A method for improving surface indentation of high-strength thin strip produced by a twin roll casting process

Abstract

The present application belongs to the technical field of double-roller casting, and relates to a method for improving surface indentation of high-strength thin strip steel produced by a double-roller casting process. The method improves the surface indentation of high-strength thin strip steel produced by the double-roller casting process. The method optimizes the rolling lubrication and segmented cooling water process of the working roller, slows down the thermal fatigue, prolongs the service life of the working roller, and improves the surface quality and the qualification rate of the product.

Description

Technical Field

[0001] This invention belongs to the field of twin-roll casting and rolling technology, and relates to a method for improving the surface indentation of high-strength thin strip steel produced by twin-roll casting and rolling process. More specifically, this invention relates to a rolling method for producing high-strength thin strip steel using twin-roll thin strip casting and rolling technology, specifically a method for improving the surface indentation of high-strength thin strip steel during the twin-roll casting and rolling production process. Background Technology

[0002] Hot-rolled strip steel generally refers to coiled strip steel with a thickness of 1-20mm. It is widely used in industries such as automobiles, motors, chemicals, and shipbuilding, and is also used as a raw material for the production of cold-rolled, welded pipes, and cold-formed steel sections. In application, in addition to the usual mechanical properties, the requirements for surface quality and plate shape are becoming increasingly stringent, especially for thin strip steel products with a thickness of less than 2mm.

[0003] Traditional hot-rolled strip steel production typically employs a seven-stand hot continuous rolling mill, allocating the reduction amount per pass based on the total reduction rate. In contrast, twin-roll casting and rolling processes involve only one hot rolling step, with a single casting cycle lasting 8-10 hours and a maximum reduction rate of 60% per pass. The work rolls are continuously subjected to high-temperature conditions of 800-1000°C. Furthermore, when producing thinner products, the rolling force on the work rolls increases dramatically, leading to premature thermal fatigue on the roll surface, ultimately affecting product surface quality and reducing the yield rate.

[0004] Current domestic research on strip steel indentation problems mainly focuses on thick plates and cold-rolled plates. Patent document 202210527376.2 discloses a method for eliminating longitudinal indentations on new roll systems in hot straightening machines. This solution addresses the longitudinal indentation problem caused by new roll systems in hot straightening machines for thick plates. First, the end face chamfers of the support rolls of the new hot straightening roll system are ground and modified. Second, the rolling schedule is specially arranged, and a special straightening strategy is implemented based on the arrangement of the rolling schedule. This allows the new hot straightening roll system to quickly and efficiently achieve a stable running-in state, ensuring good surface quality of the steel plate. This is not in the same technical field as the problem this invention aims to solve: improving the surface indentation of high-strength thin strip steel produced by twin-roll casting and rolling processes.

[0005] Patent document 202211191140.2 discloses a control device for preventing strip indentation. This solution improves the quality of cold-rolled strip products, avoids indentation defects caused by agglomeration on the surface of the squeeze rolls, and prevents indentation caused by foreign objects pressing into the roll surface, which is a different type of defect that this invention aims to solve.

[0006] It is evident that providing a method to improve the surface indentation of high-strength thin strip steel produced by twin-roll casting and rolling is a problem that still faces in this field. In particular, there is no mature technical solution yet for how to slow down the thermal fatigue rate of the work roll surface through optimization of rolling lubrication and work roll cooling processes, thereby ensuring the surface quality of the strip steel. Summary of the Invention

[0007] Based on the above background technology, the purpose of this invention is to provide a method for improving the surface indentation of high-strength thin strip steel produced by twin-roll casting and rolling process. The method of this invention, by optimizing the rolling lubrication process and the work roll cooling process, slows down the thermal fatigue rate of the work roll surface, ensures the surface quality of the strip steel, and reduces the rejection rate of indentation in high-strength thin strip steel.

[0008] More specifically, the present invention adopts the following technical solution.

[0009] According to one aspect of the present invention, a method for improving the surface indentation of high-strength thin strip steel produced by twin-roll casting and rolling process is provided, the method comprising the following steps:

[0010] (1) Thin strip continuous casting: using twin-roll casting process to produce strips with a thickness of 1.9~2.2mm;

[0011] (2) Hot rolling process: The cast strip is hot rolled in one pass to produce high-strength thin strip steel with a thickness of 0.9~1.2mm. The temperature of the cast strip before hot rolling is controlled at 800~980℃, and the hot rolling reduction rate is controlled at 40%~60%.

[0012] In the hot rolling process, a rolling lubrication process and a segmented cooling process for the work rolls are used to slow down the surface deterioration of the work rolls. Specifically:

[0013] (a) Use an oil-water mixture as the lubricating medium. The water flow rate is controlled at 12~15L / min, and the lubricating oil flow rate is controlled at 100±10mL / min. Ensure that the oil and water are mixed evenly and that the temperature of the oil-water mixture is controlled at 40~45℃ to avoid the grease from hardening and insufficient mixing due to excessively low temperature.

