Continuous casting method for controlling fine lines at hot-rolled hemming part for automobile sheet

Abstract

The invention discloses a continuous casting method for controlling fine lines on a hot-rolled hemming part for an automobile sheet, and relates to the technical field of steel continuous casting. Comprising the following steps: obtaining molten steel of the steel for the automobile sheet; the molten steel is subjected to continuous casting, and a continuous casting billet with a chamfer bevel is obtained; the chamfering value of the chamfering inclined surface is 25 to 35 degrees; an air gap between an initial setting blank shell and a crystallizer copper plate can be better compensated by the chamfered inclined surface, so that the corner part is cooled more uniformly; and the continuous casting billet enters a secondary cooling area, the pulling speed and the specific water flow are controlled, and the continuous casting billet is cooled through the amplitude cutting technology, so that the temperature of the corner of the cooled continuous casting billet in the straightening section is higher than the temperature Ar3 at which austenite is converted into ferrite, corner cracks of the corner of the continuous casting billet in the straightening process are avoided, and the quality of the corner of the continuous casting billet is improved. The corner-crack-free continuous casting billet prepared by the method can effectively control the fine line defect of the edge part of the hot-rolled coil for the automobile sheet from the source, a qualified hot-rolled coil can be obtained after hot rolling, and the product yield is improved.

Description

Technical Field

[0001] The present application relates to the technical field of continuous casting in iron and steel metallurgy, and in particular to a continuous casting method for controlling fine wires in a hot rolled edge portion of an automobile plate. Background Art

[0002] The problem of fine lines on the edge of hot-rolled coils for automotive plates has always been the key to restricting its quality improvement and reducing the yield rate, and it is also the focus and difficulty of the metallurgical industry. According to literature records, the problem of fine lines on the edge is mostly caused by cracks in the corners of the continuous casting billet, which leads to the appearance of fine lines on the edge of the hot-rolled coil during the subsequent hot rolling process.

[0003] In the prior art, the control of the fine line of the hot rolled edge is mainly carried out by increasing the temperature of the heating furnace, adding a rough rolling insulation cover, limiting the width reduction of the width setting machine, etc. However, the above measures are not only ineffective, but also bring a series of adverse effects such as increased energy consumption and production restrictions. Therefore, it is necessary to provide a continuous casting method for controlling the fine line of the hot rolled edge for automobile plates. Summary of the invention

[0004] The present application provides a continuous casting method for controlling the fine line of the hot rolled edge of automobile plates to solve the following technical problem: how to improve the quality of the corner of the continuous casting billet.

[0005] In a first aspect, an embodiment of the present application provides a method for controlling continuous casting of a hot rolled curling fine wire for an automobile plate, comprising the following steps:

[0006] Obtaining molten steel for automobile sheet steel;

[0007] Continuously casting the molten steel to obtain a continuously cast billet with a chamfered inclined surface;

[0008] The continuous casting billet is put into the secondary cooling zone, the pulling speed and the specific water content are controlled, and the continuous casting billet is cooled by using the width cutting technology, so that the temperature of the chamfered surface of the continuous casting billet in the straightening section is higher than the temperature Ar3 at which austenite transforms to ferrite;

[0009] The chamfer value of the chamfered slope is 25° to 35°.

[0010] Optionally, a chamfered crystallizer having a chamfered slope is used for continuous casting.

[0011] Optionally, the taper and / or width of the chamfering mold is adjustable, and the taper of the chamfering mold and the cross-sectional width of the continuous casting billet satisfy the following relationship:

[0012] Taper=0.0053x+0.74

[0013] Wherein, Taper is the taper of the chamfered crystallizer, mm; x is the cross-sectional width of the continuous casting billet, mm.

[0014] Optionally, the four corners of the chamfered mold are chamfered inclined surfaces;

[0015] and / or,

[0016] The chamfer value of the chamfered inclined surface is 30°.

[0017] Optionally, the water volume on the wide surface of the chamfered mold is 5800 L / min to 6000 L / min, and the water volume on the narrow surface is 560 L / min to 600 L / min.

[0018] Optionally, the casting speed meets the following requirements:

[0019] When the cross-sectional width of the continuous casting billet > 1600 mm, the casting speed is 1.2 m / min;

[0020] When the cross-sectional width of the continuous casting billet ≤ 1600 mm, the casting speed is 1.3 m / min.

