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Vacuum Heat Treatment Furnace

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Application of Vacuum Heat Treatment Furnace in Aerospace Products

1. Vacuum Heat Treatment of Diaphragm

The metal diaphragm for engine end face sealing is made of high-temperature alloy GH169, with a thickness of δ=0.2mm. After welding, the parts are subjected to solution treatment and the first aging strengthening treatment, and then an overload test: press 2.5MPa, hold for 5 minutes, and the parts shall not be deformed or wrinkled. Then carry out the second strengthening treatment, and do repeated compression and pressure test more than 10 times.

The original solution treatment process is:

1065℃±10℃ for 0.5h for air cooling; after secondary strengthening aging, the room temperature strength σ≥226MPa (σb≥125kgf/mm2). Heating and air cooling in an ordinary electric furnace is bound to be severely oxidized. Therefore, we tried a vacuum heat treatment furnace for solution treatment and changed air cooling to furnace cooling to room temperature. The process is as follows:

Solution treatment: 1065±10℃, 0.5h furnace cooling to room temperature;

The first aging: 720℃, 4h, the furnace is cooled to room temperature;

The second aging: 620℃, 16h, the furnace is cooled to room temperature;

The parts are heated with the furnace, and the vacuum degree is not less than 1.33X10-3Pa.

After the above process, the parts are silver-white without deformation, and the strength and plasticity tests after the test have reached the material standard. The overload test, repeated compression, and pressure test of the parts are all qualified, thus realizing the vacuum heat treatment of the high-temperature alloy GH169 diaphragm.

GH169 contains 4.75~5.5% Nb, 0.65~1.15% Ti…These easily oxidizable elements are quickly oxidized in a vacuum quenching furnace with a vacuum of 1.33X10-1Pa (1X10-3 Torr). Oil can also cause discoloration of parts, so GH169 solid solution treatment surface oxidation in this type of furnace.

2. Vacuum Aging Strengthening of Elastic Alloy 3J₁

Many parts of the electro-hydraulic servo valve are made of 3J1, such as feedback lever, spring lever, nozzle, baffle, etc. Their dimensional accuracy is very high, and some tolerances are below 0.003mm. Some parts have a diameter of only 0.8mm, and there are many small holes and blind holes below φ 1mm, with complex shapes. The parts are finished after solution quenching of the rough material, and then aging strengthened. Because non-matching dimensions are no longer processed, it is required that there is no oxidation after heat treatment.

3J1 contains Ti and A1. It was processed in an externally heated vacuum tube in the past, and the surface was blue-black, which did not meet the technical requirements.

begging. After applying the vacuum heat treatment furnace, due to the high degree of vacuum, after the parts are processed, the metal after cutting remains very bright.

The process is as follows:

700℃, keep for 4 hours, the vacuum degree is not less than 1.33X10-2Pa (1X10-4 Torr). HRC38~45.

3. Vacuum Aging of Titanium Alloy

The spherical sauce press made of Tc4 has a wall thickness of 3 mm and requires a breaking pressure not less than 66MPa. Because the hole is spherical,

If it is oxidized, it will be difficult to clean up. Titanium alloys can easily absorb hydrogen, oxygen, and nitrogen, and form compounds at a certain temperature, reducing the performance of titanium alloys. The use of vacuum heat treatment not only obtains a very bright surface, but also purifies the material and gives full play to the characteristics of the material.

The aging process is: 550℃, 4h vacuum degree is not less than 1.33X 10-2

4. Vacuum Aging of Precipitation Hardening Stainless Steel

OCr17Ni4Cu4 Nb precipitation hardening stainless steel (PH17-4) has excellent corrosion resistance and mechanical properties, and is widely used in aerospace products, such as servo valve housings, actuators, etc. Due to the inclusion of Nb and Cu, the surface will be oxidized to blue after aging in an air furnace. In order to ensure the smoothness and non-oxidation of the parts, vacuum aging is used, and good results are obtained. The surface of the parts maintains the metal translation after cutting, and the aging temperature is from 480C to 580σ.

5. Vacuum Annealing of Constantan Foil

Constantan foil for control circuit, thickness δ=0.02mm, cold rolled material, must be annealed. Vacuum annealing is required, and the temperature is kept at 650°C for 1 hour. The users anneal in some vacuum furnaces successively, and the surface is slightly oxidized. Vacuum in our factory

After annealing in the furnace, the surface maintains the original bright silver-white color of the cold-rolled material, and the production has been stable for many years.

6. Vacuum Aging of Beryllium Bronze

Beryllium bronze is a widely used material, but in an air electric furnace at 320°C for 2 hours, the surface is oxidized and it is difficult to clean. The use of various types of grease protection can reduce oxidation, but the surface is still dark. After aging in a vacuum furnace, the parts maintain the original golden color, even brighter than the raw materials. For many years, our factory has been using vacuum aging to ensure the quality of the parts.

Although the internal heating type vacuum heat treatment furnace cannot perform vacuum quenching, it has a wide range of uses in other processes, such as brazing and sintering. This is mainly because of its furnace body structure, which has high vacuum and high thermal efficiency, and the structure is much simpler than quenching furnace. Suitable for heat treatment of parts with high surface quality requirements.