# US 8,540,825 B2 · Low-temperature stainless steel carburization method

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- Number: US 8,540,825 B2
- Document ID: US8540825B2
- Status: Granted
- Kind: B2
- Application number: 13/074,742
- Filed: 2011-03-29
- Published: 2012-10-04
- Granted: 2013-09-24
- Earliest claimed: 2011-03-29
- Assignees: Taiwan Powder Technologies Co., Ltd.
- Applicants: Kuen-Shyang Hwang; Li-Hui Cheng; Yung-Chung Lu
- Inventors: Kuen-Shyang Hwang; Li-Hui Cheng; Yung-Chung Lu
- Web page: https://patentgrep.com/patent/US8540825B2

## CPC

- C23C 8/02: Pretreatment of the material to be coated (C23C8/04 takes precedence)
- C23C 8/22: 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

A low-temperature stainless steel carburization method comprises steps: providing a stainless steel material; placing the stainless steel material in a halogen-free reducing environment and maintaining the stainless steel at a first temperature ranging 1,050 to 1,400° C.; and placing the stainless steel material in a carbon-bearing atmosphere and maintaining the stainless steel material at a second temperature lower than 600° C. to implant carbon atoms into the stainless steel material to form a carburized layer on the surface of the stainless steel material. A halide-bearing gas or solution is not to be applied to activate the passivation layer, so the fabrication cost would be reduced and the safety of carburization process would be enhanced. Besides, the environment can be prevented from halide pollution.

## Claims

### Claim 1

A low-temperature stainless steel carburization method comprising steps:
providing a stainless steel material fabricated with a forging process;
placing the stainless steel material in a halogen-free reducing environment and maintaining the stainless steel at a first temperature ranging 1050 to 1400° C.; and
placing the stainless steel material in a carbon-bearing atmosphere and maintaining the stainless steel material at a second temperature lower than 600° C. to implant carbon atoms into the stainless steel material to form a carburized layer on the surface of the stainless steel material.

### Claim 2 (depends on 1)

The low-temperature stainless steel carburization method according to claim 1, wherein the environment is a vacuum environment or a hydrogen-bearing atmosphere.

### Claim 3 (depends on 2)

The low-temperature stainless steel carburization method according to claim 2, wherein the hydrogen-bearing atmosphere contains over 5.0 vol % hydrogen.

### Claim 4 (depends on 1)

The low-temperature stainless steel carburization method according to claim 1, wherein the second temperature ranges from 400 to 580° C.

### Claim 5 (depends on 1)

The low-temperature stainless steel carburization method according to claim 1, wherein the carburized layer has a thickness of 10-50 μm.

### Claim 6 (depends on 1)

The low-temperature stainless steel carburization method according to claim 1, wherein the carbon-bearing atmosphere is selected from a group consisting of carbon monoxide, methane and propane.

### Claim 7 (depends on 1)

The low-temperature stainless steel carburization method according to claim 1, wherein the stainless steel material contains less than 2.0 wt % carbon, less than 1.0 wt % silicon, less than 2.0 wt % manganese, 12.0-19.0 wt % chromium, less than 15.0 wt % nickel, less than 6.0 wt % molybdenum, less than 6.0 wt % copper, with iron being the balance.