Metal treatment – Process of modifying or maintaining internal physical... – Carburizing or nitriding using externally supplied carbon or...
Patent
1996-08-09
1998-12-08
Yee, Deborah
Metal treatment
Process of modifying or maintaining internal physical...
Carburizing or nitriding using externally supplied carbon or...
148222, 266 78, 266 80, 266 90, 427 8, 427533, 427517, 20419216, 324464, 324466, 324468, C21D 109, C23C 820, C23C 824
Patent
active
058463410
DESCRIPTION:
BRIEF SUMMARY
THE FIELD OF TECHNOLOGY
The invention belongs to the field of metallurgy, in particular, to the field of surface heat treatment of steels and alloys in glow discharge and can be used in mechanical engineering for upgrading of surface hardening in carburizing, nitrocarburizing and nitriding of steels and alloys in glow discharge.
THE STATE-OF-THE-ART
Glow discharge has a characteristic specter of electromagnetic radiation. An intensity distribution in this specter depends on a chemical composition of the atmosphere where the discharge is ignited. When glow discharge is used for purposes of surface heat treatment of steels and alloys a radiation intensity is related in a unique fashion not only with the initial atmosphere composition but with complex physical and chemical processes occurring on and near the surface being treated as well. The regular relations which display themselves in electromagnetic radiation emitted in particular frequency regions are determined by concentrations of carbon- and nitrogen-containing particles and some other particles which are forming during ion heat treatment and depend upon the initial atmosphere composition, an area and a state of the surface being treated. These relations are very complex and insufficiently studied yet.
At present there is no direct way to determine a saturating ability of the ionized atmosphere during carburizing, nitrocarburizing or nitriding. Direct ways of diagnostics for phase transformations occurring on the surface being saturated during ion heat treatment are also unknown.
There is a sensor for active monitoring of steels and alloys heat treatment hardening which is designed to implement the way of heat treatment monitoring based on a known dependence of a contact potential difference in a point where a probing electrode touches the surface being saturated upon a chemical and phase composition of the materials brought into the contact. (Author's Certificate of the USSR 1008278, C23C 11/10, Bulletin of Inventions, -1983, #12). However, results obtained with the above named device suffer of noticeable measuring errors due to the following causes. First, the sensor surface is saturated in conditions which differ from that for a load of machine parts; second, the monitoring is performed at some distance from the surface being saturated; third, an output sensor signal includes integrated information about concentrations of all saturating elements and phase transformations in the diffuse layer; the device fails to separate these data.
This method does not provide possibility to determine a saturating ability of the atmosphere characterized by a content of active components in it and to fix a moment of the excessive phase development on the surface of the parts being treated.
There is another device designed to determine specific expenditure of the saturating gas in ion carburizing installations. (Author's Certificate of the USSR 769410, G01 N 7/10, Bulletin of Inventions, -1980, #37). Results obtained with the above named device suffer of noticeable measuring errors because they contain information on total amount of carbon absorbed by the surface during the whole saturating cycle. Besides, when the metal is saturated with carbon and nitrogen simultaneously this method fails to determine a saturating ability of each of these elements separately. This device also can not monitor phase transformations on the surface of the machine parts being treated.
The following diagnostics method for ion heat treatment of steels and alloys and the device for its realization are the closest to the applied inventions. This method (B. Edenhofer, Plasma carburizing and high pressure gas quenching in vacuum furnaces, 7th International Congress on Heat Treatment of Materials, -M., -1990, V. 1, pp. 103-112) consists in plasma parameters monitoring with subsequent estimating of a plasma saturating ability. The device realizing this method is designed as an electric current density sensor including connected one after another an instrument transducer, an electric signal
REFERENCES:
patent: 4108693 (1978-08-01), L'ttermite et al.
patent: 4445945 (1984-05-01), Schwalm
patent: 4472209 (1984-09-01), Langerich et al.
patent: 5650201 (1997-07-01), Tompa
patent: 5661115 (1997-08-01), Sandhu
Decision to grant Russian Federation patent on priority application No. 93-056024/02 and English translation, 1985.
Proceedings of 7thInternational Congress on Heat Treatment of Materials, Dec. 11-14 of 1990, Moscow.
USSR Author's Certificate No. 769410, Sensor of Carbon Potential, Jan. 24, 1978.
USSR Author's Certificate No. SU 1008278 A, Multipositional Sensor for Active Control of Heat Treatment Hardening of Steels and Alloy.
Ryzhov Nikolai Mikhailovich
Shemetov Valery Vasilyevich
Smirnov Andrei Evgenievich
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