35MnB钢高温变形行为及本构方程

Deformation behavior and constitutive equation of 35MnB steel at high temperature

为了合理制定35MnB钢制件热成形工艺参数,在790~1190℃温度范围内,应变速率为0.01~10 s^(-1)及总压缩变形量(真实应变)为0.6的试验条件下,采用Gleeble-1500D热模拟试验机对35MnB钢进行热压缩变形试验,研究其高温变形行为。结果表明:流变应力随着温度的升高而减小,随着应变速率的增大而增大。同一应变速率下,随着变形温度的升高应力峰值向左移动,应力-应变曲线整体下移;同一变形温度下,应变速率越大,应力峰值越高,相应的应变量也越大。采用含有变形温度(T)和变形激活能(Q)的Arrhenius equation方程的双曲正弦模型,构建了35MnB钢在高温下流变应力与应变速率的本构方程。并验证了所构建本构方程的准确性,计算结果显示预测应力峰值与试验应力峰值吻合较好。通过采用本文所构建的35MnB钢本构方程对大型液压装载机锻造摇臂成形过程进行模拟,结果证明本文所构建的本构方程可以应用于35MnB钢制件高温成形模拟过程,并为实际生产做指导。

In order to reasonably formulate the hot forming process parameters of 35MnB steel, the thermal compression experiment of 35MnB steel was conducted on the Gleeble - 1500D thermal-mechanical simulator at 790 - 1190 ℃ with the rate of deformation 0. 01 - 10 s^-1 and the deformation of 60%, and its deformation behavior at high temperature was studied. Results show that the flow stress decreases with the increasing of temperature, and increases with the increasing of strain rate. At the same strain rate, with the deformation tempera- ture increases, the peak stress moves to the left and the stress-strain curve moves down. At the same deformation temperature, the higher strain rate is, the higher peak stress and corresponding strain are. The constitutive equation between the flow stress and strain rate of 35MnB steel at high temperature was built with the hyperbolic sine model of Arrhenius equation which contained the deformation tempera- ture （T） and the activation energy （Q） , and the accuracy of the proposed constitutive equation was verified. The calculation results show that the experimental peak stress is coincide better with the predicted value. The result of simulation of the large forging hydraulic loader rocker arm forming process with the built constitutive equation shows that the constitutive equation can be used in the simulation of 35MnB steel, and be the guidance for practical production.