Cemented carbide vacuum sintering furnace working principle
The multi-atmosphere cemented carbide vacuum sintering furnace is composed of furnace body, insulation layer, heating element, furnace front transformer, distribution cabinet (including control system), vacuum pump, various connecting pipes and valves, etc. The system composition is shown in the figure below.
The vacuum sintering furnace body is double wall water cooling design, the inner layer is made of high quality stainless steel plate. The cooling water system includes a feed branch pipe and a return tank. The optimal water flow of each system is manually adjusted. The water pressure test is used to determine whether the cooling water pressure is within the normal working range. The vacuum system is mainly composed of a rotary vane vacuum pump and a roots vacuum pump. According to the vacuum requirements of different sintering stages, the control system adopts position-controlled vacuum valve to control the vacuum degree. Solenoid valve is mainly used for power failure protection, pressure gauge for artificial observation of vacuum. When the protective gas (hydrogen, nitrogen, argon) needs to be filled in the vacuum furnace, its flow and pressure in the furnace are controlled manually. If the furnace is filled with hydrogen gas for degumming, open PEG valve and vent valve and ignite the hydrogen gas. The condenser is used to cool PEG glue or paraffin wax to avoid damage to the vacuum system.
The insulation layer is a rectangular box made of five layers of carbon felt sewn onto a stainless steel mesh frame. The heating element is a box-shaped whole composed of graphite heating elements, and its structural design can adapt to the heating and cooling of heating elements in the heating and cooling process. In consideration of the safety of the equipment and the heating graphite's own strength and surface power, a pre-furnace transformer is designed to supply power to the heating element to obtain low voltage and large current. There are three water-cooled copper power feeders sealed by vacuum in the sintering chamber, which are connected with the heating element through graphite rod at high temperature and insulated by special high-temperature ceramic bushing. Vacuum furnace temperature by the thermocouple, temperature control device adjusted according to the temperature set value and actual value calculation, a phase shifting control signal sent to the trigger board, through the three-phase regulating circuit to adjust the size of the furnace transformer primary side voltage before, and then change the vice graphite resistance of electric power transformer size, achieve the goal of control of furnace temperature.