补焊对5754铝合金焊接接头组织和性能的影响

Influence of Repair Welding on Microstructure and Properties of Welded 5754 Aluminum Alloy Joint

气体绝缘输电线路的外壳需具有良好的焊接质量,如有焊接缺陷,必须补焊修复,但这可能影响焊接接头的性能。为揭示焊缝修补对焊接接头性能的影响,对可用于制作气体绝缘输电线路外壳的尺寸为10 mm×125 mm×500 mm的5754铝合金试板进行了1~3次的补焊试验,检测了未补焊和补焊的焊接接头的显微组织和力学性能。结果表明:未补焊和补焊1、2、3次的接头热影响区均发生了再结晶,焊缝区均为胞状树枝晶,补焊的接头晶粒比未补焊的接头粗大,且随着补焊次数的增加,晶粒更为粗大。此外,补焊和未补焊的接头热影响区均发生软化,抗拉强度为母材的80%~85%,拉伸试样均断裂在热影响区。未补焊和补焊1次、2次的接头的抗拉强度高于退火态母材的抗拉强度,但硬度相差不大;补焊3次的接头硬度最低。未补焊和补焊的接头的热影响区硬度最低。

Shell of gas insulated transmission line needs to possess excellent welding quality,and,if exhibited weld defect,must be restored by a repair welding which,however,is likely to affect performance of the welded joint.To reveal the effect of repair welding on performance of welded joint,the tests for repair welding one to three times were carried out with 5754 aluminum alloy plates measuring 10 mm by 125 mm by 500 mm which is adaptable to gas insulated transmission line shell.The microstructure and mechanical properties of the welded joint not undergoing and undergoing repair welding were checked.The results showed that recrystallization occurred in the heat affected zone of welded joints not repaired and repaired;the weld zones all offered cellular dendrite;grains of the repaired joints were coarser than that of the joints not repaired,and as the number of repair welding increased the grains became even coarser.In addition,the welded joints repaired and not repaired all showed softening in the heat affected zone,and tensile strength is 80%to 85%that of the base metal,the tensile specimens all fractured in the heat affected zone.The tensile strength of the joints not repaired or repaired one and two times was higher than that of the base material as annealed,but their hardness was less different.The joint repaired three times developed the minimum hardness.Hardness in the heat affected zone of the joints not repaired and repaired all was the lowest.