In order to obtain the pressure vessel of further sound durability and stability under high temperature, high pressure and hydrogenous environment, laser welding application to low alloy 2.25Cr-1Mo steel has been tried in this paper. The mechanical phenomenon of thermal elastoplastic behavior of laser welded joint has been characterized by means of two dimensional thermal elastoplastic Finite Element(FE) analysis, and the strength of welded joints has been evaluated through the mechanical tests(hardness, low thermal toughness, bending and tensile). Moreover, mechanical features in welds by Shielded Manual Arc Welding, Flux Cored Arc Welding and CO2 Laser Welding process have been investigated and compared using the result of numerical analysis and mechanical tests. The results of residual stress and hardness analyses regarding each welding method showed that CO2 laser had slightly higher value than SMAW, FCAW, however, its difference was minute. Charpy impact test on specimens indicated that the impact absorbing energy of CO2 laser was more than five times as large as others. It was observed that all specimens in both tensile test at room temperature and bending test, were fractured in the base metal regardless of welding method. On the other hand, all specimens of tensile test at high temperature(700°C, 750°C,) fractured in heat affected zone and each rupture load value was similar except a slightly higher value for CO2 laser welding.
Therefore, it was demonstrated that laser welding process for manufacturing pressure vessel of low alloy 2.25Cr-1Mo steel is more advantageous as compared with present used SMAW and FCAW welding in all their aspects of mechanical characteristics. Moreover, we could confirm the possibilities of replacing arc welding such as SMAW, FCAW with laser welding for this 2.25Cr-1Mo steel.
