A method for improving the surface quality of continuous casting billets based on online casting roller friction

Abstract

The present invention relates to the field of steelmaking and continuous casting technology, and more particularly to a method for improving the surface quality of continuously cast billets based on the friction of online casting rolls. The method comprises setting the amount of light reduction rolls and the friction distribution coefficient of the continuous cast billet as it passes through the light reduction rolls; and setting the amount of reduction rolls and the friction distribution coefficient of the continuous cast billet as it passes through the online casting rolls to prevent the occurrence of transverse cracks in the billet corners. To avoid crack defects, the present invention improves the surface quality of the billet by increasing the rounded corners of the billet and reducing the driving force distribution coefficient of the reduction rolls.

Description

Technical Field

[0001] The invention relates to the technical field of steelmaking and continuous casting, and in particular to a method for improving the surface quality of continuous casting billets based on the friction force of online casting rolls. Background Art

[0002] Continuously cast square billets are mainly used to provide production billets for the processing of high-quality steels such as wires and bars. The steel types mainly include cord steel, bearing steel, spring steel, cold heading steel, gear steel, rebar, etc. Among them, high-end cord steel, bearing steel, spring steel, etc. Continuously cast square billets are heated and rolled twice. The first heating rolling is usually called "opening the billet", which rolls the large-sized billet into a small-sized billet, which plays a role in squeezing the core and promoting carbon diffusion; the second heating rolling rolls the small-sized billet after "opening the billet" into the final product.

[0003] Existing patents mainly target the core defects of continuous casting billets. For example, a continuous casting method for improving the internal quality of continuous casting billets improves the internal quality of continuous casting billets by light reduction + online casting and rolling, and reduces the core segregation and loose shrinkage cavities of continuous casting billets. Although this method can improve the internal surface quality of the billet, the reduction roller will cause the surface of the billet to cool rapidly, forming thermal stress and mechanical stress, which can easily cause transverse cracks to form at the corners of the billet surface. Summary of the Invention

[0004] In view of the shortcomings of the existing algorithms, the present invention improves the surface quality of the billet by increasing the radius of the billet surface to increase the ability of the corners to resist tensile stress and reducing the distribution coefficient of the driving force of the pressing roller in order to avoid crack defects.

[0005] The technical solution adopted by the present invention is: a method for improving the surface quality of continuous casting billets based on the friction force of online casting rolls, comprising the following steps:

[0006] Step 1: Set the light pressure amount and friction force distribution coefficient K of the continuous casting billet passing through the light pressure roller i ;

[0007] First, the temperature of the geometric center of the ingot is calculated, denoted as Tx. Based on this temperature, the position of the ingot's center is calculated, and a soft reduction roll is used to gently reduce the ingot. The purpose is to squeeze out the impurity-rich molten steel in the ingot's center and reduce the degree of center segregation of the ingot.

[0008] Through continuous extrusion, the upward movement of the core molten steel is promoted. The range of light reduction is determined by the temperature Tx. For a specific type of steel, there is a fixed solidus temperature Ts and a fixed liquidus temperature Tl. Therefore, the core solid phase fraction fs of the ingot can be calculated based on Tx.

[0009] Step 2: Setting the roll reduction and friction distribution coefficient of the continuous casting billet to avoid the occurrence of transverse cracks at the corners of the billet;

[0010] Furthermore, when the continuous casting billet is a billet of less than 200 mm, the fillet radius of the continuous casting billet is set to 10-20 mm; when the continuous casting billet is a billet of 200 mm-400 mm, the fillet radius of the continuous casting billet is set to 20-50 mm.

[0011] Furthermore, when the online casting roll reduction is [10, 20), the online casting roll friction force distribution coefficient k j is [70,90); when the online casting reduction is [20,30), the online casting roller friction distribution coefficient k j is [50,70); when the online casting reduction is [30,50), the online casting roller friction distribution coefficient k j is [20,50).

[0012] After the soft reduction is completed and solidification has occurred, the ingot is rapidly cast and rolled online using online casting rollers. The online casting rollers consist of a pair, one on the upper and one on the lower surfaces, in order to fit the loose shrinkage cavities in the core of the ingot and improve the density of the core of the ingot.

[0013] After the billet is pressed down, the contact area between the online casting roller and the billet increases due to the rapid and large pressing of the online casting roller, which will cause the rapid cooling of the billet surface, which makes it easy for the billet surface temperature to quickly enter the third brittle zone. At the same time, due to the increase in the friction force of the online casting roller on the billet, it is easy for corner transverse cracks to occur at the corners of the billet.

