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采用SEM、TEM、EBSD等方法研究了35mm规格船用高强度钢淬火态的截面微观组织特征及精细结构,对其截面不同位置力学性能的对应关系进行了分析。结果表明,35mm淬火态钢板的截面效应明显,距离表面小于8mm时,截面硬度随着距表面距离的增大而减小;在8~17mm范围内,截面硬度处在一个稳定的下平台;在17~18mm范围内,截面硬度出现峰值。心部的抗拉强度和屈服强度均较钢板表面降低了40MPa以上,且心部-80℃冲击功稳定性比表面差。显微组织、板条宽度、有效晶粒尺寸、位错密度等的差异是表面性能优于心部的主要原因。钢板心部大量硬质MA岛存在、中心偏析带及大量非金属夹杂物导致硬度峰值和低温冲击性能的不稳定。
The microstructure and fine structure of the 35 mm high strength HSC steel under quenched condition were studied by means of SEM, TEM and EBSD. The corresponding relationship between the mechanical properties at different positions of the cross section was analyzed. The results show that the cross-section effect of 35mm tempered steel is obvious. When the distance from the surface is less than 8mm, the cross-section hardness decreases with the increase of the distance from the surface. In the range of 8-17mm, the cross-section hardness is in a stable lower platform. 17 ~ 18mm range, the peak section hardness. The tensile strength and yield strength of the core are both lower than the surface of the steel plate by 40MPa or more, and the stability of the impact energy at the core of -80 ℃ is worse than that of the surface. The differences in microstructure, lath width, effective grain size, dislocation density, etc., are the main reasons for the superior surface properties over the heart. A large number of hard MA islands exist in the heart of the steel plate, and the center segregation zone and a large amount of non-metallic inclusions lead to instability of peak hardness and low-temperature impact performance.