Precise resistance alloy with low resistance temperature coefficient and manufacturing method thereof

Abstract

The invention provides a low-resistance temperature coefficient precision resistance alloy and a preparation method thereof. The alloy comprises the following components: less than or equal to 0.04% of C, 1.30%-1.50% of Si, 0.30%-0.55% of Mn, less than or equal to 0.010% of S, less than or equal to 0.010% of P, 19.70%-20.50% of Cr, 3.40%-3.70% of Al, 0.60%-1.0% of Fe and the balance of Ni and inevitable impurities. The alloy has a low resistance temperature coefficient and is widely applied to the fields of aviation, aerospace and high-end instruments and meters. The manufacturing method comprises the steps that smelting is conducted in a vacuum induction furnace, a steel ingot is obtained through casting and vacuum consumable remelting, and then heating, forging and heat treatment are conducted on the steel ingot. In the smelting process, the alloy components are ensured to be accurate by controlling the pressure in the furnace, the oxygen and nitrogen content and the smelting time. And during forging, the temperature is slowly increased to 1050-1060 DEG C, heat preservation is conducted for 2-3 hours, and finally forging is conducted to the needed form. And finally, carrying out heat treatment to improve the mechanical property and the resistance temperature coefficient stability of the material. The manufacturing method can effectively improve the alloy performance, is suitable for production of precision resistor elements, and has a wide market prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of precision alloy materials, and in particular to a precision resistance alloy with a low resistance temperature coefficient and a manufacturing method thereof. Background Art

[0002] Precision resistance alloy is a functional material with excellent resistance temperature coefficient stability. It is widely used in aviation, aerospace, nuclear energy, high-end instrumentation and other fields. It is mainly used to manufacture miniature high-resistance precision wound resistors, standard resistors, potentiometers, sliding wire resistors, self-compensating resistance strain gauge wire grids, and special resistance elements such as vibration resistance, impact resistance, corrosion resistance and radiation resistance. With the development of high-end precision instruments and electronic equipment technology, precision resistance alloys have higher and higher requirements for resistance temperature coefficient, resistance stability, mechanical properties and processing performance, among which the demand for ultra-low resistance temperature coefficient is particularly critical.

[0003] At present, the common precision resistance alloys on the market mainly include manganese copper alloy, constantan alloy and germanium manganese copper alloy. These alloys have good processing performance and welding performance, but their resistance temperature coefficient is relatively high, which cannot meet the strict requirements for ultra-low resistance temperature coefficient in the fields of aviation, aerospace and high-end precision instruments. For example, although the traditional manganese copper alloy has good mechanical properties and resistance stability, its resistance temperature coefficient is limited in the application of high-precision electronic components; and although constantan alloy and germanium manganese copper alloy have good performance in certain temperature ranges, it is still difficult to achieve ultra-low resistance temperature coefficient and stability for long-term service.

[0004] In recent years, precision resistance alloys based on the Ni-Cr-Al system (such as 6J22 alloy) have gradually become a research focus. By optimizing the composition design, such as adding an appropriate amount of Cr element to enhance corrosion resistance, adding Al element to refine the grains and form a strengthening phase Ni3Al, the comprehensive performance of the alloy can be further improved. However, the Si and Al contents of the existing 6J22 alloy are relatively low (Si≤0.2%, Al≤3.20%), and its temperature coefficient of resistance and transverse and longitudinal performance consistency have not yet reached the ideal level. In addition, the traditional 6J22 alloy still has the following technical problems in the application of high-precision instruments and electronic devices:

[0005] High resistance temperature coefficient: The primary resistance temperature coefficient and secondary resistance temperature coefficient of the existing 6J22 alloy are relatively high, and the resistance value fluctuates greatly with temperature changes, which makes it difficult to meet the strict requirements of high-precision electronic components.

[0006] Insufficient resistance stability: Due to the limitations of composition and manufacturing process, the existing 6J22 alloy may experience resistance drift during long-term service, affecting its service life and reliability.

[0007] Poor processing plasticity: While improving material strength, it is difficult for existing technologies to take into account processing plasticity. In particular, the increase in Si and Al content has an adverse effect on forging performance, resulting in a decrease in processing yield.

[0008] Mechanical properties need to be optimized: Although the mechanical properties of existing alloys have been improved, their tensile strength and ductility have not yet met the requirements of high-end applications in the aviation and aerospace fields.

[0009] Therefore, in response to the above problems, it is urgent to develop a new type of precision resistance alloy with optimized composition design, high strength and processing plasticity, and ultra-low resistance temperature coefficient to meet the higher requirements for material performance in the fields of aerospace and high-end instrumentation. In response to this demand, further increasing the Cr and Al content, reasonably introducing Si, and precisely controlling the impurity content and optimizing the smelting and forging processes have become the key technical approaches to solving this problem.

[0010] In summary, there is still room for improvement in the resistance temperature coefficient stability, processing plasticity and mechanical properties of precision resistor alloys in the existing technology. A new technical solution is urgently needed to significantly improve the resistance stability, comprehensive mechanical properties and processing performance of the material to meet the application needs of high-end fields. Summary of the invention

[0011] The technical problem to be solved by the present invention is to provide a precision resistance alloy with a low resistance temperature coefficient, so as to solve the problems of high resistance temperature coefficient, poor corrosion resistance and unstable mechanical properties existing in conventional precision resistance alloys in the prior art.

[0012] In order to overcome the defects of the above prior art, the present invention provides a low resistance temperature coefficient precision resistance alloy, the chemical composition of the alloy is: C: ≤0.04%, Si: 1.30%-1.50%, Mn: 0.30%-0.55%, S: ≤0.010%, P: ≤0.010%, Cr: 19.70%-20.50%, Al: 3.40%-3.70%, Fe: 0.60%-1.0%, the balance is Ni and unavoidable impurities.

