Tensile behavior and microstructure of AISI 304 stainless steel after heat treatment in sensitization area of 600-700 °C

AISI 304 stainless steel is used as a structural component of the LWR type power reactors. In the manufacture of structural component, the quality of SS 304 welded joints is determined by cooling process from the austenite to sensitization temperature. The purposes of this study was to determine tensile strength, hardness and microstructure of SS 304 in the sensitization area of 600-700 °C. The research method was testing of the chemical composition, tensile, hardness and microstructural properties referring to ASTM. The results show that the tensile strength of SS 304 after sensitization treatment at 600^oC (30-60 minutes) and 700 °C (30-90 minutes) was relatively the same and lower than samples without heat treatment while the sample treated at 600 °C (90 minutes) was relatively the same as the sample without heat treatment. The microstructure of SS 304 consists of δ-ferrite and austenite phases and chromium carbide precipitates. The quantity of precipitate at the grain boundaries decreases with increasing temperature and holding time. The hardness after sensitization treatment at 600-700 °C was relatively the same on the base metal, near the fracture and the fracture area. The most crack resistant was samples with treatment at 700 °C (90 minutes). (author)