[0021] Optionally, the specific water ratio is set according to the casting speed to ensure that the temperature of the chamfered inclined surface of the continuous casting billet in the straightening section is higher than the temperature Ar3 at which austenite transforms into ferrite.

[0022] Optionally, the specific water ratio is 0.8 L / kg to 1.0 L / kg.

[0023] Optionally, the cooling of the continuous casting billet using the width cutting technology specifically includes:

[0024] Judging the cross-sectional width of the continuous casting billet;

[0025] When the cross-sectional width of the continuous casting billet ≤ 1600 mm, the spray devices on the outer side of the cooling section in the secondary cooling zone are closed to cool the continuous casting billet;

[0026] When the cross-sectional width of the continuous casting billet > 1600 mm, all the spray devices in the cooling section in the secondary cooling zone are opened to cool the continuous casting billet.

[0027] Optionally, the carbon content of the steel for automotive panels is less than 0.01%.

[0028] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0029] An embodiment of the present application provides a continuous casting method for controlling fine lines in the hot-rolled curling portion of automobile plates, comprising the following steps: obtaining molten steel for automobile plates; continuously casting the molten steel to obtain a continuously cast billet with a chamfered surface; the continuously cast billet enters a secondary cooling zone, controls the pulling speed and specific water amount, and uses a width-cutting technology to cool the continuously cast billet, so that the temperature of the corner (chamfered surface) of the cooled continuously cast billet in the straightening section is higher than the temperature Ar3 at which austenite transforms to ferrite; the chamfer value of the chamfered surface is 25° to 35°. During continuous casting, a chamfered crystallizer with a chamfered surface and a chamfer value of 25° to 35° is used for continuous casting, which can better compensate for the air gap between the initial solidification billet shell and the copper plate of the crystallizer, make the corner cooling more uniform, and inhibit the occurrence of corner cracks; after the continuous casting billet enters the secondary cooling zone, the water content is adjusted according to the pulling speed, and the continuous casting billet is cooled by the width cutting technology, so that the temperature of the corner of the cooled continuous casting billet in the straightening section is higher than the temperature Ar3 of the transformation of austenite to ferrite, thereby avoiding corner cracks at the corner of the continuous casting billet during the straightening process and improving the quality of the corner of the continuous casting billet.

[0030] The continuous casting billet prepared by the method can effectively control the fine line defects of the hot-rolled curling edge of automobile plates from the source, thereby improving the product yield rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0033] Figure 1 A schematic flow chart of a method for controlling continuous casting of hot rolled edge thin wire for automobile plates according to some embodiments of the present application;

[0034] Figure 2 A schematic diagram of a chamfered crystallizer according to some embodiments of the present application;

[0035] Figure 3 It is a schematic diagram of the second cold width cutting of Example 1 of the embodiment of the present invention;

[0036] Figure 4 This is a schematic diagram of the second cold cutting of Example 2 of the embodiment of the present invention. DETAILED DESCRIPTION

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are some, but not all, of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the scope of protection of this application.

[0038] The various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be construed as a rigid limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and individual values within that range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and individual numbers within that range, such as 1, 2, 3, 4, 5, and 6, and this applies regardless of the range; in addition, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0039] In this document, terms such as "including" mean "including but not limited to". Relative terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. "And / or" describes the associated relationship of associated objects and indicates that three relationships may exist. For example, A and / or B may mean: A exists alone, A and B exist simultaneously, or B exists alone; where A and B may be singular or plural. "At least one" means one or more, and "multiple" means two or more; "at least one kind", "at least one of the following items (pieces)" or similar expressions refer to any combination of these items, including any combination of single item (piece) or plural items (pieces); for example, "at least one of a, b, or c", or "at least one of a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively. The "parts representation method" such as parts by weight, parts by mass, etc. represents the proportional relationship between each component. In the proportional relationships involved in this document, the parameters that need to be described by proportion should be understood as the antecedents of the proportional formula in the order of description, and the proportional numbers should be understood as the consequents of the proportional formula. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one by one with the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0040] Unless otherwise specified, various raw materials, reagents, instruments, and equipment used in this article can be obtained through market purchases or can be prepared by existing methods.

