Analysis of Delamination of Tensile Fracture in Grade 355 MPa Low Alloy Steel
The lamination phenomenon of transverse tensile fracture of low alloys steel plate with 355 MPa was analyzed by means of non-metallic 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.
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