Pit-Type Vacuum Furnace & Ovens

‌Operating Principle‌
Pit-type vacuum furnaces operate through a hermetically sealed vertical chamber design where workpieces are loaded via overhead crane. The triple-stage vacuum system initially evacuates air to 10⁻¹Pa via rotary vane mechanical pumps, followed by oil diffusion pumps reducing pressure to 10⁻⁴Pa range. For ultra-high vacuum processes (10⁻⁵Pa), turbomolecular pumps activate to remove residual gases through momentum transfer mechanisms. This oxygen-free environment prevents surface reactions during heating.

Thermal processing utilizes radiation heating from molybdenum-alloy heating elements arranged in 16 independent zones. Each zone employs dual closed-loop control: K-type thermocouples monitor temperature gradients while infrared sensors provide real-time emissivity correction, achieving ±1°C uniformity at 1300°C. Post-heating, programmable gas quenching injects high-purity N₂/Ar at 20bar pressure through strategically placed nozzles, enabling cooling rates up to 150K/s for martensitic transformations.

‌Core Heat Treatment Processes‌

1. ‌Bright Annealing‌

   • Process: Parts are heated to 800-1100°C under ＜5×10⁻⁴Pa vacuum, suppressing oxide formation through thermodynamic equilibrium control.
   • Metallurgical Effect: Eliminates decarburization in tool steels (e.g., H13) and preserves surface reflectivity of nickel superalloys.

2. ‌Vacuum Brazing‌

   • Process: Controlled H₂ atmosphere (dew point ≤-70°C) reduces metal oxides at 900-1200°C. Filler metals (BNi-2/BAg-8) flow via capillary action with wetting angles ＜10°.
   • Application: Aerospace turbine seal rings achieve joint strength ＞95% of base material.

3. ‌Diffusion Bonding‌

   • Process: Ti-6Al-4V components bonded under 10⁻³Pa vacuum at 90% melting point temperature (～1300°C) with 15MPa pressure.
   • Outcome: Intergranular diffusion creates monolithic structures with >99.9% density.

Vacuum oven, that is, in the furnace cavity of this specific space using a vacuum system (by the vacuum pump, vacuum measurement devices, vacuum valves and other components carefully assembled) will be part of the furnace cavity material discharge, so that the pressure in the furnace cavity is less than a standard atmospheric pressure, the furnace cavity space so as to realize the vacuum state, which is the vacuum furnace.

Product Description:

This is a device for heating in a vacuum environment. In the metal shell or quartz glass sealed furnace chamber with piping and high vacuum pump system connection. The vacuum degree of the furnace chamber can be up to 133×(10-2~10-4) Pa. The heating system in the furnace can be directly heated by resistance wire (such as tungsten wire), or can be heated by high-frequency induction. The temperature can reach about 3000℃. It is mainly used for ceramic firing, vacuum smelting, degassing and annealing of electric vacuum parts, brazing of metal parts, and ceramic-metal sealing.

Advantages

(1) The oxidation and decarburization of the surface of the workpiece during the heating process are eliminated, and a clean surface without deterioration layer can be obtained. This improves the cutting performance of tools that are only ground on one side during sharpening (e.g., twist drills are ground so that the decarburized layer on the surface of the grooves is directly exposed to the cutting edge).

2）No need for three waste treatment.

(3) Furnace temperature determination, monitoring and control accuracy is significantly improved. Thermocouple indication value and furnace temperature temperature to ± 1.5 ° c. But the temperature difference between different parts of a large number of workpieces in the furnace is large, if the use of dilute gas forced circulation, can still be controlled in the range of ± 5 ° c temperature difference.

(4) high degree of mechanical and electrical integration. On the basis of temperature measurement and control accuracy, workpiece movement, air pressure adjustment, power regulation can be pre-programmed settings, according to the step-by-step implementation of quenching and tempering.

(5) Energy consumption is significantly lower than the salt bath furnace. Modern advanced vacuum furnace heating chamber using thermal insulation materials made of heat-insulating walls and barriers, can be highly concentrated in the heating chamber of electric energy, energy saving effect is significant.

Function

Vacuum quenching (tempering, annealing) is a treatment method to achieve the expected performance by heating and cooling the material or parts under vacuum according to the process protocol.

Vacuum brazing is a welding process in which a group of welded parts is heated to a temperature above the melting point of the filler metal but below the melting point of the base metal in a vacuum state, and a weld is formed with the help of the filler metal's wetting and flowing of the base metal (brazing temperatures vary depending on the material).

Vacuum sintering that is, in a vacuum state, the metal powder products heated, so that adjacent metal powder grains through adhesion and diffusion and sintered into parts of a method.

Vacuum magnetization is mainly applied to the magnetization treatment of metal materials.

Classification

Vacuum furnace & Oven, i.e. vacuum heat treatment furnace, is distinguished according to the application equipment, which probably contains the following types:

Vacuum quenching furnace, vacuum brazing furnace, vacuum annealing furnace, vacuum magnetizing furnace, vacuum tempering furnace, vacuum sintering furnace, vacuum diffusion welding furnace, vacuum carburizing furnace and so on.

Vacuum oven is divided into vacuum resistance furnace, vacuum induction furnace, vacuum arc furnace, vacuum self-consumption arc furnace, electron beam furnace (also known as electron bombardment furnace) and plasma furnace, etc. according to the heating method.

Structure

Vacuum oven is generally composed of mainframe, furnace chamber, electric heating device, sealed shell, vacuum system, power supply system, temperature control system and outside the furnace transportation vehicle and so on. The sealed shell is welded with carbon steel or stainless steel, and the joint surfaces of the removable parts are sealed with vacuum sealing materials. In order to prevent the furnace shell deformation and sealing material heat deterioration, the furnace shell is generally water-cooled or air-cooled cooling. The furnace chamber is located in the sealed furnace shell. Depending on the purpose of the furnace, the interior of the furnace chamber is equipped with different types of heating elements, such as resistors, induction coils, electrodes and electron guns. Vacuum furnaces for melting metals are equipped with crucibles in the furnace chamber, and some are also equipped with automatic pouring devices and robots for loading and unloading materials. The vacuum system is mainly composed of vacuum pumps, vacuum valves and vacuum gauges.

Application

1.High-pressure high-flow rate gas quenching vacuum furnace

Mainly used for cold and hot work mold steel, high-speed steel, elastic alloys, high-temperature alloys, stainless steel, titanium alloys, magnetic materials and other materials, vacuum heat treatment.

2 double chamber high pressure gas quenching vacuum furnace

Mainly used for high pressure gas quenching of cold and hot working die steel, high-speed steel, elastic alloy, high temperature alloy, stainless steel, titanium alloy, magnetic materials and other materials, as well as vacuum sintering, vacuum brazing and other processes.

3.Double-chamber oil quenching gas-cooled vacuum furnace

It is mainly applied to bright quenching of tool steel, mold steel, bearing steel, spring steel and other materials.

4.Vacuum aluminum brazing furnace

Mainly applicable to automobile radiator, air conditioner evaporator, condenser, intercooler, radar grid antenna, waveguide, and all kinds of plate warping or tube sheet type heat exchanger vacuum welding.

5.Vacuum high temperature brazing furnace

It is mainly used for vacuum brazing of stainless steel, high temperature alloy, hard alloy, non-ferrous metal and other materials.