Machine component

Patent metadata

Field	Value
Publication number	US-11332817-B2
Application number	US-201917046064-A
Country	US
Kind code	B2
Filing date	May 10, 2019
Priority date	Jun 18, 2018
Publication date	May 17, 2022
Grant date	May 17, 2022

Abstract

A machine component includes a core made up of a steel for machine structural use, and a medium carbon-containing layer and a high carbon-containing layer formed of the steel for machine structural use, the medium carbon-containing layer covering the core, the high carbon-containing layer covering the medium carbon-containing layer and having a carbon concentration of 0.8-1.5%. The high carbon-containing layer is made up of a martensitic structure having carbides dispersed therein and a residual austenitic structure, wherein spheroidized carbides with an aspect ratio of 1.5 or less constitute 90% or more of a total number of the carbides, and the number of spheroidized carbides on prior austenite grain boundaries is 40% or less of the total number of the carbides.

First claim

The invention claimed is:

1. A machine component comprising:
a core made up of a steel for machine structural use; and
a medium carbon-containing layer and a high carbon-containing layer formed of the steel for machine structural use, the medium carbon-containing layer covering the core, the high carbon-containing layer covering the medium carbon-containing layer and having a carbon concentration of 0.8-1.5%;
the steel for machine structural use containing, in mass %, 0.13-0.30% C, 0.15-0.80% Si, 0.20-0.90% Mn, 0.90-2.00% Cr, 0.020-0.050% Al, and 0.002-0.025% N, also containing, as impurities, 0.030% or less P and 0.030% or less S, further optionally containing, as a first group of selective optional components, one or more selected from among 0.10-2.00% Ni, 0.05-0.50% Mo, 0.01-0.10% Nb, and 0.01-0.20% V, and optionally containing, as a second group of optional components in addition to or in place of the first group of selective optional components, 0.01-0.05% Ti and 0.0010-0.0050% B, with the balance consisting of Fe and unavoidable impurities,
the high carbon-containing layer being made up of a martensitic structure having carbides dispersed therein and a residual austenitic structure, spheroidized carbides with an aspect ratio of 1.5 or less constituting 90% or more of a total number of the carbides, the number of spheroidized carbides on prior austenite grain boundaries being 40% or less of the total number of the carbides.

2. The machine component according to claim 1 , wherein 90% or more of the spheroidized carbides on the prior austenite grain boundaries have a particle size of 1 μm or less.

3. The machine component according to claim 1 , wherein the prior austenite grain boundaries provide a grain size of 15 μm or less.

4. The machine component according to claim 1 , wherein the high carbon-containing layer is formed at least from a surface to 0.3 mm in depth of the machine component.

5. The machine component according to claim 2 , wherein the prior austenite grain boundaries provide a grain size of 15 μm or less.

Assignees

• Komatsu Mfg Co Ltd

Inventors

• Sato Kensuke
• Yamamoto Koji
• Hiratsuka Yusuke
• Hashimoto Kazuya

Classifications

• C21D9/32 Primary

  for gear wheels, worm wheels, or the like · CPC title

• Y10T428/12972

  Containing 0.01-1.7% carbon [i.e., steel] · CPC title

• Y10T428/12771

  Transition metal-base component · CPC title

• C23C8/02

  Pretreatment of the material to be coated (C23C8/04 takes precedence) · CPC title

• C22C38/50

  with titanium or zirconium · CPC title