A short process for preparing high-purity nickel plate

Abstract

The present application belongs to the technical field of nonferrous metallurgy, and relates to a short-process preparation method of high-purity nickel plate. The present application designs a series double-roller continuous casting machine to realize the transformation of metallic nickel from molten state to cast state, adopts two groups of concave crystallization rollers arranged vertically, which are of the same structure and material but different roll gaps, to continuously cast nickel water, and then performs hot rolling after cooling to hot rolling temperature, and further cools to obtain the final nickel plate by coiling. The series double-roller continuous casting machine can ensure the rapid transformation of nickel water to nickel plate and the control of the shape of the nickel plate; the concave crystallization rollers are used instead of the traditional flat crystallization rollers to increase the heat exchange area between the nickel water and the crystallization rollers, improve the grain refinement degree of the thin strip, and reduce the surface defects caused by stress concentration; the thin strip cross section has an arc, and the existence of the arc provides a deformation space for subsequent rolling, which can reduce the occurrence of quality problems such as surface cracking and depression of the cast strip; the method has the advantages of short process, high production efficiency, low energy consumption and environmental friendliness.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of non-ferrous metallurgy, and particularly relates to a short-process preparation method of high-purity nickel plate. BACKGROUND

[0002] Thin strip casting technology is mainly divided into belt type thin strip casting and roller type thin strip casting, and the belt type thin strip casting is further divided into single belt or double belt thin strip casting, and similarly, the roller type thin strip casting is also divided into single roller and double roller thin strip casting. The double roller thin strip casting technology is regarded as the most revolutionary front technology in the steel metallurgy field in the 21st century. In the double roller thin strip casting process, high-temperature molten metal is directly cast on a water-cooled copper crystallizer roller to form a thin cast strip with a thickness of about 1-5 mm. Since this technology can make molten steel solidify rapidly, the reheating and a large number of rolling processes in the traditional continuous casting process are omitted, so compared with the traditional continuous casting and thin slab continuous casting and rolling technology, the double roller thin strip casting technology can omit or only need a small amount of hot rolling process, thereby greatly shortening the production line, reducing equipment investment, site occupation and energy consumption. In recent years, the double roller thin strip casting technology has become an advanced casting technology that is developed by steel companies around the world. Since the 1980s, some important thin strip casting projects have had a great influence on the development of the technology. They include a stainless steel thin strip casting project of Nippon Steel-Mitsubishi Heavy Industries, a EUROSTRIP thin strip casting project jointly developed by the European Union, a CASTRIP thin strip casting project developed by NUCOR Steel Company in the United States, and a thin strip casting project of POSCO Steel Company in South Korea. In China, Baosteel Group and Jingye Group have also built high-level double roller thin strip casting industrialization lines and carried out industrialization trial production practices, and important progress has been made. However, up to now, only NUCOR Steel Company in the United States has successfully commercialized the technology, and it is limited to the production of low-carbon steel and low-carbon micro-alloyed steel.

[0003] With the development of the energy industry in the world towards low-carbonization, China has proposed the "double carbon" goal. This measure not only marks a historic change in green development and carbon reduction, but also promotes the transformation and upgrading of China's energy and related industries to achieve long-term healthy and sustainable development of the national economy. Under this background, the double roller thin strip casting technology, with its short process and low energy consumption, not only highly matches the national development strategy, but also meets the development needs of energy industry in energy saving and cost reduction. Therefore, it is highly valued by relevant scientific and technological workers and is regarded as the main development direction of near-net-shape casting production. However, the existing thin strip technology is mainly used for producing low-carbon steel, low-carbon micro-alloyed steel and high-carbon steel strip.

