Vacuum carburizing steel

• US 4,386,973 A
• Filed: 05/08/1981
• Issued: 06/07/1983
• Est. Priority Date: 05/08/1981
• Status: Expired due to Term

• Current Assignee: GSTC Development Corporation
• Original Assignee: General Signal Corporation (SPX Corporation)
• Inventors: Kawka, Richard J., Roth, Philip, Herring, Daniel H., Sitko, Richard J.
• Primary Examiner(s): Sheehan, John P.
• Application Number:
  US06/261,761
• Time in Patent Office: 760 Days
• Field of Search: 148/16, 148/16.5, 148/16.6, 148/16.7
• US Class Current: 148/223
• CPC Class Codes: C23C 8/22 of ferrous surfaces

Abstract

A method of carburizing steel comprising carburizing steel under vacuum utilizing as the carburizing gas an aliphatic alcohol having 1 to 4 carbon atoms, preferably methanol and natural gas additions.

Claims

1. A process for carburizing steel comprising carburizing said steel under vacuum in a vacuum furnace in the presence of a hydrocarbon carburizing agent while utilizing as a carrier gas an aliphatic alcohol having 1 to 4 carbon atoms, wherein fresh carburizing agent is supplied during said carburizing by cyclically reducing the pressure in the furnace followed by the addition of hydrocarbon carburizing agent to the furnace to replenish gas removed in the pressure reduction step.

2. A process in accordance with claim 1, comprising the steps of:

(a) evacuating the furnace to remove air therefrom;

(b) raising the temperature thereby removing oxygen or air from the surface of the steel;

(c) introducing an inert gas and an alcohol into the furnace;

(d) introducing a measured amount of a hydrocarbon containing gas into the furnace; and

(e) carburizing the steel.

3. A process in accordance with claim 1, wherein said aliphatic alcohol is methanol.

4. A process in accordance with claim 2, wherein, in step b, the temperature is raised to from about 1400°

F. to about 2200°

F.

5. A method in accordance with claim 2, wherein said inert gas is introduced to a pressure of from about 300 Torr to about 400 Torr.

6. A method in accordance with claim 1 or 2, wherein said aliphatic alcohol is introduced to a pressure of from about 300 Torr to about 500 Torr.

7. A method in accordance with claim 1 or 2, wherein the steel is carburized at a temperature of from about 1400°

F. to about 2200°

F.

8. A method in accordance with claim 2, further including the step of backfilling the furnace with said inert gas during removal of the steel.