스테인레스강 SS420의 입계예민화에 의한 피트 부식

최병학; 이범규; 장현수; 박찬성; 김진표; 박남규; 김청인; 김보미; Byung Hak Choe; Bum Gyu Lee; Hyeon Su Jang; Chan Sung Park; Jin Pyo Kim; Nam Gyu Park; Cheong In Kim; Bo Mi Kim

Korean Journal of Materials Research, Vol.27, No.8, 431-437, August, 2017

DOI10.3740/MRSK.2017.27.8.431 Export Citation

스테인레스강 SS420의 입계예민화에 의한 피트 부식

Pit Corrosion of SS420 Stainless Steel by Grain Boundary Sensitization

최병학^†, 이범규, 장현수, 박찬성¹, 김진표¹, 박남규¹, 김청인², 김보미³

강릉원주대학교 신소재금속공학과
¹국립과학수사연구원
²씨알에이파이핑코리아㈜
³한국멕케이용접㈜

Byung Hak Choe^†, Bum Gyu Lee, Hyeon Su Jang, Chan Sung Park¹, Jin Pyo Kim¹, Nam Gyu Park¹, Cheong In Kim², and Bo Mi Kim³

Department of Advanced Metal & Materials Science Engineering, Gangneung-Wonju National Univ., Gangneung 26403, Republic of Korea
¹Forensic Engineering Dept., National Forensic Service, Wonju 26460, Republic of Korea
²CRA Piping Korea, Wonju 26460, Republic of Korea
³HMW Co., Ltd, Pohang 37866, Republic of Korea

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This study investigated the surface pit corrosion of SS420J2 stainless steel accompanied by intergranular crack. To reveal the causes of surface pits and cracks, OM, SEM, and TEM analyses of the microstructures of the utilized SS420J2 were performed, as was simulated heat treatment. The intergranular cracks were found to have been induced by a grain boundary carbide of (Cr,Fe)23C6, which was identified by SEM/EDS and TEM diffraction analyses. The mechanism of grain boundary sensitization occurred at the position of the carbide, followed by its occurrence at the Cr depleted zone. The grain boundary carbide of (Cr,Fe)23C6 type precipitated during air cooling condition after a 1038 °C solid solution treatment. The carbide precipitate formation also accelerated at the band structure formed by cold working. Therefore, using manufacturing processes of cooling and cold working, it is difficult to protect SS420J2 stainless steel against surface pit corrosion. Several counter plans to fight pit corrosion by sensitization were suggested, involving alloying and manufacturing processes.

Keywords:stainless steel;pit;intergranular crack;grain boundary sensitization;carbide precipitation

[References]

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[1] AK Steel Corporation, Product Data Sheet of 420 Stainless Steel, 420-S- 08-01-07 (2007).

[2] Barlow LD, Toit MD, J. Mater. Eng. Performance, 21, 1327 (2012)

[3] Garzon CM, Toro A, Tschiptschin AP, Trans. Indian Inst. Met., 55, 255 (2003)

[4] Teraoka S, Fukuda M, Kobayashi M, Takahashi A, Takemoto M, Nippon Still Technical Rep., 99, 39 (2010)

[5] Lopez D, Congote JP, Toro A, Tschiptschin AP, Wear, 259, 118 (2005)

[6] Toro A. Sinatora A, Tanaka DK, Tschiptschin AP, Wear, 251, 1257 (2001)

[7] Mesa DH, Toro A, Sinatora A, Tschiptschin AP, Wear, 255, 139 (2003)

[8] Stickler R, Vinckier A, Trans. ASM, 54, 362 (1961)

[9] Stawstrom C, Hillert M, J. Iron Steel Inst., 207, 77 (1969)

[10] Tedmon CS, Vermilyea DA, Rosolowski JH, J.Electrochemical Soc., 118, 192 (1971)

[11] Aydogdu GH, Aydinol MK, Corrosion Sci., 48, 3565 (2006)

[12] Joshi A, Stein DF, Corrosion, 28, 321 (1972)

[13] Hebsleb G, Werkst Korros., 33, 334 (1982)

[14] Truman JE, Proc. UK Corrosion, 87, 111 (1987)