[0013] Compared with the prior art, the low resistance temperature coefficient precision resistance alloy of the present application has the following advantages: by optimizing the alloy composition, especially increasing the content of aluminum (Al) and silicon (Si), the resistance temperature coefficient of the alloy is effectively improved, the resistivity of the material is reduced, and the impurity content in the material is reduced through a reasonable smelting process, thereby improving the strength and corrosion resistance of the material. In addition, the mechanical properties and resistance temperature coefficient stability of the material are significantly improved, so that the alloy has a wider application prospect in high-end instrumentation and aerospace fields. The low resistance temperature coefficient precision resistance alloy of the present invention increases its corrosion resistance by taking chromium (Cr) and nickel (Ni) as the main components of the alloy; adding metal aluminum (Al) and single crystal silicon (Si) during the smelting process not only enhances the strength of the steel, but also improves its corrosion resistance and processing performance. This method effectively solves the problems of high resistance temperature coefficient and insufficient strength in traditional resistance alloys, and the alloy finally obtained has a low resistance temperature coefficient and excellent comprehensive performance.

[0014] Another technical problem to be solved by the present invention is to provide a method for manufacturing a precision resistance alloy with a low resistance temperature coefficient, so as to solve the problems existing in the conventional precision resistance alloy manufacturing method in the prior art, such as lax smelting process control, high impurity content, uneven alloy composition and unstable resistance temperature coefficient.

[0015] In order to overcome the above defects of the prior art, the present invention provides a method for manufacturing the low resistance temperature coefficient precision resistance alloy, comprising the following steps: S1: Vacuum induction furnace smelting: after preparing the chemical composition of the low resistance temperature coefficient precision resistance alloy, add it into a vacuum induction furnace for smelting to obtain molten steel; S2: Casting and vacuum consumable remelting: Casting the molten steel after smelting in step S1 and then remelting it in vacuum consumable to obtain a steel ingot; S3: steel ingot forging: the steel ingot obtained in step S2 is heated to 1050-1060°C for the first time, then kept warm for the first time, heated to 1130-1150°C again, kept warm again, and then taken out of the furnace for forging; S4: heat treatment: the steel ingot forged in step S3 is subjected to heat treatment to obtain a precision resistance alloy with a low resistance temperature coefficient.

[0016] Compared with the prior art, the manufacturing method of the low resistance temperature coefficient precision resistance alloy provided by the present invention has the following advantages: the manufacturing method of the present invention significantly reduces the impurity elements in the alloy, improves the purity of the molten steel, and ensures the uniformity of the alloy composition by strictly controlling the oxygen content and nitrogen content in the furnace during the smelting process in the vacuum induction furnace; the processing plasticity and organizational uniformity of the material are improved by precisely controlling the staged heating, insulation and forging temperature, avoiding the generation of forging cracks or processing defects in traditional processes, and adopting a two-stage heat treatment process to optimize the grain structure and resistance temperature coefficient of the material, significantly improving the mechanical properties and corrosion resistance of the alloy; in addition, the manufacturing method of the present invention also ensures the plastic performance during the forging process by precisely controlling the temperature changes during heating and forging, avoiding the brittleness and crack generation of the alloy, thereby improving the mechanical properties and corrosion resistance of the material. Through these innovative processes, the present invention can effectively improve the stability and consistency of low resistance temperature coefficient precision resistance alloys, further improve the resistance temperature coefficient of the alloy, and meet the strict requirements for materials in high-end aviation, aerospace, and precision instrumentation. In summary, the present invention provides an efficient and stable method for manufacturing low resistance temperature coefficient precision resistance alloys suitable for high-end precision instrumentation, which meets the strict requirements of aerospace and other precision industries, solves the problems of process instability, high impurity content, inconsistent performance, etc. in the prior art, thereby achieving significant technical improvements and industrial value.

[0017] In a possible implementation, in step S1, the vacuum induction furnace smelting specifically includes: after preparing the materials according to the chemical composition of the low resistance temperature coefficient precision resistance alloy, mixing the raw materials except metal chromium, metal aluminum and metal silicon, and chemicallyizing them in a vacuum induction furnace, and after the raw materials are chemically 50%, adding metal chromium to the vacuum induction furnace for chemically again, and smelting after all the raw materials in the furnace are chemically smelted, and then adding metal aluminum and metal silicon to continue smelting.

[0018] Compared with the prior art, the above technical solution can avoid the uneven alloy composition caused by the one-time addition of chromium and the element burnout caused by excessive oxidation or overheating during the smelting process by adding chromium metal when the raw materials are smelted to 50%. The delayed addition of chromium metal ensures its full dissolution in the alloy and reduces the volatilization loss under high temperature conditions; the addition of aluminum metal and silicon metal is delayed until all raw materials are completely smelted, which ensures the initial uniformity of the matrix alloy composition, so that aluminum and silicon can fully react in the molten steel and effectively participate in the impurity control process such as deoxidation and desulfurization. The delayed addition of aluminum metal and silicon metal can fully combine the residual oxygen and sulfur in the molten steel to form aluminum oxide (Al2O3) and sulfide inclusions (such as MnS), and further remove them through the subsequent remelting process, significantly reducing the content of impurities such as oxygen and sulfur in the material, thereby improving the purity of the molten steel; the above implementation method can significantly reduce the local oversaturation or uneven phenomenon caused by the mixing order of different components during the smelting process by adding key metal elements in stages, and ensure the uniformity of the organization of the molten steel during the smelting stage. This uniformity directly affects the grain refinement effect during subsequent forging and heat treatment, thereby improving the overall performance of the material.

[0019] In a possible implementation manner, the pressure in the vacuum induction furnace is ≤1 Pa, and the re-processing time is 60 min-90 min.

