A preparation method of kovar alloy foil

Abstract

The present invention belongs to the technical field of the preparation of Kovar alloy foils, aiming to solve the problems in the prior art that it is difficult to control the content of trace elements in the preparation process of Kovar alloy foils and it is difficult to further reduce the harmful trace elements. For this purpose, the present invention provides a method for preparing Kovar alloy foils, which includes: placing Kovar alloy raw materials in a melting furnace for melting, pouring the melted metal liquid into a target mold to form an ingot; heating the ingot and forging it into a billet; cooling the forged billet and then cleaning its surface; performing dehydrogenation treatment on the billet after surface cleaning; and subjecting the alloy after dehydrogenation treatment to one-time hot rolling treatment and multiple cold rolling treatments to obtain Kovar alloy foils with a target thickness. The present invention enables precise control of the content of trace elements during the preparation of Kovar alloy foils, reduces the content of harmful trace elements such as sulfur, avoids the problem of hydrogen embrittlement in Kovar alloy, and improves the ductility and toughness of Kovar alloy.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of Kovar alloy foils, and particularly to a method for preparing Kovar alloy foils. Background Art

[0002] Kovar alloy, as a special alloy material with excellent properties, is widely used in the fields of electronics, aviation, aerospace, and precision instruments. Especially in occasions where high stability and low expansion coefficient are required, its importance is particularly prominent. With the progress of technology and the in-depth application, higher requirements are put forward for the properties and preparation processes of Kovar alloy foils, especially in terms of the thickness uniformity, composition purity, and microstructure of the foils.

[0003] The existing methods for preparing Kovar alloy foils often face many challenges, such as inaccurate composition control, poor tissue uniformity caused by simple ingot casting and forging processes, easy generation of internal stress and impurity residues during sintering, etc. These directly affect the performance and service life of the final product. Especially in terms of the content control of trace elements during the preparation process, it is crucial for improving the overall performance of the alloy. However, in the preparation process of Kovar alloy, it is unrealistic to completely eliminate some harmful trace elements. Taking sulfur (S) as an example, too high sulfur content will cause a significant decline in the corrosion resistance and mechanical properties of the alloy. Moreover, according to research, even a very small amount of S in Kovar alloy may cause hydrogen embrittlement problems in Kovar alloy. This is because the presence of S promotes the hydrogen absorption ability of the metal, enabling more hydrogen atoms to enter the metal interior. And since S reduces the ductility and toughness of the metal, the material is more likely to fracture when affected by hydrogen embrittlement. At the same time, S may also promote the diffusion and aggregation process of hydrogen atoms in the metal interior, thus exacerbating the occurrence of hydrogen embrittlement phenomenon. Therefore, how to control the content of trace elements during the preparation process of Kovar alloy and how to further reduce harmful trace elements is a difficult problem faced by this field.

[0004] In view of this, the field needs a new method for preparing Kovar alloy foils to solve the above problems. Summary of the Invention

[0005] In order to solve the above technical problems, that is, to solve the problems of difficult content control of trace elements and difficult further reduction of harmful trace elements in the existing preparation process of Kovar alloy foils, the present invention provides a method for preparing Kovar alloy foils, aiming to accurately control the content of trace elements in the preparation process of Kovar alloy foils, and to be able to further reduce the content of harmful trace elements such as sulfur, avoid hydrogen embrittlement problems in Kovar alloy, and improve the ductility and toughness of Kovar alloy.

[0006] A preparation method of kovar alloy foil provided by the present invention, the preparation method comprising:

[0007] S1: Place the kovar alloy raw materials in a melting furnace for melting, and pour the melted metal liquid into a target mold to form an ingot. Among them, the mass percentage of trace element S component in the kovar alloy raw materials is controlled as: S≤0.01%;

[0008] S2: Heat the ingot prepared in step S1 and then forge it into a billet;

[0009] S3: Cool the billet forged in step S2 and then perform surface cleaning;

[0010] S4: Perform dehydrogenation treatment on the billet after surface cleaning in step S3;

[0011] S5: Subject the alloy after dehydrogenation treatment in step S4 to one-time hot rolling treatment and multiple cold rolling treatments to obtain a kovar alloy foil with a target thickness.

[0012] In some preferred embodiments, the components of the kovar alloy raw materials include, by mass percentage: C≤0.015%, P≤0.01%, S≤0.01%, Mn: 0.35 - 0.45%, Si≤0.20%, Cu≤0.10%, Cr≤0.10%, Mo≤0.10%, Ni: 28.8% - 29.2%, Co: 17.0 - 17.3%, Zr: 0.1 - 0.2%, Nb: 0.05 - 0.15%, and the balance is Fe.

[0013] In some preferred embodiments, the melting temperature is 1600 - 1700°C, and melting is carried out under an argon protection atmosphere; before pouring, first keep the metal liquid in an environment with a vacuum degree of 10 - 50 Pa for 10 - 15 minutes for preliminary vacuum treatment, then introduce argon into the metal liquid for blowing and stirring, the argon flow rate is controlled at 5 - 10 L / min, and the stirring time is 5 - 8 minutes; the pouring temperature is 1550 - 1600°C, and the pouring speed is 2 - 5 kg / s; during the pouring process, heat preservation treatment is carried out on the target mold.

[0014] In some preferred embodiments, step S2 specifically includes:

[0015] Heat the ingot prepared in step S1. First, heat the ingot at a heating rate of 60 - 80°C / h to 550 - 600°C for preheating, and the heat preservation time is 2 - 3 hours. Then, heat it at a rate of 100 - 120°C / h to the forging temperature range of 1150 - 1200°C. During the heating process, control the oxygen content in the furnace below 0.05% through the furnace gas circulation device;

[0016] Adopt a forging method with multiple passes and small deformation amounts to gradually forge the ingot into the required blank shape, and control the deformation amount of each pass between 12% and 18%.

[0017] In some preferred embodiments, step S3 specifically includes:

[0018] Place the blank in a holding furnace and slowly cool it with the furnace, and the cooling rate is 60 - 80 °C / h;

[0019] Use mechanical grinding to grind the blank, the grinding pressure is 0.2 - 0.4 MPa, and the grinding speed is 10 - 15 m / min;

[0020] Put the blank into a chemical cleaning tank and clean it with a cleaning solution. The cleaning time is 15 - 25 minutes, and the cleaning solution is stirred at a stirring speed of 30 - 50 r / min during the cleaning process;

[0021] After cleaning, rinse the blank with clean water, the rinsing pressure is 0.1 - 0.3 MPa, and the rinsing time is 3 - 5 minutes.

[0022] In some preferred embodiments, step S4 specifically includes:

[0023] Place the blank after surface cleaning in step S3 into a dehydrogenation furnace and fill the dehydrogenation furnace with argon;

[0024] Heat and dehydrogenate the alloy in the dehydrogenation furnace, the dehydrogenation temperature is 1430 - 1480 °C, and the dehydrogenation time is 2.5 - 3.5 hours;

[0025] After dehydrogenation is completed, turn off the power supply of the dehydrogenation furnace and let the alloy cool naturally in the dehydrogenation furnace to room temperature.

[0026] In some preferred embodiments, step S4 further includes:

[0027] Use a grinding machine to grind the alloy after dehydrogenation treatment, and among them, the grinding direction remains unchanged all the time;

[0028] Use a polishing machine to polish the alloy after grinding treatment.

[0029] In some preferred embodiments, step S5 specifically includes:

[0030] Perform hot rolling treatment on the alloy after dehydrogenation treatment in step S4. The hot rolling treatment temperature is 410 - 430 °C, and the hot rolling time is 70 - 80 minutes;

[0031] Subject the hot-rolled alloy to multiple cold rolling, cleaning and annealing steps. Among them, the annealing temperature after the first cold rolling is 470 - 480 °C, the annealing time is 65 - 75 minutes, and the cleaning is carried out with dilute hydrochloric acid.

[0032] In some preferred embodiments, the hot-rolled alloy is subjected to three cold rolling, cleaning and annealing steps, specifically:

[0033] The hot-rolled alloy is fed into a rolling mill for the first rolling. After the rolled alloy is cleaned with dilute hydrochloric acid, it is subjected to the first annealing.

[0034] The alloy after the first annealing is fed into a rolling mill for the second rolling. After the rolled alloy is cleaned with dilute hydrochloric acid, it is subjected to the second annealing, wherein the annealing temperature is 780 - 790 °C and the annealing time is 60 - 70 minutes.

[0035] The alloy after the second annealing is fed into a rolling mill for the third rolling. After the rolled alloy is cleaned with dilute hydrochloric acid, it is subjected to the third annealing to obtain the Kovar alloy foil with the target thickness, wherein the annealing temperature is 530 - 540 °C and the annealing time is 60 - 70 minutes.

[0036] In some preferred embodiments, step S5 further includes:

[0037] The Kovar alloy foil after the third annealing is cleaned with an ultrasonic cleaner for 10 - 15 minutes, and then polished.

