20~#钢的慢速率高温流变实验和模拟

碳钢种类繁多且广泛应用于建筑、汽车制造等领域.选择其中的20#低碳钢,利用Paterson高温高压流变仪在恒温条件下,完成了单阶恒应变速率和多阶突变应变速率两类轴向压缩实验.实验条件如下:温度700～900℃,围压100々300MPa,应变速率105～103s1测定了不同条件下变形过程中的应力-应变曲线,并进行了流变本构方程计算.结果显示流变本构方程中的参数对应变的函数依赖关系与快速变形时类似.由本构方程模拟计算所得的流变应力可以很好地拟合单阶恒应变速率实验;由于多阶突变应变速率实验受变形历史影响大,因此拟合精度较差但仍可接受.另外,研究表明,在慢速率变形时无论是低温的铁素体相还是高温的奥氏体相,20#钢的流变行为均可用相同的流变本构方程进行描述,但是相变区的流变行为则不同,需要对lnA的表达式稍作修正.

Experimental study and prediction of deformation behavior of low carbon steel at low strain rate and high temperature

Various types of carbon steel have been used extensively in construction and manufacturing. In this paper, axial deformation tests of 20^# low carbon steel using either constant strain rate or suddenly jumping strain rates were carried out in a high pressure, high temperature Paterson-type gas apparatus. The test pressures, temperatures and strain rates ranged from 100 to 300 MPa, 700 to 900℃, and 10^?5 to 10^?3 s^?1, respectively. The stress-strain curves from the experiments were used to obtain the deformation constitutive equation. The functions relating the parameters in the constitutive equation and the strain are similar at both low and high strain rates. The predicted flow stress calculated from the constitutive equation fits the experimental data from the constant strain rate tests well, but only roughly fits the data from the strain rate jump tests. Regardless of whether the steel is ferritic or austenitic, the deformation behavior of 20^# low carbon steel at low strain rate can be described by the same constitutive equation; however the parameter lnA in the equation needs to be corrected when deformation is carried out at temperatures where a phase change is occurring.