ã€China Aluminum Industry Network】 Treatment of Grooves The butt welds with a thickness of less than 3mm can be grooved, and only a 0.5 to 1mm angle can be used on the back of the weld. This facilitates gas discharge and avoids back grooves. Whether the back side is chamfered or not, the angle of the groove of the aluminum alloy plate is larger than that of the steel plate. The unilateral groove generally uses a 55° groove and the bilateral groove uses a 35° groove on each side. This can improve the accessibility of the welding and at the same time reduce the occurrence of unfused defects. For HV or HY joints in thick plate T-joints, it is required to fill the bevel outside, and then add a fillet weld, so that the total weld seam size S is not less than the plate thickness T. Pre-weld cleaning Welding aluminum requires a relatively clean preparation, otherwise its ability to resist corrosion decreases and pores are easily generated. Welding aluminum should be thoroughly distinguished from the practice of welding steel. Welded steel has been used tools, it is strictly prohibited to use when welding aluminum alloy. Clean the oxide film and other impurities in the weld area. Use a stainless steel brush or wash with acetone as much as possible. Cannot be used to grind the grinding wheel, because grinding with a grinding wheel will only melt the oxide film on the surface of the welding material without actually removing it. And if hard wheels are used, impurities can enter the weld and cause hot cracks. In addition, since the Al2O3 film will be regenerated and accumulated in a very short time, in order to make the oxide film as little as possible affect the weld, welding should be performed immediately after the cleaning. Preheat temperature and interlayer temperature control When welding thick plates with a thickness of more than 8 mm, preheating before welding should be performed. The preheating temperature should be controlled between 80°C and 120°C, and the temperature between layers should be controlled between 60°C and 100°C. Preheating temperature is too high, in addition to the harsh operating environment, it may also affect the alloy properties of the aluminum alloy, joint softening, poor appearance of the weld appearance and other phenomena. Excessively high temperatures between layers will also increase the chance of hot cracking in aluminum welding. Reasonable choice of specification parameters The physical and chemical properties of aluminum alloys and steels are far from each other, and the welding specification parameters must be tested and determined according to the welding characteristics of aluminum alloys. The aluminum alloy itself has a large thermal conductivity (about 4 times that of steel), and it dissipates heat quickly. Therefore, at the same welding speed, the heat input during welding of aluminum alloy is 2 to 4 times greater than the heat input during welding of steel. If the heat input is not enough, the problem of insufficient penetration or even lack of fusion occurs, especially in the beginning of the weld. Wire feed speed should be properly adjusted The wire feed speed is closely related to the current, voltage, and other specification parameters and matches each other. When the welding current is increased, the wire feed speed should be increased accordingly. The choice of welding speed For thin plate welds, in order to avoid overheating of welds, smaller welding currents and faster welding speeds are generally used; for thick plate welds, larger welds are used to fully melt the weld and fully escape the weld gas. Current and slower welding speeds. Welding torch angle selection In the welding direction, the angle of the welding torch is generally controlled to be about 90°, too large and too small will cause welding defects. Excessive angle of the welding torch may cause insufficient gas protection to generate air holes. If the angle is too small, it may cause the liquid aluminum to reach the front end of the arc, so that the arc cannot directly act on the weld to cause unwelding.