[0038] The present invention has the following beneficial effects:

[0039] The method for preparing the Kovar alloy foil provided by the present invention strictly controls the mass percentage of trace element S in the Kovar alloy raw material (S ≤ 0.01%), reducing the factors that may cause hydrogen embrittlement from the source. During the preparation process, a dehydrogenation treatment process is added to further remove the hydrogen that may exist in the alloy. After the dehydrogenation treatment, the hydrogen content in the alloy is significantly reduced, improving the toughness and ductility of the foil, making it more resistant to external forces during use and not easily prone to hydrogen embrittlement fracture, significantly extending the service life of the Kovar alloy foil. After the ingot casting, forging treatment is carried out to fully refine and homogenize the structure of the alloy. The subsequent hot rolling and multiple cold rolling treatments further improve the structural uniformity. The present invention does not require particularly high-precision melting equipment and complex powder processing equipment. Ordinary melting furnaces and forging equipment can meet the production requirements after appropriate parameter adjustment and maintenance, which greatly reduces the equipment cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The features and advantages of the present invention will be more clearly understood by referring to the accompanying drawings. The drawings are schematic and should not be construed as limiting the present invention in any way. In the drawings:

[0041] Figure 1 is a flow chart of the method for preparing the Kovar alloy foil of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0043] Based on the problems in the prior art pointed out in the background art, namely, the difficulty in controlling the content of trace elements in the preparation process of Kovar alloy foil and the difficulty in further reducing harmful trace elements, the present invention provides a method for preparing Kovar alloy foil, aiming to accurately control the content of trace elements in the preparation process of Kovar alloy foil, and further reduce the content of harmful trace elements such as sulfur, avoid the problem of hydrogen embrittlement in Kovar alloy, and improve the ductility and toughness of Kovar alloy.

[0044] As Figure 1 shown, the method for preparing Kovar alloy foil provided by the present invention includes:

[0045] S1: Place the Kovar alloy raw material in a melting furnace for melting, and pour the melted metal liquid into a target mold to form an ingot. Among them, the mass percentage of the trace element S component in the Kovar alloy raw material is controlled as: S ≤ 0.01%, preferably, the other components are as follows: C ≤ 0.015%, P ≤ 0.01%, Mn: 0.35 - 0.45%, Si ≤ 0.20%, Cu ≤ 0.10%, Cr ≤ 0.10%, Mo ≤ 0.10%, Ni: 28.8% - 29.2%, Co: 17.0 - 17.3%, Zr: 0.1 - 0.2%, Nb: 0.05 - 0.15%, and the balance is Fe;

[0046] In the above, the manganese (Mn) content is controlled between 0.35 - 0.45%, thereby playing the role of deoxidation and desulfurization. It can combine with sulfur to form manganese sulfide with a high melting point, reducing the harmful effects of sulfur, and improving the strength and hardness of the alloy without affecting the toughness of the alloy; the chromium (Cr) content is controlled to be ≤0.10%. Chromium can improve the corrosion resistance and oxidation resistance of the Kovar alloy. At high temperatures, chromium can form a stable chromium oxide film to prevent further oxidation of the alloy; the molybdenum (Mo) content is controlled to be ≤0.10%. Molybdenum can improve the strength and high-temperature performance of the Kovar alloy. It can dissolve in the alloy matrix, enhancing the interatomic binding force of the alloy, thereby improving the strength and hardness of the alloy. At the same time, molybdenum can also increase the recrystallization temperature of the alloy, enabling it to maintain good mechanical properties at high temperatures; the zirconium (Zr) content is controlled between 0.1 - 0.2%. Zirconium mainly plays the role of refining grains in the Kovar alloy. It can inhibit the grain growth of the alloy during solidification, making the structure of the alloy more uniform and dense, thereby improving the strength and toughness of the alloy. At the same time, zirconium can also improve the corrosion resistance of the alloy; the niobium (Nb) content is controlled between 0.05 - 0.15%. Niobium can improve the strength and corrosion resistance of the Kovar alloy. It can form stable compounds with elements such as carbon and nitrogen, reducing the adverse effects of these elements on the alloy properties. At the same time, niobium can also refine grains, improving the toughness and workability of the alloy.

[0047] In addition, the inventors found that nickel (Ni) and cobalt (Co) with the above contents can jointly form a stable austenite structure, endowing the alloy with good toughness and plasticity at room temperature. Nickel expands the austenite phase region, and cobalt improves the thermal stability and strength of the alloy. The two cooperate with each other to enhance the comprehensive mechanical properties of the alloy. In a high-temperature environment, this synergistic effect is more obvious, enabling the alloy to maintain good strength and hardness, and not easily undergoing deformation and softening; for manganese (Mn) and sulfur (S) with the above contents, when the sulfur content is controlled at a low level (≤0.01%), manganese can combine with sulfur to form manganese sulfide with a high melting point, reducing the harmful effects of sulfur and preventing the occurrence of hot brittleness. This synergistic effect helps to improve the mechanical properties and workability of the alloy, reducing defects caused by sulfur; zirconium (Zr) and niobium (Nb) can promote each other in terms of grain refinement. Zirconium can inhibit the grain growth during solidification in the alloy, making the structure more uniform and dense, improving the strength and toughness of the alloy. Niobium, on the other hand, forms stable compounds with elements such as carbon and nitrogen, reducing the adverse effects of these elements on the alloy properties, and can also refine grains. The two work together to further enhance the mechanical properties and workability of the alloy. During the subsequent forging and rolling processes of the Kovar alloy, the refined grains can make the alloy easier to deform, improving the dimensional accuracy and surface quality. At the same time, the uniform and dense structure can also improve the corrosion resistance of the alloy and extend its service life.

[0048] Preferably, in the above step S1, the melting temperature is 1600 - 1700 °C, and the melting is carried out under an argon protection atmosphere to prevent the alloy from oxidation and gas absorption, providing high-quality molten metal for subsequent processes; the mold is made of H13 steel, and the inner surface of the mold is finely polished to make the surface roughness Ra between 0.8 - 1.6 μm to ensure the smooth surface of the ingot and reduce stress concentration points during subsequent processing; a layer of high-temperature release agent, such as boron nitride coating, is applied to the inner wall of the mold, and the coating thickness is controlled between 0.05 - 0.1 mm, which can not only facilitate the demolding of the ingot but also reduce the adhesion between the ingot and the mold, reducing the possibility of surface defects; the molten metal after melting is fully degassed, and methods such as blowing and stirring or vacuum treatment can be used. For example, the molten metal is first subjected to preliminary vacuum treatment in an environment with a vacuum degree of 10 - 50 Pa for 10 - 15 minutes, and then argon is introduced into the molten metal for blowing and stirring, with the argon flow rate controlled at 5 - 10 L / min and the stirring time being 5 - 8 minutes to minimize the hydrogen content in the molten metal and prevent the occurrence of hydrogen embrittlement; the pouring temperature is controlled within a suitable range, generally slightly higher than the liquidus temperature of the alloy. For Kovar alloy, the pouring temperature is controlled between 1550 - 1600 °C to ensure that the molten metal has good fluidity but is not too high to cause increased gas absorption and oxidation. During pouring, the molten metal is made to flow smoothly into the mold, and the bottom-pouring method is adopted, with the pouring speed controlled at 2 - 5 kg / s to avoid splashing and turbulence and prevent the entrainment of air and impurities; during the pouring process, heat preservation measures are taken for the mold, such as wrapping the outside of the mold with heat preservation materials (such as aluminosilicate fiber), and the thickness of the heat preservation layer is controlled between 30 - 50 mm to slow down the cooling rate of the ingot, making the internal structure of the ingot more uniform and reducing internal stress caused by uneven cooling;

[0049] S2: Heat the ingot prepared in step S1 and forge it into a billet;

[0050] Preferably, the above step S2 specifically includes:

[0051] Heat the ingot prepared in step S1. First, heat the ingot at a heating rate of 60 - 80 °C / h to 550 - 600 °C for preheating, with a holding time of 2 - 3 hours. Then, raise the temperature to the forging temperature range at a rate of 100 - 120 °C / h, and control the forging heating temperature between 1150 - 1200 °C; during the heating process, ensure the uniformity of the furnace atmosphere, and control the oxygen content in the furnace below 0.05% through the furnace gas circulation device to prevent local oxidation or decarburization of the ingot; adopt a forging method with multiple passes and small deformation amounts to gradually forge the ingot into the required blank shape; control the deformation amount of each pass between 12% - 18%. For example, first perform rough forging to roughly forge the shape of the ingot close to the blank shape, with 3 - 5 rough forging passes, and then perform multiple finish forging passes, with 5 - 8 finish forging passes, to gradually refine the microstructure and improve the dimensional accuracy; during the forging process, control the forging direction and deformation sequence to ensure that the blank can be fully deformed in different directions; for example, first perform axial forging, and then perform radial forging, and control the reduction amount of each forging between 10 - 20 mm to ensure good forging effect on all parts of the blank; control the impact force and frequency of the forging equipment. For large-volume blanks, use a hydraulic press for forging, and control the hydraulic press pressure between 100 - 150 MPa; for small-volume blanks, use a mechanical hammer for forging, control the impact force of the mechanical hammer between 500 - 800 kN, and control the impact frequency between 30 - 50 times / min to avoid internal cracks in the blank caused by excessive impact force, and at the same time, an appropriate frequency can ensure the smooth progress of the forging process;

[0052] S3: After cooling the blank forged in step S2, perform surface cleaning;

[0053] Preferably, step S3 specifically includes:

