# US 6,294,031 B1 · Production method of a heat-treated steel member

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- Number: US 6,294,031 B1
- Document ID: US6294031B1
- Status: Granted
- Kind: B1
- Application number: 09/148,707
- Filed: 1998-09-04
- Granted: 2001-09-25
- Earliest claimed: 1997-09-05
- Assignees: Topy Kogyo Kabushiki Kaisha
- Inventors: Hiroyuki Takeno; Masahiro Nakajima; Kiyokazu Niwa; Go Morishima; Daigo Sugiyama
- Web page: https://patentgrep.com/patent/US6294031B1

## CPC

- C21D 1/18: Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62)
- C21D 9/0068: {for particular articles not mentioned below}
- C21D 9/0087: {for chains, for chain links}
- C21D 2211/008: Martensite
- C21D 2221/10: Differential treatment of inner with respect to outer regions, e.g. core and periphery, respectively
- 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)

## Abstract

A production method of a heat-treated steel member includes the steps of: shaping a steel material of low-carbon boron steel containing about 0.05-0.30% carbon by weight into a predetermined configuration to bc a shaped material; and heat-treating the shaped material, said heat-treating, includes quench-hardening only.

## Claims

### Claim 1

A method of producing a heat-treated steel member selected from any one of a shoe, a bushing, a link, and a pin used for an endless track mounted to a construction vehicle, and a cutting edge of a blade used for a construction vehicle and a vehicle with a snow plow, said method comprising:
providing a steel member of low-carbon boron steel containing about 0.20-0.30% carbon by weight;
shaping said steel material to form a shaped material; and
quench-hardening said shaped material to form a low-carbon martensite microstructure close to a surface of said shaped material with a hardness of HRC 45 to 49, a tensile strength of 144 to 155 Kg/mm2, and a toughness of 7 to 10 Kg·m/cm2 Charpy impact value;
said quench-hardening including heating an entire thickness of said shaped material to above an Ac3 transformation temperature and then rapidly cooling said heated shaped material to below about 200° C. without tempering said shaped material subsequent to said quench-hardening.

### Claim 2 (depends on 1)

A method according to claim 1, wherein the low-carbon boron steel contains 0.20-0.26% carbon by weight.

### Claim 3 (depends on 1)

A method according to claim 1, wherein the low-carbon boron steel contains about 0.0001-0.0100% boron by weight.

### Claim 4 (depends on 1)

A method according to claim 1, wherein the low-carbon boron steel contains 0.0005-0.0030% boron by weight.

### Claim 5 (depends on 1)

A method according to claim 1, wherein the low-carbon boron steel contains about 0.80-1.10% manganese by weight.