Pliers for Welding
the grip for a point of contact welds
The Spot Welding Process
on the process of spot welding
The Spot Welding Process (Part 2)
on the process of spot welding part 2
Special Types of Spot Welding
how to increase the productivity of spot welding (using special-purpose machines, multi-point welding)
Spot Welding
Electric Resistance Welding
Showing posts with label pressure contact welding. Show all posts
Showing posts with label pressure contact welding. Show all posts
2:08 AM
2:00 AM
Special Types of Spot Welding
how to increase the productivity of spot welding (using special-purpose machines, multi-point welding)
Special types of spot welding
To improve performance, multi-point welding is used in which one cycle of the machine is welded by a few points. The electrodes are pressed against the product, which lies on the conductive copper lining. Current flows through the circuit electrode - a product - a copper lining - the product - the second electrode. Welded together two points. This method is called two-point one-sided welding. Multipoint machines typically have a hydraulic drive and operate on the principle of two-point one-sided welding.
Oil distributor distributes oil under high pressure in the cylinders and presses the individual electrodes to the product of two respective electrodes by applying a current to them, then the current is switched off, the electrodes are retracted, the oil is fed into the next couple of cylinders and so on, until the finished welding of the entire site. These machines can have up to 100 or more electrodes.
In some multi-point machines all at once the electrodes are pressed against the product, which provides a lower warpage, and greater accuracy of the product. The current spread between the electrodes pressed a special commutator having a very sophisticated device and comprising electrodes in pairs, carrying out the process of two-point one-sided welding. Both types of machines are only applicable in mass production, and for each part requires a rather complex manufacturing of devices with the appropriate placement of the electrodes and the hydraulic cylinders.
A few simple simultaneous welding of several points raised by means of welding or welding projections, which is a kind of spot welding. In this case, one of the workpiece or both pre vyshtampovyvayut protrusions (reliefs)
in places subject to welding. Trained lay down the details in a special welding machine that bears the name of "welding press." Welding of lugs may also be at the point of powerful machines with a straight course of the electrode and the electrode is replaced by a normal point-specific electrode for projection welding, plate-shaped solid. Simultaneously with the inclusion of current top electrode compresses the parts and compressed them to complete destruction of the projections. Thus, over the course of a machine is so spot welds, as it was stamped projections, their number can reach up to several dozen in one piece. To obtain high-quality welding requires accurate punching and a snug fit on all parts collected projections.
The method of projection welding can provide high performance. The electrodes are in good working conditions and have a great life because of their contact surface is very high and the pressure and current projections are concentrated in the welded parts.
The disadvantage of projection welding is a significant electrical power required for welding presses. The magnitude of this power for the welding of a 15-30 bulge that. Pressure on a ledge is typically 200-600 kg. A variety of projection welding is a welding rod to the ends of the sheets. This socket or T-shaped welding can be performed on normal pin machines in more simple devices. End of the rod is often attached to a spherical shape, and the end of the rod cross-section increases the pre-landing.
Usually on the spot weld machines is relatively small parts that can lay motionless in a fixed spot the car.
See also:
Electric Resistance Welding
Pliers for Welding
Spot Welding
The Spot Welding Process
The Spot Welding Process (Part 2)
Special Types of Spot Welding
Special types of spot welding
To improve performance, multi-point welding is used in which one cycle of the machine is welded by a few points. The electrodes are pressed against the product, which lies on the conductive copper lining. Current flows through the circuit electrode - a product - a copper lining - the product - the second electrode. Welded together two points. This method is called two-point one-sided welding. Multipoint machines typically have a hydraulic drive and operate on the principle of two-point one-sided welding.
Oil distributor distributes oil under high pressure in the cylinders and presses the individual electrodes to the product of two respective electrodes by applying a current to them, then the current is switched off, the electrodes are retracted, the oil is fed into the next couple of cylinders and so on, until the finished welding of the entire site. These machines can have up to 100 or more electrodes.
In some multi-point machines all at once the electrodes are pressed against the product, which provides a lower warpage, and greater accuracy of the product. The current spread between the electrodes pressed a special commutator having a very sophisticated device and comprising electrodes in pairs, carrying out the process of two-point one-sided welding. Both types of machines are only applicable in mass production, and for each part requires a rather complex manufacturing of devices with the appropriate placement of the electrodes and the hydraulic cylinders.
