A heat treatment method for low-hardness sealing copper gasket

Abstract

The present application relates to a kind of low hardness sealed copper pad heat treatment method, to bar as processing base material, according to design size machine processing into copper pad, avoid the hardness change of copper pad after processing secondary hardening caused by heat treatment;After processing copper pad is pretreated, carries out first heat treatment;Heat treatment holding temperature is determined by copper pad raw material cold deformation rate, the higher the deformation rate, (restore recrystallization) holding temperature is higher, and the original size of the material of processing copper pad is smaller, and the higher holding temperature selected.The hardness of the present application can be controlled in 30HBW-40HBW, more in line with the design requirements of contact type mechanical seal form.

Description

Technical Field

[0001] This invention pertains to heat treatment processing methods, specifically a heat treatment method for a low-hardness sealing copper gasket, which reduces its hardness to the range of 30HBW to 40HBW after heat treatment. Background Technology

[0002] Copper gets its name from the purple oxide film on its surface and has a face-centered cubic structure. It has good thermal conductivity, electrical conductivity, weldability, ductility and corrosion resistance, and is widely used in industries such as electronics, aerospace and shipbuilding, machinery and equipment and molds.

[0003] Especially in the aerospace industry, the demand for copper gaskets is increasing, and contact-type mechanical seals are more adaptable to the complex operating conditions of aircraft. Their sealing relies primarily on the pairing of a high-hardness joint end face and a low-hardness copper gasket. Sealing performance depends mainly on the compression deformation of the copper gasket to fill the gaps at the end face. Excessive hardness of the copper gasket will result in insufficient deformation; insufficient hardness will cause material disintegration during deformation, damaging the copper gasket; neither of these will meet sealing requirements. Therefore, the hardness of the copper gasket directly affects the sealing performance, making the performance of copper seals an important research topic in this field.

[0004] Because different industries have different focuses, existing processes cannot meet the performance requirements under different conditions. Furthermore, the state of the raw materials (deformation) also affects the material properties after heat treatment, increasing the difficulty of process testing. In particular, there is no literature documenting the control of the low hardness (30HBW~40HBW) of annealed copper. To meet product design requirements, the hardness of the material after annealing must be within the safe operating range. Summary of the Invention

[0005] Technical problems to be solved

[0006] To overcome the shortcomings of existing technologies, this invention proposes a heat treatment method for low-hardness sealing copper gaskets, so that the hardness after heat treatment is in the range of 30HBW to 40HBW, solving the problem that the hardness of conventional heat-treated gaskets cannot meet the sealing requirements, and improving the pass rate of heat treatment of sealing copper gaskets.

[0007] Technical solution

[0008] A heat treatment method for low-hardness sealing copper gaskets, characterized by a supplementary heat treatment process involving secondary annealing and cold treatment, comprising the following steps:

[0009] Using bar stock as the base material, it is machined into copper pads according to the design dimensions to avoid changes in the hardness of the copper pads caused by secondary hardening after heat treatment.

[0010] After pretreatment of the processed copper pads, they are placed in a vacuum furnace and then evacuated to 1.33–13.3 Pa.

[0011] First heat treatment: Heat to 420℃~480℃ and hold for 20min~30min;

[0012] The insulation temperature is determined by the cold deformation rate of the copper pad material. The higher the deformation rate, the higher the insulation temperature (recovery recrystallization). Also, the smaller the original size of the material used to process the copper pad, the higher the insulation temperature can be selected.

[0013] Then slowly heat to 630℃~680℃, do not hold the temperature, turn off the power and cool in the furnace to below 100℃ before air cooling.

[0014] When the initial hardness test meets the target hardness, the heat treatment of the sealing copper gasket is completed.

[0015] A second heat treatment is performed if the initial hardness does not meet the target hardness.

[0016] When the initial hardness is lower than the target hardness (0-5), cold treatment is performed at -70℃ to -90℃ for 150-180 minutes, followed by air cooling.

