Abstract: Workpieces are quenched by gases in a heat-treatment system (1) and the circulated gases are recooled on cooling surfaces (12, 15) in at least one heat exchanger (11, 14), the cooling surfaces (15) of the heat exchanger (14) are cooled by a primary refrigeration unit (20) and a refrigerant to temperatures below 0.degree. C., preferably to temperatures below -20.degree. C. or even below -40.degree. C., to increase the intensity of the quenching. To reduce the size and power of the refrigeration unit (20), the quenching gas is sent in succession through at least one heat exchanger (11) cooled with water and at least one heat exchanger (14) cooled by a refrigerant. To reduce the size and power of the refrigeration unit (20) even further, this unit and a secondary refrigerant are used initially to cool down a storage volume of the primary refrigerant, such as a cooling brine, being stored under little or no pressure, to a temperature below 0.degree. C.

Abstract: Method for the treatment of alloy steels and refractory metals such as Ti, Zr and Nb, especially for depassivation and subsequent thermochemical surface treatment in a process chamber (1, 2) under the action of pressure and temperature, wherein, in a first process step, a first gas or gas mixture from the group N.sub.2, H.sub.2 or NH.sub.3 is admitted for the depassivation into a process chamber (1), a pressure greater than 1 bar a and a temperature between 100.degree. C. and 1,000.degree. C. is established in the chamber (1), and in a second process step a second gas or gas mixture from the group of N-, C- or B-containing gases is admitted into a process chamber (1, 2) for the thermochemical surface treatment, and a temperature between 100.degree. C. and 1,000.degree. C. at a pressure greater than or equal to 1 bar a is established.

Abstract: In a vacuum heat treating oven operating with hydrogen under pressure as the cooling medium, especially for the quenching of greatly heated metal workpieces (5), a method is provided for the automatic control of the progress of the process and for monitoring safety of operation. The housing (4) of the heat treating oven is for this purpose connected to gas inlet lines (9 and 10), one for the admission of the cooling gas and one for the admission of the flushing gas (H.sub.2 and N.sub.

Abstract: An economical process for applying nitride layers to titanium and titanium alloys. Within a short time, layer thicknesses of 20 .mu.m are obtained by pressure-nitriding in an ammonia atmosphere. To this end, temperatures of 500.degree. to 1000.degree. C. and pressures of 0.2 to 9 MPa are used.

Abstract: In a vacuum heat treating oven operating with hydrogen under pressure as the cooling medium, especially for the quenching of greatly heated metal workpieces (5), a method is provided for the automatic control of the progress of the process and for monitoring safety of operation. The housing (4) of the heat treating oven is for this purpose connected to gas inlet lines (9 and 10), one for the admission of the cooling gas and one for the admission of the flushing gas (H.sub.2 and N.sub.

Abstract: Very low-pore, thick nitride cases may be obtained in a short time during a gas nitriding process in accordance with the invention. This process includes nitriding in a gaseous mixture containing about 5 to 95% by volume ammonia and about 95 to 5% by volume nitrogen. The nitriding process is most preferably carried out at essentially a constant pressure above about 0.2 MPa.

Abstract: Hardening-shop wastewaters can be removed without salt incrustations and without creating harmful exhaust steam during the evaporation of the wastewaters only if the heat is supplied across the free liquid surface to temperatures of 50.degree. C. to 85.degree. C. and a flow of air is conducted across the free liquid surface.

Abstract: A vacuum furnace for heat treatment of metallic workpieces wherein the heat conductors are formed as conduits fitted with bore holes and connected by electrical insulators to coolant gas distributor.

Abstract: A process for heat treatment of metallic workpieces by heating in a vacuum furnace followed by quenching in a coolant gas under above-atmospheric pressure and with coolant-gas circulation.