통합 검색 | Korea Science

냉간가공한 오스테나이트계 강재의 극저온 특성에 미치는 Ni 및 N의 영향 (The Effect of Nickel and Nitrogen on Cryogenic Properties of Austenitic Stainless Steel)

최진일;주기남;강영환
- 한국표면공학회지
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- 제37권1호
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- pp.64-70
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- 2004
Cryogenic characteristics of austenitic stainless steel based on 304 steel with nickel and nitrogen were investigated at room temperature and $-196^{\circ}C$. The alloys were fabricated by vacuum arc furnace and cold working after homogenization treatment. The addition of nickel and nitrogen decreased the stability of $\delta$-ferrite and induced the stability against the formation of martensite to result significantly in enhancing ductility at $-196^{\circ}C$. Nitrogen reduced Md temperature, which was beneficial to the tensile strength and elongation at $25^{\circ}C$ and -196$^{\circ}C$.
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페라이트계 스테인리스 판재 적용을 위한 세탁기 회전날개의 전산 해석기반 성형공정설계 (Simulation-based Stamping Process Design for a Pulsator Cover of a Washing Machine with Ferritic Stainless Steel Sheet)

김세호;김기풍
- 한국정밀공학회지
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- 제28권3호
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- pp.349-356
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- 2011
This paper replaces a conventional austenitic stainless steel sheet to a ferritic stainless steel for the cost reduction of a pulsator cover of a washing machine. However, ferritic stainless steel has poor formability in comparison with austenitic one. The low formability of ferritic steel results in problems during stamping such as fracture, wrinkling, shape inaccuracy and so on. Design modification of the stamping tool is carried out with the aid of the finite element analysis for multistage stamping process of the pulsator cover. The simulation results show that fracture occurs on top of the product while wrinkles are generated by the excess metal near the wing part. Modification of the initial stamping die is performed to improve metal flow and to eliminate problems during the stamping process. Simulation with the modified design fully demonstrates that safe forming is possible without inferiorities.
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오스테나이트계 스테인리스강 용접부의 금속학적 현상에 관한 연구(2) - STS 304 용접부 조직특성 및 고온균열 감수성에 미치는 질소의 영향 - (A Study of Weld Fusion Zone Phenomena in Austenitic Stainless Steels(2) - Effects of Nitrogen on Microstructural Evolution and Hot Cracking Susceptibility GTA Welds in STS 304 -)

이종섭;김숙환
- Journal of Welding and Joining
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- 제18권1호
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- pp.59-69
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- 2000
The purpose of the present study was to investigate weld metallurgical phenomena such as primary solidification mode, microstructural evolution and hot cracking susceptibility in nitrogen-bearing austenitic stainless steel GTA welds. Eight experimental heats varying nitrogen content from 0.007 to 0.23 wt.% were used in this study. Autogenous GTA welding was performed on weld coupons and the primary solidification mode and their microstructural characteristics were investigated from the fusion welds. Varestraint test was employed to evaluate the solidification cracking susceptibility of the heats and TCL(Total Crack Length) was used as cracking susceptibility index. The solidification mode shifted from primary ferrite to primary austenite with an increase in nitrogen content. Retained delta ferrite exhibited a variety of morphology as nitrogen content varied. The weld fusion zone exhibited duplex structure(austenite+ferrite) at nitrogen contents less than 0.10 wt.% but fully austenitic structure at nitrogen contents more than 0.20 wt.%. The weld fusion zone in alloys with about 0.15 wt.% nitrogen experienced primary austenite + primary ferrite solidification (mode AF) and contained delta ferrite less than 1% at room temperature. Regarding to solidification cracking susceptibility, the welds with fully austenitic structure exhibited high cracking susceptibility while those with duplex structure low susceptibility. The cracking susceptibility increased slowly with an increase in nitrogen content up to 0.20 wt.% but sharply as nitrogen content exceeded 0.20 wt.%, which was attributed to solidification mode shift fro primary ferrite to primary austenite single phase solidification.
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