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    STP1600

    Relationship between Hot Workability and Center Segregation in Bearing Steel

    Published: 11 December 2017


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    Abstract

    The inner and outer rings of taper roller bearings made of 100Cr6 bearing steel are usually hot forged prior to subsequent manufacturing operations. During hot forging, the workpiece is subjected to high temperature and heavy deformation. Therefore, the requirement for hot workability—the ability to be deformed under hot forming conditions—and its relationship to center segregation are of vital importance. This paper summarizes the findings of an investigation relating to a quality issue where cracks were detected in the bore area of inner rings. A metallurgical inspection showed that melting at the grain boundaries had occurred both at and beneath the crack surface. Efforts were then made to reduce the temperature increase caused by the additional heat generated during the hot forging process. However, this temperature increase could not be eliminated. Therefore, it is essential that the steel itself should be suitable for the hot forging process. In other words it should meet certain requirements for hot workability. In order to compare the hot workability of 100Cr6 steel from different steelmaking process routes, a simple but effective test was carried out by hot forging steel blanks at different forging temperatures. It quickly became apparent that the specific steelmaking process route used for the aforementioned inner rings produced the lowest hot workability. Further investigations were performed by means of a Gleeble test to quantify the hot workability in relation to the center segregation level.

    Keywords:

    hot workability, center segregation, Gleeble test


    Author Information:

    Liu, Xiaoping
    SKF Bearing Operations, Lüchow,

    Kim, Sungyu
    SeAH Besteel Corp., R&D Center, Gunshan-si Jeollabuk-do,

    Kerrigan, Aidan
    SKF Engineering & Research Center, Nieuwegein,


    Committee/Subcommittee: A01.28

    DOI: 10.1520/STP160020160148