Modifications in the properties of galvannealed steel sheet have been made to meet the needs of the automotive industry. The press formability (powdering and flaking) of the galvannealed steel sheet is very sensitive to the phase composition and coating weight of the coating. The allowable coatings or a satisfactory anti-powdering property may fail to provide the anti-flaking property, showing a high coefficient of friction due to the existence of a soft phase at the surface. In this study, the effects of an inorganic film on the surface of the galvannealed coating were studied improving press formablity. It was found that a thin borax film was effective to minimize surface friction and to improve unti-flaking properties. Short electrode life is another problem, as it limits continous spot welding of the galvannealed steel sheet. During welding, electrode tips (Cu) are consumed by an interaction with the coating and the steel substrate. A small amount of B addition in the ultra-low carbon steel substrate was found to be effective in incressing the electode life by reducing this interaction. Thus, galvannealed steel sheet becomes one of the best balanced materials for automotive panels when used with a borax coating and B addition to the ultra-low carbon steel substrate.


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    Title :

    Improvements in formablity and spot weldability of galvannealled steel sheet


    Additional title:

    Verbesserung der Formbarkeit und der Punktschweißbarkeit von galvanisch getempertem Stahlblech


    Contributors:
    Tobiyama, Y. (author) / Kato, C. (author) / Yasuda, A. (author) / Mochizuki, K. (author) / Morito, N. (author)

    Published in:

    Publication date :

    1994


    Size :

    7 Seiten, 8 Bilder, 4 Tabellen, 12 Quellen



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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