Microstructural, mechanical and corrosion properties of dissimilar joint between AISI A321 stainless steel and ASTM A537CL1 structural steel produced by GTAW process

摘要

In this research, the microstructural, mechanical and corrosion properties of the dissimilar joint of ASTM A537CL1 to AISI A321 steels produced by GTAW process were studied. The welding process was done with ER308L filler metal without pre and post weld heat treatment. The scanning electron microscope and optical microscope were used to study the microstructure and fracture surface of the welded samples. Also, the mechanical behavior of the joint was evaluated by impact, tensile, bending and microhardness tests. The results illustrated that the microstructure of the weld metal was austenite with dendritic structure contained skeletal and lathy ferrite. In tension tests, all weldments failed from A537 base metal. The results of impact test indicated that all specimens exhibit ductile fracture and indicated high impact energy of about 205 J. In fine grain HAZ of A537 steel, because of formation of fine equiaxed grains due to the allotropic transformation, high microhardness was seen. While, in coarse grain HAZ, due to the formation of bigger grains, carbon migration and decreasing in the amount of pearlite phase, the microhardness slightly decreased. The exsistence of chromium in microstructure improved the corrosion resistance and the weld metal indicated acceptable corrosion resistance as compared with both base metals.