A method for producing pure nickel plates by thin strip continuous casting

Abstract

This invention belongs to the field of non-ferrous metallurgical technology, and particularly relates to a short-process preparation technology for pure nickel strip. This invention uses a concave crystallizing roll with a concave diameter of 0.2-0.3 mm to continuously cast molten nickel obtained from vacuum smelting. After cooling to the hot rolling temperature, it is hot rolled, then cooled to room temperature and cold rolled again, and finally coiled to obtain the product. This invention directly produces as-cast thin strip by pouring molten nickel directly onto a crystallizing roll with a special structure. Combined with subsequent processes, it achieves high-quality pure nickel thin strip in an extremely short process.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metallurgical technology, and particularly relates to a short-process preparation technology for pure nickel strip. Background Technology

[0002] Thin strip continuous casting includes single-strip thin strip continuous casting, double-strip thin strip continuous casting, single-roll thin strip continuous casting, and twin-roll thin strip continuous casting. Among them, twin-roll thin strip continuous casting technology is considered the most revolutionary cutting-edge technology in the steel metallurgy field of the 21st century. In the twin-roll thin strip casting process, molten steel is directly cast into a thin strip with a thickness of about 1-5mm on a water-cooled copper crystallizing roll. The molten steel produces a sub-rapid solidification effect, while eliminating the reheating and numerous rolling processes required in traditional continuous casting, thus realizing integrated casting and rolling production. Because twin-roll thin strip continuous casting technology can eliminate the hot rolling process of the slab or require only a few hot rolling processes, compared with traditional continuous casting and thin slab continuous casting and rolling technologies, its production line is greatly shortened, and the corresponding equipment investment, space occupation, and energy consumption are significantly reduced, greatly shortening the steel product production cycle. Therefore, in recent years, twin-roll thin strip continuous casting technology has become an advanced casting technology that major steel companies around the world are vying to develop. Since the 1980s, major thin-strip continuous casting projects have included the Nippon Steel-Mitsubishi Heavy Industries stainless steel thin-strip continuous casting project, the EUROSTRIP thin-strip continuous casting project jointly developed by the European Union, the CASTRIP thin-strip continuous casting project developed by NUCOR Steel in the United States, and the thin-strip continuous casting project developed by POSCO Steel in South Korea. Domestically, Baosteel Group and Jingye Group have also built high-level twin-roll thin-strip continuous casting industrial lines and conducted industrial-scale pilot production practices, achieving significant progress in industrialization research. Looking at the development history of steel thin-strip continuous casting technology, Europe, Japan, and the United States established pilot lines for thin-strip continuous casting early on and achieved industrial-scale production, mainly for the production of carbon steel, stainless steel, and silicon steel thin strips. However, currently only NUCOR Steel in the United States has commercialized thin-strip continuous casting technology and achieved good economic benefits, but mainly for the production of low-carbon steel and low-carbon microalloyed steel, and has sold the CASTRIP technology to Tyasa Steel in Mexico and Shagang Group in China.

[0003] With the global trend towards low-carbon development in the energy industry, my country has proactively proposed a "dual-carbon" goal. This marks a historic turning point in green development aimed at reducing carbon emissions and promoting the transformation and upgrading of my country's energy and related industries, thereby achieving long-term, healthy, and sustainable economic development. Against this backdrop, twin-roll thin strip technology, with its advantages of short process and low energy consumption, not only aligns with national development strategies but also meets the energy industry's requirements for energy conservation and cost reduction. Therefore, it has attracted the attention of relevant scientific and technological workers and is considered a major development direction for near-net-shape continuous casting production. However, existing thin strip technologies are mostly used to produce strips of low-carbon steel, low-carbon microalloyed steel, and high-carbon steel.

