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Spot welded joint

  • US 10,081,073 B2
  • Filed: 04/25/2013
  • Issued: 09/25/2018
  • Est. Priority Date: 04/25/2012
  • Status: Active Grant
First Claim
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1. A method of forming a spot welded joint, comprising:

  • providing a plurality of overlapping steel sheets containing 0.001% to 0.05% of P; and

    forming a nugget in an overlapped face of the plurality of the overlapping steel sheets, wherein the spot welded joint is formed by;

    performing a main energizing process with a current value Iw (kA) for energizing time tw (msec) while applying a welding pressure,after performing the main energizing process, performing a solidification process by retaining an energizing with a current value Is (kA) satisfying an Expression (1) for an energizing time ts (msec) satisfying an Expression (2) while maintaining the welding pressure, andafter performing the solidification process, performing a post energizing process with a current value Ip (kA) satisfying an Expression (3) for an energizing time tp (msec) satisfying an Expression (4), the energizing time tp being 60 msec or longer, wherein the Expressions comprise;


    0

    I
    s



    )1/2×

    I
    w



    (1),
    α

    2×

    {2×

    (Is2/Iw2)+1

    h≤

    t
    s



    α

    2×

    {2×

    (Is2/Iw2)+1

    h




    (2),
    Ip>

    0.8×

    I
    w



    (3), and
    Ip2×

    t
    p

    I
    w2×

    t
    w



    (4),where h is an average sheet thickness in terms of mm of the plurality of the overlapping steel sheets, and a is a nugget diameter (mm)/(h(mm))1/2.

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