A few simple simultaneous welding of several points raised by means of welding or welding projections, which is a kind of spot welding. In this case, one of the workpiece or both pre vyshtampovyvayut protrusions (reliefs)
in places subject to welding. Trained lay down the details in a special welding machine that bears the name of "welding press." Welding of lugs may also be at the point of powerful machines with a straight course of the electrode and the electrode is replaced by a normal point-specific electrode for projection welding, plate-shaped solid. Simultaneously with the inclusion of current top electrode compresses the parts and compressed them to complete destruction of the projections. Thus, over the course of a machine is so spot welds, as it was stamped projections, their number can reach up to several dozen in one piece. To obtain high-quality welding requires accurate punching and a snug fit on all parts collected projections.
The method of projection welding can provide high performance. The electrodes are in good working conditions and have a great life because of their contact surface is very high and the pressure and current projections are concentrated in the welded parts.
The disadvantage of projection welding is a significant electrical power required for welding presses. The magnitude of this power for the welding of a 15-30 bulge that. Pressure on a ledge is typically 200-600 kg. A variety of projection welding is a welding rod to the ends of the sheets. This socket or T-shaped welding can be performed on normal pin machines in more simple devices. End of the rod is often attached to a spherical shape, and the end of the rod cross-section increases the pre-landing.
Usually on the spot weld machines is relatively small parts that can lay motionless in a fixed spot the car.
See also:
Electric Resistance Welding
Pliers for Welding
Spot Welding
The Spot Welding Process
The Spot Welding Process (Part 2)
Special Types of Spot Welding
1:59 AM
The Spot Welding Process (Part 2)
The process of spot welding
Upon cooling and solidification of molten metal core volume decreases. As a result, in the central part of the nucleus can be formed piping, porosity and friability of the metal. The thicker the metal, the greater the adverse effect of shrinkage and the greater the probability of defect formation. The most reliable way to deal with them is to increase the operating pressure, and the transition to the cycles of welding forging.
Usually in the welded joint is located a few points, so that the welding has to be the diversion of current through a previously welded points, shunt point to be welded. Having previously welded points is decreased efficiency of the electrodes on welded pressure point, as part of this pressure is perceived earlier welded points. Therefore, the welding of several closely spaced points of the average strength of the points is lower than when welding a single point. The strongest point in the node is usually the first one.
For spot welding the metal contamination in the weld zone must first be carefully removed by brushing, pickling in acid, opeskostruivaniem etc. Build a spot welding should as closely as possible to ensure a snug fit of parts before welding. The presence of the gap between the components absorbs a significant part of the pressure on the deformation of the electrode parts to solid ground, the actual pressure on the sedimentary point becomes insufficient and the strength of the scatter of points is obtained. The requirements for precision assembly increased with increasing thickness of the sheets.
There are so-called soft and hard modes of spot welding. When the soft modes are moderates current, current density at the working electrode surface is typically less than 100 A / mm 2 . For hard modes of the current density reaches the welding of steel to 120-300 A/mm2.
The soft modes are characterized by a greater length of time of welding, smoother heating, reduced power welding. The advantages of soft modes include reducing the power consumption of the network, reducing network load, lower power and cost of the necessary machinery of contact, reducing the hardening of the fusion zone. Rigid regimes require high power machines, increase the maximum load on the network. The advantages of hard welding conditions include reducing welding time, increase productivity. The pressure of the electrodes is usually taken within 3.8 kg / mm 2 .
Improperly installed or violation of the welding process requirements may lead to a variety of spot welding defects. The most dangerous is the lack of fusion defect, characterized by the absence of molten core point or small by its size. Risk of lack of penetration is increased by the fact that it is not always reliably detected by visual inspection of products at acceptance. May occur as defects such as surface and podplavlenie burn-through metal, deep indentations on the surface of the metal shell and the porosity of the molded core.
Spot welding is mainly connected components of low carbon steel having excellent weldability. Alloy steels are prone to hardening and steel with high carbon content should be welded to the soft modes. When welding on hard regimes the core point and the surrounding area of influence is strongly quenched and exhibit an increased tendency to form cracks. High-strength steel demand to increase the working pressure during welding.
