# US 5,707,460 A · Method of producing parts having improved wear, fatigue and corrosion resistance from medium alloy, low carbon steel and parts obtained therefrom

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- Number: US 5,707,460 A
- Document ID: US5707460A
- Status: Granted
- Kind: A
- Application number: 08/500,533
- Filed: 1995-07-11
- Granted: 1998-01-13
- Earliest claimed: 1995-07-11
- Assignees: Porter-Cable Corporation
- Inventors: Bimal K. Chaterjee
- Web page: https://patentgrep.com/patent/US5707460A

## CPC

- C23C 8/32: of ferrous surfaces
- 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)

## Abstract

Improved corrosion, wear and fatigue resistance is provided for pieces formed of medium alloy, low carbon steel by subjecting the piece to a treatment process which includes a step of carburizing, followed by nitriding. The process is especially useful for producing durable and low-cost steel parts, for example for certain automotive and marine applications, pumps (especially positive displacement pumps), chemical or food processing equipment, power tools, and the like. The blade-carrying reciprocating shaft for a reciprocating power saw is a specific example.

## Claims

### Claim 1

A method of treating a piece formed of medium alloy, low carbon steel, comprising:
(a) subjecting the piece to a carburizing treatment whereby a martensitic case is formed at the surface of the piece; and
(b) subsequently subjecting the piece to nitriding.

### Claim 2 (depends on 1)

The method of claim 1, wherein the piece is formed by joining at least two components together by welding before carburizing.

### Claim 3 (depends on 2)

The method of claim 2, further comprising machining the piece or the components prior to carburizing.

### Claim 4 (depends on 1)

The method of claim 1, wherein the nitriding is salt bath nitriding.

### Claim 5 (depends on 4)

The method of claim 4, wherein the salt bath nitriding is carried out with a bath of molten cyanate and carbonate salts of potassium and sodium.

### Claim 6 (depends on 2)

The method of claim 2, wherein the welding is laser welding.

### Claim 7 (depends on 1)

The method of claim 1, wherein the medium alloy, low carbon steel has a carbon content of not more than about 0.32%.

### Claim 8 (depends on 1)

A piece formed of medium alloy, low carbon steel, produced by a method according to claim 1.

### Claim 9

A piece formed of medium alloy, low carbon steel, having corrosion and wear resistance properties at least comparable to those of an otherwise identical piece formed from stainless steel.

### Claim 10 (depends on 8)

The piece of claim 8, which is a component of a reciprocating saw.

### Claim 11 (depends on 10)

The piece of claim 10, which is a reciprocating shaft for carrying a blade of a reciprocating saw.

### Claim 12 (depends on 9)

The piece of claim 9, which is a component of a reciprocating saw.

### Claim 13 (depends on 12)

The piece of claim 12, which is a reciprocating shaft for carrying a blade of a reciprocating saw.

### Claim 14 (depends on 1)

The method of claim 1, wherein the steel is selected from the group consisting of 6118, 6120, 8115, 8615, 8617, 8620, 8622, 9625, 8627, 8630, 8720, 8822, 9310, 94B15, 94B17 and 94B30 steel.