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Vacuum brazing process of honeycomb materials

Vacuum brazing is an advanced welding process, which is widely used in machinery, aviation, shipbuilding and other industries. During welding, the brazing material diffuses between the base metals and is distributed to the tight mating surface of the joint by the adsorption of capillary tubes. Workpiece connection. Since the honeycomb material is thin, the pores of the honeycomb are uniform and densely distributed, and it is easy to deform when heated, vacuum brazing is often used to weld the honeycomb material.

1 Test method

The test operation method is as follows:

(1) Cleaning: first clean the sample with gasoline-ultrasonic-cold water, and then use the newly prepared cleaning solution or acetone to strengthen the cleaning of the honeycomb until the oil on the surface of the sample and in the honeycomb is removed.

(2) Drying: The drying temperature is kept at (150±10)°C, and the holding time is 90~120 min.

(3) Filling with strip-shaped solder: Press the solder into the holes of the honeycomb surface to be welded by rolling to ensure that there is solder in each honeycomb hole.

(4) Assembly positioning spot welding: Spot weld the test piece and the honeycomb material with an energy storage spot welding machine as shown in Figure 1. The distance between each welding spot is not greater than 10mm, in order to prevent the welding spots from being welded due to too close Together, a piece of copper can be placed on the spot weld to isolate the spot, and powdered BNi82CrSiB solder can be added to D and E. The brazing process parameters are listed in the table below.

2 Test results and analysis

2.1 Visual inspection

Visual inspection results: the amount of deformation of the honeycomb core is not more than 20%; the surface of the honeycomb core has no obvious oxidation and macroscopic defects; the continuity of the brazing seam is greater than 98%, and the length of each discontinuous brazing seam is less than 5 mm. No defects such as dissolution and perforation were found in the samples from the four furnaces, and the grains were fine grains. Therefore, it can be determined that the solder BNi82CrSiB is suitable for the welding of GH4196 and GH3536.

2.2 Ultrasonic analysis

Ultrasonic flaw detection was carried out on the brazing seam of the first furnace sample, and there were obvious unpenetrated areas on No. 1 and No. 3 samples, and the area of the unpenetrated area of No. 3 sample was larger. This is due to the The energy is low, the binding force is small, and the honeycomb deforms when heated, so that the honeycomb material and the test piece are partially separated, and there is a non-tight fit between the honeycomb material and the test piece, and there is a hole in the non-tight fit of the solder, resulting in Welding is impenetrable. After adjusting the energy of energy storage spot welding to 500~550J and vacuum brazing temperature to 1055°C, the quality of the brazing seam meets the requirements.

3 applications

A factory produces an aviation precision part, which is welded by vacuum brazing of 0.3 mm thick GH3536 honeycomb material. Welding technical requirements: the number of core deformation is not more than 30%, there is no obvious oxidation and macroscopic defects on the surface of the honeycomb core, the continuity of the brazing seam is more than 98%, and the length of each discontinuous brazing seam is not more than 5 mm. The grain grade of welding place and welding heat-affected zone shall not be lower than grade 6. Production trial processing was carried out according to the process of energy storage spot welding energy 550J, brazing temperature 1055 ℃, holding time 14 minutes, and cooling with furnace. After passing the inspection and putting into mass production for a period of time, the pass rate of the product has reached more than 99%. The actual production shows that this process has short production cycle, low cost and high efficiency.

4 Conclusion

(1) Under the premise of ensuring the honeycomb deformation requirements, the energy of energy storage spot welding should be as large as possible, and the solder joints should be as dense as possible, so that the honeycomb and the test piece are closely matched.

(2) The brazing temperature should be 50-60°C higher than the liquidus line of the solder.

Vacuum furnace equipment selection: RHVB series vacuum brazing furnace produced by SIMUWU company is a high-quality product for vacuum heat treatment of tools and molds. Good temperature control accuracy and temperature control uniformity ensure the effective vacuum brazing process. SIMUWU company focuses on the manufacture of vacuum furnaces, has more than ten years of relevant experience, and has a good reputation in the field of vacuum furnace manufacturing. The product line includes vacuum air quenching furnace, vacuum oil quenching furnace, vacuum brazing furnace, etc., which are widely sold in developed and developing countries.