[0041] Figure 1 It is a schematic flow chart of a continuous casting method for controlling the fine lines at the edge of a hot-rolled coil for automotive sheets according to some embodiments of the present application;

[0042] As Figure 1 shown, the embodiments of the present application provide a continuous casting method for controlling the fine lines at the edge of a hot-rolled coil for automotive sheets, including:

[0043] S1. Obtain the molten steel for automotive sheets to obtain a molten steel with uniform composition and purity, providing raw materials that meet the requirements for subsequent preparation;

[0044] S2. Continuously cast the molten steel to obtain a continuous casting billet with a chamfered slope, and the chamfer value of the chamfered slope is 25° - 35°;

[0045] The purpose of this step is to reduce the stress concentration at the corners of the continuous casting billet; at the same time, it can reduce the cooling rate at the corners of the continuous casting billet, delay the ferrite transformation, improve the uniformity of corner deformation during subsequent rolling, and avoid cracks.

[0046] S3. The continuous casting billet enters the secondary cooling zone, control the drawing speed and specific water volume, and use the width cutting technology to cool the continuous casting billet, so that the temperature of the corners of the cooled continuous casting billet in the straightening section is higher than the temperature Ar3 at which austenite transforms into ferrite;

[0047] The purpose in step S3 is to cool the continuous casting billet. By controlling the drawing speed and specific water volume, and at the same time combining the width cutting technology to dynamically adjust the cooling water volume, so as to adjust the cooling intensity according to the different positions and temperature changes of the continuous casting billet, to ensure uniform cooling of the continuous casting billet and avoid excessive temperature gradients. Finally, make the temperature of the corners of the continuous casting billet in the straightening section higher than the Ar3 temperature. In this way, during the straightening process, the corners are still in the austenite state, and austenite has good plasticity and is not easy to produce cracks.

[0048] In the above-described embodiment, first, a ladle for automotive sheet steel is obtained as the raw material for subsequent continuous casting and cooling; the molten steel in the ladle flows into a chamfered mold with a chamfered inclined surface to obtain a continuous casting billet; continuous casting is performed using a chamfered mold with a chamfered inclined surface and a chamfer value of 25° to 35°, which can better compensate for the air gap between the initially solidified shell and the copper plate of the mold, make the corner cooling more uniform, and inhibit the generation of corner cracks; the continuous casting billet enters the secondary cooling zone, and the cooling effect is greatly related to the drawing speed, specific water volume, and spray position. Therefore, it is necessary to control the drawing speed, specific water volume, and spray cutting technology according to the actual size of the continuous casting billet, so that the temperature of the corner of the cooled continuous casting billet in the straightening section is higher than the temperature Ar3 at which austenite transforms into ferrite, avoiding corner cracks during the straightening process of the continuous casting billet corner and improving the quality of the continuous casting billet corner.

[0049] In the above-described embodiment, the reason for controlling the chamfer value of the chamfered inclined surface to be 25° to 35° is that when the chamfer value is within this range, it helps to optimize the cooling conditions of the continuous casting billet corner, reduce the generation of corner cracks, and improve the overall quality of the casting billet. If it is higher than 35°, the hypotenuse is too large, resulting in uneven cooling; if it is lower than 25°, it will also be affected by two-dimensional heat transfer and the cooling is uneven. Exemplarily, the chamfer value of the chamfered hammer head can be 25°, 26°, 27°, 28°, 29°, 30°, 31°, 32°, 33°, 34°, or 35°.

[0050] As an alternative embodiment, continuous casting is performed using a chamfered mold with a chamfered inclined surface, and the structural schematic diagram of the chamfered mold is as Figure 2 shown, and the dimensions of the chamfered narrow side a, wide side b, and hypotenuse c of the chamfered inclined surface are 20 mm, 34.6 mm, and 40 mm, respectively.

[0051] As an alternative embodiment, the taper and / or width of the chamfered mold can be adjusted according to the cross-sectional width required for the continuous casting billet.

[0052] In the above-described embodiment, the taper is an important index for evaluating the quality of continuous casting, which is directly related to the quality and dimensional accuracy of the casting billet. An appropriate taper helps to ensure the smooth forming of the casting billet and the smooth progress of subsequent processing processes. If the taper is too large or too small, it may have an adverse impact on the quality and dimensional accuracy of the casting billet. The chamfered mold can adjust the width and taper online to meet the production control requirements of continuous casting billets with different cross-sections.

