Patent ID: 8758901
Filing Date: 2014-06-24
Classification: B23K,C21D,C22C,Y10T

Abstract:
1. An ultrahigh-strength welded joint with a tensile strength of 1138 MPa or more and an absorbed energy in a 2 mm V-notch Charpy impact test at −40° C. (vE-40) of 27 J/cm 2 or more, comprising a steel plate having a plate thickness of 4 mm to 12 mm and including a weld metal with an almost full martensite structure, wherein, in a cross-section of the welded joint in a direction perpendicular to a welding direction, a cross-sectional shape of the weld metal has a width W 1 at a surface of the steel plate and a width W 2 at a position which is separated from the surface by three-quarters of the plate thickness, the width W 1 being 2.0 mm to 7.0 mm and the width W 2 being 0.5 mm to 2.4 mm, and wherein the weld metal comprises, by mass %, wherein a carbon equivalent (Ceq) as defined by equation (1) is 0.40% to 1.00%, a value Y as defined by equation (2) is 0.07% to 0.20%, and a balance of the weld metal is constituted by unavoidable impurities and Fe: wherein in equations (1) and (2), elements with “[ ]” represent contents (mass %) of respective elements.