After welding, heat treatment of products is sometimes necessary to remove the internal stresses generated by the welding process, or to improve the structure of the metal, mainly for the destruction of the structure of martensite is especially dangerous. Typically, heat treatment is reduced to a high holiday. Most subsequent heat treatment can be repeated by passing the current directly to the point the car immediately after the welding point.
Good welded austenitic stainless chromium-nickel steels of 18-8. To reduce the decomposition of austenite and the precipitation of carbides are welded on hard regimes, with the least possible time welding. Apply high pressure, requiring electrodes of high-strength alloys. Welding time is reduced to 0.01 seconds per point for the thin material. Can spot welding of aluminum, aluminum and magnesium alloys. Due to the high thermal and electrical conductivity of aluminum for its spot welding requires a large current density at the electrodes, reaching in some cases, the 1000-1500 A / mm 2 . In this case the aluminum particles easily stick to the electrodes and the particles of copper electrodes stick to the aluminum sheets. To reduce the adhesion requires a thorough cleaning of the surfaces of sheets and the working surface of electrodes. Aluminum alloys are usually welded together a little better commercially pure aluminum due to increased electrical resistance.
See also:
Electric Resistance Welding
Pliers for Welding
Spot Welding
The Spot Welding Process
The Spot Welding Process (Part 2)
Special Types of Spot Welding
Upon cooling and solidification of molten metal core volume decreases. As a result, in the central part of the nucleus can be formed piping, porosity and friability of the metal. The thicker the metal, the greater the adverse effect of shrinkage and the greater the probability of defect formation. The most reliable way to deal with them is to increase the operating pressure, and the transition to the cycles of welding forging.
Usually in the welded joint is located a few points, so that the welding has to be the diversion of current through a previously welded points, shunt point to be welded. Having previously welded points is decreased efficiency of the electrodes on welded pressure point, as part of this pressure is perceived earlier welded points. Therefore, the welding of several closely spaced points of the average strength of the points is lower than when welding a single point. The strongest point in the node is usually the first one.
For spot welding the metal contamination in the weld zone must first be carefully removed by brushing, pickling in acid, opeskostruivaniem etc. Build a spot welding should as closely as possible to ensure a snug fit of parts before welding. The presence of the gap between the components absorbs a significant part of the pressure on the deformation of the electrode parts to solid ground, the actual pressure on the sedimentary point becomes insufficient and the strength of the scatter of points is obtained. The requirements for precision assembly increased with increasing thickness of the sheets.
There are so-called soft and hard modes of spot welding. When the soft modes are moderates current, current density at the working electrode surface is typically less than 100 A / mm 2 . For hard modes of the current density reaches the welding of steel to 120-300 A/mm2.
The soft modes are characterized by a greater length of time of welding, smoother heating, reduced power welding. The advantages of soft modes include reducing the power consumption of the network, reducing network load, lower power and cost of the necessary machinery of contact, reducing the hardening of the fusion zone. Rigid regimes require high power machines, increase the maximum load on the network. The advantages of hard welding conditions include reducing welding time, increase productivity. The pressure of the electrodes is usually taken within 3.8 kg / mm 2 .
Improperly installed or violation of the welding process requirements may lead to a variety of spot welding defects. The most dangerous is the lack of fusion defect, characterized by the absence of molten core point or small by its size. Risk of lack of penetration is increased by the fact that it is not always reliably detected by visual inspection of products at acceptance. May occur as defects such as surface and podplavlenie burn-through metal, deep indentations on the surface of the metal shell and the porosity of the molded core.
Spot welding is mainly connected components of low carbon steel having excellent weldability. Alloy steels are prone to hardening and steel with high carbon content should be welded to the soft modes. When welding on hard regimes the core point and the surrounding area of influence is strongly quenched and exhibit an increased tendency to form cracks. High-strength steel demand to increase the working pressure during welding.
After welding, heat treatment of products is sometimes necessary to remove the internal stresses generated by the welding process, or to improve the structure of the metal, mainly for the destruction of the structure of martensite is especially dangerous. Typically, heat treatment is reduced to a high holiday. Most subsequent heat treatment can be repeated by passing the current directly to the point the car immediately after the welding point.
