Metal treatment – Compositions – Heat treating
Patent
1976-12-27
1978-10-10
Steiner, Arthur J.
Metal treatment
Compositions
Heat treating
148 27, C21D 106
Patent
active
041194446
ABSTRACT:
A method of nitriding metal parts is disclosed. A preferred mode requires burying the metal part to be treated in a body of vermiculite or other porous media containing urea or other suitable nitriding agent. Prior to burying, a controlled amount of an aqueous solution of the nitriding agent is absorbed into dry vermiculite; the water of the solution is removed by evaporation leaving a pasty substance coating or impregnating the grains of the vermiculite. The pasty substance coating each vermiculite grain physically forms a thin film on the external particle surface and on the surfaces of its internal porosity; the average film thickness is less than 0.001 inch. The vermiculite bearing the nitriding agent and buried part are heated in a closed container to a temperature at which the agent decomposes at a predetermined slow rate and releases gases bearing nitrogen. Heating is continued for about 4-8 hours at 700.degree.-1300.degree. F (preferably 925.degree.-1050.degree. F for 90% of the applications) to achieve a nitrided case on the metal part of the desired thickness, typically 0.002-0.005 inch thick.
REFERENCES:
patent: 1772866 (1930-08-01), Hirsch
patent: 2219004 (1940-10-01), Daeves et al.
patent: 2219005 (1940-10-01), Daeves et al.
patent: 2801154 (1957-07-01), DePree et al.
patent: 2948644 (1960-08-01), Aherns
patent: 3232797 (1966-02-01), Bessen
patent: 3303063 (1967-02-01), Pietryko
Ford Motor Company
Johnson Olin B.
Malleck Joseph W.
Steiner Arthur J.
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