[0020] Compared with the prior art, the above-mentioned technical scheme can effectively reduce the oxygen and nitrogen content in the molten steel by setting the vacuum condition with a pressure of ≤1Pa, because under high vacuum conditions, the partial pressures of oxygen and nitrogen are extremely low, which prompts the oxygen and nitrogen dissolved in the molten steel to escape quickly, thereby significantly reducing the influence of impurity elements on the properties of the alloy; and setting the re-melting time to 60-90 minutes can fully dissolve key elements such as metallic chromium and evenly mix them with other components of the matrix alloy. This time range ensures that the smelting process can achieve sufficient reaction without causing the burning of volatile elements such as metallic chromium and metallic aluminum due to excessive heating, thereby achieving optimal composition control; through the coordination of the air pressure environment and the precise re-melting time, the formation of inclusions in the molten steel can be effectively reduced, avoiding the damage to the uniformity of the molten steel structure caused by oxide inclusions and inadequately dissolved particles.

[0021] In a possible implementation, when the metal aluminum and the metal silicon are added, the oxygen content and the nitrogen content in the vacuum induction furnace are both lower than 20 PPM, and after the metal aluminum and the metal silicon are added, the molten steel in the vacuum induction furnace needs to meet the following conditions: C≤0.04%, S≤0.010%, P≤0.010%, H≤0.0003%, 0≤0.0015%, and N≤0.0015%.

[0022] Compared with the prior art, the above technical solution controls the oxygen content and nitrogen content below 20PPM, which can significantly reduce the formation of oxide inclusions and nitride inclusions in the molten steel. These inclusions will become the starting point of performance defects in high-end precision alloys, affecting the mechanical properties and resistance stability of the material. The low oxygen and low nitrogen environment can optimize the deoxidation effect of metal aluminum and metal silicon, so that the oxygen impurities in the molten steel can fully react with these elements to generate Al2O3 and SiO2, and quickly discharge the molten steel, further improving the purity of the molten steel; and after adding metal aluminum and metal silicon, strictly control the composition of the molten steel (such as C, S, P, H, O, N, etc.) Within the specified range, it is possible to prevent performance degradation caused by excessive impurity content. For example, low C content (≤0.04%) reduces the impact of carbide precipitation on the mechanical properties of the material; low S and P contents (≤0.010%) reduce hot brittleness and cracking tendency; ultra-low H, O, and N contents (such as H≤0.0003%, O≤0.0015%, N≤0.0015%) eliminate pores and defects caused by inclusions, and improve the density and uniformity of the material; precise composition control makes the resistivity and temperature coefficient of resistance of the alloy more stable, meeting the requirements of aviation, aerospace and high-end precision instruments for long-term stability of materials.

[0023] In a possible implementation, in step S3, the heating rate of the initial heating is ≤150°C / h, the initial insulation time is 2-3h, and the second insulation time is 1h.

[0024] Compared with the prior art, the above technical solution can effectively reduce the temperature gradient inside the steel ingot by controlling the heating rate ≤ 150℃ / h, avoid the concentration of thermal stress caused by rapid heating, thereby reducing the risk of cracking of the steel ingot caused by thermal cracks, internal stress or micro defects, preventing local overheating, and further optimizing the thermoplastic conditions of the steel ingot, which is particularly critical in the precision resistance alloy with low resistance temperature coefficient and complex composition. The initial heat preservation of 2-3 hours provides sufficient time for the temperature uniformity inside the steel ingot, while promoting the further precipitation of residual inclusions that are not completely decomposed during the smelting process and diffusing them to the forging surface under high temperature conditions, which is convenient for removal in subsequent processing, and also stabilizes the alloy structure during the heating process, reduces the tendency of grain coarsening, and improves the processing stability of the material. The second heat preservation of 1 hour further optimizes the thermoplastic range of the steel ingot by staying at a higher temperature (1130℃-1150℃) for a short time, reduces grain boundary segregation and improves grain uniformity, and provides a more ideal microstructure for subsequent forging.

[0025] In a possible implementation, in step S3, the conditions for the furnace forging are: the forging process controls the deformation of each fire to be 35%-45%, the start forging temperature is ≥1050°C, and the final forging temperature is ≥850°C.

[0026] Compared with the prior art, the above technical solution is adopted to control the deformation amount of each fire to be set to 35%-45%, which can effectively avoid the insufficient crushing of the internal grains of the material due to too small deformation or the work hardening caused by too large deformation. The deformation amount within this range can promote the recrystallization process inside the material, so that the originally larger grains are refined, and at the same time, the residual internal stress that may occur during the forging process is eliminated; at a temperature of 1050°C and above, the material is in a better thermoplastic range. At this time, the fluidity of the metal is significantly enhanced, which is conducive to the uniform deformation inside the alloy and reduces the formation of forging cracks. The higher forging temperature can also accelerate the recrystallization process and prevent the deformation from being concentrated on the surface of the material and causing insufficient internal deformation. Controlling the final forging temperature ≥850°C can ensure that the material is still in a certain plastic range at the end of the forging process, avoiding work hardening or cracking due to too low temperature, and can also ensure the uniformity of the material structure and prevent grain boundary precipitation and microcracks caused by premature cooling.

[0027] In a possible embodiment, in step S4, the heat treatment conditions are: heating the forged steel billet to 1000-1020°C at a rate of 50°C-100°C, performing initial heat preservation, air cooling, and then heating the steel billet to 490-500°C at a rate of 50°C-100°C / min, and heat preservation again.

