Arc welding in inert gas argon on aluminum and aluminum alloys with non-melting tungsten electrode - (VIG). The welding of aluminum and aluminum alloys is performed with alternating current in a protective argon. Welding of Aluminum is possible even in a material thickness of 0.1-0.5 mm.
When welding aluminum and its alloys are found the following problems:
1. The presence or the possible formation of Al2O3 refractory with a melting temperature of 2050 to 2070 ° C and a higher density than aluminum strongly impedes welding. To remove this oxide layer before welding surface is cleaned in depth by chemical or mechanical means. Formed in the process of welding oxide layer is removed by the use of fluxes that provide its dissolution or disintegration. Flux is the basis of chloride and fluoride compounds of alkali elements. In TIG welding oxide is removed by cathode sputtering by simply welding is done with alternating current.
2. At high temperatures dramatically reduces the strength of the aluminum, which can lead to destruction of the hard metal of the unrendered portion of the edges under the effect of the mass of the weld pool. The dimensions of the weld pool is difficult to control, as by heating the aluminum virtually does not change its color.
3. Aluminum has a higher coefficient of linear expansion and small elasticity, which increases the tendency to warping. Therefore welded must be firmly with accessories.
4. The liquid aluminum dissolves large quantities of hydrogen, which is difficult to removed by rapid solidification of the weld pool. As a result, porosity occurs, which results in a decrease in the strength and ductility of the weld metal. The porosity can be avoided by applying the pre-heated to 150-200 ° C, particularly in the welding of material with a large thickness. This leads to a delay in crystallization of the metal and the gases easy access to the surface of the weld pool. Most prone to the formation of pores have aluminum-magnesium alloys.
5. Metal seam is prone to cracking due to its wholesale crystal structure and large voltages obtained from large linear shrinkage crystallization - 1,7%.
Aluminum and its alloys are welded well with all methods of welding. By far the greatest application have manual and mechanized welding in inert gases.