Microstructure and mechanical properties of Invar36 alloy joints using keyhole TIG welding
Xuan Yang, Jin Yang, Hongbing Liu, Jingyu Deng, Yuhua Wang
Abstract
Single-pass keyhole TIG welding (K-TIG) was used to weld 10-mm-thick Invar36 alloy plates without filler metal and groove preparation. The effects of joint gap, welding current, welding speed and arc length on the weld appearance, microstructure and mechanical properties were investigated. No phase transformation occurred in the weld where only austenite (γ-(Fe, Ni)) was formed, while the grain structure changed significantly. The maximum tensile strength of K-TIG weld was 440.7 MPa reaching 99.9% of the base metal and the maximum elongation was 31.5%. The microhardness in the weld zone was slightly lower than that of the base metal. The results suggested that K-TIG welding was a very promising method for the joining of middle-thick Invar36 alloy plates.