A cold rolling method for a high-precision extra-thin strip special steel

Abstract

The application provides a cold rolling method of a high-precision and extremely thin strip special steel, and the cold rolling method comprises the following steps: (1) the thickness of the steel coil before cold rolling is 2.5mm-3.0mm, and an acid pickling-continuous rolling combined unit and a twenty-roller combined cold rolling production method are adopted; (2) a secondary cold rolling method is adopted, a five-rack four-roller continuous rolling is used for first cold rolling to roll the raw material to an intermediate thickness, and a twenty-roller rolling mill reversible rolling mill is used for second cold rolling to roll the intermediate thickness to a target thickness; (3) in the first cold rolling, the five-rack four-roller rolling mill rolls the raw material from the thickness of 2.5mm-3.0mm to the intermediate thickness of 0.5mm-0.8mm, and the total reduction rate is 65%-80%; (4) the second cold rolling adopts the twenty-roller reversible rolling mill three-pass cold rolling rolling; the reduction rate of the first and second passes is controlled to be 30%-36%, and the reduction rate of the third pass is controlled to be 20%-28%; and (5) the thickness of the rolled product is 0.19mm-0.25mm, and the thickness control precision is ±1um.

Description

Technical Field

[0001] This invention relates to the field of steel rolling, specifically to a cold rolling method for high-precision ultra-thin strip special steel, particularly a cold rolling method for thin-gauge high-precision battery steel. Background Technology

[0002] For special steels with a thickness of less than 0.25mm (such as battery steel), traditional five-stand continuous rolling mills have limited control capabilities, resulting in limited control over thickness and strip thickness variation, making it impossible to obtain ultra-thin products that meet high-precision thickness requirements. Alternatively, traditional pickling and 20-roll mill production processes are relatively expensive and time-consuming. Neither approach can simultaneously meet the requirements of low production cost and high strip precision.

[0003] In summary, the existing technology has the following problems: high-precision ultra-thin strip steel with a thickness of less than 0.25mm has a slow production pace, high cost and low production efficiency. Summary of the Invention

[0004] This invention provides a cold rolling method for high-precision ultra-thin strip steel for special purposes, in order to solve the problems of slow production pace, high cost and low production efficiency of high-precision ultra-thin strip steel with a thickness of less than 0.25mm.

[0005] Therefore, this invention proposes a cold rolling method for high-precision ultra-thin special steel strips, wherein the high-precision ultra-thin special steel strip is, for example, battery steel with a thickness of less than 0.25 mm. The cold rolling method for the high-precision ultra-thin special steel strip includes the following steps:

[0006] (1) The thickness of the steel coil before cold rolling is 2.5mm to 3.0mm, and the cold rolling production method is adopted by pickling-continuous rolling combined unit and twenty roll combination;

[0007] (2) The two-stage cold rolling method is adopted. The first cold rolling uses a 5-stand four-roll continuous rolling mill to roll the raw material to the intermediate thickness. The second cold rolling uses a 20-roll reversible rolling mill to roll the intermediate thickness to the target thickness.

[0008] (3) In the first cold rolling, the 5-stand four-high mill adopts the conventional low-carbon steel production process, which changes the raw material thickness from...

[0009] Rolled from 2.5mm to 3.0mm to an intermediate thickness of 0.5mm to 0.8mm, with a total reduction rate of 65% to 80%;

[0010] (4) The second cold rolling is performed using a 20-roll reversible rolling mill in three passes; among which...

[0011] 4.1) Control the reduction rate of the first and second passes to 30%–36%, and the reduction rate of the third pass to 20%–28%;

[0012] 4.2) Select different roughness of the 20-roll mill work rolls according to the annealing process;

[0013] (5) The thickness of the rolled product is between 0.19 mm and 0.25 mm. The thickness control accuracy is ±1 μm.

[0014] After using this invention, finished steel strips with good surface quality, high dimensional accuracy, and low variation within the same strip are obtained. Moreover, compared to traditional pickling and 20-roll mill production, this method saves production time and costs, reducing costs by nearly 80 yuan / ton compared to traditional methods and improving production efficiency. The successful application of this new battery steel technology signifies that Liuzhou Steel now possesses the capability to produce ultra-thin special steel strips, further increasing the proportion of high value-added products and creating considerable economic benefits for the company. On the other hand, it also expands the market for special steel grades and enhances product competitiveness. Detailed Implementation

[0015] To provide a clearer understanding of the technical features, objectives, and effects of this invention, the invention is now described.