[0004] Nickel, as a commonly used non-ferrous metal, is often used as an alloying element to improve the corrosion resistance, oxidation resistance, hardness, strength, and toughness of alloy materials. In addition, high-purity nickel is widely used in chemical, marine equipment, nuclear energy, and battery industries due to its excellent corrosion resistance, machinability, and electromagnetic properties. With the development of industrial society, the demand for high-purity nickel is increasing. Nowadays, the production of high-purity nickel strip is mostly carried out by traditional die casting and rolling. That is, qualified nickel molten metal is produced by vacuum melting, die casting under vacuum, and then hot rolling and repeated cold rolling and annealing are performed to produce the final pure nickel strip. However, shrinkage cavities and porosity are very easy to occur in the die casting process, which seriously reduces the yield of ingots and easily causes problems such as unqualified slab quality (Yang Zhe, Yang Han, Cheng Wei. Pure Nickel Smelting Process Method [J]. Metal World, 2021(01):36-39.). Furthermore, traditional production processes often require repeated heating and rolling of ingots, involving numerous steps, resulting in significant heat waste and extremely low production efficiency, as illustrated by patent 202011596924.4. Against this backdrop, the rapid, energy-efficient, and economical production of pure nickel plates is one of the main development directions for the industry. Twin-roll strip casting, as a short-process production technology, has become a major trend in future metallurgical production. Moreover, given that existing industrialized steel strip production technology is larger in scale and more complex in equipment compared to non-ferrous metals, the industrialization of twin-roll strip casting in the non-ferrous metals production sector is highly feasible. To date, industrialized twin-roll strip casting production of non-ferrous metals such as aluminum alloys, copper alloys, and high-nickel alloys has been achieved globally, but the industrialized production of pure nickel twin-roll strip and related basic research have not been reported.

[0005] For nickel alloys, most production methods employ vacuum melting followed by ingot casting. This method, due to its slow cooling rate, provides ample time for the diffusion of internal impurities, leading to severe grain boundary and intragranular oxidation in the ingot. This results in the formation of large-area oxide scale, reducing alloy yield (see Song Hongyu et al., "Study on the Microstructure, Structure and Mechanical Properties of Thin-Strip Continuous Casting Invar Alloy"). To avoid this, Kawasaki Steel Corporation of Japan utilizes twin-roll thin-strip technology to produce nickel-based alloys. While the final product has sufficient machinability, the overall thickness of the cast strip fluctuates significantly; furthermore, due to the low thermal conductivity of nickel-based alloys, voids often exist within the cast strip. Additionally, during the production of nickel-iron alloys using twin-roll thin-strip technology, the extremely rapid cooling rate makes the cast strip surface highly susceptible to cracking, thus reducing product yield (see Lian Qifang et al., "Continuous Casting Thin Strip of Iron-Nickel Alloy and Its Manufacturing").

[0006] Preliminary investigations revealed significant problems with directly producing pure nickel using existing thin-strip continuous casting technology. The resulting nickel plates exhibited severe surface quality issues, including numerous pits and large cracks. Therefore, while the twin-roll thin-strip production process has some applicability to pure nickel strip production, further optimization of continuous casting process parameters and the structure of key components is needed to achieve continuous production of high-quality pure nickel strips. Research indicates that there are currently few records of using concave crystallizing rolls to prepare pure nickel strips. Summary of the Invention

[0007] To address the problems existing in the prior art, the present invention aims to provide a method for producing pure nickel strip. This method involves directly pouring molten nickel onto a crystallizing roll with a unique structure (such as a concave crystallizing roll) that has rolling capabilities. The concave crystallizing roll not only provides strong cooling to achieve sub-rapid solidification of the molten nickel, thereby increasing the austenite nucleation rate within the nickel plate and ultimately improving the product's mechanical properties, but also provides space for bending and twisting of the strip as it passes through the roll gap, effectively reducing stress and surface texture and segregation. Furthermore, the concave crystallizing roll increases the contact area between the strip and the crystallizing roll, thereby improving heat transfer efficiency and further enhancing the uniformity of strip crystallization. Moreover, the strip produced by the concave crystallizing roll has a certain curvature, which reduces stress concentration and friction between the roll and the strip surface during subsequent rolling, thus reducing cracks and depressions and improving the surface quality of the strip.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] This invention discloses a short-process preparation technology for pure nickel strip, which includes the following steps:

[0010] 1) Nickel smelting

[0011] High-purity nickel molten metal was smelted in a vacuum environment using an induction furnace. The chemical composition of the molten nickel molten metal obtained by smelting was as follows: C: ≤20.0ppm, Si: ≤10ppm, Mn: ≤12ppm, S: ≤2.0ppm, Mg: ≤3.0ppm, Al: ≤7ppm, Ti: ≤25ppm, with the balance being Ni and unavoidable impurities.

