Method for continuous casting of slabs and high-strength low-alloy steel slab

Abstract

This application discloses a continuous casting method for slabs and a high-strength low-alloy steel slab. The continuous casting method includes injecting refined molten steel into a continuous casting machine, cooling it once in a crystallizer to solidify it into a slab, and then drawing the slab under the action of clamping rolls according to the first roll gap curve shown in Figure 1 to obtain the slab, which comprises a high-strength low-alloy steel slab. According to the embodiments of this application, the risk of surface cracks in the slab can be reduced, and the quality of the slab and the first-pass continuous casting yield can be improved.

Description

Technical Field

[0001] This application relates to a continuous casting method for slabs and high-strength low-alloy steel slabs. Background Technology

[0002] High-strength low-alloy steel (HSLA) has significant advantages in automotive manufacturing, primarily in the following aspects: First, it possesses excellent mechanical properties, including high strength, good formability, and superior weldability; second, its material cost is more competitive compared to traditional steel. Therefore, this material is widely used in key automotive structural components, including upper A-pillar reinforcements, inner B-pillars, extended door sills, outer panels of left and right longitudinal beams, and chassis seat support components.

[0003] However, high-strength low-alloy steel (HSLA) slabs are prone to cracking defects during continuous casting, especially at the corners of the slabs. This can greatly affect the quality of high-strength low-alloy steel and the first-time continuous casting yield. Summary of the Invention

[0004] This application provides a continuous casting method for slabs and a high-strength low-alloy steel slab, which can reduce the risk of surface cracks in the slab and improve the quality of the slab and the first-time continuous casting pass rate.

[0005] In one aspect, embodiments of this application provide a continuous casting method for slabs. The continuous casting machine includes a crystallizer and multiple pairs of vertically arranged pinch rolls adjacent to the crystallizer, the distance between the pinch rolls being the roll gap. The method includes the following steps: injecting refined molten steel into the continuous casting machine, cooling it once in the crystallizer, and solidifying it into a slab; the slab, under the action of the pinch rolls, is cast according to... Figure 1 The first roll gap curve shown is used for drawing to obtain a slab, which includes a high-strength low-alloy steel slab.

[0006] The continuous casting method disclosed in the embodiments of this application adopts... Figure 1 The special reduction technique shown in the first roll gap curve allows the strain rate at the solidification front of the slab to be lower than the critical strain rate of the steel grade at the corresponding temperature, thus ensuring a crack-free slab surface and improving internal defects such as segregation, porosity, and shrinkage cavities. This improves the slab quality and the yield rate of a single continuous casting.

[0007] In some embodiments, the continuous casting machine includes multiple pairs of vertically arranged pinch rolls, which are divided into first pinch rolls, second pinch rolls, ..., nth pinch rolls in order of distance from the crystallizer, where n is four to eight. The first pinch roll is close to the crystallizer, and the nth pinch roll is away from the crystallizer and located at the tail of the continuous casting machine. The gap between the pinch rolls is y, and the distance between the different pinch rolls and the crystallizer is x. x and y satisfy the following condition: y = -0.2165x + 247.03.

[0008] In some embodiments, the clamping roll includes a pressing roll located at the tail of the continuous casting machine, and the pressing roll has side edges on both axial sides, with the inner surface of the side edges in contact with the billet being a smooth transition surface.

[0009] In some embodiments, the throwing speed is 1.3 m / min to 1.6 m / min.

[0010] In some embodiments, the slab includes Fe, C and alloying elements, the alloying elements include one or more of Mn, Nb, Ti and V, the mass content of C is 0.05%-0.085%, and the mass content of the alloying elements is 0.0243%-0.3420%.

[0011] In some embodiments, the thickness of the slab is 200-280 mm.

[0012] In some embodiments, the yield strength of the slab is 300 MPa-800 MPa.

[0013] In some embodiments, the nitrogen content in the refined steel is less than 55 ppm.

[0014] In some embodiments, after the refined molten steel is cooled once in the crystallizer, it solidifies into a billet. The crystallizer moves up and down in a reciprocating motion according to a set amplitude and frequency so that the initial billet shell in the crystallizer is demolded from the inner wall of the crystallizer. The amplitude is 3.8mm-4mm and the frequency is 140-142cpm.

