- deformable used in the form of forgings, rolled, etc., are divided into Thermally and netermouprochnyaemye.
- casting (AL) , used for casting, welding these alloys used in the correction of casting defects.
- BP and AD1 - technical aluminum;
- AMts - aluminum-manganese alloys (on the basis of Al-Mn);
- AMg - aluminum-magnesium alloys (on the basis of Al-Mg).
- D1, D16, D18, D19, M40, VAD1, VD17 - aluminum-copper-magnesium (duralumin), on the basis of Al-Cu-Mg;
- B92, V92TS, ACM - aluminum-magnesium-zinc;
- AK6, AK6-1, AK8, AD31, AD33, AD35, AB - based on the systems Al-Mg-Si and Al-Mg-Si-Cu;
- AK2, AK4, AK4-1 - on the basis of Al-Mg-Cu-Fe-Ni;
- D20 and D21-aluminum-copper-manganese;
- VAD23 - on the basis of Al-Mn-Cu-Li-Cd;
- V93, V94, V95, B96 - on the basis of Al-Mg-Cu-Zn.
A. Education refractory aluminum oxide Al 2 O 3 (melting point 2050 ° C) with a higher density than aluminum, making it difficult to fusion edge connectivity and contributes to the pollution of the weld metal particles of the film. Before welding, to remove the film you want to clean the surface and the adjacent edges of the base metal and carefully filler metal surface (due to the large surface area and relatively small volume) mechanically or by etching.
Oxide film that forms during welding of aluminum, is removed either by cathode sputtering , or the use of fluxes , which provide for its dissolution or destruction of the transfer of volatile compounds.
Cathode sputtering is possible when welding on the reverse polarity. When argon welding consumable electrode polarity reverse does not apply because of the maldistribution of heat between the electrode and the workpiece (70% and 30% of the electrode on the workpiece). For this reason, welding is carried out on an alternating current at which the destruction of the film takes place in the half-periods of reverse polarity.
Two. At high temperatures dramatically reduces the strength and solid metal parts nerasplavivsheysya edges may collapse under the weight of the weld pool. Aluminum has a high fluidity and can flow through the root of the weld. It almost does not change its color when heated, so during welding is difficult to control the size of the weld pool. To avoid burn-through or failure in the single-layer welding of metal or welding the first layers of multipass welds at high heat input is used form the lining of ceramic, steel or graphite.
3. Due to the high value of the coefficient of linear expansion, and low modulus of elasticity of aluminum alloys have a high propensity for warping (deformation). To reduce the strain can be used special technological measures (optimal modes of welding, heating, etc.)
4. Welding hampered not only by the appearance of the oxide film, but also due to hydrogen porosity, which reduces the ductility and strength of the metal. The pores occur mainly in the weld metal, as well as at the fusion line. Especially prone to the formation of pores are alloys of AMg.
In this connection it is necessary to carry out a thorough chemical cleaning of welding wire and mechanical cleaning and degreasing of the welded edges. When welding heavy sections of metal leads to a decrease in porosity and the accompanying pre-heated to a temperature of 150-250 ° C.
5. Due to the high thermal conductivity of aluminum welding is required for its powerful heat source. In some cases, we recommend pre-heating of the initial sections of the weld to a temperature of 120-150 ° C and the associated heating.
6. When welding in the weld metal can form hot cracks, which is caused by processes internal strains and stresses in the crystallization of the metal weld pool. To reduce the likelihood of their occurrence in the welds can be added to the special modifiers that improve the crystalline structure of the joint, and should avoid the proximity of joints.
Inert gas welding
Aluminum welding in inert gas is nonconsumable (tungsten) or consumable electrodes. As the inert gas argon is used in Class I or higher, high purity helium or a mixture of argon and helium.
Tungsten electrode may be ittrirovannymi or lantanirovannymi. The use of tungsten electrode with a diameter of 2 to 6 mm is suitable for welding of metal up to 12 mm. Filler wire with a diameter of 2 to 5 mm is selected depending on the type of aluminum alloy. For example, a commercial aluminum wire can be used stamps AB, AC, or AD, for alloys such as AMG - wire of similar marks, but with an increased amount of magnesium (1-1.5%) to compensate for his intoxication.
Manual TIG argon welding can be performed at facilities such as AC UDG (UDG-300, UDG-500) with a flow of argon from 6 to 15 l / min. Welding of metal can be produced in helium at a flow rate of helium in the 1.8-2.2 times higher than argon. When welding in argon arc voltage of 15-20 V, welding in helium is 25-30 V.
TABLE. Recommended modes of the metal tungsten electrode welding
| Metal thickness (mm) | Diameter (mm) | Current (A) | ||
| tungsten electrode | filler wire | in argon | in helium | |
| 2.1 | 2 | 2.1 | 50–70 | 30–40 |
| 4.6 | 3 | 2.3 | 100–130 | 60–90 |
| 4.6 | 4 | 3 | 160–180 | 110–130 |
| 6.10 | 5 | 4.3 | 220–300 | 160–240 |
| 11–15 | 6 | 4 | 280–360 | 220–300 |
To improve performance, welding tungsten electrode (3-5 times) can be used three-phase arc. The more powerful heat source allows one-pass welding of aluminum in the lining thickness of 30 mm.
 |
| Three-phase arc welding of aluminum |
Welding consumable electrode is performed in pure argon and a mixture of argon and helium (70% helium) wire diameter 1.5-2.5 mm at a constant current of reverse polarity. Cutting edges can be V-shaped or X-shaped with an opening angle of 70-90 ° (for placement in the cutting tip of the burner), or ryumkoobraznoy; blunting - 6 mm.