[0004] Nickel is a chemical element with important application value, and is often used as an alloying element to improve the mechanical properties of alloy materials in the development of metal materials. At the same time, nickel is also an excellent metal with high electrical conductivity, high temperature stability and excellent corrosion resistance, and is widely used in transportation, new energy batteries, aerospace and military equipment fields. With the progress of science and technology, the demand for high-purity nickel is also increasing. At present, the production and processing of high-purity nickel plate is mostly realized by traditional die casting combined with rolling. Specifically, nickel water with qualified composition is produced by vacuum consumable or electroslag remelting, and then ingots are obtained by die casting, and finally pure nickel plate is produced by turning, hot rolling and multi-pass cold rolling. This traditional production process is very complicated, on the one hand, the heat lost during the solidification of molten nickel water is not utilized, on the other hand, quality defects such as shrinkage and porosity are prone to occur during the solidification process, resulting in low yield (Xi Jin-hui, Shu Ying, Xie Wen-long. Preparation process of pure nickel plate [J]. Hot Working Technology, 2015, 44(17): 111-114+117.). In addition, during the production of nickel-based alloy by traditional method, quality problems such as edge curling and cracking are prone to occur due to multi-pass rolling (Wu Zhi-jie, Bian Lu-yang, Yuan Guo. Microstructure and texture evolution and properties of thin strip cast Fe-36Ni alloy [J]. Journal of Materials and Metallurgy, 2019, 18(03): 213-218.). Therefore, how to efficiently, greenly and economically produce high-purity nickel plate is one of the research hotspots in this industry. Under this background, the twin-roll thin strip casting technology as a near-net-shape casting technology can not only realize the transformation of metal from molten state to solid state, but also directly produce metal plate close to the product size, which is very suitable for the production and processing of high-purity nickel plate.

[0005] It is found through in-depth exploration that direct production of pure nickel plate by twin-roll thin strip casting technology has certain problems, mainly in that the thickness of nickel plate is not uniform enough, and the strip shape of the cast strip is not well controlled, which affects the subsequent hot rolling forming. As can be seen, although the twin-roll thin strip casting technology has great advantages in producing pure nickel plate, further optimization of the process is still needed to realize the production of high-quality pure nickel plate. According to the existing research results, there are few records of using a tandem twin-roll caster to prepare pure nickel plate. SUMMARY

[0006] In order to solve the problems in the prior art, the present application provides a short-process preparation method of high-purity nickel plate, which realizes the production of high-purity nickel plate by pouring molten nickel water on a continuous casting machine (i.e. a tandem double-roller continuous casting machine) capable of secondary rolling and cooling. The tandem double-roller continuous casting machine can not only realize the sub-rapid solidification of nickel water from a molten state to a cast state, but also ensure that the thickness of the produced cast strip is more uniform through two times of cooling and rolling. In addition, the rolling of the two concave rollers can make the cast strip have a certain arc, and the existence of the arc can guide the nickel plate to produce appropriate deformation in the hot rolling process and provide a certain deformation space for the deformation of the plate in the rolling process, so that the stress distribution on the surface of the cast strip is more uniform, the stress concentration on the surface of the cast strip is reduced, the cracking phenomenon in the rolling process is finally reduced, and the surface quality of the cast strip is improved.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] The short-process preparation method of high-purity nickel plate provided by the present application comprises the following steps:

[0009] 1) Nickel water smelting

[0010] The smelting process is carried out under vacuum throughout the process, and the molten nickel water is obtained by smelting with a vacuum induction furnace, and the mass percentage of the chemical composition is: C: ≤20.0ppm, Si: ≤10ppm, Mn: ≤12ppm, S: ≤2.0ppm, Mg: ≤3.0ppm, Al: ≤7ppm, Ti: ≤25ppm, and the balance is Ni and unavoidable impurities;

[0011] 2) Thin strip casting

[0012] The molten nickel water in the vacuum induction furnace is poured into the buffer bag through the long nozzle, and flows into the crystallization roller pool through the shunt nozzle under the buffer bag, and finally the pure nickel cast thin strip is cast out through the tandem double-roller thin strip continuous casting machine;