[0015] In some embodiments, the crystallizer further includes a cooling system, the total water volume in the cooling system being 3600L / min-4200L / min, and the water flow rate in a single cooling channel in the cooling system being 340L / min-400L / min.

[0016] Secondly, the embodiments of this application provide a high-strength low-alloy steel slab, wherein more than 99% of the corner area of ​​the high-strength low-alloy steel slab is free of cracks.

[0017] In some embodiments, the slab includes Fe, C and alloying elements, the alloying elements include one or more of Mn, Nb, Ti and V, the mass content of C is 0.05%-0.085%, and the mass content of the alloying elements is 0.0243%-0.3420%.

[0018] In some embodiments, the thickness of the slab is 200-280 mm.

[0019] In some embodiments, the yield strength of the slab is 300 MPa-800 MPa. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The roll gap curves of embodiments and comparative examples of this application are shown, wherein the first roll gap curve is the roll gap curve in the embodiment, the third roll gap curve is the roll gap curve in the comparative example, and the second roll gap curve is the roll gap curve with a section of pressing down in the related art.

[0022] The accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0023] To better understand the above-mentioned objectives, features, and advantages of this application, the solution of this application will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0024] Many specific details are set forth in the following description in order to provide a full understanding of this application, but this application may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of this application, and not all embodiments.

[0025] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is also expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0026] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0027] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0028] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0029] Unless otherwise specified, in this application, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0030] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0031] In the description of the embodiments of this application, unless otherwise specified, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0032] Continuous casting of slabs is the process of directly casting molten steel into solid slabs. Its core is a continuous, controlled solidification process. Specific steps generally include: 1. Steel receiving and pouring: Molten steel from the refining furnace (such as an LF furnace) is placed on a rotary table; the molten steel flows into the tundish through a long nozzle, sealed with argon gas throughout to prevent oxidation; it then flows back into the tundish to stabilize the steel flow and further lift small inclusions. 2. Primary cooling and initial solidification: Molten steel from the tundish flows into a water-cooled copper crystallizer through an immersion nozzle. The crystallizer is circulated with high-speed cooling water, allowing the molten steel to solidify into a primary slab shell, the interior of which remains molten steel. 3. Secondary cooling and slab shell growth: The primary slab shell, carrying its liquid core, is continuously pulled out from the bottom of the crystallizer using a billet puller. The slab is supported, guided, and its shape controlled by clamping rollers to prevent bulging. In this process, the surface of the billet is sprayed with atomized water for secondary cooling, which further solidifies the liquid core inside, resulting in a slab.

[0033] Continuous casting processes require the use of continuous casting machines. A continuous casting machine mainly includes a crystallizer, which provides primary cooling and initial solidification. The crystallizer can also reciprocate up and down according to a set amplitude and frequency to facilitate better demolding of the initial billet shell from the inner wall of the crystallizer. The continuous casting machine also includes a fan-shaped section, which provides secondary cooling and billet shell growth. The fan-shaped section is a modular unit composed of multiple pairs of clamping rollers, cooling water nozzles, a frame, and adjustment devices, connected in series to form the running channel for the cast billet. The roller gap can also be adjusted by changing the distance between the clamping rollers.

[0034] This application provides a method for continuous casting of slabs, in which refined molten steel is poured into a continuous casting machine, cooled once in a crystallizer, and solidified into a slab. The slab is then subjected to the action of clamping rollers and cast according to... Figure 1 The first roll gap curve is used for drawing to obtain a slab, which includes a high-strength low-alloy steel slab.

[0035] In continuous casting, related technologies often employ a two-stage reduction process to further solidify the billet into a slab. In this case, the roll gap curve is a non-smooth, broken line (see [link to relevant documentation]). Figure 1 The reduction amount in the two-stage pressing process creates a reaction force on the slab against the clamping rolls, which further increases stress concentration at the corners of the slab during bending and straightening, leading to corner cracks. These cracks manifest as transverse cracks, and their location can coincide with vibration marks left on the slab surface during demolding, further increasing the risk of crack formation. Additionally, frequent instances of the slab being unable to be pulled out during production, causing the pulling speed to stop, also occur. Related technologies using a single-stage pressing process (see...) Figure 1 (Second roll gap curve) Due to the lack of light pressing, internal defects such as segregation will appear in the slab.

