STUDY OF PRIMARY MACHINING TYPE INFLUENCE ON THE QUALITY OF WELDED LIGHTWEIGHT ALUMINUM ALLOY STRUCTURES

The article presents the study results of welded joints from the aluminum alloy of Al-Fe-Si system. The purpose of welding is to obtain aircraft parts. The challenge of joining light-weight skin-type parts consists in frequent defects such as flatness deviations and joint surface geometry changes caused by spot resistance welding. As the adjustment of welding mode and conditions has not yielded favorable results a decision was made to study the influence of previous operations of the technological process. The PURPOSE of this work is to study the influence of the types of primary machining of aluminum alloy sheet parts on the quality of welded joints obtained by spot resistance welding. METHODS. The influence of the blank production method and sample sheet rolling direction at nesting on the quality of welded joints has been determined experimentally. RESULTS AND THEIR DISCUSSION. The best results after welding have been obtained on the parts made by chemical dimensional etching. After resistance welding of such samples with the thinning windows of 0.9 mm and 1.1 mm regardless of the sheet nesting direction the defects were not found. After resistance welding on parts with the thinning windows of 0.68 - 0.75 mm, 0.88-0.96 performed by the mechanical processing method regardless of the sheet nesting direction the defects in the form of bucklings were identified. The parts with the increased thickness of 1.15 mm do not feature any surface deviations from flatness after welding. CONCLUSIONS. It has been determined that the appearance of geometry integrity defects after spot resistance welding on samples does not depend on the direction of sheet nesting but depends on the type of machining and the thickness of thinning windows. The residual deformation after machining can be reduced by decreasing the depth of thinning, i.e. increasing the part thickness in the thinning windows to the maximum allowable value of 1.15 mm. This eliminates the possibility of defects after welding in the form of surface crowns.

resistance welding, aluminum alloy, spot welding defects, chemical etching, milling

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