铝合金双面双弧同步立焊工艺特征与接头组织性能分析

Analysis on Characteristics of Double-sided Synchronization Vertical Welding for Aluminum Alloy and Structure Property of Joint

采用双面双弧同步立焊工艺方法,对8 mm厚5083铝合金进行自熔试验,I形坡口一次熔透,焊缝成形美观。通过调节两侧电弧热量配比研究熔池成形规律,并从焊接接头的微观组织、力学性能分析其连接机理。研究结果表明,随着热输入的增加,双面双弧同步立焊热量加速集聚,熔深以三次幂函数的速度增大。双面双弧同步立焊接头轮廓呈'双曲线形',而相同热输入下的单面焊接头则呈'倒马鞍形'。总热输入一定的情况下,双面双弧接头正面熔宽随能量配比系数的增大而增大,反面熔宽随能量配比系数的增大而减小,中间熔宽基本不变,熔化面积随能量配比系数的增大先增大后减小;能量配比系数一定时,随着焊速的增大,接头熔宽和熔化面积均减小。母材组织为条带状纤维织构,热影响区发生静态回复与再结晶,变形组织消失,产生新晶粒,焊缝区主要由α-Al固溶体、β相(Al_8Mg_5)质点和骨骼状的Mg_2Si析出相组成。焊缝的抗拉强度随着能量配比系数的增大而减小,拉伸断裂形式为韧性断裂。热影响区出现软化现象,双弧交汇区硬度低于正面焊缝区。

8 mm thick 5083 aluminum alloy is penetrated fully without sloping and filler by double-sided synchronization vertical welding（DSSVW）. The welding heat input distribution of both sides, the microstructure and the mechanical properties of the welding joints are analyzed to show joining mechanism. Results indicate that the thermal input of DSSVW is acceleratedly accumulated and the penetration increases by the growth velocity of cubic function. The morphology of DSSVW is hyperbolic type, while the morphology of single side vertical welding（SSVW） with the same heat input is inverted saddle type. If the total heat input is certain, an increase in the energy distribution coefficient will cause an increase in front bead wide, a decrease in back bead wide of DSSVW process, while the intermediate weld wide is almost unchanged and the melting area first increases then decreases. The weld wide and fusion area both decrease with the increase in welding velocity when the energy distribution coefficient is determined. The microstructure of base metal is banding fiber texture. Static recovery or recrystallization occurs in heat-affected zone（HAZ） due to arc heating, so that deformed microstructure disappeared and recrystallization grain generates. The weld metal zone is constituted by a-Al solid solution, β phase（Al_8Mg_5） and skeleton shaped Mg_2 Si phase. The tensile strength decreases slightly with the increase in energy distribution coefficient, and the fracture mode is ductile fracture. The hardness of HAZ decreases and the hardness of the intersection region is lower than the front weld bead.