[0054] After forging, the billet is cooled, preferably by slow cooling. For example, the billet is placed in a holding furnace and slowly cooled with the furnace, and the cooling rate is controlled at about 60 - 80 °C / h. Or the billet is wrapped with heat-insulating materials such as asbestos for cooling, and the thickness of the heat-insulating material is controlled between 20 - 30 mm to reduce the cooling rate and reduce the residual stress and non-uniformity of the structure caused by too fast cooling. The surface is cleaned by a method combining mechanical grinding and chemical cleaning. First, tools such as a grinding wheel or a wire brush are used to initially grind and remove the scale on the surface of the billet, and the grinding pressure is controlled between 0.2 - 0.4 MPa, and the grinding speed is 10 - 15 m / min. Then the billet is put into a chemical cleaning tank for cleaning. The cleaning solution is a solution containing an appropriate amount of acid and corrosion inhibitor, such as dilute hydrochloric acid (concentration 8% - 10%) or sulfuric acid solution (concentration 6% - 8%), and the addition amount of the corrosion inhibitor is 0.8% - 1% of the mass of the acid solution. The cleaning time is determined according to the thickness and pollution degree of the scale on the surface of the billet, generally 15 - 25 minutes. During the cleaning process, the cleaning solution should be continuously stirred at a speed of 30 - 50 r / min to ensure uniform cleaning and prevent excessive corrosion of the billet surface. After cleaning, the billet is rinsed with clean water, the rinsing pressure is 0.1 - 0.3 MPa, and the rinsing time is 3 - 5 minutes to remove the residual cleaning solution and impurities on the surface, and then drying treatment is carried out. The drying temperature is 90 - 110 °C and the time is 1.5 - 2 hours to ensure that the surface of the billet is dry and clean, and to prepare for subsequent flaw detection and processing procedures. A variety of flaw detection methods are used to comprehensively detect the cleaned billet to ensure the internal quality of the billet. For example, first, an ultrasonic flaw detector is used to detect the billet to check whether there are defects such as cracks and porosity inside the billet. The frequency of ultrasonic flaw detection is selected according to the size and material of the billet, generally between 2.5 - 4 MHz. For large-volume billets, multi-probe and multi-angle flaw detection are adopted, and the probe spacing is controlled between 50 - 80 mm to ensure comprehensive detection coverage. Then magnetic particle flaw detection is carried out to detect small defects on the surface and near the surface of the billet. After magnetizing the billet, a magnetic particle suspension is evenly sprayed on its surface, the magnetic particle concentration is 10 - 20 g / L, and the aggregation of magnetic particles is observed to judge whether there are defects. During magnetic particle flaw detection, the magnetization current and magnetic field strength are controlled within a suitable range, the magnetization current is 500 - 800 A, and the magnetic field strength is 2000 - 3000 Gs to ensure the detection sensitivity. The defects found by flaw detection are analyzed and evaluated. If they are small surface defects with a defect size less than 2 mm, methods such as grinding and repair welding are used for repair. If they are large internal defects with a defect size greater than 5 mm or a defect depth exceeding 10% of the billet thickness, it is necessary to decide whether to scrap the billet according to the severity and location of the defects. The repaired part needs to be flaw detected again to ensure that the quality meets the requirements;

[0055] S4: The billet after surface cleaning in step S3 is subjected to dehydrogenation treatment;

[0056] Preferably, step S4 specifically includes:

[0057] Place the billet after surface cleaning in step S3 in a dehydrogenation furnace, and fill the dehydrogenation furnace with argon; heat and dehydrogenate the alloy in the dehydrogenation furnace, with the dehydrogenation temperature being 1430 - 1480 °C and the dehydrogenation time being 2.5 - 3.5 hours; after dehydrogenation is completed, turn off the power of the dehydrogenation furnace and let the alloy cool naturally in the dehydrogenation furnace to room temperature; use a grinding machine to grind the alloy after dehydrogenation treatment, where the grinding direction remains unchanged all the time; use a polishing machine to polish the alloy after grinding treatment;

[0058] S5: Subject the alloy after dehydrogenation treatment in step S4 to one hot rolling treatment and multiple cold rolling treatments to obtain a Kovar alloy foil with a target thickness;

[0059] Preferably, step S5 specifically includes:

[0060] Subject the alloy after dehydrogenation treatment in step S4 to hot rolling treatment, with the hot rolling treatment temperature being 410 - 430 °C and the hot rolling time being 70 - 80 minutes. Through hot rolling, the billet is further deformed to improve the tissue performance and prepare for the subsequent cold rolling process; subject the hot-rolled alloy to multiple cold rolling, cleaning, and annealing steps. Among them, the annealing temperature after the first cold rolling is 470 - 480 °C and the annealing time is 65 - 75 minutes, and the cleaning is carried out using dilute hydrochloric acid. It should be particularly noted that the texture in the alloy after hot rolling transforms into a weaker random and diffuse texture. After setting the annealing parameters of the first rolling and annealing temperature of 470 - 480 °C and annealing time of 65 - 75 minutes, compared with the too high annealing temperature range (resulting in too large grain size, reducing the strength and hardness of the material) and too low annealing temperature range (resulting in incomplete crystallization, the existence of dislocations and substructures, reducing plasticity, toughness, and increasing crack propagation) in the prior art, the plastic anisotropy of the final rolling sample obtained in the present invention is improved most significantly, and the plastic anisotropy index can be reduced to 11.9% at most. The texture is mainly a specific cubic texture variant with a crystal plane index of 100 and a crystal direction index of 110, achieving the best in terms of comprehensive mechanical properties and anisotropy, significantly reducing plastic anisotropy while ensuring the strength of the material;

[0061] Specifically, the hot-rolled alloy undergoes three cold rolling, cleaning, and annealing steps, specifically as follows: The hot-rolled alloy is fed into a rolling mill for the first rolling. After the rolled alloy is cleaned with dilute hydrochloric acid, it undergoes the first annealing. The alloy after the first annealing is fed into the rolling mill for the second rolling. After the rolled alloy is cleaned with dilute hydrochloric acid, it undergoes the second annealing, where the annealing temperature is 780 - 790 °C and the annealing time is 60 - 70 minutes. The alloy after the second annealing is fed into the rolling mill for the third rolling. After the rolled alloy is cleaned with dilute hydrochloric acid, it undergoes the third annealing to obtain the Kovar alloy foil with the target thickness, where the annealing temperature is 530 - 540 °C and the annealing time is 60 - 70 minutes. The Kovar alloy foil after the third annealing is cleaned with an ultrasonic cleaner for 10 - 15 minutes and then polished.

[0062] It should be noted that through repeated experiments, analysis and comparison by the inventors, it is found that S has a certain surface activity in the alloy. When the S content is relatively high (exceeding 0.01%), it will be highly enriched on the surface of the alloy liquid; during the melting and pouring processes, the alloy liquid contacts the surrounding atmosphere, and the presence of S will change the physical and chemical properties of the alloy liquid surface, making it easier for hydrogen to adsorb on the alloy liquid surface; this may be because S atoms will form some weak chemical bonds or physical adsorption with hydrogen molecules, increasing the probability of hydrogen dissolution and adsorption in the alloy liquid; in contrast, when the S content is controlled below 0.01%, its enrichment degree on the alloy liquid surface is significantly reduced, and the hydrogen adsorption capacity of the alloy liquid surface is weakened, thereby reducing the amount of hydrogen entering the alloy liquid; in addition, when the S content is relatively high, it will affect the structure and properties of the alloy surface oxide film; during the high-temperature melting process, the alloy will react with oxygen in the air to form an oxide film; the oxide film with a higher S content may have more defects and pores, and these defects provide a penetration channel for hydrogen; hydrogen can more easily diffuse into the alloy interior through these channels, resulting in an increase in the hydrogen content in the alloy; while when the S content is controlled at a lower level (below 0.01%), the formed oxide film is denser and more uniform, which can effectively block the penetration of hydrogen, reducing the possibility of hydrogen entering the alloy interior, and thus contributing to controlling the hydrogen content of the alloy; in addition, during the subsequent degassing process of the alloy liquid, such as vacuum treatment and gas blowing and stirring, the presence of S will have an adverse effect on the degassing effect. For example, during vacuum treatment, S will form compounds with lower volatility with other elements or impurities in the alloy, and these compounds are not easily volatilized and discharged in a vacuum environment, thus affecting the hydrogen removal efficiency; during gas blowing and stirring, S will chemically react with argon, consuming part of the argon, and at the same time the generated products may wrap around the hydrogen bubbles, preventing the hydrogen bubbles from floating up and discharging, resulting in poor degassing effect and ultimately a higher hydrogen content in the alloy; when the S content in the raw materials is controlled below 0.01%, the interference factors during the degassing process are reduced; vacuum treatment can more effectively remove hydrogen from the alloy liquid because there are not too many S-related compounds hindering the volatilization of hydrogen; during gas blowing and stirring, argon can more smoothly contact the alloy liquid, bringing out the hydrogen dissolved in the alloy liquid, improving the degassing efficiency, and enabling better control of the hydrogen content in the alloy; during subsequent processing such as forging and rolling, the atoms inside the alloy will move and rearrange; when the S content in the raw materials is relatively high, the alloy is more likely to generate stress concentration and micro-defects during processing; these defect sites will become the aggregation points of hydrogen, promoting the diffusion and aggregation of hydrogen; the aggregation of hydrogen at the defects may lead to problems such as hydrogen embrittlement, further affecting the performance of the alloy; while when the S content is controlled at 0.When it is below 0.01%, the structure of the alloy is more uniform during the processing, the defects are reduced, and the diffusion path of hydrogen is also correspondingly reduced; this makes the distribution of hydrogen in the alloy more uniform, reduces the adverse effects caused by hydrogen aggregation, and thus is conducive to maintaining a low hydrogen content and good alloy properties; during the dehydrogenation treatment process, the S content will also affect the dehydrogenation effect; when the S content exceeds 0.01%, it will react with the gas generated during the dehydrogenation process or other elements in the alloy to form some stable compounds, and these compounds may inhibit the removal of hydrogen; for example, S will form a certain stable hydride with hydrogen inside the alloy, making the dehydrogenation process require a higher temperature and a longer time to achieve the same dehydrogenation effect; on the contrary, when the S content is controlled below 0.01%, the dehydrogenation process is more smooth; under the same dehydrogenation treatment conditions (such as dehydrogenation temperature and time), the hydrogen in the alloy can be more effectively removed, reducing the hydrogen content to a lower level, and improving the quality and performance stability of the Kovar alloy foil.