[0053] As an alternative embodiment, the taper of the chamfered mold and the cross-sectional width of the continuous casting billet satisfy the following relationship:

[0054] Taper = 0.0053x + 0.74

[0055] Wherein, Taper is the taper of the chamfered mold, in mm; x is the cross-sectional width of the continuous casting billet, in mm.

[0056] As an alternative embodiment, the four corners of the chamfered mold are chamfered inclined planes; having chamfered inclined planes at all four corners can ensure better compensation for the air gap between the initially solidified shell and the mold copper plate, making the corner cooling more uniform and suppressing the generation of corner cracks.

[0057] As an alternative embodiment, the chamfer value of the chamfered inclined plane of the chamfered mold is 30°.

[0058] As an alternative embodiment, the water flow rate on the wide face of the chamfered mold is 5800 L / min to 6000 L / min, and the water flow rate on the narrow face is 560 L / min to 600 L / min.

[0059] During continuous casting, the water flow rates on the wide face and narrow face of the chamfered mold usually act together with other parameters such as casting speed, superheat of molten steel, mold powder, hydrogen content of molten steel, and control of water flow rate and temperature difference in the first cooling zone on the cooling and solidification process of the casting billet. These parameters interact with each other and jointly affect the heat transfer, solidification, and quality control of the casting billet. In the above embodiment, controlling the water flow rate on the wide face of the chamfered mold to be 5800 L / min to 6000 L / min and the water flow rate on the narrow face to be 560 L / min to 600 L / min means that during continuous casting, there is a water flow rate of 5800 L to 6000 L per minute on the wide face part of the mold for cooling the wide face of the continuous casting billet, and a water flow rate of 560 L to 600 L per minute on the narrow face part for cooling the narrow face of the continuous casting billet. The magnitude of the water flow rate on the wide face directly affects the cooling effect of the wide face of the casting billet and the formation speed of the shell. A higher water flow rate can more effectively remove the heat of the casting billet and promote the uniform formation of the shell, thereby helping to reduce defects in the casting billet, such as transverse corner cracks. The control of the water flow rate on the narrow face is equally important because it is related to the cooling effect and temperature distribution at the corners of the casting billet. In the chamfered mold, since the chamfer value of the chamfered mold in this application is limited to 25° to 35°, setting this water flow rate on the narrow face plays a key role in delaying heat transfer at the corners, increasing the corner temperature, and improving the uniformity.

[0060] Exemplarily, the water flow rate on the wide face can be 5800 L / min, 5820 L / min, 5840 L / min, 5860 L / min, 5900 L / min, 5920 L / min, 5940 L / min, 5960 L / min, 5980 L / min, or 6000 L / min, and the water flow rate on the narrow face can be 560 L / min, 565 L / min, 570 L / min, 575 L / min, 580 L / min, 585 L / min, 590 L / min, 595 L / min, or 600 L / min.

[0061] As an alternative embodiment, the water flow rate on the wide face of the chamfered mold is 5940 L / min, and the water flow rate on the narrow face is 580 L / min.

[0062] As an alternative embodiment, the casting speed meets the following requirements:

[0063] When the cross-sectional width of the continuous casting billet > 1600 mm, the casting speed is 1.2 m / min;

[0064] When the cross-sectional width of the continuous casting billet ≤ 1600 mm, the casting speed is 1.3 m / min.

[0065] In the above embodiment, the casting speed is controlled according to the cross-sectional width of the continuous casting billet. The reason is that in order to maintain the stability and efficiency of the continuous casting process, it is necessary to reasonably adjust the casting speed according to the cross-sectional width of the billet. If the cross-sectional width is too large or too small, it may be necessary to adjust the casting speed to adapt to the solidification and forming process of the billet, so as to ensure the quality and production efficiency of the billet. Control the casting speed to meet that when the cross-sectional width of the continuous casting billet > 1600 mm, the casting speed of the continuous casting machine is 1.2 m / min, and when the cross-sectional width of the continuous casting billet

[0066] ≤ 1600 mm, the casting speed of the continuous casting machine is 1.3 m / min.

[0067] As an alternative embodiment, the specific water consumption is set according to the casting speed to ensure that the temperature of the corner of the continuous casting billet in the straightening section is higher than the temperature Ar3 at which austenite transforms into ferrite.

