Vacuum furnace for heating prodn. objects - using two vacuum chambers operated at different vacuum-hardness

摘要

Process for the treatment of prodn. objects arranged in a chamber (I) which is connected by an opening to a chamber (II) which is continuously evacuated by a vacuum source to obtain a pressure (II) of 10 mu to 6700 mu in chamber (II); a compressed gas, which may be functional or inert, is continuously fed into chamber (I) so its pressure is always higher than pressure (II) and at a value of 100-10,000 mu so the gas flows continuously into chamber (II), and the flow of gas maintains the pressures (I, II). The pref. ratio I:II is between 1.5:1 and 20:1, and the pref. flow of compressed gas is 3-300 1/h, esp. using N2, Ar, O2, H2, air or hydrocarbon gases. The opening between the chambers may be variable and the objects are pref. heated up to 3000 degrees C. Used e.g. for heating steel or iron castings for degassing and removal of surface oxide prior to glazing; brazing Al without flux; soldering or brazing OFHC copper; brazing of titanium; heat-treating steels.