Heat Threatment Systems with Graphite Resistance Heater

Characteristics

COV heat treatment systems are high performance most efficient furnaces with a wide working-temperature and application range. Due to the compatibility with all kind of process gases and the fully automatic process runs they are especially suitable for the economic application in industrial productions.

COV Heat Treatment Systems with Graphite Resistance Heater

Applications:

operating temperatures up to 1.100 °C: heat treatment, brazing, reduction, degassing and debinding

operating temperatures up to 1.350 °C: heat treatment, brazing, degassing, debinding and sintering

operating temperatures up to 1.600 °C: debinding and sintering of hard metals

operating temperatures up to 1.800 °C: sintering of non-oxydic ceramics

operating temperatures up to 2.000°C: CVD- and pyrolytic processes, degassing and cleaning, sintering

operating temperatures up to 2.200 °C: CVD-processes, degassing and cleaning

Depending on the process requirements furnaces with operating temperatures up to 3.000 °C are available.

Special

Applications:

Reduction and degassing of water atomized metal powders (1.100 °C)

Powder production by nitriding (Si3N4) or carburizing (refractory metal carbides) (1.400 - 2.000 °C)

CVD-processes, e.g. coating of graphite parts with SiC (1.800 °C)

Cleaning of graphite under reactive gases (2.200 °C)

Pressure-less sintering of non-oxydic ceramics as e.g. Si3N4 and SiC (1.500 - 1.900 °C)

Benefits for users

Especially robust construction with high process integrity and a quite universal field of application make a COV furnace an investment with optimal cost-benefit-relation

System Design

The heating insert made of graphite with graphite tube or rod heating elements arranged uniformly all around the hot zone is forming the heart of the furnace. The thermal insulation surrounding the heating zone is made of graphite hard-felt and shields the heat radiation from the double-walled water-cooled vacuum vessel. The design of the heating insert provides for excellent and long lasting temperature homogeneity. Mechanically heavy-stressed parts in the hot zone are made of high quality carbon-fibre re-inforced graphite materials (CFC). According to process requirements the COV series systems can be of horizontal front loading or vertical top or bottom loading design.

A COV heat treatment plant is mainly consisting of: the water-cooled furnace vessel, the heating insert, the vacuum pumping unit, the forced gas cooling device, the power supply and the control cabinet. These main assemblies are combined in different versions according to the application requirements. In many applications the furnaces are equipped with a special condensation device for the removal of binders in the heat treatment materials incorporating a closed charge recipient (e.g. for debinding of the green powder compacts of sintering charge loads).

As may be necessary for the desired process various options are available for protective gas or high vacuum operation. COV furnaces for high temperature brazing under vacuum with operating temperatures up to 1.350°C are available in vertical design with a bottom loading facility and as horizontal batch type furnaces with a fork lift or hearth carriage. The systems are equipped with a fully automatic process control including application of protective or reactive gases. A variety of pumping systems ensures best adaptation to the process requirements. The brazing process is controlled by thermocouples measuring directly at the charge load. As an option forced gas circulation can be provided for a shorter cooling down time after the completion of the brazing process. COV furnaces for the sintering of hard metal combine the dewaxing and sintering of hard metal compacts in one heating cycle.

The organic binding agents, usually paraffines or polyethyleneglycols, are being removed in the beginning of the process. To avoid contamination of the heating insert and the furnace interior by the binder vapours the charge load is totally encapsulated in a graphite recipient. The binder vapours are directly lead to an external condenser and residualless removed from inside the furnace. After debinding the graphite recipient is automatically opened to ensure a good evacuation and an optimum sintering atmosphere. During the sintering process the evaporation of Cobalt is prevented by automatic vacuum pressure control.

Treatment with reactive respectively inert gases with automatic flow and pressure control is performed automatically according to preset control programs. A forced gas cooling system provides for a fast cooling down of the charge and short cycle times by circulating the gas by means of a blower inside the furnace or via an external heat exchanger.