Vacuum chamber oven

The vacuum chamber oven for heat treating metallic workpieces contains, in a cylindrical steel housing (1), a heating chamber (2) having substantially rectangular contours, the walls of which have closable openings (17, 20) for the passage of a cooling gas, which can be circulated over a heat exchanger (24) with the aid of a blower (23). To be able to adapt the flow of cooling gas optimally to the particular batch structure and to achieve a uniform cooling rate within a batch, on the one hand a plurality of relatively small openings (17) or a larger opening are present in each case in two mutually opposite walls for alternately admitting gas into the heating chamber (2) for the purpose of creating gas flows in opposite directions, and on the other hand in the adjacent, identically oriented walls there is provided, at their edges, in each case a longitudinal gap (20) running parallel to the adjoining wall for discharging the gas, in which case the two longitudinal gaps (20) situated in different walls are to be opened and closed in each case at the same time as the admission openings (or the admission opening) in the wall on the opposite chamber side. As a result of this arrangement, during the cooling process the circulated cooling gas inside the heating chamber (2) can flow either vertically in two opposite directions or horizontally in two opposite directions.