Preparation method of nickel-copper composite board for commemorative coins

Abstract

The invention provides a preparation method of a nickel-copper composite board for commemorative coins, which comprises the following steps: material selection: acquiring a nickel strip, a copper strip and a copper foil strip as basic materials, and carrying out surface treatment on the nickel strip and the copper strip to meet a preset roughness requirement; carrying out rolling and annealing treatment on the copper foil strip; compounding: combining the nickel strip, the copper strip and the copper foil strip according to a preset composite structure to form a composite board; rolling: processing the composite board through multi-pass rolling to form a target size; and annealing: carrying out annealing treatment and detection on the composite board. The copper foil strip is annealed in a hydrogen reducing atmosphere, so that the ductility of the copper foil strip is improved; single rolling is carried out, turning is carried out, and uniform stress distribution is ensured; a continuous annealing furnace is used for uniform-temperature annealing, and residual stress is reduced; high-sensitivity ultrasonic waves are adopted to detect the internal quality, and surface defects are strictly controlled. Through the innovative processes, the interface bonding strength, the internal structure uniformity and the surface quality of the nickel-copper composite board are remarkably improved, high-quality raw materials are provided for production of high-quality commemorative coins, and important practical value is achieved.

Description

Technical Field

[0001] This invention patent belongs to the technical field of high-quality metal composite plate preparation for commemorative coins, and relates to an advanced preparation method for nickel-copper composite plates. Background Technology

[0002] Commemorative coins are special currencies meticulously designed and issued in limited quantities to commemorate specific events, figures, or themes, possessing artistic, historical, investment, and collectible value. Currently, they have become an important choice for collectors and investors. The diversity of materials, designs, types, and maintenance methods gives commemorative coins a unique collectible value in the fields of art, history, and investment. With the improvement of people's living standards, the market demand for commemorative coins is expected to further increase in the future. Nickel is resistant to oxidation and corrosion, possessing a bright and beautiful metallic luster, effectively preventing commemorative coins from oxidizing or discoloring in daily environments and maintaining their long-lasting luster; copper enhances strength and ductility. Nickel-copper composite plates exhibit excellent performance in corrosion resistance, mechanical properties, appearance, cost, processing performance, and conductivity. On the one hand, the composite structure reduces the amount of relatively expensive nickel used, lowering costs while maintaining a high-quality appearance; on the other hand, nickel-copper composite plates are easy to process, such as stamping, making them suitable for mass production. Furthermore, the composite structure reduces dependence on a single metal, helping to reduce resource consumption. Therefore, nickel-copper composite plates are very suitable for the manufacture and production of commemorative coins.

[0003] However, commemorative coins require high-quality nickel strips. Firstly, from a usability perspective, the strip surface must be flat, free from defects such as scabs, cracks, inclusions, and folds. These defects not only damage the strip's quality but also often reduce product performance. Secondly, high internal quality is required for the nickel strip; internal pores, cracks, and inclusions significantly impact the product's appearance and lifespan. Furthermore, the interfacial bonding between the nickel and copper strips is a significant technical challenge. A weak interfacial bond allows oxygen atoms to react chemically with easily oxidized copper, leading to discoloration and delamination at the interface, severely affecting product quality.

[0004] Therefore, preparing nickel-copper composite plates with strong interfacial bonding and excellent metallurgical quality is a very important step in the production of commemorative coins. Summary of the Invention

[0005] This invention addresses the problems of low interfacial bonding strength and surface oxidation and peeling after a certain period of storage in nickel-copper composite plates used for commemorative coins. It proposes a process to improve the interfacial bonding performance of nickel-copper composite plates and enhance the quality of the final product. The process involves first selecting and surface-treating nickel strips, copper strips, and copper foils, then laminating them together, followed by precision rolling, and finally annealing for stress relief and inspection.

