Method for determining roll diameter and roll spacing of straightening section in continuous casting reduction process

Abstract

The present application belongs to the technical field of continuous casting production, and relates to a method for determining the roll diameter and roll spacing of a straightening section in a continuous casting pressing process. Based on a mathematical model of solidification heat transfer and a high-temperature stress-strain model for bloom continuous casting, under a typical light pressing condition, the mathematical model of solidification heat transfer and the high-temperature stress-strain model are used to obtain the relationship between the maximum strain of a crack sensitive zone and the roll diameter and the roll spacing under different roll diameters and different roll spacings, and a curve of the relationship between the maximum strain of the crack sensitive zone and the roll diameter and a curve of the relationship between the maximum strain of the crack sensitive zone and the roll spacing are established correspondingly. Meanwhile, a curve of the relationship between the roll diameter and the deflection and a curve of the relationship between the roll spacing and the bulging amount are established. The reasonable roll array parameters of the caster are determined through the curves, so as to prevent the bending deformation of the rolls and the surface cracks of the cast blank.

Description

Technical Field

[0001] This invention belongs to the field of continuous casting production technology and relates to a method for determining the roller diameter and roller spacing of the straightening section in the continuous casting pressing process. Background Technology

[0002] The roll arrangement is a crucial aspect of the entire continuous casting project design and a core element of the overall design. It directly impacts the investment cost of the continuous casting machine and is closely related to the quality of the cast billet. The roll arrangement serves two important purposes: determining the roll diameter and roll spacing, which are vital for the smooth operation of the continuous casting process. If the roll diameter is too small, it can easily cause the rolls to bend and deform; the roll spacing can affect the bulging of the cast billet.

[0003] In recent years, the widespread application of dynamic reduction technology in secondary cooling of continuous casting has placed higher demands on the roll arrangement of continuous casting machines. Currently, research on the influence of roll arrangement design parameters (roll diameter, roll spacing) in the secondary cooling reduction zone of the casting machine on the crack sensitivity, center segregation, density, and other quality issues of the cast billet is relatively lacking. With the development of computer technology and the finite element method, simulating the stress and strain of the cast billet reduction process using finite element software is one of the effective means for continuous casting engineering design and design guidance.

[0004] Roll arrangement is a crucial component of continuous casting machine process design, primarily involving determining the roll diameter and roll spacing. During the secondary cooling light and heavy pressing processes, the roll spacing of the pressing rolls affects the bulging deformation of the cast billet, while the roll diameter determines the pressing capacity of the pressing equipment, thus influencing the billet quality. Therefore, selecting appropriate roll diameter and roll spacing is of paramount importance in the continuous casting machine roll arrangement process. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to solve the above-mentioned technical defects and provide a method for determining the roller diameter and roller spacing of the straightening section in the continuous casting pressing process, which is beneficial to prevent the rollers from bending and deforming and to avoid surface cracks in the cast billet.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for determining the roller diameter and roller spacing of the straightening section in a continuous casting reduction process includes the following steps:

[0008] 1) Using the solidification heat transfer mathematical model and high-temperature stress-strain model of large billet continuous casting, under typical light pressure conditions, the relationship between the maximum strain of the crack-sensitive area and the roll diameter and roll spacing under different roll diameters and different roll spacings is obtained through the solidification heat transfer mathematical model and high-temperature stress-strain model of large billet continuous casting. Correspondingly, the relationship curves between the maximum strain of the crack-sensitive area and the roll diameter and the relationship curves between the maximum strain of the crack-sensitive area and the roll spacing are established.

[0009] 2) Calculate the deflection value of the pressing roller under different roller diameter conditions during the pressing process, and establish the relationship curve between roller diameter and deflection;

[0010] 3) Calculate the bulging amount of the billet under different roll spacing conditions during the pressing process, and establish the relationship curve between roll spacing and bulging amount;

[0011] 4) Whether the maximum strain generated at the solidification front of the billet exceeds the allowable critical strain is used to measure whether the billet has internal cracks, and to determine the maximum strain value of the crack-sensitive zone of the billet under the allowable critical strain condition.

