合金钢棒材轧制的平均轧辊半径计算模型

 在合金钢棒材生产中,轧制过程中椭圆与圆孔型对棒材成品的尺寸精度及质量缺陷起决定性作用,在计算轧制工艺规程时一般用平均轧辊半径等效代替轧槽轮廓变化的轧辊半径,因此,平均轧辊半径计算模型的可靠程度对轧制工艺(轧制速度、压下量、轧制力等)的合理选取和产品几何尺寸精度的提升具有重要作用。在现有平均轧辊半径模型基础上,考虑不同合金钢种宽展影响,利用孔型轧制表面轮廓预测模型推导得出变形轧件断面形状与轧制临界点的求解公式,提出了用出口轧件断面面积与临界平均宽度来计算等效矩形平均高度的方法,得到了椭圆与圆孔型平均轧辊半径的新计算模型,并进行了轧制试验验证。试验结果表明,与现有模型相比,新计算模型在一定程度上提高了平均轧辊半径的计算精度。同时,基于合金成分影响系数探究了不同合金钢种轧制变形后的临界点分布对应关系。考虑到孔型侧壁直线的存在,对圆孔型轧制接触状态进行了阶段划分,当合金成分系数较小(碳结钢与珠光体-马氏体钢)时,轧制临界点落于圆弧轧槽上,所有计算模型均有效;当合金成分系数超过1.33(奥氏体钢与铁素体钢)时,轧制临界点扩展至侧壁直线上,原有计算模型失效,轧制工艺参数由新计算模型求解。基于新模型的合金钢种轧制临界分布对棒材轧制钢种变换工艺参数的快速制定具有重要指导意义。

Analytical model of mean roll radius in alloy steel bar rolling

In alloy steel bar rolling, oval and round pass play a decisive role in the dimensional accuracy and quality defects of finished bar. When calculating the rolling process specification, the mean roll radius is generally used to replace the roll radius of groove profile change. Therefore, the reliability of mean roll radius calculation model plays an important role in the reasonable selection of rolling process (rolling speed, reduction, rolling force, etc.) and the improvement of geometric dimension accuracy of products. On the basis of existing mean roll radius model, considering the influence of spread for different alloy steels, the calculation formulas of section shape and rolling critical point of deformed rolled piece were deduced using the prediction model of pass rolling surface profile. A method for calculating the equivalent rectangular average height using the section area and critical average width of export rolled pieces was proposed. A new calculation model for the mean roll radius of oval and round pass was given and verified by rolling experiments. The rolling experiment results show that, compared with the existing model, the new calculation model improves the calculation accuracy of mean roll radius to a certain extent. At the same time, based on the influence coefficient of alloy composition, the corresponding relationship of critical point distribution after rolling deformation of different alloy steels is explored. Taking into account the existence of straight lines on the side walls of pass, the rolling contact state of round pass is divided into stages. When the alloy composition coefficient is small (carbon structure steel and pearlitic-martensitic steel), the rolling critical point falls on the arc groove, and all calculation models are valid. When the alloy composition coefficient exceeds 1.33 (austenitic steel and ferritic steel), the rolling critical point extends to the straight line of side wall, the original model calculation fails, and the rolling process parameters are solved by the new calculation model. The critical distribution of alloy steel grade rolling based on the new model has important guiding significance for the rapid formulation of process parameters for bar rolling steel grade transformation.