特厚钢板辊式淬火过程厚向温降规律研究

Thickness temperature drop regularity during roller quenching process for ultra-heavy steel plate

摘要:

为针对特厚钢板厚向淬火冷速和冷却均匀性研究提供理论算法和实验数据,利用研发的辊式淬火装置及多通道温度记录仪,测试了160 mm、220 mm、300 mm钢板淬火温降曲线,采用有限元、最优化等方法建立三维反传热导热模型和热流密度计算模型,分析特厚钢板淬火厚向温度梯度、热流密度和冷速分布规律.结果表明:计算获得的温降曲线与实测值吻合良好,偏差小于4 %.高强度冷却可使钢板厚向形成较大温度梯度,随后适当减小冷却强度,可提高壁面过热度并维持厚向较大温度梯度,对特厚钢板心部~1/4H厚度区间温降有利.热流密度和温度梯度的耦合作用,共同影响钢板淬火温度场.随着壁面过热度的变化,220 mm和300 mm钢板厚向温降曲线出现“平台”和“反向温升”现象.“返温”现象一方面与钢板表面热流密度改变有关,另一方面与钢板厚向因温度梯度变化引起的MHF点（临界热流密度）位置改变有关.当钢板上下表面水流密度比分别为1∶1.25（0.8 MPa）和1∶1.4（0.4 MPa）时,能够实现上下表面基本对称冷却.

Abstract:

In order to provide theoretical methods and experimental data for the research of quenching cooling rate and cooling uniformity of ultra-heavy steel plate, the quenching temperature drop curves of 160 mm, 220 mm, and 300 mm ultra-heavy steel plate were obtained by roller quenching machine and multichannel temperature recorder in this study. A three-dimensional inverse heat transfer model and a heat flux calculation model were established by finite element method and optimization method, and the distribution regularities of temperature gradient, heat flux, and cooling rate were analyzed. Results indicate that the calculated temperature drop curves agreed well with the measured value, and the deviation was less than 4%. High-intensity cooling allowed the steel sheet to form a large temperature gradient. Subsequent reduction of the cooling intensity could improve the wall superheat and maintain the thicker temperature gradient, which was beneficial to the temperature drop of the core to 1/4H. The coupling effect of heat flux and temperature gradient had influences on plate quenching temperature field. “Platform” and “reheating” appeared in temperature drop curves for 220mm and 300mm plate as wall superheat changed. The “reheating” was related to the heat flux change on the plate surface and the position change of MHF point (critical heat flux) caused by temperature gradient change in the thickness direction of steel plate. When ratio of the upper and lower plate surface flow density were 1∶1.25 (0.8 MPa) and 1∶1.4 (0.4 MPa) respectively, symmetrical cooling was realized.