Effect of Heat Input on the Bending Crack and Microstructure of an Austenitic Stainless Steel Overlay Weldment by Flux Cored Arc Welding

摘要

This study investigated the effect of heat input in overlay welding using stainless steel FCW on the dilution ratio and characteristics of microstructural evolution, initiation and propagation of a bending crack in the overlay weldment. When the heat input was varied in the range of 3.2-19.8 kJ/cm by adjusting welding parameters such as current, voltage and speed, the dilution ratio was the highest in 7.9-9.9 kJ/cm with the lowest values of Cr_(eq) and Ni_(eq), for which the formation of martensite was predicted by the Schaeffler diagram, and its existence was confirmed by optical microscopy. In addition, the width of the transition zone was the largest in heat input of 7.9-9.9 kJ/ cm, and martensite was observed in the transition zone of the first weld layer of E309LT1-1 (welding material) and ASTM A516 Gr.70 (base metal). According to the bending test, cracks were observed in the specimens with heat input of 8.6-9.5 kJ/cm.