Seven elements of preparation before aluminum welding

by:Zeyi     2021-12-26
Groove treatment For butt welds with a thickness of less than 3mm, grooves are not required. You only need to pour a 0.5-1mm angle on the back of the weld. This is good for gas emission and avoids back grooves. Whether the back side is chamfered or not has an influence on the weld, the bevel angle of aluminum alloy thick plate is larger than that of steel plate. Single-side bevels generally use 55° bevels, and bilateral bevels use 35° bevels on each side. In this way, the accessibility of welding can be improved, and the probability of non-fusion defects can be reduced at the same time. For HV or HY joints in thick plate T joints, it is required to fill the groove and add a fillet weld so that the total weld size S is not less than the plate thickness T. Clean up work before welding Welding aluminum alloy requires the cleanest preparation work, otherwise its corrosion resistance will be reduced and porosity will easily occur. Welding aluminum alloy should be thoroughly distinguished from the habit of welding steel. Tools that have been used for welding steel are strictly prohibited for welding aluminum alloys. Clean the oxide film and other impurities in the weld area, and use a stainless steel brush or acetone to clean as much as possible. Do not use a grinding wheel for grinding, because grinding with a grinding wheel will only fuse the oxide film on the surface of the welding material, but will not actually be removed. And if a hard grinding wheel is used, impurities in it will enter the weld and cause hot cracks. In addition, because the Al2O3 film will regenerate and accumulate in a very short time, in order to make the oxide film affect the weld as little as possible, welding should be performed immediately after cleaning. Control of preheating temperature and interlayer temperature When welding thick plates with a thickness of more than 8mm, preheating must be carried out before welding. The preheating temperature is controlled between 80°C and 120°C, and the interlayer temperature is controlled at 60°C. ~100℃. Preheating temperature is too high, in addition to the harsh working environment, it may also affect the alloy properties of aluminum alloy, such as joint softening and poor appearance of welds. Too high interlayer temperature will also increase the probability of aluminum welding heat cracks. Reasonable selection of specification parameters The physical and chemical properties of aluminum alloy and steel are far different, and the welding specification parameters of aluminum alloy should be tested and determined according to the welding characteristics of aluminum alloy. The thermal conductivity of aluminum alloy itself is large (about 4 times that of steel) and heat dissipation is fast. Therefore, at the same welding speed, the heat input when welding aluminum alloy is 2 to 4 times larger than when welding steel. If the heat input is not enough, the problem of insufficient penetration or even non-fusion will easily occur, especially at the beginning of the weld. The wire feeding speed should be increased appropriately. The wire feeding speed is closely related to the current, voltage and other specification parameters, and they are matched with each other. When the welding current is increased, the wire feeding speed should be increased accordingly. The choice of welding speedFor thin plate welds, in order to avoid overheating of the welds, a smaller welding current and faster welding speed are generally used; for thick plate welds, in order to make the weld fusion fully and the weld gas fully escape, adopt Larger welding current and slower welding speed. The choice of welding torch angle In the welding direction, the welding torch angle is generally controlled at about 90°, too large or too small will cause welding defects. Torch angle is too large, resulting in insufficient gas protection and pores; too small an angle may also cause the liquid aluminum to reach the front of the arc, so that the arc cannot directly act on the weld and cause unfusion. ————The article comes from the Internet. If there is any infringement, please contact to delete it.
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