What Is Aluminum Welding?

Aluminum alloy welding ^[1] refers to the welding process of aluminum alloy materials. Aluminum alloy has high strength and light weight. The main welding processes are manual TIG welding (non-melting extremely inert gas shielded welding), automatic TIG welding and MIG welding (melting extremely inert gas shielded welding), its base metal, welding wire, shielding gas, and welding equipment.

Aluminum and aluminum alloys play an important role in various materials used in modern engineering technology. It ranks second only to steel in the world's annual output and ranks first among non-ferrous metals. ^[1]

1.Tungsten arc welding

Tungsten arc welding is mainly used for aluminum alloys, which is a better welding method. However, tungsten arc welding equipment is more complicated and is not suitable for operation in open conditions.

2.Resistance spot welding and seam welding

This welding method can be used to weld aluminum alloy sheets with a thickness of less than 5mm. However, the equipment used in welding is relatively complicated, the welding current is large, and the productivity is high, which is especially suitable for mass production of parts and components.

3.Pulse argon arc welding

Pulse argon arc welding can improve the stability during the welding process. The parameters can be adjusted to control the arc power and weld formation. Welding parts have small deformation and small heat affected zone, especially suitable for thin plates, all-position welding and other occasions, as well as welding of heat-sensitive forged aluminum, hard aluminum, super hard aluminum, etc.

1.Requirements for storage environment and auxiliary materials for welding production of aluminum alloy

(1) Requirements for production storage temperature and humidity

The production and storage environment of aluminum alloy must be dustproof, waterproof and dry. The ambient temperature is usually controlled above 5 , and the humidity is controlled below 70%. Should try to ensure that the humidity of the welding environment is not too high, too high humidity will significantly increase the probability of porosity in the weld, which will affect the welding quality. The violent flow of air will cause insufficient gas protection, which will cause welding pores.

1. Selection of welding wire

For the 6005A, 6082, and 5083 base materials, the selected wire grade is 5087 / AlMg4.5MnZr. The 5087 wire not only has good crack resistance, superior porosity resistance, but also good strength properties. For the selection of wire specifications, preference is given to large diameter wire. The same welding filling amount is equal to the weight of the welding wire. The surface area of the large size wire is smaller than that of the small size wire. Therefore, the large size wire has less surface pollution, that is, the oxidation area is smaller, and the welding quality is easier to meet the requirements. . In addition, the wire feeding process of the large diameter welding wire is easier to operate. For base materials with a thickness of 8 mm or less, a 1.2 mm diameter wire is generally used, and for base materials with a thickness of 8 mm or more, a 1.6 mm diameter wire is used. The automatic welding machine uses a 1.6mm diameter welding wire.

2. Selection of protective gas

Ar100% is characterized by stable arc and convenient arc starting. For base materials with a thickness of 8mm or less, Ar100% is generally used for welding. For base materials with a thickness of 8mm and above and welds with high porosity requirements, Ar70% + He30% is used for welding. The characteristics of helium are: 9 times the thermal conductivity of argon, faster welding, reduced porosity and increased penetration. When welding thick plates, the penetration of Ar100% and Ar70% + He30%. The choice of gas flow is not as large as possible. Excessive flow will cause turbulence, resulting in insufficient protection of the molten pool, and the reaction between air and deposited metal will change the weld structure, reduce performance, and increase the tendency of welding pores.

1. Bevel treatment

Butt welds with a thickness of less than 3mm may not be grooved, and only an angle of -0.5 to 1mm is required on the back of the weld, which is conducive to the emission of gas and avoiding back grooves. The effect of chamfering on the back side on the weld. The groove angle of aluminum alloy thick plate is larger than that of steel plate. The unilateral groove is generally 55 °, and the bilateral groove is 35 ° on each side. This can improve the accessibility of welding and reduce the probability of unfused defects.

For HV or HY joints in thick plate T-joints, it is required to fill the outside of the groove and add a fillet weld so that the total size S of the weld is not less than the plate thickness T. Thick plate T-joint welding requirements.

1. Wash the welded joint carefully with a stiff brush in hot water.

2. Dip the weldment in a chromic anhydride aqueous solution or a potassium dichromate solution at a temperature of 60 to 80 ° C and a mass fraction of 2% to 3% for about 5 to 10 minutes, and carefully wash it with a hard brush. Alternatively, the weldment is immersed in a nitric acid solution with a mass fraction of 10% at 15-20 ° C for 10-20 minutes.

3. Wash and wash the weldment in hot water.

4. Dry the weldment with hot air or dry it in a 100 ° C drying oven ^[2]

1. Before welding, use mechanical or chemical methods to remove the oxide on the bevel and surrounding parts of the workpiece and the surface of the welding wire;

2. Use qualified protective gas for protection during welding;

3. During gas welding, a flux is used, and the oxide film on the surface of the molten pool is continuously broken by the welding wire during the welding process.

1. Socket connection of copper and aluminum pipes in the refrigeration industry

1. "Welding Procedure Evaluation Rules" DL / T868-2004;

2. "Technical Regulations for Radiographic Inspection of Butt Welding Joints of Steel Pressure Pipes" DL / T821-2002;

3. Welding Rules for Steel Pressure Vessels JB / T4709-2000;

4. "Technical Specifications for Construction and Acceptance of Electric Power Construction" (Welding of Thermal Power Plants) DL5007-92;

5. "Basic Types and Dimensions of Welded Joints" GB985-986-80;

6. "Code for Construction Quality Acceptance of Steel Structure Engineering" GB50205-2001.