[0013] The tandem double-roller thin strip caster is two groups of crystal rollers arranged in the vertical direction and having the same structure and material, and is defined as follows: after the first group of crystal rollers is arranged, only the vertical position is changed, and all other devices are translated to arrange the second group of crystal rollers, the roll gap of the second group of crystal rollers is smaller than that of the first group of crystal rollers, the roll gap distance of the first group of crystal rollers is d1, the roll gap of the second group of crystal rollers is d2, the horizontal roll gap difference Δd = d1-d2 is 0.2-0.5mm, and at the same time, to ensure the secondary rolling effect, the ratio of the roll gap difference of the upper and lower groups of crystal rollers to the roll gap of the second group of crystal rollers is preferably Δd / d2 = 10%-20%; the distance between the upper and lower groups of crystal rollers of the tandem double-roller thin strip caster is preferably as close as possible without contact, and the distance is preferably ≤2.5cm, and the rotating speeds of the upper and lower groups of crystal rollers are the same;

[0014] In addition, the crystal rollers used are all concave crystal rollers having a spindle structure with large ends and a small middle part, and are defined as follows: after the concave crystal roller is vertically arranged, the top surface and the bottom surface are composed of two circles with equal radii and an R, the height from the bottom surface to the top surface is H, the radius of the circle at the plane of 1 / 2H of the concave pinch roller is R1, the concavity is R-R1 = 0.2-0.3mm, and is preferably 0.2mm; the radius of the circle constituting the concave crystal roller decreases along the bottom surface to 1 / 2H; the radius of the circle constituting the concave crystal roller increases along the bottom surface to the top surface after passing 1 / 2H; the temperature of the molten nickel water is 1500-1550℃; the temperature of the nickel water entering the molten pool of the first group of crystal rollers is 1490-1530℃; the temperature of the cast strip after being cooled by the first group of crystal rollers is 1000-1150℃, and the temperature of the cast strip after being cooled by the second group of crystal rollers is 850-1000℃; the average roll gap distance d2 of the second group of crystal rollers is 2.0mm-5.0mm; and the increasing or decreasing mode is preferably a circular arc shape.

[0015] The temperature of the cast pure nickel strip cast by the tandem double-roller thin strip caster is 850-1000℃.

[0016] Preferably, the concave crystal roller in the application has a nickel-chromium alloy plating layer on the surface; the thickness of the plating layer is 20-60μm; further preferably, the content of nickel in the nickel-chromium alloy plating layer is 50-80%, preferably 60-70%, and the balance is chromium.

[0017] The application discloses a short-process preparation method of high-purity nickel plate, which comprises the following steps: casting a pure nickel cast strip by a tandem double-roller thin strip caster, and then performing online hot rolling.

[0018] The as-cast thin strip of pure nickel is cooled after passing through a series double-roller casting machine, and the temperature is reduced to 850-1000 DEG C after rolling, and the as-cast thin strip of pure nickel is rolled to 1.0-3.0 mm at a temperature of 800-900 DEG C in one pass to obtain the hot-rolled high-purity nickel plate.

[0019] The short-process preparation method of the high-purity nickel plate is characterized in that the hot-rolled nickel plate is cooled immediately after being manufactured by a hot-roller, and the cooling is as follows:

[0020] The as-cast thin strip of high-purity nickel is further cooled to 100-300 DEG C by a high-pressure water nozzle, and the cooling rate is 60-150 DEG C / s.

[0021] The short-process preparation method of the high-purity nickel plate is characterized in that the cooled high-purity nickel plate is coiled by a coiling machine, and the high-purity nickel coil is obtained, and the coiled high-purity nickel coil is naturally cooled to room temperature.

[0022] Further, in the step 1), the smelting mode is vacuum induction melting (VIM) or double vacuum melting, i.e., vacuum induction melting (VIM) plus vacuum consumable (VAR), so as to realize the regulation of the nickel water composition; and the whole process from smelting to pouring is carried out in a vacuum environment, so as to effectively avoid the oxidation of the nickel water.

[0023] Further, in the step 2), the vacuum in the vacuum cover is broken after the smelting of the nickel water is completed, and inert gas is blown in to prevent the oxidation of the nickel water, and the inert gas is generally nitrogen.

[0024] Further, in the step 2), the temperature of the nickel water is collected by a contact thermocouple during the smelting process of the nickel water, and a PID intelligent temperature control system is matched to realize the detection and regulation of the temperature of the nickel water, so as to ensure that the temperature changes according to the preset process.

