Fluidized-bed heat-treatment method for metallic workpieces

US4620883A · kind A · utility

Inventors

• Ewald Schwing · Neukirchen-Vluyn, DE
• Peter Sommer · Copenhagen, DK
• Horst Uhrner · Issum, DE

Key dates

• Filing date: Sep 4, 1984
• Grant date: Nov 4, 1986
• Expiry date: Sep 4, 2004

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C21D1/53
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

A metallic object is heat treated by suspending it in a fluidizable bed through which a gas can be passed at a volume/time rate to fluidize it. The temperature of the bed is varied in accordance with a temperature curve having regions of considerable slope and temperature change and regions of inconsiderable slope and temperature change and the workpiece temperature varies in accordance with the bed temperature principally by heat conduction between the bed and workpiece. Enough gas is passed through the bed at a predetermined relatively high volume/time rate sufficient to fluidize the bed only during the periods corresponding to the regions of considerable slope and gas is passed through the bed at a relatively low volume/time rate equal to more than 0% and less than 75%, and preferably between 5% and 45%, of the high rate and insufficient to fluidize the bed during the periods corresponding to the regions of inconsiderable slope. The low rate is about 10% of the high rate.