PRODUCT CATEGORIES

Vacuum Heat Treatment Furnace

Vacuum Sintering Furnace

Vacuum Brazing Furnace

Vacuum furnace manufacturer analyzes the reasons for insufficient vacuum brazing rate of automobile aluminum oil cooler

The stacked vacuum brazing oil cooler is a safety part on the car, and the reliability requirements are high. The burst pressure is required to be greater than 4MPa, the pressure is alternating for 500,000 times, and the weld brazing rate is >60%. The air tightness and overall strength of the weld are required to be high.

Reasons for insufficient vacuum brazing brazing rate of automobile oil cooler

1. Insufficient vacuum degree

The vacuum furnace leaks or the vacuum rate is low, resulting in excessive oxygen partial pressure in the furnace and the oxide film is not effectively removed. Vacuum brazing requires the vacuum degree to reach below 2.0×10-³Pa, otherwise the wettability of the brazing material may deteriorate.
The vacuum brazing furnace that has not been used for a long time has not been fully dried, and the residual water vapor affects the vacuum environment.

2. Unreasonable process parameters

The heating rate is too slow: the residence time in the solid-liquid phase interval of the brazing material is too long (such as using high heat capacity tooling or too much furnace loading), resulting in the volatilization of low melting point components (such as Mg, Bi), changing the composition of the brazing material and reducing wettability. Insufficient holding time: insufficient diffusion and weak interface bonding.

3. Tool design issues

The tool has a large heat capacity (such as stainless steel), which prevents the workpiece from heating up evenly and quickly, exacerbating the volatilization of the solder.
The assembly gap is too large or the clamping force is insufficient, resulting in the failure of the capillary action and the inability of the solder to fill the gap.

4. Improper surface treatment

The oxide film on the surface of the parent material has not been completely removed (such as insufficient alkali washing), or secondary pollution (such as grease and dust) occurs during the assembly process.

5. Poor matching between the solder and the parent material

The solder composition is not adjusted according to the heat capacity of the parent material. For example, a solder with a lower liquidus temperature (such as AA4005) is required for high heat capacity areas.

Vacuum brazing improvement measures

1. Optimize the vacuum process
Improve the vacuum degree: check the sealing of the furnace body and dehumidify the furnace (extend the furnace time at low temperature, such as keeping at 100℃ for 2 hours and gradually increasing to 500℃).
Heating in stages: preheat slowly below 500°C to ensure uniform heating of the workpiece; quickly heat the solid-liquid phase of the brazing material to reduce volatilization.
2. Adjust process parameters
Shorten the brazing holding time: avoid excessive volatilization and ensure sufficient diffusion (adjust the time according to the material thickness).
Lower the brazing temperature: for sensitive areas (such as thin-walled parts), use brazing materials with lower liquidus temperatures (such as AA 4104 Bi-containing brazing materials).
3. Tooling optimization
Replace part of the stainless steel with graphite: reduce the heat capacity of the tooling and increase the heating rate.
Reasonably design the assembly gap: ensure capillary action, control the gap at 0.05–0.15 mm, and use moderate clamping force to prevent deformation.
4. Strengthen cleaning and surface treatment
Thorough alkaline cleaning: use 60°C alkaline cleaning solution to remove the oxide film, dry in time after cleaning and avoid secondary contamination. Use high-quality or imported composite aluminum foil: If the composite material has no advantages in quality and cost, use imported materials to improve wettability.
5. Control the amount of furnace loading and batches
Reduce the amount of single furnace loading: ensure the uniformity of furnace temperature and avoid local overheating or insufficient heat.
Vacuum brazing example reference
The stainless steel EGR cooler vacuum brazing case (using 316L stainless steel + Ni-based brazing filler metal) improves the qualified rate through the following measures: Select high thermal conductivity graphite tooling to shorten the heating time.
Use a high-performance furnace body with a vacuum degree of ≤5×10-³Pa and regularly maintain the sealing system.
Before vacuum brazing, stress relief anneal the workpiece to reduce the risk of deformation.

SIMUWU vacuum furnace manufacturer brings you summary
The insufficient brazing rate requires comprehensive improvement in four aspects: vacuum environment, process parameters, tooling design, and material matching. The focus is on controlling volatilization, optimizing heating, and ensuring interface cleanliness, and finally achieving full metallurgical bonding of capillary caulking with the interface.