[0012] 2) Thin strip casting

[0013] Molten nickel in a vacuum induction furnace is poured into a buffer ladle through a long nozzle and flows into the crystallizing roll pool through a branch nozzle under the buffer ladle. Finally, pure nickel as-cast strip is cast using a twin-roll thin strip casting machine. The crystallizing roll used in the twin-roll thin strip casting machine is a concave crystallizing roll. The concave crystallizing roll has a spindle structure that is large at both ends and small in the middle. It is defined as follows: when the concave crystallizing roll is upright, the top and bottom surfaces are composed of two circles with equal radii R. The height from the bottom surface to the top surface is H. The radius of the circle in the plane where 1 / 2H of the concave crystallizing roll is located is R1. R-R1 = 0.2-0.3 mm, preferably 0.2-0.22 mm. The radius of the circle constituting the concave crystallizing roll decreases linearly from the bottom surface upwards to 1 / 2H. From the bottom surface upwards, after passing 1 / 2H, the radius of the circle constituting the concave crystallizing roll increases linearly towards the top surface. The temperature of the molten nickel is 1500-1550℃; the temperature at which the molten nickel enters the crystallizing roller pool is 1490-1530℃. The average distance between the two rollers is 2.0mm-5.0mm.

[0014] The temperature at which pure nickel as-cast strip is cast using a twin-roll continuous casting machine is 1100-1200℃.

[0015] Preferably, the concave crystallizing roller has a nickel-molybdenum alloy coating or a nickel-chromium alloy coating on its surface; the coating thickness is 20-60 μm, which is further preferred. The nickel-molybdenum alloy coating contains 50-70% nickel, preferably 60-65%, with the balance being molybdenum. The nickel-chromium alloy coating contains 50-80% nickel, preferably 60-70%, with the balance being chromium.

[0016] This invention discloses a short-process preparation technology for pure nickel strip. After casting pure nickel as-cast strip using a twin-roll continuous casting machine, it can also be hot-rolled; the hot rolling process is as follows:

[0017] After exiting the crystallizing roll, the as-cast strip is rapidly and uniformly cooled to 850-1000℃, with a cooling rate of not less than 50℃ / s. The as-cast strip is then hot-rolled to 1.0-3.0mm in one pass at 850-1000℃ to obtain a hot-rolled strip. The temperature of the hot-rolled strip is 800-900℃.

[0018] This invention discloses a short-process preparation technology for pure nickel strip. The hot-rolled strip is continuously cooled to room temperature, and then continuously cold-rolled for 3 to 6 passes to roll it into a strip with a thickness of 0.3-0.8 mm; thus obtaining a cold-rolled strip.

[0019] This invention provides a short-process preparation technology for pure nickel strip. Cold-rolled thin strip The final nickel coil is obtained after winding at room temperature.

[0020] Furthermore, in step 1), the smelting method is vacuum induction melting (VIM) or double vacuum melting, namely vacuum induction melting (VIM) plus vacuum self-consumption (VAR), and further refining is used to control the composition of the nickel molten metal.

[0021] Furthermore, in step 2), after the nickel smelting is completed, the vacuum must first be broken, and then an inert gas is blown in to prevent the nickel smelting from oxidizing.

[0022] Furthermore, in step 2), the superheat of the nickel solution is 50–100°C.

[0023] Furthermore, in step 2), the thickness of the cast strip is 2.0-5.0 mm.

[0024] Furthermore, in step 2), the casting speed of the twin-roll thin strip continuous casting machine is 60-100 m / min.

[0025] Furthermore, after the cast thin strip exits the crystallizing roll, it is first cooled to 850-1000℃ by spraying inert gas through a high-pressure air-cooled nozzle at a cooling rate of 50-100℃ / s. The nozzle gas is nitrogen, helium, or argon. Then, it is immediately followed by online hot rolling with a hot rolling reduction rate of no more than 50%.

