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

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. © 2019, Editorial Board of Journal of Harbin Institute of Technology. All right reserved.