Copper-manganese alloy plate strip with ultralow copper thermal electromotive force and preparation method of copper-manganese alloy plate strip

Abstract

The invention discloses a copper-manganese alloy plate strip with ultralow copper thermal electromotive force and a preparation method of the copper-manganese alloy plate strip, and belongs to the technical field of non-ferrous metal smelting and rolling machining. The copper-manganese alloy plate strip comprises the following raw materials in percentage by mass: 11.0%-13.0% of Mn, 2.0%-3.0% of Ni, 0.1%-1% of Ce, 0.5%-1.5% of Nd, less than or equal to 0.25% of Si, 0.25%-0.5% of Fe and the balance of Cu; wherein the mass ratio of Ce to Nd is (0.07-2): 1, and alloy grains can be refined to 5-10 [mu] m. The preparation method comprises the following steps: sequentially performing casting, forging, hot rolling and solid solution heat treatment on raw materials to obtain a hot-rolled coil; carrying out surface milling, rough rolling, first annealing and medium finish rolling treatment to obtain a medium finish rolling plate strip; and finally, carrying out secondary annealing, finish rolling, withdrawal and straightening and finished product annealing treatment to obtain a copper-manganese alloy finished product plate strip. Through the unique rare earth element ratio and strict process control, the alloy plate strip with fine grains and uniform structure is obtained, the thermoelectric force of the alloy plate strip to copper is remarkably reduced, the performance is stable, and the high requirements of the fields of precision resistors and the like are met.

Description

Technical Field

[0001] This application belongs to the field of non-ferrous metal smelting and rolling technology, specifically, it relates to a copper-manganese alloy plate and strip with ultra-low thermoelectric potential to copper and its preparation method. Background Technology

[0002] Copper-manganese resistance alloys are precision resistance materials based on Cu-Mn. They occupy a core position in the electronics and instrumentation industries due to their high and stable resistivity, extremely low temperature coefficient of resistance, and relatively low thermoelectric potential (EMF) relative to copper. Their thermoelectric potential to copper in the range of 0℃ to 100℃ is typically ≤1μV / ℃, far superior to traditional constantan and manganese bronze alloys. This effectively reduces parasitic voltages introduced by contact temperature differences in precision resistance networks and electrical measuring instruments, making them a key material for ensuring the long-term stability and accuracy of microvolt-level measurement signals.

[0003] Currently, the mainstream process for producing copper-manganese alloy sheets and strips both domestically and internationally is a multi-pass rolling and annealing combination process of "vacuum melting - forging - hot rolling - cold rolling - annealing". However, the copper-manganese alloy sheets and strips produced by the existing process route still cannot meet the stringent requirements of high-end fields such as aerospace high-precision bridges and microvolt-level sensors in medical equipment. The thermoelectric potential level of ≤1μV / ℃ has become the core bottleneck restricting its application in more precise scenarios.

[0004] Therefore, developing a copper-manganese alloy sheet and strip preparation technology that can achieve a lower thermoelectric potential for copper has become an urgent need for the current industry development. Summary of the Invention

[0005] The purpose of this application is to provide a copper-manganese alloy plate and strip with ultra-low thermoelectric potential to copper and its preparation method. The method refines the grains by adding rare earth elements in a specific ratio and combining it with a strict heat treatment process, thereby synergistically reducing the thermoelectric potential of the alloy to copper.

[0006] To achieve the above objectives, this application provides a method for preparing a copper-manganese alloy strip with ultra-low thermoelectric potential to copper, comprising the following steps: The raw materials are sequentially processed through melting and casting, forging, hot rolling, and solution heat treatment to obtain hot-rolled coils. Hot-rolled coils are processed by milling, rough rolling, first annealing, and medium-precision rolling to obtain medium-precision rolled strips. The medium-precision rolled strip is subjected to a second annealing, precision rolling, tension leveling and finished product annealing to obtain copper-manganese alloy strip; The raw materials include electrolytic copper plates, industrial silicon blocks, electrolytic manganese sheets, high-purity iron blocks, nickel plates, cerium powder, and neodymium powder. The raw materials are proportioned by mass percentage as follows: Mn 11.0%~13.0%, Ni 2.0%~3.0%, Ce 0.1%~1%, Nd 0.5%~1.5%, Si≤0.25%, Fe 0.25%~0.5%, with the balance being Cu. The mass ratio of Ce to Nd is 0.07~2:1, which can refine the alloy grain to 5μm~10μm.

[0007] Furthermore, the casting process includes the following steps: placing electrolytic copper plates, electrolytic manganese sheets, and nickel plates into a melting furnace, and drawing a vacuum to ensure the vacuum level inside the furnace is ≤10Pa; starting the melting process and controlling the maximum melting power to 60kW~70kW; after the alloy liquid has completely melted, adding industrial silicon blocks, high-purity iron blocks, cerium powder, and neodymium powder, and refining at a constant temperature for 30min~45min; pouring the refined alloy liquid into a mold preheated to 200℃~300℃, and after the ingot has solidified, air-cooling it with the mold to 400℃~500℃ before demolding to obtain the ingot.

