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针对高强焊接结构钢HG70C带钢在力学性能检验中产生拉伸样断口中心分层缺陷,试验设计获得不同拉伸应力的试样,并对比分析未分层试样。通过电镜观察拉伸样断口截面中心偏析带组织和裂纹的演变,从微观上分析了拉伸样断口心部分层微裂纹的渐进演变过程。研究表明,中心处珠光体组织随着变形伸长扩展,与铁素体界面没有产生微孔。分层断口微裂纹是在超过屈服强度后逐步产生的,且在带钢中心厚度位置存在过多连铸偏析的铌钛夹杂物和MnS带边缘处诱发微裂纹。随着拉伸应力逐渐增大,这些微裂纹相互扩展长大形成了贯通平台,最终产生层状分离断口。
Aimed at high-strength welded structural steel HG70C strip in the mechanical properties of the test results in tensile delamination center delamination defects, the experimental design to obtain different tensile stress specimens, and comparative analysis of un-layered samples. The evolution of microstructure and crack in the center segregation zone of tensile specimen was observed by electron microscope. The gradual evolution of microcracks in the core part of tensile specimen was analyzed microscopically. The research shows that the pearlite in the center expands with the elongation and deformation, and does not produce micropores with the ferrite interface. The micro-cracks in the layered fracture are generated gradually after the yield strength is exceeded, and there are too much continuous casting segregation of niobium and titanium inclusions and micro-cracks at the edges of the MnS band at the strip center thickness. With the gradual increase of tensile stress, these microcracks expand each other to form a through platform, resulting in a layered fracture.