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The most common problems in the welding process of 7075 alum

addtiame:2016/10/21 click:
With the continuous development of aluminum, aluminum processing technology has also been rapid development. However, because the aluminum has strong oxidation, low melting point, fast heat conduction, linear expansion of physical and chemical properties of various characteristic coefficient, high latent heat, so the choice of welding method, is easy to appear the following common problems:
1, aluminum and aluminum alloys in the liquid can dissolve a large number of hydrogen, the solid state almost does not dissolve hydrogen.
In the process of weld pool solidification and rapid cooling, hydrogen is less than overflow, which is easy to form hydrogen porosity. The moisture content in arc column atmosphere, welding material and the moisture content on the surface of the base material are the important sources of hydrogen in the weld. Therefore, the source of hydrogen should be strictly controlled to prevent the formation of pores. Aluminum steel
2, 7075 aluminum belt in the air and welding is very easy to oxidation, resulting in high melting point of (Al2O3), very stable, not easy to remove.
Before welding, chemical or mechanical methods should be used to remove the surface oxide film on the surface of the surface. When tungsten electrode argon arc welding, the AC power supply is used to remove the oxide film. Gas welding, the removal of oxide flux. In the welding, the welding heat can be increased, for example, helium arc heat, using helium or argon helium mixed gas protection, melting or the use of specification in gas arc welding, DC case, but does not need the cathode cleaning".
3, aluminum and Aluminum Alloy thermal conductivity and heat capacity are about two times more carbon and low alloy steel.
In the welding process, a large amount of heat can be quickly transmitted to the base metal, aluminum and Aluminum Alloy welding and energy consumption, in addition to a bath of molten metal, but also have more heat to unnecessary consumption of other parts of metal, this useless energy consumption than steel welding for welding is more significant. Joint access to high quality, we should try our best to adopt concentrated energy and power energy, sometimes by preheating process.
4, 7075 aluminum strip and Aluminum Alloy linear expansion coefficient is about two times of carbon steel and low alloy steel.
7075 aluminum strip welding weld pool solidification is prone to shrinkage, shrinkage, thermal crack and high internal stress, the production can be used to adjust the welding process and welding process to prevent the occurrence of thermal crack. In the case of corrosion resistance, aluminum silicon alloy welding wire can be used to weld aluminum alloy except Al Mg alloy. In the Al Si alloy, the hot cracking tendency of the silicon containing 0.5% is larger, with the increase of silicon content, the crystallization temperature range becomes smaller, the mobility is significantly increased, the shrinkage rate decreases, and the thermal cracking tendency also decreases accordingly. According to the production experience, when the silicon containing 5% ~ 6% can not produce hot cracking, and thus the use of SAlSi (silicon content 6% ~ 4.5%) welding wire will have a better anti cracking performance.