To prevent generation of flaws by providing a steel slab with an arc-shaped groove bottom side of a roll hole and a straight flange side of the side surface of the roll, and punching a hole.
Preferably, in this press roll punching method, the height H of a material in the vertical direction of a steel slab is set to satisfy the inequalities of Hmin ≤H ≤Hmax, and the ratio W/D of the width W of the material in the right-to-left direction of the steel slab to the outside diameter D of a stock tube after the punching is set to satisfy the inequalities of 0.72≤W/D≤0.86, wed the drawing ratio λ, is set to satisfy the inequalities 1.1≤λ≤1.35. Hmax is 0.67 (Rg+D/2) (where, Rg is the radius of the roll at a center part of a roll groove bottom, Lp, is the distance from a part immediately below the roll to a tip of m plug, ad D is the outside diameter of the stock tube), and λ is expressed by Ai/Ao (where, Ai is the sectional area of the steel slab before the punching, and Ao is the sectional area of the hollow stock tube after the punching). Generation of flaws in the outer surface in the case of punching the stainless steel is considerably reduced, the quality and yield are improved, and repairs of the flaws are reduced.
MARUYAMA KAZUSHI
KOSHO KOICHI
ISHIBASHI SEIJI
