GB492663A - A method of treating metals to change their structure - Google Patents

Abstract

492,663. Altering physical structure. THORNTON, A. A. (Bercovitz, B., and Debor, H.) March 23, 1937, No. 8499. Drawings to Specification. [Class 83 (iv)] The structure of metal bodies, particularly steel, is changed by acting on the bodies whilst at forging temperature by a gas under high pressure, in which pressure impulses are generated in rapid succession. The gas may be air, carbon dioxide or nitrogen under a pressure of from 10 to 1000 atmospheres or more, and for a hollow body the gas may be introduced internally and a mould may surround it to prevent expansion thereof, or the gas may be introduced between the mould and a body which then has its contraction prevented by a core. The gas may be introduced or exhausted through the core. The gas is subjected to rapid alternations of pressure by introducing it into the body or mould through a rapidly rotating valve which alternately establishes and interrupts communication between the gas supply and body, a construction of valve being described in the Specification. The body may be heated before introduction into the mould but is preferably heated in the mould by electric resistance heating, or the gas may be preheated to the required temperature and its pressure thereby increased at the same time. The gas may be selected with a view to making chemical or metallurgical changes in the metal, e.g. producing an inner or outer layer of metal carbides or nitrides &c.