[0016] Example 1

[0017] High-precision, ultra-thin strip steel with a carbon content of <0.03% was produced using a pickling-five-roll mill and a Sendzimir 20-roll mill. The specific chemical composition of the steel plate in this embodiment is shown in Table 1.

[0018] Table 1 Chemical composition (weight percentage %)

[0019]

[0020] The specific steps are as follows:

[0021] 1) The smelting and hot rolling processes follow the conventional production methods for low-carbon steel, and the thickness of the steel coil before cold rolling is 2.7 mm.

[0022] 2) The strip steel is rolled to an intermediate thickness of 0.7 mm using a pickling-pickling-five-rolling combined unit in a single cold rolling process;

[0023] 3) Continue to use the 20-roll mill secondary cold rolling method to perform continuous reversible three-pass cold rolling to the target thickness;

[0024] 3.1) Use a work roller (φ65mm) with a roughness ≥1.2μm to prevent adhesion defects caused by subsequent annealing processes.

[0025] 3.2) Control the reduction rate between 18% and 40%, with the first pass reduction rate at 32.9%, the second pass at 31.9%, and the final pass at 25.0%. Refer to Table 1 for specific reduction rates.

[0026] 3.3) During rolling, control the unit tension on the inlet side of each pass to be between 5 and 16 kg / mm. 2 The outlet lateral tension is between 10 and 26 kg / mm. 2 The unit tension on the inlet side of the first pass is 7–9 kg / mm². 2 The unit tension on the outlet side is 15-18 kg / mm. 2 For specific allocation details, please refer to Table 1.

[0027] 3.4) The maximum stable rolling speed can reach 800 m / min, and the thickness of the rolled product is 0.24 mm;

[0028] 4) Subsequent processes are carried out according to conventional processes. It should be noted that if the board surface requires a smooth surface with low roughness, the working roller of the leveling machine needs to be a smooth roller with a roughness of <0.5μm in order to reduce the surface roughness of the board to below 0.6μm.

[0029] The final product of this embodiment is excellent, with good stamping performance and a hardness value of HR30T of 52.8. Compared with the traditional method, this method can save nearly 80 yuan / ton in cost. The specific analysis is shown in Table 3.

[0030] Example 2

[0031] Low-carbon, high-precision, ultra-thin strip steel for special applications was rolled using a pickling-five-roll mill and a Sendzimir 20-roll mill. The specific chemical composition of the steel plate in this embodiment is shown in Table 2.

[0032] Table 2 Chemical composition (weight percentage %)

[0033]

[0034] The specific steps are as follows:

[0035] 1) The smelting and hot rolling processes follow the conventional production methods for low-carbon steel, and the thickness of the steel coil before cold rolling is 2.5 mm.

[0036] 2) The strip steel is rolled to an intermediate thickness of 0.6 mm using a pickling-pickling-five-rolling combined unit in a single cold rolling process;

[0037] 3) Continue to use the 20-roll mill secondary cold rolling method to perform continuous reversible three-pass cold rolling to the target thickness;

[0038] 3.1) Use a work roller (φ65mm) with a roughness ≥1.2μm to prevent adhesion defects caused by subsequent annealing processes.

[0039] 3.2) Control the reduction rate between 18% and 40%, with the first pass reduction rate at 35.0%, the second pass at 33.3%, and the final pass at 26.9%. Refer to Table 4 for specific reduction rates.

[0040] 3.3) During rolling, control the unit tension on the inlet side of each pass to be between 5 and 16 kg / mm. 2 The outlet lateral tension is between 10 and 26 kg / mm. 2 The unit tension on the inlet side of the first pass is 7–9 kg / mm². 2 The unit tension on the outlet side is 15-18 kg / mm. 2 For specific allocation details, please refer to Table 2.

[0041] 3.4) The maximum stable rolling speed can reach 800m / min, and the thickness of the rolled product is 0.19mm.

[0042] 4) Subsequent processes are carried out according to conventional processes. It should be noted that if the board surface requires a smooth surface with low roughness, the working roller of the leveling machine needs to be a smooth roller with a roughness of <0.5μm in order to reduce the surface roughness of the board to below 0.6μm.

