The main structure of the vacuum brazing furnace is horizontal and single chamber heating structure. It consists of furnace body, heating chamber, vacuum system, air cooling system, air charging system, partial pressure system, water cooling system and electrical control system.
Main body of vacuum furnace
The main body of vacuum furnace is composed of furnace body and heating chamber. The shell of the furnace shell, the furnace door and the motor cover are welded by the double layer cylinder, the double elliptical head and the flange by the airtight welding seam. The double layer cylinder is a channel, and the inner cooling water is inside. A locking ring locking structure is adopted for the furnace cover. The heating chamber is designed as a cylinder and consists of a frame and a graphite felt.
The heating system includes heating power supply, temperature control system and heating element. The magnetic regulator is used in the heating power supply, the voltage regulation is controlled by DC excitation, and the closed loop automatic control is implemented according to different control signals. The DC excitation power supply is controlled by the bidirectional thyristor. The temperature control instrument with self-tuning function, the temperature inside the furnace thermocouple will be converted into electrical signals, the temperature detected by the current value and the set value of the difference, after the PID operation as output signals, control the bidirectional thyristor conduction angle, the average heating power of the heating element so as to effectively control the temperature, phase consistent with the heating curve set. The heating elements are 18 graphite tubes, which are evenly distributed along the circumference of the hot zone by triangle connection, so as to provide a good furnace temperature uniformity. The heating element is connected with the external connection through 3 water cooling electrodes.
The main pump is KT-500 type diffusion pump, the front pump is ZJ-600 roots pump and 2X-70 rotary vane mechanical pump. They are equipped with high vacuum valve, main road valve, bypass valve and electromagnetic pressure differential valve which is linked with mechanical pump. The mechanical pump is a rough vacuum device, the mechanical pump after a series of roots pump, roots pump with high pumping rate, so the vacuum pumping system to a higher degree of vacuum; but only in the pumping system of pressure to allow entrance pressure of roots pump, roots pump to start work, otherwise will be due to overload and overheating and damage. The diffusion pump is a high vacuum device. It diffuses the gas molecules in the vacuum system into the high speed steam jet, and discharges the air from the front pump to the air to complete the pumping action.
Air cooling system
In the rear of the vacuum furnace body, equipped with 1 sets of three-phase asynchronous motor, reduce the gas temperature by a heat exchanger after dome, air inlet and impeller through the hot compartment in the working area in the furnace, and then return to the implementation of circular cooling radiator.
Water cooling system
The water cooling system consists of stainless steel stop valve, water inlet, drainage box, hydraulic electric contact pressure gauge and so on. The inlet is equipped with 63.5 mm (2.5in) stainless steel ball valve, and the outlet is equipped with 101.6 mm (4 in) flange, which only needs to be connected with the user’s circulating water system.
Partial pressure system
The partial pressure system consists of an electromagnetic vacuum charging valve and an adjustable needle valve. In the process of copper brazing, high purity nitrogen or argon can be charged when partial pressure control is needed, and the partial pressure range is controlled at 5~500 Pa.
The pneumatic system consists of a large diameter pneumatic stop valve, a gas collecting and discharging valve, a vacuum electric contact pressure gauge, etc.