[0008] Furthermore, before casting, the process includes: electromagnetic stirring of the refined alloy liquid at a frequency of 5Hz to 10Hz for a duration of 30s to 60s.

[0009] Furthermore, the forging process includes the following steps: sawing the riser and bottom plate of the ingot obtained from the melting and casting process, turning the surface until it is smooth and free of oxide scale, heating to 800℃~850℃ and holding for 4h~6h, and forging it into a slab of (120mm~130mm)×(370mm~390mm)×(4500mm~4600mm); wherein, the temperature before forging is controlled not to be lower than 760℃ when exiting the furnace, and the final forging temperature is controlled not to be lower than 650℃ during the forging process.

[0010] Furthermore, the hot rolling process includes the following steps: heating the slab obtained from the forging process to 730℃~760℃ and holding it at that temperature for 2h~3h, and then hot rolling it to 12mm~18mm in 6 passes to obtain hot-rolled strip; wherein, the rolling speed of the first 3 passes is controlled at 1.2m / s~1.5m / s, and the speed of the last 3 passes is reduced to 0.8m / s~1.0m / s.

[0011] Furthermore, the solution heat treatment includes the following steps: holding the hot-rolled strip obtained by hot rolling at 800℃~900℃ for 3h~5h, and after the holding is completed, cooling it to room temperature with water mist and then air cooling; wherein, the cooling rate is 80℃ / s~100℃ / s.

[0012] Further, the milling and rough rolling processes include: performing double-sided milling on the hot-rolled coil after solution heat treatment, with a single-sided milling amount of 0.2mm~0.3mm; then performing multi-pass rough rolling to 2.0mm, controlling the single-pass deformation rate to 15%~25%; wherein, during the rolling process, the rolls are cooled in sections to control the temperature fluctuation of the roll surface to ≤5℃.

[0013] Furthermore, the first annealing and intermediate finishing rolling process includes: placing the strip obtained from the roughing rolling process in a bell furnace, introducing a mixed protective atmosphere, holding it at 550℃~620℃ for 3h~5h, cooling and cleaning; using a four-high mill for multi-pass intermediate finishing rolling to 0.5mm, controlling the single-pass deformation rate at 10%~20%, and controlling the roll crown at 0.02mm~0.05mm.

[0014] Furthermore, the second annealing and finishing rolling process includes: feeding the intermediate-finished strip obtained from the intermediate-finishing rolling process back into the bell furnace, introducing a mixed protective atmosphere, holding it at 450℃~500℃ for 3h~5h, cooling and cleaning; using a twelve-roll mill for finishing rolling to the target thickness, controlling the single-pass deformation rate to 5%~15%, controlling the front tension to 8kN~12kN and the back tension to 9kN~14kN during rolling, and the roll diameter difference to ≤0.005mm; wherein, the mixed protective atmosphere is nitrogen and hydrogen in a volume ratio of 3:1.

[0015] Furthermore, the tension leveling and finished product annealing processes include: tension leveling the finished strip after precision rolling, with the elongation controlled at 0.2%~0.6% and the straightening speed at 150m / min~200m / min; and feeding it into a continuous annealing furnace for annealing at 650℃~750℃ and a winding speed of 3m / min.

[0016] This application provides a copper-manganese alloy strip with ultra-low thermoelectric potential to copper, prepared by the above method. The thermoelectric potential of the copper-manganese alloy strip to copper is ≤0.3 μV / ℃.

[0017] In summary, this application has the following advantages: This application successfully prepared a copper-manganese alloy strip with ultra-low thermoelectric potential to copper and highly stable performance by combining a unique alloy composition design with an optimized multi-stage processing technology. Firstly, by precisely controlling the mass ratio of Ce and Nd, two rare earth elements, the application utilizes the modification and refining effects of rare earth elements to effectively refine the alloy grains to 5μm~10μm, laying a solid microscopic foundation for obtaining a uniform matrix structure and stable electrical properties. Secondly, this application employs a synergistic process of solution heat treatment, multi-stage rolling, intermediate annealing, and final annealing. By precisely controlling the temperature, time, deformation rate, and cooling rate at each stage, it not only fully dissolves alloy elements, eliminates processing stress, and promotes uniform recrystallization, but also effectively suppresses the precipitation of harmful phases, ultimately achieving ultimate optimization of the alloy's internal structure.

[0018] Therefore, compared with traditional materials, the copper-manganese alloy strip prepared in this application has the advantages of extremely low thermoelectric potential to copper (≤0.3μV / ℃), high thermoelectric potential uniformity, stable resistivity, flat plate shape and bright surface, which can fully meet the stringent application requirements of precision resistors, high-end measuring instruments and other applications that require material performance. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic flowchart of the method for preparing copper-manganese alloy strips with ultra-low thermoelectric potential to copper proposed in this application.