[0036] The continuous casting method disclosed in the embodiments of this application adopts... Figure 1The special reduction technique shown in the first roll gap curve allows the strain rate at the solidification front of the slab to be lower than the critical strain rate of the steel grade at the corresponding temperature, thus resulting in crack-free slab surfaces and improving internal defects such as segregation, porosity, and shrinkage cavities. This improves slab quality and the yield rate of single-pass continuous casting. The roll gap curve can be adjusted by changing the roll gap opening at different positions of the clamping rolls.

[0037] In some embodiments, the continuous casting machine includes multiple pairs of vertically arranged pinch rolls, which are divided into first pinch rolls, second pinch rolls, ..., nth pinch rolls in order of distance from the crystallizer, where n is four to eight. The first pinch roll is close to the crystallizer, and the nth pinch roll is away from the crystallizer and located at the tail of the continuous casting machine. The gap between the pinch rolls is y, and the distance between the different pinch rolls and the crystallizer is x. x and y satisfy y = -0.2165x + 247.03.

[0038] The rollers at different positions have the aforementioned roll gaps, which allows the strain rate at the solidification front to be lower than the critical strain rate of the steel grade at the corresponding temperature. This results in crack-free slab surfaces and also improves internal defects such as segregation, porosity, and shrinkage cavities in the cast slab. Consequently, the quality of the slab and the yield rate of a single continuous casting can be improved.

[0039] In some embodiments, the clamping roll includes a pressing roll located at the tail of the continuous casting machine, and the pressing roll has side edges on both axial sides, with the inner surface of the side edges in contact with the billet being a smooth transition surface.

[0040] The clamping rollers serve as basic support and guides, reducing the risk of the billet bulging under the static pressure of molten steel, maintaining the basic shape of the billet, and guiding it to move along a predetermined arc track.

[0041] The pressure roller is a type of clamping roller, usually set at the end of the billet solidification into a slab, or in the slab straightening section. It can actively and precisely apply compression deformation to the billet on a supporting foundation.

[0042] In this embodiment, side edges are provided on both sides of the pressing roller along the axial direction, and the inner surface of the side edges in contact with the billet is a smooth transition surface. This can further eliminate the driving force for cracks to occur in the corner area of ​​the billet, thereby reducing the risk of pressing cracks; and the smooth transition surface adopts an arc or a continuously changing arc transition, which can prevent stress concentration from occurring on the contact surface between the side edges and the billet during the pressing deformation process, further reducing the risk of pressing cracks.

[0043] In some embodiments, the throwing speed is 1.3 m / min to 1.6 m / min. For example, it can be 1.3 m / min, 1.35 m / min, 1.4 m / min, 1.45 m / min, 1.5 m / min, 1.55 m / min, 1.6 m / min, or any range of the above values.

[0044] The billet casting speed is the most active and critical variable in continuous casting production, directly determining the solidification state of the billet. Changes in the casting speed can affect the location where the billet completely solidifies; for example, increasing the casting speed will shift the location of complete solidification significantly downwards from the casting machine. Since the roll gap profile deals with the solidifying billet, changes in the casting speed will affect the roll gap profile settings.

[0045] The embodiments of this application, with the aforementioned drawing speed, allow for better distribution of the reduction amount of each pressure roller, generating sufficient compression at the end of solidification to weld the central shrinkage cavity, while reducing the risk of excessive strain in the high-pressure phase region leading to internal cracks. This improves the quality of the slab.

[0046] In some embodiments, the slab includes Fe, C and alloying elements, the alloying elements include one or more of Mn, Nb, Ti and V, the mass content of C is 0.05%-0.085%, and the mass content of the alloying elements is 0.0243%-0.3420%.

[0047] The mass content of element C is 0.05%-0.085%. For example, it can be 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, or any range of the above values.

