Abstract: A martensitic stainless alloy comprising, in percent by weight (wt. %) C >0.50 to 0.60; Si 0.10 to 0.60, Mn 0.40 to 0.80; Cr 13.50 to 14.50; Ni 0 to 1.20; Mo 0.80 to 2.50; N 0.050 to 0.12; Cu 0.10 to 1.50; V max 0.10; S max 0.03; P max 0.03; the balance being Fe an unavoidable impurities.

Abstract: The steel punch knife according to the invention is suitable for punching out parts of any shape from paper, cardboard, paperboard, corrugated board, plastics sheets, leather rubber and the like, and comprises a knife body (4) with a cutting edge (2) at one end and a deformable back portion (3) opposite the cutting edge (2). The cutting edge (2) is harder than at least a portion of the back portion (3). The back portion (3) comprises a V-shaped back edge (3b) having two inclined sides defining an inclination angle between them. The maximum width of the back edge (3b), at the base thereof, is smaller than the width of the knife body (4), such that there is a shoulder (9) where the back edge (3b) meets the knife body (4).