High strength steel pipe for reinforcing door of car
AssigneesKabushiki Kaisha Kobe Seiko Sho, Sango Co., Ltd.
InventorsHidenori Shirasawa, Yoshiki Tanaka, Shinji Sawaki
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Abstract
Herein described is a high strength steel pipe for reinforcing doors of a car, comprising a steel pipe made by seam-welding a steel sheet, wherein a ratio (Hv.sub.1 /Hv.sub.2) of a minimum hardness in a softened area of a weld affected zone to an average hardness in a base material satisfies the following formula, -0.001.sigma.B+1.05.gtoreq.Hv.sub.1 /Hv.sub.2 .gtoreq.-0.003.sigma.B+1.05 wherein .sigma.B: tensile strength (kgf/mm.sup.2) and Hv.sub.1, Hv.sub.2 : Vickers hardness and a ratio (.sigma.y/.sigma.B) of a yield strength .sigma.y to a tensile strength .sigma.B of a steel pipe is 0.7 or more.
Claims6
A high strength steel pipe for reinforcing doors of a car, comprising a steel pipe made by seam-welding a steel sheet, wherein a ratio (Hv.sub.1 /Hv.sub.2) of a minimum hardness in a softened area of a weld affected zone to an average hardness in a base material satisfies the following formula,
- -0.001.sigma.B+1.05.gtoreq.Hv.sub.1 /Hv.sub.2.gtoreq.- 0.003.sigma.B+1.05
- wherein
- .sigma.B:
- tensile strength (kgf/mm.sup.2) and
- Hv.sub.1, H.sub.2 :
- Vickers hardness
- and a ratio (.sigma.y/.sigma.B)of a yield strength .sigma.y to a tensile strength .sigma.B of a steel pipe is 0.7 or more.
In a door of a car incorporated with a steel pipe as a reinforcing member inside a door main body, said steel pipe comprising a steel pipe made by seam-welding a steel sheet, wherein a ratio (Hv.sub.1 /Hv.sub.2) of a minimum hardness Hv.sub.1 in a softened area of a weld affected zone to an average hardness Hv.sub.2 in a base material satisfies the following formula,
- -0.001.sigma.B+1.05.gtoreq.Hv.sub.1 /H.sub.2.gtoreq.- 0.003.sigma.B+1.05
- wherein
- .sigma.B:
- tensile strength (kgf/mm.sup.2) and
- Hv.sub.1, Hv.sub.2 :
- Vickers hardness
- and a ratio (.sigma.y/.sigma.B) of a yield strength .sigma.y to a tensile strength .sigma.B of a pipe is 0.7 or more.
Dependencies are inferred from the claim text.