[0026] Furthermore, the hot-rolled strip is cooled to room temperature using high-pressure water nozzles at a rate of 60–150°C / s; then it undergoes 3–6 passes of cold rolling, with a total cold rolling reduction of no more than 80%.

[0027] Furthermore, the thin strip curling is carried out at room temperature.

[0028] The technical concept of this invention is as follows:

[0029] 1) By utilizing the commonalities in production and processing between nickel plates and steel plates, the steel production process is redesigned and optimized to achieve short-process production of pure nickel cast strip.

[0030] 2) The nickel melt achieves sub-rapid solidification under the strong cooling of the concave crystallizing roll. The concave crystallizing roll can effectively increase the contact area between the cast strip and the crystallizing roll, thereby improving the heat transfer efficiency and thus improving the uniformity of the cast strip crystallization. After exiting the crystallizing roll, the thin strip is cooled rapidly and uniformly by high-pressure inert gas and high-pressure water cooling, which can suppress the growth and coarsening of austenite grains in the high-temperature cast thin strip. The strength, plasticity and toughness of the pure nickel thin strip are improved by using the fine grain strengthening mechanism.

[0031] 3) Concave crystallizing rolls refer to rolls that are concave in the diameter direction and have a spindle structure that is large at both ends and small in the middle. During use, this type of crystallizing roll can provide a certain space for the bending and twisting of the cast strip, so that the cast strip has a certain curvature, which makes it easier to obtain thin strip products with better quality in the subsequent rolling process.

[0032] 4) Using concave crystallizing rolls instead of flat crystallizing rolls can reduce stress concentration at the roll gap during rolling, thereby reducing fatigue damage to the crystallizing rolls and extending their service life. On the other hand, it can even out the surface tension of the cast strip, thereby reducing the probability of surface cracking and improving the surface quality of the cast strip.

[0033] The functions and limitations of the components in the pure nickel strip involved in this invention are explained below:

[0034] C: At 1100℃, 0.5% of carbon dissolves in nickel. However, as the temperature of the nickel plate decreases, the solubility of carbon in nickel drops sharply, reaching only 0.02% at room temperature. Excessive carbon can deposit as graphite and also form segregation at grain boundaries, making it easily oxidized and forming voids. At high temperatures, it can even be oxidized to generate gases such as CO and CO2, causing bubbles on the nickel plate surface and affecting product quality. Therefore, the carbon content in this invention is no higher than 20 ppm.

[0035] Si: Si is more reactive than Ni, and therefore will be oxidized before Ni, thus forming an island-like SiO2 structure under the NiO layer. Due to the difference in their coefficients of thermal expansion, the NiO layer is prone to peeling off during the cooling process after heating. Furthermore, Si oxide cannot be reduced by annealing in hydrogen, so the Si content must be strictly limited. This invention limits it to below 10 ppm.

[0036] Mn: Mn is more reactive than Ni, so it is oxidized before Ni and will form oxides between Ni and NiO layers. Therefore, the present invention controls the Mn content to below 12 ppm.

[0037] Mg: Mg is also chemically active, and because of its small molar volume, it can easily increase the porosity of nickel plates. Therefore, the present invention controls its content to below 3 ppm.

[0038] Sulfur (S) is a harmful element in nickel plates. It has an adverse effect on the toughness and tensile properties of nickel plates. Excessive sulfur in nickel molten metal will precipitate NiS at the grain boundaries. Since sulfides are larger in volume than metals, stress will exist between the grain boundaries, thereby reducing the mechanical properties of the product. Therefore, the lower the sulfur content in nickel, the better. Taking into account the current smelting level and economic factors, this invention controls the sulfur content to below 2 ppm.

[0039] Al: Due to its strong affinity for oxygen, Al readily forms Al2O3 in the Ni matrix, which further leads to Ni diffusion to the outer layer, forming a NiO layer. Al2O3 is also quite hard, making it difficult to deform under stress, thus easily causing pores to form during material processing. Therefore, this invention controls the Al content to below 7 ppm.

