What gases can be used in a high vacuum air quenching furnace?
11-18-2025 Author: KJ technology
The high vacuum air quenching furnace can be cooled by various inert or neutral gases, and the gas selection needs to be comprehensively considered based on material characteristics, process requirements, and economy. The following are common gas types and their application scenarios:
1. Nitrogen (N ₂)
Features: Low cost, easy to obtain, moderate cooling capacity.
Application Scenario:
Structural steel quenching: such as 42CrMo, 45 steel, etc., 2-5MPa nitrogen can achieve higher surface hardness and better core hardness.
Stainless steel treatment: Austenitic stainless steels such as 304 and 316L, nitrogen cooling can prevent carbide precipitation and maintain corrosion resistance.
Economic solution: suitable for mass production with moderate hardness requirements and cost sensitivity.
2. Argon (Ar)
Features: Low thermal conductivity (0.018 W/(m · K)), slow cooling rate, but extremely strong chemical inertness.
Application Scenario:
Active metal treatment: such as titanium alloys (TC4, TA15), magnesium alloys, etc., to avoid surface contamination caused by gas reaction.
High purity requirements: In fields such as aerospace and medical equipment, ensure that materials are free from impurities such as hydrogen and oxygen.
Thin walled cooling: With a high density of argon gas (1.78 g/L), it can reduce turbulence and lower the risk of deformation.
3. Helium (He)
Features: The highest thermal conductivity (0.151 W/(m · K)), extremely fast cooling speed, but high cost.
Application Scenario:
High speed steel quenching: such as M2, M42, etc., helium cooling can achieve high red hardness, significantly higher than oil quenching.
Ultra fine grain materials: materials that require rapid cooling to suppress grain growth, such as powder metallurgy high-speed steel and nanocrystalline alloys.
High temperature alloy treatment: Nickel based high-temperature alloys require high cooling rate solution treatment.
4. Mixed gases (N ₂+He, N ₂+Ar)
Features: Balance cost and performance through proportional adjustment, for example:
N ₂+He (volume ratio 3:1): The cooling rate is close to pure helium gas, reducing costs.
N ₂+Ar (volume ratio 1:1): Suitable for materials that are sensitive to oxidation but do not require rapid cooling.
Application Scenario:
Complex structural components, such as automotive transmission gears and aircraft engine blades, require a balance between hardness and deformation control.
Gradient cooling process: First, high-pressure helium gas is used to rapidly cool the surface, and then nitrogen gas is switched to slowly cool the core to reduce residual stress.
5. Special gases (hydrogen, carbon dioxide)
Hydrogen (H ₂):
Characteristics: High thermal conductivity (0.183 W/(m · K)), but flammable and explosive, requiring strict safety measures.
Application: Special quenching process for a very small number of high-temperature alloys (such as cobalt based alloys).
Carbon dioxide (CO ₂):
Characteristic: Fast cooling speed, but may cause carbide pollution.
Application: Experimental research or specific carbon steel treatment (requiring subsequent decarbonization treatment).
Gas selection principle
Material compatibility: Argon gas is preferred for active metals such as titanium and magnesium; Choose helium gas or mixed gas for high-speed steel and high-temperature alloys.
Hardness requirement: When extremely high hardness is required (such as high-speed steel red hardness), helium gas is used; Medium hardness with nitrogen gas.
Deformation control: Choose argon gas or low-pressure mixed gas for thin-walled and precision parts.
Cost effectiveness: prioritize nitrogen for mass production; High end manufacturing can accept the cost of helium or gas mixtures.
Typical Case
Automotive gears: using 2MPa nitrogen quenching, the surface hardness increases, the core hardness is high, and the deformation is smaller.
Aviation blades: quenched with 10MPa helium gas, achieving an increase in surface hardness of nickel based alloys, an increase in core hardness, and a reduction in residual stress.
Medical equipment: Pure argon cooled stainless steel with lower surface roughness, meeting sterile requirements.