[0063] The technical solution of the present invention will be further elaborated below in combination with multiple embodiments:

[0064] Example 1

[0065] Prepare Kovar alloy raw materials. The composition of the Kovar alloy raw materials is in mass percentage: C = 0.015%, P = 0.01%, S = 0.01%, Mn = 0.35%, Si = 0.20%, Cu = 0.10%, Cr = 0.10%, Mo = 0.10%, Ni = 28.8%, Co = 17.0%, Zr = 0.1%, Nb = 0.05%, and the balance is Fe;

[0066] Place the Kovar alloy raw materials in a melting furnace and melt them at 1600°C. An argon protection atmosphere is used during the melting process; the mold is made of H13 steel, and the inner surface of the mold is finely polished and processed so that the surface roughness Ra reaches 0.8 μm; apply boron nitride coating on the inner wall of the mold, and the coating thickness is 0.05 mm; first keep the melted metal liquid in an environment with a vacuum degree of 10 Pa for 10 minutes for preliminary vacuum treatment, then introduce argon into the metal liquid for blowing and stirring, the argon flow rate is controlled at 5 L / min, and the stirring time is 5 minutes; control the pouring temperature at 1550°C, adopt the bottom pouring method, and the pouring speed is controlled at 2 kg / s; wrap the outside of the mold with aluminosilicate fiber, and the thickness of the insulation layer is controlled at 30 mm;

[0067] The ingot is preheated by heating it to 550°C at a heating rate of 60°C / h for 2 hours of holding time, and then heated to 1150°C at a rate of 100°C / h for forging; the deformation per pass is controlled at 12%, first rough forging is carried out 3 times, and then finish forging is carried out 5 times; the forging equipment is a hydraulic press, and the pressure is controlled at 100 MPa; during the forging process, axial forging is carried out first, and the forging reduction per time is controlled at 10 mm, and then radial forging is carried out, and the forging reduction per time is controlled at 10 mm; after forging is completed, the billet is placed in a holding furnace and slowly cooled with the furnace, and the cooling rate is controlled at 60°C / h;

[0068] First, use a grinding wheel to polish and remove the oxide scale on the surface of the billet, the grinding pressure is 0.2 MPa, and the grinding speed is 10 m / min; then place the billet in a chemical cleaning tank, the cleaning solution is dilute hydrochloric acid (concentration 8%), add an inhibitor (0.8% of the acid solution mass), the cleaning time is 15 minutes, and the stirring speed during the cleaning process is 30 r / min; after cleaning, rinse with clean water, the rinsing pressure is 0.1 MPa, and the rinsing time is 3 minutes, and finally dry at 90°C for 1.5 hours; first use an ultrasonic flaw detector to detect the billet, the ultrasonic flaw detection frequency is 2.5 MHz, for large-volume billets, multi-probe and multi-angle flaw detection are adopted, and the probe spacing is controlled at 50 mm; then carry out magnetic particle flaw detection, the magnetic particle concentration is 10 g / L, the magnetization current is 500 A, and the magnetic field strength is 2000 Gs; if surface micro-defects are found (defect size less than 2 mm), use the grinding method for repair; if internal large defects are found (defect size greater than 5 mm or defect depth exceeding 10% of the billet thickness), the billet is scrapped; the repaired part is subjected to flaw detection again;

[0069] Place the cooled billet in a dehydrogenation furnace, fill the dehydrogenation furnace with argon, heat it to 1430°C for dehydrogenation treatment for 2.5 hours; after dehydrogenation is completed, cool it to room temperature naturally with the furnace; use a grinding machine to grind the alloy after dehydrogenation treatment, and the grinding direction remains unchanged all the time; use a polishing machine to polish the alloy after grinding treatment;

[0070] The alloy after dehydrogenation treatment is subjected to hot rolling treatment, the hot rolling temperature is 410°C, and the hot rolling time is 70 minutes; the alloy after hot rolling is subjected to three cold rolling, cleaning and annealing; after the first cold rolling, it is annealed at 470°C for 65 minutes, and the cleaning is carried out with dilute hydrochloric acid; after the second cold rolling, it is annealed at 780°C for 60 minutes; after the third cold rolling, it is annealed at 530°C for 60 minutes to obtain a Kovar alloy foil with the target thickness; the foil after the third annealing is cleaned with an ultrasonic cleaner for 10 minutes, and then polished.

[0071] Example Two

[0072] Prepare Kovar alloy raw materials. The composition of the Kovar alloy raw materials is by mass percentage: C = 0.01%, P = 0.005%, S = 0.005%, Mn = 0.4%, Si = 0.15%, Cu = 0.08%, Cr = 0.08%, Mo = 0.08%, Ni = 29%, Co = 17.15%, Zr = 0.15%, Nb = 0.1%, and the balance is Fe;

[0073] Place the Kovar alloy raw materials in a melting furnace and melt them at 1650°C. An argon protective atmosphere is used during the melting process; the mold is made of H13 steel, and the inner surface of the mold is finely ground and polished to make the surface roughness Ra reach 1.2 μm; apply boron nitride coating on the inner wall of the mold, and the coating thickness is 0.08 mm; first, keep the melted metal liquid in an environment with a vacuum degree of 30 Pa for 12 minutes for preliminary vacuum treatment, then introduce argon into the metal liquid for gas blowing and stirring, the argon flow rate is controlled at 8 L / min, and the stirring time is 6 minutes; control the pouring temperature at 1580°C, adopt the bottom-pouring method, and control the pouring speed at 3 kg / s; wrap the outside of the mold with aluminosilicate fiber, and control the thickness of the insulation layer at 40 mm;

[0074] Heat the ingot to 580°C for preheating at a heating rate of 70°C / h, keep the temperature for 2.5 hours, and then heat it to 1180°C at a rate of 110°C / h for forging; control the deformation amount per pass at 15%, first perform rough forging 4 times, and then perform finish forging 6 times; the forging equipment is a hydraulic press, and the pressure is controlled at 120 MPa; during the forging process, first perform axial forging, and control the forging reduction amount per time at 15 mm, then perform radial forging, and control the forging reduction amount per time at 15 mm; after forging, wrap the billet with asbestos insulation material for cooling, the thickness of the insulation material is 25 mm, and control the cooling speed at 70°C / h;

[0075] First, use a wire brush to polish and remove the oxide scale on the surface of the billet. The polishing pressure is 0.3 MPa, and the polishing speed is 12 m / min. Then, place the billet in a chemical cleaning tank. The cleaning solution is dilute sulfuric acid (concentration 7%), and a corrosion inhibitor (0.9% of the acid solution mass) is added. The cleaning time is 20 minutes, and the stirring speed during cleaning is 40 r / min. After cleaning, rinse with clean water. The rinsing pressure is 0.2 MPa, and the rinsing time is 4 minutes. Finally, dry at 100 °C for 1.8 hours. First, use an ultrasonic flaw detector to detect the billet. The ultrasonic flaw detection frequency is 3 MHz. For large-volume billets, multi-probe and multi-angle flaw detection are used, and the probe spacing is controlled at 60 mm. Then, perform magnetic particle flaw detection. The magnetic particle concentration is 15 g / L, the magnetization current is 600 A, and the magnetic field strength is 2500 Gs. If surface micro-defects (defect size less than 2 mm) are found, repair them by welding. If large internal defects (defect size greater than 5 mm or defect depth exceeding 10% of the billet thickness) are found, the billet is scrapped. The repaired part is subjected to flaw detection again.

[0076] Place the cooled billet in a dehydrogenation furnace, fill the dehydrogenation furnace with argon, heat to 1450 °C for dehydrogenation treatment, and the dehydrogenation time is 3 hours. After dehydrogenation is completed, cool naturally in the furnace to room temperature. Use a grinding machine to grind the alloy after dehydrogenation treatment. The cross-grinding method is adopted during grinding (that is, first grind in one direction for a certain number of times, and then grind in the vertical direction for the same number of times). Use a polishing machine to polish the alloy after grinding treatment, and control the polishing pressure and rotation speed within a suitable range during the polishing process.

[0077] The alloy after dehydrogenation treatment is subjected to hot rolling treatment. The hot rolling temperature is 420 °C, and the hot rolling time is 75 minutes. The alloy after hot rolling is subjected to three cold rolling, cleaning, and annealing processes. After the first cold rolling, anneal at 475 °C for 70 minutes, and the cleaning uses dilute hydrochloric acid. After the second cold rolling, anneal at 785 °C for 65 minutes. After the third cold rolling, anneal at 535 °C for 65 minutes to obtain the Kovar alloy foil with the target thickness. The foil after the third annealing is cleaned with an ultrasonic cleaning machine for 12 minutes, and then polished.

[0078] Example 3

[0079] Prepare Kovar alloy raw materials. The composition of the Kovar alloy raw materials is in mass percentage: C = 0.008%, P = 0.003%, S = 0.003%, Mn = 0.42%, Si = 0.12%, Cu = 0.06%, Cr = 0.06%, Mo = 0.06%, Ni = 29.1%, Co = 17.2%, Zr = 0.18%, Nb = 0.12%, and the balance is Fe.

