A method for controlling surface scratch defects of ultra-low carbon hot-rolled strip steel

Abstract

The application discloses a control method for surface scratch defect of ultra-low-carbon hot-rolled strip steel, which comprises the following measures: increasing a rough rolling head sledging coefficient; increasing rough rolling front two pass reduction; adjusting rough rolling last two pass biting speed and rolling speed; reducing rough rolling last two pass reduction; and reducing rough rolling last two pass reduction amount difference. The control method is simple and easy to operate, and improves the scratch defect in the hot continuous rolling strip steel production process, and the scratch defect is reduced from 45.14 tons / month to 25.07 tons / month, and the improvement effect is remarkable.

Description

Technical Field

[0001] This invention relates to the field of hot-rolled strip steel technology, and in particular to a method for controlling surface scratch defects in ultra-low carbon hot-rolled strip steel. Background Technology

[0002] In recent years, as the steel industry as a whole has moved towards high-quality development, downstream processes have increasingly demanded higher quality strip steel. Surface defects in strip steel necessitate rework, and in some cases, downgrade the product or even classify it as scrap, increasing production costs and hindering the company's high-quality development strategy. Scratches on hot-rolled strip steel are a common surface defect that severely affects its use in downstream processes; therefore, it must be controlled during production.

[0003] Scratches are a common defect in hot-rolled strip steel production. They are caused by friction between the rolled piece and mechanical equipment components due to relative movement. Their length, width, and depth vary, and they mainly appear at the beginning and end of the strip along the rolling direction. Scratches at high temperatures have a thin layer of iron oxide scale, appearing blackish-gray. During continuous production, scratches may be slightly flattened, or they may contain iron oxide scale or expose the inner metal layer. Scratches cannot be effectively removed during pickling. Coils with scratches need to be ground before production or downgraded.

[0004] In view of this, the present invention is proposed to solve the above-mentioned technical problems existing in the prior art. Summary of the Invention

[0005] The main objective of this invention is to provide a method for controlling surface scratches on ultra-low carbon hot-rolled strip steel, so as to solve the problem that scratches on the surface of hot-rolled strip steel limit its application.

[0006] According to one aspect of the present invention, a method for controlling surface scratch defects in ultra-low carbon hot-rolled strip steel is provided, comprising the following measures:

[0007] Increase the sled coefficient at the head of the rough rolling mill;

[0008] Increase the reduction rate in the first two passes of rough rolling;

[0009] Adjust the bite speed and rolling speed of the last two passes of rough rolling;

[0010] Reduce the reduction rate in the last two passes of rough rolling; and

[0011] Reduce the difference in reduction between the last two passes of rough rolling.

[0012] According to one embodiment of the present invention, the reduction rate of the first two roughing passes is ≥25%.

[0013] According to one embodiment of the present invention, the bite speed of the last two passes of the rough rolling is set to 2.5 m / s-3.0 m / s.

[0014] According to one embodiment of the present invention, the rolling speed is set to 4.5 m / s-5.0 m / s.

[0015] According to one embodiment of the present invention, the roughing head sled coefficient is increased by 2%-4% compared to other transitional steel grades.

[0016] According to one embodiment of the present invention, the reduction rate of the last two roughing passes is ≤30%.

[0017] According to one embodiment of the present invention, the difference in reduction between the last two passes of the roughing mill is ≤13mm.

[0018] By adopting the above technical solutions, the present invention has the following advantages over the prior art: (1) reducing the reduction rate of subsequent passes by increasing the reduction rate; (2) reducing the relative sliding of the head to the roller table by adjusting the rolling speed; (3) reducing the degree of head tilting, thus reducing the interference between the strip and the roller table and transition plate in some areas; (4) controlling the strip shape by reducing the reduction rate; (5) optimizing the strip shape by reducing the difference in reduction amount, thus avoiding the relative sliding between the strip and the mechanical equipment caused by poor strip shape. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some implementation examples of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The diagram illustrates the improvement effect of a method for controlling surface scratch defects in ultra-low carbon hot-rolled strip steel according to an exemplary embodiment of the present invention. 。 Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0022] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0023] like Figure 1 As shown, a method for controlling surface scratch defects in ultra-low carbon hot-rolled strip steel includes the following measures:

[0024] Increase the sled coefficient at the head of the rough rolling mill;

[0025] Increase the reduction rate in the first two passes of rough rolling;

[0026] Adjust the bite speed and rolling speed of the last two passes of rough rolling;

[0027] Reduce the reduction rate in the last two passes of rough rolling; and

[0028] Reduce the difference in reduction between the last two passes of rough rolling.

[0029] The roughing mill head sled coefficient is increased by 2%-4% compared to other transition steel grades. The average head sled coefficient for other transition steel grades is set at 3.2%, and the average roughing mill head sled coefficient after adjustment is set at 5.2%-7.2%. By reducing the degree of head tilting, local interference between the strip and the roller table and transition plate is eliminated.

[0030] The reduction rate of the first two roughing passes is controlled to be ≥25%, thereby reducing the reduction rate of subsequent passes by increasing the reduction rate.

[0031] The bite speed for the last two roughing passes is set to 2.5 m / s-3.0 m / s, and the rolling speed is set to 4.5 m / s-5.0 m / s. By changing the rolling speed, the relative slippage between the head and the roller table is reduced. Operators can adjust the speed settings according to actual needs.

[0032] The reduction rate of the last two roughing passes is controlled to be ≤30%, thereby controlling the strip shape by reducing the reduction rate.

[0033] The difference in reduction between the last two passes of the rough rolling is controlled to be ≤13mm. By reducing the difference in reduction, the strip shape is optimized, and relative slippage between the strip and the mechanical equipment due to poor strip shape is avoided.

[0034] In actual production, operators will decide the number of measures in this invention to use based on the actual situation, and may use one or more of them.

[0035] The improvement effects of various embodiments of the present invention on surface scratch defects of ultra-low carbon hot-rolled strip steel are shown in Table 1.

[0036] Table 1

[0037]

[0038] like Figure 1 As shown, compared to the control method using proportional parameters before April 2021, since April 2021, when the scratch defects of ultra-low carbon strip steel were controlled according to the aforementioned control method, the amount of scratch defects in strip steel has been significantly reduced. Specifically, the scratch defects have decreased from 45.14 tons / month to 25.07 tons / month, showing a significant improvement effect.

[0039] The control method of the present invention is simple and easy to operate, improves the scratch defects in the hot strip steel production process, and has a significant improvement effect, making it suitable for widespread use.

[0040] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for controlling surface scratch defects in ultra-low carbon hot-rolled strip steel, characterized in that, Including the following measures: The roughing mill head sled coefficient is increased by 2%-4% compared to other transitional steel grades. The average head sled coefficient for other transitional steel grades is set at 3.2%, and the adjusted average roughing mill head sled coefficient is set at 5.2%. 7.2%; Increase the reduction rate of the first two passes of rough rolling, wherein the reduction rate of the first two passes of rough rolling is ≥25%; Adjust the bite speed and rolling speed of the last two passes of roughing milling. The bite speed of the last two passes of roughing milling is set to 2.5 m / s-3.0 m / s, and the rolling speed is set to 4.5 m / s-5.0 m / s. Reduce the reduction rate of the last two passes of roughing milling, wherein the reduction rate of the last two passes of roughing milling is ≤30%; and Reduce the difference in reduction between the last two passes of rough rolling, wherein the difference in reduction between the last two passes of rough rolling is ≤13mm.

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