卷取温度对热轧X70管线钢层流冷却过程残余应力的影响

通过热膨胀仪和Gleeble3500热模拟试验机检测X70钢的膨胀系数、高温屈服强度和弹性模量,采用Marc有限元软件计算了热轧带钢在层流冷却中卷取温度分别为500、550和600℃时的温度场、相变体积分数、残余应力随时间的变化.结果表明:层流冷却过程中,在水冷前期带钢边部的应力超过了该温度下钢板的屈服强度,带钢板形会向着边浪发展;水冷结束时,边部应力值再次超过屈服强度并发生了塑性变形,带钢板形会向着中浪发展.在保证X70管线钢性能的条件下,降低卷取温度有利于钢板贝氏体相变的完成和层流冷却阶段残余应力的降低.

Effect of coiling temperature on residual stresses in hot-rolled X70 pipeline steel strips during laminar cooling

The thermal expansion coefficient,high-temperature yield strength and Young's modulus of hot-rolled X70 pipeline strips were tested with a thermal expansion instrument and a thermal simulation test machine Gleeble3500.The temperature field,bainitic volume fraction and residual stresses in the hot-rolled strips during laminar cooling were calculated with the finite element software Marc when the coiling temperature is 500,550 and 600℃,respectively.It is shown that stresses in the strip edge exceed the yield strength of the steel at the same temperature in the earlier water cooling stage,leading to edge waves;but in the end of water cooling,stresses in the strip edge exceed the yield strength again and generates plastic deformation,which causes center waves.Reducing the coiling temperature is in favor of completing bainite transformation and decreasing residual stresses in the hot rolled strips on the assumption that the properties of X70 pipeline steel are ensured.