vacuum furnace

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Vacuum Furnace Standard Structure and Characteristics

The main machine of vacuum furnace is horizontal and single chamber structure, which is composed of pressure furnace body, furnace door, heating chamber and air cooling system.

Furnace body, door and motor cover are double-wall water-cooled structures. The inner and outer walls of the furnace are welded with high quality carbon steel sheets. One end is welded with the flange of the furnace door, the other end is welded with the flange of the motor with the head and the air-cooled system, and the cooling water is passed in. There is a two-way sealing structure between the furnace body and the furnace door. The vacuum furnace is sealed under negative pressure and high pressure gas cooling by locking ring. The rear part of the furnace body is equipped with a high-power air-cooled motor, and the outer part of the motor is equipped with a motor cover with cooling water. The outer wall thickness of the water jacket of the furnace body is 8 mm and the inner wall thickness is 12 mm.

The heating chamber (furnace gallbladder) is composed of heat insulation layer, heating element, graphite nozzle and charging table.

The insulation layer consists of six layers of graphite felt and one layer of molybdenum sheet (0.5mm). The properties of molybdenum sheet are as follows: density 10.2g/cm³, melting point 2620±10℃, linear expansion coefficient （al）20-1000℃ 5.8′10-6/K, tensile strength（sb）590-785MPa. The insulation layer is fixed on the heating chamber frame composed of 2 mm porous stainless steel (304) plate and angle steel ring. Angle steel ring is 6mm thick stainless steel. The front and rear cover are equipped with fixed air doors.

The heating element is made of three high graphite tubes and insulated by ceramic parts. The heating elements are uniformly arranged along the circumferential direction of the inner wall of the insulation layer, with uniform heating and low heat loss, and can be disassembled separately and replaced conveniently.

The graphite nozzle is a multi-row graphite nozzle, which distributes uniformly in the heating chamber along the circumferential direction of the inner wall of the insulation layer. During gas quenching, the gas is forced to eject uniformly from the graphite nozzle to achieve uniform quenching effectively.

The charging table is composed of graphite pillar, graphite furnace bed and AL2O3 partition bar on the furnace bed. This structure can prevent the bond between the charge plate and the graphite furnace bed at high temperature. The length of the furnace bed is 1200mm and three furnace beds are required.

Vacuum Furnace Air-cooled System: There are high-pressure and high-speed impeller fan, multi-stage copper-copper heat exchanger and air duct diversion device at the rear of the furnace body. When air-cooled, high-purity nitrogen or high-purity argon is filled. Driven by high-speed impeller fan, the gas is sucked into impeller through high-efficiency copper-copper heat exchanger. After impeller reversal, it is ejected evenly from graphite nozzle to workpiece through air duct diversion device, which makes the workpiece uniformly strong refrigeration. A forced high flow rate cycle is formed to realize rapid air cooling of the workpiece. The cooling fan is controlled by frequency converter, which can not only reduce the starting current of the motor and the voltage fluctuation of the power line, but also control the running speed of the motor to achieve energy-saving effect.

Vacuum Furnace Vacuum System: Vacuum unit consisting of H-150 slide valve pump, ZJ-600 Roots booster pump and vacuum valve and pneumatic baffle valve, flexible connector, electrical contact pressure gauge, gauge and its accessories installed in vacuum pipeline.

Because the primary pump and booster pump are installed, and the volume of the container is adequately reserved in the selection of the pump, which ensures the rapid emptying time of the system.

The electronic control system is composed of temperature program control, pressure controller and programmable logic controller (PLC), which can realize automatic program control and manual control.

Vacuum Furnace Temperature Control
Microprocessor Model: 3504 Digital Intelligent Program Section Regulator
3504 series is a digital intelligent program section loop regulator developed by Continental Company of England. Its precision is 0.1 level. It can set 50 curves and up to 500 segments. It contains many sets of PID parameters. It also has the regional PID function corresponding to segments or PV. It can automatically select the corresponding PID parameters according to the multi-zone temperature range set by the process. Deviation waiting function, in high quality heat treatment process, can ensure the processing time into the insulation section.

The recorder is a paperless recorder KT504 with accuracy of 0.2 grade and measurement error of ±0.2FS%.

Thermocouples are equipped with two sets of single “S” type ceramic tube thermocouples, one for temperature control, the other for recording and overtemperature alarm.

The pressure controller is fed back to the instrument by the pressure sensor on the furnace body. The instrument displays the pressure of the furnace body, so that the pressure to be quenched can be input on the pressure indicator. (1bar-6bar) control precision is 0.005Kpa.

The programmable controller is CP1E-N60, which controls the mechanical action. It can realize the automatic control of vacuum pumping, vacuum valve opening and closing, heating, air-cooled pressure, etc.

The control cabinet is equipped with a 15-inch touch screen, which can visually display the working state of the vacuum furnace. The vacuum furnace has the function of self-diagnosis of faults, such as water pressure, over-temperature, over-current, sound and light alarm and chain protection.

Vacuum Heat Treatment Furnace