[0028] Compared with the prior art, by adopting the above technical scheme, within the temperature range of 1000℃-1020℃, the austenitization process of the material can be fully completed, and the alloy elements are uniformly dissolved in the matrix to avoid the formation of segregation areas and uneven structures; and controlling the heating rate to 50℃-100℃ can effectively avoid the thermal stress caused by excessive temperature gradient from causing cracks or deformation of the steel billet, while ensuring uniform heat distribution and improving the internal structure; air cooling treatment helps to maintain the uniformity of the high-temperature structure of the alloy after forging, while avoiding the instability of the structure caused by rapid cooling; and heating again to 490℃-500℃, the material can form a stable precipitation strengthening phase (such as Ni3Al, etc.) within this temperature range, thereby significantly enhancing the strength and heat resistance of the alloy, and continuing to control the heating rate to 50℃-100℃ / min can not only prevent the coarsening of the structure caused by excessively rapid heating, but also ensure the uniformity of the precipitation process.

[0029] In a possible implementation manner, the initial insulation time is: a×d+t min, wherein a is 1.5-1.8, d is the value corresponding to the diameter of the steel billet, in mm; t is 5-10; and the second insulation time is 4h.

[0030] Compared with the prior art, the above technical solution is adopted, by calculating the holding time based on the diameter for the first time, and determining the initial holding time by the formula a×d+t, which accurately considers the influence of the billet diameter on the heat treatment effect, and ensures that the internal structure of billets of different specifications can be completely austenitized, and the parameter a controls the amplitude range of the holding time, and its value is 1.5-1.8, which adapts to the actual situation of different billet diameters; t is used as a correction parameter to make up for the deviation that may occur only by diameter calculation, and ensures that the holding process is more stable; the second holding time is set to 4 hours, which can ensure that the strengthening phase is fully precipitated and evenly distributed within the temperature range of 490℃-500℃, thereby maximizing the mechanical properties and stability of the material; the organizational evolution during the billet heating process is closely related to time. The above implementation method avoids the uneven organization or incomplete precipitation phase caused by insufficient time, as well as the energy waste and grain coarsening caused by too long time through the accurate calculation of the holding time. DETAILED DESCRIPTION

[0031] First, those skilled in the art should understand that these implementations are only used to explain the technical principles of the embodiments of the present application, and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0032] The present invention provides a precision resistance alloy with a low resistance temperature coefficient, the chemical composition of the alloy is: C: ≤0.04%, Si: 1.30%-1.50%, Mn: 0.30%-0.55%, S: ≤0.010%, P: ≤0.010%, Cr: 19.70%-20.50%, Al: 3.40%-3.70%, Fe: 0.60%-1.0%, the balance is Ni and unavoidable impurities.

[0033] Now, for the prior art, the ultra-low resistance temperature coefficient precision resistance alloy provided by the present invention is briefly analyzed on the alloy component system: the strength and corrosion resistance of the material are improved by adding Cr, which forms a dense Cr2O3 protective film on the surface of the material to protect the inside of the material from oxidation and corrosion by the working environment, thereby increasing the stability and service life of the material; the addition of Ni element in conjunction with Cr can effectively enhance the effect of Ni element on improving the corrosion resistance of the material; the addition of Si element can improve the elastic limit, yield point and tensile strength of the steel, while the combination of Cr and Ni can further improve the corrosion resistance of the material; the addition of Al element can refine the grains and make the structure uniform, and at the same time, it can also form a Ni3Al strengthening phase with Ni to further improve the strength of the material; in addition, the content of impurity elements such as C, P, S, H, O, and N is controlled at a low level to improve the purity of the steel, which is also beneficial to reducing the difference in the lateral and longitudinal mechanical properties of the precision resistance alloy, and is beneficial to further improve the consistency of various physical properties of the material.

[0034] The ultra-low resistance temperature coefficient precision resistance alloy of the present invention adds relatively high Al and Si elements, and the components cooperate with each other to make the transverse performance and longitudinal performance of the prepared precision resistance alloy consistent, reaching the level of homogeneous steel. Although excessive Al and Si elements are harmful to the processing plasticity of the material, the material strength is improved to a greater extent and the resistance temperature coefficient of the material is reduced, and the material has broad application prospects.

[0035] The composition of the precision resistance alloy in the present invention is mainly designed based on the following ideas: In the ultra-low temperature coefficient of resistance precision alloy, C mainly forms carbides with the added Cr, which enhances the strength and corrosion resistance of the material. However, the higher the C content, the more chromium carbides will be formed, resulting in a decrease in the Cr content in the solid solution and the formation of a chromium-poor area around the carbide, thereby reducing the corrosion resistance of the steel. The strength of the material increases with the increase of the carbon content in the steel, but the increase in strength also leads to a decrease in toughness, plasticity and corrosion resistance, especially in the material, which greatly deteriorates the forging plasticity. Therefore, in the present invention, C is controlled to be ≤0.015%, and the smaller the better.

[0036] Cr can improve the corrosion resistance and strength of steel materials. In the present invention, the Cr content is controlled at 20.0-20.2%, which can improve the corrosion resistance and strength of steel and reduce the difference in mechanical properties between the transverse and longitudinal directions of the material.

[0037] Ni is an alloying element that forms austenite. In the present invention, Ni is a matrix element, and Ni can improve the corrosion resistance of steel materials. Compared with ferrite, martensite, bainite and other structures, austenitic steel materials have more stable structures and more stable performance. Therefore, the material has better corrosion resistance and stable mechanical properties in the use environment, and the main technical parameter, the temperature coefficient of resistance, is lower.

[0038] Si, Mn, and Al are all elements that are easily combined with O. The addition of these elements ensures that the molten steel is fully deoxidized during the smelting process, making the O content in the material lower and ensuring the hot processing performance of the material. On the other hand, it strengthens the material and makes the material have higher strength. Mn can also combine with S to produce MnS, which has a higher melting point than FeS, reduces the hot brittleness of the material, and improves the hot processing plasticity of the material; the strengthening effect of Al also lies in that it can combine with Ni in the material to precipitate Ni3Al strengthening phase, greatly improving the strength of the material.

