Effect of High Temperature on the Strength of the Base Metal and the Weld Metal in a Welded Joint of Low-Carbon Steels

The strength properties of the base metal and the weld metal in welded joints of low-carbon 22K and 09G2S steels are studied before and after high-temperature action, i.e., heating to 1000°C and the subsequent multistage decrease in temperature to 23°C for 22K steel and annealing for 3.7 h at the test temperatures (750–1200°C) upon cooling to room temperature for 09G2S steel. The thermal action in the austenite region is found to decrease the conventional yield strength of the base metal in the welded joint of 22K steel by 8–23% at test temperatures of 23–300°C and to increase it by 11–51% at temperatures of 400–700°C. The weld metal in the welded joint of 22K steel has a higher strength compared to the base metal at temperatures 23–800°C both before and after thermal action. Isothermal holding increases the strength of the base metal in the welded joint of 09G2S steel and decreases the strength of the weld metal by a factor of two at 750°C; at 800–1200°C, the influence of isothermal holding on the strength of the weld metal is insignificant.