不同冷却速率下硅钢氧化皮结构与酸洗动力学关系

Relationship Between Pickling Kinetics and Scale Structure of Silicon Steel at Different Cooling Rates

研究热轧硅钢卷板各部位因其冷却速度不同造成相结构差异,为热轧硅钢板氧化皮结构调控以及工业酸洗工艺提供理论依据和数据积累。采用场发射扫描电子显微镜、背散射成像、X射线能谱仪以及XRD等方法,结合工业酸洗和实验室模拟酸洗,研究了不同冷却速率下热轧硅钢板氧化皮显微组织结构与酸洗动力学之间的关系,初步探讨了其酸洗机理。结果表明:热轧硅钢卷板快、慢冷部位氧化皮分为两层,主要由Fe、Fe2O3和Fe3O4相组成,而相对含量有明显差异。卷头慢冷部位氧化皮厚度分布不均,表面存在许多裂纹,与基体结合界面平滑;卷尾快冷部位氧化皮均匀致密且较厚,与基体结合界面较粗糙,显微结构差异造成快冷部位氧化皮酸洗动力学更慢。快、慢冷部位氧化皮酸洗机制相似,前期以化学溶解过程为主,后期以两阶段电化学腐蚀过程进行。

The phase structure of hot-rolled silicon steel coil is different due to the different cooling rates. The work aims to provide a theoretical basis and data accumulation for the structure control of hot-rolled silicon steel scale and industrial pickling process. Field emission scanning electron microscope(FE-SEM), secondary electron(SE), backscattered electron(BSE), X-ray energy dispersive spectroscopy(EDS) and X-ray powder diffraction(XRD), combining with the industrial pickling and laboratory simulated pickling, were performed to study the relationship between the scale microstructure structure and pickling kinetics of the hot-rolled silicon steel under different cooling rates. Pickling mechanism was discussed preliminarily. Results show that oxide scales of rapid and slow cooling hot-rolled silicon steel coils are both double-layer structure, which consists of Fe, Fe2O3 and Fe3O4 with different relative contents. The oxide scale of slow cooling coil is uniform with many cracks on the surface. And the interface between the substrate and oxide layer is smooth. The oxide scale of rapid cooling coil is uniform and dense, and the interface with the matrix is rough. The microstructure difference causes the pickling kinetic of rapid cooling coils to be slower. The pickling mechanism of rapid and slow cooling coil is similar, at which chemical dissolution plays a major role in initial stage and two-stage electrochemical corrosion in later process.