Claims
- 1. A method of manufacturing a steel tube having a small outside diameter and a large wall thickness, and a hardened layer on at least one surface, comprising the steps of Tufftriding a steel tube in a molten bath of sodium cyanide while the tube is being axially vibrated, whereby a diffusion layer comprising a solid solution of nitrogen is formed on at least one surface of the tube; and heat treating the tube in a gaseous atmosphere to decompose any intermetallic compound formed on the diffusion layer by the Tufftriding, whereby a hardened layer is formed on the said surface.
- 2. A method according to claim 1, wherein an antinitriding treatment is applied to the external surface of the tube whereby the hardened layer is formed only on the internal surface of the tube.
- 3. A method according to claim 2, wherein the antinitriding treatment comprises plating the external tube surface with nickel.
- 4. A method according to any one of claims 1 to 3, wherein the gaseous atmosphere is composed at least mainly of nitrogen.
Priority Claims (1)
Number |
Date |
Country |
Kind |
56-87868 |
Jun 1981 |
JPX |
|
Parent Case Info
This is a division of application Ser. No. 383,788 filed June 1, 1982, now U.S. Pat. No. 4,458,724.
US Referenced Citations (4)
Non-Patent Literature Citations (3)
Entry |
Metals Handbook, vol. 2, 8th Ed., Amer. Soc. Metals, Metals Park, Oh., pp. 146-151, 1974. |
Frank Smith, Metals (Australia) Tufftride-Its Metallurgy Application and Evaluation, pp. 147-152, Jun. 1970. |
SAE Testing Stands for Diesel Fuel Injection Systems-SAE J970a pp. 24,104-24,109 and SAE J521b-Fuel Injection Tubing Connections. |
Divisions (1)
|
Number |
Date |
Country |
Parent |
383788 |
Jun 1982 |
|