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원심주조법으로 제조된 10% Cr 내열강의 등온 변태 거동
김주업 ( J E Kim ),이종훈 ( J H Lee ),김두현 ( D H Kim ),유위도 ( W D Yoo ),이재현 ( J H Lee ) 한국열처리공학회 2014 熱處理工學會誌 Vol.27 No.2
Isothermal transformation behavior of a 10% Cr heat resistant steel fabricated by centrifugal casting process was investigated. Normalized specimen at 1100oC for 1 hour was isothermally annealed at temperature range between 600oC and 700oC with various time. The annealed specimen had eutectoid structure which was generated along austenitic grain boundary during isothermal annealing. Areal fraction of eutectoid structure increased up to 25% after holding at 700oC for 20 hours. It was observed that austenitic matrix was transformed to ferrite structure and fine M23C6 carbides with increase of annealing time. Time-temperature-transformation diagram of the centrifugally cast 10% Cr steel with 0.18 wt% C was plotted based on the results of isothermal transformation behavior.
SAF 2205 듀플렉스 스테인레스강의 미세조직 및 기계적 특성에 미치는 냉각속도의 영향
오영주 ( Y J Oh ),양원존 ( W J Yang ),이종훈 ( J H Lee ),김두현 ( D H Kim ),유위도 ( W D Yoo ),이재현 ( J H Lee ) 한국열처리공학회 2013 熱處理工學會誌 Vol.26 No.1
Abstract Duplex stainless steel, which is a kind of stainless steel with a mixed mixrd microstructure of about equal proportions of austenite and ferrite, is generally known as a unique material with excellent corrosion resistance and high strength. However, toughness, strength, and corrosion resistance of the steel could be reduced due to precipitation of topologically closed packed phases such as sigma phase during cooling. In case of large forged products, they have strong possibility that б-phase precipitates due to difference of cooling rate between surface and inner of the products. Investigation on sigma phase precipitation behavior of duplex stainless steel with change of cooling rate was carried out in this study. Forged SAF 2205 duplex stainless steel was used as spec-imens to examine the cooling rate effect. Dissolution behavior of sigma phase was also discussed through reso-lution test of duplex stainless steel containing lots of sigma phase. Experimental results revealed that impact energy was very sensitive to precipitation of small amount sigma phase. However, sigma phase could be removed by short term resolution treatment and impact resistance of the duplex stainless steel was restored. (Received November 9, 2012; Revised December 22, 2012; Accepted January 7, 2013)