[0021] Figure 2 This is a metallographic photograph of the copper-manganese alloy strip proposed in Embodiment 1 of this application.

[0022] Figure 3 This is a metallographic photograph of the copper-manganese alloy strip proposed in Comparative Example 2 of this application. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] Copper-manganese alloys, as precision resistance alloys based on Cu-Mn, are widely used in precision resistance networks, high-precision electrical measuring instruments, aerospace, and new energy vehicle electronic control systems due to their high resistivity, low temperature coefficient of resistance, and low thermoelectric potential to copper. The thermoelectric potential to copper is one of the key indicators for evaluating the performance of this type of alloy; a lower value means a smaller parasitic voltage generated by the contact temperature difference in the measurement circuit, thus ensuring the measurement accuracy and long-term stability of microvolt-level signals. Existing technologies for preparing copper-manganese alloy strips have reached near-theoretical limits in terms of thermoelectric potential to copper, typically maintaining a level of ≤1 μV / ℃. Based on this, this application, through precise composition control and process optimization, has prepared ultra-low EMF copper-manganese alloy strips with a thermoelectric potential to copper as low as ≤0.3 μV / ℃, significantly improving product performance.

[0025] Specifically, in the first aspect, this application provides a method for preparing a copper-manganese alloy plate or strip with an ultra-low thermoelectric potential to copper, such as... Figure 1 As shown, it includes the following steps: S1. The raw materials are sequentially subjected to melting and casting, forging, hot rolling and solution heat treatment to obtain hot rolled coils.

[0026] In this specific embodiment, the raw materials include electrolytic copper plates, industrial silicon blocks, electrolytic manganese sheets, high-purity iron blocks, nickel plates, cerium powder, and neodymium powder. The raw materials are proportioned by mass percentage as follows: Mn 11.0%~13.0%, Ni 2.0%~3.0%, Ce 0.1%~1%, Nd 0.5%~1.5%, Si≤0.25%, Fe 0.25%~0.5%, with the balance being Cu. The mass ratio of Ce to Nd is 0.07~2:1, which can refine the alloy grains to 5μm~10μm. This application establishes a component system with synergistic effects of Ce and Nd composite rare earth elements. By controlling the precise proportion of 0.07~2:1, the alloy grains are stably refined to 5μm~10μm (compared to 20μm~30μm in conventional processes).

[0027] In a specific embodiment, the casting process includes the following steps: Electrolytic copper plates, electrolytic manganese sheets, and nickel plates are placed in a melting furnace, and a vacuum is drawn to ensure a vacuum level ≤10Pa; melting is started, and the maximum melting power is controlled at 60kW~70kW; after the alloy liquid is completely melted, industrial silicon blocks, high-purity iron blocks, cerium powder, and neodymium powder are added, and the mixture is kept at a constant temperature for 30min~45min; the refined alloy liquid is poured into a mold preheated to 200℃~300℃, and after the ingot solidifies, it is air-cooled with the mold to 400℃~500℃ before being demolded to obtain the ingot. This application first uses electrolytic copper plates, electrolytic manganese sheets, and nickel plates, which have relatively high melting points and are not easily volatile, as the base material for melting. After a stable alloy pool is formed, industrial silicon blocks and high-purity iron blocks are added, especially the highly reactive rare earth elements cerium and neodymium. This greatly shortens their exposure time in the high-temperature melt, minimizing losses caused by oxidation and volatilization. The entire process is carried out under a high vacuum of ≤10Pa, effectively isolating air and fundamentally inhibiting the oxidation and burn-off of active elements such as Mn, Ce, and Nd, ensuring that the chemical composition of the final product is highly consistent with the designed ratio. During the casting process, cold casting can cause the alloy liquid to cool too quickly, generating a large temperature gradient that easily leads to casting defects such as cracks, shrinkage cavities, and porosity, and the formation of coarse columnar crystals. Therefore, this application preheats the mold to 200℃~300℃, which can significantly reduce the cooling rate of the alloy liquid, reduce thermal shock, and promote a more stable filling of the mold by the alloy liquid. This is conducive to the formation of equiaxed crystals rather than coarse columnar crystals, improving the uniformity and density of the ingot's structure. Furthermore, demolding at 400℃~500℃ reduces the risk of cracking during subsequent hot working processes such as forging and hot rolling, significantly improving the overall yield from ingot to final strip.

