Vacuum Heat Treating Using Plasma EB

Abstract

This paper describes a semicontinuous heat treatment equipment with some of its operating results for metal strips or foils. Work accelerated electron flux from a hot hollow cathode discharge is used for bombarding the strip. Use of hot hollow cathod discharge for annealing of a metal strip was briefly discussed by Morley in 1963. (see Ref. 1.) Smith, Jr. and Hunt reported in 1965 (Ref. 2) the use of high-voltage high-vacuum electron beam for continuous annealing of metal strips. Homogeneous thermal history, rapid heating cycle, and a very high temperature processing are obtainable by using an electron bombardment heating for running strips. Processing of metal strips while running will also be desirable for high temperature treatment where adhesion between layers of a roll may cause defects. The high-voltage high-vacuum EB is advantageous in obtaining higher energy density than the use of hot hollow cathode EB. The latter, however, operates at a low voltage and often more economically than the former. Less evaporation of a volatile component can be another factor to be considered for some alloys. Thus refractory alloys strip rolls that require high temperature contamination free environment, minimum vaporization of volatile component, and nonsticking between layers will be suitable for the plasma EB semicontinuous or continuous processing.