[0039] Fe can adjust the resistance properties of the material, making the material's temperature coefficient of resistance lower. Appropriate addition can ensure the stability of the material's temperature coefficient of resistance on the one hand, and reduce material costs on the other.

[0040] P, S, H, O, N and other impurity elements are used. Through vacuum smelting and consumable remelting, the content of these elements in the material can be reduced as much as possible, the purity of the material can be improved, and the thermal processing performance of the material can be ensured while also giving the material better physical and chemical properties.

[0041] The present invention also provides a method for manufacturing the low resistance temperature coefficient precision resistance alloy, which is characterized by comprising the following steps: S1: Vacuum induction furnace smelting: after preparing the chemical composition of the low resistance temperature coefficient precision resistance alloy, add it into a vacuum induction furnace for smelting to obtain molten steel; S2: Casting and vacuum consumable remelting: Casting the molten steel after smelting in step S1 and then remelting it in vacuum consumable to obtain a steel ingot; S3: steel ingot forging: the steel ingot obtained in step S2 is heated to 1050-1060°C for the first time, then kept warm for the first time, heated to 1130-1150°C again, kept warm again, and then taken out of the furnace for forging; S4: heat treatment: the steel ingot forged in step S3 is subjected to heat treatment to obtain a precision resistance alloy with a low resistance temperature coefficient.

[0042] As a preferred scheme, in the step S1, the vacuum induction furnace smelting specifically includes: after preparing the materials according to the chemical composition of the low resistance temperature coefficient precision resistance alloy, mixing the raw materials except metal chromium, metal aluminum and metal silicon, and chemicallyizing them in a vacuum induction furnace, and after the raw materials are chemically processed to 50%, adding metal chromium to the vacuum induction furnace for chemically processing again, and smelting after all the raw materials in the furnace are chemically processed, and then adding metal aluminum and metal silicon to continue smelting.

[0043] As a preferred solution, the pressure in the vacuum induction furnace is ≤1Pa, and the time for re-processing is 60min-90min.

[0044] As a preferred solution, when the metallic aluminum and metallic silicon are added, the oxygen content and nitrogen content in the vacuum induction furnace are both lower than 20PPM, and after the metallic aluminum and metallic silicon are added, the molten steel in the vacuum induction furnace must meet the following requirements: C≤0.04%, S≤0.010%, P≤0.010%, H≤0.0003%, 0≤0.0015%, and N≤0.0015%.

[0045] As a preferred solution, in step S3, the heating rate of the initial heating is ≤150°C / h, the initial insulation time is 2-3h, and the second insulation time is 1h.

[0046] As a preferred solution, in step S3, the conditions for the furnace forging are: the forging process controls the deformation of each fire to 35%-45%, the start forging temperature is ≥1050°C, and the final forging temperature is ≥850°C.

[0047] As a preferred solution, in step S4, the heat treatment conditions are as follows: heating the forged steel billet to 1000-1020°C at a rate of 50°C-100°C, performing initial heat preservation, air cooling, and then heating the steel billet to 490-500°C at a rate of 50°C-100°C / min, and heat preservation again.

[0048] As a preferred solution, the initial insulation time is: a×d+t min, wherein a is 1.5-1.8, d is the value corresponding to the diameter of the steel billet, in mm; t is 5-10; and the second insulation time is 4h.

[0049] The following is a further explanation and description of the above-mentioned technical solutions of the present invention in combination with specific data: Example 1 The present embodiment provides a low resistance temperature coefficient precision resistance alloy and a manufacturing method thereof, wherein the chemical composition of the low resistance temperature coefficient precision resistance alloy is: C 0.021%, Mn 0.42%, Si 1.38%, Al 3.57%, Cr 20.22%, Fe 0.72%, S 0.004%, P 0.002%, H 0.00015%, O 0.0012%, N 0.0010%, and the remainder is Ni and unavoidable impurities.

[0050] The method for preparing the alloy comprises the following steps: S1: Vacuum induction furnace smelting After the materials are prepared according to the chemical composition of the low resistance temperature coefficient precision resistance alloy, the raw materials except metal chromium, metal aluminum and metal silicon are mixed, and the materials are chemically processed in a vacuum induction furnace. After 50% of the raw materials are chemically processed, metal chromium is added and chemical processing is continued. After all the materials are chemically processed, the pressure in the furnace is maintained at 1Pa, and smelting is continued for 75 minutes. Under the condition that the oxygen content and nitrogen content are both lower than 20PPM, metal aluminum and single crystal silicon are added, and the composition of the molten steel is controlled to be C≤0.04%, S≤0.010%, P≤0.010%, H≤0.0003%, O≤0.0015%, and N≤0.0015%.

[0051] S2: Casting and vacuum consumable remelting The molten steel obtained in step S1 is cast to prepare a Φ406 mm steel ingot, and then consumable remelting is performed under vacuum conditions to further improve the purity and structural uniformity of the steel ingot.

[0052] S3: Ingot Forging The steel ingot obtained in step S2 was slowly heated to 1055°C at a heating rate of 150°C / h and kept at this temperature for 3 hours; then the temperature was raised to 1140°C and kept at this temperature for 1 hour before being taken out of the furnace for forging. During the forging process, the deformation amount of each fire was controlled to be 40%, the start forging temperature was 1055°C, and the final forging temperature was 850°C.

[0053] S4: Heat treatment The forged billet was heated to 1010°C at a rate of 80°C / h, kept at this temperature for 135 minutes and then air-cooled; it was then heated to 495°C at a rate of 70°C / min and kept at this temperature for 4 hours to complete the final heat treatment and obtain a □55mm forged square billet.

[0054] Example 2 The present embodiment provides a low resistance temperature coefficient precision resistance alloy and a manufacturing method thereof, wherein the chemical composition of the low resistance temperature coefficient precision resistance alloy is: C 0.018%, Mn 0.44%, Si 1.36%, Al 3.55%, Cr 20.18%, Fe 0.75%, S 0.0035%, P 0.0018%, H 0.00012%, O 0.0013%, N 0.0012%, and the remainder is Ni and unavoidable impurities.