Good welded austenitic stainless chromium-nickel steels of 18-8. To reduce the decomposition of austenite and the precipitation of carbides are welded on hard regimes, with the least possible time welding. Apply high pressure, requiring electrodes of high-strength alloys. Welding time is reduced to 0.01 seconds per point for the thin material. Can spot welding of aluminum, aluminum and magnesium alloys. Due to the high thermal and electrical conductivity of aluminum for its spot welding requires a large current density at the electrodes, reaching in some cases, the 1000-1500 A / mm 2 . In this case the aluminum particles easily stick to the electrodes and the particles of copper electrodes stick to the aluminum sheets. To reduce the adhesion requires a thorough cleaning of the surfaces of sheets and the working surface of electrodes. Aluminum alloys are usually welded together a little better commercially pure aluminum due to increased electrical resistance.
See also:
Electric Resistance Welding
Pliers for Welding
Spot Welding
The Spot Welding Process
The Spot Welding Process (Part 2)
Special Types of Spot Welding
1:57 AM
The Spot Welding Process
on the process of spot welding
The process of spot welding
After switching current passes from one electrode to another through the metal parts and metal heats up more than just a place of contact details. Heating of the metal surface under the electrodes when properly conducted process is negligible, since the contact electrode - the product has relatively little resistance due to the softness and high electrical conductivity of the electrode metal and the electrode is cooled rapidly under running water. The passage of current causes heating and melting the metal in the welding zone, creating the flow core, having a lenticular shape (see Fig.). The diameter of the core weld point in ordinary cases, has a value of 4-12 mm. Spot welding without melting the metal core point though is possible (for mild steel), but is not sufficiently reliable and, therefore, in practice almost never used. Welding of metals having poor weldability in a plastic state, is only possible with sufficient molten metal in the core point.
Spot welding is a unique process that combines the melting of metal and molded to obtain the structure of a welded joint with a large sediment pressure. Pressure should be sufficient to overcome the rigidity of the product and carry out the necessary plastic deformation, ensuring adequate strength of welded points. The required pressure increases rapidly with increasing thickness of the base metal. Air pressure is fully transmitted to the electrodes, having a small work surface, carrying a large thermal and electrical load. In a large thickness of the base metal electrode load is so high that their life is declining rapidly. Therefore, spot welding is used primarily for the small thickness of the metal, not more than 5-6 mm. The diameter of the nucleus determines the strength of the points mainly depends on the diameter of the working electrode surface, plate thickness, pressure, current, and the time of his passing. If incorrectly chosen mode of welding can not occur enough melting point metal and get imperfections. When the core is molten, the adjacent area around the circumference of the metal is in a plastic state, impact pressure of the electrodes. The pressure creates the seal ring ductile metal, retaining the liquid metal core. With low pressure sealing ring can not retain the liquid metal core and the inner splash occurs in the gap between the metal sheets.
With increasing time of passage of the current diameter and height of the growing nucleus. An excessive increase in the size of the nucleus weakens its shell from the heated solid metal, and there is a strong indentation of the metal under the electrodes, leading to the outdoor splash of molten metal and reduce the strength of the point. After switching off the current starts cooling and solidification of the molten core point.
The crystallization of the molten metal comes from the surface of the nucleus to the middle. As a result, the kernel has a columnar dendritic structure.
See also:
Electric Resistance Welding
Pliers for Welding
Spot Welding
The Spot Welding Process
The Spot Welding Process (Part 2)
Special Types of Spot Welding
The process of spot welding
After switching current passes from one electrode to another through the metal parts and metal heats up more than just a place of contact details. Heating of the metal surface under the electrodes when properly conducted process is negligible, since the contact electrode - the product has relatively little resistance due to the softness and high electrical conductivity of the electrode metal and the electrode is cooled rapidly under running water. The passage of current causes heating and melting the metal in the welding zone, creating the flow core, having a lenticular shape (see Fig.). The diameter of the core weld point in ordinary cases, has a value of 4-12 mm. Spot welding without melting the metal core point though is possible (for mild steel), but is not sufficiently reliable and, therefore, in practice almost never used. Welding of metals having poor weldability in a plastic state, is only possible with sufficient molten metal in the core point.