[0006] The technical solution of this invention is: This invention provides a method for preparing a nickel-copper composite plate for commemorative coins, the method comprising the following steps: (1) Material selection: Nickel strip, copper strip and copper foil strip are used as base materials. The nickel strip and copper strip are subjected to surface roughening treatment. The copper foil strip is subjected to rolling and annealing treatment. (2) Composite: The nickel strip, copper strip and copper foil strip are combined to form a composite plate according to the composite structure of "nickel strip-copper foil-copper strip-copper foil-nickel strip"; (3) Rolling: The composite material is processed by rolling; (4) Annealing: The composite board is annealed.

[0007] Furthermore, in step (1), the nickel strip thickness is 0.2mm-0.5mm; the copper foil strip thickness is 30μm-50μm; and the copper strip thickness is 1.5mm-2mm.

[0008] Further, in step (1), after the nickel strip and copper strip are surface roughened, they are cleaned to remove oil and impurities, dried and then rolled into rolls for later use. After the treatment, the surface roughness Ra of the nickel strip is ≥3.2μm and the surface roughness Ra of the copper strip is ≥3.2μm; wherein, the nickel content in the nickel strip is ≥98% and the copper content in the copper strip is ≥95%.

[0009] Further, in step (1), the rolling and annealing of the copper foil strip includes: The copper foil strip is rolled and then annealed in a continuous annealing furnace under a hydrogen reducing atmosphere. The annealing temperature and holding time are controlled to reduce the internal stress of the copper foil strip. The surface of the annealed copper foil strip is then degreased and cleaned.

[0010] Furthermore, in step (1), the temperature control accuracy of the annealing furnace reaches ±5℃, the annealing temperature is 550℃-600℃, and the holding time is 5min-10min.

[0011] Furthermore, in step (2), a layered structure of nickel strip-copper foil-copper strip-copper foil-nickel strip is used for combination. The copper foil strip is used as an intermediate layer, and the contact interface between the nickel strip and the copper strip is adjusted to form a composite plate structure to be rolled.

[0012] Furthermore, step (3) specifically includes: The composite sheet is processed by a multi-pass rolling process, using a single-sheet rolling method, controlling the deformation of each rolling pass to be 25%-35%, and the rolling speed to be 35m / min-45m / min, to ensure uniform stress distribution inside the composite sheet. After each rolling pass, the composite sheet is flipped and turned over before the next rolling pass. This rolling process is repeated until the composite sheet reaches the target size and thickness.

[0013] Furthermore, step (4) specifically includes: The composite board was annealed in a hydrogen atmosphere using a continuous annealing furnace with a temperature control accuracy of ±5℃. The annealing temperature was controlled at 600℃-700℃, and the holding time was 15min-20min.

[0014] Furthermore, it also includes step (5): using the contact method to perform ultrasonic testing on the interior of the composite board, with a testing sensitivity of 3.2 mm, to identify whether there are internal defects such as cracks, folds and inclusions.

[0015] Furthermore, after step (5), the method further includes: visually inspecting the surface of the composite board to determine whether there are surface defects, including pits and scratches. If the internal and surface quality tests are passed, the product is deemed to be qualified.

[0016] The beneficial effects of this invention are: The nickel-copper composite sheet for commemorative coins prepared in this invention adopts a gradient functional composite structure of nickel and copper strips. The surface roughness of the nickel and copper strips is designed, and a layer of copper foil with good plasticity and a thickness matching the roughness of the nickel and copper strips is sandwiched between them. After rolling, a tight metallurgical bond is achieved at the contact surface of the nickel and copper strips. A crucial process for quality control of internal defects in the nickel strip is high-sensitivity ultrasonic testing. Ultrasonic testing can detect internal defects in the sheet material, especially planar defects such as cracks and delamination, demonstrating strong reliability and detection capability.

[0017] The composite sheet prepared by this invention is manufactured using a cold rolling process. Cold rolling is carried out at room temperature, which avoids surface oxidation and results in a sheet with good surface quality. By precisely controlling the rolling speed and deformation, high-quality nickel-copper composite sheets can be mass-produced.

[0018] This invention discloses a method for preparing high-quality nickel-copper composite plates for commemorative coin production. By precisely controlling key aspects such as raw material selection, composite structure design, heat treatment process, precision rolling, and quality inspection, it solves problems such as insufficient interfacial bonding strength and uneven internal stress distribution in traditional preparation methods.

