Hot rolling control method based on N6 pure nickel 5mm thin strip

Abstract

The invention discloses a hot rolling control method based on an N6 pure nickel 5 mm thin strip, and belongs to the field of metal material hot rolling, and the hot rolling control method specifically comprises the steps that 1, a pure nickel forging stock is heated in a preheating section, a first heating section, a second heating section, a third heating section and a soaking section in sequence, and the total heating time is kept to be 220-320 min; 2, the heated blank is conveyed to a roughing mill, a roughing mill set adopts three-pass vertical rolling and seven-pass flat rolling, the initial rolling temperature ranges from 1050 DEG C to 1150 DEG C, the pass reduction rate of roughing rolling ranges from 18% to 23%, the total deformation of roughing rolling ranges from 75% to 80%, the width of the blank at a roughing rolling outlet ranges from 420 mm to 425 mm, and the thickness of the blank at the roughing rolling outlet ranges from 34 mm; 3, the rough rolling blank is sent to a finish rolling area, a finish rolling unit adopts two-pass vertical rolling and nine-pass flat rolling, the temperature of a finish rolling inlet is controlled to be 1000-1050 DEG C, and the finish rolling temperature is controlled to be 850-900 DEG C; 4, after finish rolling is completed, the strip steel is fed into a crimping machine through a flat plate chain to be crimped, and the crimping temperature ranges from 550 DEG C to 600 DEG C; according to the method, the N6 pure nickel thin strip which is uniform in structure, stable in performance and excellent in surface quality is obtained by controlling heating, rolling and curling links.

Description

Technical Field

[0001] This invention relates to a rolling control method, specifically a hot rolling control method based on 5mm N6 pure nickel thin strip, belonging to the field of hot rolling technology of metallic materials. Background Technology

[0002] N6 pure nickel (Ni content ≥ 99.5%) is widely used in high-end fields such as new energy batteries, electronic components, aerospace, and chemical equipment due to its excellent corrosion resistance, high-temperature oxidation resistance, good electrical and thermal conductivity, and mechanical properties. These applications typically require pure nickel strips with millimeter-level or even micrometer-level thickness, high-precision dimensions, smooth surface quality, and excellent mechanical properties. Hot rolling a 150mm thick forging billet into a 5mm thin strip is a key preparatory step for subsequent cold rolling to micrometer-level ultra-thin strips.

[0003] Hot rolling is a key process for rolling cast or forged billets into thin strips. However, the following problems exist in the rolling process of N6 pure nickel: (1) In the existing heating technology, direct heating is used without changing the heating rhythm according to the actual situation. Therefore, when the nickel plate is in a low temperature environment, hot rolling is carried out directly, which can easily lead to changes in the internal grains of the nickel plate, resulting in a lower yield and reduced performance; (2) During the rolling process, the oxide scale and exogenous hard particles cannot fall off on their own. When pressed into the nickel plate, they will seriously affect the surface quality; (3) The thinner the nickel plate, the worse its plate shape control accuracy will be, and problems such as nickel plate cracking, uneven deformation, surface damage, folding, and severe edge waviness will occur, affecting the normal use of the nickel plate.

[0004] Currently, patent CN109351771A describes a method for rolling high-purity nickel plates, which includes the following steps: Step 1: Hot rolling blanking, where high-purity nickel ingots are heated and then hot rolled blanks, and the high-purity nickel ingots are rolled into rough-rolled nickel plates with a thickness of 2.5-3.0 mm through multiple passes; Step 2: Finished product warm rolling, where the surface of the rough-rolled nickel plate is alkaline washed, cleaned, and then finished product warm rolling, where the rough-rolled nickel plate is rolled into a finished warm-rolled nickel plate with a thickness of 0.1-0.3 mm; Step 3: Annealing the finished warm-rolled nickel plate, and then trimming the edges of the finished warm-rolled nickel plate with a shearing machine. This method uses multiple passes in both hot rolling blanking and finished product warm rolling to make the rolled nickel plate flat and free of defects such as roller marks and scratches. However, this method has a short heating and holding time, which cannot achieve sufficient homogenization of the microstructure. Furthermore, dephosphorization is not performed during the rolling process, and surface oxide scale and hard particles cannot be removed, affecting surface quality.

