Microstructural investigation of MIG-brazed 304L stainless steel joints

Abstract

In this paper, austenitic 304L stainless steel plates having 1.0mm thickness were joined by copper-based CuAl8 wire in gas metal arc brazing technique with 100% Ar gas as a protective atmosphere. Specimens were prepared in butt and overlap joint positions. The metal inert gas (MIG) brazing operations were done with seven different arc voltages and weld currents as 40, 45, 50, 55, 60, 65 and 70 A. CuAl8 wire composed largely of copper serves as the filler metal was used. Owing to the low fusion temperature of the filler metal (900−1,100 ◦C), no fusion of the base metal takes place in MIG-brazing. The 1,500 ◦C fusion temperature of the base metal was not reached. A solid joint between the workpieces was brought about by diffusion. Having accomplished the brazing operations, micro and macrostructures of joints were investigated by optical microscope and scanning electron microscope (SEM) in order to see the joinability of stainless steels by gas metal arc brazing technique.