[0028] Preferably, the melting and casting process further includes: electromagnetic stirring of the refined alloy liquid at a frequency of 5Hz to 10Hz for a duration of 30s to 60s. By applying a low-frequency alternating electromagnetic field with a frequency of 5Hz to 10Hz and a duration of 30s to 60s, a controllable electromagnetic force is generated in the molten pool. This ensures a highly uniform distribution of all alloying elements at both the macroscopic and microscopic levels throughout the melt, thus creating conditions for the formation of a uniformly structured ingot during subsequent solidification. More importantly, the tangential force generated by electromagnetic stirring effectively washes away and breaks up nascent dendrites, inhibiting their coarsening and promoting a large number of fine equiaxed crystal nuclei. This not only significantly refines the as-cast grains, creating a synergistic effect with the refining effect of rare earth elements, but also promotes the floating or aggregation of high-density inclusions and low-density oxides, facilitating their subsequent removal. This results in a high-purity, dense, and uniformly composed high-quality ingot.

[0029] In a specific embodiment, the forging process includes the following steps: sawing the riser and bottom plate of the ingot obtained from the melting and casting process, turning the surface until it is smooth and free of oxide scale, heating to 800℃~850℃ and holding for 4h~6h, and then forging it into a slab of (120mm~130mm)×(370mm~390mm)×(4500mm~4600mm); wherein, the pre-forging temperature is controlled not to be lower than 760℃ when exiting the furnace, and the final forging temperature is controlled not to be lower than 650℃ during the forging process. This application completely eliminates defects such as porosity, shrinkage cavities, and oxide scale in the ingot by sawing the riser and bottom plate and turning the surface to a smooth finish. Secondly, holding the slab at 800℃~850℃ for a long time for 4h~6h can make its overall temperature uniform and thorough, which can effectively eliminate dendritic segregation inside the ingot and make the distribution of alloy elements more uniform. During this process, the pre-forging temperature is strictly controlled to be no lower than 760℃, ensuring that the alloy deforms within the optimal thermoplastic range and avoiding excessive resistance and cracking risks caused by excessively low temperatures. At the same time, the final forging temperature is specified to be no lower than 650℃, ensuring that the entire forging process is completed above the material's recrystallization temperature. This allows the work hardening and internal stress generated by plastic deformation to be eliminated in a timely manner through dynamic recrystallization, thereby fully breaking down the coarse cast structure and obtaining a forged slab with a dense internal structure and fine and uniform grains. This effectively avoids microcracks and residual stress that may be caused by low-temperature forging.

[0030] In a specific embodiment, the hot rolling process includes the following steps: heating the forged slab to 730℃~760℃ and holding it at that temperature for 2h~3h, then hot rolling it to 12mm~18mm in 6 passes to obtain a hot-rolled strip; wherein, the rolling speed of the first 3 passes is controlled at 1.2m / s~1.5m / s, and the speed of the last 3 passes is reduced to 0.8m / s~1.0m / s. This application's hot rolling process achieves a perfect combination of efficient deformation and microstructure optimization by controlling the rolling speed in stages. The first 3 passes use a relatively fast rolling speed (1.2m / s~1.5m / s), which can quickly complete the main thickness reduction while ensuring the slab temperature, thus improving production efficiency; the last 3 passes actively reduce the rolling speed (0.8m / s~1.0m / s), extending the residence time of the deformed metal in the high-temperature zone, providing more sufficient conditions for dynamic recrystallization, thereby effectively refining the grains and homogenizing the microstructure, avoiding microstructure inhomogeneity and residual stress caused by excessively fast rolling.

[0031] In a specific embodiment, the solution heat treatment includes the following steps: holding the hot-rolled strip at 800℃~900℃ for 3h~5h, followed by water mist cooling to room temperature and then air cooling; wherein the cooling rate is 80℃ / s~100℃ / s. Holding the hot-rolled strip at 800℃~900℃ for 3h~5h in this application allows alloying elements such as Mn and Ni in the hot-rolled strip to fully dissolve into the copper matrix, forming a supersaturated solid solution, effectively eliminating compositional segregation and internal stress. More importantly, the rapid water mist cooling at a rate of 80℃ / s~100℃ / s after the holding period suppresses the precipitation of coarse equilibrium phases, creating ideal microstructure conditions for subsequent aging treatment or cold working to form fine, dispersed strengthening phases, thereby significantly reducing the material's thermoelectric potential to copper.

[0032] S2. The hot-rolled coil is subjected to milling, rough rolling, first annealing and intermediate and fine rolling to obtain medium and fine rolled strip.

[0033] In a specific implementation, the milling process includes the following steps: performing double-sided milling on the hot-rolled coil after solution heat treatment, with a single-sided milling amount of 0.2mm~0.3mm. By precisely controlling the milling amount, the surface quality and final performance stability of the strip are effectively improved.

[0034] In a specific embodiment, the rough rolling process includes the following steps: performing multi-pass rough rolling to 2.0 mm, controlling the single-pass deformation rate to 15%~25%; wherein, during the rolling process, segmented cooling of the rolls is adopted to control the surface temperature fluctuation of the rolls to ≤5℃. This application achieves efficient microstructure optimization and excellent strip shape control by combining large deformation with precise roll temperature control. Controlling the single-pass large deformation rate of 15%~25% can fully break down the coarse grains remaining after solution treatment, laying the foundation for obtaining a uniform and refined final microstructure. Simultaneously, segmented cooling of the rolls and controlling the surface temperature fluctuation within the range of ≤5℃ ensures that the thermal expansion height of the rolls along the width direction is consistent, thereby effectively avoiding strip shape defects caused by uneven stress and ensuring the stability of the rolling process and the flatness of the strip.

