Method for inhibiting periodical fluctuation of liquid level of 600MPa-level dual-phase steel crystallizer

Abstract

The invention discloses a method for inhibiting periodic fluctuation of the liquid level of a 600MPa-grade dual-phase steel crystallizer, which comprises the following steps: providing molten steel for continuous casting, and the molten steel for continuous casting needs to meet the following component requirements in percentage by mass: 0.095-1.1 wt.% of C; the content of Mn is 1.7 wt.%-2.1 wt.%; the content of Si is 0.20 wt.% to 0.23 wt.%; the total weight of Al is 0.02 to 0.08 percent by weight; the content of Cr is 0.17 wt.%-0.23 wt.%, and the balance is iron, so that the periodic fluctuation of a crystallizer is reduced; and a continuous casting machine is used for conducting continuous casting on the molten steel for continuous casting, and a continuous casting slab is obtained. According to the method for inhibiting the periodic fluctuation of the liquid level of the 600MPa-grade dual-phase steel crystallizer, the content of C contained in steel is optimized according to middle upper limit control, the continuous casting pulling speed is optimized, the production conditions of a continuous casting machine are confirmed, the periodic fluctuation of the liquid level of the 600MPa-grade dual-phase steel crystallizer is reduced to be + / -7mm or below from + / -12mm or above, and the continuous casting pulling speed is optimized. Periodic fluctuation of the liquid level of the dual-phase steel crystallizer in the continuous casting process can be effectively controlled, a blank shell is evenly cooled, breakout accidents are prevented, and the surface quality of a 600MPa-level dual-phase steel casting blank is greatly improved.

Description

Technical Field

[0001] The present application belongs to the technical field of steelmaking, and in particular relates to a method for suppressing periodic fluctuations in the liquid level of a 600MPa-grade dual-phase steel crystallizer. Background Art

[0002] 600MPa grade dual-phase steel is currently the most widely used high-strength automotive steel plate. It is an important material for the automotive industry to achieve lightweight body. It is widely used in automobile side beams, side members, cross beams, pillars, chassis reinforcements, fuel tank brackets and structural parts, reinforcements and anti-collision parts of the body. It has the characteristics of low yield strength ratio and high elongation, so this type of steel has been rapidly promoted and applied since its successful development. However, when steel mills produce 600MPa grade dual-phase steel, periodic fluctuations in the liquid level of the crystallizer often occur, generally above ±12mm, and up to ±20mm in severe cases. This not only causes a large amount of slag defects in the steel coil to be downgraded, but in severe cases the downgrade rate reaches 15% to 20%, and severe liquid level fluctuations can also cause steel leakage, resulting in production interruptions.

[0003] In the prior art, in order to solve the problem of periodic fluctuation of the liquid level in the crystallizer during the casting of peritectic steel, relevant scholars or experts have conducted corresponding research: for example, the 8th issue of "Steel" magazine in 2011 reported that Li Yang, Huang Quanjin and others found that increasing the strength of the front zone of the secondary cooling can effectively suppress the periodic fluctuation of peritectic steel; Liu Hong and others from China Center for Machinery Research invented "continuous casting structure with the function of eliminating periodic fluctuation of crystallization liquid level" and "a method for modifying a continuous casting machine to solve liquid level fluctuation"; Jiang Zhongkuai and others invented "continuous casting machine structure for preventing periodic fluctuation of steel liquid level in continuous casting crystallization", all of which solved the problem of periodic fluctuation of steel liquid level in the crystallizer from the direction of the arrangement of rollers of the continuous casting machine; Wu Qiang and others from Wuhan Iron and Steel Company invented "a method for preventing fluctuation of peritectic steel liquid level", using weak primary cooling strength and high alkalinity protective slag to suppress periodic fluctuation of the crystallizer liquid level. After the above technology is applied in continuous casting production practice, it has a certain inhibitory effect on the fluctuation of the liquid level of ordinary peritectic steel. However, for 600MPa grade dual-phase steel, the actual production still shows strong periodic fluctuation of the crystallizer steel liquid level, which is generally above ±10mm, and reaches ±15mm in severe cases. It is impossible to effectively solve the problem of periodic fluctuation of the crystallizer liquid level of 600MPa grade dual-phase steel. Summary of the invention

[0004] The embodiment of the present application provides a method for suppressing the periodic fluctuation of the liquid level in a 600MPa grade dual-phase steel crystallizer, which can effectively suppress the periodic fluctuation of the liquid level in the crystallizer.

