PRODUCT CATEGORIES

Vacuum Heat Treatment Furnace

Vacuum Sintering Furnace

Vacuum Brazing Furnace

Common defects of vacuum brazing and their solutions

Common defects of vacuum brazing

1. Dissolution
Reason: The brazing material does not match the base material, forming a low melting point phase. The heating rate is too slow or the holding time is too long. The vacuum brazing temperature is too high or the local temperature is uneven.
Solution: Replace a more matching brazing material grade. Rapidly heat up when approaching the melting point of the brazing material to reduce the amount of furnace loading. Reduce the vacuum brazing temperature and shorten the holding time. Reduce the weight of the tooling and use materials with low heat capacity such as graphite.
2. Discontinuous brazing seams (leaky welding, incomplete brazing)
Reason: Insufficient amount of brazing material or too large connection gap. The assembly gap is too large to form a capillary effect. Insufficient vacuum degree, the oxide film is not completely removed. The brazing temperature is too low or the time is too short.
Solution: Increase the amount of brazing material and reduce the connection gap. Increase the clamping force of the tooling to ensure that the gap remains unchanged in the hot state. Extend the holding time and increase the vacuum degree to the requirement (such as ≤6.0×10-³Pa). Check the pressure rise rate of the vacuum furnace and adopt a staged temperature rise strategy.
3. Flowing
Reason: Insufficient tooling rigidity leads to increased gaps, excessive wettability, and too long a stay time of the solder in the liquid state.
Solution: Improve tooling rigidity and reduce thermal deformation. Reduce the amount of furnace loading or reduce the amount of furnace loading in batches. Rapidly increase and decrease the temperature in the solid-liquid phase interval of the solder. Use hollow tooling or graphite to replace steel to reduce heat capacity.
4. Porosity (pinhole)
Reason: Low vacuum degree (such as >2.0×10-³Pa) hinders the escape of bubbles. The solder contains low melting point and high vapor pressure elements (such as Zn, Mg).Surface oxide film or moisture residue.
Solution: Set a heat preservation platform near the melting point of the solder to release the pressure in the furnace. Control the content of high vapor pressure elements in the solder. Thoroughly clean and dry the workpiece before vacuum brazing to extend the vacuum time.
5. Low strength of vacuum brazing
Reason: Insufficient diffusion (short holding time or uneven temperature). Oxidation of base material or brazing material (insufficient vacuum or leakage). Change of brazing material composition due to volatilization/corrosion.
Solution: Extend the holding time and accelerate diffusion by heating in sections. Reduce the vacuum pressure and check the leakage rate of the equipment. Adjust the concentration/time during alkali cleaning and treat the brazing material and base material separately.
6. Deformation of brazed workpiece
Reason: Uneven thermal stress caused by too fast heating/cooling rate. Excessive clamping force of tooling or mismatch of thermal expansion.
Solution: Stress relief annealing of components before vacuum brazing. Rapid heating at 500℃ and above and set up an isothermal platform. Control the cooling rate in stages and optimize tooling design and materials.

Control of key process parameters of vacuum brazing

1. Vacuum brazing temperature: usually at least 60℃ lower than the melting point of the base material, to ensure the fluidity of the brazing material and avoid the melting of the base material.
2. Insulation time: to ensure that the core of the base material reaches the brazing temperature and meets the decomposition time of the oxide film (1-2 seconds).
3. Vacuum degree: pre-vacuuming must reach 10-4Pa level, and the working vacuum degree is not higher than 6.0×10-³Pa.
4. Environmental control: humidity <60%, parts must be assembled and brazed within 24 hours after cleaning.

Vacuum Brazing Furnace