[0005] Patent CN115889454B discloses a method for preparing hot-rolled pure nickel strip coil. Specifically, a pure nickel slab is loaded into a heating furnace and its exit temperature is maintained at 950–1060°C. The heated pure nickel slab is dephosphorized and then fed into a roughing mill for multiple passes of roughing to obtain a rough-rolled slab. The rough-rolled slab is then dephosphorized and fed into a finishing mill for multiple passes of finishing to obtain a finishing slab. The finishing slab is cooled. The cooled finishing slab is then coiled to obtain a pure nickel strip coil. In actual operation, the rolling process only involves one furnace heating, resulting in lower energy costs. Dephosphorization is performed after the furnace heating process using a dephosphorization device. The process effectively removes oxides generated on the slab surface in the heating furnace. Dephosphorization is also performed before the finishing mill to remove oxides generated during rough rolling, thus significantly improving the surface quality of pure nickel strip coils. Furthermore, the continuous operation of each step using a hot continuous rolling mill results in high rolling speeds. Pure nickel hot-rolled strip coils produced by this method have advantages such as good surface quality, high dimensional accuracy, high production efficiency, and low energy consumption and production costs. However, this method only involves one heating in the furnace, and the heating temperature is not high enough, with insufficient holding time, making it impossible to achieve sufficient temperature and microstructure homogenization.

[0006] Therefore, developing a dedicated hot rolling control method for N6 pure nickel strip that can overcome the above defects has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to propose a hot rolling control method based on 5mm N6 pure nickel strip, which addresses the shortcomings of the existing technology. This method obtains N6 pure nickel strip with uniform structure, stable performance and excellent surface quality by controlling the heating, rolling and coiling processes.

[0008] The technical solution of this invention to solve the above technical problems is: A hot rolling control method based on 5mm N6 pure nickel thin strip specifically includes the following steps: Step (1): The pure nickel forging billet is heated in a heating furnace. The heating is divided into 5 sections, namely the preheating section, the first heating section, the second heating section, the third heating section and the soaking section. The total heating time is maintained at 220-320 min. Step (2): The heated billet is conveyed to the roughing mill by the conveyor roller. The roughing mill adopts 3 vertical rolling and 7 horizontal rolling. The initial rolling temperature is 1050-1150℃, preferably 1090℃. The reduction rate of each roughing pass is 18%-23%. The total deformation of the roughing is 75-80%. The width of the billet at the exit of the roughing mill is 420-425mm and the thickness is 34mm. Step (3): The roughing billet is conveyed to the finishing rolling area through the intermediate roller table. The intermediate roller table is equipped with a heat insulation cover. The finishing rolling mill adopts 2 vertical rolling passes and 9 horizontal rolling passes. The reduction rate of each finishing rolling pass is 14%-17%, the total deformation of finishing rolling is 84-86%, the entry temperature of finishing rolling is controlled at 1000-1050℃, and the final rolling temperature is controlled at 850-900℃. Step (4): After finishing rolling, the strip is fed into the coiling machine via a flat chain to complete the coiling. Protective plates are installed on both sides of the flat chain for transport. The coiling temperature is 550-600℃.

[0009] The technical solution further defined in this invention is as follows: Furthermore, in the aforementioned hot rolling control method based on N6 pure nickel 5mm thin strip, the thickness of the pure nickel forging billet in step (1) is 145-160mm.

[0010] In the aforementioned hot rolling control method based on N6 pure nickel 5mm thin strip, the preheating temperature in step (1) is 500-600℃.

[0011] In the aforementioned hot rolling control method based on N6 pure nickel 5mm thin strip, the heating section in step (1) is divided into three sections. The temperature of the first heating section is 800-900℃, preferably 830℃; the temperature of the second heating section is 850-1050℃, preferably 950℃; and the temperature of the third heating section is 970-1070℃, preferably 1020℃.

[0012] In the aforementioned hot rolling control method based on N6 pure nickel 5mm thin strip, the temperature of the forging billet soaking section in step (1) is 1080~1150℃, preferably 1100℃.

[0013] In the aforementioned hot rolling control method based on N6 pure nickel 5mm thin strip, the duration of the high-temperature section of the heating three sections and the homogenization section in step (1) is 100-150 min.

[0014] In the aforementioned hot rolling control method based on N6 pure nickel 5mm thin strip, the rolling mill sequence of the roughing mill in step (2) is as follows: vertical rolling - horizontal rolling - horizontal rolling - vertical rolling - horizontal rolling - horizontal rolling - vertical rolling - horizontal rolling - horizontal rolling - horizontal rolling.

