X80级高强低合金管线钢组织与冲击韧性

Microstructure and impact toughness of X80 grade high strength low alloy pipeline steel

为了研究准多边形铁素体/板条贝氏体/粒状贝氏体显微组织的高强低合金X80管线钢的低温韧性与冲击裂纹扩展特点,用OM、SEM、EBSD和TEM等多尺度手段进行了表征。结果表明,与针状铁素体/粒状贝氏体相比,在-60℃以上时,准多边形铁素体/板条贝氏体/粒状贝氏体表现出更好的阻止裂纹扩展的能力,准多边形铁素体可以分割显微组织并细化有效晶粒尺寸,增加大角度晶界比例,协调约束冲击裂纹扩展,进而提高韧性;当温度在-60℃以下时,这种准多边形铁素体/板条贝氏体/粒状贝氏体对裂纹扩展的协调约束作用减弱,成为显微组织的"软区",使得材料韧性下降。

In order to study the low-temperature toughness and related impact crack propagation characteristics of a high strength low-alloyed X80 pipe steel that contains mainly quasi-polygon ferrite/lath bainite,the multiscale means including optical microscope(OM),scanning electron microscopy(SEM),electron back scattering diffraction(EBSD)and transmission electr on microscopy(TEM)were used. The results showed that when the temperature was above -60 ℃, the quasi polyg on ferrite/lath bainite pipeline steel obtained the stronger ability to prevent crack growth in comparison with the acicular ferrite/granular bainite pipe steel. Because of the existence of quasi polygon ferrite,the effective grain size of the tissue could be divided into thin sections. The large angle proportion of the grain boundary could be increased. And the grain boundary of the tissue could be harmonize constraint. Therefore,the crack propagation energy of the material was enhanced and the toughness of the material was improved significantly. When the temperature was below -60 ℃,the coordination of the quasi polygon ferrite/lath bainite was weak and turn into the soft area of the materials.