Investigation on the Microstructure and Mechanical Properties of ASTM A131 Steel Manufactured by Different Welding Methods

Welding is an indispensable manufacturing process in the shipbuilding industry. The fierce competition involved often necessitates a cost-effective and reliable welding method. In this study, the weldabilities, microstructures and some mechanical properties of ASTM A131 (Grade A) steel joints fabrication by submerged arc welding (SAW), metal active gas (MAG) welding and plasma arc welding (PAW) have been investigated. The microstructures of the welds were examined by optical microscopy. The mechanical properties of the joints were determined by microhardness measurements, tensile and impact tests. The results showed that tensile strength of the joints reached a tensile strength of up to 462 MPa. The locations of the fractures were always adjacent to the base metal. The Charpy impact energy of the weld metal reached a value of 72.5 J, which was 25 % higher than that of the base metal at 57.7 J. A relatively high hardness of 221 HV was obtained in the PAW method compared to 179 HV in the base metal.