82B热轧盘条浅表面网状渗碳体缺陷原因分析

为了研究12.5 mm规格82B的热轧盘条浅表面网状渗碳体缺陷的产生原因，使用光学显微镜对82B的热轧盘条浅表层显微组织进行观测、连铸坯表面铣削后检测浅表层碳质量分数、连铸坯表面剥皮后轧制、使用无碳结晶器保护渣和调整连铸坯加热温度。结果表明，连铸坯浅表层不同深度碳质量分数在凝固偏析的范围内属正常波动，未见明显表面增碳现象；连铸坯浅表层剥掉 3.0～5.0 mm后轧制，82B的热轧盘条浅表面网状渗碳体缺陷仍然存在，没有减少的趋势；使用无碳结晶器保护渣生产的连铸坯轧制成材后，盘条浅表面网状渗碳体缺陷依然存在，且没有减少；把连铸坯开轧温度由890～910调整到960～1 010 ℃后， 82B的热轧盘条浅表面再也没有发现网状渗碳体。综合以上结果，该厂82B的热轧盘条浅表面网状渗碳体缺陷是由不恰当的连铸坯加热温度造成的，而不是连铸坯表面增碳造成的。

Cause analysis of superficial network cementite defect in 82B hot- rolled wire rob

In order to investigate the the cause of superficial network cementite defect in 12.5 mm specification 82B hot- rolled wire rob, the superficial microstructures of 82B hot- rolled wire rob were observed, the mass fraction of the superficial carbon was detected after milling the surface of billet, the mould fluxes without carbon were applied and the heating temperature of the billet was adjusted. Results showed that the mass fraction of carbon at different depth from the shallow layer of the billet was normal fluctuation when considering the solidification segregation, and there was on obvious surface recarburization. After milling the billet of 3.0- 5.0 mm from the shallow layer, the superficial network cementite defect also existed in 82B hot- rolled wire rob and had no decreasing trend. And after rolling the billets produced by the mould fluxes without carbon, the superficial network cementite in 82B hot- rolled wire rob still existed and had no decreasing trend neither. After adjusting the initial rolling temperature of the billet from 890- 910 to 960- 1 010 ℃, the superficial network cementite defect in 82B hot- rolled wire rob was not found any longer. Thus, it could be concluded that the reason for the superficial network cementite defect in 12.5 mm specification 82B hot- rolled wire rob produced in the factory was the incorrect heating temperature of the billet, rather than the surface recarburizing of the billet.