[0012] 5) In the curve relating roll diameter to deflection, the lower limit of roll diameter is determined by the allowable value of deflection; at the same time, in the curve relating maximum strain in the crack-sensitive zone to roll diameter, the upper limit of roll diameter is determined by the maximum strain value in the crack-sensitive zone under the allowable critical strain condition.

[0013] In the curve relating roll spacing to bulging, the upper limit of roll spacing is determined by the allowable value of bulging; at the same time, in the curve relating the maximum strain in the crack-sensitive zone to roll spacing, the lower limit of roll spacing is determined by the maximum strain value in the crack-sensitive zone under the allowable critical strain condition.

[0014] Among them, the large square billet is a GCr15 steel large square billet with a cross-sectional size of 420mm×530mm.

[0015] Among them, the maximum strain value of the crack-sensitive zone of GCr15 billet under the allowable critical strain condition is 0.5%.

[0016] The allowable deflection value for GCr15 billets is 0.1 mm, and the formula for calculating the deflection value is as follows:

[0017]

[0018] In the formula, q is the uniformly distributed load; l is the roll length; E is the elastic modulus; and I is the moment of inertia.

[0019] Here, q is obtained by averaging the compressive force obtained through finite element simulation.

[0020] The allowable bulging amount for GCr15 billets is 0.5 mm; the calculation formula for the bulging amount between the two rolls is as follows:

[0021]

[0022] E = 3.146 × 10 4 -22.56t + 1.36 × 10 -3 T 2

[0023]

[0024] In the formula, δ max P is the maximum bulging deformation; l is the static pressure of molten steel; t is the roll gap; E is the time required to pass through one roll gap; S is the elastic modulus; T is the billet shell thickness; K is the temperature; L is the solidification coefficient; L is the distance from the liquid surface of the crystallizer; V is the billet drawing speed.

[0025] The beneficial effects of this invention are as follows:

[0026] This invention is based on the existing high-temperature stress-strain model of the continuous casting process of large billets. It obtains the influence law of different roll arrangement parameters on the stress-strain behavior of the billet. At the same time, it combines the deformation of the rolls and the bulging deformation behavior of the billet to establish parameter relationship curves. The reasonable roll arrangement parameters of the casting machine are determined by the curves.

[0027] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0029] Figure 1 This is a schematic diagram of roller deflection calculation in this invention.

[0030] Figure 2 This is the curve showing the relationship between the maximum strain in the crack-sensitive area and the roll diameter in this invention.

[0031] Figure 3 This is a curve showing the relationship between the maximum strain in the crack-sensitive area and the roll spacing in this invention.

[0032] Figure 4 This is a curve showing the relationship between roller deflection and roller diameter in this invention.

[0033] Figure 5 This is a curve showing the relationship between the bulging amount of the cast billet and the roll spacing in this invention.

[0034] Figure 6 This is a schematic diagram illustrating the range of values ​​for the roller diameter.

[0035] Figure 7 This shows the range of values ​​for the roller spacing. Detailed Implementation

[0036] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0037] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0038] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present 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, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0039] Please see Figures 1-7 This invention relates to a method for determining the roller diameter and roller spacing of the straightening section during continuous casting reduction, comprising the following steps:

[0040] 1) Using the solidification heat transfer mathematical model and high-temperature stress-strain model of large billet continuous casting, the model establishment process refers to the "Study on Stress-Strain and Deformation Behavior of Bloom in the Heavy Reduction Process Under Single Roll" published by Springer on February 4, 2022. Under typical light pressure conditions, the relationship between the maximum strain of the crack-sensitive area and the roll diameter and roll spacing under different roll diameters and different roll spacing conditions is obtained through the solidification heat transfer mathematical model and high-temperature stress-strain model of large billet continuous casting. Correspondingly, the relationship curves between the maximum strain of the crack-sensitive area and the roll diameter and the relationship curves between the maximum strain of the crack-sensitive area and the roll spacing are established.