[0055] The method for preparing the alloy comprises the following steps: S1: Vacuum induction furnace smelting After the materials are prepared according to the chemical composition of the low resistance temperature coefficient precision resistance alloy, the raw materials except metal chromium, metal aluminum and metal silicon are mixed, and the materials are chemically processed in a vacuum induction furnace. After 50% of the raw materials are chemically processed, metal chromium is added and chemical processing is continued. After all the materials are chemically processed, the pressure in the furnace is maintained at 1Pa, and smelting is continued for 70 minutes. Under the condition that the oxygen content and nitrogen content are both lower than 20PPM, metal aluminum and single crystal silicon are added, and the composition of the molten steel is controlled to be C≤0.04%, S≤0.010%, P≤0.010%, H≤0.0003%, O≤0.0015%, and N≤0.0015%.

[0056] S2: Casting and vacuum consumable remelting The molten steel obtained in step S1 is cast to prepare a Φ406 mm steel ingot, and then consumable remelting is performed under vacuum conditions to further improve the purity and structural uniformity of the steel ingot.

[0057] S3: Ingot Forging The steel ingot obtained in step S2 is slowly heated to 1050°C at a heating rate of 150°C / h and kept at this temperature for 2 hours; then the temperature is raised to 1135°C and kept at this temperature for 1 hour before being taken out of the furnace for forging. During the forging process, the deformation amount of each fire is controlled to be 35%, the starting forging temperature is 1050°C, and the final forging temperature is 850°C.

[0058] S4: Heat treatment The forged steel billet was heated to 1005°C at a rate of 60°C / h, kept at this temperature for 140 minutes and then air-cooled; it was then heated to 490°C at a rate of 80°C / min and kept at this temperature for 4 hours to complete the final heat treatment and obtain a □55mm forged square billet.

[0059] Example 3 The present embodiment provides a low resistance temperature coefficient precision resistance alloy and a manufacturing method thereof, wherein the chemical composition of the low resistance temperature coefficient precision resistance alloy is: C 0.021%, Mn 0.39%, Si 1.39%, Al 3.58%, Cr 20.25%, Fe 0.82%, S 0.0033%, P 0.0022%, H 0.00015%, O 0.0012%, N 0.0009%, and the remainder is Ni and unavoidable impurities.

[0060] The method for preparing the alloy comprises the following steps: S1: Vacuum induction furnace smelting After the materials are prepared according to the chemical composition of the low resistance temperature coefficient precision resistance alloy, the raw materials except metal chromium, metal aluminum and metal silicon are mixed, and the materials are chemically processed in a vacuum induction furnace. After 50% of the raw materials are chemically processed, metal chromium is added and the chemical processing is continued. After all the materials are chemically processed, the pressure in the furnace is maintained at 1Pa, and the smelting is continued for 65 minutes. Under the condition that the oxygen content and nitrogen content are both lower than 20PPM, metal aluminum and single crystal silicon are added, and the composition of the molten steel is controlled to be C≤0.04%, S≤0.010%, P≤0.010%, H≤0.0003%, O≤0.0015%, and N≤0.0015%.

[0061] S2: Casting and vacuum consumable remelting The molten steel obtained in step S1 is cast to prepare a Φ406 mm steel ingot, and then consumable remelting is performed under vacuum conditions to further improve the purity and structural uniformity of the steel ingot.

[0062] S3: Ingot Forging The steel ingot obtained in step S2 was slowly heated to 1060°C at a heating rate of 140°C / h and kept at this temperature for 3 hours; then the temperature was raised to 1145°C and kept at this temperature for 1 hour before being taken out of the furnace for forging. During the forging process, the deformation amount of each fire was controlled to be 45%, the starting forging temperature was 1060°C, and the final forging temperature was 850°C.

[0063] S4: Heat treatment The forged steel billet was heated to 1020°C at a rate of 70°C / h, kept at this temperature for 130 minutes and then air-cooled; it was then heated to 500°C at a rate of 50°C / min and kept at this temperature for 4 hours to complete the final heat treatment and obtain a □55mm forged square billet.

[0064] The square billets prepared in Examples 1-3 were randomly sampled and analyzed to detect the non-metallic inclusion content. The coarse and fine inclusions of Class A, Class B, and Class C inclusions were all at level 0, while the fine inclusions of Class D inclusions were at level 0.5 and the coarse inclusions were at level 0.

[0065] According to the standard requirements of GB / T 228, samples were randomly taken from the square billets prepared in Examples 1-3 to test their tensile strength, elongation after fracture, cross-sectional shrinkage, resistivity, temperature coefficient of resistance, and copper thermoelectric potential. The statistical analysis results are shown in Table 1, wherein the number of samples in the table is the number of seamless line pipes taken, and random sampling was adopted.

[0066] The existing 6J22 alloy was analyzed. The chemical composition of the existing 6J22 alloy is: C≤0.04%, Mn 0.5~1.5%, Si≤0.2%, S≤0.01%, P≤0.01%, Cr 19.00~21.50%, Al 2.70~3.20%, Fe 2.00~3.00%, and the rest are nickel and other inevitable impurity elements.

[0067] The main production process is: vacuum induction melting and casting electrode rod Φ360 → vacuum consumable remelting Φ406mm ingot → forging blank → forging into material, heat treatment.

[0068] Comparative Example: Preparation method of existing 6J22 alloy: Step a, weighing and mixing the raw materials according to the designed proportion of the chemical components, and performing vacuum induction melting and casting, and electroslag remelting to obtain a Φ406mm steel ingot; wherein the chemical composition of the steel ingot meets the chemical composition requirements of the above-mentioned existing 6J22 alloy; Step b, heating, forging and heat treating the steel ingot to obtain a square billet of □55 mm.

