Hot forming of welded blanks of aluminum alloy sheets 1565 chM

Abstract

The details of forming in cold or heated position for welded blanks of alloy 1565chM with a thickness of 8,0 mm, performed by friction stir welding, are viewed. It is found that welded joints of alloy 1565chM with a thickness of 8,0 mm, obtained by friction stir welding have high strength properties together with sufficient toughness. Thus, bending angle of the joints is 165…170 °. The strength factor of the welded joint is 0.96 of the strength of the base metal. At the same time, the temporary resistance of the weld metal exceeds temporary resistance of both: base metal and the welded joint in its value. The 1565chM alloy joints, made by friction stir welding have good formability under cold deformation. This special feature of welded blanks made of 1565chM alloy sheets is explained by the presence of a fine-grained recrystallized structure in a stir zone, which is formed as a result of heat impact and force action of the working tool on the material to be welded. Welding modes providing specified mechanical properties of the joints were used for welding shells (blanks) of gas cylinders (liners). Manufacturing technique for such cylinders includes the following operations: welding of the shell, calibration of the shell, quality control of the weld on the shell, jumping into a hot mold for forming bottoms, welding of fittings and general tightness control. Experiments on forming liners bottoms due to the shell jumping into a heated to 450...500 °C mold have shown that there is an intensive weld metal runout due to differences in the strain capacity of the weld metal and the base metal. This behavior of the weld metal during hot forming can be explained by superductility of the weld metal owing to the presence of a recrystallized ultrafine-grained structure. It was found that starting from a temperature of 400 °C, the relative elongation of the weld metal significantly exceeds the elongation value of the base metal. In case of 450 °C, this difference reaches 72 %. For the weld of the 1565chM alloy, starting from the heating temperature of 540 °C, an abnormal grain growth occurs along the entire weld.