小型H型钢超快冷“内并外扩”的有限元模拟

Finite element simulation of"out-of-square"during ultra-fast cooling of small-size H-beam steel

超快速冷却对于H型钢的组织优化和性能提升具有重要的意义,冷却后的"内并外扩"是影响产品质量和生产稳定性的重要因素,也限制了超快速冷却工艺的推广和应用,在H型钢冷却过程中,换热系数是关键参数。为了研究换热系数对小型H型钢超快冷条件下"内并外扩"的影响,采用有限元模拟计算软件Abaqus建立了轧后冷却二维热力耦合模拟计算模型。考虑翼缘、腹板、R角处不同部位的冷却特点,将H型钢断面划分16个特定冷却特征区域并分别为其指定不同的换热系数,制定3个不同的冷却方案,分别进行模拟计算,得出温度场、应力场和上下翼缘宽度差,分析了温度场和应力场不均匀分布的特点。通过冷却试验模拟了小型H型钢轧后冷却过程,采用热成像仪获得冷却后的H型钢温度场。温度场与宽度差的计算结果与试验结果吻合良好。在此基础上分析了采用3种不同换热系数组合的冷却方案时上下翼缘横向、R角处纵向代表性特征截面上Mises应力与等效应变分布的规律,研究了R角处换热系数对翼缘扩并及上下翼缘宽度差的影响,发现R角处换热系数与上下翼缘宽度差具有线性关系,建立了描述其线性关系的数学模型。研究结果对于优化冷却方案以及提高小型H型钢超快速冷却的均匀性具有理论意义和参考价值。

Ultra-fast cooling is of great significance for the microstructure optimization and performance improvement of H-beam steel.The"out of square"after cooling is an important factor affecting product quality and production stability and also limits the popularization and application of the ultra-fast cooling process.In the cooling process of H-beam steel,the heat transfer coefficient is the key parameter.In order to study the effect of heat transfer coefficient on the"out of square"of small-size H-beam steel during ultra-fast cooling,a 2-D thermal mechanical coupling simulative model is established using Abaqus to simulate the cooling process of the small size H-beam steel.Considering the different cooling characters of the flange and web positions,the section of H-Beam steel is divided into 16 particular cooling areas with particular heat transfer coefficients.As well as three cooling solutions are proposed,under different cooling conditions,the cooling processes are simulated respectively and the temperature field,stress field,and the width difference between upper and lower are obtained.The character of uneven temperature field distribution accompanied by irregular stress field is analyzed.The experiment is conducted to simulate the cooling process of small size H-beam steel.The temperature field after cooling is obtained using the thermal image instrument.The simulation results meet experimental data well.Based on the experiment and simulative calculation,the relevant regularities are summarized,including the uneven Mises stress and equivalent strain distribution along paths specified on the simulative model,which are at the lateral direction of upper and lower flanges and the vertical at R corner.The linear relationship between the changing heat transfer coefficients of R corner and width differences are analyzed,and a mathematic model is built to describe it.The research results have theoretical significance and reference value for optimizing the cooling process and improving the uniformity of ultra-fast cooling of small H-beam steel.