# US 10,865,457 B2 · Steel composition

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- Number: US 10,865,457 B2
- Document ID: US10865457B2
- Status: Granted
- Kind: B2
- Application number: 16/310,267
- Filed: 2017-06-16
- Published: 2019-11-07
- Granted: 2020-12-15
- Earliest claimed: 2016-06-17
- Assignees: Aubert & Duval
- Applicants: Aubert & Duval
- Inventors: Jacques Bellus; Atman Benbahmed; Johanna Andre; Fredrik Sandberg
- Web page: https://patentgrep.com/patent/US10865457B2

## CPC

- C21D 8/00: 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)
- C21D 1/06: Surface hardening
- C21D 6/004: {containing Cr and Ni}
- C21D 6/005: {containing Mn}
- C21D 6/007: {containing Co}
- C21D 6/008: {containing Si}
- C21D 9/36: for balls; for rollers
- C21D 9/40: for rings; for bearing races
- C22C 33/0257: {characterised by the range of the alloying elements}
- C22C 38/001: {containing N}
- C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60}
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/06: containing aluminium
- C22C 38/42: with copper
- C22C 38/44: with molybdenum or tungsten
- C22C 38/46: with vanadium
- C22C 38/52: with cobalt
- C23C 8/22: of ferrous surfaces
- C23C 8/26: of ferrous surfaces
- C23C 8/32: of ferrous surfaces
- C23C 8/80: After-treatment
- B22F 2998/10: Processes characterised by the sequence of their steps
- C21D 1/18: Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62)
- C21D 2211/001: Austenite
- C21D 2241/02: Hot isostatic pressing
- 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)
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)
- B22F: WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER (making alloys by powder metallurgy C22C); APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER

## Abstract

The present invention relates to a steel composition carburizable and/or nitritable, comprising, in percentages by weight of the total composition: Carbon: 0.05-0.40, preferably 0.10-0.30; Chromium: 2.50-5.00, preferably 3.00-4.50; Molybdenum: 4.00-6.00; Tungsten: 0.01-1.80, preferably 0.02-1.50; Vanadium: 1.00-3.00, preferably 1.50-2.50; Nickel: 2.00-4.00; Cobalt: 2.00-8.00, preferably 3.00-7.00; Iron: balance as well as the inevitable impurities, optionally further comprising one or more of the following elements: Niobium: ≤2.00; Nitrogen: ≤0.50, preferably ≤0.20; Silicon: ≤0.70, preferably 0.05-0.50; Manganese: ≤0.70, preferably 0.05-0.50; Aluminum: ≤0.15, preferably ≤0.10; the combined niobium+vanadium content being in the range 1.00-3.50; and the carbon+nitrogen content being in the range 0.05-0.50. It further relates to the method of production thereof, the steel blank obtained and a mechanical device comprising the latter.

## Claims

### Claim 1

A steel composition carburizable and/or nitritable comprising, in percentages by weight of the total composition:
Carbon: 0.05-0.40;
Chromium: 2.50-5.00;
Molybdenum: 4.00-6.00;
Tungsten: 0.01-1.80;
Vanadium: 1.00-3.00;
Nickel: 2.00-4.00;
Cobalt: 2.00-8.00;
Iron: balance
as well as the inevitable impurities,
optionally further comprising one or more of the following elements:
Niobium: ≤2.00;
Nitrogen: ≤0.50;
Silicon: ≤0.70;
Manganese: ≤0.70;
Aluminum: ≤0;
the combined niobium+vanadium content being in the range 1.00-3.50;
and the carbon+nitrogen content being in the range 0.05-0.50.