[0005] In the first aspect, the present application provides a method for suppressing the periodic fluctuation of the liquid level of a 600MPa grade dual-phase steel crystallizer, comprising: providing molten steel for continuous casting, the molten steel for continuous casting must meet the following composition requirements, measured in mass percentage: C content of 0.095wt.%~1.1wt.%; Mn content of 1.7wt.%~2.1wt.%; Si content of 0.20wt.%~0.23wt.%; Al tot: 0.02wt.%~0.08wt.%; Cr content of 0.17wt.%~0.23wt.%, the remainder being iron, to reduce the periodic fluctuation of the crystallizer; using a continuous casting machine to continuously cast the molten steel for continuous casting to obtain a continuously cast slab.

[0006] According to an embodiment of the first aspect of the present application, using a continuous casting machine to continuously cast molten steel for continuous casting includes: casting the molten steel for continuous casting into a crystallizer for solidification, wherein the amount of steel passing through the crystallizer needs to satisfy: the number of narrow side furnaces ≤ 500 furnaces.

[0007] According to an embodiment of the first aspect of the present application, using a continuous casting machine to continuously cast molten steel for continuous casting includes: passing a crystallizer containing the molten steel for continuous casting through a bending section and a second cooling section of the continuous casting machine at one time, wherein the second cooling section includes a first second cooling section and a second second cooling section, the amount of steel passing through the bending section needs to satisfy: ≤1200 furnaces, the amount of steel passing through the second cooling section needs to satisfy: ≤4800 furnaces for the first second cooling section, and ≤5500 furnaces for the second second cooling section.

[0008] According to an embodiment of the first aspect of the present application, using a continuous casting machine to continuously cast molten steel for continuous casting includes: making the roll gap of the continuous casting machine conveying the crystallizer meet the standard requirements: ≤ + 1mm.

[0009] According to an embodiment of the first aspect of the present application, using a continuous casting machine to continuously cast molten steel for continuous casting includes: ensuring that the nozzles in sections 0-3 in the second cooling section of the continuous casting machine are not blocked, and the total number of blockages in sections 4-8 is ≤5.

[0010] According to an embodiment of the first aspect of the present application, using a continuous casting machine to continuously cast molten steel for continuous casting includes: centering the SEN nozzle of the tundish: the inner and outer arc deviation is ≤2mm.

[0011] According to an embodiment of the first aspect of the present application, using a continuous casting machine to continuously cast the molten steel for continuous casting includes: centering the SEN nozzle of the tundish: the inner and outer arc deviation is ≤2mm.

[0012] According to an embodiment of the first aspect of the present application, using a continuous casting machine to continuously cast molten steel for continuous casting includes: setting the continuous casting speed of the continuous casting machine to 0.9 m / min to 1.3 m / min.

[0013] The method for suppressing the periodic fluctuation of the liquid level in the crystallizer of 600MPa-grade dual-phase steel in the embodiment of the present application, for conventional slab casting of 600MPa-grade dual-phase steel, controls and optimizes the C content contained in the steel type according to the middle and upper limits, optimizes the continuous casting speed, and confirms the production conditions of the continuous casting machine, so that the periodic fluctuation of the liquid level in the crystallizer of 600MPa-grade dual-phase steel is reduced from more than ±12mm to less than ±7mm. It can effectively control the problem of periodic fluctuation of the liquid level in the crystallizer of dual-phase steel during continuous casting, uniformly cool the billet shell, prevent steel leakage accidents, and greatly improve the surface quality of the 600MPa-grade dual-phase steel ingot. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solution of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0015] Figure 1 It is a flow chart of a method for suppressing periodic fluctuation of liquid level in a 600MPa grade dual-phase steel crystallizer provided in an embodiment of the present application. DETAILED DESCRIPTION

[0016] The features and exemplary embodiments of various aspects of the present application will be described in detail below. In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, rather than to limit the present application. For those skilled in the art, the present application can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present application by illustrating the examples of the present application.

