The issue of the upper limit on base metal thickness after solution treatment in welding qualification

The upper limit for the base metal thickness after solution treatment in welding qualification is determined based on the size of the heat-affected zone (HAZ) during the welding process. The heat-affected zone refers to the area that is heated during welding to a temperature above the grain boundary recrystallization temperature but does not melt completely. During stainless steel welding, issues such as intergranular corrosion and nitrogen precipitation may occur in the heat-affected zone; therefore, solution treatment is required to eliminate these adverse effects. To ensure that solution treatment can effectively eliminate problems in the heat-affected zone, the evaluation criteria specify a minimum solution treatment time and temperature. In 40mm thick stainless steel sheets, due to the large size of the heat-affected zone generated during welding, a longer solution treatment time is required to ensure that recrystallization of the grain boundaries in the heat-affected zone is completed. Therefore, in 40mm stainless steel sheets, the upper limit for the base material thickness after solution treatment has been extended to 200mm. For thinner base materials, such as stainless steel sheets with a thickness of 5–44 mm, the size of the heat-affected zone is relatively small, allowing grain boundary recrystallization to occur within a shorter solubilization time. Therefore, according to Evaluation Standard Table 10, the upper limit for the base material thickness after solution treatment is 44 mm. This range is determined to ensure that the base material after welding meets the specified performance and quality requirements. .

Table 10 shows the normalizing treatment for carbon steel and low-alloy steel; the solution treatment of stainless steel is not considered normalizing