[0015] In the aforementioned hot rolling control method based on N6 pure nickel 5mm thin strip, the width of the rough rolling exit billet in step (2) is 420-425mm and the thickness is 34mm.

[0016] In the aforementioned hot rolling control method based on N6 pure nickel 5mm thin strip, the rolling sequence of the finishing mill in step (3) is as follows: vertical rolling - horizontal rolling - horizontal rolling - vertical rolling - horizontal rolling - horizontal rolling - horizontal rolling - horizontal rolling - horizontal rolling - horizontal rolling - horizontal rolling - horizontal rolling - horizontal rolling.

[0017] In the aforementioned hot rolling control method based on N6 pure nickel 5mm thin strip, three dephosphorization waters are opened in the rolling area of ​​steps (2) and (3), specifically: 1# rough dephosphorization pressure ≥22MPa, located in the first vertical roll mill area of ​​rough rolling; 1# fine dephosphorization pressure ≥17MPa, located in the third flat roll mill area of ​​fine rolling; 2# fine dephosphorization pressure ≥12MPa, located in the fifth flat roll mill area of ​​fine rolling.

[0018] The beneficial effects of this invention are: (1) This invention employs a five-stage heating system. First, the pure nickel forging billet is preheated. Simultaneously, by precisely controlling the temperatures of the first heating stage, the second heating stage, the third heating stage, and the soaking stage, the heating rate can be effectively slowed down. As the temperature of pure nickel gradually increases, its thermal conductivity gradually decreases. By using segmented heating, the core temperature can keep up with the surface temperature, minimizing thermal stress. In addition, the five-stage heating system allows for adjustment of the furnace temperature settings for each stage to accommodate pure nickel billets of different specifications.

[0019] (2) This invention employs a specific sequence of roughing and finishing mills. By alternating rolling directions, it ensures that the rolling thickness and width control are alternately performed under the large reduction of roughing, thus ensuring uniform deformation of the billet. The three vertical rolling passes also ensure the centering of the billet and prevent deviation. In the finishing rolling process, the first stage (vertical rolling-horizontal rolling-horizontal rolling) is used to set the width of the finishing rolling process and perform initial thinning. The second stage (vertical rolling-horizontal rolling-horizontal rolling-horizontal rolling-horizontal rolling-horizontal rolling-horizontal rolling-horizontal rolling) corrects the width deviation caused by the first two horizontal rolling passes and precisely controls the thickness of the finished product through continuous horizontal rolling.

[0020] (3) This invention effectively prevents problems such as waviness and warping that are prone to occur during rolling by combining a large reduction in roughing and a small reduction in finishing, ensuring the transverse thickness difference and straightness of the strip, and ensuring dimensional accuracy and surface quality. In the roughing stage, a large reduction is used, resulting in a large deformation per pass, shortening the rolling time, and fully breaking down the original structure to obtain uniform and fine grains; the high temperature and large deformation promote dynamic recrystallization and refine the grains. In the subsequent finishing stage, a small reduction is used, resulting in a relatively small rolling force and a small elastic deformation (mill bounce) of the mill, making it easier to accurately control the thickness of the finished product. At the same time, the smaller rolling force facilitates the shape control system (such as bending rolls and shifting rolls) to fine-tune the roll gap shape, thereby obtaining a good strip shape (flatness) and a finished product with smaller tolerances. Therefore, this invention combines a large reduction and a small reduction, which optimizes the allocation of the two core tasks of "deformation" and "control" in time and space according to the changing law of metal temperature and state during the rolling process.

[0021] (4) The present invention opens three dephosphorization waters in the roughing and finishing rolling areas respectively, which can effectively remove oxide scale and foreign hard particles from the surface of the billet, ensuring that the final pure nickel strip obtains excellent surface quality. Attached Figure Description

[0022] Figure 1 The image shows the metallographic structure near the surface of a pure nickel strip obtained using the hot rolling control method based on a 5mm N6 pure nickel strip according to an embodiment of the present invention. Figure 2 The image shows the metallographic structure at 1 / 4 of a pure nickel strip obtained using the hot rolling control method based on a 5mm N6 pure nickel strip according to an embodiment of the present invention. Figure 3 The image shows the metallographic structure at the center of a pure nickel strip obtained using the hot rolling control method based on a 5mm N6 pure nickel strip according to an embodiment of the present invention. Detailed Implementation