[0068] The specific water consumption refers to the amount of cooling water used per unit weight of molten steel, expressed in L / kg. In the above embodiment, the size of the specific water consumption is set according to the value of the casting speed. The specific value of the specific water consumption is not limited, as long as the temperature of the corner of the continuous casting billet in the straightening section is higher than the temperature Ar3 at which austenite transforms into ferrite, so as to achieve the purpose of suppressing corner cracks of the continuous casting billet. The temperature Ar3 at which austenite transforms into ferrite can be obtained through thermal expansion tests or thermodynamic software calculations of different steel grades.

[0069] As an alternative embodiment, the specific water consumption is 0.8 L / kg to 1.0 L / kg.

[0070] In the above embodiment, the reason for controlling the specific water consumption to be 0.8 - 1.0 L / kg is that the specific water consumption within this range can ensure that the temperature of the corner of the cooled continuous casting billet in the straightening section is higher than Ar3. Exemplarily, the specific water consumption can be set to 0.8 L / kg, 0.82 L / kg, 0.85 L / kg, 0.88 L / kg, 0.9 L / kg, 0.92 L / kg, 0.95 L / kg, 0.98 L / kg or 1.0 L / kg.

[0071] As an alternative implementation method, the cooling of the continuous casting billet by using the width cutting technology specifically includes:

[0072] Judge the cross-sectional width of the continuous casting billet;

[0073] When the cross-sectional width of the continuous casting billet ≤ 1600 mm, close the spray devices outside the cooling section in the secondary cooling zone to cool the continuous casting billet;

[0074] When the cross-sectional width of the continuous casting billet > 1600 mm, open all the spray devices in the cooling section of the secondary cooling zone to cool the continuous casting billet.

[0075] The cooling section in the secondary cooling zone includes a horizontal section and an arc section, etc., and multiple rows of spray devices are arranged directly above to cool the continuous casting billet. The multiple rows of spray devices include the inner spray devices (middle water circuit, sub-edge water circuit) and the outer spray devices (edge water circuit). Among them, the sub-edge water circuit is located on both sides of the middle water circuit, and the edge water circuit is located on both sides of the sub-edge water circuit. In the above implementation method, when the cross-sectional width of the continuous casting billet ≤ 1600 mm, due to the small cross-sectional width, only the spray devices of the middle and sub-edge water circuits in the horizontal section and arc section of the secondary cooling zone, that is, the inner spray devices, need to be opened to achieve cooling, and the spray devices of the edge water circuit are closed. When the cross-sectional width of the continuous casting billet > 1600 mm, the cross-sectional width is large, and all the spray devices in the cooling section of the secondary cooling zone need to be opened to achieve full cooling of the continuous casting billet.

[0076] As an alternative implementation method, the carbon content of the steel for automotive sheet is less than 0.01%.

[0077] In the above implementation method, the steel for automotive sheet is low-carbon steel or extra-low-carbon steel. The main purpose of controlling the carbon content in the steel for automotive sheet is that the continuous casting billet in this application is used for automobiles and the carbon content needs to be controlled; secondly, through the production practice of a large number of steel grades, it is found that the method in this application has the best effect on low-carbon steel or extra-low-carbon steel.

[0078] The following further elaborates this application in combination with specific embodiments. For the experimental methods without specific conditions noted in the following embodiments, they are usually measured according to national standards / industry standards; if there are no corresponding national standards / industry standards, they are carried out according to general international standards, conventional conditions or the conditions recommended by the manufacturer.

[0079] Example 1

[0080] This embodiment provides a continuous casting method for controlling the edge fine lines of hot-rolled coils for automotive sheets. Taking the continuous casting billet of ultra-low-carbon steel SEC1 produced by a certain steel mill as an example, the casting cross-sectional width is 1550×237 mm, and the chemical composition of ultra-low-carbon steel SEC1 is shown in Table 1.

[0081] Table 1 Chemical Composition of SEC1 Steel (unit: %)

[0082]

[0083] The continuous casting method of the present invention is used to improve the corner quality of the continuous casting billet to avoid edge thin line defects in subsequent hot rolling and other processes, including the following steps:

[0084] Obtain the molten steel of SEC1 steel;

[0085] Flow the molten steel of the SEC1 steel into a self-made chamfered mold to obtain a continuous casting billet;

[0086] Among them, the schematic diagram of the self-made chamfered mold is as Figure 2 shown. The dimensions of the chamfered narrow side, wide side, and bevel side of the chamfered mold are 20 mm, 34.6 mm, and 40 mm respectively, and it satisfies that the chamfer value α of the chamfered hammer head is 30°.