Welding speed depends on the section of the seam and can reach 40 m / h The wire is fed at a rate of up to 400 m / h With a blend of 30% argon and 70% helium increases penetration depth and width, allowing a single run in the lining to perform welding metal thickness of 16 mm, and in two passes - up to 30 mm. The weld in this case takes on a more favorable shape.
Automatic Arc Welding
Automatic welding of aluminum and its alloys is performed over a layer of half-open arc or submerged arc flux submerged.
Automatic welding consumable electrode layer on the flux can be produced with the use of fluoride-chloride fluxes makes the AN-AN-A1 and A4. Flux grade AN-A1 is used to connect the technical aluminum, flux AN-grade A4, containing no NaCl, - for the aluminum-magnesium alloys. For the alloys of this type the presence of NaCl in the flux is invalid because the expense of aluminum and magnesium from the reduced flux of sodium, which enters into the joint and leads to the appearance of voids in the metal and reduce the ductility.
Automatic welding sheet is the layer of flux, since even the unfused flux has a high electrical conductivity, shunts and breaks the electric arc process stability. The width and thickness of the poured flux depends on the thickness of aluminum sheet (as a rule, the width of 25-45 mm and the thickness of 7-16 mm). To avoid the leaking of the molten metal from the reverse side of the weld steel forms the lining is required. The arc is powered by direct current reverse polarity.
Automatic submerged arc welding is usually performed on the split-electrode AC or DC reverse polarity. Apply flux with low electrical conductivity, for example, ceramic fluxes marks HA-HA-64 and 64A.
Gas welding
When gas welding of aluminum as a fuel gas is mainly used acetylene. Acetylene flow is about 100 l / h at 1 mm thickness of the base metal.
The diameter of filler rod, which is a wire made of aluminum or its alloys, usually 1,5-5,5 mm depending on the thickness of the workpiece.
To prevent oxidation of the metal and oxide removal using special fluxes, for example, marks the AF-4A (50% KCl, 28% NaCl, 14% LiCl, 8% NaF). When welding flux injected with either filler stick, or pre-applied to the welded edges in the form of paste diluted in water. The flux in the reconstituted state can not store more than 8-10 hours
With a thickness exceeding 4 mm billet is desirable to carry out cutting edges. When the thickness of sheets above 8 mm carry a general or local heating. Welding is the "left" way. Upon completion of welding fluxes to remove welds were washed with warm water or 2% solution of chromic acid.
Manual arc welding
Manual arc welding with coated electrodes used for the procurement of commercially pure aluminum, aluminum alloys with silicon alloys AMg (with a magnesium content up to 5%) and AMts thickness product of more than 4 mm. It runs on DC reverse polarity is usually at high speeds without bending vibrations. When the thickness of the metal 10 mm and above is desirable to carry out a breaker welded edges.
As a rule, the butt joint. Do not use tee and lap joints, as the slag can zatech in the gaps, making it difficult to remove by washing. The remains of slag can lead to corrosion.
Before welding, the details should be warmed to a temperature of 100-400 ° C depending on their thickness. Metal rod electrode is made of wire with a composition close to the composition of the base metal (eg, electrodes stamps Oz-1). For the alloys used AMg wire with a high amount of magnesium (1.5-2%) to compensate him for welding fumes. The main components of electrode coatings are cryolite, fluoride and chloride salts of potassium and sodium.
Manual welding of carbon electrode is used only for non-critical designs. Runs on DC straight polarity. As the electrodes used carbon or graphite rods. When the thickness of a workpiece is 2.5 mm cutting edges. The diameter of filler rods of 2-8 mm. A layer of flux is applied either to the rod or welded to the edge as a paste.
Electroslag welding
Electroslag welding of aluminum and its alloys is performed for product thicknesses from 50 to 250 mm and is especially effective for large thicknesses. Conducted on alternating current consumable mouthpieces or plate electrodes, with fluxes on the basis of alkaline earth halides and alkali metals (eg, AN-301 and AN-302). The seam is formed by water-cooled copper or graphite molds. Welding speed is 6.8 m / h The resulting welds have strength equal to 80-100% of the strength of the base metal.
Plasma welding
Plasma welding due to the high concentration of energy at the point of heating and deep penetration is considered to be a promising method of joining aluminum and its alloys.
The main advantages of plasma welding of aluminum:
- high speed;
- stability and ease of process control in comparison with the manual metal arc welding;
- much smaller zone of thermal influence.
Electron-beam welding
Electron beam welding - one of the most effective ways of joining components made of aluminum and its alloys.
The main advantages of electron beam welding of metal:
- obtaining dense high-quality welds;
- minimum heat input;
- minimum softening of aluminum in the heat affected zone;
- high welding speed;
- minimal deformation structures.
See also:
argon welding (argon-arc welding)
welding wire
welding equipment
welding flux
gas welding technology
manual welding
electroslag welding technology
Welding of metals:
welding of cast iron
welding of aluminum
welding of titanium
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