[0035] In a specific implementation, the first annealing includes the following steps: placing the rough-rolled strip in a bell furnace, introducing a mixed protective atmosphere, and holding it at 550℃~620℃ for 3h~5h, followed by cooling and cleaning. After rough rolling, a large number of dislocations and work hardening are generated inside the strip, leading to reduced plasticity and increased internal stress. Holding it at 550℃~620℃ for 3h~5h allows the alloy to recrystallize sufficiently, completely eliminating work hardening, restoring the material's plasticity, and preparing it for subsequent intermediate and finishing rolling.

[0036] In a specific implementation, the intermediate-finish rolling process includes the following steps: multi-pass intermediate-finish rolling to 0.5mm is performed using a four-high mill, controlling the single-pass deformation rate at 10%~20%, and the roll crown at 0.02mm~0.05mm. Controlling the single-pass deformation rate within the range of 10%~20% is gentler than rough rolling, effectively refining the grains and homogenizing the microstructure while gradually reducing the thickness, thus avoiding material cracking or performance deterioration due to excessive deformation. Simultaneously, precisely controlling the roll crown within the minute range of 0.02mm~0.05mm effectively compensates for the bending deformation of the rolls during rolling, ensuring uniform elongation of the strip along its width, thereby producing a 0.5mm strip with excellent shape and uniform thickness.

[0037] S3. The medium-precision rolled strip is subjected to a second annealing, precision rolling, tension leveling, and final annealing to obtain a copper-manganese alloy strip.

[0038] In a specific implementation, the second annealing includes the following steps: the strip after intermediate finishing rolling is fed back into a bell furnace, a mixed protective atmosphere is introduced, and it is held at 450℃~500℃ for 3h~5h, then cooled and cleaned. After intermediate finishing rolling to 0.5mm, work hardening and residual stress accumulate again inside the strip. Annealing at 450℃~500℃ is mainly to eliminate these internal stresses and promote the precipitation of alloying elements in a finer, more dispersed manner, thereby ensuring sufficient plasticity of the material while maximizing and optimizing its key electrical properties such as resistivity and thermoelectric potential.

[0039] In a specific embodiment, the finishing rolling process includes the following steps: finishing rolling to the target thickness using a twelve-roll mill, controlling the single-pass deformation rate at 5%~15%, controlling the front tension at 8kN~12kN and the back tension at 9kN~14kN during rolling, and maintaining a roll diameter difference ≤0.005mm; wherein, the mixed protective atmosphere is nitrogen and hydrogen in a volume ratio of 3:1. This application controls the single-pass deformation rate at a relatively low level of 5%~15%, and combined with precise front and back tension control, effectively stabilizes the rolling process, prevents strip deviation or breakage, and ensures excellent flatness and strip shape.

[0040] In a specific implementation, the tension straightening process includes the following steps: tension straightening is performed on the finished strip after precision rolling, with the elongation controlled at 0.2%~0.6% and the straightening speed at 150m / min~200m / min. Tension straightening of the finished hardened strip can flatten the strip shape and balance stress.

[0041] In a specific embodiment, the finished product annealing process includes the following steps: the strip is fed into a continuous annealing furnace and annealed at 650℃~750℃ and a winding speed of 3m / min. This application uses a continuous annealing furnace, precisely controlling the furnace temperature at 650℃~750℃ and matching it with a winding speed of 3m / min. These optimized process parameters effectively eliminate residual stress in the finished strip to below 50MPa, fundamentally avoiding uneven thermoelectric potential distribution caused by stress concentration. In contrast, if the annealing temperature is below 650℃, the residual stress will remain above 100MPa, causing thermoelectric potential (EMF) fluctuations exceeding 0.05μV / ℃, severely affecting product accuracy. After annealing, the strip is immediately cleaned to thoroughly remove any trace oxidation inclusions that may have formed on the surface at high temperatures, ensuring the finished strip has a bright and clean surface, meeting the appearance and performance requirements of high-end applications.

[0042] Secondly, based on a general inventive concept, this application also provides a copper-manganese alloy strip with ultra-low thermoelectric potential to copper obtained by the above preparation method, wherein the thermoelectric potential to copper of the copper-manganese alloy strip is ≤0.3μV / ℃.

[0043] The technical solutions described above in this application will be explained in detail below with reference to specific embodiments.