[0080] Place the Kovar alloy raw materials in a melting furnace and melt them at 1680 °C under an argon protective atmosphere during the melting process; select H13 steel for the mold, and perform fine grinding and polishing on the inner surface of the mold to make the surface roughness Ra reach 1.4 μm; apply boron nitride coating on the inner wall of the mold, and the coating thickness is 0.09 mm; first keep the melted metal liquid in an environment with a vacuum degree of 40 Pa for 13 minutes for preliminary vacuum treatment, then introduce argon into the metal liquid for gas blowing and stirring, control the argon flow rate at 9 L / min, and the stirring time is 7 minutes; control the pouring temperature at 1590 °C, adopt the bottom-pouring method, and control the pouring speed at 4 kg / s; wrap the outside of the mold with aluminosilicate fiber, and control the thickness of the insulation layer at 45 mm;

[0081] Preheat the ingot by heating it to 590 °C at a heating rate of 75 °C / h, with a holding time of 2.8 hours, and then heat it to 1190 °C at a rate of 115 °C / h for forging; control the deformation amount per pass at 16%, first perform rough forging 4 times, and then perform finish forging 7 times; the forging equipment is a hydraulic press, and the pressure is controlled at 130 MPa; during the forging process, first perform axial forging, control the forging reduction amount per time at 18 mm, and then perform radial forging, control the forging reduction amount per time at 18 mm; after forging, wrap the billet with asbestos insulation material for cooling, the thickness of the insulation material is 28 mm, and the cooling rate is controlled at 75 °C / h;

[0082] First, use a grinding wheel to polish and remove the oxide scale on the surface of the billet, with a grinding pressure of 0.35 MPa and a grinding speed of 13 m / min; then place the billet in a chemical cleaning tank, the cleaning solution is dilute hydrochloric acid (concentration 9%), add an inhibitor (0.95% of the acid solution mass), the cleaning time is 22 minutes, and the stirring speed during the cleaning process is 45 r / min; after cleaning, rinse with clean water, the rinsing pressure is 0.25 MPa, the rinsing time is 4 minutes, and finally dry at 105 °C for 1.9 hours; first use an ultrasonic flaw detector to detect the billet, the ultrasonic flaw detection frequency is 3.5 MHz, for large-volume billets, use multiple probes and multi-angle flaw detection, and control the probe spacing at 70 mm; then perform magnetic particle flaw detection, the magnetic particle concentration is 18 g / L, the magnetization current is 700 A, and the magnetic field strength is 2800 Gs; if surface micro-defects are found (defect size less than 2 mm), use the grinding method for repair; if internal large defects are found (defect size greater than 5 mm or defect depth exceeding 10% of the billet thickness), the billet will be scrapped; the repaired part will be subjected to flaw detection again;

[0083] Place the cooled billet in a dehydrogenation furnace, fill the furnace with argon, heat it to 1460 °C for dehydrogenation treatment, and the dehydrogenation time is 3.2 hours. After dehydrogenation is completed, let it cool naturally in the furnace to room temperature. Use a grinding machine to grind the alloy after dehydrogenation treatment, and adopt a spiral grinding path (grind from the center outwards in a spiral). Use a polishing machine to polish the alloy after grinding treatment, and regularly replace the polishing liquid during the polishing process to ensure the polishing effect.

[0084] The alloy after dehydrogenation treatment is subjected to hot rolling treatment, the hot rolling temperature is 425 °C, and the hot rolling time is 78 minutes. The alloy after hot rolling is subjected to three times of cold rolling, cleaning and annealing. After the first cold rolling, it is annealed at 478 °C for 72 minutes, and the cleaning is carried out with dilute hydrochloric acid. After the second cold rolling, it is annealed at 788 °C for 68 minutes. After the third cold rolling, it is annealed at 538 °C for 68 minutes to obtain the Kovar alloy foil with the target thickness. The foil after the third annealing is cleaned with an ultrasonic cleaning machine for 13 minutes, and then polished.

[0085] Example 4

[0086] Prepare Kovar alloy raw materials. The composition of the Kovar alloy raw materials is calculated by mass percentage: C = 0.005%, P = 0.002%, S = 0.002%, Mn = 0.45%, Si = 0.1%, Cu = 0.05%, Cr = 0.05%, Mo = 0.05%, Ni = 29.2%, Co = 17.3%, Zr = 0.2%, Nb = 0.15%, and the balance is Fe.

[0087] Place the Kovar alloy raw materials in a melting furnace and melt them at 1700 °C. An argon protective atmosphere is adopted during the melting process. The mold is made of H13 steel, and the inner surface of the mold is finely ground and polished to make the surface roughness Ra reach 1.6 μm. Apply boron nitride coating on the inner wall of the mold, and the coating thickness is 0.1 mm. First, keep the molten metal in an environment with a vacuum degree of 50 Pa for 15 minutes for preliminary vacuum treatment, and then blow argon into the molten metal for gas stirring. The argon flow rate is controlled at 10 L / min, and the stirring time is 8 minutes. Control the pouring temperature at 1600 °C, adopt the bottom-pouring method, and control the pouring speed at 5 kg / s. Wrap the outside of the mold with aluminosilicate fiber, and control the thickness of the insulation layer at 50 mm.

[0088] The ingot is preheated by heating it to 600°C at a heating rate of 80°C / h for 3 hours, and then heated to 1200°C at a rate of 120°C / h for forging; the deformation per pass is controlled at 18%. First, rough forging is carried out 5 times, and then finish forging is carried out 8 times; the forging equipment is a hydraulic press, and the pressure is controlled at 150 MPa; during forging, axial forging is carried out first, and the forging reduction per time is controlled at 20 mm, and then radial forging is carried out, and the forging reduction per time is controlled at 20 mm; after forging, the billet is placed in a holding furnace and slowly cooled with the furnace, and the cooling rate is controlled at 80°C / h;

[0089] First, use a wire brush to polish and remove the scale on the surface of the billet, with a polishing pressure of 0.4 MPa and a polishing speed of 15 m / min; then place the billet in a chemical cleaning tank, the cleaning solution is dilute sulfuric acid (concentration 8%), adding an inhibitor (1% of the acid solution mass), the cleaning time is 25 minutes, and the stirring speed during cleaning is 50 r / min; after cleaning, rinse with clean water, the rinsing pressure is 0.3 MPa, the rinsing time is 5 minutes, and finally dry at 110°C for 2 hours; first, use an ultrasonic flaw detector to detect the billet, the ultrasonic flaw detection frequency is 4 MHz, for large-volume billets, multi-probe and multi-angle flaw detection is adopted, and the probe spacing is controlled at 80 mm; then carry out magnetic particle flaw detection, the magnetic particle concentration is 20 g / L, the magnetization current is 800 A, and the magnetic field strength is 3000 Gs; if surface micro-defects are found (defect size less than 2 mm), repair by welding; if large internal defects are found (defect size greater than 5 mm or defect depth exceeding 10% of the billet thickness), the billet is scrapped; the repaired part is detected by flaw detection again;

[0090] Place the cooled billet in a dehydrogenation furnace, fill the dehydrogenation furnace with argon, heat to 1480°C for dehydrogenation treatment, and the dehydrogenation time is 3.5 hours; after dehydrogenation, cool naturally with the furnace to room temperature; use a grinding machine to grind the alloy after dehydrogenation treatment, and adopt segmented grinding during grinding, divide the surface of the billet into several areas and grind them in turn; use a polishing machine to polish the alloy after grinding treatment, and adjust the polishing parameters according to the surface condition of the billet during polishing;

[0091] The alloy after dehydrogenation treatment is subjected to hot rolling treatment, the hot rolling temperature is 430°C, and the hot rolling time is 80 minutes; the alloy after hot rolling is subjected to three cold rolling, cleaning and annealing; after the first cold rolling, anneal at 480°C for 75 minutes, and clean with dilute hydrochloric acid; after the second cold rolling, anneal at 790°C for 70 minutes; after the third cold rolling, anneal at 540°C for 70 minutes to obtain a Kovar alloy foil with the target thickness; the foil after the third annealing is cleaned with an ultrasonic cleaning machine for 15 minutes, and then polished.

[0092] Example Five

[0093] Prepare Kovar alloy raw materials. The composition of the Kovar alloy raw materials is by mass percentage: C = 0.012%, P = 0.008%, S = 0.008%, Mn = 0.38%, Si = 0.18%, Cu = 0.09%, Cr = 0.09%, Mo = 0.09%, Ni = 28.9%, Co = 17.1%, Zr = 0.12%, Nb = 0.08%, and the balance is Fe;

[0094] Place the Kovar alloy raw materials in a melting furnace and melt at 1630°C. An argon protective atmosphere is used during the melting process; the mold is made of H13 steel, and the inner surface of the mold is finely ground and polished to make the surface roughness Ra reach 1μm; apply boron nitride coating to the inner wall of the mold, and the coating thickness is 0.06mm; first, keep the melted metal liquid in an environment with a vacuum degree of 20Pa for 11 minutes for preliminary vacuum treatment, then introduce argon into the metal liquid for gas blowing and stirring, the argon flow rate is controlled at 6L / min, and the stirring time is 6 minutes; control the pouring temperature at 1560°C, adopt the bottom-pouring method, and control the pouring speed at 3kg / s; wrap the outside of the mold with aluminosilicate fiber, and control the thickness of the insulation layer at 35mm;

[0095] Heat the ingot to 560°C for preheating at a heating rate of 65°C / h, keep the temperature for 2.2 hours, and then heat it to 1160°C at a rate of 105°C / h for forging; control the deformation amount per pass at 13%, first perform rough forging 3 times, and then perform finish forging 6 times; the forging equipment is a hydraulic press, and the pressure is controlled at 110MPa; during the forging process, first perform axial forging, and control the forging reduction amount per time at 12mm, then perform radial forging, and control the forging reduction amount per time at 12mm; after forging, wrap the billet with asbestos heat-insulating material for cooling, the thickness of the heat-insulating material is 22mm, and the cooling rate is controlled at 65°C / h;

[0096] First, use a grinding wheel to polish and remove the oxide scale on the surface of the blank. The grinding pressure is 0.25 MPa, and the grinding speed is 11 m / min. Then, place the blank in a chemical cleaning tank. The cleaning solution is dilute hydrochloric acid (concentration 8.5%), and a corrosion inhibitor (0.85% of the acid solution mass) is added. The cleaning time is 18 minutes, and the stirring speed during cleaning is 35 r / min. After cleaning, rinse with clean water. The rinsing pressure is 0.15 MPa, and the rinsing time is 3.5 minutes. Finally, dry at 95°C for 1.6 hours. First, use an ultrasonic flaw detector to detect the blank. The ultrasonic flaw detection frequency is 2.8 MHz. For large-volume blanks, use multiple probes and multi-angle flaw detection, and control the probe spacing at 55 mm. Then, perform magnetic particle flaw detection. The magnetic particle concentration is 12 g / L, the magnetization current is 550 A, and the magnetic field strength is 2200 Gs. If surface micro-defects (defect size less than 2 mm) are found, use the grinding method for repair. If internal large defects (defect size greater than 5 mm or defect depth exceeding 10% of the blank thickness) are found, the blank is scrapped. The repaired part is subjected to flaw detection again.

