(1) It is easy to have a high affinity between alumina and oxygen, and can be combined with oxidation in the atmosphere to form a dense and insoluble oxide film (alumina), which has a melting point of up to 2050 C, and with time And the increase in temperature, the thickness of the oxide film is also increasing. When the solder is soldered, the oxide film is covered on the upper side, which hinders the bonding between the filler metal and the base metal, and impedes the wetting of the metal; in addition, the density of the oxide film is also large, about 1.4 times that of aluminum, and is easy. Forming slag. Therefore, in the welding of aluminum and 6061 aluminum plates, in order to ensure the welding quality, the oxide film on the surface of the letter must be removed before welding, and the metal at the high temperature of the molten metal box is effectively protected from being oxidized during the welding process.
(2) It is easy to generate pores Since the 6061 aluminum plate and the aluminum alloy do not contain carbon, there is no condition for attempting CO, and the gas generated during welding is mainly hydrogen. The solubility of hydrogen in the molten metal is the largest in aluminum. Therefore, aluminum can dissolve a large amount of hydrogen at high temperature, and the hydrogen solubility in the solidification process decreases from 0.69 ml/100 g to 0.036 ml/100 g, which is about 20 times different. Almost all of the hydrogen in the liquid aluminum precipitates to form bubbles. However, due to the low density of aluminum and aluminum alloy, the bubble floats slowly in the bath, and the green heat conductivity is strong, and the condensation is fast, which is not conducive to the bubble. Therefore, when the aluminum is welded, the weld has a tendency to generate pores.
(3) The welding deformation and the tendency to crack formation are large. The coefficient of linear expansion of the 6061 aluminum plate is about twice as large as that of the steel, and the shrinkage rate during solidification is twice as large as that of the steel. Therefore, a large inner portion is produced when welding aluminum and aluminum alloy. Gravity and welding deformation. Secondly, the aluminum alloy has a low temperature and plasticity, and therefore, it is prone to thermal cracking under a large internal attraction.
(4) The strength is low at high temperature, the aluminum alloy element is easy to evaporate and burn, and the strength of aluminum is 0.1MPA at 37C, which is often the weight that can not support the liquid molten pool, and the deformation of the weld metal is sometimes broken. The weld metal is slumped and burnt through. Therefore, the reverse pad method is generally used for welding.
(5) There is no color change. When the temperature of copper or steel is close to the melting point, the color change will occur, so it must be operated during welding, not the melting zone.
Article source: www.bombgroup17.com 6061 aluminum plate Aluminum alloy plate, aluminum alloy bar