Cold working tool material and cold working tool manufacturing method

Patent metadata

Field	Value
Publication number	US-10407747-B2
Application number	US-201615566812-A
Country	US
Kind code	B2
Filing date	Dec 27, 2016
Priority date	Mar 18, 2016
Publication date	Sep 10, 2019
Grant date	Sep 10, 2019

Abstract

Provided are a cold working tool material with which high hardness can be obtained in a broad range of tempering temperatures, and a cold working tool manufacturing method using same. The present invention is a cold working tool material comprising a steel component composition that contains, in mass %, C: 0.65-2.40%, Cr: 5.0-15.0%, Mo and W alone or combined (Mo+½W): 0.50-4.00%, V: 0.10-1.50%, and N: greater than 0.0300% to 0.0800%, in which martensitic structure can be adjusted by quenching, and in which, in a 90 μm long 90 μm wide region of a cross-sectional structure that does not contain carbides with equivalent circle diameters exceeding 5.0 μm, the number density of carbides A with equivalent circle diameters greater than 0.1 μm to 2.0 μm is at least 9.0×105/mm2 and the number density of carbides B with equivalent circle diameters greater than 0.1 μm to 0.4 μm is at least 7.5×105/mm2. The present invention is also a cold working tool manufacturing method in which quenching and tempering are performed on said cold working tool material.

First claim

The invention claimed is:

1. A cold work tool material having a steel composition including, by mass %, C: 0.65% to 2.40%, Cr: 5.0% to 15.0%, Mo and W alone or in combination in an amount of (Mo+½W): 0.50% to 4.00%, V: 0.10% to 1.50%, N: more than 0.0300% and not more than 0.0800%, Si: not more than 2.00%, Mn: not more than 1.50%, P: not more than 0.050%, S: not more than 0.0500%, Ni: 0% to 1.00%, Nb: 0% to 1.50%, Cu: 0% to 0.25%, and the balance being Fe and impurities,
wherein the material includes a cross sectional region of a structure, the region having a length of 90 μm and a width of 90 μm and including no carbides having an equivalent circular diameter exceeding 5.0 μm, and
wherein, in the cross sectional region, a number density of carbides A having an equivalent circular diameter of more than 0.1 μm and not more than 2.0 μm is not less than 9.0×10 5 /mm 2 , and a number density of carbides B having an equivalent circular diameter of more than 0.1 μm and not more than 0.4 μm is not less than 7.5×10 5 /mm 2 .

2. The cold work tool material according to claim 1 , wherein a proportion of the number of the carbides B to the number of the carbides A is not less than 65.0% in the cross sectional region.

3. A method of manufacturing a cold work tool, comprising a step of quenching and tempering the cold work tool material according to claim 1 .

4. A method of manufacturing a cold work tool, comprising a step of quenching and tempering the cold work tool material according to claim 2 .

Assignees

• Hitachi Metals Ltd

Inventors

• Shouji Tatsuya
• Mishima Setsuo
• Shinji Yukio
• Kuroda Katsufumi

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

• C22C38/60

  containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur · CPC title

• C22C38/36

  with more than 1.7% by weight of carbon · CPC title

• C21D9/00

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

• C21D6/00

  Heat treatment of ferrous alloys · CPC title