[0023] The present invention will now be clearly and completely described with reference to specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Example 1

[0024] This embodiment provides a hot rolling control method based on 5mm N6 pure nickel thin strip. The N6 pure nickel forging billet has dimensions of 153*365*6100mm (thickness × width × length) and a target size of 5*410mm (thickness × width). The method includes the following steps: Step S1: The pure nickel forging billet is heated in a heating furnace. After the preheating temperature reaches 560℃ and is held for 20 minutes, the billet is heated for 40 minutes in the first stage at 830℃. The second stage of heating is at 950℃ and held for 45 minutes. The third stage of heating is at 1020℃ and held for 55 minutes. The soaking stage is at 1100℃ and held for 75 minutes. After the soaking stage, the billet is sent to the roughing mill through the conveyor rollers. Step S2: The roughing rolling start temperature is 1090℃. The roughing rolling mill adopts 3 vertical rolling passes and 7 horizontal rolling passes. The rolling sequence of the roughing rolling mill group is as follows: vertical rolling - horizontal rolling - horizontal rolling - vertical rolling - horizontal rolling - horizontal rolling - vertical rolling - horizontal rolling - horizontal rolling. The reduction of each horizontal rolling pass is 18%-23%. Through roughing rolling, the billet thickness is reduced from 153mm to 34mm, and the total deformation is 78%. Descaling water is turned on in the first vertical rolling mill area of ​​the roughing rolling mill. The descaling pressure of No. 1 roughing is ≥22MPa. The descaling water prevents hard particles from being pressed into the thin strip. After roughing rolling is completed, it is transferred to the finishing rolling area through the intermediate roller table. The intermediate roller table is equipped with a heat preservation cover. Step S3: Before entering the finishing mill, the raised portion of the billet head is removed. The finishing mill uses 2 vertical rolling passes and 9 horizontal rolling passes. The reduction rate of each finishing rolling pass is 14%-17%, and the total deformation of the finishing mill is 84-86%. The rolling sequence of the finishing mill is as follows: vertical rolling - horizontal rolling - horizontal rolling - vertical rolling - horizontal rolling - horizontal rolling - horizontal rolling - horizontal rolling - horizontal rolling - horizontal rolling - horizontal rolling. The entry temperature of the finishing mill is 1020℃, and the final rolling temperature is 880℃ (controlling the final rolling temperature to 880℃ ensures that the strip undergoes complete recrystallization after finishing rolling, resulting in a uniform microstructure and stable mechanical properties of the strip). The rolling speed is 4m / s. Two passes of descaling water are opened in the finishing mill area. Specifically: No. 1 descaling pressure ≥17MPa, located in the third horizontal rolling mill area of ​​the finishing mill; No. 2 descaling pressure ≥12MPa, located in the fifth horizontal rolling mill area of ​​the finishing mill. The descaling water prevents hard particles from being pressed into the thin strip. Step S4: After finishing rolling, the strip is fed into the coiling machine via a flat chain to complete the coiling of the strip and obtain the product. Protective plates are installed on both sides of the flat chain to prevent the thin strip from being scratched on the surface during the process of entering the coiling machine. The final coiling temperature is 570℃.

[0025] Finally, a visual inspection of the surface quality of the pure nickel strip revealed that the overall surface quality was good, with a smooth and clean surface and no cracks at the edges. Only a few long, narrow scratches and a few pits were observed at the beginning and end of the strip. Metallographic observation showed that the near-surface metallographic structure was... Figure 1 As shown, the metallographic structure at 1 / 4 is as follows Figure 2 As shown, the metallographic structure at the center is as follows Figure 3 As shown, the metallographic structure is comparable to the grain size and is uniform. Furthermore, room temperature mechanical properties were tested, with tests performed in both the transverse and longitudinal directions. The experimental data are shown in Table 1 below. Table 1 Properties of N6 pure nickel in hot-rolled state in Example 1

[0026] As can be seen from the relevant experimental data in Table 1, the mechanical properties in this embodiment meet the relevant provisions of GB / T2054-2023 "Nickel and Nickel Alloy Plates". This invention can make the rolled nickel plate have better performance.