[0040] Ti: In Ni water, Ti easily diffuses to the surface of the nickel plate during processing to form TiO2, and conventional heat treatment cannot reduce it. Therefore, in this invention, the Ti content is controlled to be below 25 ppm.

[0041] As a preferred embodiment, the diameters of the bottom and top surfaces of the crystallizing roller are 300 mm, and the diameter at 1 / 2H is 299.6 mm or 299.4 mm, with a casting speed of 90 m / min. In this invention, when the diameters of the bottom and top surfaces of the crystallizing roller are 300 mm, the diameter at 1 / 2H is 299.6 mm or 299.4 mm, and the coating is 65% Ni-35% Mo, the cable tie thickness tolerance of the product obtained with a diameter at 1 / 2H of 299.6 mm is significantly smaller than that obtained with a diameter at 1 / 2H of 299.4 mm. However, the strength of the product obtained with a diameter at 1 / 2H of 299.4 mm is significantly higher than that obtained with a diameter at 1 / 2H of 299.6 mm.

[0042] As a preferred embodiment, the diameters of the bottom and top surfaces of the crystallizing roller are 300 mm, and the diameter at 1 / 2H is 299.6 mm or 299.4 mm, with a casting speed of 90 m / min. In this invention, when the diameters of the bottom and top surfaces of the crystallizing roller are 300 mm, the diameter at 1 / 2H is 299.6 mm or 299.4 mm, and the coating is 70% Ni-30% Cr, the product with a diameter at 1 / 2H of 299.4 mm has a significantly smaller cable tie thickness tolerance than the product with a diameter at 1 / 2H of 299.6 mm. However, the product with a diameter at 1 / 2H of 299.4 mm has significantly higher strength than the product with a diameter at 1 / 2H of 299.6 mm.

[0043] The beneficial effects of this invention are:

[0044] 1) This invention optimizes the crystallizing roll shape by using a concave crystallizing roll instead of a straight one, giving the pure nickel cast strip a certain curvature. This improves the strip's shape and ensures that subsequent rolling produces thin strip products with uniform thickness, superior mechanical properties, good surface quality, and extremely small tolerances. This invention can directly obtain final pure nickel thin strips with high mechanical strength, crack-free surfaces, good quality, and small tolerances from molten nickel. Compared to traditional nickel plate production processes, the method involved in this invention has advantages such as a shorter process flow, higher production efficiency, lower energy consumption, and environmental friendliness.

[0045] 2) Compared with existing nickel plate production processes, the twin-roll thin strip continuous casting process of the present invention can utilize the residual heat of the cast strip for online hot rolling and compactly match continuous cold rolling, reducing heating, uncoiling and other steps in the process, shortening the production line length, thereby reducing the production cost of pure nickel thin strip.

[0046] 3) The nickel smelting is completed in a vacuum induction furnace, and the entire process from the start of smelting to pouring into the buffer ladle is carried out in a vacuum environment, which effectively avoids the oxidation of the nickel smelting and greatly reduces the generation of oxide scale, thereby reducing cracking during the nickel plate rolling process.

[0047] 4) Utilize nickel-molybdenum alloy and nickel-chromium alloy coatings to extend the service life of the crystallizing roller and accurately control the coating roughness, thereby increasing the contact area between the crystallizing roller and the molten nickel, improving heat transfer efficiency, ensuring continuous strip production, and improving the surface quality of the strip.

[0048] 5) For the first time, a twin-roll thin strip production method was proposed to produce pure nickel thin strip, which effectively improves the production efficiency of thin strip by utilizing online hot rolling and continuous cold rolling. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the process flow of the twin-roll thin strip continuous casting unit of the present invention.

[0050] Figure 2 This is a schematic diagram of the crystallization roller.