[0087] During the continuous casting process, the pulling speed of the continuous casting machine is 1.3 m / min, the calculated mold taper is 9.0 mm, and the water flow rates of the wide side and narrow side of the mold are 5940 L / min and 580 L / min respectively.

[0088] Cool the continuous casting billet in the secondary cooling zone. It can be calculated by using JMatPro thermodynamics software that the transformation temperature Ar3 of austenite to ferrite of SEC1 steel is 910 °C. Set the secondary cooling water ratio to 0.86 L / kg, which can meet the requirement that the temperature at the corner of the continuous casting billet is higher than Ar3 in the straightening section of the secondary cooling zone and can meet the actual cooling requirements of the continuous casting billet. At the same time, the secondary cooling zone adopts the spray cutting technology, and it is set that the nozzles at both ends of the spray racks in the arc section and the horizontal section do not spray water. The nozzle layout is as Figure 3 shown.

[0089] For the continuous casting billet produced by the above method, the corner cracks disappear, and the hot rolled coil formed after the hot rolling process is not downgraded due to edge thin lines.

[0090] Example 2

[0091] This example provides a continuous casting method for controlling edge thin lines of hot rolled coils for automotive sheets. The continuous casting produces a continuous casting billet of ultra-low carbon steel SDC04 with a casting section width of 1900×237 mm. The chemical composition of ultra-low carbon steel SDC04 is shown in Table 2.

[0092] Table 2 Chemical Composition of SDC04 Steel (unit: %)

[0093]

[0094] The continuous casting method of the present invention is used to improve the corner quality of the continuous casting billet to avoid edge thin line defects in subsequent hot rolling and other processes, including the following steps:

[0095] Molten steel of SDC04 steel is obtained;

[0096] The molten steel of the SDC04 steel is poured into a self-made chamfered mold to obtain a continuous casting billet;

[0097] Among them, the schematic diagram of the self-made chamfered mold is as Figure 2 shown. The dimensions of the narrow side, wide side, and inclined side of the chamfer of the chamfered mold are 20 mm, 34.6 mm, and 40 mm respectively, and it satisfies that the chamfer value α of the chamfered hammer head is 30°.

[0098] During the continuous casting process, the drawing speed of the continuous caster is 1.2 m / min, the calculated mold taper is 10.8 mm, and the water flow rates of the wide face and narrow face of the mold are 5940 L / min and 580 L / min respectively.

[0099] The continuous casting billet is sent into the secondary cooling zone for cooling. It can be calculated by using JMatPro thermodynamics software that the transformation temperature Ar3 from austenite to ferrite of SEC1 steel is 905 °C. The secondary cooling specific water flow rate is set to 0.88 L / kg, which can satisfy that the temperature at the corner of the continuous casting billet is higher than Ar3 in the straightening section of the secondary cooling zone, and can meet the actual cooling requirements of the continuous casting billet. At the same time, the amplitude cutting technology is adopted in the secondary cooling zone, and it is set that the nozzles at both ends of the spray racks in the arc section and the horizontal section do not spray water. The nozzle layout is as Figure 4 shown.

[0100] For the continuous casting billet produced by the above method, the corner cracks disappear, and the hot rolled coil formed after the hot rolling process is not downgraded due to the edge thin line.

[0101] Comparative Example 1

[0102] This comparative example provides a continuous casting method, which uses the same steel grade as in Example 1. The difference is that this comparative example uses the traditional continuous casting process to produce a continuous casting billet, that is, it does not use a chamfered mold for continuous casting, and at the same time, it does not use the amplitude cutting technology in the secondary cooling zone, and directly cools to obtain a continuous casting billet.

[0103] It is detected that transverse corner cracks and longitudinal corner cracks defects appear at the corners of the obtained continuous casting billet, and edge thin line defects appear in the subsequent hot rolling process, affecting the product quality and yield.

[0104] Comparative Example 2

[0105] This comparative example provides a continuous casting method, which uses the same steel grade as in Example 2. The difference is that this comparative example uses the traditional continuous casting process to produce a continuous casting billet. It is detected that transverse corner cracks and longitudinal corner cracks defects appear at the corners of the obtained continuous casting billet, and edge thin line defects appear in the subsequent hot rolling process, affecting the product quality and yield.