[0025] Further, in the step 2), the superheat of the nickel water is 50-100 DEG C.

[0026] Further, in the step 2), the thickness of the final cast strip is adjusted by controlling the distance between the crystallization rollers, and the thickness of the as-cast thin strip of high-purity nickel is 2.0-5.0 mm.

[0027] Further, in the step 2), the casting speed of the series double-roller thin strip casting machine is 60-100 m / min.

[0028] Further, the temperature of the as-cast thin strip after the rolling and cooling of the second group of crystallization rollers is 850-1000 DEG C, and the as-cast thin strip is on-line hot-rolled after passing through the second group of crystallization rollers, and the hot-rolling reduction is ≤50%.

[0029] The technical concept of the application is as follows:

[0030] 1) Utilize the production and processing commonality between nickel plate and steel plate, optimize the design of double-roller thin strip continuous casting technology to realize the short process production of high-purity nickel plate.

[0031] 2) Utilize the concave crystallization roller to increase the heat exchange area between the molten nickel water and the crystallization roller, improve the cooling efficiency, and play the role of refining the grain; at the same time, the concave crystallization roller has a certain spindle structure with large ends and small middle, which provides deformation space for the as-cast thin strip during continuous casting, reduces the stress concentration between the cast strip and the crystallization roller, and uniformly reduces the surface tension of the cast strip to reduce the probability of surface cracking of the cast strip.

[0032] 3) The series double-roller continuous casting machine is composed of two groups of crystallization rollers with the same speed, and the parameters such as the material, diameter and concavity of the crystallization rollers are the same, the as-cast thin strip is rolled and cooled again by changing the roll gap of the second group of crystallization rollers, which can ensure that the cross section of the as-cast thin strip maintains a certain plate shape, and can also ensure the uniformity of the thickness of the cast strip.

[0033] 4) The as-cast thin strip with arc cross section can effectively and uniformly bear stress during hot rolling, and the existence of the arc provides space for the deformation of the cast strip, thereby reducing the generation of surface defects such as cracks and depressions of the thin strip during rolling, and improving the surface quality of the product.

[0034] The components and limitations of the pure nickel cast strip involved in the application are as follows:

[0035] C: 0.5% C is dissolved in nickel at 1100 DEG C, but when the temperature of the nickel plate decreases, the solubility of C in nickel decreases greatly, and the solubility of C in nickel at room temperature is only 0.02%. Too much C will be deposited in the form of graphite on one hand, and will form segregation at the grain boundary position on the other hand, which is easy to be oxidized to form voids, and even at high temperature, it will be oxidized to generate CO, CO2 and other gases to cause bubbles on the surface of the nickel plate, affecting the product quality. Therefore, the C content of the application is not higher than 20ppm.

[0036] Si: Si is more active than Ni, so it will be oxidized before Ni, thereby forming island-shaped SiO2 under the NiO layer. Due to the difference in expansion coefficient, the material after heating is easy to have the problem of NiO layer falling off during cooling, and the oxide of Si cannot be reduced by annealing in hydrogen, so the content of Si must be strictly limited, which is limited to below 10ppm in the application.

[0037] Mn: Mn element is more active than Ni, so it will be oxidized before Ni, thereby forming an oxide between Ni and NiO layer, so the content of Mn is controlled to be below 12ppm in the application.

[0038] Mg: The chemical properties of Mg element are also relatively active, and because its molar volume is small, it is easy to increase the porosity of the nickel plate, so the content of Mg is controlled to be below 3ppm in the application.

[0039] S: S is a harmful element in the nickel plate. It has an adverse effect on the toughness and tensile properties of the nickel plate. If the content of S in the nickel water is too high, NiS will be precipitated at the grain boundary. Since the volume of the sulfide is larger than that of the metal, stress will exist between the grain boundaries, thereby reducing the mechanical properties of the product. Therefore, the lower the content of sulfur in nickel, the better. Considering the existing smelting level and economic factors, the content of S is controlled to be below 2 ppm in the application.