[0097] Place the cooled blank in a dehydrogenation furnace, fill the dehydrogenation furnace with argon, heat to 1440°C for dehydrogenation treatment, and the dehydrogenation time is 2.8 hours. After dehydrogenation is completed, cool naturally in the furnace to room temperature. Use a grinding machine to polish the alloy after dehydrogenation treatment. The reciprocating grinding method (grinding back and forth repeatedly) is used during grinding. Use a polishing machine to polish the alloy after grinding treatment, and pay attention to controlling the polishing temperature during the polishing process.

[0098] The alloy after dehydrogenation treatment is subjected to hot rolling treatment. The hot rolling temperature is 415°C, and the hot rolling time is 72 minutes. The alloy after hot rolling is subjected to three cold rolling, cleaning, and annealing processes. After the first cold rolling, anneal at 472°C for 68 minutes, and use dilute hydrochloric acid for cleaning. After the second cold rolling, anneal at 782°C for 62 minutes. After the third cold rolling, anneal at 532°C for 62 minutes to obtain the Kovar alloy foil with the target thickness. The foil after the third annealing is cleaned with an ultrasonic cleaning machine for 11 minutes, and then polished.

[0099] Comparative Example 1

[0100] Prepare Kovar alloy raw materials. The composition of the Kovar alloy raw materials is similar to that in the above example, but the trace element S is not strictly controlled. The mass percentage of S is 0.02% (higher than S≤0.01% in the example). The other main components are: C = 0.012%, P = 0.008%, Mn = 0.38%, Si = 0.18%, Cu = 0.09%, Cr = 0.09%, Mo = 0.09%, Ni = 28.9%, Co = 17.1%, Zr = 0.12%, Nb = 0.08%, and the balance is Fe.

[0101] The Kovar alloy raw materials are placed in a common melting furnace for melting at a melting temperature of 1600 °C, with a conventional nitrogen protection atmosphere; ordinary die materials are selected, and the internal surface of the die is polished and treated rather roughly, with a surface roughness Ra of about 2 μm; no special release agent is used, and casting is carried out directly; the molten metal is only simply degassed by blowing air and not vacuum-treated; the casting temperature is 1550 °C, and the casting method is top gating (different from the bottom gating of the embodiment), with a relatively fast casting speed of about 5 - 8 kg / s; the die has no heat preservation measures;

[0102] Surface cleaning only uses simple mechanical grinding, and then flaw detection is carried out directly without chemical cleaning; only an ultrasonic flaw detector is used for flaw detection, and the flaw detection frequency is fixed at 3 MHz;

[0103] The billet is placed in a dehydrogenation furnace and dehydrogenated at 1400 °C for 2.5 hours, and argon is filled during the dehydrogenation process;

[0104] The hot rolling treatment temperature is 410 °C, and the hot rolling time is 65 minutes; the number of cold rolling passes is two. After the first cold rolling, the annealing temperature is 450 °C, and the annealing time is 50 minutes; after the second cold rolling, the annealing temperature is 510 °C, and the annealing time is 50 - 60 minutes; the third cold rolling and the corresponding annealing treatment are not carried out.

[0105] Comparative Example 2

[0106] Prepare Kovar alloy raw materials. The composition of the Kovar alloy raw materials is by mass percentage: C = 0.015%, P = 0.01%, S = 0.015% (slightly higher than the embodiment), Mn = 0.35%, Si = 0.20%, Cu = 0.10%, Cr = 0.10%, Mo = 0.10%, Ni = 28.8%, Co = 17.0%, Zr = 0.1%, Nb = 0.05%, and the balance is Fe;

[0107] The die preparation is similar to that of the embodiment, but during the casting process, the degassing treatment is insufficient, and only a short blowing and stirring are carried out. The argon flow rate is 4 L / min, and the stirring time is 4 minutes; the casting temperature is 1600 °C, the casting speed is 4.5 kg / s, and bottom gating is used, but the thickness of the die insulation layer is relatively thin, about 25 mm;

[0108] In the heating process, the preheating temperature is 530 °C, the heat preservation time is 1.5 hours, the rate of heating up to the forging temperature is 90 °C / h, and the forging temperature is 1150 °C; the deformation amount per pass is between 20%, the number of rough forging passes is 3 times, and the number of finish forging passes is 4 times; the forging equipment is a small hydraulic press, and the pressure is controlled at 100 MPa; after forging, air cooling is used for cooling, and the cooling speed is relatively fast;

[0109] During surface cleaning, the grinding pressure is 0.2 MPa, the grinding speed is 10 m / min, the chemical cleaning solution is dilute hydrochloric acid (concentration 7%), the inhibitor addition amount is 0.7% of the acid solution mass, the cleaning time is 13 minutes, and the stirring speed is 25 r / min; during flaw detection, the ultrasonic flaw detection frequency is 3.5 MHz, the probe spacing is 60 mm, during magnetic particle flaw detection, the magnetic particle concentration is 15 g / L, the magnetization current is 600 A, and the magnetic field strength is 2500 Gs;

[0110] Put the billet into the dehydrogenation furnace, the dehydrogenation temperature is 1440 °C, and the dehydrogenation time is 2.5 hours;

[0111] The hot rolling treatment temperature is 420 °C, and the hot rolling time is 65 minutes; the cold rolling is carried out twice. After the first cold rolling, the annealing temperature is 470 °C, and the annealing time is 70 minutes; after the second cold rolling, the annealing temperature is 770 °C, and the annealing time is 60 minutes; the third cold rolling and the corresponding annealing treatment are not carried out.

[0112] Comparative Example 3

[0113] Compared with Comparative Example 2, the step of putting the billet into the dehydrogenation furnace for dehydrogenation is reduced, that is:

[0114] Prepare the Kovar alloy raw material. The composition of the Kovar alloy raw material is by mass percentage: C = 0.015%, P = 0.01%, S = 0.015% (slightly higher than the example), Mn = 0.35%, Si = 0.20%, Cu = 0.10%, Cr = 0.10%, Mo = 0.10%, Ni = 28.8%, Co = 17.0%, Zr = 0.1%, Nb = 0.05%, and the balance is Fe;

[0115] The mold preparation is similar to the example, but during the pouring process, the degassing treatment is not sufficient, only a short blowing and stirring are carried out, the argon flow rate is 4 L / min, and the stirring time is 4 minutes; the pouring temperature is 1600 °C, the pouring speed is 4.5 kg / s, and bottom pouring is adopted, but the thickness of the mold insulation layer is relatively thin, about 25 mm;

[0116] In the heating process, the preheating temperature is 530 °C, the heat preservation time is 1.5 hours, the heating rate to the forging temperature is 90 °C / h, and the forging temperature is 1150 °C; the deformation amount per pass is between 20%, the rough forging pass is 3 times, and the finish forging pass is 4 times; the forging equipment is a small hydraulic press, and the pressure is controlled at 100 MPa; after forging, air cooling is adopted, and the cooling speed is relatively fast;

[0117] During surface cleaning, the grinding pressure is 0.2 MPa, the grinding speed is 10 m / min, the chemical cleaning solution is dilute hydrochloric acid (concentration 7%), the addition amount of the corrosion inhibitor is 0.7% of the mass of the acid solution, the cleaning time is 13 minutes, and the stirring speed is 25 r / min; during flaw detection, the ultrasonic flaw detection frequency is 3.5 MHz, the probe spacing is 60 mm, the magnetic powder concentration during magnetic particle flaw detection is 15 g / L, the magnetization current is 600 A, and the magnetic field strength is 2500 Gs;

[0118] The hot rolling treatment temperature is 420 °C, and the hot rolling time is 65 minutes; cold rolling is carried out twice. After the first cold rolling, the annealing temperature is 470 °C, and the annealing time is 70 minutes; after the second cold rolling, the annealing temperature is 770 °C, and the annealing time is 60 minutes; the third cold rolling and the corresponding annealing treatment are not carried out.

[0119] Next, the hydrogen content (ppm), tensile strength (MPa), yield strength (MPa), elongation (%) , hardness (HV), surface roughness (μm), and thickness uniformity (μm) of the Kovar alloy foils prepared in Examples 1 to 5 and Comparative Examples 1 to 3 are measured and the performance parameters are compared respectively.

