热轧酸洗板表面条带状色差缺陷产生原因及机理研究

针对热轧酸洗板表面条带状色差缺陷问题,以SPHC带钢为试验材料,采用金相法研究了色差缺陷的组织特点,明确了缺陷产生的原因是带钢表层存在增碳现象,使表层碳化物密度上升,晶界出现珠光体形貌异常组织而导致。应用差热分析仪分析了不同自由碳含量保护渣、不同加热温度和保温时间对带钢表面增碳层深度和珠光体组织比例的影响,明确了SPHC热卷表层增碳的内在机理。提出了优化保护渣熔化性能、控制结晶器液面波动和调整加热炉工艺等措施,为消除酸洗板条带状色差提供了控制策略。

Study on the cause and mechanism of striped color difference defects on the surface of hot rolled pickled strip

To eliminate the color difference defects on the surface of hot rolled pickled strip,SPHC strip was used as the tested material and the microstructure characteristics of the defects were studied by metallographic analysis.The formation mechanism was revealed as local carburization on the surface of hot rolled strip, resulting in abnormal pearlite structure at grainboundaries with increase of surface carbide proportion. Using differential thermal analyzer, the effect of free carbon content of mold flux, heating temperature and holding time on the depth of carburizing layer and pearlite ration of the strip surface was analyzed,and the formation mechanism of surface carburczation of SPHC hot rolled coil was clarified. Measures such as the optimization of melting behavior of mold flux, mold level fluctuation control and adjustment of operation parameters of heating furnace were proposed to eliminate the color difference defects of hot rolled pickled strip.