# US 11,306,377 B2 · High strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation and manufacturing method thereof

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- Number: US 11,306,377 B2
- Document ID: US11306377B2
- Status: Granted
- Kind: B2
- Application number: 16/314,396
- Filed: 2017-07-06
- Published: 2019-10-24
- Granted: 2022-04-19
- Earliest claimed: 2016-07-06
- Assignees: Magang (Group) Holding Co., Ltd.; Maanshan Iron & Steel Co., Ltd.
- Applicants: Nmagang (Group) Holding Co., Ltd.; Maanshan Iron & Steel Co., Ltd.
- Inventors: Mingru Zhang; Zheng Fang; Feng Zhang; Chaohai Yin; Yumei Pu; Zhiyuan Cheng; Hai Zhao
- Web page: https://patentgrep.com/patent/US11306377B2

## CPC

- C22C 38/16: containing copper
- C21D 1/18: Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62)
- C21D 9/0062: {Heat-treating apparatus with a cooling or quenching zone}
- C21D 9/34: for tyres; for rims
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/08: containing nickel {(C22C38/105 takes precedence)}
- C21D 2211/001: Austenite
- C21D 2211/002: Bainite
- C21D 2211/005: Ferrite
- C22C 2202/00: Physical properties
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- 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

The present invention provides a high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation and a manufacturing method thereof. Components are: carbon 0.10-0.40%, silicon 1.00-2.00%, manganese 1.00-2.50%, copper 0.20-1.00%, boron 0.0001-0.035%, nickel 0.10-1.00%, phosphorus ≤0.020%, and sulphur ≤0.020%, where the remaining is iron and unavoidable residual elements, 1.50%≤Si+Ni≤3.00%, and 1.50%≤Mn+Ni+Cu≤3.00%. Compared with the prior art, in the present invention, by using design of the chemical compositions of steel and wheel manufacturing processes, especially a heat treatment process and technology, a rim of the wheel obtains a carbide-free bainite structure, and a web and a wheel hub obtain a metallographic structure based on granular bainite and a supersaturated ferritic structure. The wheel has comprehensive mechanical properties such as high strength, high toughness, heat-cracking resistant performance and good service performance, thereby improving a service life and comprehensive efficiency of the wheel, bringing specific economic and social benefits.

## Claims

### Claim 1

A bainite steel wheel for rail transportation, comprising:
carbon C: 0.15-0.25%;
silicon Si: 1.40-1.80;
manganese Mn: 1.40-2.00%;
copper Cu: 0.20-0.80%;
boron B: 0.0003-0.005%;
nickel Ni: 0.10-0.60%;
phosphorus P≤0.020%; and
sulphur S≤0.020%;
wherein the remaining is iron and unavoidable residual elements;
wherein 1.50%≤Si+Ni≤3.00%, and 1.50%≤Mn+Ni+Cu≤3.00%;
wherein the portion of the bainite steel wheel that is between the surface of a rim tread and 40 millimeters below the rim tread is organized into a microstructure of a carbide-free bainite structure, wherein the carbide-free bainite structure comprises a supersaturated lath ferrite in nanometer scale, wherein a film-shaped carbon-rich residual austenite in nanometer scale is interspersed among the supersaturated lath ferrite, and wherein a volume percentage of the residual austenite is 4%-15%; and
wherein the microstructure of the bainite steel wheel was formed by the steps of smelting, refining, molding, and heat treatment processes, wherein the heat treatment process comprises heating a molded wheel to austenite temperature by heating to 860-930° C. and maintaining at the temperature for 2.0-2.5 hours, intensively cooling a rim tread with a water spray to a temperature below 400° C., and performing tempering treatment.

### Claim 2 (depends on 1)

The bainite steel wheel for rail transportation according to claim 1, comprising:
carbon C: 0.18%;
silicon Si: 1.63%;
manganese Mn: 1.95%;
copper Cu: 0.21%;
boron B: 0.001%;
nickel Ni: 0.18%;
phosphorus P: 0.012%; and
sulphur S: 0.008%.

### Claim 3 (depends on 1)

The bainite steel wheel for rail transportation according to claim 1, wherein the microstructure is a multiphase structure formed by the supersaturated lath ferrite and the carbon-rich residual austenite, and a size of the nanometer scale ranges from 1-999 nm.

### Claim 4 (depends on 1)

The bainite steel wheel for rail transportation according to claim 1, wherein a tempering treatment is as follows: performing tempering at medium or low temperature for more than 30 minutes when the temperature of the wheel is less than 400° C., and air cooling the wheel to room temperature after the tempering; or intensively cooling the rim tread with the water spray to the temperature below 400° C., and air cooling to room temperature, during which self-tempering is performed by using waste heat.

### Claim 5 (depends on 1)

The bainite steel wheel for rail transportation according to claim 1, wherein the heat treatment process comprises: heating treatment of the wheel with high-temperature waste heat after the molding, and directly intensively cooling a rim tread of a molded wheel with a water spray to a temperature below 400° C., and performing tempering treatment.