Process for the low pressure carburization of metal alloy parts
AssigneeAcieries Aubert & Duval
InventorsAndre Faure, Jacques Frey
Life of this patent
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Abstract
A low pressure carburization process for metal alloy parts uses a fuel mixture consisting of hydrogen with 2 to 60% by volume ethylene. The fuel mixture is heated to a temperature between 820.degree. and 1100.degree. C. A furnace installation for carrying out the process includes a double vacuum tank or vessel arrangement with internal carburizing gas distribution, an annular space surrounding the vessel, a cover, thermocouples and a microcomputer control arrangement.
Claims10
Process for the low pressure carburization of metal alloy parts contained in a furnace chamber heated to a temperature between about 820.degree. C. and about 1100.degree. C. comprising the steps of:
- a) forming a preliminary vacuum in the chamber to a pressure of 10.sup.-1 hPa so as to eliminate the air,
- b) filling the chamber with purified nitrogen at atmospheric pressure,
- c) loading the metal parts into the chamber,
- d) forming a vacuum at 10.sup.-2 hPa in the chamber,
- e) heating the chamber to the austenitization temperature and maintaining this temperature for homogenizing the parts,
- f) introducing hydrogen into the chamber at a pressure of up to 500 hPa,
- g) introducing ethylene into the chamber at a pressure of 10 to 100 hPa and forming an ethylene-based fuel gas mixture with said hydrogen, said fuel gas mixture consisting of hydrogen and ethylene, ethylene being present in an amount of from about 2% to about 60% by volume for carbonization to provide carbon,
- h) vacuum diffusing carbon at 10.sup.-1 hPa, and
- i) introducing nitrogen into the chamber for unloading the parts.
Process for the low pressure carburization of metal alloy parts contained in a furnace chamber heated to a temperature between about 820.degree. C. and about 1000.degree. C. comprising the steps of:
- a) forming a preliminary vacuum in the chamber to a pressure of 10.sup.-1 hPa so as to eliminate the air,
- b) filling the chamber with purified nitrogen at atmospheric pressure,
- c) loading the metal parts into the chamber,
- d) forming a vacuum at 10.sup.-2 hPa in the chamber,
- e) heating the chamber to the austenitization temperature and maintaining this temperature for homogenizing the parts,
- f) introducing hydrogen into the chamber at a pressure of up to 500 hPa,
- g) introducing ethylene into the chamber at a pressure of 10 to 100 hPa, and forming an ethylene-based fuel gas mixture with said hydrogen, said fuel gas consisting of hydrogen and ethylene, ethylene being present in an amount of from about 2% to about 60% by volume for carbonization to provide carbon,
- h) vacuum diffusing carbon at 10.sup.-1 hPa,
- i) breaking the vacuum with hydrogen,
- j) introducing ethylene into the chamber at a pressure of 10 to 100 hPa, and forming more of said ethylene-based fuel gas for carbonization to provide carbon,
- k) diffusing carbon, and
- l) breaking the vacuum with nitrogen at atmospheric pressure.
Process for the low pressure carburization of metal alloy parts contained in a furnace for heating in a furnace atmosphere comprising the steps of:
- forming said furnace atmosphere of a gaseous fuel mixture consisting of hydrogen and ethylene at a pressure less than atmospheric pressure, ethylene being present in an amount of from about 2% to about 60% by volume for providing carbon for carburization of said metal alloy parts,
- heating said furnace atmosphere to a temperature of from about 820.degree. C. to about 1100.degree. C., and
- carburizing said metal alloy parts by incorporating carbon into the metal alloy parts to a desired depth.
Dependencies are inferred from the claim text.