### Claim 2 (depends on 1)

The steel composition as claimed in claim 1, wherein it comprises, in percentages by weight of the total composition:
Carbon: 0.10-0.30;
Chromium: 3.00-4.50;
Molybdenum: 4.00-6.00;
Tungsten 0.02-1.50;
Vanadium: 1.50-2.50;
Nickel: 2.00-4.00;
Cobalt: 3.00-7.00;
Silicon: 0.05-0.50;
Manganese: 0.05-0.50;
Iron: balance
as well as the inevitable impurities,
optionally further comprising one or more of the following elements:
Niobium: ≤2.00;
Nitrogen: ≤0.20;
Aluminum: ≤0.10;
the combined niobium+vanadium content being in the range 1.00-3.50;
and the carbon+nitrogen content being in the range 0.05-0.50.

### Claim 3 (depends on 1)

The steel composition as claimed in claim 1, wherein it comprises at most 1 wt % of inevitable impurities relative to the total weight of the composition.

### Claim 4 (depends on 1)

The steel composition as claimed in claim 1, wherein the inevitable impurities are selected from titanium, sulfur, phosphorus, copper, tin, lead, oxygen and mixtures thereof.

### Claim 5 (depends on 1)

The steel composition as claimed in claim 1, wherein the tungsten content is in the range 0.03-1.40 in percentages by weight of the total composition.

### Claim 6 (depends on 5)

The steel composition as claimed in claim 5, wherein the tungsten content is in the range 0.04-1.30 in percentages by weight of the total composition.

### Claim 7 (depends on 1)

The steel composition as claimed in claim 1, wherein, after thermochemical treatment, followed by heat treatment, it has a surface hardness greater than or equal to 64 HRC.

### Claim 8 (depends on 7)

The steel composition as claimed in claim 7, wherein the heat treatment comprises solution heat treatment at a temperature between 1090° C.-1160° C. followed by quenching optionally with cooling to a temperature below −40° C. and several tempering operations, at a temperature greater than or equal to 475° C.

### Claim 9 (depends on 1)

The steel composition as claimed in claim 1, wherein, after thermochemical treatment, followed by heat treatment, it has a martensitic structure having a residual austenite content below 10% and that is free from ferrite and pearlite.

### Claim 10 (depends on 1)

A mechanical device, formed from steel having the composition as claimed in claim 1.

### Claim 11 (depends on 10)

The mechanical device according to claim 10, which is a bearing or a gear train.

### Claim 12 (depends on 1)

A method for producing a steel blank having the composition as claimed in claim 1, wherein it comprises:
a) a steelmaking step;
b) a step of processing the steel;
c) a thermochemical treatment;
d) and a heat treatment.

### Claim 13 (depends on 12)

The production method as claimed in claim 12, wherein step b) consists of a step of rolling, forging and/or extrusion.

### Claim 14 (depends on 12)

The production method as claimed in claim 12, wherein the steelmaking step a) is carried out by a conventional production process of arc furnace refining and electro slag remelting (ESR), or by a VIM-VAR process, optionally with a step of electro slag remelting (ESR) and/or vacuum arc remelting (VAR), or by powder metallurgy.

### Claim 15 (depends on 12)

A steel blank obtainable by a method as claimed in claim 12.

### Claim 16 (depends on 12)

The production method as claimed in claim 12, wherein step c) consists of a treatment of carburization or nitriding or carbonitriding or carburization and then nitriding.

### Claim 17 (depends on 16)

The production method as claimed in claim 16, wherein step c) consists of a treatment of carburization.

### Claim 18 (depends on 12)

The production method as claimed in claim 12, wherein step d) comprises solution heat treatment at a temperature between 1090° C.-1160° C., followed by holding at this temperature until there is complete austenitization optionally with cooling to a temperature below −40° C., and several tempering operations, at a temperature greater than or equal to 475° C.

### Claim 19 (depends on 18)

The production method as claimed in claim 18, wherein the tempering operations are carried out at a temperature greater than or equal to 500° C.

### Claim 20 (depends on 18)

The production method as claimed in claim 18, wherein the heat treatment is carried out at a temperature between 1100° C.-1150° C.