[0051] Figure 3 The images show a comparison of the nickel plates in Embodiments 1 and 2 of the present invention with those in Comparative Example 1. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] See Figure 1 The process flow of this invention is shown below:

[0054] The nickel smelting process is carried out using an induction furnace 3 within a vacuum chamber 1. During this process, a contact thermocouple 2 equipped with a PID temperature control system is used to detect and regulate the temperature of the nickel smelting. After the nickel smelting is completed, it enters a buffer ladle 5 through a long nozzle 4. The superheat of the nickel smelting in the buffer ladle is 70°C (temperature is 1520°C). Then, it enters a molten pool 7 composed of crystallizing rollers 9a and 9b and side sealing plates 8a and 8b through a flow-distribution nozzle 6. The nickel smelting is then cast into a cast thin strip 12 with a thickness of 3.0 mm (temperature is 1150°C) using a twin-roll thin strip continuous casting machine. The crystallizing roller has a width of 250mm (i.e., a height H of 250mm), and the diameters of its bottom and top surfaces are 300mm (the diameters at 1 / 2H are 299.8mm (Example 1), 299.6mm (Example 2), 299.4mm (Example 3), 299.8mm (Example 4), 299.6mm (Example 5), 299.4mm (Example 6), and 300mm (Comparative Example 1)). The casting speed of the casting machine is 90m / min. Both crystallizing rollers 9a and 9b have wire brushes 10a and 10b of the same width as the crystallizing rollers arranged on their outer sides. The wire brushes 10a and 10b are made of copper alloy and are used to remove excess oxide deposits generated on the surfaces of the crystallizing rollers 9a and 9b during the continuous casting process. From the flow-type nozzle 6 to the area where gas cooling is complete is a gas protection box 14, filled with inert gas, specifically nitrogen, to prevent high-temperature oxidation of the thin strip.

[0055] After exiting the crystallization rolls 9a and 9b (at a temperature of 1150℃), high-pressure air-cooling nozzles 11 are evenly arranged on both sides of the wide face of the cast strip 12 along the width of the strip and the casting direction. The entire air-cooling section is 0.3mm long. The nozzle gas is an inert gas, specifically helium, which prevents oxidation of the strip surface during the cooling process. The inert gas emitted by the high-pressure air-cooling nozzles 11 rapidly and uniformly cools the cast strip to 970℃, with a cooling rate of not less than 50℃ / s. The strip is then transported to the pinch rolls 15 via the fan-shaped guide plate 13, and then to the online hot rolling mill 17 via the transport rolls 16, where it is rolled to 1.7mm with a reduction rate of 43%. The strip is subsequently cooled by laminar flow using a No. 1 high-pressure water nozzle 18 at a cooling rate of not less than 60℃ / s, directly cooling it to room temperature. It is then continuously cold-rolled to 0.45mm using a 3-6 pass cold rolling mill 19. After being cut by the flying shear 20, the thin strip is rolled into the final nickel coil by the high-power coiler 21.

[0056] The pure nickel molten metal in Examples 1-6 and Comparative Example 1 of this invention was obtained by vacuum induction melting (VIM) or double vacuum melting, i.e., vacuum induction melting (VIM) combined with vacuum arc refining (VAR) and ladle refining. The specific chemical composition is shown in Table 1. Table 2 shows the crystallization roll concavity, surface coating material, coating roughness, austenite grain size, strip thickness, strip surface quality, strip thickness tolerance, and tensile properties of the thin strip coil at room temperature for the examples and comparative examples. It can be seen that the pure nickel strip of this invention has a yield strength greater than 150 MPa, a tensile strength greater than 370 MPa, and an elongation greater than 40%, exhibiting excellent comprehensive mechanical properties. Comparative Example 1 shows that the nickel plate produced by thin strip continuous casting meets the requirements in terms of composition, austenite grain size, and final mechanical properties, indicating that this technology can fully meet the production needs of pure nickel thin strip.

[0057] Table 1. Chemical composition (mass percentage ppm) of nickel solutions from Examples 1-6 and Comparative Example 1

[0058]

[0059]

[0060] Table 2. Thin strip continuous casting process parameters, surface quality, and properties of Examples 1-6 and Comparative Example 1.