[0069] The specific heating process of 6J22 steel ingot is as follows: slowly heat the steel ingot to 1050~1060℃ at <150℃h, keep it warm for 2~3h, then heat it to 1135~1145℃, keep it warm for 1h, and then take it out of the furnace for forging. During the forging process, the deformation amount of each fire is controlled at 35%~45%, the start forging temperature is controlled to be ≥1050℃, and the final forging temperature is controlled to be ≥850℃.

[0070] In the heat treatment process, the forged steel billet is heated to 1000℃~1020℃ at a rate of ≤150℃ / h, kept at this temperature for 90min, and air-cooled; then the steel billet is heated to 490℃ with the furnace temperature rising and kept at this temperature for 4h.

[0071] The differences between the manufacturing method and the formula of the present invention include but are not limited to: There are great differences in element control: Mn content: The present invention controls it at 0.30%-0.55%, which is lower than 0.5%-1.5% of 6J22 alloy. By precisely controlling the Mn content, the hot working plasticity and hot brittleness resistance are optimized; Si content: The present invention significantly increases it to 1.30%-1.50% (Si≤0.2% in 6J22), improving the elastic limit, tensile strength and corrosion resistance of the alloy; Al content: The present invention increases it to 3.40%-3.70% (6J22 is 2.70%-3.20%), enhancing the precipitation of Ni3Al strengthening phase, further improving the strength and high temperature resistance; Fe content: The present invention reduces it to 0.60%-1.00% (6J22 is 2.00%-3.00%), reducing the interference with resistivity and stability; There are great differences in the manufacturing methods: the smelting of the preparation method of the present invention adopts vacuum induction melting + vacuum consumable remelting, which is more conducive to controlling the impurity content and material purity than electroslag remelting, and adds the control of the deformation amount (35%-45%) per fire to ensure the uniformity of the organization and the stability of the performance, and introduces the a×d+t formula for the initial holding time to ensure the best heat treatment effect for different billet specifications.

[0072] The square billets prepared in Examples 1-3 were randomly sampled and analyzed to detect the non-metallic inclusion content. The coarse and fine inclusions of Class A, Class B, and Class C inclusions were all at level 0, while the fine inclusions of Class D inclusions were at level 0.5 and the coarse inclusions were at level 0.

[0073] According to the standard requirements of GB / T 228, samples were randomly taken from the square billets prepared in Examples 1-3 to test their tensile strength, elongation after fracture, cross-sectional shrinkage, resistivity, temperature coefficient of resistance, and copper thermoelectric potential. The statistical analysis results are shown in Table 1, wherein the number of samples in the table is the number of seamless line pipes taken, and random sampling was adopted.

[0074] According to the standard requirements of GB / T 228, samples are randomly taken from the prepared square billets to analyze their tensile strength, elongation after fracture, cross-sectional shrinkage, resistivity, temperature coefficient of resistance, and copper thermoelectric potential. The statistical analysis results are shown in Table 1, where the number of samples in the table is the number of seamless pipes taken, and random sampling is adopted.

[0075] The following are the performance data of the 6J22 billets prepared in the above-mentioned Examples 1-3 of the present invention and the existing 6J22 billets, as shown in Table 1: Table 1: Performance data of 6J22 billets prepared in Examples 1-3 and 6J22 billets prepared in Comparative Examples Table 1 further proves that, compared with the existing 6J22 alloy, the square bars prepared in Examples 1-3 of the present invention have higher tensile strength. Although the elongation after fracture and the cross-sectional shrinkage rate are reduced, the main performance indicators including resistivity and resistance temperature coefficient are reduced. The manufacturing method of the present invention obtains an ultra-low resistance temperature coefficient precision resistor alloy with higher mechanical strength, lower resistivity, lower resistance temperature coefficient and better resistance stability through the control of composition and process.

[0076] In summary, the present invention achieves the performance improvement of the low resistance temperature coefficient precision resistance alloy by accurately designing the chemical composition and optimizing the manufacturing process. The technical principle of the present invention is further explained from the two aspects of alloy composition and manufacturing process: 1. Alloy composition design principle (1) Optimized ratio of key elements C element control: The present invention strictly controls the C content to ≤0.04% to avoid the formation of excessive carbides, thereby preventing the chromium-poor zone caused by chromium carbide and improving the corrosion resistance and hot working plasticity of the alloy.

[0077] Increase of Si element: Increased to 1.30%-1.50%, significantly enhancing the elastic limit, tensile strength and corrosion resistance of the material, while improving the corrosion resistance through synergistic effect with Cr.

[0078] Optimization of Al element: Increased to 3.40%-3.70%, significantly improving the high temperature strength and corrosion resistance of the material by generating Ni3Al strengthening phase.

[0079] Precise control of Mn element: Within the range of 0.30%-0.55%, it forms MnS with S to reduce hot brittleness while ensuring hot processing plasticity.

[0080] Synergy of Cr and Fe: Cr (19.70%-20.50%) combines with Ni and Al to form a stable austenite structure, and the Fe content is reduced to 0.60%-1.0%, avoiding adverse effects on resistance performance.

[0081] (2) Strict control of impurity elements Through vacuum smelting and vacuum consumable remelting processes, the contents of gas impurities such as H, O, and N are reduced to H≤0.0003%, O≤0.0015%, and N≤0.0015%, respectively, thereby improving the purity of the material and reducing non-metallic inclusions, thereby optimizing the mechanical and resistance properties of the alloy.

[0082] 2. Principles of manufacturing process optimization (1) Advantages of vacuum consumable remelting process Vacuum consumable remelting has a higher impurity removal capability than electroslag remelting, ensuring the internal purity of the material and avoiding fluctuations in material properties caused by inclusions.

