electrodes are applied with rods of iron grades A or B, as well as carbon electrodes can be used. Hot welding is done continuously at high currents up to the end of the welding defect. If significant amounts of welding performed alternating welder. Cover the cast bar has a diameter of 5-20 mm alloying (silicon carbide, graphite, calcium silicon, ferrosilicon, etc.) and stabilizing materials. Electrode holder shall be provided with a shield to protect the welder's hands from the heat radiation. Welding of carbon electrodes (diameter 8-20 mm) is performed on a direct current straight polarity.
TABLE. The composition of iron rods for welding and hot for semi
| Element | Grade A hot welding | Grade B for hot and for semi welding |
| Carbon | 3.0–3.5 | |
| Silicon | 3.0–3.4 | 3.5–4.0 |
| Manganese | 0.5–0.8 | |
| Phosphorus | 0.2–0.4 | 0.3–0.5 |
| Sulfur | to 0.08 | |
| Chrome | to 0.05 | |
| Nickel | to 0.3 | |
| Metal thickness (mm) | The diameter of the electrode (mm) | Current (A) |
| 6–10 | 8–10 | 280–350 |
| 10–20 | 10–12 | 300–400 |
| 20–30 | 12–16 | 350–500 |
| 30 or more | 16–18 | 350–600 |
- the complexity of the process associated with the need to mold the welding, the complexity of providing uniform heating of the product;
- duration and high cost of the process.
To prevent bleaching of iron in the weld metal can be introduced by a large number of grafitizatorov and alloying elements. For example, welding electrodes brand EMCH have iron rod with a high silicon content (up to 5.2%) and two-layer coating, which is the first layer of alloying, and the second is designed to provide protection of the gas and slag.
TABLE. The composition of electrode coatings brands EMCH
| 1st layer | 2nd layer |
| Graphite - 41% silikomagny - 40% iron slag - 14% aluminum (powder) - 5% | Marble - 50% fluorspar - 50% |
When welding electrodes brand EMCH massive products of iron to produce defect-free welds require pre-heating to T = 400 ° C depending on the hardness and thickness of cast iron products.
The electrodes of nickel pig iron can obtain welds with good machinability, but it increases the likelihood of hot cracking. Welding is carried out in several layers with a reciprocating movement of the electrode.
TABLE. The composition of the electrode rods of nickel pig iron (%)
| Cast iron | Carbon | Nickel | Silicon | Copper | Manganese | Iron |
| Ni-resist | 2,0 | 29 | 1,3 | 7,6 | 0,4 | 59,7 |
| Nikrosilal | 2,0–2,3 | 19–22 | 5,2–6,4 | – | 0,5 | 68,8–73,3 |
Semi-automatic hot and cold for semi welding cast iron is performed, usually with flux cored wire PP-Anch-1, PP-Anch-2, PP-Anch-3, etc. The wires contain a set of modifying elements introduced into the charge as a ligature on the basis silicon.
TABLE. The mechanical properties of the metal iron, welded with flux cored wire
| Mark the wire and the temperature of heating | σ B (MPa) tensile | σ B (MPa), flexural | Hardness, HB |
| Welding wire PP-Anch-1, welding without preheating | 180–220 | 400–450 | 250–300 |
| Welding wire PP-Anch-2 welding with heating at T = 350 ° C | 170–250 | 350–450 | 170–190 |
| Welding wire PP-Anch-3 Welding heated at T = 600 ° C | 280–320 | 460–520 | 180–210 |
Gas welding cast iron is considered a reliable method of obtaining the metal seams, little different from the basic metal products. Compared with arc welding with heating and cooling in gas welding - a long and uniform, so that provided the best conditions for the graphitization of carbon and decreases the likelihood of bleached areas in the weld and heat affected zone.
Desirable to perform gas welding with preheating (general or local). Bevel the edges is one-sided (V-shaped), with an opening angle of 90 °. The edges are thoroughly cleaned of dirt, rust and oil with a brush or a sandblaster and heated gas flame.
Filler rods are usually cast iron rods following brands:
- " A "(for hot gas welding of cast iron, composition see table above);
- " B "(for gas welding of cast iron with a local heating, see the composition in the table above);
- " LF-1 "(for low-temperature gas welding of thin-walled castings made of cast iron);
- " low-2 "(for low-temperature gas welding of thick-walled castings made of cast iron);
- " Warhead "and" KhCh "(to wear welding cast iron.)
For gas welding of metal is necessary to use flux, which performs the following functions:
- protects the weld pool from oxidation;
- translates refractory oxides of iron, manganese and silicon in low-melting slag;
- improves splavlyaemost creating micropitting oxidation and partial dissolution of the graphite inclusions of iron;
- increases the fluidity of the molten pool of metal and slag.
- Flux FSCH-1, used mainly for welding of large defects of - calcined borax (23%), sodium nitrate (50%), sodium carbonate (27%);
- Flux FSCH-2, used for low-temperature welding and welding of small parts made of cast iron, is different from the flux FSCH-1 additive in the composition of lithium carbonate;
- gas flux of MB-1 consists of a volatile liquid organoboron.
It is essential that the welding flame is normal or carburizing, since oxidative flame leads to a strong local burnout of silicon with the formation of grains in the weld seam of white cast iron. The metal should be well warmed up. Welding is performed in the down position quickly, and for large parts preferably two burners simultaneously. To prevent the formation of pores in the weld metal must constantly stir welding bath filler rod end, making it easier to exit the dissolved gases.
During the welding filler rod is dipped into a bath only when it warms up to temperature end of the light-red heat, as the immersion of unheated rods can cause bleached areas. Rods are removed from the weld pool as little as possible and only to cover its flux.
Allowed periodic removal of the flame kernel to the weld pool surface, but the replacement part of the flame must always cover the surface of the bath. If excessive delay in one area of the flame is burning out of carbon and silicon, which can lead to bleaching of iron.
Welding of cast iron parts of complex shape (with holes, bridges, unequal in different parts of the section) to avoid the appearance of defects caused by the uneven heating, should be performed only with the general pre-heated.
Upon completion of welding of the product cover layer of asbestos for a slow cooling.
Electroslag welding
In electroslag welding of cast iron as electrodes use a cast iron plate, and as a flux - fluoride and non-oxidative desulfurizing flux. Electroslag welding allows to obtain satisfactory properties of the joints of cast iron, hardened and bleached without the parts, pores, cracks and other defects.
See also:
welding equipment
welding wire
manual arc welding technology
semi-automatic welding
gas welding
electroslag welding
Welding of metals:
welding of cast iron
welding of aluminum
welding of titanium