355MPa级别低合金钢拉伸断口分层现象分析

Analysis of Delamination of Tensile Fracture in Grade 355 MPa Low Alloy Steel

通过非金属夹杂物、金相组织观察及扫描电镜、能谱检验等分析技术手段,对355 MPa级别低合金钢板试样横向拉伸断口分层现象分析。结果表明,存在MnS夹杂物及珠光体带状组织,其中,塑性夹杂物割裂钢基体,合金元素偏析引起带状组织易诱发微裂纹,两因素相互作用影响钢基体连续性,是诱发拉伸断口分层的主要原因;通过强化铁水原料预处理,提高钢水的纯净度,严控硫、磷等有害元素含量或经Ga处理等手段,改变硫化物夹杂物形态,配合连铸低过热度浇注及控轧控冷工艺,优化金相组织形态,可有效减少该类缺陷的发生。

The lamination phenomenon of transverse tensile fracture of low alloys steel plate with 355 MPa was analyzed by means of nonmeallic inclusions,metallographic structure observation,scanning electron microscopy,energy spectrum test and other analytical techniques.The results show that there are MnS inclusions and pearlite zonal structure,among which plastic inclusions slice the steel matrix,and the zonal structure caused by alloying element segregation is easy to induce microcracks.The interaction of the two factors affects the continuity of the steel matrix,which is the main reason to induce the delamination of tensile fracture.By strengthening the pretreatment of molten iron raw materials,improving the purity of molten steel,strictly controlling the contents of sulfur,phosphorus and other harmful elements or Ga treatment,the morphology of sulfide inclusions can be changed,and the occurrence of such defects can be effectively reduced by optimizing the microstructure morphology with low superheat pouring of continuous casting and controlled rolling and cooling process.