A Study on the Heat Transfer Characteristics of Steel Plate in the Matrix Laminar Cooling Process.

Jing Xu,Xin He,Xiangjun Bao,Guang Chen,Qingyue Duan

doi:10.3390/ma14195680

Abstract

Accurate prediction and control of the steel plate temperature in the laminar cooling process are very challenging. In this research, an experimental platform was built to measure the heat transfer characteristics of the steel plate in the process of matrix laminar spray cooling when the steel plate is one millimeter away from the upper surface. The “buried couple method” was used, including the cooling temperature and cooling rate. Then, the temperature and the integrated heat transfer coefficient at the steel plate surface were calculated by the time-sequential function method (TSFM). The obtained results show that the fast cooling stage under the water cooling condition occurred in the first 1.5 s, and the measuring point temperature decreased by 8%. The “re-reddening” phenomenon of the steel plate appeared with time, and the measuring point temperature increased by 37%. Second, the maximum calculated difference between the surface temperature and the measuring point temperature was 0.75 °C, and the integrated heat transfer coefficient conformed to the periodic boundary features. The comprehensive convective heat transfer coefficient on the surface was in agreement with the periodic boundary characteristics, and its value exhibited oscillatory attenuation with the cooling process, and the oscillatory peak period was about 6 seconds. Two methods, sequential function method (SFM) and finite difference method (FDM), were used to verify the correctness of TSFM.

Highlights

Temperature control in the plate cooling process has always been very complex
From 12.5 to 77 s, the steel plate ran on the moving roller table, and the nozzle sprayed cooling water for laminar cooling
The temperature dropped from 793.2 to 730 ◦ C, with a drop ratio of 8%, and the cooling rate decreased from −0.9 to −34 ◦ C/s, with a drop ratio of 36%

Summary

Introduction

Temperature control in the plate cooling process has always been very complex. It is related to the cooling medium’s flow rate, velocity, pressure, and other process parameters and the specific heat transfer mechanism, such as phase change heat transfer, convection heat transfer, radiation heat transfer, and heat transfer conduction. By controlling the cooling temperature and cooling rate, the transformation process of austenite grains and the mechanical properties of steel can be improved [1]. Liu et al [2] first adopted numerical simulation using COMSOL software to calculate the temperature field of the plate in the laminar cooling process. Holes were drilled at different positions along the slab thickness direction, and the temperature curve of the slab in the cooling process was measured by using the “buried couple method”

Methods

Results

Conclusion