回火温度对抗硫钻杆钢析出相形貌及力学性能的影响

通过光学显微镜(OM)、透射电镜(TEM)观察及硬度、拉伸性能测试,研究了抗硫钻杆钢中析出相的析出行为。结果表明:抗硫钻杆钢中析出相的形貌及结构尺寸具有多重特征,表现出对回火温度的依赖性。580℃回火温度下,铁素体基体上析出微米量级的棒状及纳米量级的球形析出相,抗硫钻杆钢强度因而较高。回火温度升高到625℃,析出相形貌逐渐向球形演变,并且其体积分数增加,抗硫钻杆钢强度、塑性同时提高,强度达到150 ksi钢级,表现出良好的强度/韧性匹配。回火温度680℃下,析出相沿晶界析出并逐渐聚集,导致抗硫钻杆钢强度急剧降低。抗硫钻杆钢的强/韧性匹配依赖于析出相—位错交互作用和析出相—基体变形协调两种机制的相互竞争。

Effect of tempering temperature on precipitate and mechanical properties of an anti-sulfur,drill pipe steel in H_2S containing environments

Precipitates and mechanical properties of an anti-sulfur drill pipe steel tempered at different temperatures were investigated by means of optical microscopy(OM),transmission electron microscopy(TEM),hardness and tensile tests.The results show that rod-shaped precipitates with micron size and spherical-shaped precipitates with nanometer size are observed in the matrix of ferrite for the steel tempered at 580 ℃.As tempering temperature increases to 625 ℃,the volume fraction of precipitate increases remarkably,and its shape is evolved into sphere gradually.Consequently,strength and toughness of the steel improves simultaneously,with the tensile strength higher than 1000 MPa.With increasing tempering temperature to 680 ℃,precipitation occurrs and segregates along grain boundary,which results in degradation in strength.Finally,the competitive mechanism between precipitate-dislocation interaction and harmonizing precipitate-matrix deformation,which is responsible for optimial match between strength and ductility,is discussed.