[0040] Al: Since Al element has strong oxygen affinity, it is easy to form Al2O3 in the Ni matrix, which further causes the diffusion of Ni to the outer layer to form a NiO layer. Al2O3 has high hardness and is difficult to deform during stress, so it is easy to form holes during material processing. Therefore, the content of Al is controlled to be below 7 ppm in the application.

[0041] Ti: Ti in the nickel water is easy to diffuse to the surface of the nickel plate during processing to form TiO2, and conventional heat treatment cannot reduce it. Therefore, the content of Ti is controlled to be below 25 ppm in the application.

[0042] As a preferred scheme, the diameters of the bottom surface and the top surface of the concave crystallization roller are 300 mm, the diameter at 1 / 2H is 299.6 mm, and the concavity is 0.2. The existence of the concavity can increase the contact area between the molten nickel water and the crystallization roller, thereby improving the heat transfer therebetween and increasing the cooling rate of the molten metal. At the same time, the cast strip has a certain camber, which provides a certain deformation space for subsequent rolling and ensures the surface quality of the product. If the concavity is too small, the plate shape adjustment of the metal plate is not obvious and the improvement effect is not achieved. If the concavity is too large, the subsequent rolling difficulty is increased, which is not conducive to the control of the surface quality.

[0043] As a preferred scheme, the horizontal roll gap between the upper and lower two groups of crystallization rollers in the designed tandem double-roller continuous casting machine is different. The horizontal roll gap d2 of the lower second group of crystallization rollers is smaller than the horizontal roll gap d1 of the upper first group of crystallization rollers. The roll gap difference is ensured to be Δd=d1-d2=0.2-0.5 mm. The second group of crystallization rollers performs secondary rolling on the cast strip after primary rolling, thereby improving the uniformity of the thickness of the cast strip. However, the horizontal roll gap difference of the two groups of crystallization rollers needs to be kept within a certain range. If the roll gap difference is too small or too large, the purpose of uniformizing the thickness of the cast strip cannot be effectively achieved. In the embodiment of the application, when the roll gap difference is 0.3 mm and 0.5 mm, the thickness tolerance and surface quality of the rolled strip obtained are obviously better than those when the roll gap difference is 0.1 mm and 0.7 mm.

[0044] The beneficial effects of the application are as follows:

[0045] 1) The present application can directly obtain final high-purity pure nickel coil from molten nickel water, compared with the traditional production of nickel plate process, the subsequent multi-pass cold rolling process is omitted, the method has the advantages of short process, high production efficiency, low energy consumption and environmental friendly.

[0046] 2) The concave crystallization roller is used instead of the traditional flat crystallization roller, which increases the heat exchange area between the molten nickel water and the crystallization roller, improves the heat exchange efficiency, and improves the thin strip grain refinement degree; in addition, it also uniformed the stress distribution on the surface of the cast strip, reduced the surface defects caused by stress concentration.

[0047] 3) The function of the designed and invented tandem double-roller continuous casting machine is that the first group of crystallization rollers realizes the transformation of molten nickel water to cast thin strip, the second group of crystallization rollers performs secondary cooling and rolling on the formed cast thin strip to ensure the uniformity of the cast strip thickness, and further determines the cast strip profile, so that the thin strip cross section has a certain arc, which provides a deformation space for the subsequent rolling process, and uniform the stress distribution of the cast strip in the rolling process, thereby reducing the occurrence of cast strip surface cracking, depression and other quality problems.

[0048] 4) The tandem double-roller continuous casting machine can continuously cool the cast strip, and the thin strip coming out of the second group of crystallization rollers is followed by a hot rolling process, which omits the cooling process, shortens the production line length and improves the production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 It is a schematic diagram of the process flow of the tandem double-roller thin strip continuous casting machine of the present application.

[0050] Figure 2 It is a schematic diagram of the gap difference of the upper and lower two groups of crystallization rollers of the tandem double-roller continuous casting machine.

[0051] Figure 3 It is a schematic diagram of the concave degree of the crystallization roller.

