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借助TEM、SEM、EBSD等显微组织分析手段及力学性能测试,研究了深海用超厚规格X70管线钢板的显微组织与力学性能的关系。实验结果表明:为满足深海用厚壁X70管线钢对纵向变形能力及DWTT(落锤撕裂实验)断裂韧性的严格要求,组织设计可采用针状铁素体+多边形铁素体的双相组织方法。针状铁素体为硬相、多边形铁素体为软相的双相组织中,屈强比随多边形铁素体数量的增加而降低,增大铁素体晶粒尺寸也能降低材料屈强比;在针状铁素体为基体的显微组织中,引入适量的细化多边形铁素体还可降低其有效晶粒尺寸,提高材料DWTT性能,但多边形铁素体体积分数过多、晶粒尺寸过大时,平均有效晶粒尺寸增加,DWTT性能反而降低。
The relationship between the microstructure and mechanical properties of deep-sea ultra-thick X70 pipeline steel was studied by TEM, SEM, EBSD and other microstructure analysis methods and mechanical properties tests. The experimental results show that in order to meet the strict requirements of longitudinal deformation capacity and DWTT fracture toughness of deep-walled X70 pipeline steel, the structure design can adopt the dual-phase structure of acicular ferrite + polygonal ferrite method. When the acicular ferrite is hard phase and the polygonal ferrite is soft phase, the yield ratio decreases with the increase of the amount of polygonal ferrite. Increasing the ferrite grain size also reduces the yield strength In the acicular ferrite matrix microstructure, the introduction of the appropriate amount of refined polygonal ferrite can also reduce the effective grain size and improve the performance of the material DWTT, but the polygonal ferrite volume fraction too much, the crystal When the particle size is too large, the average effective grain size increases and the DWTT performance decreases instead.