通过采用金相显微镜、扫描电镜及能谱分析等手段，对铌微合金化热轧带肋钢筋的连铸方坯质量及钢筋表面裂纹进行了分析研究。结果表明，连铸方坯上的中心疏松、中间裂纹和中心裂纹颇为严重，分析认为这些缺陷是浇注温度、冷却强度和拉坯速度等因素综合影响的结果。钢筋表面裂纹为纵向裂纹，主要是由表层及亚表层的夹杂物而并非连铸方坯内部裂纹所引起的，讨论了夹杂物对钢筋纵向裂纹扩展和分叉的影响，裂纹扩展时遇到难以变形的大颗粒夹杂易发生分叉。提出了优化冶炼和改进连铸工艺等相关措施并取得了良好的效果。
The surface cracks of niobium microalloyed hotrolled ribbed bars and the continuously cast billets were studied respectively by means of using metallographic microscopy, scanning electron microscopy (SEM) and energy spectrum analysis. Results indicate that the continuous casting billets have serious defects such as centre porosity, interal cracks and centre cracks, caused by the combined effects of improper casting temperature, cooling intensity, casting speed and so on. On surface of bars there were the longitudinal cracks caused by inclusions on the outer layer, especially the subouter layer of bars, but not the interal cracks in billets. The effect of inclusions on the growth and branching of longitudinal cracks were discussed. The large inclusions with poor deformability could easily lead to branching of cracks during propagation. Based on the above conclusions, the relative precautions including optimization of steel refining and improvement of continuous casting parameters were offered and good effect was obtained.
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