以Ueshima的正六边形横断面枝晶模型为原型, 采用有限差分方法建立了钢凝固过程伴随δ/γ相变的两相区溶质微观偏析模型, 确立了在冷却速率为10 ℃/s非平衡凝固条件下钢的脆性温度区间, 研究分析了各溶质元素在该温度区内的偏析特点及对脆性温度区间ΔθB与热应变的影响规律, 定量计算了不同P, S含量下脆性温度区热应变随C含量的变化规律, 揭示了P, S含量的增加使连铸坯出现表面纵裂纹几率提高的机理.
The solidification of molten steel in continuous casting mold is a complicated nonequilibrium process with high cooling rate of 10—100 ℃/s. At such a cooling rate, the segregation of the solute elements such as C, Si, Mn, P and S in brittle temperature range (ΔθB) will vary with their initial contents and influence on the thermal strain significantly which could greatly increase the incidence of surface defects of strand. In this paper, a microsegregation model of solute elements in mushy zone with δ/γ transformation during solidification was established based on the regular hexagon transverse cross section of dendrite shape proposed by Ueshima by finite difference method under the non-equilibrium solidification condition at 10 ℃/s of cooling rate and the brittle temperaturerange ΔθB was determined. The distribution characteristics of solute elements and the effect of their segregations on ΔθB and thermal strin were nvestigatedTe results show that both P and S are the most serious segregation elements in final stage of solidification and affect on ΔθB sinificantly together with carbon content in molten steel. The mechanism that increasing contents of P and S may incrasthe probability of longitudinal surface crack for continuous casting strand was presented by calculatng the change law of thermal strain with carbn content under different of P and S contents.
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