针对Ф50 mm大规格HRB500钢筋沿横肋根部冷弯裂纹试样,进行化学成分、夹杂物级别、组织特征和断口形貌等检测后发现,钢筋表面树枝状组织是钢筋冷弯开裂的主要原因.热处理试验表明:l 000 ℃保温50 min,树枝状组织开始均匀化;保温90 min,可以获得F+P为主的均匀组织.通过降低连铸钢水过热度、二冷水冷却强度及控制拉速和轧制节奏、延长加热保温时间等工艺改进措施,能有效改善大规格钢筋边部树枝状组织.%Against the 50mm HRB500 hot rolled ribbed bar along the roots of transverse ribs bending crack specimen, the tests of chemical composition, inclusion grade、microstructure and fracture were carried out, then it was found that the dendritic structure of steel bars is the main cause of the cold bending cracks.The heat treatment test showed that: at 1 000 ℃ for 50 min ,the dendritic microstructure changed homogenized, and as the holding time was extended to 90 min, the uniform F+P microstructure could be obtained.By reducing the superheat of molten steel, cold water cooling strength, rolling rhythm, control the speed, extending the heating and heating time and other process improvements, it can effectively improve the large-scale steel edge dendritic structure.
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