Aircraft engine rectifier vacuum brazing

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The material of the 5~8 stage rectifier of the aero-engine is Ti-6AI-4V titanium alloy. It is required to braze 60~80 blades to the inner and outer rings at the same time. The smaller the amount of deformation required as a whole, the better.

When assembling before vacuum brazing, the blades are inserted from the outer ring piece by piece, so that the inner ends of the blades are inserted into the grooves of the inner ring. Since the blade has a certain degree of twist, it is difficult to ensure the brazing gap in this assembly. To this end, titanium alloy foil is used to fill the large gap, and theφ1mm filamentary BAg72CuNi solder is prepared in a U shape and placed at the junction of the blade and the outer ring; 0.1mm titanium foil is pressed on the blade and the outer ring, and a pistol capacitor is used. The spot welding of the energy storage spot welding machine keeps the blade, the outer ring and the solder in relative positions. The prepared brazing filler metal is placed on the outer end blade of the inner ring again. Choose the vacuum degree in the cold state as 5*10^-3Pa, and keep the vacuum degree in the furnace not lower than 10^-1Pa when heating. If the vacuum degree tends to be lower than 10^-2Pa, the vacuum degree in the furnace can be increased by stabilizing the temperature. The vacuum brazing temperature is 850C; the vacuum brazing holding time is 10±2min.

Main points of vacuum brazing process:

Titanium and titanium alloys must be well degreased and removed from the oxide film before vacuum brazing. Degrease with a chloride-free solvent such as acetone, alcohol, etc. The oxidation film can be removed by sandblasting, or by adding 20~30mL of HNO per liter of water at room temperature, and 30-40mL of HCI solution for 5~10min.

In order to ensure high-quality joints, it is more appropriate to carry out vacuum brazing under a vacuum of 10^-2Pa in production. The heating speed is fast, the holding time is short, the compound layer in the interface area is thin, and the joint performance is good. Therefore, the vacuum brazing temperature and the vacuum brazing holding time must be controlled so that the brazing material flows to fill the brazing gap.

The a+β titanium alloy is used in the annealed solid solution or aging state. If vacuum brazing is performed below the heat treatment temperature, the brazing process can only be arranged at the end, otherwise the heat treatment cannot be performed after brazing. If the brazing temperature can be selected When it is consistent with the heat treatment requirements and is higher than the heat treatment temperature, the welding is started, then the cooling after vacuum brazing is consistent with the annealing system of the material, and the purpose of both brazing and heat treatment can be achieved. When brazing β alloy with aluminum-containing solder, the heating rate must be selected correctly. If the heating is too slow, aluminum segregation will occur, which will increase the melting temperature of the solder or create voids in the brazing seam.

Vacuum furnace equipment selection：SIMUWU is a vacuum brazing furnace equipped with three-stage pumps, which can meet the brazing requirements of qualified products, and can customize equipment according to product size and output requirements.

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