[0061]

[0062]

[0063] Figure 3 In the diagram, a is a photograph of the nickel plate obtained in Comparative Example 1; b is a photograph of the nickel plate obtained in Example 1; and c is a photograph of the nickel plate obtained in Example 2. Figure 3 As can be seen, using a concave crystallizing roller can effectively reduce the number of pits on the surface of the thin strip and reduce the generation of cracks. However, the concavity of the concave roller must be precisely controlled during use to ensure the quality of the thin strip.

Claims

1. A short process for the production of pure nickel strip material, characterized in that, Comprising the following steps: 1) Nickel water smelting High-purity nickel water is smelted by an induction furnace under vacuum environment, and the mass percentage of the chemical composition of the molten nickel water obtained by smelting is: C: ≤20.0 ppm, Si: ≤10 ppm, Mn: ≤12 ppm, S: ≤2.0 ppm, Mg: ≤3.0 ppm, Al: ≤7 ppm, Ti: ≤25 ppm, and the balance is Ni and unavoidable impurities; in the step 1), after the nickel water smelting is completed, the vacuum valve needs to be opened to break the vacuum and inert gas is blown in; 2) Thin strip casting The molten nickel water in the vacuum induction furnace is poured into a buffer bag through a long nozzle, and flows into the crystallization roll pool through the shunt nozzle under the buffer bag, and finally the pure nickel as-cast thin strip is cast by a double-roll thin strip continuous casting machine; the crystallization roll used by the double-roll thin strip continuous casting machine is a concave crystallization roll, which has a spindle structure with large ends and small middle, defined: the concave crystallization roll is erected, the top surface and the bottom surface are composed of two circles with equal radius and R, the height from the bottom surface to the top surface is H, the radius of the circle on the plane of 1 / 2H of the concave crystallization roll is R1; and R-R1=0.2-0.3mm; along the bottom surface upward to 1 / 2H, the diameter of the circle constituting the concave crystallization roll decreases linearly; along the bottom surface upward, after passing through 1 / 2H, the diameter of the circle constituting the concave crystallization roll increases linearly in the direction of the top surface; the temperature of the molten nickel water is 1500-1550℃; the temperature of the nickel water entering the crystallization roll pool is 1490-1530℃; the average distance of the double rolls is 2.0mm-5.0mm; 3) Hot rolling The as-cast thin strip is cooled to 850-1000℃ by high-pressure gas cooling nozzle spraying inert gas after coming out of the crystallization roll, the cooling rate is 50-100℃ / s, and then online hot rolling is carried out, the hot rolling reduction is not higher than 50%; the as-cast thin strip is rolled to 1.0-3.0mm by one pass hot rolling between 850~1000℃; 4) Cold rolling The rolled strip after hot rolling is cooled to room temperature by high-pressure water nozzle, the cooling rate is 60-150℃ / s; then 3-6 passes of cold rolling are carried out to roll it into a 0.3~0.8mm rolled strip, and the total reduction is not higher than 80%; 5) Nickel strip coiling The pure nickel rolled strip after cold rolling is coiled by a coiling machine to obtain the final nickel coil.

2. A short process technique for the production of pure nickel strip as claimed in claim 1, wherein: In the step 1), the smelting method is vacuum induction melting or double vacuum melting, i.e. vacuum induction melting plus vacuum consumable, and further refining is used to control the composition of the nickel water.

3. A short process technique for the production of pure nickel strip as claimed in claim 1, wherein: In the step 2), the superheat of the nickel water is 50-100℃.

4. A short process technique for the production of pure nickel strip as claimed in claim 1, wherein: In the step 2), the thickness of the as-cast thin strip is 2.0-5.0mm, and the casting speed of the double-roll thin strip continuous casting machine is 60-100m / min.

5. A short process technique for the production of pure nickel strip as claimed in claim 1, wherein: In the step 2), the surface of the crystallization roll is shot blasted and electroplated to control the surface roughness of the crystallization roll to be less than or equal to 30 μm, and the plating layer material is at least one of pure nickel, pure chromium, nickel-based alloy, chromium-based alloy and ceramic coating.

6. A short process technique for the production of pure nickel strip as claimed in claim 1, wherein: In the step 5), the coiling temperature is room temperature.

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