[0017] If the initial hardness is higher than the target hardness (0-8), repeat the first heat treatment and adjust the process parameters to the upper limit for two heat treatments: heat to 480℃ and hold for 30 minutes; then heat to 680℃ at 1.2℃ / min, do not hold, turn off the power and cool in the furnace to below 100℃ before air cooling.

[0018] The slow heating rate is 0.8℃ / min to 1.2℃ / min.

[0019] The machining process is performed by turning.

[0020] The pretreatment involves cleaning the sealing copper gasket with ethyl acetate.

[0021] After the copper pads pass inspection, they are individually packaged with rust-proof paper, placed in a packaging box, and filled with 99.99% nitrogen.

[0022] The heat treatment temperature is directly proportional to the cold deformation rate of the copper pad material.

[0023] The holding temperature of the first heat treatment is inversely proportional to the original dimensions of the material used to process the copper pad.

[0024] Beneficial effects

[0025] This invention proposes a heat treatment method for low-hardness sealing copper gaskets. Using rods as the base material, the copper gaskets are machined to design dimensions, avoiding changes in hardness caused by secondary hardening after heat treatment. After pretreatment, the machined copper gaskets undergo a first heat treatment. The holding temperature during heat treatment is determined by the cold deformation rate of the copper gasket material; a higher deformation rate (recovery recrystallization) requires a higher holding temperature, and a smaller original size of the material used to machine the copper gasket necessitates a higher holding temperature. If the target hardness is not met, a first cold treatment or a second heat treatment is performed.

[0026] Compared with the prior art, the advantages of this invention are:

[0027] (1) Conventional heat treatment of sealing copper gaskets cannot precisely control the hardness range after treatment, and can only meet the requirement of being below a certain hardness value. The present invention can control the hardness within 30HBW to 40HBW, which is more in line with the design requirements of contact mechanical seals.

[0028] (2) Conventional heat treatment of sealing copper gaskets results in a single heat treatment process where the hardness of the copper gasket cannot be adjusted, and any defective product must be scrapped. This invention employs a supplementary heat treatment technology of secondary annealing and cold treatment, which enables fine adjustment of the copper gasket hardness and improves the product qualification rate.

[0029] (3) Conventional heat treatment of sealing copper gaskets does not consider the cold deformation rate of raw materials. It uses high temperatures and long holding times to soften the copper gaskets. During the recrystallization nucleation stage, the temperature is often rising, which is not conducive to obtaining copper gaskets with lower hardness. Long-term holding in high-temperature areas (above 600℃) does not effectively promote the continuous softening of materials when the number of nuclei is already determined, resulting in ineffective energy consumption. This invention considers the cold deformation rate of raw materials. It holds the material at the recovery crystallization temperature range to promote nucleation, and then slowly heats it (0.8℃ / min~1.2℃ / min) to ensure continuous energy supply for the growth of nuclei in the previous stage and ensure that the material is fully softened. After reaching the heating peak, the temperature is directly lowered to reduce ineffective energy consumption and shorten the processing time.

[0030] (4) Unlike conventional heat treatment of sealing copper gaskets, the process involves machining followed by vacuum heat treatment to reduce the heat treatment stress and deformation of the copper gasket, and to avoid the hardening effect caused by heat treatment followed by machining. The post-treatment uses rust-proof paper for individual packaging and is placed in a packaging box filled with 99.99% nitrogen to prevent the copper gasket from developing oxidation black spots. Attached Figure Description

[0031] Figure 1 The vacuum heat treatment process curve of the present invention Detailed Implementation

[0032] The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

[0033] Example 1: Φ60 copper T2-M rods were processed and shaped to Φ50×Φ40×2.5 mm, with a hardness requirement of 30HBW~40HBW. Pretreatment was performed, including cleaning the sealing copper gasket with ethyl acetate. The pretreated material was then placed in a vacuum furnace and evacuated to 13.3 Pa. In the first stage, the temperature was raised to 420℃ and held for 20 min. Then, the temperature was slowly increased to 630℃ at a rate of 0.8℃ / min, without holding. The furnace was then cooled to below 100℃ before being removed and air-cooled. Measurement and testing results showed a hardness of 37HBW~38HBW.

