Steel for a mold and mold

Patent metadata

Field	Value
Publication number	US-11952640-B2
Application number	US-202318111381-A
Country	US
Kind code	B2
Filing date	Feb 17, 2023
Priority date	Feb 24, 2022
Publication date	Apr 9, 2024
Grant date	Apr 9, 2024

Abstract

The present invention relates to a steel for a mold including: on % by mass basis, 0.55%≤C≤0.70%; 0.30%≤Si≤0.60%; 0.55%≤Mn≤1.2%; 5.7%≤Cr≤6.9%; 1.2%≤Mo+W/2≤1.6%; 0.55%≤V≤0.79%; and 0.005%≤N≤0.1%, with the remainder being Fe and inevitable impurities including, Al≤0.020%, Ni≤0.20%, S≤0.0015%, and Cu≤0.10%, and satisfying P1≥24 and 4.9≤P2≤7.3, P1 and P2 being a value obtained based on the following formula (1) and (2), respectively, P1=45−13.6[Si]−7.0([Mo]+[W]/2)−12.9[Ni] (1), P2=7.4[V]+15.8[N]+38.6[Al] (2) in which [M] represents a content of an element M in % by mass basis, and relates to a mold including the steel for a mold.

First claim

What is claimed is:

1. A steel for a mold, having a composition consisting of, on % by mass basis:
0.55%≤C≤0.70%;
0.30%≤Si≤0.60%;
0.55%≤Mn≤1.2%;
5.7%≤Cr≤6.9%;
1.2%≤Mo+W/2≤1.6%;
0.55%≤V≤0.79%;
0.005%≤N≤0.1%,
Nb≤0.5%;
Zr≤0.5%;
Ta≤0.5%; and
Co≤1.0%,
with the remainder being Fe and inevitable impurities satisfying, on % by mass basis, Al≤0.020%, Ni≤0.20%, S≤0.0015%, and Cu≤0.10%, and
satisfying P1≥24 and 4.9≤P2≤7.3, P1 being a value obtained based on the following formula (1) and P2 being a value obtained based on the following formula (2),
P1=45−13.6[Si]−7.0([Mo]+[W]/2)−12.9[Ni]  (1)

P2=7.4[V]+15.8[N]+38.6[Al]  (2)

in the formulae (1) and (2), [M] represents a content of an element M in % by mass basis,
wherein in a state after quenching and tempering, the steel has a hardness at room temperature of 58 HRC or more and 61 HRC or less, and a thermal conductivity at room temperature of 20 W/(m·K) or more, and
in a state after quenching, the steel has a crystal grain size of 5 or more in terms of a grain size number defined in JIS G 0551:2020.

2. The steel for a mold according to claim 1 ,
further satisfying, on % by mass basis, at least one kind selected from the group consisting of:
0.01%≤Nb≤0.5%;
0.01%≤Zr≤0.5%; and
0.01%≤Ta≤0.5%.

3. The steel for a mold according to claim 1 , further satisfying, on % by mass basis, 0.10%≤Co≤1.0%.

4. The steel for a mold according to claim 1 , wherein in a state after quenching and tempering, the steel has a grain size of a crystallized carbide of less than 25 km.

5. A mold comprising the steel for a mold according to claim 1 .

6. The mold according to claim 5 , wherein the mold is a hot stamping mold.

7. The steel for a mold according to claim 1 , further satisfying, on % by mass basis, 0.55%≤C≤0.63%.

8. The steel for a mold according to claim 1 , further satisfying, on % by mass basis, 0.005%≤N≤0.0244%.

Assignees

• Daido Steel Co Ltd

Inventors

• Umemori Naoki
• Nemoto Toshifumi

Classifications

• C21D9/00 Primary

  Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor · CPC title

• C21D1/18

  Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62) · CPC title

• C21D6/004

  containing Cr and Ni · CPC title

• C21D6/005

  containing Mn · CPC title

• C21D6/007

  containing Co · CPC title