[0044] Example 1 This embodiment provides a method for preparing a copper-manganese alloy plate or strip with ultra-low thermoelectric potential to copper, including the following steps: (1) Ingredients The raw materials used are electrolytic copper plates, industrial silicon blocks, electrolytic manganese sheets, high-purity iron blocks, nickel plates, cerium powder and neodymium powder, and are formulated according to the following mass percentage ratio: Mn 11.7%, Ni 2.5%, Ce 0.105%, Nd 1%, Si≤0.25%, Fe 0.3%, with the balance being Cu.

[0045] (2) Vacuum melting and casting Electrolytic copper plates, electrolytic manganese sheets, and nickel plates are first placed in an alumina crucible and then placed into a smelting furnace along with the crucible. The casting mold is then placed into the furnace simultaneously. After the furnace lid is closed, a mechanical pump is used to evacuate the inside of the smelting furnace until the vacuum pressure is ≤0.08MPa. Then, a Roots pump is used to evacuate the furnace until the vacuum degree is ≤10Pa.

[0046] Start the melting process and control the maximum melting power to 60kW; after the alloy liquid is completely melted, add industrial silicon blocks, high-purity iron blocks, cerium powder and neodymium powder, and keep it at the temperature for 30 minutes to refine it, and obtain the alloy liquid.

[0047] The refined alloy liquid was electromagnetically stirred at a frequency of 10 Hz for 30 seconds. It was then poured into a mold preheated to 200°C. After the ingot solidified, it was air-cooled to 400°C along with the mold before being demolded to obtain the ingot.

[0048] (3) Forging The risers and bottom plates of the ingots obtained from sawing and melting are machined until the surface is smooth and free of oxide scale. They are heated to 850℃ and held for 4 hours. They are then forged into 130mm×390mm×4600mm slabs. The temperature before forging is controlled to be no less than 760℃ when the ingots are taken out of the furnace, and the final forging temperature is controlled to be no less than 650℃ during the forging process.

[0049] (4) Hot rolling The forged slab was heated to 760℃ and held for 2 hours, then hot-rolled to 15mm in 6 passes to obtain hot-rolled strip. The rolling speed was controlled at 1.2m / s for the first 3 passes and reduced to 0.8m / s for the last 3 passes. The rolling speed should not be too fast to ensure complete dynamic recrystallization.

[0050] (5) Solution heat treatment The hot-rolled strip obtained by hot rolling was kept at 850℃ for 4 hours. After the heat preservation was completed, it was cooled to room temperature by water mist and then air cooled. The cooling rate of water mist cooling was 80℃ / s.

[0051] (6) Milling The strip after solution heat treatment is milled on both sides with a single-sided milling amount of 0.25mm to ensure that the strip surface is smooth and free of defects.

[0052] (7) Rough rolling The milled strip is subjected to multiple rough rolling processes to a thickness of 2.0 mm, with the single deformation rate controlled at 15%. During the rolling process, the rolls are cooled in sections to control the surface temperature fluctuation of the rolls to ≤5℃.

[0053] (8) First annealing The strip obtained from rough rolling is placed in a bell furnace, a mixed protective atmosphere is introduced, and it is held at 600℃ for 4 hours. After annealing, it is cleaned to remove surface oxide inclusions.

[0054] (9) Medium and fine rolling A four-high rolling mill is used to perform multi-pass intermediate and finishing rolling to a thickness of 0.5 mm, with the single-pass deformation rate controlled at 10% and the roll crown controlled at 0.05 mm.

[0055] (10) Second annealing The strip after medium and fine rolling is sent back into the bell furnace, a mixed protective atmosphere is introduced, and it is held at 450°C for 4 hours. After annealing, it is cleaned to remove surface oxide inclusions.

[0056] (11) Finish rolling The strip is finished to the target thickness using a twelve-roll mill, with a single-pass deformation rate controlled at 10%. During rolling, the pre-tension is controlled at 10 kN and the post-tension at 9 kN, with a roll diameter difference ≤ 0.005 mm. The protective atmosphere is a mixture of nitrogen and hydrogen in a 3:1 volume ratio. The target thickness of the finished product is determined according to customer requirements. The strip thickness is monitored in real-time during rolling, and parameters such as tension and reduction are adjusted as needed to prevent edge breakage.

[0057] (12) Straightening The finished strip is subjected to tension leveling to flatten the strip and balance the stress. The elongation is controlled at 0.2%, and the straightening speed is 150 m / min.

[0058] (13) Finished product annealing It is fed into a continuous annealing furnace and annealed at 700℃ and a winding speed of 3m / min.

[0059] Example 2 The difference between this embodiment and Embodiment 1 is that the mass ratio of Ce to Nd is adjusted to 0.1:1.

[0060] Example 3 The difference between this embodiment and Embodiment 1 is that the mass ratio of Ce to Nd is adjusted to 0.5:1.

[0061] Example 4 The difference between this embodiment and Embodiment 1 is that the mass ratio of Ce to Nd is adjusted to 1.2:1.

[0062] Example 5 The difference between this embodiment and Embodiment 1 is that the mass ratio of Ce to Nd is adjusted to 2:1.

