Abstract: This hot work tool steel has a composition containing C: 0.45 to 0.57 mass %, Si: 0.05 to 0.30 mass %, Mn: 0.45 to 1.00 mass %, Cr: 4.5 to 5.2 mass %, Ni: 0.5 mass % or less, Mo+(½) W: 1.0 to 2.0 mass %, V: 0.30 to 0.80 mass %, and N: 0.008 to 0.025 mass %, the remainder being Fe and unavoidable impurities, and the area ratio of carbide having an equivalent circle diameter of 1 ?m or less being 20% or higher. It is thereby possible to improve thermal conductivity to thereby shorten cycle time, and improving hardness after heat treatment to improve abrasion resistance while sufficient hardenability is maintained. Consequently, it is possible to obtain a hot work tool steel having excellent toughness with high hardness, excellent corrosion resistance, and minimal degradation of machinability.

Abstract: This hot work tool steel has a composition containing C: 0.45 to 0.57 mass %, Si: 0.05 to 0.30 mass %, Mn: 0.45 to 1.00 mass %, Cr: 4.5 to 5.2 mass %, Ni: 0.5 mass % or less, Mo+(½) W: 1.0 to 2.0 mass %, V: 0.30 to 0.80 mass %, and N: 0.008 to 0.025 mass %, the remainder being Fe and unavoidable impurities, and the area ratio of carbide having an equivalent circle diameter of 1 ?m or less being 20% or higher. It is thereby possible to improve thermal conductivity to thereby shorten cycle time, and improving hardness after heat treatment to improve abrasion resistance while sufficient hardenability is maintained. Consequently, it is possible to obtain a hot work tool steel having excellent toughness with high hardness, excellent corrosion resistance, and minimal degradation of machinability.

Abstract: The present invention relates to a cold-work die steel, comprising by mass %: 0.5 to 0.7% of C; 0.5 to 2.0% of Si; 0.1 to 2.0% of Mn; 5 to 7% of Cr; 0.01 to 1.0% of Al; 0.003 to 0.025% of N; 0.25 to 1% of Cu; 0.25 to 1% of Ni; 0.5 to 3% of Mo; 2% or less (including 0%) of W; and 0.1% or less (excluding 0%) of S, with a remainder being iron and an unavoidable impurity; wherein the following requirements (1) to (3) are satisfied: (1) [Cr]×[C]?4; (2) [Al]/[N]: 1 to 30; and (3) [Mo]+0.5×[W]: 0.5 to 3.00%, wherein the bracket means a content (%) of an element written therein.

Abstract: The present invention provides a cold-work die steel useful as a material of dies for cold pressing, which has basic properties such as hardness, toughness and dimensional change by heat treatment, and besides, which causes no problem in terms of machined surface roughness and cutting tool life, and also its dies for cold pressing. The invention relates to a cold-work die steel comprising: 0.5 to 0.7 mass % of C; 5.0 to 7.0 mass % of Cr; 0.5 to 2.0 mass % of Si; 0.1 to 2.0 mass % of Mn; 0.001 to 0.010 mass % of Al; 0.25 to 1.00 mass % of Cu; 0.25 to 1.00 mass % of Ni; 0.5 to 3.0 mass % of Mo+0.5×W; 0.5 mass % or less of V; 0.05 mass % or less of P; 0.1 mass % or less of S; 0.005 mass % or less of O, wherein the following requirements are satisfied: [C]×[Cr]?4; FP=[Si]/5+[Cr]/5+2×[Mo]+[W]+2×[V]+10×[Al]?5.0; and AP=[Mn]+3×([Cu]+[Ni])?2.5, and also relates to a die for cold pressing which is manufactured by using the cold-work die steel.

Abstract: The invention relates to a cold work die steel containing, by mass %, C: 0.20 to 0.60%, Si: 0.5 to 2.00%, Mn: 0.1 to 2%, Cr: 3.00 to 9.00%, Al: 0.3 to 2.0%, Cu: 1.00 to 5%, Ni: 1.00 to 5%, Mo: 0.5 to 3% and/or W: 2% or less (including 0%), S: 0.10% or less (not including 0%), in which the following requirements (1) to (3) are satisfied {wherein each square bracket [ ] means a content (%) of each element}: [Cr]×[C]?3.00,??(1) [Cu]/[Ni]:0.5 to 2.2,??(2) [Mo]+0.5×[W]:0.5 to 3.0%,??(3) with the remainder being iron and unavoidable impurities; and to a die obtained by the using the same. The invention also relates to a production method for a cold work die steel.