[0106] The degradation rate of fine wire at the edge of hot rolled coil for automobiles was statistically analyzed before and after the steel plant implemented the continuous casting method provided in this application. The results are shown in Table 3:

[0107] Table 3 Degradation rate of fine wire at hot rolled coil edge before and after the implementation of the technical solution

[0108]

[0109] It can be seen from the above table that before the implementation of the continuous casting method provided in the present application, that is, the continuous casting billet produced by the existing traditional continuous casting process is used for automobile plates, and the degradation rate of the fine lines at the edge of the automobile hot-rolled coil is 1.32. After adopting the technical solution in the present application, the degradation rate of the edge fine lines is 0, indicating that the continuous casting billet produced by the continuous casting method provided in the present application is obviously helpful in controlling the problem of fine lines at the edge of the automobile hot-rolled coil.

[0110] In summary, the present invention provides a continuous casting production method for controlling fine lines at the edge of hot-rolled coils for automobile plates. By adopting a self-developed chamfering crystallizer and formulating a secondary cooling zone control strategy, the purpose of suppressing cracks at the corners of the continuous casting billet is achieved, and fine line defects at the edge of the hot-rolled coils for automobile plates are controlled from the source. The present invention can improve the quality of the corners of the continuous casting billet, control fine line defects at the edges, and improve the product yield rate.

[0111] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. It will be apparent to those skilled in the art that various modifications to these embodiments are possible, and the general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown in the present application, but will conform to the widest range consistent with the principles and novel features applied for by the present application.

Claims

1. A continuous casting method for controlling fine lines at the edge of a hot-rolled coil for automotive panels, comprising the following steps: Obtain the molten steel of the steel for automotive panels; Perform continuous casting on the molten steel to obtain a continuously cast slab with a chamfered inclined surface; Feed the continuously cast slab into the secondary cooling zone, control the casting speed and the specific water volume, and use the width cutting technology to cool the continuously cast slab, so that the temperature of the chamfered inclined surface of the continuously cast slab in the straightening section is higher than the temperature Ar3 at which austenite transforms into ferrite; The chamfer value of the chamfered inclined surface is 25° to 35°.

2. The continuous casting method according to claim 1, wherein continuous casting is performed using a chamfered mold with a chamfered inclined surface.

3. The continuous casting method according to claim 2, wherein the taper and / or width of the chamfered mold is adjustable, and the taper of the chamfered mold and the cross-sectional width of the continuously cast slab satisfy the following relationship: Taper = 0.0053x + 0.74 Wherein, Taper is the taper of the chamfered mold, in mm; x is the cross-sectional width of the continuously cast slab, in mm.

4. The continuous casting method according to claim 2, wherein the four corners of the chamfered mold are chamfered inclined surfaces; And / or, The chamfer value of the chamfered inclined surface is 30°.

5. The continuous casting method according to claim 2, wherein the water volume on the wide face of the chamfered mold is 5800 L / min to 6000 L / min, and the water volume on the narrow face is 560 L / min to 600 L / min.

6. The continuous casting method according to claim 1, wherein the casting speed meets the following requirements: When the cross-sectional width of the continuously cast slab > 1600 mm, the casting speed is 1.2 m / min; When the cross-sectional width of the continuously cast slab ≤ 1600 mm, the casting speed is 1.3 m / min.

7. The continuous casting method according to claim 1, wherein the specific water volume is set according to the casting speed to ensure that the temperature of the chamfered inclined surface of the continuously cast slab in the straightening section is higher than the temperature Ar3 at which austenite transforms into ferrite.

8. The continuous casting method according to claim 1 or 7, wherein the specific water volume is 0.8 L / kg to 1.0 L / kg.

9. The continuous casting method according to claim 1, wherein the cooling of the continuously cast slab using the width cutting technology specifically includes: Judging the cross-sectional width of the continuously cast slab; When the cross-sectional width of the continuously cast slab ≤ 1600 mm, close the spray devices on the outer side of the cooling section in the secondary cooling zone to cool the continuously cast slab; When the cross-sectional width of the continuously cast slab > 1600 mm, open all the spray devices in the cooling section in the secondary cooling zone to cool the continuously cast slab.

10. The continuous casting method according to claim 1, wherein the carbon content of the steel for automotive panels is less than 0.01%.

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