[0052] Figures 1-3 In the figure, vacuum cover 1, thermocouple 2, induction furnace 3, long nozzle 4, buffer bag 5, flow distribution type nozzle 6, molten pool 7, side sealing plate 8a, 8b, first group of crystallization rollers 9a, 9b, metal wire roller brush 10a, 10b, second group of crystallization rollers 11a, 11b, metal wire roller brush 12a, 12b, cast thin strip 13, fan-shaped guide plate 14, gas protection box 15, pinch roller 16, hot rolling mill 17, 1# high pressure water nozzle 18, conveying roller 19, flying shear 20, powerful coiling machine 21; d1 is the gap distance of the first group of crystallization rollers, d2 is the gap distance of the second group of crystallization rollers; R is the radius of the crystallization roller, H is the width of the crystallization roller. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work are within the protection scope of the present application.

[0054] Embodiments 1-6, see Figures 1-3 ;

[0055] The nickel water smelting work completed by the induction furnace 3 in the vacuum cover 1 collects the nickel water temperature by the contact thermocouple 2 during the smelting process, and the PID temperature control system is used to realize the detection and regulation of the nickel water temperature. After the nickel water smelting is completed, it enters the buffer bag 5 through the long water gap 4, and the superheat degree of the nickel water in the buffer bag is 70°C (the temperature is 1520°C), then the nickel water enters the molten pool 7 composed of the first group of crystallization rollers 9a, 9b and side sealing plates 8a, 8b through the flow distribution type water gap 6, and the nickel water is cast into a cast thin strip 13 (the temperature is 1150°C) with a thickness of 3.1mm (3.1mm in example 1, 3.3mm in example 2, example 5 and example 6, 3.5mm in example 3, and 3.7mm in example 4) by the first group of double-roller thin strip continuous casting machine. The cast strip further enters the second group of crystallization rollers 11a, 11b to be cooled again, and is subjected to secondary rolling to maintain its cross-sectional curvature and ensure the uniformity of the overall thickness of the cast strip (the temperature after cooling is 970°C). The horizontal roller gap difference between the second group of crystallization rollers 11a, 11b and the first group of crystallization rollers 9a, 9b is 0.1mm (0.1mm in example 1, 0.3mm in example 2, 5, 0.5mm in example 3, 6, and 0.7mm in example 4). The diameter of the bottom surface and the top surface of the concave pinch roller is 300mm, the diameter at 1 / 2H is 299.6mm, and the concavity is R-R1=150-149.8=0.2mm. The casting speed of the casting machine is 90m / min. Both groups of crystallization rollers are provided with a nickel-chromium alloy plating layer, and the mass fractions of nickel Ni and chromium Cr are 70% and 30% respectively. The outer sides of the two groups of crystallization rollers 9a, 9b and 11a, 11b are respectively provided with metal wire roller brushes 10a, 10b and 12a, 12b with the same width as the crystallization rollers. The metal wire roller brushes 10a, 10b and 12a, 12b are made of copper alloy and are used to brush off the excess oxide deposition film generated on the surface of the crystallization rollers 9a, 9b and 11a, 11b during the continuous casting process. From the flow distribution type water gap 6 to the area where the gas cooling is completed, it is a gas protection box 15 filled with inert gas, which is nitrogen, which can prevent the thin strip from being oxidized at high temperature. The structure and material of the first group of crystallization rollers 9a, 9b and the second group of crystallization rollers 11a, 11b are completely the same, but the horizontal roller gap distance is different, and the distance between the upper and lower two groups of crystallization rollers is 1.5cm (1.5cm in examples 1-4, 0.5cm in example 5, and 2.5cm in example 6).

