# US 10,119,174 B2 · Hot work tool material and method for manufacturing hot work tool

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- Number: US 10,119,174 B2
- Document ID: US10119174B2
- Status: Granted
- Kind: B2
- Application number: 15/114,604
- Filed: 2015-05-26
- Published: 2016-12-01
- Granted: 2018-11-06
- Earliest claimed: 2014-05-28
- Assignees: Hitachi Metals, Ltd.
- Applicants: Hitachi Metals, Ltd.
- Inventors: Yousuke Nakano
- Web page: https://patentgrep.com/patent/US10119174B2

## CPC

- C21D 9/0068: {for particular articles not mentioned below}
- C21D 1/18: Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62)
- C21D 1/25: Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
- C21D 6/002: {containing Cr (C21D6/004 takes precedence)}
- C21D 6/005: {containing Mn}
- C21D 6/008: {containing Si}
- C21D 7/13: by hot working
- C22C 38/001: {containing N}
- C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60}
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/06: containing aluminium
- C22C 38/20: with copper
- C22C 38/22: with molybdenum or tungsten
- C22C 38/24: with vanadium
- C21D 2211/001: Austenite
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

Provided are a hot work tool material having an annealed structure effective for producing a finer quenched and tempered structure when made into a hot work tool, and a method for manufacturing a hot work tool. A hot work tool material which has an annealed structure and which is used upon being quenched and tempered, wherein the hot work tool material has a composition that can be adjusted to a martensite structure by the aforementioned quenching, and ferrite grains in a cross-section of the annealed structure of the hot work tool material have, in an oversize cumulative distribution based on the cross-sectional area of the ferrite grains, a grain diameter distribution such that the grain diameter is 25 μm or less as a circle equivalent diameter when the cumulative cross-sectional area is 90% of the total cross-sectional area. In addition, a method for manufacturing a hot work tool in which quenching and tempering is performed on the aforementioned hot work tool material.

## Claims

### Claim 1

A hot work tool material having an annealed structure and a composition consisting of, by mass %:
C: 0.30% to 0.50%,
Si: not greater than 2.00%,
Mn: not greater than 1.50%,
P: not greater than 0.0500%,
S: not greater than 0.0500%,
Cr: 3.00% to 6.00%,
one or both of Mo and W in an expression of (Mo+½ W): 0.50% to 3.50%,
V: 0.10% to 1.50%,
Ni: 0% to 1.00%,
Co: 0% to 1.00%,
Nb: 0% to 0.30%, and
the balance of Fe and impurities,
wherein the annealed structure comprises ferrite grains in a cross-sectional structure, the ferrite grains having, in an oversize cumulative distribution based on a cross-sectional area of the ferrite grains, a grain diameter distribution such that the grain diameter is not greater than 25 μm as a circle equivalent diameter when the cumulative cross-sectional area is 90% of the total cross-sectional area.

### Claim 2 (depends on 1)

A method for manufacturing a hot work tool, comprising quenching and tempering the hot work tool material according to claim 1.

### Claim 3 (depends on 2)

The method according to claim 2, wherein a prior austenite grain size number in the structure of the hot work tool after the quenching and tempering is not less than No. 9 as a grain size number pursuant to JIS-G-0551.