[0019] This invention employs hydrogen-reducing atmosphere annealing to improve the ductility of copper foil strips; single-sheet rolling and flipping ensure uniform stress distribution; continuous annealing furnace for uniform temperature annealing reduces residual stress; and high-sensitivity ultrasonic testing is used to strictly control surface defects. Through these innovative processes, this invention significantly improves the interfacial bonding strength, internal structure uniformity, and surface quality of nickel-copper composite plates, providing high-quality raw materials for the production of high-quality commemorative coins and possessing significant practical value.

[0020] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0021] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the invention.

[0022] Figure 1 A flowchart of the method for preparing the nickel-copper composite plate for commemorative coins according to the present invention is shown. Detailed Implementation

[0023] Preferred embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0024] like Figure 1 As shown, the present invention provides a method for preparing a nickel-copper composite plate for commemorative coins, comprising the following steps: (1) Obtain the raw materials required for the preparation of nickel-copper composite plates for commemorative coins, including nickel strip, copper strip and copper foil strip, wherein the thickness of the nickel strip is 0.2mm-0.5mm; the thickness of the copper foil is 30μm-50μm; and the thickness of the copper strip is 1.5mm-2mm.

[0025] The surface roughness of the nickel strip and copper strip must meet the preset requirements. After surface cleaning and drying, they are ready for use. The surface roughness of the nickel strip is Ra≥3.2μm, and the surface roughness of the copper strip is Ra≥3.2μm. The nickel content in the chemical composition of the nickel strip is ≥98%, and the copper content in the copper strip is ≥95%.

[0026] The copper foil strip is rolled to a preset thickness and then heat-treated in a continuous annealing furnace under a hydrogen reducing atmosphere. The annealing temperature and holding time are controlled to reduce the internal stress of the copper foil strip. The annealing process parameters are 550℃-600℃ × holding time of 5min-10min to obtain a copper foil strip with improved ductility. The surface of the treated copper foil strip needs to be degreased and cleaned.

[0027] (2) According to the preset composite structure design, construct a multilayer composite structure of nickel strip-copper foil-copper strip-copper foil-nickel strip. The thickness of each layer of the composite structure must meet the predetermined range to ensure the matching of the interface contact surface and provide a basis for subsequent rolling.

[0028] (3) The composite structure is rolled in multiple passes using a precision rolling mill. The deformation amount and rolling rate of each pass are controlled. The rolling process is carried out in single-sheet rolling mode. The deformation amount of each pass is controlled within the range of 25% to 35%, and the rolling rate is controlled within the range of 35m / min to 45m / min. It is required that after each pass of rolling, the composite plate is flipped and turned over in the next pass to obtain a primary rolled plate with uniform stress distribution.

[0029] (4) The primary rolled plate is subjected to uniform annealing in a continuous annealing furnace under hydrogen atmosphere. The annealing temperature and holding time are precisely controlled to reduce the residual stress of the primary rolled plate and obtain the annealed composite plate. The temperature control accuracy reaches ±5℃, the annealing temperature is controlled at 600℃-700℃, and the holding time is 15min-20min.

[0030] (5) For the annealed composite plate, a high-sensitivity ultrasonic test is performed using the contact method to check the metallurgical quality inside the composite plate, determine whether there are cracks or slag inclusions, and obtain a qualified plate.

[0031] (6) Based on the qualified plate, conduct a surface quality inspection to confirm that there are no visible pits or scratches on the surface of the plate, and obtain a nickel-copper composite plate that meets the quality standards; by sorting and packaging the nickel-copper composite plate that meets the quality standards, the final product preparation process is completed. The final product is used for the production of commemorative coins and meets the high-quality requirements. Example 1

[0032] The composite sheet structure is designed as nickel strip-copper foil-copper strip-copper foil-nickel strip, where the nickel strip thickness is 0.2 mm, the copper foil thickness is 30 μm, and the copper strip thickness is 1.5 mm. The surface roughness Ra of the nickel strip is 4 μm, and the surface roughness Ra of the copper strip is 5 μm. The nickel content in the metallic nickel strip reaches 98.5% (wt), with the remainder being alloying elements and trace elements; the copper content in the metallic copper strip is 96%, with the remainder being alloying elements and trace elements.