[0120] Hydrogen content measurement:

[0121] Using a LECOR H-600 hydrogen analyzer, cut 1 g samples from the Kovar alloy foils prepared in each of the above examples and comparative examples. Use a cutting tool to cut the samples into small pieces to ensure that the samples can completely enter the reaction furnace of the analyzer. Place the samples in a clean and dry quartz boat; calibrate the hydrogen analyzer with a sample of known hydrogen content (such as a Kovar alloy standard sample with a known hydrogen content). According to the requirements of the instrument operation manual, put the standard sample into the instrument, measure, and adjust the parameters of the instrument to make the measured value match the known hydrogen content of the standard sample; place the boat containing the sample into the sample inlet of the hydrogen analyzer, start the instrument, and the instrument automatically sends the sample into the high-temperature reaction furnace. The sample releases hydrogen at high temperature; the hydrogen enters the detection system with the carrier gas, and the instrument records and calculates the hydrogen content and displays the measurement result in ppm (parts per million).

[0122] Tensile strength and yield strength measurement:

[0123] Using an Instron 5982 series electronic universal testing machine, in accordance with the requirements of the national standard GB / T 228.1-2010 "Tensile testing of metallic materials - Part 1: Method of test at room temperature", for kovar alloy foil, dumbbell-shaped specimens are made. The gauge length is 50 mm, the width is 10 mm (appropriately adjusted according to the actual thickness of the foil), and the thickness is the actual thickness of the foil. Then, the surface of the specimen is polished with sandpaper to remove the oxide layer and defects, ensuring a smooth surface. Adjust the chuck spacing of the universal material testing machine to a suitable position to accommodate the specimen length. Set the test speed to 3 mm / min. Turn on the force sensor and displacement sensor of the testing machine and perform a zeroing operation to ensure accurate initial data. Clamp the two ends of the specimen in the upper and lower chucks of the testing machine, ensuring that the specimen is clamped and perpendicular to the chuck axis. Start the testing machine to apply tensile force. The testing machine automatically records the tensile force and the elongation of the specimen, and plots the stress-strain curve. When the specimen breaks, the testing machine stops loading and records the maximum tensile force value F max , the tensile strength σ b The calculation formula is: σ b = F max / A, where A is the original cross-sectional area of the specimen (A = width × thickness); for materials with an obvious yield phenomenon, find the yield force F y of the yield plateau on the stress-strain curve, and the yield strength σ y = F y / A; for materials without an obvious yield phenomenon, the specified plastic extension strength (such as Rp0.2, that is, the stress when the plastic extension rate is 0.2%) is usually used as the yield strength, and it is calculated by finding the corresponding force value on the stress-strain curve.

[0124] Elongation measurement:

[0125] Using an Instron 5982 series electronic universal testing machine, during the tensile test, measure the ratio of the gauge elongation of the specimen after fracture to the original gauge length, which is the elongation. That is, during the tensile test for measuring the tensile strength, simultaneously record the gauge elongation of the specimen. After the specimen breaks, butt the broken specimen together and use a measuring tool (such as a vernier caliper) to measure the total length L f of the gauge section after fracture. The calculation formula for the elongation δ is: δ = (L f - L 0 ) / L 0 × 100%, where L 0 is the original gauge length of the specimen (selected as 50 mm here).

[0126] Hardness measurement:

[0127] Using an MHV-1000Z type automatic turret micro-Vickers hardness tester, cut the Kovar alloy foil into specimens with a size of 10 mm × 10 mm, and the thickness is the actual thickness of the foil. Polish and buff the surface of the specimens to make it flat and smooth without oxide layer and scratches to ensure the accuracy of hardness measurement. Set the test force to 0.4 kgf (1 kgf = 9.8 N). Set the loading time and holding time of the hardness tester, the loading time is 15 s, and the holding time is 15 s. Place the specimen on the working table of the hardness tester, adjust the focal length to make the indenter clearly align with the specimen surface. Start the hardness tester, the indenter presses into the specimen surface under the action of the test force, and remove the test force after maintaining the specified time. Use a microscope to measure the lengths of the two diagonals d 1 and d 2 ; The calculation formula for the Vickers hardness value HV is: HV = 1.8544F / d 2 , where F is the test force (N), d = (d 1 +d 2 ) / 2 is the average length of the indentation diagonal (mm); The calculation result is averaged. Measure 8 points at different positions on the specimen surface, and then take the average value as the hardness value of the specimen.

[0128] Surface roughness measurement:

[0129] Use a Taylor-Hobson Surtronic S-128 type surface roughness meter. Cut a flat area from the Kovar alloy foil as the measurement sample, with an area of 50 mm × 50 mm. Ensure that the sample surface is clean without impurities such as dust and oil to avoid affecting the measurement results. Calibrate the surface roughness measuring instrument with a standard roughness sample. Place the standard sample on the measuring table and perform the calibration operation to make the instrument measurement value match the known roughness value of the standard sample. Place the sample flat on the measuring table and fix it to avoid movement during the measurement. Gently place the measuring probe on the sample surface and start the measuring instrument. The probe scans and measures the sample surface at a certain speed and stroke. The instrument automatically records the measurement data and calculates the surface roughness parameters; Measure 5 times at different positions on the sample surface and take the average value as the surface roughness value of the foil.

[0130] Thickness uniformity measurement:

[0131] Use a Mahr Millimar C1208 thickness gauge made in Germany. Select a whole square kovar alloy foil with a side length of 100 mm as the measurement object, ensuring that the foil is flat, without wrinkles and deformation. On the square foil with a side length of 100 mm, select a measurement point every 20 mm, for a total of 25 points. When using a micrometer, make the micrometer screw contact the foil surface perpendicularly, gently rotate the thimble until the micrometer screw just touches the foil surface. After hearing a "click" sound, read the value on the micrometer and record it as the thickness value of this point. When using a film thickness gauge, place the measurement probe on the selected measurement point according to the instrument operation instructions, and the instrument will automatically display the thickness value of this point. Calculate the average value of the thickness values of all measurement points Calculate the thickness value t of each measurement point i And the average value Deviation The thickness uniformity is expressed by the maximum deviation value max(|Δt i |), with the unit of μm; that is, thickness uniformity = max(|Δt i |), where i = 1, 2,..., n, and n is the total number of measurement points.

[0132]

[0133] Conduct a comparative analysis on the various performance parameters measured in Examples 1 to 5 and Comparative Examples 1 to 3 above.

[0134] In terms of hydrogen content:

[0135] The hydrogen content in Examples 1 to 5 ranges from 1.93 to 2.56 ppm, which is generally at a relatively low level; this benefits from the strict control of raw materials, melting, casting and other processes during the preparation; for example, an argon protection atmosphere is used during melting to prevent alloy oxidation and hydrogen absorption; during the casting process, sufficient degassing treatment is carried out. For example, in Example 2, the molten metal is first kept in an environment with a vacuum degree of 30 Pa for 12 minutes for preliminary vacuum treatment, and then argon is introduced for blowing and stirring, effectively reducing the hydrogen content in the molten metal; the hydrogen contents of Comparative Example 1 and Comparative Example 2 are 4.85 ppm and 3.91 ppm respectively, which are significantly higher than those of the example group; in Comparative Example 1, the control of trace element S is relatively loose (S = 0.02%, higher than S ≤ 0.01% in the examples), and the protection atmosphere and degassing measures during melting and casting are not as perfect as those in the examples, which may lead to more hydrogen entering the alloy; there are also differences in the process of Comparative Example 2 before the dehydrogenation step compared with the examples, such as insufficient degassing treatment, resulting in a higher hydrogen content; due to the lack of the dehydrogenation furnace dehydrogenation step in Comparative Example 3, the hydrogen content is as high as 6.22 ppm, which is the highest among all groups; this fully demonstrates the importance of dehydrogenation treatment for reducing the hydrogen content of Kovar alloy foil. If dehydrogenation treatment is not carried out, a large amount of hydrogen will remain in the alloy, seriously affecting the material properties.

[0136] In terms of mechanical properties (tensile strength, yield strength, elongation):

[0137] Examples 1 to 5 showed good performance in terms of tensile strength, yield strength, and elongation; the tensile strength was between 520 - 550 MPa, the yield strength was between 480 - 505 MPa, and the elongation was between 28% - 35%; this was because a reasonable forging process was adopted during preparation, such as a forging method with multiple passes and small deformation amounts (the deformation amount per pass was controlled between 12% - 18%), gradually refining the microstructure and improving the mechanical properties of the material; at the same time, controlling the uniformity of the furnace atmosphere during heating to prevent local oxidation or decarburization of the ingot also contributed to improving the strength and toughness of the material; the tensile strength of Comparative Example 1 was 460 MPa, the yield strength was 420 MPa, and the elongation was 20%; the tensile strength of Comparative Example 2 was 485 MPa, the yield strength was 440 MPa, and the elongation was 23%; compared with the Example group, the mechanical properties were significantly worse; this was mainly due to deficiencies in aspects such as raw material composition control, melting and casting process, and forging process; for example, in Comparative Example 1, the internal surface treatment of the mold was relatively rough, no special release agent was used, the pouring method was top pouring without heat preservation measures, the heating rate was fast, the number of passes was small, the deformation amount was large, and the impact force and frequency of the equipment were unstable during the forging process, these factors led to non-uniform material microstructure and more defects, thus reducing the mechanical properties; the mechanical properties of Comparative Example 3 were the worst, the tensile strength was only 450 MPa, the yield strength was 410 MPa, and the elongation was 18%; in addition to having similar problems to Comparative Example 1 and Comparative Example 2 during the preparation process, the lack of a dehydrogenation treatment step made the hydrogen content in the material too high, and hydrogen would form defects such as hydrogen embrittlement inside the material, severely weakening the mechanical properties of the material and resulting in a significant decrease in its tensile strength, yield strength, and elongation.