[0056] After the as-cast thin strip 13 passes through the second set of crystallization rollers 11a, 11b, it is transported to the pinch roller 16 after passing through the fan-shaped guide plate 14, and then is sent to the hot rolling mill 17 to roll the as-cast thin strip 13 on-line to 1.8 mm (1.8 mm for Examples 1, 4 and 5, 1.9 mm for Example 2, and 1.7 mm for Examples 3 and 6), with a reduction ratio of 42%, and then is transported through the transport roller 19, during which the as-cast thin strip 13 is laminarly cooled by using the 1# high-pressure water nozzle 18, with a cooling rate of 60-150 ℃ / s, to directly cool the thin strip to 210 ℃; the cooled as-cast thin strip 13 is further cut by the flying shear 20, and finally is coiled into a final nickel coil by the strong coiler 21, and after coiling, the nickel coil is naturally cooled to room temperature.

[0057] The pure nickel nickel water of Examples 1-6 and Comparative Example 1 of the present application is obtained by vacuum induction melting (VIM) or double vacuum melting, i.e., vacuum induction melting (VIM) combined with vacuum consumable (VAR) and combined with secondary refining outside the furnace, and the specific chemical components are shown in Table 1. The type of continuous casting machine, the difference between the roll gaps of the crystallization rollers, the concave degree of the crystallization rollers, the material of the surface plating layer, the roughness of the plating layer, the rolling strip thickness, the surface quality of the rolling strip and the rolling strip thickness tolerance corresponding to Examples 1-6 and Comparative Example 1 are shown in Table 2. Among them, the basic parameters of the ordinary twin-roll continuous casting machine used in Comparative Example 1 are: the crystallization rollers are flat type, the roller diameter is 300 mm, the roller width is 100 mm, and the roll gap is 4 mm.

[0058] As can be seen from Table 2, the series type twin-roll continuous casting machine in the present application can effectively reduce the occurrence of surface pits and cracks of the cast strip by controlling the difference between the roll gaps of the two sets of crystallization rollers, the surface roughness is reduced, and the surface quality of the cast strip is effectively improved. In the series type twin-roll continuous casting machine designed in Examples 1-6 of the present application, there is a difference between the horizontal roll gaps of the upper and lower two sets of crystallization rollers, the horizontal roll gap d2 of the lower second set of crystallization rollers is smaller than that of the upper first set of crystallization rollers, and then the roll gap difference d1 is ensured to be Δd = d1-d2; among them, the roll gap difference of Examples 2-3 and 5-6 is ensured to be Δd = d1-d2 = 0.2-0.5 mm; when the roll gap difference is 0.3 mm (such as Example 2) and 0.5 mm (such as Example 3), the rolling strip thickness tolerance and surface quality obtained are significantly better than those of the roll gap difference Δd = 0.1 mm (Example 1) and Δd = 0.7 mm (Example 4), and the Δd / d2 corresponding to Examples 2-3 is 10% and 16.7%; in Example 5, the spacing between the upper and lower crystallization rollers is 0.5 cm, and in Example 6, the spacing between the upper and lower crystallization rollers is 2.5 cm, and the quality of the rolling strip produced by both is higher than that of Comparative Example 1, and the quality of the rolling strip produced by Example 5 is higher than that of Example 6, which indicates that under the condition of no contact and no interference between the upper and lower crystallization rollers, the smaller the spacing, the better the quality.

[0059] Table 1 Chemical components (mass percentage ppm) of nickel water of Examples 1-6 and Comparative Example 1

[0060] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Ti 22.3 19.6 21.8 22.5 17.9 19.6 21.3 Al 5.4 5.2 6.4 5.7 4.8 6.9 5.7 Mg 2.3 2.5 1.9 2.1 1.7 1.9 1.8 S 0.9 1.2 1.8 1.6 1.5 1.2 1.4 Mn 9.2 10.8 9.9 10.8 11 11.6 11.3 Si 6.4 8.5 7.8 6.9 9.7 10.4 7.4 C 17 16.9 17.7 19.8 15.6 17.6 18.3

[0061] Table 2 Thin strip casting process parameters and quality for Examples 1-6 and Comparative Example 1

[0062]

[0063]

