焊丝钢热变形本构模型研究

Study on constitutive models of hot deformation for welding wire steel

利用Gleeble-3500热模拟实验机对焊丝钢ER70S-6进行等温恒应变速率压缩实验,研究其热变形行为,变形温度范围为900~1200℃,应变速率范围为0.01~10 s^(-1),获得应变为60%时的真应力-真应变曲线。采用修正的Johnson-Cook模型与应变相关的Arrhenius模型分别拟合热压缩实验中的真应力-真应变数据,确定了两种本构模型的参数值,进而对比研究了两种流动应力模型的预测精度。结果表明,流变应力随变形温度的增加而减小,随应变速率的增加而增加。根据修正的Johnson-Cook模型与应变相关的Arrhenius模型计算所得预测值与实验值之间的平均误差分别为11.6%与4.51%。前者适用于多组应力-应变曲线变化趋势相同的情况,而后者与实验数据吻合度好,能够准确预测焊丝钢的流变应力。

The isothermal compression experiments with the same strain rate of welding wire steel ER70 S-6 were carried out using Gleeble-3500 thermal simulator to study its thermal deformation behavior. The range of deformation temperature is 900-1200 ℃,and the range of strain rate is 0. 01-10 s^(-1). The true stress-true strain curves at the strain of 60% were obtained. The modified Johnson-Cook model and strain-dependent Arrhenius model were used to fit the true stress-true strain data in hot compression experiment,respectively,and the parameters of two constitutive models were determined. Then,the prediction accuracy of two flow stress models was compared and studied. The results show that the flow stress decreases with the increase of deformation temperature and increases with the increase of strain rate. The average error between the predicted value calculated by the modified Johnson-Cook model and the strain-dependent Arrhenius model and the experimental value is 11. 6 % and 4. 51 %,respectively. The modified Johnson-Cook model is suitable for situations where a set of stress-strain curves have the same variation trend,and the strain-dependent Arrhenius model is in good agreement with the experimental data and can accurately predict the flow stress of welding wire steel.