基于3D热加工图的节镍型高锰奥氏体不锈钢的热变形特性

Hot Deformation Characterization of Low-Ni Austenite Stainless Steel with High Mn Through 3D Processing Map

为优化较大变形量节镍型奥氏体不锈钢热轧工艺,在Gleeble-3500热力模拟试验机上对1Cr14Mn10Ni1.57不锈钢进行了温度950~1250℃,应变速率0.01~5.0s^(-1),应变为0.36、0.69和0.92的等温热压缩实验。建立了基于应变影响三维热加工图,使用Arrhenius型本构方程计算出了3种应变下的热激活能,联系微观组织分析了热加工图受应变影响的演变行为。结果表明:当真应变从0.36增加到0.69和0.92时,热激活能Q从501.66kJ/mol分别下降到427.45和424.86 kJ/mol,材料的动态软化效应在0.36~0.69应变区间内显著增强;热加工图显示,峰值区域和谷值区域会随着应变的增加向低温和高速方向移动,这是由于应变输入的总能量增加导致的;实验钢在热加工图中存在3个峰值区域,0.69真应变,1175~1225℃,1.0~5.0 s的条件下能够达到最高38%的热加工功率耗散效率,这与高应变速率下的温升有关;随着应变增加到0.69和0.92,失稳区域的面积先增大后减小;应力应变曲线和微观组织证明,高功率的区域的软化机制为动态再结晶,失稳区域表现为不连续动态再结晶和动态回复。

To optimize the process of hot rolling for low-Ni austenitic stainless steel with large deformation, the isothermal hot compression experiments of 1Cr14Mn10Ni1.57 stainless steel were carried out on Gleeble-3500 thermal simulation system at temperatures of 950~1250 ℃, strain rates of 0.01~5.0 s, and strains of 0.36, 0.69 and 0.92. The 3D hot processing maps were established based on the strain effect. The thermal activation energies under the three strains were calculated by the Arrhenius type constitutive equation. The evolution behavior of the hot processing map under the strain effect was analyzed by combining with the microstructure. The r esults show that when the true strain increases from 0.36 to 0.69 and 0.92, the thermal activation energy Q decreases from 501.66 kJ/mol to 427.45 and 424.86 kJ/mol, indicating that the dynamic softening in the material is significantly enhanced in the strain range from 0.36 to 0.69. The hot processing map shows that the peak and valley regions change with the increasing strain, mainly in the direction of low temperature and high speed, which is caused by the increase of the total energy of strain input. There are three peak regions in the hot proc essing map of the experimental steel, only under the conditions of 0.69 true strain, 1175~1225 ℃, 1.0~5.0s^(-1) can reach the maximum processing efficiency of 38%, which is related to the temperature rise at high strain rate. As the strain increases to 0.69 and 0.92, the instability region extends first and then shrinks. The stress-strain curves and microstructure show that the softening mechanism of the high efficiency region is dynamic recrystallization(DRX), while the instability region is characterized by discontinuous dynamic recrystallization(DDRX) and dynamic recovery(DRV).