# US 11,441,201 B2 · Sucker rod steel and manufacturing method therefor

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- Number: US 11,441,201 B2
- Document ID: US11441201B2
- Status: Granted
- Kind: B2
- Application number: 16/321,287
- Filed: 2017-08-25
- Published: 2019-06-06
- Granted: 2022-09-13
- Earliest claimed: 2016-08-30
- Assignees: Baoshan Iron & Steel Co., Ltd.
- Applicants: Baoshan Iron & Steel Co., Ltd.
- Inventors: Xiangjiang Liu; Zongze Huang
- Web page: https://patentgrep.com/patent/US11441201B2

## CPC

- C21D 9/0075: {for rods of limited length (of unlimited length C21D9/52)}
- C21D 1/18: Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62)
- C21D 1/58: Oils
- C21D 6/002: {containing Cr (C21D6/004 takes precedence)}
- C21D 6/005: {containing Mn}
- C21D 6/008: {containing Si}
- C22C 38/001: {containing N}
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/06: containing aluminium
- C22C 38/22: with molybdenum or tungsten
- C22C 38/26: with niobium or tantalum
- C21D 2211/004: Dispersions; Precipitations
- C21D 2211/008: Martensite
- Y02P 10/25: Process efficiency
- 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)
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

A sucker rod steel, a heat treatment process therefor, and a manufacturing method comprising the heat treatment process are provided. The sucker rod steel comprises, in mass percent, the following chemical elements: C: 0.10˜0.20%, Si: 0.40˜0.80%, Mn: 0.20˜0.60%, Mo: 0.36˜0.46%, Cr: 6.15˜7.10%, Al: 0.015˜0.035%, Nb: 0.02˜0.06%, and N: 0.008˜0.015%, with the balance being Fe and other inevitable impurities. The microstructure of the sucker rod steel is tempered martensite and nanoscale precipitates. The grain size is higher than grade 10, the tensile strength is 920˜1320 Mpa, and the AKU2 impact energy is greater than or equal to 180 J.

## Claims

### Claim 1

A sucker rod steel, comprising the following chemical elements in mass percent: C: 0.10˜0.20%, Si: 0.40˜0.80%, Mn: 0.20˜0.60%, Mo: 0.36˜0.46%, Cr: 6.15˜6.97%, Al: 0.015˜0.035%, Nb: 0.02˜0.06%, and N: 0.008˜0.015%, with the balance being Fe and other inevitable impurities, wherein the microstructure of the sucker rod steel is tempered martensite and nanoscale precipitates and the precipitates include carbonitrides of Cr and Fe, wherein the sucker rod steel has a tensile strength of 920˜1320 MPa.

### Claim 2 (depends on 1)

The sucker rod steel according to claim 1, wherein the nanoscale precipitates comprise granular precipitates.

### Claim 3 (depends on 2)

The sucker rod steel according to claim 2, wherein the granular precipitates have a particle size of 10˜20 nm.

### Claim 4 (depends on 2)

The sucker rod steel according to claim 2, wherein the granular precipitates comprise carbonitrides of Cr, Mn and Nb.

### Claim 5 (depends on 1)

The sucker rod steel according to claim 1, wherein the carbonitrides of Cr and Fe are rod-shaped.

### Claim 6 (depends on 5)

The sucker rod steel according to claim 5, wherein the precipitates have a length of 60˜80 nm and a width of 10˜20 nm.

### Claim 7 (depends on 1)

The sucker rod steel according to claim 1, wherein the sucker rod steel has a grain size of higher than grade 10.

### Claim 8 (depends on 1)

The sucker rod steel according to claim 1, wherein the sucker rod steel has an AKU2 of 180 J or more.

### Claim 9 (depends on 1, 2, 3, 4, 5, 6, 7, 8)

A heat treatment process of the sucker rod steel according to any one of claims 1 to 6, 7 and 8, comprising the steps of:
induction hardening: passing the sucker rod steel through an intermediate frequency induction heater to heat the sucker rod steel to 850˜950° C. and keep for a holding time of 1˜5 min, and then cooling the sucker rod steel by oil quenching at an oil temperature of 20˜50° C.;
induction tempering: passing the sucker rod steel through an intermediate frequency induction heater to heat the sucker rod steel to 520˜650° C. and keep for a holding time of 1.5˜5 min, and then air cooling the sucker rod steel to room temperature.

### Claim 10 (depends on 9)

The heat treatment process according to claim 9, wherein, in the step(s) of the induction hardening and/or the induction tempering, passing the sucker rod steel through an intermediate frequency induction heater with a frequency of 20˜30 KHz at a speed of 0.5˜1 m/min.

### Claim 11 (depends on 9)

A method for manufacturing sucker rod steel, comprising the heat treatment process according to claim 9.

### Claim 12 (depends on 10)

A method for manufacturing sucker rod steel, comprising the heat treatment process according to claim 10.