[0048] The mass content of the alloying elements is 0.0243%-0.3420%. For example, it can be 0.0243%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20%, 0.21%, 0.22%, 0.2340%, 0.2380%, 0.2400%, 0.2420%, 0.2460%, 0.2500%, 0.2600%, 0.2700%, 0.2800%, 0.2900%, 0.3000%, 0.3100%, 0.3200%, 0.3300%, 0.3340%, 0.3380%, 0.3400%, 0.3420%, or any range of the above values.

[0049] The elemental composition of a slab will change its critical strain rate at a corresponding temperature, and the magnitude of the critical strain rate and the strain rate at the solidification front of the slab will directly affect the surface quality of the slab.

[0050] The embodiments of this application have slabs with specific elemental compositions, which can make the strain rate at the solidification front of the slab lower than the critical strain rate of the steel grade at the corresponding temperature, thereby reducing the risk of cracks appearing on the slab surface and thus improving the quality of the slab.

[0051] In some embodiments, the alloying elements include Mn and Nb, wherein the mass content of Mn is 0.22%-0.32% and the mass content of Nb is 0.0140%-0.0220%.

[0052] In some embodiments, the alloying elements include Nb and Ti, wherein the mass content of Ti is 0.0050%-0.0070% and the mass content of Nb is 0.0140%-0.0220%.

[0053] In some embodiments, the thickness of the slab is 200mm-280mm. For example, it can be 200mm, 210mm, 220mm, 230mm, 240mm, 250mm, 260mm, 270mm, 280mm, or any range of the above values.

[0054] In some embodiments, the yield strength of the slab is 300MPa-800MPa. For example, it can be 300MPa, 350MPa, 400MPa, 450MPa, 500MPa, 550MPa, 600MPa, 650MPa, 700MPa, 750MPa, 800MPa, or any range of the above values.

[0055] In some embodiments, the nitrogen content in the refined steel is less than 55 ppm. For example, it can be 54 ppm, 53 ppm, 52 ppm, 51 ppm, 50 ppm, 45 ppm, 40 ppm, 35 ppm, 30 ppm, 25 ppm, 20 ppm, or any range of the above values.

[0056] Nitrogen is a harmful element that reduces the plasticity and impact toughness of steel, and like phosphorus, it can cause brittleness in steel during cooling. Nitrogen also forms nitride inclusions with elements such as titanium and niobium in steel, which easily precipitate at the edges of the cast billet during cooling, affecting the plasticity of the billet edges.

[0057] The embodiments of this application control the N content in the refined steel to be low, which can reduce the risk of cracks appearing on the slab surface and thereby improve the quality of the slab.

[0058] In some embodiments, after the refined molten steel is cooled once in the crystallizer, it solidifies into a billet. The crystallizer moves up and down in a reciprocating motion according to a set amplitude and frequency so that the initial billet shell in the crystallizer is demolded from the inner wall of the crystallizer. The amplitude is 3.8mm-4mm and the frequency is 140-142cpm.

[0059] The amplitude is 3.8mm-4mm. For example, it can be 3.8mm, 3.85mm, 3.90mm, 3.95mm, 4mm, or any range of the above values.

[0060] The frequency is 140-142 cpm. For example, it can be 140 cpm, 140.5 cpm, 141 cpm, 141.5 cpm, 142 cpm, or any range of the above values.

[0061] Crystallizer vibration can reduce the risk of the primary billet shell sticking to the inner wall of the crystallizer, allowing for better demolding. However, crystallizer vibration can also cause vibration marks on the surface of the primary billet shell, which can further induce surface cracks.

[0062] The embodiments of this application utilize high-frequency, low-amplitude vibration to reduce negative slip time and decrease vibration mark depth. This improves the quality of the slab.

[0063] In some embodiments, the crystallizer further includes a cooling system, the total water volume in the cooling system being 3600L / min-4200L / min, and the water flow rate in a single cooling channel in the cooling system being 340L / min-400L / min.

[0064] The total water flow rate in the cooling system is 3600L / min-4200L / min. For example, it can be 3600L / min, 3700L / min, 3800L / min, 3900L / min, 4000L / min, 4100L / min, 4200L / min, or any range of the above values.

[0065] The water flow rate in a single cooling channel of the cooling system is 340L / min-400L / min. For example, it can be 340L / min, 345L / min, 350L / min, 355L / min, 360L / min, 365L / min, 370L / min, 375L / min, 380L / min, 385L / min, 390L / min, 395L / min, 400L / min, or any range of the above values.