[0041] 2) Calculate the deflection value of the pressing roller under different roller diameter conditions during the pressing process, and establish the relationship curve between roller diameter and deflection;

[0042] 3) Calculate the bulging amount of the billet under different roll spacing conditions during the pressing process, and establish the relationship curve between roll spacing and bulging amount;

[0043] 4) Whether the maximum strain generated at the solidification front of the billet exceeds the allowable critical strain is used to measure whether the billet has internal cracks, and to determine the maximum strain value of the crack-sensitive zone of the billet under the allowable critical strain condition.

[0044] 5) In the curve relating roll diameter to deflection, the lower limit of roll diameter is determined by the allowable value of deflection; at the same time, in the curve relating maximum strain in the crack-sensitive zone to roll diameter, the upper limit of roll diameter is determined by the maximum strain value in the crack-sensitive zone under the allowable critical strain condition.

[0045] In the curve relating roll spacing to bulging, the upper limit of roll spacing is determined by the allowable value of bulging; at the same time, in the curve relating the maximum strain in the crack-sensitive zone to roll spacing, the lower limit of roll spacing is determined by the maximum strain value in the crack-sensitive zone under the allowable critical strain condition.

[0046] Taking a large square billet of GCr15 steel with a cross-sectional size of 420mm×530mm as an example, this paper uses a mathematical model of solidification heat transfer and a high-temperature stress-strain model for continuous casting of large square billets. A typical light reduction condition is selected to analyze the influence of the reduction roll diameter and roll spacing on the stress-strain distribution of the billet. The deflection of the rolls and the bulging deformation of the billet under different roll diameters and roll spacings are calculated. The roll diameter and roll spacing are reasonably evaluated based on the simulation results and theoretical calculation results. The solidification heat transfer model for the billet considers four heat transfer modes: secondary cooling water accumulation and evaporation, spray water heat transfer, roll clamping heat transfer, and radiation heat transfer. The specific control equations are as follows:

[0047]

[0048] In the formula, t is the temperature (K); τ is the time (s); ρ is the density of steel (kg / m3); Ce is the effective specific heat (J / (kg·℃); and λe is the thermal conductivity (W / (m·℃)).

[0049] Based on this, the temperature field distribution at different locations during the solidification process of the billet was calculated. The temperature field at the pressing position was then imported as an initial condition into the ABAQUS finite element simulation software to establish a high-temperature stress-strain model for continuous casting of square billets. This allowed for the calculation of the strain and pressing force data required for this invention. In the stress-strain model, the billet length was 3.4m, the roll diameters were 350mm, 400mm, 450mm, 500mm, 550mm, and 600mm, and the roll spacing was 0.8m, 1.0m, 1.2m, 1.45m, and 1.7m. Furthermore, the calculation process employed a hexahedral hybrid formula and reduced integral elements for the billet, and hexahedral reduced integral elements for the rolls.

[0050] According to existing literature and experience, the maximum strain value of the crack-sensitive zone of GCr15 billet under allowable critical strain conditions is 0.5%.

[0051] The allowable deflection value for GCr15 billets is 0.1 mm, and the formula for calculating the deflection value is as follows:

[0052]

[0053] In the formula, q is the uniformly distributed load; l is the roll length; E is the elastic modulus; and I is the moment of inertia.

[0054] Here, q is obtained by averaging the compressive force obtained through finite element simulation.

[0055] The allowable bulging amount for GCr15 billets is 0.5 mm; the calculation formula for the bulging amount between the two rolls is as follows:

[0056]

[0057] E = 3.146 × 10 4 -22.56t + 1.36 × 10 -3 T 2

[0058]

[0059] In the formula, δ max P is the maximum bulging deformation; l is the static pressure of molten steel; t is the roll gap; E is the time required to pass through one roll gap; S is the elastic modulus; T is the billet shell thickness; K is the temperature; L is the solidification coefficient; L is the distance from the liquid surface of the crystallizer; V is the billet drawing speed.