[0014] Since the contact surface between the online casting roller and the billet is large, when the pressing force increases, the surface friction of the online casting roller on the billet will be too large. Therefore, it is necessary to control the friction distribution between the online casting roller and the billet. Usually, the light pressing roller and the online casting roller evenly distribute the total friction force. The friction coefficients of the light pressing roller and the online casting roller are set as k i and k j , the corresponding friction force is F i and F j , usually, k i and k j are all set to 100. When the online casting roll performs a large reduction, its friction force F j The situation will increase, and excessive driving force will cause transverse cracks at the corners. Therefore, it is necessary to reduce the friction of the online casting roller to reduce the risk of transverse cracks at the corners. By setting the friction distribution coefficient of the online casting roller, the contact area between the corners and the rollers is reduced, and the tensile stress resistance of the corners of the insulate is improved.

[0015] Beneficial effects of the present invention:

[0016] Surface defects can be reduced by increasing the R angle of the billet and the distribution of friction force. The method is simple and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flow chart of a method for improving the surface quality of continuous casting billets based on online casting roll friction of the present invention;

[0018] Figure 2 Schematic diagram of soft reduction and online casting and rolling according to the present invention;

[0019] Figure 3 This is a schematic diagram of transverse cracks in the corners of continuous casting billets;

[0020] Figure 4 It is a schematic cross-sectional view of the rounded corner continuous casting billet of the present invention. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. This figure is a simplified schematic diagram, which only illustrates the basic structure of the present invention in a schematic manner, and therefore only shows the components related to the present invention.

[0022] like Figure 1 As shown, a method for improving the surface quality of continuous casting billets based on online casting roll friction comprises the following steps:

[0023] S1. Setting the light pressure amount and friction force distribution coefficient of the continuous casting billet passing through the light pressure roller;

[0024] like Figure 2 Schematic diagram of soft reduction and online casting and rolling structure.

[0025] S2. Set the continuous casting billet rolling roll reduction and friction distribution coefficient to avoid the occurrence of transverse cracks in the billet corners; Figure 3 、 4 Schematic diagrams of rounded corner continuous casting billets and corner transverse cracks respectively.

[0026] The friction force distribution coefficient is calculated from the motor torque.

[0027] Example 1

[0028] For 160mm billet, the billet corner radius is set to 11mm, the total reduction of the online casting roll is set to 20mm, the friction force distribution coefficient is set to 69; the friction force coefficient of each light reduction roll is set to 100.

[0029] Example 2

[0030] For 160mm billet, the billet corner radius is set to 20mm, the total reduction of the online casting roll is set to 20mm, the friction force distribution coefficient is set to 69; the friction force coefficient of each light reduction roll is set to 100.

[0031] Example 3

[0032] For 160mm billet, the billet corner radius is set to 11mm, the total reduction of the online casting roll is set to 10mm, the friction force distribution coefficient is set to 70; the friction force coefficient of each light reduction roll is set to 100.

[0033] Example 4

[0034] For 160mm billet, the billet corner radius is set to 11mm, the total reduction of the online casting roll is set to 40mm, the friction force distribution coefficient is set to 20; the friction force coefficient of each light reduction roll is set to 100.

[0035] Example 5

[0036] For 160mm billet, the billet corner radius is set to 11mm, the total reduction of the online casting roll is set to 40mm, the friction force distribution coefficient is set to 49; the friction force coefficient of each light reduction roll is set to 100.

[0037] Example 6

[0038] For 220mm billet, the billet corner radius is set to 21mm, the total reduction of the online casting roll is set to 20mm, the friction force distribution coefficient is set to 69; the friction force coefficient of each light reduction roll is set to 100.

[0039] Example 7

[0040] For 400mm billet, the billet corner radius is set to 40mm, the total reduction of the online casting roll is set to 20mm, the friction force distribution coefficient is set to 69; the friction force coefficient of each light reduction roll is set to 100.

[0041] Example 8

[0042] For 220mm billet, the billet corner radius is set to 25mm, the total reduction of the online casting roll is set to 10mm, the friction force distribution coefficient is set to 70; the friction force coefficient of each light reduction roll is set to 100.

[0043] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A method for improving the surface quality of continuous casting billets based on online casting roll friction, characterized in that: The following steps are involved: Step 1: setting the light pressure amount and friction force distribution coefficient of the continuous casting billet passing through the light pressure roller; When the continuous casting billet is less than 200 mm, the fillet radius of the continuous casting billet is set to (10, 20] mm; when the continuous casting billet is (200, 400] mm, the fillet radius of the continuous casting billet is set to (20~50] mm; The friction force distribution coefficient of the light pressure roller is 100; Step 2: Setting the reduction amount and friction distribution coefficient of the continuous casting billet passing through the online casting roller to reduce the friction of the online casting roller and avoid the generation of transverse cracks in the billet corners; When the online casting roller reduction is [10,20) mm, the online casting roller friction force distribution coefficient is 70-90; when the online casting roller reduction is [20,30) mm, the online casting roller friction force distribution coefficient is 50-70; when the online casting roller reduction is [30,50) mm, the online casting roller friction force distribution coefficient is 20-50.

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