STP647

    Relationship Between Surface Characteristics and Galling Index of Sheet Steel

    Published: Jul 1978


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    Abstract

    The influence of annealing atmosphere and surface finish of cold-rolled steel on the occurrence of galling during stamping operations has been noted empirically for many years. In order to minimize the galling tendencies of drawing quality sheets a program was carried out to define pertinent surface features and their interaction during stamping.

    Commercial steel coils were processed in two types of annealing atmospheres, a hydrogen and nitrogen mixture (HN) and DX-type exothermic gas. The coils were then skin rolled to achieve a wide range of surface roughness. The sensitivity to galling was rated during the stamping of quarter panels and also by means of a sliding friction test in which the ratio of static to dynamic drawing force was used to designate a friction ratio that appeared to correlate well with performance. Surface finish was recorded by standard profilometry techniques, and chemical differences between the types of surfaces were examined by auger electron spectrometry; general aspects of the surfaces were studied by scanning electron microscopy.

    The critical frictional ratio was found to be 1.3, above which sheet steel has galling tendencies. Galling in HN-annealed steel was found to be surface-finish sensitive, and a range of surface finish parameters for nongalling characteristics has been established. DX-annealed steel appeared to be insensitive to the effects of surface finish, and differences in surface films were detected to account for the frictional changes.

    Keywords:

    metal forming, galling, steels, surface finish, friction test, profilometry


    Author Information:

    Hilsen, RR
    Senior research engineer and associate director of Research, Inland Steel Company, East Chicago, Ind

    Bernick, LM
    Senior research engineer and associate director of Research, Inland Steel Company, East Chicago, Ind


    Paper ID: STP30055S

    Committee/Subcommittee: E28.04

    DOI: 10.1520/STP30055S


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