[0014] (b) The hot rolling work rolls are cooled in sections by a cooling system, the cooling system including a first cooling system acting on the upper work roll and a second cooling system acting on the lower work roll;

[0015] Both the first cooling system and the second cooling system are provided with at least three rows of nozzles distributed radially along the working roll. Each row of nozzles includes multiple nozzles distributed along the length of the working roll to spray water onto the surface of the working roll for cooling. The water flow rate of each nozzle is controlled at 4000±200L / min, and the cooling water pressure is controlled at 3.5~4.5bar.

[0016] Wherein, the outermost radial row of at least three rows of nozzles in the first cooling system is a selective nozzle, and the outermost radial row of at least three rows of nozzles in the second cooling system is a selective nozzle. The method further includes controlling the opening or closing of the selective nozzles according to the shape of the cast strip and the local temperature distribution, increasing the local cooling water of the work roll, ensuring uniform temperature and consistent thermal expansion along the length of the work roll, and avoiding overheating.

[0017] According to the method for improving the twin-roll casting process for producing high-strength thin strip steel surface indentation of the present invention, preferably, the first cooling system includes three rows of nozzles, the outermost row being selective nozzles and the other two rows being normally open nozzles; the second cooling system includes three rows of nozzles, the outermost row being selective nozzles and the other two rows being normally open nozzles.

[0018] According to the method of improving the twin-roll casting and rolling process for producing surface indentations of high-strength thin strip steel according to the present invention, preferably, each row of nozzles in the first cooling system and the second cooling system includes 36 to 38 nozzles, and the nozzles are evenly distributed along the length of the work roll.

[0019] According to the method for improving the twin-roll casting process for producing surface indentations of high-strength thin strip steel according to the present invention, preferably, each row of nozzles in the first cooling system and the second cooling system includes 37 nozzles.

[0020] In the method for improving the twin-roll casting and rolling process for producing surface indentations of high-strength thin strip steel according to the present invention, preferably, the water flow rate in the lubricating medium during hot rolling is controlled at 14~15L / min.

[0021] The method for producing high-strength thin strip steel with surface indentation according to the present invention, wherein the lubricating oil flow rate in the hot-rolled lubricating medium is preferably controlled at 100~110mL / min.

[0022] The method for producing surface indentations of high-strength thin strip steel according to the present invention, wherein the temperature of the oil-water mixture in the lubricating medium of hot rolling is preferably controlled at 42~45°C.

[0023] In the method for improving the twin-roll casting process for producing surface indentations of high-strength thin strip steel according to the present invention, preferably, the cooling water pressure of each nozzle is controlled at 3.8~4.2 bar.

[0024] In the method for improving the twin-roll casting process of the present invention for producing surface indentations of high-strength thin strip steel, preferably, the water flow rate of each nozzle is controlled at 4000~4200L / min.

[0025] The method for producing surface indentation of high-strength thin strip steel according to the present invention, wherein preferably, the indentation rejection rate of the high-strength thin strip steel produced by the method is not higher than 1%.

[0026] Beneficial technical effects

[0027] Compared with the prior art, the technical concept and corresponding technical solution of the present invention can achieve at least the following beneficial technical effects:

[0028] The method of the present invention, under existing production conditions, does not require any additional equipment, but effectively improves the problem of surface indentation in high-strength thin strip steel by optimizing the relevant parameters of rolling lubricating oil and segmented cooling water for work rolls.

[0029] The method of the present invention is easy to operate, has low process improvement costs, and can significantly improve product surface quality and single-cast yield of thin-gauge products. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention.

[0031] Figure 1 This is a schematic diagram of surface indentation on high-strength thin strip steel in the prior art.

[0032] Figure 2 This is a schematic diagram of the surface of a high-strength thin strip steel according to an embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram of the segmented cooling water distribution of the rolls according to an embodiment of the present invention.

[0034] The reference numerals in the attached figures refer to the following:

[0035] 1: Support roller; 2: Work roller;

[0036] 3, 4, 5: Segmented cooling water manifolds for the upper working roller;

[0037] 6, 7, 8: Segmented cooling water manifolds for the lower work roll;

[0038] 9: Water-cutting plate; 10: High-strength thin strip steel. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0040] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0041] The following are embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention. All other embodiments that can be 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.

[0042] The technical solution of the present invention will be further described in detail below through specific embodiments and comparative examples.

[0043] Example

[0044] In this embodiment of the invention, a twin-roll casting and rolling process is used to produce high-strength thin strip steel. The cast strip thickness in this embodiment is 2.0 mm, and the rolled strip thickness is 1.0 mm.

[0045] In this embodiment, the rolling lubricant flow rate is 15 mL / min, and the cooling water flow rate is 100 L / min.