[0033] The nickel and copper strips were cleaned to remove oil and dirt, dried, and then rolled into rolls for later use. The copper foil used was 30μm thick. After rolling, the copper foil was annealed in a continuous annealing furnace in a hydrogen reducing atmosphere. The temperature control accuracy of the annealing furnace reached ±5℃, and the annealing process parameters were 600℃ × 5min. The surface of the rolled copper foil was then degreased and cleaned.

[0034] The composite structure, combining nickel strip, copper foil, copper strip, copper foil, and nickel strip, is employed. This composite rolling process utilizes a mill with precisely controlled deformation, employing single-sheet rolling to avoid increased internal stress due to curling. The deformation per pass is controlled within 25%, and the rolling speed is maintained at 35 m / min. Crucially, after each pass, the composite sheet is flipped and rotated for the next pass to ensure a more uniform distribution of internal stress. Through multiple rolling passes, the composite sheet is rolled to the required dimensions and thickness for the product.

[0035] The composite plates are annealed in a hydrogen atmosphere using a continuous annealing furnace with a temperature control accuracy of ±5℃. The annealing process parameters are 600℃ × holding time of 20min. After rolling, the nickel-copper composite plates are ultrasonically tested for internal metallurgical quality using a contact method with a sensitivity of 3.2mm. This process avoids residual cracks, folds, slag inclusions, and other defects. The surface quality of the rolled nickel-copper composite plates is inspected, requiring no visually visible pits, scratches, or other defects. Once the products pass inspection, they are packaged and stored. Example 2

[0036] The composite sheet structure is designed as nickel strip-copper foil-copper strip-copper foil-nickel strip, where the nickel strip thickness is 0.5 mm, the copper foil thickness is 50 μm, and the copper strip thickness is 2 mm. The surface roughness Ra of the nickel strip is 5.5 μm, and the surface roughness Ra of the copper strip is 6 μm. The nickel content in the metallic nickel strip reaches 99%, with the remainder being alloying elements and trace elements; the copper content in the metallic copper strip is 97%, with the remainder being alloying elements and trace elements.

[0037] The nickel and copper strips were cleaned to remove oil and dirt, dried, and then rolled into rolls for later use. The copper foil used was 50μm thick. After rolling, the copper foil was annealed in a continuous annealing furnace in a hydrogen reducing atmosphere. The temperature control accuracy of the annealing furnace reached ±5℃, and the annealing process parameters were 550℃ × 10min. The surface of the rolled copper foil was then degreased and cleaned.

[0038] The composite structure, combining nickel strip, copper foil, copper strip, copper foil, and nickel strip, is employed. This composite rolling process utilizes a mill with precisely controlled deformation, employing single-sheet rolling to avoid increased internal stress due to curling. The deformation per pass is controlled within 30%, and the rolling speed is maintained at 40 m / min. Crucially, after each pass, the composite sheet is flipped and rotated for the next pass to ensure a more uniform distribution of internal stress. Through multiple rolling passes, the composite sheet is rolled to the required dimensions and thickness for the product.

[0039] The composite plates are annealed in a hydrogen atmosphere using a continuous annealing furnace with a temperature control accuracy of ±5℃. The annealing process parameters are 700℃ × holding time of 15min. After rolling, the nickel-copper composite plates are ultrasonically tested for internal metallurgical quality using a contact method with a sensitivity of 3.2mm. The surface quality of the rolled nickel-copper composite plates is visually inspected, requiring the absence of surface pits, scratches, and other defects. Once the products pass inspection, they are packaged and stored.

[0040] Comparative Example 1: The traditional method involves the following steps: first, selecting nickel strip and copper strip; then, stacking the nickel strip and copper strip and rolling them together; and finally, annealing and inspecting the composite strip.