[0043] The final product of this embodiment is excellent, with good stamping performance and a hardness value of HR30T of 53.2. Similarly, this method can save nearly 80 yuan / ton in cost compared with the traditional method.

[0044] Table 3. Pressing and dispensing regime for Example 1 (finished product thickness 0.24 mm).

[0045]

[0046] Table 4. Pressing and Distributing System for Example 2 (Finished Product Thickness: 0.19 mm)

[0047]

[0048]

[0049] Table 5: Cost of 5 Tons of Steel (Unit: Yuan / Ton)

[0050]

[0051] In summary, although the new process of this invention increases the number of five stands and four rolls in continuous rolling, the number of 20 roll passes is greatly reduced. The high-precision ultra-thin strip produced by cold rolling according to the processes in Examples 1 and 2 has a straight and stable strip shape, a thickness accuracy of ±1μm, and good performance, as shown in Table 6. The cost per ton of steel can be reduced by 120 yuan, as shown in Table 5.

[0052] Table 6 Mechanical Performance Requirements of Finished Products

[0053]

[0054] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. The various components of the present invention can be combined with each other without conflict. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A cold rolling method for high-precision ultra-thin strip special steel, characterized in that, The cold rolling method is specifically as follows: This high-precision, ultra-thin strip special steel is produced by using a pickling-five-roll mill and a Sendzimir 20-roll mill. The chemical composition, by weight percentage (%), is: C < 0.03%, Si ≤ 0.03%, Mn: 0.10-0.25%, P ≤ 0.022%, S ≤ 0.015%, Alt: 0.020-0.050%, Ti ≤ 0.010%, N ≤ 0.0028%. The residual Cu, Cr, and Ni contents are each no greater than 0.10%, and the As content is no greater than 0.040%. The steel coil was 2.7 mm thick before cold rolling; The strip steel is rolled to an intermediate thickness of 0.7 mm using a pickling-five-rolling combined unit in a single cold rolling process. The target thickness is achieved by using a Sendzimir 20-roll mill double cold rolling method to perform continuous reversible three-pass cold rolling. The secondary cold rolling process uses φ65mm work rolls with a roughness ≥1.2μm to prevent adhesion defects caused by subsequent annealing. The first pass reduction rate was controlled at 32.9%, the second pass reduction rate at 31.9%, and the final pass reduction rate at 25.0%. During rolling, the unit tension on the inlet side is controlled at 5~16 kg / mm ​​for each pass. 2 The unit tension on the outlet side is 10~26 kg / mm. 2 The unit tension on the inlet side of the first pass is 7~9 kg / mm. 2 The unit tension on the outlet side is 15~18 kg / mm. 2 ; The maximum stable rolling speed is 800 m / min, and the thickness of the rolled product is 0.24 mm.

2. A cold rolling method for high-precision ultra-thin strip special steel, characterized in that, The cold rolling method is specifically as follows: This high-precision, ultra-thin strip special steel is produced by using a pickling-five-roll mill and a Sendzimir 20-roll mill. The chemical composition, by weight percentage (%), is: C 0.05~0.07, Si≤0.03, Mn: 0.10-0.25, P≤0.022, S≤0.015, Alt: 0.020-0.050, Ti≤0.010, N≤0.0060. The residual Cu, Cr, and Ni contents are each no greater than 0.10, and the As content is no greater than 0.

040. The steel coil was 2.5 mm thick before cold rolling; The strip steel is rolled to an intermediate thickness of 0.6 mm using a pickling-five-rolling combined unit in a single cold rolling process. The target thickness is achieved by using a Sendzimir 20-roll mill double cold rolling method to perform continuous reversible three-pass cold rolling. The secondary cold rolling process uses φ65mm work rolls with a roughness ≥1.2μm to prevent adhesion defects caused by subsequent annealing. The first pass reduction rate was controlled at 35.0%, the second pass reduction rate at 33.3%, and the final pass reduction rate at 26.9%. During rolling, the unit tension on the inlet side is controlled at 5~16 kg / mm ​​for each pass. 2 The unit tension on the outlet side is 10~26 kg / mm. 2 The unit tension on the inlet side of the first pass is 7~9 kg / mm. 2 The unit tension on the outlet side is 15~18 kg / mm. 2 ; The maximum stable rolling speed is 800 m / min, and the thickness of the rolled product is 0.24 mm.

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