Metallic Heated
MOV Heat Treatment Furnaces with Metal Resistance Heater
Characteristics
Heat Treatment furnaces (MOV) are ideal for the treatment of sophisticated materials if high temperatures and an absolutely clean hydro-carbon free atmosphere are required. Due to the ultrahigh vacuum atmosphere as well as the extreme temperature homogeneity and the fully automatic process the furnaces are especially suitable for the economic application in industrial and medical productions, i.e. for brazing of vacuum interruptors, parts of x ray tubes, heat exchangers, parts used in the medical and aerospace industry and parts for cleaning processes.
Furnace design
MOV-heat treatment furnaces are cold-wall furnaces with water-cooled double wall vessel out of stainless steel. The material to be treated is heated by full metal resistance heater arranged around the working chamber. The heat is transferred by radiation. The heating insert is equipped with heating elements consisting of materials suiting the desired maximum temperature, such as molybdenum, tantalum or tungsten. Thermal insulation is provided by metal sheets or multi-layer foils or, for temperatures below 1.400 °C, also sandwich-constructions with inner and outer metal layers and an insulation graphite felt inbetween. For temperatures up to 1.700 °C metal wire heaters are fixed and supported by aluminium oxide insulators.
If higher temperatures are involved tungsten heaters in self supporting ceramicless design are used. The basic equipment of the furnace also includes a sight glass allowing optical temperature measurement. A three-phase high-current transformer is used for the power supply. The heating capacity is infinitely controlled by a thyristor controller.
The furnace vessel and, thus, the working chamber can be arranged vertically or horizontally. Vertical furnaces are equipped for charging from top or bottom optionally. All furnaces can be equipped with mechanical charging devices. The all-metal design of the MOV furnaces is particularly well suited for high vacuum operation. Due to its high vacuum conduction short pumping times and low ultimate vacuum pressures are ensured. The sandwich-type insulation for low temperature applications provides for a better energy exploitation. According to the process requirements, ultimate operating pressures in the heated and loaded furnace up to approx. 10E-6 mbar can be realised. Appropriate accessory equipment also allows operation under partial pressure or overpressure protective respectively process gas atmospheres.
A MOV heat treatment furnace mainly consists of: the furnace vessel, the vacuum pumping unit, the power supply and the control cabinet. These main system modules are combined in different versions according to the application requirements.