[0027] This invention provides a complete process. First, the pure nickel forging billet is preheated. Simultaneously, by precisely controlling the temperature of the first heating stage, the second heating stage, the third heating stage, and the soaking stage, the drastic changes in the grain size inside the pure nickel forging billet are prevented. A combination of large reduction in rough rolling and small reduction in finish rolling is adopted. Dephosphorization treatment is carried out during rough rolling and finish rolling to remove oxide scale and exogenous particles, thereby improving surface quality. This makes the production process of N6 pure nickel strip controllable, significantly improving the yield and quality performance.

[0028] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A hot rolling control method based on 5mm N6 pure nickel thin strip, characterized in that, Specifically, the following steps are included: Step (1): The pure nickel forging billet is heated in a heating furnace. The heating is divided into 5 sections, namely the preheating section, the first heating section, the second heating section, the third heating section and the soaking section. The total heating time is maintained at 220-320 min. Step (2): The heated billet is conveyed to the roughing mill by the conveyor rollers. The roughing mill adopts 3 vertical rolling and 7 horizontal rolling. The initial rolling temperature is 1050-1150℃, the reduction rate of each roughing pass is 18%-23%, and the total deformation of the roughing is 75-80%. Step (3): The roughing billet is conveyed to the finishing rolling area through the intermediate roller table. The intermediate roller table is equipped with a heat insulation cover. The finishing rolling mill adopts 2 vertical rolling passes and 9 horizontal rolling passes. The reduction rate of each finishing rolling pass is 14%-17%, the total deformation of finishing rolling is 84-86%, the entry temperature of finishing rolling is controlled at 1000-1050℃, and the final rolling temperature is controlled at 850-900℃. Step (4): After finishing rolling, the strip is fed into the coiling machine via a flat chain to complete the coiling. Protective plates are installed on both sides of the flat chain for transport. The coiling temperature is 550-600℃.

2. The hot rolling control method based on 5mm N6 pure nickel thin strip according to claim 1, characterized in that: The thickness of the pure nickel forging billet in step (1) is 145-160 mm.

3. The hot rolling control method based on 5mm N6 pure nickel thin strip according to claim 1, characterized in that: The temperature of the preheating section in step (1) is 500-600℃.

4. The hot rolling control method based on 5mm N6 pure nickel thin strip according to claim 1, characterized in that: In step (1), the heating section is divided into three sections: the first heating section has a temperature of 800-900℃; the second heating section has a temperature of 850-1050℃; and the third heating section has a temperature of 970-1070℃.

5. The hot rolling control method based on 5mm N6 pure nickel thin strip according to claim 1, characterized in that: In step (1), the temperature of the soaking zone of the forging billet is 1080-1150℃.

6. The hot rolling control method based on 5mm N6 pure nickel thin strip according to claim 1, characterized in that: In step (1), the duration of the high-temperature section of the heating three sections and the homogenization section is 100-150 min.

7. The hot rolling control method based on 5mm N6 pure nickel thin strip according to claim 1, characterized in that: The rolling sequence of the roughing mill in step (2) is as follows: vertical rolling - horizontal rolling - horizontal rolling - vertical rolling - horizontal rolling - horizontal rolling - vertical rolling - horizontal rolling - horizontal rolling - horizontal rolling.

8. The hot rolling control method based on 5mm N6 pure nickel thin strip according to claim 1, characterized in that: The width of the rough-rolled billet exiting the stage in step (2) is 420-425 mm and the thickness is 34 mm.

9. The hot rolling control method based on 5mm N6 pure nickel thin strip according to claim 1, characterized in that: The rolling sequence of the finishing mill in step (3) is as follows: vertical rolling - horizontal rolling - horizontal rolling - vertical rolling - horizontal rolling - horizontal rolling - horizontal rolling - horizontal rolling - horizontal rolling - horizontal rolling - horizontal rolling - horizontal rolling - horizontal rolling.

10. The hot rolling control method based on 5mm thin N6 pure nickel strip according to claim 1, characterized in that: In steps (2) and (3), three dephosphorization water channels are opened in the rolling area. Specifically, the dephosphorization pressure of No. 1 is ≥22MPa and is located in the first vertical roll mill area of ​​the roughing mill; the dephosphorization pressure of No. 1 is ≥17MPa and is located in the third horizontal roll mill area of ​​the finishing mill; and the dephosphorization pressure of No. 2 is ≥12MPa and is located in the fifth horizontal roll mill area of ​​the finishing mill.

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