[0041] Compared with traditional methods, the product prepared by the method of the present invention achieves the effect of strong interfacial bonding and excellent metallurgical quality, and solves the problems of insufficient interfacial bonding strength and uneven internal stress distribution in traditional preparation methods.

[0042]

[0043] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for preparing a nickel-copper composite plate for commemorative coins, characterized in that, The method includes the following steps: (1) Material selection: Nickel strip, copper strip and copper foil strip are used as base materials. The nickel strip and copper strip are subjected to surface roughening treatment. The copper foil strip is subjected to rolling and annealing treatment. (2) Composite: The nickel strip, copper strip and copper foil strip are combined to form a composite plate according to the composite structure of "nickel strip-copper foil-copper strip-copper foil-nickel strip"; (3) Rolling: The composite material is processed by rolling; (4) Annealing: The composite board is annealed.

2. The method for preparing nickel-copper composite plates for commemorative coins as described in claim 1, characterized in that... In step (1), the nickel strip thickness is 0.2mm-0.5mm; the copper foil strip thickness is 30μm-50μm; and the copper strip thickness is 1.5mm-2mm.

3. The method for preparing nickel-copper composite plates for commemorative coins as described in claim 1, characterized in that... In step (1), after surface roughness treatment of the nickel strip and copper strip, they are cleaned to remove oil and impurities, dried and then rolled into rolls for later use. After treatment, the surface roughness Ra of the nickel strip is ≥3.2μm and the surface roughness Ra of the copper strip is ≥3.2μm. The nickel content in the nickel strip is ≥98% and the copper content in the copper strip is ≥95%.

4. The method for preparing nickel-copper composite plates for commemorative coins as described in claim 1, characterized in that... In step (1), the rolling and annealing of the copper foil strip includes: The copper foil strip is rolled and then annealed in a continuous annealing furnace under a hydrogen reducing atmosphere. The annealing temperature and holding time are controlled to reduce the internal stress of the copper foil strip. The surface of the annealed copper foil strip is then degreased and cleaned.

5. The method for preparing nickel-copper composite plates for commemorative coins as described in claim 4, characterized in that... In step (1), the temperature control accuracy of the annealing furnace reaches ±5℃, the annealing temperature is 550℃-600℃, and the holding time is 5min-10min.

6. The method for preparing nickel-copper composite plates for commemorative coins as described in claim 1, characterized in that... In step (2), a layered structure of nickel strip-copper foil-copper strip-copper foil-nickel strip is used for combination. The copper foil strip is used as an intermediate layer, and the contact interface between the nickel strip and the copper strip is adjusted to form a composite plate structure to be rolled.

7. The method for preparing nickel-copper composite plates for commemorative coins as described in claim 1, characterized in that... The specific steps (3) are as follows: The composite sheet is processed by a multi-pass rolling process, using a single-sheet rolling method, controlling the deformation of each rolling pass to be 25%-35%, and the rolling speed to be 35m / min-45m / min, to ensure uniform stress distribution inside the composite sheet. After each rolling pass, the composite sheet is flipped and turned over before the next rolling pass. This rolling process is repeated until the composite sheet reaches the target size and thickness.

8. The method for preparing nickel-copper composite plates for commemorative coins as described in claim 1, characterized in that... The specific steps (4) are as follows: The composite board was annealed in a hydrogen atmosphere using a continuous annealing furnace with a temperature control accuracy of ±5℃. The annealing temperature was controlled at 600℃-700℃, and the holding time was 15min-20min.

9. The method for preparing nickel-copper composite plates for commemorative coins as described in claim 1, characterized in that... It also includes step (5): using the contact method to perform ultrasonic testing on the interior of the composite board, with a testing sensitivity of 3.2 mm, to identify whether there are cracks, folds and inclusions inside.

10. The method for preparing nickel-copper composite plates for commemorative coins as described in claim 9, characterized in that... Step (5) is followed by visual inspection of the surface of the composite board to determine whether there are surface defects, including pits and scratches. If the internal and surface quality tests are passed, the product is deemed to be qualified.

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