STEEL PLATE PUNCHING TOOL AND PUNCHING METHOD

摘要

In order to promote the utilization of thin high-strength steel plates in car parts to make cars more lightweight, the present invention improves the expandability of holes punched in the thin high-strength steel plates. Provided are a punching tool to be used in a punching step for forming a steel plate, which is the material to be worked, in a specified external form using a die and a punch with an attached protrusion, and a punching method and a molding method using same. The punching tool is characterized in that the radius of curvature (Rd) of the die cutting edge is 0.03 mm to 0.2 mm, and the angle (α) formed between a tangent line drawn from the punch cutting edge to the shoulder of the protrusion and the direction orthogonal to the direction of punch movement is 12° to 72°. Moreover, when the die cutting edge (rounded shoulder portion) is configured as a two-level rounded portion with radii of curvature (R1, R2) and the slope of a straight line passing through the centers of (R1) and (R2) is (β), expandability of the punched hole can be further improved by making 0.03 mm ≤ (R1) ≤ 0.2 mm, 1 ≤ (R2)/(R1) ≤ 5, 0 ≤ (R2(1-sin(β1)) ≤ 0.3t, and 30° ≤ (β) ≤ 90°.