[0063] Comparative Example 1 The difference between this comparative example and Example 1 is that the mass ratio of Ce to Nd is adjusted to 0.05:1.

[0064] Comparative Example 2 The difference between this comparative example and Example 1 is that the mass ratio of Ce to Nd is adjusted to 3:1.

[0065] The EMF data of the copper-manganese alloy strips obtained in Examples 1-6 and Comparative Examples 1-2 are shown in Table 1, where X represents the mass ratio of Ce to Nd. Metallographic photographs of the copper-manganese alloy strips obtained in Example 1 and Comparative Example 2 are shown below. Figure 2-3 As shown.

[0066] Table 1. EMF data of copper-manganese alloy strips in Examples 1-5 and Comparative Examples 1-2

[0067] From Table 1 and Figure 2-3 It can be seen that the copper-manganese alloy strip prepared in the embodiments of this application has fine and uniform grains. Figure 2 The image shows a metallographic photograph of Ce to Nd mass ratio 3:1. It can be seen that the grain distribution is uneven and some grains are coarse. The EMF of the finished product is measured to be 0.37 μV / ℃.

[0068] Example 6 The difference between this embodiment and Embodiment 1 is that the solution heat treatment temperature is adjusted to 800℃.

[0069] Example 7 The difference between this embodiment and Embodiment 1 is that the solution heat treatment temperature is adjusted to 900℃.

[0070] Comparative Example 3 The difference between this comparative example and Example 1 is that the solution heat treatment temperature was adjusted to 700°C.

[0071] Comparative Example 4 The difference between this comparative example and Example 1 is that the solution heat treatment temperature was adjusted to 750°C.

[0072] Comparative Example 5 The difference between this comparative example and Example 1 is that the solution heat treatment temperature was adjusted to 950°C.

[0073] The EMF data of the copper-manganese alloy strips obtained in Examples 1, 6-7 and Comparative Examples 3-5 are shown in Table 2.

[0074] Table 2. EMF data of copper-manganese alloy strips from Examples 1, 6-7, and Comparative Examples 3-5.

[0075] As can be seen from Table 2, different solution heat treatment temperatures affect the EMF value of copper-manganese alloy strips. The solution heat treatment temperature setting of this application avoids the occurrence of poor grain size and uniformity due to insufficient material recrystallization caused by low temperature, and also avoids the occurrence of abnormal material growth caused by high temperature, thereby obtaining strips with good grain size and uniformity and high degree of equiaxation.

[0076] Example 8 The difference between this embodiment and Embodiment 1 is that the following mass percentage ratio is used: Mn 12.3%, Ni 2.7%, Ce 0.2%, Nd 0.6%, Si≤0.25%, Fe 0.5%, with the balance being Cu.

[0077] Example 9 The difference between this embodiment and Embodiment 1 is that the following mass percentage ratio is used: Mn 11.7%, Ni 2.5%, Ce 0.6%, Nd 0.9%, Si≤0.25%, Fe 0.5%, and the balance is Cu.

[0078] Example 10 The difference between this embodiment and Embodiment 1 is that the following mass percentage ratio is used: Mn 12.7%, Ni 2.2%, Ce 0.3%, Nd 1.3%, Si≤0.25%, Fe 0.5%, and the balance is Cu.

[0079] The EMF data of the manganese alloy strips obtained in Examples 8-10 are shown in Table 3.

[0080] Table 3. EMF data of manganese alloy strips obtained in Examples 8-10

[0081] As shown in Table 3, the manganese alloy strip prepared in this application has the advantages of extremely low thermoelectric potential to copper, high thermoelectric potential uniformity, and stable resistivity. It can fully meet the stringent application requirements for material properties in precision resistors, high-end measuring instruments, and other applications. Specifically, from Example 8 to Example 10, as the Ce content fluctuated from 0.2% to 0.6%, the Nd content fluctuated from 0.6% to 1.3%, and the Mn and Ni contents were adjusted accordingly, the EMF value steadily decreased from 0.193 μV / ℃ to 0.143 μV / ℃. This indicates that by adjusting the Ce / Nd ratio and the content of the main alloying elements, the thermoelectric potential of the alloy can be effectively and predictably controlled within an extremely low range.

[0082] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of this application.

[0083] Finally, it should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes the element.

[0084] This application uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for producing a copper-manganese alloy sheet strip having an ultra-low copper thermoelectric potential, characterized by, Includes the following steps: The raw materials are sequentially processed through melting and casting, forging, hot rolling, and solution heat treatment to obtain hot-rolled coils. The hot-rolled coil is subjected to milling, rough rolling, first annealing and medium-precision rolling to obtain medium-precision rolled strip; The medium-precision rolled strip is subjected to a second annealing, precision rolling, tension leveling, and final annealing to obtain a copper-manganese alloy strip. The raw materials include electrolytic copper plates, industrial silicon blocks, electrolytic manganese sheets, high-purity iron blocks, nickel plates, cerium powder, and neodymium powder. The raw materials are formulated by mass percentage as follows: Mn 11.0%~13.0%, Ni 2.0%~3.0%, Ce 0.1%~1%, Nd 0.5%~1.5%, Si≤0.25%, Fe 0.25%~0.5%, with the balance being Cu. The mass ratio of Ce to Nd is 0.07~2:1, which can refine the alloy grains to 5μm~10μm.

