Abstract
Hot rolling is an essential process for the shape-forming of bearing steel. It plays a significant role in the formation and distribution of flow lines. In this work, the effect of flow lines is investigated by analyzing the microstructure and mechanical anisotropy of hot-rolled bearing steel. It was found that carbides rich with Cr and Mn elements are distributed unevenly along the flow-line direction of the hot-rolled bearing steel. Moreover, the mechanical characterization indicates that ultimate tensile strength and yield strength do not have any significant difference in two directions. Nevertheless, an ultrahigh section shrinkage of 57.51% is obtained in the 0° sample that has parallel flow lines, while 90° sample shows poor section shrinkage. The uneven distributed carbides will affect the direction and speed of crack propagation during tensile deformation. Therefore, the 0° and 90° samples exhibit great difference in plastic property. Meanwhile, after tensile deformation, a delaminated texture is observed in the flow lines, which may be caused by different degrees of deformation of grains due to the uneven distribution of carbides. The results of this work may provide guidance for controlling and optimizing flow lines in the manufacturing of bearing rings.
Highlights
The hot rolling process is essential for the shape-forming of bearing steel and it directly influences the formation and distribution of flow lines [1,2,3,4,5]
Jiang et al [6,7] investigated the behavior of the microstructure evolution of the bearing rings during hot rolling and found that the flow lines were consistent with the distribution of carbides
The results indicated that the applied V-shaped punching pin and punching recess could resolve disordered flow lines
Summary
The hot rolling process is essential for the shape-forming of bearing steel and it directly influences the formation and distribution of flow lines [1,2,3,4,5]. Li et al [8] reported that the bandshape or chain-shape distribution of inclusions could cause the formation of flow lines during deformation They reported that flow lines directly determine the mechanical properties of the workpiece because the distribution of the carbides and inclusions seriously affect cracks initiation and propagation. Jiang et al [16] investigated the mechanical anisotropy of the forged bearing rings by conducting tensile tests They revealed that the mechanical properties in the direction parallel to the direction of the flow lines were superior to those in the perpendicular direction. The influence of flow lines on mechanical anisotropy is studied and the final structure-property relationship is further discussed
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