Metal treatment – Process of modifying or maintaining internal physical... – With casting or solidifying from melt
Patent
1991-07-29
1992-08-18
Dean, R.
Metal treatment
Process of modifying or maintaining internal physical...
With casting or solidifying from melt
148322, C21D 500
Patent
active
051395797
ABSTRACT:
A method for preparing an austempered cast iron which includes an ausferritic matrix, the cast iron having a silicon content of from about 1.6 to about 2.4 weight percent, and a carbon content of from about 1.6 to about 2.2 weight percent, such that the carbon equivalent of the cast iron is from about 2.1 to about 3.0 weight percent. The method includes (a) melting the cast iron composition; (b) pouring the melt into a mold to form a casting having eutectic carbide particles; (c) altering the temperature of the casting to about 1650.degree.-1900.degree. F. and maintaining the temperature of the casting at about 1650.degree.-1900.degree. F. until substantially all of the eutectic carbide particles convert to temper graphite nodules to form a temper graphite-containing casting; (d) cooling the temper graphite-containing casting to about 1500.degree.-1750.degree. F. and maintaining the temperature of the tempered graphite-containing casting at about 1500.degree.-1750.degree. F. until a fully austenitic matrix is achieved; (e) quenching the austenitic matrix casting to a temperature of between about 460.degree. to about 750.degree. F. and maintaining that temperature until the entire casting is transformed to an ausferritic matrix; and (f) cooling the ausferritic matrix casting to room temperature before bainite is formed.
REFERENCES:
patent: 2796373 (1957-06-01), Berg
Metals Handbook, 9th Ed, vol. 4; 1981 pp. 104-105; 299-302.
John Keough; Industrial Heating; "Process and Equipment Development in Austempering Ductile Iron Increase its Utility" pp. 56-59; Sep. 1989.
J. F. Janowak and R. B. Gundlach; Journal of Heat Treating; vol. 4 No. 1 "Approaching Austempered Ductile Iron Properties by Controlled Cooling in the Foundry" Jun. 1985, pp. 25-31.
Keough John R.
Kovacs Bela V.
Pramstaller Douglas M.
Applied Process
Cargill Lynn E.
Dean R.
Phipps Margery S.
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