2. The preparation method according to claim 1, characterized in that, The casting process includes the following steps: The electrolytic copper plate, electrolytic manganese sheet and nickel plate are placed in a smelting furnace, and a vacuum is drawn to make the vacuum degree in the furnace ≤10Pa; Start the smelting process and control the maximum smelting power to 60kW~70kW; After the alloy liquid is completely melted, add the industrial silicon block, high-purity iron block, cerium powder and neodymium powder, and keep it at the temperature for 30 min to 45 min for refining; The refined alloy liquid is poured into a mold preheated to 200℃~300℃. After the ingot solidifies, it is air-cooled with the mold to 400℃~500℃ and then demolded to obtain the ingot.

3. The preparation method according to claim 2, characterized in that, The process before casting also includes: electromagnetic stirring of the refined alloy liquid, with an electromagnetic stirring frequency of 5Hz~10Hz and a stirring time of 30s~60s.

4. The preparation method according to claim 1, characterized in that, The forging process includes the following steps: sawing off the riser and bottom plate of the ingot obtained from the melting and casting process, turning the surface until it is smooth and free of oxide scale, heating to 800℃~850℃ and holding at that temperature for 4h~6h, and then forging it into a slab of (120mm~130mm)×(370mm~390mm)×(4500mm~4600mm); wherein... When exiting the furnace, the pre-forging temperature should be controlled to be no less than 760℃, and the final forging temperature should be controlled to be no less than 650℃ during the forging process.

5. The preparation method according to claim 1, characterized in that, The hot rolling process includes the following steps: heating the slab obtained from the forging process to 730℃~760℃ and holding it at that temperature for 2h~3h, and hot rolling it to 12mm~18mm in 6 passes to obtain hot-rolled strip; wherein, the rolling speed of the first 3 passes is controlled at 1.2m / s~1.5m / s, and the speed of the last 3 passes is reduced to 0.8m / s~1.0m / s.

6. The preparation method according to claim 1, characterized in that, The solution heat treatment includes the following steps: holding the hot-rolled strip obtained by hot rolling at 800℃~900℃ for 3h~5h, and after the holding is completed, cooling it to room temperature with water mist and then air cooling; wherein, the cooling rate is 80℃ / s~100℃ / s.

7. The preparation method according to claim 1, characterized in that, The milling and rough rolling processes include: performing double-sided milling on the hot-rolled coil obtained by solution heat treatment, with a single-sided milling amount of 0.2mm~0.3mm; then performing multiple passes of rough rolling to 2.0mm, controlling the single-pass deformation rate to 15%~25%; wherein, during the rolling process, the rolls are cooled in sections to control the surface temperature fluctuation of the rolls to ≤5℃.

8. The preparation method according to claim 1, characterized in that, The first annealing and intermediate finishing rolling processes include: The strip obtained from the rough rolling process is placed in a bell furnace, a mixed protective atmosphere is introduced, and it is kept at 550℃~620℃ for 3h~5h. After cooling, it is cleaned. The mill is made using a four-high mill for multiple passes of intermediate and finishing rolling to 0.5 mm, with the single-pass deformation rate controlled at 10%~20% and the roll crown controlled at 0.02 mm~0.05 mm. The second annealing and finishing rolling process includes: feeding the medium-finished strip obtained from the medium-finishing rolling process back into the bell furnace, introducing a mixed protective atmosphere, holding it at 450℃~500℃ for 3h~5h, and cleaning it after cooling. The target thickness is achieved by using a twelve-roll mill, with the deformation rate controlled at 5% to 15% per pass. During rolling, the front tension is controlled at 8kN to 12kN and the back tension at 9kN to 14kN, and the roll diameter difference is ≤0.005mm. The mixed protective atmosphere is nitrogen and hydrogen in a volume ratio of 3:

1.

9. The preparation method according to claim 1, characterized in that, The tension straightening process and the finished product annealing process include: The strip after precision rolling is subjected to tension straightening treatment, with the elongation controlled at 0.2%~0.6% and the straightening speed at 150m / min~200m / min; It is fed into a continuous annealing furnace and annealed at 650℃~750℃ and a winding speed of 3m / min.

10. A copper-manganese alloy strip with ultra-low thermoelectric potential to copper, obtained by the preparation method according to any one of claims 1-9, characterized in that, The thermoelectric potential of the copper-manganese alloy strip to copper is ≤0.3μV / ℃.

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