Claims

1. A short process for the production of high purity nickel plate characterized by: Comprising the following steps: 1) Nickel water smelting The smelting process is carried out under vacuum, and the molten nickel water is obtained by vacuum induction furnace smelting, and the mass percentage of its chemical composition 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; 2) Thin strip casting The molten nickel water in the vacuum induction furnace is poured into the buffer bag through the 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 through the tandem double-roll thin strip continuous casting machine; The tandem double-roll thin strip continuous casting machine is two groups of crystallization rolls arranged in the vertical direction, which are completely the same in structure and material, and the definition is: after arranging the first group of crystallization rolls on the upper side, only the vertical position is changed, and all other equipment is translated to arrange the second group of crystallization rolls, the roll gap d2 of the second group of crystallization rolls is smaller than the roll gap d1 of the first group of crystallization rolls, then the roll gap difference Δd = d1-d2 is 0.2-0.5mm; The distance between the upper and lower two groups of crystallization rolls of the tandem double-roll thin strip continuous casting machine is ≤2.5cm, and the rotating speeds of the upper and lower two groups of crystallization rolls are the same; The ratio of the roll gap difference of the upper and lower two groups of crystallization rolls to the roll gap of the second group of crystallization rolls is Δd / d2 = 10%-20%; In addition, the crystallization rolls used are all concave crystallization rolls, which have a spindle structure with large ends and small middle, and the definition is: after the concave crystallization roll is erected, the top surface and the bottom surface are composed of two circles with equal radii and R, the height from the bottom surface to the top surface is H, and the radius of the circle on the plane of 1 / 2H of the concave pinch roll is R1, and the concavity is R-R1 = 0.2-0.3mm; The radius of the circle constituting the concave crystallization roll decreases along the bottom surface to 1 / 2H; Along the bottom surface upward, after passing 1 / 2H, the radius of the circle constituting the concave crystallization roll increases 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 first group of crystallization roll pool is 1490-1530℃; The temperature of the cast strip after cooling through the first group of crystallization rolls is 1000-1150℃, and the temperature of the cast strip after cooling through the second group of crystallization rolls is 850-1000℃, and the average roll gap of the second group of crystallization rolls is 2.0mm-5.0mm; The temperature of the pure nickel as-cast thin strip cast by the tandem double-roll thin strip continuous casting machine is 850-1000℃; In the step 2), the superheat of the nickel water is 50-100℃; In the step 2), the thickness of the high-purity nickel as-cast thin strip is 2.0-5.0mm; In the step 2), the casting speed of the double-roll thin strip continuous casting machine is 60-100m / min; 3) Hot rolling After the pure nickel as-cast thin strip is cooled and rolled by the tandem double-roll continuous casting machine, the temperature is reduced to 850-1000℃, and it is rolled to 1.0-3.0mm in one pass at this temperature interval, and the temperature of the hot-rolled high-purity nickel plate is 800-900℃; 4) Cooling The high-purity nickel plate in hot-rolled state is further cooled to 100-300℃ by high-pressure water nozzles, and the cooling rate is 60-150℃ / s; 5) nickel plate curling The cooled high-purity nickel plate strip is coiled to obtain a high-purity nickel coil.

2. The short process for the production of high purity nickel plate according to claim 1, characterized in that: In the step 1), the smelting mode is vacuum induction melting or vacuum induction melting plus vacuum consumable, so as to realize the regulation of the nickel-water composition.

3. The short process for the production of high purity nickel plate according to claim 1, characterized in that: In the step 2), the vacuum in the vacuum cover needs to be broken after the nickel-water smelting is completed, and inert gas is blown in to prevent the nickel-water from being oxidized.

4. The short process for the production of high purity nickel plate according to claim 1, characterized in that: In the step 2), the concave crystallization roller surface is provided with a nickel-chromium alloy plating layer; the thickness of the plating layer is 20-60μm; the content of nickel in the nickel-chromium alloy plating layer is 50-80%, and the balance is chromium.

5. The short process for the production of high purity nickel plate according to claim 1, characterized in that: In the step 3), the hot rolling reduction rate is ≤50%.

6. The short process for the production of high purity nickel plate according to claim 1, characterized in that: In the step 5), the curled high-purity nickel coil is naturally cooled to room temperature.

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