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오스테나이트계 스테인레스강의 열간가공성에 미치는 Cu 의 영향
최점용,진원 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.1
The effect of Cu on the hot workability of austenitic stainless steel has been investigated by performing tensile tests and examination by scanning electron microscopy and Auger electron spectroscopy. Reduction of area decreased linearly with increasing Cu contents at deformation temperature above 1100℃. But, at the deformation temperature below 1100℃, the effect of Cu on reduction of area changed drastically at about 3.2% Cu. At lower Cu contents, reduction of area decreased in the same manner with that observed above 1100℃. However, as Cu contents exceeded about 3.2%, reduction of area rapidly decreased with increasing Cu contents. Fracture mode changed from ductile rupture to intergranular decohesion as Cu contents increased in the ductility trough. The occurrence of embrittlement would be attributed to the segregation of Cu and S at austenite grain boundary.
역변태 Fe-Cr-Mn계 변태유기소성 스테인레스강의 결정립 크기에 따른 상온인장변형 거동
최점용,박경태 한국소성∙가공학회 2023 소성가공 : 한국소성가공학회지 Vol.32 No.2
A wide range of grain size was achieved in a Fe-Cr-Mn austenitic stainless steel (STS) by cold rolling and reversion annealing. The tensile characteristics of the STS were analyzed in terms of the dependence of strain induced martensitic (SIM) transformation on the grain size. In the ultrafine grain regime, the steel showed a high yield strength over 1 GPa, a discontinuous yielding, and a prolonged yield point elongation followed by considerable strain hardening. By increasing the grain size, the discontinuous yielding diminished and the yield point elongation decreased. The microstructural examination revealed that these tensile characteristics are closely related to the suppression of SIM transformation with decreasing the grain size. Especially, the prolonged yield point elongation of the ultrafine grained STS was found to be associated with development of unidirectional martensite bands. Based on the microstructural examination of the deformed microstructures, the rationalization of the grain size dependence of SIM transformation was suggested.
신선가공시 오스테나이트계 스테인리스강의 미세조직 변화 및 가공경화 거동
최점용,진원 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.3
The strain induced α′-martensite formation and the strain hardening behavior of metastable austenitic stainless steel during cold drawing have been investigated. The strain induced α′-martensite nucleates mainly at the intersection of the mechanical twins rather than ε-martensite. It could be explained by the increase of stacking fault energy which arises from the heat generated during high speed drawing and, for AISI 304/Cu, the additional effect of Cu additions. The strain hardening behavior of austenitic stainless steel is strongly related to the microstructural evolution accompanied by strain induced α′-martensite. The work hardening rates of cold-drawn 304 increased with increasing interstitial element(C,N) contents which affect the strength of the strain induced α′-martensite.
냉간 압연에 따른 N 함유 저 Ni계 Duplex Stainless Steel의 변형거동
최점용(J. Y. Choi),황시우(S. W. Hwang),지정훈(J. H. Ji),김세라(S. R. Kim),박경태(K. -T. Park) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.5
The effects of nitrogen addition on the strain induced martensitic transformation (SIMT) behavior of duplex stainless steel (D-STS) with the low nickel content were examined in a wide range of strain by means of cold rolling. Nitrogen of 0.1,0.2 and 0.3 wt.% was added into Fe-20Cr-5Mn-0.2Ni D-STS (in wt.%) and cold rolling was conducted up to the effective strain of ~1.45 after annealing at 1100 C for 30 min. In the as-annealed state, the austenite fraction increased with increasing the N content. Regardless of the N content, the ferrite grain size was coarser than that of austenite. The stacking fault energy of austenite of the present D-STSs inferred by the element partitioning analysis was low enough so that SIM transformation is available. Accordingly, during cold rolling, SIMT occurred in austenite with a sequential manner of austenite → ε martensite → α’ martensite with increasing strain. By contrast, the deformed microstructure of ferrite was dominated by dislocation cells.