[0060] Among them, when the solidity at the center of the billet reduction position is 0.7 and the reduction is 5 mm, the effects of different roll diameters and different roll spacings on the maximum strain in the crack-sensitive zone are as follows: Figure 2 , Figure 3As shown. With the pressing position at the center, a solid fraction of 1.0, and a pressing amount of 30 mm, the calculated results of the roller deflection values ​​for different roller diameters are as follows. Figure 4 As shown in the figure. The result shows the variation of the billet bulge amount with the roll gap. Figure 5 As shown.

[0061] Based on comprehensive simulation and theoretical calculation results, the roll diameter of a continuous casting machine for 420mm×530mm section GCr15 steel should not be less than 350mm, and the roll spacing should be 1.4~1.5m. This roll arrangement ensures both the rigidity of the rolls to prevent bending deformation and the prevention of bulging and cracking of the cast billet during pressing. A schematic diagram of the roll diameter and roll spacing values ​​is shown below. Figure 6 , 7 As shown.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for determining the roller diameter and roller spacing of the straightening section in a continuous casting pressing process, characterized in that, Includes the following steps: 1) Using the solidification heat transfer mathematical model and high-temperature stress-strain model of large billet continuous casting, under typical light pressure conditions, the relationship between the maximum strain of the crack-sensitive area and the roll diameter and roll spacing under different roll diameters and different roll spacings is obtained through the solidification heat transfer mathematical model and high-temperature stress-strain model of large billet continuous casting. Correspondingly, the relationship curves between the maximum strain of the crack-sensitive area and the roll diameter and the relationship curves between the maximum strain of the crack-sensitive area and the roll spacing are established. 2) Calculate the deflection value of the pressing roller under different roller diameter conditions during the pressing process, and establish the relationship curve between roller diameter and deflection; 3) Calculate the bulging amount of the billet under different roll spacing conditions during the pressing process, and establish the relationship curve between roll spacing and bulging amount; 4) Whether the maximum strain generated at the solidification front of the billet exceeds the allowable critical strain is used to measure whether the billet has internal cracks, and to determine the maximum strain value of the crack-sensitive zone of the billet under the allowable critical strain condition. 5) In the curve relating roll diameter to deflection, the lower limit of roll diameter is determined by the allowable value of deflection; at the same time, in the curve relating maximum strain in the crack-sensitive zone to roll diameter, the upper limit of roll diameter is determined by the maximum strain value in the crack-sensitive zone under the allowable critical strain condition. In the curve relating roll spacing to bulging, the upper limit of roll spacing is determined by the allowable value of bulging; at the same time, in the curve relating the maximum strain in the crack-sensitive zone to roll spacing, the lower limit of roll spacing is determined by the maximum strain value in the crack-sensitive zone under the allowable critical strain condition.

2. The method for determining the roller diameter and roller spacing of the straightening section in the continuous casting pressing process according to claim 1, characterized in that: The large billet is a GCr15 steel billet with a cross-sectional size of 420mm×530mm.

3. The method for determining the roller diameter and roller spacing of the straightening section in the continuous casting pressing process according to claim 2, characterized in that: The allowable critical strain for GCr15 billets is 0.5%.

4. The method for determining the roller diameter and roller spacing of the straightening section in the continuous casting pressing process according to claim 2, characterized in that: The allowable deflection value for GCr15 cast billets is 0.1 mm. The formula for calculating the deflection value is as follows: In the formula, q is the uniformly distributed load; l is the roll length; E is the elastic modulus; and I is the moment of inertia. Here, q is obtained by averaging the compressive force obtained through finite element simulation.

5. The method for determining the roller diameter and roller spacing of the straightening section in the continuous casting pressing process according to claim 2, characterized in that: The allowable bulging amount for GCr15 billets is 0.5mm; the formula for calculating the bulging amount between the two rolls is as follows: E=3.146×10 4 -22.56t+1.36×10 -3 T 2 In the formula, δ max P is the maximum bulging deformation; l is the static pressure of molten steel; t is the roll gap; E is the elastic modulus; S is the billet shell thickness; T is the temperature; K is the solidification coefficient; L is the distance from the liquid surface of the crystallizer. V is the throwing speed.

Images