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通过在ML20MnTiB钢方坯表面预置人工裂纹的方法,研究了裂纹在线材热轧过程的演变规律。结果表明,方坯表面预置纵裂纹经多道次轧制变形后的微观特征表现为:裂纹处有较明显的脱碳层和较厚的氧化铁皮残留,且裂纹与轧后盘条表面接近垂直;裂纹深度随着轧制变形量的增大而减小,且裂纹深度与横截面积成正比例减小。方坯表面预置角部横裂纹经多道次轧制后演变成了较短的纵向裂纹,裂纹横截面形貌呈小角度折叠状,脱碳特征明显。不同直径的线材对方坯表面裂纹深度的要求不同,轧制盘条规格越大,对铸坯表面裂纹要求越严格。
By means of presetting artificial cracks on the surface of ML20MnTiB steel billet, the evolution of the crack during the hot rolling process of the wire was studied. The results show that the microscopic features of the pre-set longitudinal cracks on the billet after multi-pass rolling deformation are as follows: there are more obvious decarburized layers and thicker scale residues in the crack, and the cracks are close to the surface of the rolled rod Vertical; the crack depth decreases with the increase of rolling deformation, and the crack depth decreases in direct proportion to the cross-sectional area. After the multi-pass rolling, the transverse cracks at the pre-formed corner of the billets evolved into short longitudinal cracks. The cross-sectional shape of the cracks showed a small-angle folded shape with obvious decarburization characteristics. Wire rods of different diameters have different requirements on the surface crack depth of the billet. The larger the gauge of the rolled wire rod, the stricter the surface crack requirements of the slab.