Can a high-temperature vacuum brazing furnace be filled with nitrogen gas?
11-20-2025 Author: KJ technology
The high-temperature vacuum brazing furnace can be filled with nitrogen gas, which has significant advantages in specific process scenarios, but the purity and process parameters need to be strictly controlled. The specific explanation is as follows:
1. The core function of nitrogen gas supply
Inert protection to prevent oxidation
Nitrogen is chemically stable at high temperatures and can displace oxygen from the furnace, forming an inert protective layer. For example, in the brazing of aluminum alloy heat exchangers (such as car water tanks and condensers), introducing high-purity nitrogen gas (≥ 99.995%) can prevent surface oxidation of the welded parts, reduce the amount of oxide scale generated, and improve the bonding strength of the weld seam.
Optimize the wetting properties of brazing materials
In a pure nitrogen environment, the flowability and diffusivity of brazing materials (such as silver copper based and nickel based brazing materials) are significantly enhanced, which can uniformly wet the surface of the base material and form dense joints. For example, in the brazing of dissimilar materials between stainless steel and titanium alloy, nitrogen gas can improve the mechanical strength of the joint.
Enhance product appearance and performance
Nitrogen protection can reduce surface contaminants (such as oxide layers and carbon deposits) on welded components, avoid subsequent cleaning or polishing steps, and lower production costs. For example, in the brazing of aircraft engine blades, nitrogen gas can achieve high surface smoothness of the blades, meeting the requirements of high-temperature and high-speed rotation conditions.
Extend equipment lifespan
Moisture and impurities in low purity nitrogen may corrode furnace components such as heating tubes and sensors, while high-purity nitrogen can reduce such risks. For example, long-term use of high-purity nitrogen in vacuum brazing furnaces can extend the lifespan of heating elements.
2. Typical application scenarios of nitrogen gas supply
Brazing of aluminum alloy products
Effect: The porosity of the weld seam is lower, the leakage rate is reduced, and it meets the mass production needs of heat exchangers in the automotive and aviation fields.
Brazing of stainless steel and titanium alloy
Effect: Higher joint strength and improved corrosion resistance, suitable for fields such as chemical and marine engineering.
Heat treatment of high-temperature alloy parts
Effect: The thickness of the oxide layer on the surface of the parts is smaller, and the high-temperature strength retention rate is higher, meeting the requirements of key components such as aircraft engine turbine blades.
3. Key control points for nitrogen gas flow
Purity requirements
The purity of nitrogen must be ≥ 99.99%, otherwise impurities such as oxygen will react with the weld, resulting in thickening of the oxide layer and a decrease in weld strength.
flow control
The flow rate needs to be adjusted according to the furnace volume and process requirements. Low flow rate may result in insufficient protection effect, while high flow rate may cause turbulence in the furnace airflow, affecting temperature uniformity.
Timing of entry
Heating stage: After initially vacuuming to below 1 × 10 ⁻ Pa, nitrogen gas is introduced to create a protective atmosphere.
Insulation stage: Maintain a stable nitrogen flow rate to ensure a lower oxygen content in the furnace.
Cooling stage: Continuously introduce nitrogen gas before cooling to below 200 ℃ to prevent the welded parts from re oxidizing.
safety measures
Nitrogen is an inert gas, but high concentration environments may cause suffocation of personnel. Ensure good ventilation in the furnace room and equip it with oxygen concentration monitoring and alarm devices during operation.
