듀플렉스 스테인리스강(ASTM A240 UNS S31803)의 FCA 용접 후 열처리가 용접부 특성에 미치는 영향 (The Effect of PWHT on the Characteristics of Duplex Stainless Steel (ASTM A240 UNS S31803) Weld Metals made with FCAW)

서지정보

· 발행기관 : 대한용접접합학회
· 수록지 정보 : 대한용접접합학회지 / 35권 / 6호 / 89 ~ 95페이지
· 저자명 : 현준혁, 신태우, 장복수, 김상호, 고진현

초록

The effect of post-weld heat treatment(PWHT) on microstructure, mechanical properties and pitting corrosion resistance of UNS S31803, duplex stainless steel(DSS), weld metals was investigated. Three heat inputs of 7.6, 12.5, 18.0kJ/cm were employed to make joints of DSS with E2209T1-1/4 wire and PWHT was conducted in three temperatures of 1070, 1100, 1130℃. Microstructure in weld metals after PWHT consisted of allotriomorphic rather than needle-shaped austenite. Secondary austenite was scarcely formed and intermetallic compounds were not formed. Ferrite content was increased with increasing PWHT temperatures because δ-ferrite was stable phase and ferrite can not be sufficiently transformed to austenite due to rapid cooling. The difference of Cr, Mo and Ni contents between δ-ferrite and austenite after PWHT increased compared to that before PWHT. Hardness of weld metals became lower than that of base metal after PWHT.
Also, hardness of weld metals was increased while impact absorbed energy was decreased with increasing PWHT temperature because of increase of δ-ferrite content. In pitting corrosion test, the critical pitting corrosion temperature(CPT) after PWHT increased by approximately 10℃, and CPT of weld metals was between 35 and 40℃. Heat-treated specimens in 1070℃ was corroded in base metal because ferrite content of base metal was quite high over 60%.

영어초록

The effect of post-weld heat treatment(PWHT) on microstructure, mechanical properties and pitting corrosion resistance of UNS S31803, duplex stainless steel(DSS), weld metals was investigated. Three heat inputs of 7.6, 12.5, 18.0kJ/cm were employed to make joints of DSS with E2209T1-1/4 wire and PWHT was conducted in three temperatures of 1070, 1100, 1130℃. Microstructure in weld metals after PWHT consisted of allotriomorphic rather than needle-shaped austenite. Secondary austenite was scarcely formed and intermetallic compounds were not formed. Ferrite content was increased with increasing PWHT temperatures because δ-ferrite was stable phase and ferrite can not be sufficiently transformed to austenite due to rapid cooling. The difference of Cr, Mo and Ni contents between δ-ferrite and austenite after PWHT increased compared to that before PWHT. Hardness of weld metals became lower than that of base metal after PWHT.
Also, hardness of weld metals was increased while impact absorbed energy was decreased with increasing PWHT temperature because of increase of δ-ferrite content. In pitting corrosion test, the critical pitting corrosion temperature(CPT) after PWHT increased by approximately 10℃, and CPT of weld metals was between 35 and 40℃. Heat-treated specimens in 1070℃ was corroded in base metal because ferrite content of base metal was quite high over 60%.

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