钢高温蠕变特性对连铸坯矫直变形的影响

Effects of high-temperature creep property on straightening deformation of continuous casting slab

为使连铸坯在矫直过程中能够充分利用钢的高温蠕变特性,避免产生内部矫直裂纹,对铸坯矫直及机型曲线进行了研究。首先,在Gleeble-3800热模拟试验机上对Q345C连铸坯进行热塑性和高温蠕变试验,确定了Q345C钢的热物性参数和最小蠕变应变速率方程;其次,根据钢的高温蠕变特性,针对目前使用的某连铸机设计了新机型曲线;最后,采用热力耦合数值模拟的方法,计算了距离铸坯内弧侧表面38.3 mm处中心点的温度分布和应变速率。通过蠕变矫直机型应变速率和蠕变速率的对比表明,蠕变矫直机型曲线可以充分利用钢的高温蠕变变形进行矫直,蠕变变形量占总矫直变形量的比例达到88.6%,因此可降低铸坯内部矫直裂纹产生的可能性,有利于提高铸坯质量。

Straightening deformation and casting curve of slab were studied in this paper in order to make full use of high temperature creep property of steel and avoid the internal cracks caused by straightening. First of all,uniaxial tensile tests were carried out on the Gleeble-3800 so as to evaluate the high-temperature mechanical properties and calculate the parameters of minimal creep strain rate equation. Secondly,a new casting curve full applying the high temperature creep property of steel was designed based on the size of current casting machine. At last,the temperature and strain rate at 38.3 mm beneath the center of inner arc surface in new creep straightening curve was presented by thermal-mechanical coupled algorithm. It can be concluded that the slab was straightened by full using of the high temperature creep deformation and 88.6% of straightening deformation came from the creep deformation. Therefore,cracks caused by bending and straightening could be effectively avoided,and the quality of the slab was improved.