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AssigneeNippon Steel & Sumitomo Metal Corporation
InventorsYuzo Takahashi, Osamu Kawano, Tatsuo Yokoi, Junji Haji, Satoshi Horioka
Estimating the term…
Punching hole expandability of high strength thin-gauge steel sheet is improved for the purpose of application of high strength thin-gauge steel sheet to auto parts so as to lighten the weight of automobiles. Tooling used in a punching process which uses a die and projecting punch to form a worked material of steel sheet into a predetermined outer shape, in which tooling for punching, a radius of curvature Rd of a die cutting edge is from 0.03 mm to 0.2 mm and an angle (α) formed by a tangent drawn from a punch cutting edge to a projection shoulder and a direction perpendicular to a direction of movement of the punch is from 12° to 72°, and a punching method and shaping method using the same, are provided. Further, when making the die cutting edge (shoulder R part) a two-stage R of radii of curvature R1 and R2 and making a slant of a line passing through the centers of R1 and R2 β, by making 0.03 mm≦R1≦0.2 mm, 1≦R2/R1≦5, 0≦R2(1−sin β1)≦0.3t, and 30°≦β≦90°, punching hole expandability can be improved.
Tooling for punching a steel sheet comprised of at least a die, a sheet holder, and a projecting punch, in which tooling for punching a steel sheet, in a cross-section parallel to a direction of movement of the punch and vertical to a ridgeline formed by a cutting edge of the punch or die, the radius of curvature R of a shoulder forming the cutting edge of the die is from 0.03 mm to 0.2 mm and an angle α formed by a line drawn from the shoulder forming the cutting edge of the punch to the shoulder of the projection and a direction perpendicular to the direction of movement of the punch is from 12° to 72°.
A method of punching a steel sheet using tooling for punching comprised of at least a die, a sheet holder, and a projecting punch, in which method of punching a steel sheet, in a cross-section parallel to a direction of movement of the punch and vertical to a ridgeline formed by a cutting edge of the punch or die, the radius of curvature R of a shoulder forming the cutting edge of the die is from 0.03 mm to 0.2 mm and an angle α formed by a line drawn from the shoulder forming the cutting edge of the punch to the shoulder of the projection and a direction perpendicular to the direction of movement of the punch is from 12° to 72°.
Dependencies are inferred from the claim text.