特殊钢大方坯动态轻压下压下量模型研究

Reduction amount model for dynamic soft reduction in bloom continuous casting of special steels

根据拉坯方向上质量守恒推导出更加简单且易于数值模拟计算的特殊钢大方坯连铸压下量计算模型Ri=2/37＊31/2fSC,i-fSC,i-1）Th/η,或者Ri=-2△TC,iTh/37＊31/2T1-Tsηi.式中,Ri为单个压下辊压下量,（fSC,i-fSC,i-1）为中心固相率增量,Th为铸坯厚度,η_i为压下效率,△TC,i为铸坯中心温度增量,Ts和T1分别为固液相温度。建立了耦合压下量模型的大方坯凝固传热模型,并分析了钢种、断面尺寸、拉速、过热度和比水量对合理压下量的影响。结果表明,在拉坯方向上,由于凝固加速和压下效率减小,铸坯的压下量逐步增大;钢种、铸坯宽度、拉速、过热度和比水量对总压下量影响有限,但铸坯厚度对总压下量影响很大。大方坯厚度每增加30 mm,轻压下量增加1mm。

Based on overall mass balance in the casting direction, a theoretical model of reduction amount, suitable for any rectangular continuous casting products, was presented. The impact of arbitrary rectangular section, solidification contraction, thermal shrinking, deformation and temperature on reduction amount can well be described by the formula as Ri=2/37＊31/2fSC,i-fSC,i-1）Th/η,or Ri=-2△TC,iTh/37＊31/2T1-Tsηi .Where R1 is reduction amount,（fSC,i-fSC,i-1）is the center solid fraction increment, Th is the thickness of casting product, η is the reduction efficiency, △Tci is the center tempera- ture increment, Ts and T1 are the solidus and liquidus temperature, respectively. A finite difference numerical method of solving heat transfer and solidification was developed to calculate the reduction amount with consideration of different steel grades, section sizes, casting speeds, superheat and specific water flow. It was found that the soft reduction amount under each reduction roll should increase upon approaching the crater end due to the increased final solidification and de- creased reduction efficiency. The effect of carbon and alloy contents, bloom width, casting speed, superheat and specif- ic water flow on the effective total reduction amount is rather limited, while the bloom thickness influences the soft re- duction amount remarkably. The soft reduction amount increases by 1 mm as the bloom thickness increases by 30 mm.