Spot welding is a unique process that combines the melting of metal and molded to obtain the structure of a welded joint with a large sediment pressure. Pressure should be sufficient to overcome the rigidity of the product and carry out the necessary plastic deformation, ensuring adequate strength of welded points. The required pressure increases rapidly with increasing thickness of the base metal. Air pressure is fully transmitted to the electrodes, having a small work surface, carrying a large thermal and electrical load. In a large thickness of the base metal electrode load is so high that their life is declining rapidly. Therefore, spot welding is used primarily for the small thickness of the metal, not more than 5-6 mm. The diameter of the nucleus determines the strength of the points mainly depends on the diameter of the working electrode surface, plate thickness, pressure, current, and the time of his passing. If incorrectly chosen mode of welding can not occur enough melting point metal and get imperfections. When the core is molten, the adjacent area around the circumference of the metal is in a plastic state, impact pressure of the electrodes. The pressure creates the seal ring ductile metal, retaining the liquid metal core. With low pressure sealing ring can not retain the liquid metal core and the inner splash occurs in the gap between the metal sheets.
With increasing time of passage of the current diameter and height of the growing nucleus. An excessive increase in the size of the nucleus weakens its shell from the heated solid metal, and there is a strong indentation of the metal under the electrodes, leading to the outdoor splash of molten metal and reduce the strength of the point. After switching off the current starts cooling and solidification of the molten core point.
The crystallization of the molten metal comes from the surface of the nucleus to the middle. As a result, the kernel has a columnar dendritic structure.
See also:
Electric Resistance Welding
Pliers for Welding
Spot Welding
The Spot Welding Process
The Spot Welding Process (Part 2)
Special Types of Spot Welding
1:53 AM
Pliers for Welding
the grip for a point of contact welds
Welding tongs/pliers.
Widespread use of spot welding in the manufacture of large dimensions, such as cars, airplanes, cars, light metal construction, etc., required to create a mobile and portable point machines and mobile devices to fixed machines, welding products allow larger sizes.
Portable devices for spot welding have different names: pliers, clamps, welding guns for spot welding, etc.
In most cases, the most convenient spot welding device, connected to the welding transformer, flexible wires, while the product is moved only one welding device having a relatively low weight, and the most difficult part of the contact machines, welding transformer, ie, remains in place.
The presented figure show several types of portable welding clamp with pneumatic pressure of being connected to the transformer flexible wires. The wire or cable for connecting welding equipment has a special device that provides a minimum inductance of the welding circuit and the minimum weight of the cable. To reduce the weight of the flexible multi-core cable is a rubber hose and cool running water. Such devices are widely used, for example, in the manufacture of automobiles. In some cases, for welding thin metal pole are comfortable welding guns. The gun is attached to one end of the welding transformer secondary winding, the other end of the coil attached to the product. This allows for the weld spot anywhere in the product, without supplying an electrode on the back side of the metal.
See also:
Electric Resistance Welding
Pliers for Welding
Spot Welding
The Spot Welding Process
The Spot Welding Process (Part 2)
Special Types of Spot Welding
Welding tongs/pliers.
Widespread use of spot welding in the manufacture of large dimensions, such as cars, airplanes, cars, light metal construction, etc., required to create a mobile and portable point machines and mobile devices to fixed machines, welding products allow larger sizes.
Portable devices for spot welding have different names: pliers, clamps, welding guns for spot welding, etc.
In most cases, the most convenient spot welding device, connected to the welding transformer, flexible wires, while the product is moved only one welding device having a relatively low weight, and the most difficult part of the contact machines, welding transformer, ie, remains in place.
The presented figure show several types of portable welding clamp with pneumatic pressure of being connected to the transformer flexible wires. The wire or cable for connecting welding equipment has a special device that provides a minimum inductance of the welding circuit and the minimum weight of the cable. To reduce the weight of the flexible multi-core cable is a rubber hose and cool running water. Such devices are widely used, for example, in the manufacture of automobiles. In some cases, for welding thin metal pole are comfortable welding guns. The gun is attached to one end of the welding transformer secondary winding, the other end of the coil attached to the product. This allows for the weld spot anywhere in the product, without supplying an electrode on the back side of the metal.
See also:
Electric Resistance Welding
Pliers for Welding
Spot Welding
The Spot Welding Process
The Spot Welding Process (Part 2)
Special Types of Spot Welding