# US 2020/0399751 A9 · Method of case hardening gears

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- Number: US 2020/0399751 A9
- Document ID: US20200399751A9
- Status: Published application
- Kind: A9
- Application number: 15/592,501
- Filed: 2017-05-11
- Published: 2020-12-24
- Earliest claimed: 2010-12-31
- Inventors: Anatoly Alexeevich Kuznetsov; Arkadiy Moiseevich Peker; Semyon Brayman; Nikolay Igorevich Mironov
- Web page: https://patentgrep.com/patent/US20200399751A9

## CPC

- C23C 8/04: Treatment of selected surface areas, e.g. using masks
- C21D 1/06: Surface hardening
- F16H 55/06: Use of materials; Use of treatments of toothed members or worms to affect their intrinsic material properties
- F16H 55/17: Toothed wheels (worm wheels F16H55/22; chain wheels F16H55/30)
- 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)
- 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)
- F16H: GEARING

## Abstract

A method of case hardening toothed gearing using low (LH) or specified hardness (SH) steel and using through surface hardening (TSH) in order to create a described case hardening pattern which increases the fatigue strength of the gear tooth.

## Claims

### Claim 1

canceled

### Claim 2

canceled

### Claim 3

canceled

### Claim 4

canceled

### Claim 5

A method of making gears of a gear modulus m greater than 5 mm for continuous bending and contact loads in the range of 400-600 N/mm2 fatigue point and higher short term loads, comprising making said gears from low hardenability (LH) or specified hardenability (SH) steel having a carbon content of 0.5 to 1.2% and of a critical diameter Dcr in mm equal to the gear modulus m times 1.5 to 2.0, and through surface hardening (TSH) said gears so formed,
whereby a hardened depth in mm at the tooth root bottom and radius is equal to 0.2 to 0.25 times the gear modulus m;
a hardened depth in mm at a pitch line is equal to 0.25 to 0.32 times the gear modulus m; and,
a hardened depth in mm at a tooth tip is equal to 0.25 to 0.75 times the gear modulus m; and,
a surface hardness (HRC) at a surface is equal to 56 to 65 and at a gear tooth core equal to 30 to 45.

### Claim 6

A method of making gears of a gear modulus m from 3 to 4.5 mm for continuous bending loads in the vicinity of 300-600 N/mm2 fatigue point, comprising making said gears from low hardenability (LH) or specified hardenability (SH) steel having a carbon content of 0.5 to 1.2% and of a critical diameter Dcr in mm equal to the gear modulus m times 1.5 to 2.5, and through surface hardening (TSH) said gears so formed, whereby:
a hardened depth in mm at a tooth root bottom and radius is equal to 0.2 to 0.45 times the gear modulus m;
a hardened depth in mm at the pitch line is equal to 0.25 to 0.78 times the gear modulus m;
a hardened depth mm at the tooth tip is equal to 0.25 to 1.25 times the gear modulus m, and,
a surface hardness (HRC) is equal to 56-61 and at a gear tooth core of 30-45.

### Claim 7

A method of making gears of a gear modulus m of 3.0 to 4.5 mm for continuous bending in the range of 300 N/mm2 fatigue point, comprising making said gears from low hardenability (LH) or specified hardenability (SH) steel having a carbon content of 0.35 to 1.2% and having critical diameter Dcr in mm equal to the gear modulus m times 1.5 to 3.0, and through surface hardening (TSH) said gears so formed, whereby:
a hardened depth in mm at the tooth root bottom and a radius equal to 0.2 to 0.75 times the gear modulus m;
a hardened depth in mm at the pitch line equal to 0.25 to 0.78 times the gear modulus m;
a hardened depth in mm at the tooth tip equal to 0.25 to 2.0 times the gear modulus m; and
a surface hardness (HRC) at the surface equal to 50-61 and at a gear tooth core equal to 30-45.

### Claim 8 (depends on 5)

The method according to claim 5 wherein with a carbon content in LH or SH steels above 0.6% after TSH said gears are subjected to deep-freeze treatment at temperatures not higher than −60° C.

### Claim 9 (depends on 6)

The method according to claim 6 wherein with a carbon content in LH or SH steels above 0.6% after TSH said gears are subjected to deep-freeze treatment at temperatures not higher than −60° C.

### Claim 10 (depends on 7)

The method according to claim 7 wherein with a carbon content in LH or SH steels above 0.6% after TSH said gears are subjected to deep-freeze treatment at temperatures not higher than −60° C.

### Claim 11 (depends on 5)

The method according to claim 5 wherein on the surfaces to be subjected to TSH, the hardened layer may be either continuous or intermittent.

### Claim 12 (depends on 6)

The method according to claim 6 wherein on the surfaces to be subjected to TSH, the hardened layer may be either continuous or intermittent.

### Claim 13 (depends on 7)

The method according to claim 7 wherein on the surfaces to be subjected to TSH, the hardened layer may be either continuous or intermittent.

### Claim 14 (depends on 5)

The method according to claim 5 wherein the micro structure of the tooth hardened layer in the pitch line zone at the depth of not less than 0.08 m:
fine-crystal line structured tempered martensite formed in the TSH process with the actual grain size #10-14 per ASTM scale, without the structurally free ferrite or austentite decomposition of bainite, troostite or sorbite;
0-15% residual austenite for LH or SH gears with 0.6-1.2% carbon;
nitrides and carbides and nitrides, vanadium carbides and other rare-earth elements; and
0-50% troostite inclusions at the greater depth up to the core/hardened layer boundary.

### Claim 15 (depends on 6)

The method according to claim 6 wherein the micro structure of the tooth hardened layer in the pitch line zone at the depth of not less than 0.06 m is as follows:
fine-crystal line structured tempered martensite formed in the TSH process with the actual grain size #10-14 per ASTM scale, without the structurally free ferrite or austentite decomposition of bainite, troostite or sorbite;
0-15% residual austenite for LH or SH gears with 0.6-1.2% carbon;
nitrides and carbides and nitrides, vanadium carbides and other rare-earth elements; and
0-50% troostite inclusions at the greater depth up to the core/hardened layer boundary.