Vacuum atmosphere furnace

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Vacuum atmosphere furnace is a new heat treatment technology which combines vacuum technology with heat treatment technology. The vacuum environment of vacuum heat treatment refers to the atmosphere environment below one atmosphere pressure, including low vacuum, medium vacuum, high vacuum and ultra-high vacuum. In fact, vacuum heat treatment belongs to atmosphere-controlled heat treatment. Vacuum heat treatment refers to all and part of the heat treatment process carried out in vacuum. Vacuum heat treatment can achieve almost all the heat treatment processes involved in conventional heat treatment, but the quality of heat treatment is greatly improved. Compared with conventional heat treatment, vacuum heat treatment can achieve no oxidation, no decarbonization, no carburization, removal of phosphorus chips on the surface of workpiece, degreasing and degassing, so as to achieve the effect of surface brightness and purification.

In high vacuum atmosphere furnace, imported 1600 alumina polycrystalline fiber material is used in the furnace. It has good thermal insulation performance and imported high quality silicon carbon rod is used as heating element. Double shell structure, with air cooling and water cooling system, can quickly cool down, furnace door with circulating water cooling, side open door structure. It can rapidly increase and decrease the temperature to meet the different needs of production and R&D.

Main uses and application scope of vacuum atmosphere furnace:
Vacuum atmosphere furnace is widely used in ceramics, metallurgy, electronics, glass, chemical industry, machinery, refractories, new material development, special materials, building materials and other fields of production and experiment.

Powder sintering under atmospheric pressure.
The main advantages of vacuum furnace are:
(1) Reduce the harmful effects of harmful components (water, oxygen, nitrogen) in the atmosphere on the products. For example, it is very difficult to reduce the dew point of water content in electrolytic hydrogen gas to一40℃, and the dew point of water content at一40℃ is equivalent to that of vacuum at 133 Pa. It is not difficult to obtain such a vacuum.
(2) Vacuum sintering can be used for materials which are not suitable to use reducing or inert gas as protective atmosphere (such as sintering of active metals), or which are prone to decarbonization and carburization.
(3) Vacuum can improve the wettability of liquid phase to solid phase, conducive to shrinkage and improve the structure of the alloy.
(4) Vacuum sintering is helpful to remove impurities such as silicon, aluminium, magnesium and calcium or their oxides, and to purify materials.
(5) Vacuum is conducive to the removal of adsorbed gases, residual gases in pore and products of reactive gases, and has a significant effect on promoting the shrinkage in the later stage of sintering. For example, the porosity of the vacuum sintered cemented carbide is much lower than that of the hydrogen sintered cemented carbide.
(6) The sintering temperature of vacuum sintering is lower than that of gas-protected sintering. For example, the sintering temperature of cemented carbide can be reduced by 100℃-150℃. This is conducive to reducing energy consumption and preventing grain growth.

Metal volatilization often occurs during vacuum sintering. For example, the volatilization loss of cobalt occurs during sintering cemented carbide. By strictly controlling the vacuum, even if the pressure in the furnace is not lower than the vapor pressure of sintered metal components, the volatilization loss of metal can be greatly reduced or avoided. Another problem of vacuum sintering is decarbonization of carbon-containing materials. This occurs mainly in the heating stage. Oxygen, moisture in the residual gas and oxide in the powder can react with the combined carbon in the carbide or free carbon in the material to produce carbon monoxide which is extracted with the furnace gas. Decarbonization of carbon-containing materials can be solved by increasing carbon content in powder and controlling vacuum.

In order to improve the uniformity of heating speed and furnace temperature in vacuum sintering process, appropriate gas (inert gas or hydrogen) can be introduced into the initial stage of sintering. Similarly, the cooling rate of vacuum sintering can be improved by the method of swing-off circulating gas cooling. In order to prevent the formation agent from contaminating the vacuum system during sintering, the compact should be pre-fired before vacuum sintering to remove the forming agent.

In powder metallurgy, vacuum sintering is mainly used for sintering active metals and refractory metals such as beryllium, thorium, titanium, zirconium, tantalum, niobium, etc., sintering cemented carbides, magnetic alloys, tool steels and stainless steels, and sintering compounds that are easy to react with gases such as hydrogen, nitrogen and carbon monoxide.

Main functions and characteristics of vacuum atmosphere furnace:
1. Control accuracy: +1℃ furnace temperature uniformity: +1℃ (depending on the size of the heating chamber);
2. Easy to operate, programmable, PID self-tuning, automatic heating, automatic heat preservation, automatic cooling, without duty; can be equipped with computer communication through the operation of electric furnace (start electric furnace, stop electric furnace, pause heating, set heating curve, heating curve storage, history curve, etc.). Free software details are as follows: computer control system;
3. The heating rate is fast (the heating rate can be adjusted from 1℃/h to 40℃/min).
4. Energy saving (the furnace is made of imported fibers, high temperature resistance, heat and cold resistance);
5. The furnace body is exquisitely sprayed, corrosion-resistant, acid-resistant and alkali-resistant, and the air-cooled furnace wall temperature is close to room temperature in isolation from the furnace body.
6. Dual-circuit protection (over-temperature, over-voltage, over-current, segment couple, power failure, etc.).
7. Furnace materials imported refractories, good thermal insulation, high temperature resistance, rapid cold and heat resistance;
8. Temperature category: 1200℃ 1400℃ 1600℃ 1700℃ 1800℃;
9. Furnace body sealing and water-cooling structure: Seals: Seals are made of silicone rubber rings (260℃-350℃Celsius). Cooling structure: double shell, air-cooled + water-cooled.
Water cooling: In order to save resources, the electric furnace is equipped with hot water circulating pump and circulating water tank. The maximum heat resistance of hot water circulating pump is 160℃ hot water. The working time is more than one year without interruption. The circulating water tank is made of 304 stainless steel with a capacity of 150L-200L.
Circulating water radiator: adopt multi-channel pure aluminium water circulating radiator;
Water-cooled parts: furnace mouth, furnace door and furnace top of furnace inner shell;