# US 10,502,319 B2 · Piston ring and its production method

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 10,502,319 B2
- Document ID: US10502319B2
- Status: Granted
- Kind: B2
- Application number: 15/744,609
- Filed: 2016-07-14
- Published: 2018-07-26
- Granted: 2019-12-10
- Earliest claimed: 2015-07-17
- Assignees: Riken
- Applicants: Kabushiki Kaisha Riken
- Inventors: Yuji Shima
- Web page: https://patentgrep.com/patent/US10502319B2

## CPC

- F16J 9/22: Rings for preventing wear of grooves or like seatings
- C23C 8/26: of ferrous surfaces
- C23C 8/38: Treatment of ferrous surfaces
- C23C 8/50: of ferrous surfaces
- C23C 8/80: After-treatment
- C23C 22/22: containing alkaline earth metal cations
- C23C 28/04: only coatings of inorganic non-metallic material
- F02F 5/00: Piston rings, e.g. associated with piston crown
- F16J 9/26: characterised by the use of particular materials
- C22C 21/02: with silicon as the next major constituent
- 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
- C23C 22/78: Pretreatment of the material to be coated
- C23C 30/00: Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process (C23C26/00, C23C28/00 take precedence)
- F02F 1/20: characterised by constructional features providing for lubrication
- F16J: PISTONS {(specially adapted for dampers F16F9/32)}; CYLINDERS; SEALINGS
- 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)
- F02F: CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

To provide a piston ring free from microwelding to a piston while exhibiting excellent wear resistance in side surfaces, for a long period of use in a high-temperature, high-pressure environment, and its production method, a nitride layer is formed on at least one of upper and lower side surfaces of the piston ring, and then subjected to a phosphate chemical conversion treatment, such that the nitride layer has at least one of granular and vermicular surface forms.

## Claims

### Claim 1

A piston ring made of steel, which has a nitride layer formed on at least one of upper and lower side surfaces, said nitride layer having at least one of granular and vermicular surface forms, wherein
a surface roughness curve of said nitride layer has the maximum height Rz of 2.5-6 μm.

### Claim 2 (depends on 1)

The piston ring according to claim 1, wherein the diameters of said granular surface forms and the short diameters of said vermicular surface forms are in a range of 3-40 μm on average.

### Claim 3 (depends on 1)

The piston ring according to claim 1, wherein a phosphate chemical conversion coating is formed on said nitride layer.

### Claim 4 (depends on 3)

The piston ring according to claim 3, wherein said phosphate chemical conversion coating is a zinc calcium phosphate coating.

### Claim 5 (depends on 1)

The piston ring according to claim 1, wherein a matrix of said piston ring, on which said nitride layer is formed, is made of a steel comprising C, Si, Mn and Cr as indispensable alloy elements, and Mo, V and B as optional alloy elements; the composition of said indispensable alloy elements comprising by mass 0.45-0.65% of C, 0.15-0.35% of Si, 0.65-1.00% of Mn, and 0.60-1.10% of Cr; the composition of said optional alloy elements comprising by mass less than 0.35% of Mo, less than 0.25% of V, and less than 0.001% of B; and the total amount of said indispensable alloy elements and said optional alloy elements being less than 3.0% by mass.

### Claim 6 (depends on 5)

The piston ring according to claim 5, wherein said nitride layer has hardness of 700 HV0.05 or more in a range from the outermost surface to the depth of 30 μm.

### Claim 7 (depends on 6)

The piston ring according to claim 6, wherein said nitride layer has a hardness reduction ratio of 3 HV0.05/μm or less in a range from the outermost surface to the depth of 30 μm in a depth direction.

### Claim 8 (depends on 5)

The piston ring according to claim 5, wherein the hardness of said matrix is 90-100% of the hardness before nitriding.

### Claim 9

A piston ring made of steel, which has a nitride layer formed on at least one of upper and lower side surfaces, said nitride layer having at least one of granular and vermicular surface forms, wherein
a matrix of said piston ring, on which said nitride layer is formed, is made of a steel comprising C, Si, Mn and Cr as indispensable alloy elements, and Mo, V and B as optional alloy elements; the composition of said indispensable alloy elements comprising by mass 0.45-0.65% of C, 0.15-0.35% of Si, 0.65-1.00% of Mn, and 0.60-1.10% of Cr; the composition of said optional alloy elements comprising by mass less than 0.35% of Mo, less than 0.25% of V, and less than 0.001% of B; and the total amount of said indispensable alloy elements and said optional alloy elements being less than 3.0% by mass,
said nitride layer has hardness of 700 HV0.05 or more in a range from the outermost surface to the depth of 30 μm, and
said nitride layer has a hardness reduction ratio of 3 HV0.05/μm or less in a range from the outermost surface to the depth of 30 μm in a depth direction.

### Claim 10

A piston ring made of steel, which has a nitride layer formed on at least one of upper and lower side surfaces, said nitride layer having at least one of granular and vermicular surface forms, wherein
a matrix of said piston ring, on which said nitride layer is formed, is made of a steel comprising C, Si, Mn and Cr as indispensable alloy elements, and Mo, V and B as optional alloy elements; the composition of said indispensable alloy elements comprising by mass 0.45-0.65% of C, 0.15-0.35% of Si, 0.65-1.00% of Mn, and 0.60-1.10% of Cr; the composition of said optional alloy elements comprising by mass less than 0.35% of Mo, less than 0.25% of V, and less than 0.001% of B; and the total amount of said indispensable alloy elements and said optional alloy elements being less than 3.0% by mass, and
the hardness of said matrix is 90-100% of the hardness before nitriding.

### Claim 11 (depends on 1, 2)

A method for producing the piston ring recited in any one of claims 1, 2, and 3-8, wherein after said piston ring is formed by a steel wire, at least one of upper and lower side surfaces of said piston ring is nitrided, and then subjected to a phosphate chemical conversion treatment.

### Claim 12 (depends on 11)

The method for producing a piston ring according to claim 11, wherein said phosphate chemical conversion treatment is a zinc calcium phosphate treatment.

### Claim 13 (depends on 12)

The method for producing a piston ring according to claim 12, wherein said zinc calcium phosphate treatment is conducted under the conditions of a treatment temperature of 75-95° C. and total acidity of 30-55 points.