[0083] Control smelting conditions, such as vacuum degree (≤1.0Pa) and holding time (60-90min), to further reduce the content of oxygen, nitrogen and other gases in the material.

[0084] (2) Optimization of forging process In the forging process of the present invention, the deformation amount of each fire is controlled to be 35%-45%, thereby ensuring the uniformity of forging deformation, preventing tissue segregation, and improving the strength and durability of the material.

[0085] The setting of the start forging temperature (≥1050℃) and the final forging temperature (≥850℃) ensures the thermoplasticity of the material during the forging process and avoids crack formation.

[0086] (3) Fine control of heat treatment The initial holding time is calculated according to the formula a×d+t, combined with the precise processing of the billet size to ensure uniform distribution of alloy elements; The secondary heat preservation is carried out at 490-500℃ to further improve the comprehensive performance of the material by precipitation of strengthening phase and organization adjustment.

[0087] 3. Synergistic improvement of resistance and mechanical properties Reduction of resistivity: High purity and precise alloy composition design reduce impurity obstacles in the conductive path, while refined grain structure and stable austenite structure improve conductivity.

[0088] Reduction of temperature coefficient: The increase in Al and Si content optimizes the thermoelectric performance, reduces the primary resistance temperature coefficient (α) and the secondary resistance temperature coefficient (β), and makes the alloy more adaptable to complex temperature environments.

[0089] Improvement of mechanical properties: The precipitation and high purity of Ni3Al strengthening phase ensure high strength and excellent durability. Although the elongation and cross-sectional shrinkage are slightly reduced, the overall performance indicators are better than the existing technology.

[0090] The manufacturing method of the present invention not only significantly improves the mechanical properties of the alloy (tensile strength 1350-1450MPa), but also significantly improves the resistivity (1.15-1.21μΩ·m) and the temperature coefficient of resistance (3.12-3.23×10 -6 ℃ -1 ). By comparing with the existing 6J22 alloy, it can be clearly seen that the technical solution of the present invention has significant technical advantages and application value in the fields of precision instruments and aerospace.

[0091] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" etc. means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0092] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A low resistance temperature coefficient precision resistance alloy, characterized in that: The chemical composition of the alloy is: C: ≤0.04%, Si: 1.30%-1.50%, Mn: 0.30%-0.55%, S: ≤0.010%, P: ≤0.010%, Cr: 19.70%-20.50%, Al: 3.40%-3.70%, Fe: 0.60%-1.0%, the balance is Ni and unavoidable impurities.

2. A method for manufacturing the low resistance temperature coefficient precision resistance alloy according to claim 1, characterized in that: The following steps are involved: S1: Vacuum induction furnace smelting: after preparing the chemical composition of the low resistance temperature coefficient precision resistance alloy, add it into a vacuum induction furnace for smelting to obtain molten steel; S2: Casting and vacuum consumable remelting: Casting the molten steel after smelting in step S1 and then remelting it in vacuum consumable remelting to obtain a steel ingot; S3: steel ingot forging: the steel ingot obtained in step S2 is heated to 1050-1060°C for the first time, then kept warm for the first time, heated to 1130-1150°C again, kept warm again, and then taken out of the furnace for forging; S4: heat treatment: the steel ingot forged in step S3 is subjected to heat treatment to obtain a precision resistance alloy with a low resistance temperature coefficient.

3. The method for manufacturing a precision resistance alloy with a low resistance temperature coefficient according to claim 2, characterized in that: In the step S1, the vacuum induction furnace smelting specifically includes: after preparing the materials according to the chemical composition of the low resistance temperature coefficient precision resistance alloy, mixing the raw materials except metal chromium, metal aluminum and metal silicon, and then melting the materials in a vacuum induction furnace. After the raw materials are 50% melted, adding metal chromium to the vacuum induction furnace for melting again, and smelting after all the raw materials in the furnace are melted, and then adding metal aluminum and metal silicon to continue smelting.

4. The method for manufacturing a precision resistance alloy with a low resistance temperature coefficient according to claim 3, characterized in that: The pressure in the vacuum induction furnace is ≤1Pa, and the time for re-processing is 60min-90min.

5. The method for manufacturing a precision resistance alloy with a low resistance temperature coefficient according to claim 3, characterized in that: When the metallic aluminum and metallic silicon are added, the oxygen content and nitrogen content in the vacuum induction furnace are both lower than 20PPM, and after the metallic aluminum and metallic silicon are added, the molten steel in the vacuum induction furnace must meet the following requirements: C≤0.04%, S≤0.010%, P≤0.010%, H≤0.0003%, 0≤0.0015%, and N≤0.0015%.

6. The method for manufacturing a precision resistance alloy with a low resistance temperature coefficient according to claim 2, characterized in that: In the step S3, the heating rate of the initial heating is ≤150°C / h, the initial insulation time is 2-3h, and the second insulation time is 1h.

7. The method for manufacturing a precision resistance alloy with a low resistance temperature coefficient according to claim 2, characterized in that: In step S3, the conditions for the furnace forging are: the deformation of each fire is controlled to be 35%-45% during the forging process, the start forging temperature is ≥1050°C, and the final forging temperature is ≥850°C.

8. The method for manufacturing a precision resistance alloy with a low resistance temperature coefficient according to claim 2, characterized in that: In step S4, the heat treatment conditions are as follows: heating the forged steel billet to 1000-1020°C at a rate of 50°C-100°C, performing initial heat preservation, air cooling, and then heating the steel billet to 490-500°C at a rate of 50°C-100°C / min, and heat preservation again.

9. The method for manufacturing a precision resistance alloy with a low resistance temperature coefficient according to claim 8, characterized in that: The initial insulation time is: a×d+t min, wherein a is 1.5-1.8, d is the value corresponding to the diameter of the steel billet, in mm; t is 5-10; and the second insulation time is 4h.

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