[0066] Cooling strategies can affect the growth of cracks in the cast billet. The cooling system of this application embodiment, with the aforementioned total water volume and water flow rate in a single cooling channel, can reduce the shrinkage of the billet shell, resulting in uniform shell growth and reducing the risk of cracks appearing on the slab surface, thereby improving the quality of the slab.

[0067] Example The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0068] Example 1 HSLA was smelted using a 210t converter, producing 225t of molten steel. The converter used scrap steel. The crude steel was then transferred to a refining furnace for smelting to obtain refined steel with a nitrogen content of 52ppm. Molten steel is poured into a continuous casting machine, and after being cooled once in a crystallizer, it solidifies into a billet. The billet is then subjected to the action of clamping rollers and follows the... Figure 1 The first roll gap curve shown is used for drawing to obtain a slab. The amplitude of the crystallizer vibration is 4 mm, the frequency is 140 cpm, the total water volume in the crystallizer is 4000 L / min, the water flow rate is 380 L / min, the cross-section of the crystallizer is 1420 mm * 240 mm, and the drawing speed is 1.5 m / min. The mass content of C in the slab is 0.072%, the mass contents of Nb and Ti are 0.0176% and 0.0067% respectively, and the surface crack incidence of the slab is 0.

[0069] Example 2 The experimental steps are basically the same as in Example 1, the only difference being the amount of water and the water flow rate in the crystallizer.

[0070] HSLA was smelted using a 210t converter, producing 225t of molten steel. The converter used scrap steel. The crude steel was then transferred to a refining furnace for smelting to obtain refined steel with a nitrogen content of 50ppm. Molten steel is poured into a continuous casting machine, and after being cooled once in a crystallizer, it solidifies into a billet. The billet is then subjected to the action of clamping rollers and follows the... Figure 1 The first roll gap curve shown is used for drawing to obtain a slab. An LG14# crystallizer was selected, with a total water volume of 4200 L / min, a water flow rate of 400 L / min, a crystallizer cross-section of 1420 mm * 240 mm, and a drawing speed of 1.5 m / min. The surface crack incidence rate of the slab was 1.05%.

[0071] Example 3 The experimental procedures were basically the same as in Example 1, with the only differences being the crystallizer vibration parameters and the N content in the refined steel.

[0072] HSLA was smelted using a 210t converter, producing 225t of molten steel. The converter used scrap steel. The crude steel was then transferred to a refining furnace for smelting to obtain refined steel with a nitrogen content of 64ppm. Molten steel is poured into a continuous casting machine, and after being cooled once in a crystallizer, it solidifies into a billet. The billet is then subjected to the action of clamping rollers and follows the... Figure 1 The first roll gap curve shown is used for drawing to obtain a slab. The amplitude of the crystallizer vibration is 4 mm, the frequency is 140 cpm, the total water volume in the crystallizer is 4000 L / min, the water flow rate is 380 L / min, the cross-section of the crystallizer is 1420 mm * 240 mm, and the drawing speed is 1.5 m / min. The surface crack incidence rate of the slab is 2.23%.

[0073] Example 4 The experimental steps are basically the same as in Example 1, with the only differences being the crystallizer vibration parameters, the amount of water in the crystallizer, and the N content in the refined steel.

[0074] HSLA was smelted using a 210t converter, producing 225t of molten steel. The converter used scrap steel. The crude steel was then transferred to a refining furnace for smelting to obtain refined steel with a nitrogen content of 66ppm. Molten steel is poured into a continuous casting machine, and after being cooled once in a crystallizer, it solidifies into a billet. The billet is then subjected to the action of clamping rollers and follows the... Figure 1 The first roll gap curve is used for drawing to obtain a slab. An LG17# crystallizer vibration unit was selected, with a total water volume of 4200 L / min, a water flow rate of 400 L / min, a crystallizer cross-section of 1420 mm * 240 mm, and a drawing speed of 1.5 m / min. The surface crack incidence rate of the slab was 3.51%.

