What is a vacuum furnace?

A vacuum furnace is a furnace that heats materials to very high temperatures and performs processes such as sintering and heat treatment with high consistency and low contamination. The product in the furnace is surrounded by a vacuum. No air or other gases can transfer heat to the product by convection and eliminate sources of contamination.

Vacuum Furnace Structure

The vacuum furnace consists of a furnace body, vacuum unit, hydraulic system, control system, cooling system, and other parts. The vacuum furnace body and the furnace door are welded and pressed by a high-strength steel plate, and the structure is a double-layer water jacket. The opening and closing of the vacuum furnace door adopt rack and pinion transmission. Flexible and convenient.

The graphite tube heater and cooling gas nozzle are evenly distributed 360 degrees around the heating chamber. Insulation material adopts high-grade carbon felt and flexible graphite paper. Lightweight and fixed structure.

According to the heating form, vacuum furnaces can be divided into two types: externally heated and internally heated. Internally heated furnaces are the preferred type for vacuum furnace manufacturers. Vacuum quenching uses nitrogen of 99.999% purity or more for stainless steel, high alloy dies steel, high-speed tool steel, and iron-nickel-based alloys.

Features of Vacuum Furnaces

The unique process construction of the vacuum furnace makes it resistant to vibration and has a certain degree of heat resistance, relatively good corrosion resistance, no collapse, no pollution, and a relatively long service life. The thermal conductivity is relatively low, the thermal fusion is relatively excellent, with relatively stable chemical properties, and also has a certain excellent tensile strength, including corrosion resistance and other characteristics.

The working principle of vacuum furnace

The vacuum furnace uses the phase change of the hot medium water for heat exchange. The heat released from fuel combustion is absorbed by the hot medium of water. When the temperature rises to a certain vacuum state of saturation temperature, evaporation for the saturated state and gasification, complete the first phase change process. The condensate flowing 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 bundle of heat transfer tubes; the upper part is a vacuum chamber, and a U-tube heat exchanger is inserted in the vacuum chamber; the vacuum chamber is connected to a pumping device to keep the vacuum chamber stable and pump out the non-condensable gas in the vacuum chamber to improve the heat transfer efficiency of the U-tube heat exchanger.

Inert gas 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 twice or more the atmospheric pressure and then circulated through the hot zone area to absorb heat, which is then removed through the heat exchanger. This process continues until the desired temperature is reached.

Vacuum furnace functions

1、Vacuum quenching is a method of heating and cooling a material or part in a vacuum according to a process protocol to achieve the desired properties.

2、Vacuum brazing is a welding process in which a group of weldments is heated under a vacuum to the melting point of the filler metal, but below the melting point of the base material.

3、Vacuum sintering is a method of sintering adjacent metal powder grains into parts by adhesion and diffusion when the metal powder products are heated in a vacuum.

Advantages of vacuum furnace

1. Controllable temperature range

2. Uniform temperature in the range of 1100-1500°C

3. Low contamination of the product by carbon, oxygen, and other gases

4. Rapid cooling of the product (quenching)

5. Process can be computer controlled to ensure metallurgical repeatability

6. No heating of the metal to high temperatures and resulting oxidation

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