Machining Technology of Aero-Engine Sealing Ring

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Brazing technology is widely used in the connection of aero-engine structures, aviation instruments and the second power assembly, and has become a key technology in the manufacture of engine components. Vacuum brazing is used to heat the parts as a whole, with small thermal stress, small deformation of the workpiece, accurate control of process parameters, and stable product quality. It is especially suitable for complex welding and multi-part combination to achieve large area connections. Compared with other welding methods, vacuum brazing welding joints have good performance and stable weld quality, which is conducive to the welding of dissimilar materials.

The sealing ring of aero-engine is made of aluminum bronze (QAl7) and martensitic stainless steel (1Cr17Ni2) connected by vacuum brazing with HBAg72CuNiLi solder. The sealing ring is a ring structure composed of dissimilar materials. It belongs to the wearable sealing ring type. It is used for sealing the high-pressure turbine bearing of the engine. It requires good wear resistance and sealing performance. The inner side of the copper ring is machined with teeth groove.

SIMUWU manufactures vacuum furnace equipment including vacuum brazing, vacuum heat treatment and vacuum sintering. The following takes the RVB series vacuum brazing furnace produced by SIMUWU’ as an example to introduce the corresponding process parameters.

Process parameters:

Select HBAg72CuNiLi as solder. When silver-copper solder is brazing stainless steel, nickel plating on the surface of the base metal can improve the wettability and spreading ability of silver-copper solder; when silver-copper solder is brazing aluminum bronze, silver plating on aluminum bronze can prevent The Al diffuses to the solder, which can also prevent oxidation during brazing and reduce the generation of surface oxides.

The melting temperature of HBAg72CuNiLi solder is 766 ℃, and Li element has self-brazing effect, which can be used for brazing copper alloy and stainless steel. The structure of the part is a ring body, and the brazing filler metal with a thickness of 0.06 mm and a wire-shaped filler metal with a diameter of 1 mm are used. Because the copper ring has good electrical conductivity and the surface to be welded is silver-plated, the solder cannot be positioned during energy storage spot welding, and the solder is prone to fall off during the assembly process. Therefore, when presetting the solder, choose the stainless steel installation edge. Two layers of brazing filler metal are spot welded on one side of the circle, and two circles of filamentous brazing filler metal are placed in the groove on the mounting side as a supplement. The entire lap surface is evenly covered with solder to reduce defects such as unwelded and voids, and to improve the quality of brazing.

In order to prevent weld cracking during brazing shrinkage, brazing tooling is added during brazing. The tooling material is 1Cr17Ni2, and the thickness of one side is about 25 mm. During brazing, the parts are sleeved on the tooling. During the shrinkage process, the heat of the tooling slows down the shrinking speed of the copper ring, thereby reducing the possibility of cracking of the weld. At the same time, the tooling can also support the round copper ring and reduce the deformation of the copper ring after welding. . In order to avoid the connection between the tool and the part, spray the aluminum oxide coating on the surface of the tool.

The brazing parameters are as follows: pre-vacuum until the pressure in the furnace is lower than 2 × 10-2 Pa, and then start to heat up after the vacuum degree is reached. After the temperature is raised to 700 ℃, the partial pressure of argon is 3~20 Pa, and the temperature is kept for 3~7 min. , heat up to 870 °C, hold for 8-12 min, cool down to below 700 °C with the furnace, backfill the furnace with argon to 0.08-0.1 MPa, and release the furnace when the furnace temperature drops below 100 °C.

The RVB series brazing furnace produced by SIMUWU has the characteristics of good temperature uniformity and high temperature control accuracy, so it is widely purchased by overseas heat treatment factories. The parts are processed in a vacuum furnace produced by SIMUWU, and the joints are of good quality and increased durability.