EFFECT OF SHIELDING GAS COMPOSITION ON WELD METAL (GMAW) PROPERTIES OF SA 516 GRADE 70 STEEL

摘要

SA 516 Grade 70 steel is one of the most popular grades used in the boiler and pressure vessel industry. Gas metal arc welding (GMAW) process is employed in this study. The GMAW produces smooth, neat, clean and spatter free welded surfaces which require little or no further cleaning. Plates of SA 516 Grade 70 of 20mm thickness were used in this study. Two sets of weld beads were produced each at two different shielding gas mixtures such as 80% Ar + 20% CO_2 and 85% Ar + 15% CO_2. One set of weld was subjected to post weld heat treatment (PWHT) while the other was maintained in the as-welded condition. Mechanical properties of the weld joint such as tensile strength, impact strength and hardness were evaluated and also compared with PWHT weld. Microstructure evaluation of the weld as well as fractography of the fracture surface was carried out.