Analysis on refinement of columnary γ grain by phosphorus in continuously cast 0.1 mass% carbon steel
Analysis on refinement of columnary γ grain by phosphorus in continuously cast 0.1 mass% carbon steel
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DOI：
10.2355/isijinternational.44.547
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发表时间：
2004-01-01
影响因子：
1.8
通讯作者：
Nagai, K
中科院分区：
文献类型：
--
作者：
Yoshida, N;Umezawa, O;Nagai, K
Based on a grain growth model, this paper discusses the gamma grain refinement by phosphorus (P) in as cast 0.1 mass% C slabs. Two important factors, the starting temperature of the rapid grain growth (T-rg) and the grain growth rate, are especially focused in the model. Local Equilibrium Mapping (LEM), an analytical method with local equilibrium calculations in the micro-segregation maps determined by EPMA, is carried out to evaluate the local transformation temperature and the gamma phase fraction. The LEM analysis shows that the micro-segregation of P extends the delta/gamma transformation temperature range to a lower temperature and retains the delta phase at a lower temperature. The Classical Grain Growth Model (CGM) based on a theory by Burke (1949) and Turnbull (1951) is derived, which assumes a normal grain growth with a parabolic law, The CGM successfully evaluates the gamma grain growth curve in the as cast 0.1 mass% carbon steels considering the rapid growth after the delta/gamma transformation and the change of the growth rate during cooling. The CGM analysis predicts the decrease of both T-rg and growth rate by the P addition. The decrease of T-rg was determined to be 160-170 K and agrees with the extension of the delta/gamma transformation temperature range evaluated by the LEM analysis. Hence, the grain growth curves can be predicted by considering the extension of the delta/gamma transformation temperature range clue to the P addition and its micro-segregation.
