炉卷轧机生产X100管线钢的组织特征与强韧性

Microstructure characteristic and strength-toughness of X100 pipeline steel produced by steckel mill

利用扫描电镜(SEM)、透射电镜(TEM)对炉卷轧机生产X100管线钢的显微组织特点进行了观察与分析,通过背散射电子衍射技术(EBSD)探讨了X100管线钢的有效晶粒尺寸与低温韧性的关系,并利用物理化学相分析的方法对X100管线钢的析出粒子尺寸分布和强化作用进行了定量分析.结果表明:X100管线钢的显微组织以粒状贝氏体为主,晶粒内部和晶界上弥散分布着大量细小的马氏体/奥氏体(M/A)岛;X100管线钢的有效晶粒尺寸较小,仅为2μm左右,细化有效晶粒尺寸和降低组织方向性有利于提高管线钢的低温韧性;X100管线钢中的析出粒子尺寸较小,平均尺寸为45.4nm,但由于其总体质量分数只有0.062%,经计算,其析出强化作用约为52MPa,析出强化对屈服强度贡献较小.

The microstructure of X100 pipeline steel produced by steckel mill was observed by SEM and TEM. Electron backscattered diffraction （EBSD） was employed to investigate the relationship between effective grain size and low-temperature toughness. The size distribution and strengthening effect of precipitation in X100 pipeline steel were quantitatively analyzed through physicochemical phase analysis technology. The results show that the microstructure of X100 pipeline steel mainly consists of granular bainite with plenty of M/A islands dispersing in the matrix or on grain boundaries. The effective grain size of X100 pipeline steel is refined to about 2μm. The refinement of effective grains and the reduction of microstructure orientation are two effective ways to improve the low-temperature toughness. The average size of precipitation particles in X100 pipeline steel is refined to 45.4 nm. Since the total mass fraction of precipitation particles is about 0. 062 %, the strengthen effect of precipitation is only about 52 MPa, which does not contribute much to the yield strength.