含钛高强带钢中心分层样拉伸过程断口分析

Analysis on Tensile Fracture With Centerline De-Lamination Defect of Ti-Bearing High Strengthen Steel Strip

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。

Serious centerline de-lamination fractures appeared in hot rolled strip of high-strength structural steel HGTOC during tensile test. Specimens under different stress levels were designed for comparison with normal speci- men. The formation of centerline cracks of the test specimens was studies by optical microscopy and scanning elec- tron microscopy with energy dispersive spectroscopy. Progressive failure for centerline lamination fracture was ana- lyzed~ furthermore the cracking mechanism of de-lamination tensile fracture was described. The results indicated that the pearlite colonies of centerline segregation banding were not the main reason of centerline lamellar fracture. The micro-crack was observed around the inclusions which existed in abundance in the center area. With increasing tensile stress, the micro-cracks coalesced, eventually extended to lamellar cleavage fracture.