2021 Volume 39 Issue 1 Pages 24-31
The weldability of cast iron depends on several factors such as the welding method, chemical composition of the filler material, and the presence or absence of preheating/post-weld heat treatment (PWHT). In the past, the authors of this study have proposed the utilization of mild steel and austenitic stainless-steel filler materials for cast iron. They advocated the use of welding methods such as shielded metal arc welding (SMAW) and gas metal arc welding (GMAW). However, these studies did not examine preheating or PWHT. There have been no studies to date on the effects of heat treatment on the metallographic structure and mechanical properties of welded joints obtained using mild steel and austenitic stainless-steel filler materials. The aim of this study is to investigate the effect of PWHT on joints obtained when mild steel filler material and austenitic stainless steel-filler material are used to join spheroidal graphite cast iron. For the welding method, SMAW and GMAW were applied as in the previous studies. After welding, each test piece was maintained at 850℃ for 1h and air-cooled. Subsequently, metallographic observation, hardness testing, and tensile tests were performed on the welded joint. For the test pieces with mild steel filler material, the ledeburite that appeared during welding decomposed, and the maximum hardness of the joint was significantly reduced. For the test piece with austenitic stainless-steel filler, ledeburite did not decompose and the maximum hardness of the joint did not decrease. In the tensile test, the tensile strength, 0.2% proof stress, and elongation increased. These results suggest that PWHT is effective in improving the tensile strength, proof stress, and elongation of the joint.
