SPOT WELDED JOINT AND METHOD FOR MANUFACTURING SPOT WELDED JOINT

WIPO Patent Application WO/2023/234391

A1

A spot welded joint according to one embodiment of the present disclosure comprises a first steel plate, a second steel plate, and a spot-welding portion joining the first steel plate and the second steel plate. The first steel plate and the second steel plate directly overlap each other. The tensile strength of the first steel plate is 1500 MPA or greater. The tensile strength of the second steel plate is equal to less than the tensile strength of the first steel plate. The Vickers hardness of the first steel plate from a surface thereof to a depth of 20 μm is 95% or less of the Vickers hardness of the first steel plate at a position at 1/4 the plate thickness of a base material portion. The carbon equivalent Ceq of the base material portion of the first steel plate is 0.22% or greater, and HC = Ceq × TS2 × (1 - (TS2 × t2 3 / (TS1 × t1 3)) / √t2 is 170 or greater. The spot-welding portion includes a nugget and a pressure-welding portion that joins the first steel plate and the second steel plate at the periphery of the nugget. The Vickers hardness at 20 μm on the first steel plate side of an outer peripheral end portion of the pressure-welding portion is Hv 50 or more lower than the Vickers hardness of the first steel plate at the position of 1/4 the plate thickness of the base material portion.

OKADA TOHRU (JP)
AZUMA MASAFUMI (JP)
NISHIO TAKUYA (JP)
FURUSAKO SEIJI (JP)

PCT/JP2023/020489

December 07, 2023

June 01, 2023

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NIPPON STEEL CORP (JP)

B23K11/16; B23K11/11

WO2014171495A1

2014-10-23

JP2016209919A	2016-12-15
JP2009001839A	2009-01-08
JP2001009573A	2001-01-16

MATSUNUMA Yasushi et al. (JP)

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