[0075] Comparative Example 1 The experimental procedure is basically the same as in Example 1, the only difference being the roll gap curve. Figure 1 The third roll gap curve is shown. The incidence of surface cracks in the slab is 5.85%.

[0076] Comparative Example 2 The experimental steps are basically the same as in Example 2, the only difference being the roll gap curve. Figure 1 The third roll gap curve is shown. The incidence of surface cracks in the slab is 6.76%.

[0077] Comparative Example 3 The experimental steps are basically the same as in Example 3, the only difference being the roll gap curve. Figure 1 The third roll gap curve is shown. The incidence of surface cracks in the slab is 11.46%.

[0078] Comparative Example 4 The experimental steps are basically the same as in Example 4, the only difference being the roll gap curve. Figure 1 The third roll gap curve is shown. The incidence of surface cracks in the slab is 20.05%.

[0079] As can be seen from the embodiments and comparative examples, the embodiments of this application employ [the following] in continuous casting. Figure 1 The optimized roll gap curve shown can reduce the risk of crack defects on the slab surface, improve the slab quality and the first-time continuous casting pass rate.

[0080] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A method for continuous casting of slabs, the continuous casting machine comprising a crystallizer and a plurality of pairs of vertically arranged pinch rolls adjacent to the crystallizer, the distance between the pinch rolls being the roll gap, characterized in that, Includes the following steps: Refined molten steel is poured into a continuous casting machine and solidified into a billet after being cooled once in a crystallizer. The billet is then drawn under the action of the clamping rollers according to the first roll gap curve shown in Figure 1 to obtain the slab. The slab includes a high-strength low-alloy steel slab.

2. The continuous casting method according to claim 1, characterized in that, The continuous casting machine includes multiple pairs of vertically arranged pinch rolls, which are divided into first pinch roll, second pinch roll, ..., nth pinch roll in order of distance from the crystallizer, where n is four to eight. The first pinch roll is close to the crystallizer, and the nth pinch roll is away from the crystallizer and located at the tail of the continuous casting machine. The gap between the pinch rolls is y, and the distance between each pinch roll and the crystallizer is x. x and y satisfy the following condition: y = -0.2165x + 247.

03.

3. The continuous casting method according to claim 1, characterized in that, The clamping roll includes a pressing roll, which is located at the tail of the continuous casting machine, and the pressing roll has side edges on both axial sides, with the inner surface of the side edge in contact with the billet being a smooth transition surface.

4. The continuous casting method according to claim 1, characterized in that, The throwing speed is 1.3m / min-1.6m / min.

5. The continuous casting method according to claim 1, characterized in that, The slab comprises Fe, C, and alloying elements, wherein the alloying elements include one or more of Mn, Nb, Ti, and V, the mass content of C is 0.05%-0.085%, and the mass content of the alloying elements is 0.0243%-0.3420%; and / or, The thickness of the slab is 200-280 mm; and / or, The yield strength of the slab is 300MPa-800MPa.

6. The continuous casting method according to claim 1, characterized in that, The nitrogen content in the refined steel is less than 55 ppm.

7. The continuous casting method according to claim 1, characterized in that, After being cooled once in a crystallizer, the refined molten steel solidifies into a billet. The crystallizer moves up and down in a reciprocating motion according to a set amplitude and frequency so that the initial billet shell in the crystallizer is demolded from the inner wall of the crystallizer. The amplitude is 3.8mm-4mm and the frequency is 140-142cpm.

8. The continuous casting method according to claim 1, characterized in that, The crystallizer also includes a cooling system, the total water volume of which is 3600L / min-4200L / min, and the water flow rate of a single cooling channel in the cooling system is 340L / min-400L / min.

9. A high-strength low-alloy steel slab, characterized in that, More than 99% of the corner area of ​​the high-strength low-alloy steel slab is free of cracks.

10. The high-strength low-alloy steel slab according to claim 9, characterized in that, The slab comprises Fe, C, and alloying elements, wherein the alloying elements include one or more of Mn, Nb, Ti, and V, the mass content of C is 0.05%-0.085%, and the mass content of the alloying elements is 0.0243%-0.3420%; and / or, The thickness of the slab is 200-280 mm; and / or, The yield strength of the slab is 300MPa-800MPa.

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