US 12,434,327 B2
Friction stir spot welded joint and production method therefor, and friction stir spot welding method
Daiki Yamagishi, Tokyo (JP); Katsutoshi Takashima, Tokyo (JP); Hiroshi Matsuda, Tokyo (JP); Ryoji Ohashi, Kobe (JP); Yoshitaka Muramatsu, Kobe (JP); and Takuya Fukuda, Kobe (JP)
Assigned to JFE STEEL CORPORATION, Tokyo (JP); and KAWASAKI JUKOGYO KABUSHIKI KAISHA, Hyogo (JP)
Appl. No. 18/683,248
Filed by JFE STEEL CORPORATION, Tokyo (JP); and KAWASAKI JUKOGYO KABUSHIKI KAISHA, Kobe (JP)
PCT Filed Jul. 21, 2022, PCT No. PCT/JP2022/028411
§ 371(c)(1), (2) Date Feb. 13, 2024,
PCT Pub. No. WO2023/032515, PCT Pub. Date Mar. 9, 2023.
Claims priority of application No. 2021-141900 (JP), filed on Aug. 31, 2021.
Prior Publication US 2025/0065438 A1, Feb. 27, 2025
Int. Cl. B23K 20/12 (2006.01); B32B 7/05 (2019.01); B32B 15/01 (2006.01); B23K 103/04 (2006.01)
CPC B23K 20/1265 (2013.01) [B23K 20/1225 (2013.01); B23K 20/1255 (2013.01); B32B 7/05 (2019.01); B32B 15/011 (2013.01); B23K 2103/04 (2018.08); B32B 2250/02 (2013.01); B32B 2311/30 (2013.01)] 6 Claims
OG exemplary drawing
 
1. A friction stir spot welded joint comprising:
two or more overlapping steel sheets;
a welded portion of the steel sheets; and
an annular groove on an upper surface of the welded portion,
wherein at least one of the steel sheets has a soft surface layer,
the welded portion includes a recess, a first flow portion adjacent to the recess, a second flow portion adjacent to the first flow portion, and a welding interface that is a boundary between the first flow portion and the second flow portion,
a vertical position of a deepest point of the recess satisfies at least one of −0.5 mm or less and −TL×0.50 or less, with a lower mating surface of the steel sheets as a reference position,
a vertical position of a highest point of the welding interface is +TU×0.50 or more, with an upper mating surface of the steel sheets as a reference position,
at a vertical position: +TU×0.50 or +TU×0.60, a difference between a hardness at a position of the welding interface and a hardness at a position that is (the position of the welding interface+350 μm) in horizontal position is 80 HV or less,
the two or more overlapping steel sheets include an upper sheet and a lower sheet that are respectively a steel sheet located at a top and a steel sheet located at a bottom,
TU is a thickness in mm of the upper sheet,
TL is a thickness in mm of the lower sheet,
the upper mating surface is a mating surface between the upper sheet and a steel sheet adjacent to the upper sheet,
the lower mating surface is a mating surface between the lower sheet and a steel sheet adjacent to the lower sheet, and
the vertical position is + when above the reference position and is − when below the reference position, and the horizontal position is a distance from a reference position.