What’s the vacuum furnace ?

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What’s the vacuum furnace ?

A vacuum furnace is a type of furnace that can heat materials, typically metals, to very high temperatures and carry out processes such as brazing, sintering and heat treatment with high consistency and low contamination.

In a vacuum furnace the product in the furnace is surrounded by a vacuum. The absence of air or other gases prevents heat transfer with the product through convection and removes a source of contamination. Some of the benefits of a vacuum furnace are:
1.Temperature can be controlled within a small area
2.Low contamination of the product by carbon, oxygen and other gases
3.Quick cooling (quenching) of product.
4.The process can be computer controlled to ensure metallurgical repeatability.

Heating metals to high temperatures normally causes rapid oxidation, which is undesirable. A vacuum furnace removes the oxygen and prevents this from happening.

An inert gas, such as Argon, is typically used to quickly cool the treated metal back to non-metallurgical levels after the desired process in the furnace. This inert gas can be pressurized to two times atmosphere or more, then circulated through the hot zone area to pick up heat before passing through a heat exchanger to remove heat. This process continues until the desired temperature is reached.

vacuum furnace structure:
Vacuum furnace is composed of furnace body, vacuum unit, hydraulic system, control system, cooling system and other parts. For gas-cooled vacuum furnace, nitrogen gas storage tank should be provided. In order to prevent water shutdown or insufficient water pressure, high-altitude water tank should be provided to prevent seals and electrodes from burning out or ablating due to water shutdown. The furnace body and door of vacuum furnace are welded and pressed by high strength steel plate. It is a double water jacket structure. The door of vacuum furnace is opened and closed by gear and rack drive. It is flexible and convenient.
The heating chamber is a circular structure. The graphite tube heater and the cooling gas nozzle distribute uniformly around the heating chamber at 360 degrees. The high-grade carbon felt and flexible graphite paper are used as insulation materials. The structure is light and fixed.
According to the form of heating, vacuum furnace can be divided into two types: external heating type and internal heating type. Internal heating furnace is the preferred type of vacuum furnace manufacturer. According to the different structure, it can be divided into single chamber, double chamber, three chambers and continuous vacuum furnace. There are gas-cooled, oil-cooled and gas-oil dual-purpose furnace. Vacuum gas quenching can quench stainless steel, high alloy die steel, high speed tool steel and Iron-Nickel Base Alloy by using nitrogen with purity over 99.999%. ZZ1 and 222 vacuum quenching oils with low saturated vapor pressure are used for quenching alloy steel.

Heating materials used in vacuum furnaces:
The heating elements of vacuum furnaces are divided into metals and nonmetals.
A. Metal heating elements are usually divided into two types: one is precious metals, such as molybdenum, platinum, tungsten, tantalum, etc., and the other is general metals, such as nickel-chromium heat-resistant alloy, iron-chromium aluminum alloy, molybdenum-tungsten alloy, etc.
B. non-metallic heating elements include two kinds of graphite and compound. The compounds are silicon carbide, molybdenum silicide, molybdenum oxide two and so on. Silicon carbide is easy to bond and decompose at high temperature, while two molybdenum oxide softens at 1300 degrees. Only graphite has the characteristics of good machinability, high temperature resistance, good resistance to quench and heat, good plasticity, large radiation area, good resistance to thermal shock and so on, so it is suitable for making heating elements.

vacuum furnace principle:
Vacuum furnace uses the phase change of heat medium water for heat exchange. The heat released from fuel combustion is absorbed by heat medium water. When the temperature rises to the saturated temperature of a certain vacuum state, it evaporates to saturation and vapor, and completes the first phase change process. The condensate flow into the evaporation chamber continues to absorb heat and complete the phase change cycle. The lower structure of the vacuum hot water boiler consists of a combustion chamber and a heat transfer tube bundle; the upper part is a vacuum chamber, in which a U-tube heat exchanger is inserted; and the vacuum chamber is connected with a suction unit to keep the vacuum chamber stable, and the non-condensable gas in the vacuum chamber is pumped out to improve the heat transfer efficiency of the U-type heat exchanger.

vacuum furnace function:
1. Vacuum quenching (tempering, annealing) is a method to achieve the desired performance by heating and cooling the material or parts in vacuum according to the process regulations.
2. Vacuum brazing is a welding process in which a group of weldments are heated to the melting point of the filler metal under vacuum condition, but below the melting point of the base metal. (brazing temperature varies from material to material).
3. Vacuum sintering is a method of sintering the adjacent metal powder grains into parts by adhesion and diffusion when the metal powder products are heated in vacuum.
4. Vacuum plus magnetism is mainly applied to metal materials and magnetic treatment.

Vacuum furnace type:

High temperature vacuum brazing furnace

High Temperature Vacuum Sintering Furnace

More Vacuum Furnace Types