[0138] In terms of hardness:

[0139] The hardness of Examples 1 to 5 is between 145 - 152 HV, and the hardness value is relatively stable and within a reasonable range. This is because during the entire preparation process, from raw material selection to fine control of each process step, the uniformity and compactness of the material's organizational structure are ensured, resulting in good hardness performance. For example, during the billet treatment process, a combination of mechanical grinding and chemical cleaning is used for surface cleaning, preparing for subsequent flaw detection and processing operations, and reducing the impact of surface defects on hardness measurement. At the same time, a reasonable heat treatment process (such as multiple cold rolling and annealing treatments) also helps to adjust the hardness of the material. The hardness of Comparative Example 1 and Comparative Example 2 is 130 HV and 135 HV respectively, lower than the Example group. Insufficient process control in the comparative examples, such as unstable melting temperature and unreasonable forging process, may lead to non-uniformity of the material's organizational structure, thus affecting the hardness. The hardness of Comparative Example 3 is 125 HV, the lowest among all groups. This is because it not only has the process problems of Comparative Example 1 and Comparative Example 2, but also the high hydrogen content has a negative impact on the hardness of the material. Hydrogen can change the lattice structure of the material and reduce the hardness of the material.

[0140] In terms of surface roughness:

[0141] The surface roughness of Examples 1 to 5 is between 0.052 - 0.085 μm, and the surface quality is good. During the preparation process, attention is paid to the surface treatment of the mold and the use of mold release agents. For example, the inner surface of the mold is finely ground and polished, and the surface roughness Ra is controlled within a lower range. At the same time, a high-temperature resistant mold release agent is applied to the inner wall of the mold, reducing the adhesion between the ingot and the mold and lowering the possibility of surface defects. During subsequent processing, such as polishing after cold rolling, the surface finish of the material is further improved. The surface roughness of Comparative Example 1 is 0.157 μm, that of Comparative Example 2 is 0.129 μm, and that of Comparative Example 3 is 0.136 μm, all higher than the Example group. The control in the comparative examples in aspects such as mold preparation, casting process, and subsequent surface treatment is not as strict as that in the examples. For example, the grinding and polishing of the inner surface of the mold in Comparative Example 1 are relatively rough, directly affecting the surface quality of the ingot and thus resulting in a higher surface roughness of the foil after subsequent processing. Similar problems also exist in Comparative Example 2 and Comparative Example 3, and differences in some process parameters (such as the concentration of the chemical cleaning solution and the addition amount of the corrosion inhibitor in Comparative Example 2 being different from those in the examples) may also affect the surface quality, resulting in a larger surface roughness.

[0142] In terms of thickness uniformity:

[0143] The thickness uniformity of Examples 1 to 5 is relatively good, with the deviation between ±1.5 - ±3 μm; during the rolling process, by precisely controlling the hot rolling and cold rolling process parameters, such as hot rolling temperature, time, number of cold rolling passes, and annealing treatment, etc., the uniform deformation of the material in the thickness direction is ensured; meanwhile, during the billet treatment and forging process, the dimensional accuracy and tissue uniformity of the billet are effectively controlled, providing a good foundation for subsequent rolling, thus ensuring the thickness uniformity of the Kovar alloy foil; the thickness uniformity deviation of Comparative Example 1 is ±6 μm, that of Comparative Example 2 is ±5 μm, and that of Comparative Example 3 is ±6.5 μm, which is significantly inferior to the example group; the deficiencies in the rolling process and the pre - billet treatment process of the comparative examples lead to poor thickness uniformity; for example, in Comparative Example 1, the forging process control is not strict and there is no heat preservation measure for the die, etc., which may cause the internal structure of the billet to be non - uniform, and it is easy to have a large thickness deviation during rolling; similar process problems also exist in Comparative Example 2 and Comparative Example 3, and in Comparative Example 3, due to the lack of dehydrogenation treatment, the material properties are more affected, and it is more difficult to ensure the thickness uniformity during the rolling process.

[0144] It should be noted that the term "including", "comprising" or any other variant thereof is intended to cover non - exclusive inclusion, so that a process, method, commodity or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, commodity or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, commodity or device including the said element.

[0145] Each embodiment in the present invention is described in a progressive manner. The same or similar parts among the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiment.

[0146] Those of ordinary skill in the art should understand that: the discussion of any above - mentioned embodiment is only exemplary, and is not intended to imply that the scope of the present disclosure is limited to these examples; under the idea of the present disclosure, the technical features among the above - mentioned embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of one or more embodiments of the present invention as described above, which are not provided in detail for the sake of brevity.

[0147] Although the present disclosure has been described in connection with specific embodiments thereof, many alternatives, modifications and variations of these embodiments will be apparent to those of ordinary skill in the art based on the foregoing description.

[0148] One or more embodiments of the present invention are intended to cover all such substitutions, modifications, and variations that fall within the scope of the present invention. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present invention shall be included within the scope of protection of this disclosure.

Claims

1. A method for preparing a kovar alloy foil, characterized in that: The preparation method comprises: S1: placing a kovar alloy raw material in a smelting furnace for smelting, and pouring the smelted metal liquid into a target mold to form a steel ingot, wherein the mass percentage of the trace element S component in the kovar alloy raw material is controlled to be: S≤0.01%, the smelting temperature is 1600-1700°C, and the smelting is carried out under an argon protective atmosphere. Before pouring, the metal liquid is kept in an environment with a vacuum degree of 10-50Pa for 10-15 minutes for preliminary vacuum treatment, and then argon is introduced into the metal liquid for blowing and stirring, the argon flow rate is controlled at 5-10L / min, and the stirring time is 5-8 minutes; the pouring adopts a bottom pouring method, the pouring temperature is 1550-1600°C, and the pouring speed is 2-5kg / s; the target mold is subjected to heat preservation treatment during the pouring process; S2: heating the steel ingot prepared in step S1, first preheating the steel ingot to 550-600°C at a heating rate of 60-80°C / h, keeping the temperature for 2-3 hours, and then heating the steel ingot to a forging temperature range of 1150-1200°C at a rate of 100-120°C / h, and controlling the oxygen content in the furnace to be below 0.05% through a furnace gas circulation device during the heating process; gradually forging the steel ingot into the desired blank shape by a multi-pass small deformation forging method, and controlling the deformation of each pass to be between 12% and 18%; S3: Cooling the blank forged in step S2 and then cleaning its surface, wherein the surface cleaning is performed by combining mechanical grinding and chemical cleaning; S4: placing the blank after surface cleaning in step S3 in a dehydrogenation furnace, and filling the dehydrogenation furnace with argon gas; allowing the dehydrogenation furnace to heat and dehydrogenate the alloy, the dehydrogenation temperature is 1430-1480° C., and the dehydrogenation time is 2.5-3.5 hours; after the dehydrogenation is completed, the dehydrogenation furnace is turned off and the alloy is naturally cooled to room temperature in the dehydrogenation furnace; S5: hot rolling the alloy after the dehydrogenation treatment in step S4, the hot rolling treatment temperature is 410-430°C, and the hot rolling time is 70-80 minutes; the hot rolled alloy is subjected to multiple cold rolling, cleaning and annealing steps to a kovar alloy foil of target thickness, wherein the annealing temperature after the first cold rolling is 470-480°C, the annealing time is 65-75 minutes, and the cleaning is carried out with dilute hydrochloric acid.

2. The method for preparing the Kovar alloy foil according to claim 1, characterized in that: The components of the Kovar alloy raw material include, by mass percentage, C≤0.015%, P≤0.01%, S≤0.01%, Mn: 0.35-0.45%, Si≤0.20%, Cu≤0.10%, Cr≤0.10%, Mo≤0.10%, Ni: 28.8%-29.2%, Co: 17.0-17.3%, Zr: 0.1-0.2%, Nb: 0.05-0.15%, and the balance is Fe.

3. The method for preparing the Kovar alloy foil according to claim 1, characterized in that: Step S3 specifically includes: Place the blank in a holding furnace and slowly cool it down with the furnace at a cooling rate of 60-80℃ / h; The blank is polished by mechanical polishing, the polishing pressure is 0.2-0.4MPa, and the polishing speed is 10-15m / min; The blank is placed in a chemical cleaning tank and cleaned with a cleaning solution for 15-25 minutes. During the cleaning process, the cleaning solution is stirred at a stirring speed of 30-50 r / min. After cleaning, the blank is rinsed with clean water at a flushing pressure of 0.1-0.3MPa and a flushing time of 3-5 minutes.

4. The method for preparing the Kovar alloy foil according to claim 1, characterized in that: Step S4 also includes: The alloy after dehydrogenation treatment is ground by a grinding machine, wherein the grinding direction remains unchanged; The polishing machine is used to polish the alloy after grinding.

5. The method for preparing the Kovar alloy foil according to claim 1, characterized in that: The hot rolled alloy is subjected to three cold rolling, cleaning and annealing steps, specifically: The hot-rolled alloy is sent to a rolling mill for the first rolling, and the rolled alloy is washed with dilute hydrochloric acid and then annealed for the first time; The alloy after the first annealing is sent to a rolling mill for a second rolling, and the rolled alloy is washed with dilute hydrochloric acid and then annealed for a second time, wherein the annealing temperature is 780-790°C and the annealing time is 60-70 minutes; The alloy after the second annealing is sent to the rolling mill for the third rolling. The rolled alloy is washed with dilute hydrochloric acid and then annealed for the third time to obtain a Kovar alloy foil of target thickness, wherein the annealing temperature is 530-540°C and the annealing time is 60-70 minutes.

6. The method for preparing the Kovar alloy foil according to claim 5, characterized in that: Step S5 also includes: The Kovar alloy foil after the third annealing is cleaned with an ultrasonic cleaner for 10-15 minutes and then polished.

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