[0034] After passing inspection, the rust-proof paper is packaged separately, placed in a box, and filled with 99.99% nitrogen.

[0035] Example 2: Φ40 copper T2-Y rods were processed and shaped into Φ30×Φ14×2 bars with a hardness requirement of 30HBW~40HBW. Pretreatment was performed, including cleaning the sealing copper gasket with ethyl acetate. The pretreated material was then placed in a vacuum furnace and evacuated to 13.3 Pa. In the first stage, the temperature was raised to 440℃ and held for 20 minutes. Then, the temperature was slowly increased to 650℃ at a rate of 1.0℃ / min, without holding. The furnace was then turned off and the material was cooled to below 100℃ before being air-cooled.

[0036] The initial metrological test results were 38 HBW to 42 HBW. The process parameters were adjusted to the upper limit, and two heat treatments were performed. The temperature was raised to 460℃ and held for 25 minutes. Then, it was slowly heated to 670℃ at a rate of 0.8℃ / min, without holding, and then cooled in the furnace to below 100℃ before being air-cooled. The metrological test results were 32 HBW to 36 HBW.

[0037] After passing inspection, the rust-proof paper is packaged separately, placed in a box, and filled with 99.99% nitrogen.

[0038] Example 3: Φ25 copper T2-M rods were processed and shaped into Φ20×Φ8×2 bars with a hardness requirement of 30HBW~40HBW. Pretreatment was performed, including cleaning the sealing copper gasket with ethyl acetate. The pretreated material was then placed in a vacuum furnace and evacuated to 1.33 Pa. In the first stage, the temperature was raised to 440℃ and held for 25 minutes. Then, the temperature was slowly increased to 630℃ at a rate of 1.1℃ / min, without holding. The furnace was then turned off and the material was cooled to below 100℃ before being air-cooled.

[0039] The initial metrological test results were 28 HBW to 31 HBW. The heat-treated copper pad was then subjected to cold treatment at -90℃ for 160 minutes, followed by air cooling. The final metrological test results were 33 HBW to 35 HBW.

[0040] After passing inspection, the rust-proof paper is packaged separately, placed in a box, and filled with 99.99% nitrogen.

Claims

1. A heat treatment method for a low-hardness sealing copper gasket, characterized in that... The supplementary heat treatment process, which involves secondary annealing and cold treatment, has the following steps: Using bar stock as the base material, it is machined into copper pads according to the design dimensions to avoid changes in the hardness of the copper pads caused by secondary hardening after heat treatment. After pretreatment, the processed copper pads are placed in a vacuum furnace and then evacuated to a pressure of 1.33–13.3 Pa. First heat treatment: Heat to 420℃~480℃ and hold for 20min~30min; Then slowly heat to 630℃~680℃, do not hold the temperature, turn off the power and cool in the furnace to below 100℃ before air cooling. When the initial hardness test meets the target hardness, the heat treatment of the sealing copper gasket is completed. If the initial hardness test does not meet the target hardness, a second heat treatment is performed: When the initial hardness is 0-5 lower than the target hardness, cold treatment is performed at -70℃ to -90℃ for 150-180 minutes, followed by air cooling. If the initial hardness is 0-8 higher than the target hardness, repeat the first heat treatment and adjust the process parameters to the upper limit for two heat treatments: heat to 480℃ and hold for 30 minutes; then heat to 680℃ at 1.2℃ / min, do not hold, and cool to below 100℃ in the furnace before air cooling; the slow heating rate is 0.8℃ / min to 1.2℃ / min; the machining is done by turning. The pretreatment involves cleaning the sealing copper gasket with ethyl acetate. After the copper pads pass inspection, they are individually packaged with rust-proof paper, placed in a packaging box, and filled with 99.99% nitrogen. The heat treatment temperature is directly proportional to the cold deformation rate of the copper pad material. The holding temperature of the first heat treatment is inversely proportional to the original dimensions of the material used to process the copper pad.

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