Hot-working tool and manufacturing method therefor

Patent metadata

Field	Value
Publication number	US-10494688-B2
Application number	US-201615533550-A
Country	US
Kind code	B2
Filing date	Feb 2, 2016
Priority date	Feb 25, 2015
Publication date	Dec 3, 2019
Grant date	Dec 3, 2019

Abstract

Provided is a hot-working tool capable of maintaining adequate toughness even if the permissible amount of P contained in the hot-working tool is increased. The present invention is a hot-working tool, which has a component composition that can be adjusted to a martensitic structure by quenching and has a post-quenching and tempering martensitic structure, wherein: the component composition comprises greater than 0.020 mass % to 0.050 mass % of P; prior austenite grain diameter in said post-quenching and tempering martensitic structure is at least No. 9.5 in grain size number according to JIS-G-0551; and the P concentration of the grain boundary of said prior austenite particles is not more than 1.5 mass %. A hot-working tool wherein said component composition also comprises not more than 0.0250 mass % of Zn is preferable. The present invention also is a method for manufacturing a hot-working tool in which quenching and tempering are performed on a hot-working tool material with said component composition.

First claim

The invention claimed is:

1. A hot work tool having a quenched and tempered martensitic structure, the tool having a composition comprising, by mass,
0.30 to 0.50% of carbon,
not more than 2.00% of silicon,
not more than 1.50% of manganese,
more than 0.020% and not more than 0.050% of phosphorus,
not more than 0.0500% of sulfur,
3.00 to 6.00% of chromium,
one or both of molybdenum and tungsten in an amount of (Mo+½W): 0.50 to 3.50%,
0.10 to 1.50% of vanadium, and
0 to 1.00% of nickel,
0 to 1.00% of cobalt,
0 to 0.30% of niobium, and
the balance of iron and impurities,
wherein prior austenite crystal in the quenched and tempered martensitic structure has a grain size of not less than No. 9.5 as a grain size number pursuant to JIS-G-0551, and
wherein a phosphorus concentration at grain boundaries of the prior austenite crystal is not more than 1.5 mass %.

2. The hot work tool according to claim 1 , wherein the composition further includes not more than 0.0250 mass % of zinc.

3. The hot work tool according to claim 1 , wherein the carbon content is 0.34 to 0.50%.

4. A method for manufacturing a hot work tool having a martensitic structure, comprising subjecting a raw material to homogenizing treatment and solid forging to produce a steel material, subjecting the steel material to annealing to produce a hot work tool material, and quenching and tempering the hot work tool material having a composition comprising, by mass,
0.30 to 0.50% of carbon,
not more than 2.00% of silicon,
not more than 1.50% of manganese,
more than 0.020% and not more than 0.050% of phosphorus,
not more than 0.0500% of sulfur,
3.00 to 6.00% of chromium,
one or both of molybdenum and tungsten in an amount of (Mo+½W): 0.50 to 3.50%,
0.10 to 1.50% of vanadium, and
0 to 1.00% of nickel,
0 to 1.00% of cobalt,
0 to 0.30% of niobium, and
the balance of iron and impurities,
wherein the homogenizing treatment is performed at a temperature of 1200 to 1350° C. for not less than 10 hours,
wherein the solid forging is performed with a processing ratio of not less than 7S,
wherein prior austenite crystal in the quenched and tempered martensitic structure has a grain size of not less than No. 9.5 as a grain size number pursuant to JIS-G-0551, and
wherein a phosphorus concentration at grain boundaries of the prior austenite crystal is not more than 1.5 mass %.

5. The method according to claim 4 , wherein the composition of the material further includes not more than 0.0250 mass % of zinc.

6. The method according to claim 4 , wherein the carbon content is 0.34 to 0.50%.

Assignees

• Hitachi Metals Ltd

Inventors

• Nakano Yousuke

Classifications

• C21D8/00 Primary

  Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02) · CPC title

• C22C38/002

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title

• B21D37/01

  Selection of materials · CPC title

• C22C38/02

  containing silicon · CPC title

• C21D6/005

  containing Mn · CPC title