超声振动对304不锈钢窄间隙TIG焊接接头组织和力学性能的影响

Effect of ultrasonic vibration on microstructure and mechanical properties of 304 stainless steel narrow gap TIG welded joint

针对304不锈钢窄间隙TIG(非熔化极惰性气体保护电弧焊)焊接焊缝晶粒粗大、接头拉伸性能较差等问题,采用将超声振动头施加在试板,在TIG焊接过程引入超声振动的方法对其进行焊接,研究了焊接接头的组织和力学性能。结果表明:引入超声振动后,在热力学和动力学综合作用下,焊缝熔深增加,焊缝区柱状晶向等轴晶转变速率提高,等轴晶占比增多,晶粒细化;与常规TIG相比,引入超声振动后改善了304不锈钢窄间隙焊接接头的焊缝组织,提高了其力学性能,焊缝区的硬度明显提高,接近于母材,焊接接头的抗拉强度和屈服强度也均高于常规TIG焊接接头,伸长率也得到提高;当超声振幅为40μm时,焊接接头的抗拉强度最高,为674 MPa,屈服强度也较高,为376 MPa,断后伸长率为25%。

In view of the problems of coarse grain size and poor tensile properties of 304 stainless steel narrow gap TIG(tungsten inert gas welding)welded joint,the ultrasonic vibration head was applied to the test plate,and the ultrasonic vibration was introduced into the TIG welding process to weld it.Microstructure and mechanical properties of the welded joint were studied.The results show that after the introduction of ultrasonic vibration,under the combined effect of thermodynamics and dynamics,the weld penetration increases,the transformation rate of columnar crystal to equiaxed crystal in the weld zone increases,the proportion of equiaxed crystal increases,and the grain is refined.Compared with conventional TIG,the introduction of ultrasonic vibration improves the weld microstructure of the 304 stainless steel narrow gap welded joint,improves its mechanical properties,significantly improves the hardness of the weld zone,close to the base metal,and the tensile strength and yield strength of the welded joint are also higher than that of conventional TIG welded joint,and the elongation is also improved.When the ultrasonic amplitude is 40μm,the tensile strength of the welded joint is the highest of 674 MPa,the yield strength is 376 MPa,and the elongation is 25%.