[0046] In this embodiment, the temperature after oil-water mixing is 43°C, the volume of segmented cooling water is 4200L, and the cooling water pressure is 4bar.

[0047] Figure 2 This is a schematic diagram of the surface of the high-strength thin strip steel according to this embodiment. Figure 3 This is a schematic diagram of the segmented cooling water distribution of the rolls in this embodiment.

[0048] In this embodiment, the indentation rejection rate of the final high-strength thin strip steel product is only 0.8%.

[0049] Table 1 shows the main technical parameters of this embodiment. The comparative example shows the process parameters for producing high-strength thin strip steel by twin-roll casting under conventional conditions. Figure 1 This is a schematic diagram illustrating the surface indentation problem that existing technologies need to address in high-strength thin strip steel.

[0050] Table 1. Key process parameters of comparative examples and embodiments

[0051]

[0052] As can be seen from Table 1, the rejection rate of high-strength thin strip steel in the comparative example under conventional production conditions was 4.5%, while the rejection rate of indentation of high-strength thin strip steel in this embodiment decreased to 0.8%, which significantly reduced the product indentation rejection rate and improved the surface quality of the product.

[0053] The above description is only a specific embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for improving the surface indentation of high-strength thin strip steel produced by twin-roll casting and rolling process, characterized in that, The method includes the following steps: (1) Thin strip continuous casting: using twin-roll casting process to produce strips with a thickness of 1.9~2.2mm; (2) Hot rolling process: The cast strip is hot rolled in one pass to produce high-strength thin strip steel with a thickness of 0.9~1.2mm. The temperature of the cast strip before hot rolling is controlled at 800~980℃, and the hot rolling reduction rate is controlled at 40%~60%. In the hot rolling process: (a) Use an oil-water mixture as the lubricating medium, with the water flow rate controlled at 12~15L / min, the lubricating oil flow rate controlled at 100±10mL / min, and the temperature of the oil-water mixture controlled at 40~45℃; (b) The hot rolling work rolls are cooled in sections by a cooling system, the cooling system including a first cooling system acting on the upper work roll and a second cooling system acting on the lower work roll; Both the first cooling system and the second cooling system are provided with at least three rows of nozzles distributed radially along the working roll. Each row of nozzles includes multiple nozzles distributed along the length of the working roll to spray water onto the surface of the working roll for cooling. The water flow rate of each nozzle is controlled at 4000±200L / min, and the cooling water pressure is controlled at 3.5~4.5bar. Wherein, the outermost radial row of at least three rows of nozzles in the first cooling system is a selective nozzle, and the outermost radial row of at least three rows of nozzles in the second cooling system is a selective nozzle, and the method further includes controlling the opening or closing of the selective nozzles according to the shape of the cast strip and the local temperature distribution.

2. The method for improving the surface indentation of high-strength thin strip steel produced by twin-roll casting and rolling process according to claim 1, characterized in that: The first cooling system includes three rows of nozzles, with the outermost row being selective nozzles and the other two rows being normally open nozzles; The second cooling system includes three rows of nozzles, with the outermost row being selective nozzles and the other two rows being normally open nozzles.

3. The method for improving the surface indentation of high-strength thin strip steel produced by twin-roll casting and rolling process according to claim 1 or 2, characterized in that: Each row of nozzles in the first and second cooling systems includes 36 to 38 nozzles, which are evenly distributed along the length of the working roller.

4. The method for improving the surface indentation of high-strength thin strip steel produced by twin-roll casting and rolling process according to claim 3, characterized in that: Each row of nozzles in both the first and second cooling systems includes 37 nozzles.

5. The method for improving the surface indentation of high-strength thin strip steel produced by twin-roll casting and rolling process according to claim 1, characterized in that: In the lubricating medium of hot rolling, the water flow rate is controlled at 14~15L / min.

6. The method for improving the surface indentation of high-strength thin strip steel produced by twin-roll casting and rolling process according to claim 1, characterized in that: In hot rolling, the lubricating oil flow rate is controlled at 100~110mL / min.

7. The method for improving the surface indentation of high-strength thin strip steel produced by twin-roll casting and rolling process according to claim 1, characterized in that: In hot rolling, the temperature of the oil-water mixture is controlled at 42~45℃.

8. The method for improving the surface indentation of high-strength thin strip steel produced by twin-roll casting and rolling process according to claim 1, characterized in that: The cooling water pressure for each nozzle is controlled at 3.8~4.2 bar.

9. The method for improving the surface indentation of high-strength thin strip steel produced by twin-roll casting and rolling process according to claim 1, characterized in that: The water flow rate for each nozzle is controlled at 4000~4200L / min.

10. The method for improving the surface indentation of high-strength thin strip steel produced by twin-roll casting and rolling process according to claim 1 or 2, characterized in that: The indentation rejection rate of the high-strength thin strip steel produced by the method is no higher than 1%.

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