[China Aluminum Network] What are the precautions for welding aluminum alloys? How to weld aluminum alloy? Aluminum alloy material, high strength and light weight. The main welding process is manual MIG welding and automatic MIG welding, its parent material, welding wire, shielding gas, and welding equipment. Aluminum alloys are alloys in which aluminum is the matrix element and one or more alloying elements are added. Due to the concentrated heat energy of the TIG welding torch, stable arc burning, dense metal welds, high strength and ductility of the welded joints, and excellent joint quality, it is a common method for welding aluminum alloys. In addition, we need to pay attention to the following six points when welding aluminum alloys: (I) High thermal conductivity The thermal conductivity and specific heat capacity of aluminum alloy are more than twice that of carbon steel and low alloy steel. The thermal conductivity of aluminum is more than ten times that of austenitic stainless steel. In the welding torch welding process, a large amount of heat is rapidly transferred to the inside of the base metal, and the molten pool is difficult to form. Therefore, energy with concentrated energy and large power should be used. It can also be preheated according to conditions such as structure size and ambient temperature. (b) No color change When the aluminum alloy weld pool metal changes from a solid state to a liquid state, there is no noticeable change in color. This is not the same as the red color of the steel before it is melted, which will inconvenience welding torch operations. It can not be accurately judged when the base material of the groove begins to melt. The molten aluminum has small surface tension, low strength, and good fluidity, which may easily cause collapse or burn-through of the weld metal. Therefore, aluminum welding operators are required to have more skilled operation skills, and are good at using the small changes in the surface of the molten pool to determine the heating temperature of aluminum; (III) Strong oxidizing power The affinity of aluminum and oxygen is very strong, and aluminum is easily oxidized in air to form a dense and strong film, and its melting point is as high as 2050°C far exceeding the melting point of aluminum and aluminum alloy. And the relative density of alumina film is larger, about 1.4 times that of aluminum. In the welding process using a welding torch, the aluminum oxide film will hinder the good bonding between the metals, and may cause slag inclusion. Alumina membranes also adsorb moisture, which, when welded, causes pores to form in the weld. Therefore, the oxides on the surface of the weldment must be strictly cleaned before welding, and reoxidation during the welding process must be prevented. (d) hot cracking tendency The coefficient of linear expansion of aluminum alloy is about twice that of carbon steel and low alloy steel. The volumetric shrinkage of aluminum during solidification is large, reaching 6.5%, while iron is 3.5%. Molten aluminum alloys have low strength at high temperatures. If the process is not properly performed, the weld seam and the near-seam zone will also have a large welding stress, restraint stress, and thermal stress during cooling. Therefore, when the aluminum welding pool is solidified, it is easy to produce shrinkage L, shrinkage, thermal cracks and high internal stress; (E) Evaporation loss Aluminum alloy contains low-boiling elements, such as magnesium, zinc, manganese, etc. Under the action of high-temperature arc, it is easy to evaporate and burn, thus changing the chemical composition of the weld metal, so that the performance of the weld decreases; (VI) High porosity sensitivity Aluminum alloy liquid baths can easily absorb hydrogen and other gases. A large amount of gas dissolved at high temperatures is too late to precipitate in the cooling and solidification process after the welding torch is welded, and a gas hole is formed in the weld. The moisture in the arc column atmosphere, the welding material, and the moisture absorbed by the oxide film on the base metal surface are all important sources of hydrogen in the weld. Therefore, it is necessary to clean the base material groove and welding wire before welding. Requirements for cleaning after welding aluminum alloy 1. Use a stiff brush to carefully wash the welded joint in hot water. 2, the weldment in the temperature of 60 ~ 80 °C, the mass fraction of 2% to 3% of the chromic anhydride solution or potassium dichromate solution dipping about 5 ~ 10min, and carefully brush with a hard hair brush. Or put the weldment in a nitric acid solution with a 10% mass fraction of 10 to 20°C and dip for 10 to 20 minutes. 3. Wash and wash the weldment in hot water. 4. The weldment is dried with hot air or dried in a drying oven at 100°C. Electronic Door Lock,Tower Base Station Electronic Locks,Electronic Locking System,Electronic Door Locking System Ningbo Hengchieh Locking Technology Co., Ltd. , https://www.hengchieh.com
What are the precautions for welding aluminum alloys?