X70抗大变形管线钢管的组织结构和形变硬化性能分析

采用金相和电子背散射衍射分析、准静态拉伸及数值模拟方法,研究了X70抗大变形管线钢管的组织结构、形变硬化性能及其可采用的表征方法.结果表明:X70抗大变形管线钢在整个塑性应变区域内不符合Hollomon公式,不具有确定的形变硬化指数n；在管线钢塑性变形的起始阶段n较大,但随着应变增大n快速减小；当总应变达到2.0％之后,形变硬化能力趋于稳定.工程应用中利用Rt1.5/Rt0.5、R2.0.0/Rt1.0和Rt5.0/Rt1.0三个应力比可以较好地描述抗大变形管线钢的形变硬化性能.当Rt1.5/Rt0.5≥1.070、Rt2.0/Rt1.0≥1.025、Rt5.0/Rt1.0≥1.050时,可使钢管压缩侧2倍管径长度上的平均压缩应变大于1.3％.

Microstructure and Strain-Hardening Performance Analysis for X70 High Strain Line Pipe

Microstructure,strain-hardening capacity and characterization method of X70 high strain line pipe were investigated by metallographic analysis,electron backscatter diffraction,quasistatic tension and finite element method.It is concluded that X70 high strain line pipe steel does not follow the Hollimon formula in the entire deforming process,and the strain-hardening exponent of the steel is not constant.At the beginning of plastic deformation,the strain-hardening exponent of the steel gets higher,but the value decreases rapidly with stain increasing,and then becomes stable after 2.0% of total strain.The stress ratios of Rt1.5/Rt0.5,Rt2.0/Rt1.0 and Rt5.0/Rt1.0 are verified to perfectly characterize the strain-hardening capacity of X70 high strain line pipe steel in engineering.As Rt1.5/Rt0.5≥1.070,Rt2.0/Rt1.0≥1.025,and Rt5.0/Rt1.0≥1.050,the average strain over the gauge length of 2 times of outer diameter centered at the wrinkle on intrados peak is above 1.3%.