[0017] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "include..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0018] In the existing composition design of 600MPa grade dual-phase steel, the C content is generally in the peritectic steel range of about 0.09wt.%, and the alloying elements are mainly Si and Mn. At the same time, a certain amount of alloying elements such as Cr and Al are added in combination with the performance of dual-phase steel and the process characteristics of the production line.

[0019] The applicant of the present application found that: production practice shows that the fluctuation of the crystallizer liquid level is best suppressed within the range of ±5mm, and at least ±7mm is more suitable. The applicant of the present application further found that the main reason for the periodic fluctuation of the crystallizer liquid level is that: in the process of solidification of the peritectic steel with a C content of about 0.09wt.% in the continuous casting crystallizer to form a billet shell, a δ→γ phase transformation with the largest volume shrinkage will occur, resulting in a large air gap between the billet shell and the crystallizer copper plate, affecting the uniform growth of the primary billet shell, resulting in a thin and uneven billet shell after the billet leaves the crystallizer, and the billet bulges under the static pressure of the unsolidified molten steel when passing through the support section rollers. At this time, the molten steel in the core of the billet flows downward, and the bulging billet is squeezed by the rollers when passing through the support rollers, causing the liquid molten steel in the core of the billet to flow upward, and this is repeated to form a periodic fluctuation of the molten steel level in the crystallizer. For 600-grade duplex steel, not only is the C content around 0.09wt.%, but in order to obtain the desired ferrite + martensite duplex steel structure and ensure a certain martensite ratio to achieve the desired performance of the steel, a certain amount of strong hardenability elements such as Mn and Cr are often added to the 600-grade duplex steel. These elements are extremely sensitive to cooling, which aggravates the unevenness of the primary shell in the crystallizer. Therefore, in the actual production process of 600-grade duplex steel, a stronger periodic fluctuation of the crystallizer liquid level is exhibited.

[0020] In order to solve the problems of the prior art, the embodiment of the present application provides a method for effectively suppressing the periodic fluctuation of the liquid level in the 600MPa grade dual-phase steel crystallizer. The method for effectively suppressing the periodic fluctuation of the liquid level in the 600MPa grade dual-phase steel crystallizer provided by the embodiment of the present application is first introduced below.

[0021] Figure 1 A schematic flow chart of a method for effectively suppressing periodic fluctuations in a 600 MPa grade dual-phase steel crystallizer liquid level provided in an embodiment of the present application is shown.

[0022] like Figure 1 As shown, the method for effectively suppressing the periodic fluctuation of the liquid level in the 600MPa grade dual-phase steel crystallizer comprises:

[0023] S1. Provide molten steel for continuous casting. The molten steel for continuous casting shall meet the following composition requirements in terms of mass percentage: C content is 0.095wt.%~1.1wt.%; Mn content is 1.7wt.%~2.1wt.%; Si content is 0.20wt.%~0.23wt.%; Al tot: 0.02wt.%~0.08wt.%; Cr content is 0.17wt.%~0.23wt.%, and the balance is iron to reduce periodic fluctuation of the crystallizer;

[0024] S2. Use a continuous casting machine to continuously cast the molten steel for continuous casting to obtain a continuous casting slab.

[0025] The method for suppressing the periodic fluctuation of the liquid level in the crystallizer of 600MPa-grade dual-phase steel in the embodiment of the present application, for conventional slab casting of 600MPa-grade dual-phase steel, controls and optimizes the C content contained in the steel type according to the middle and upper limits, optimizes the continuous casting speed, and confirms the production conditions of the continuous casting machine, so that the periodic fluctuation of the liquid level in the crystallizer of 600MPa-grade dual-phase steel is reduced from more than ±12mm to less than ±7mm. It can effectively control the problem of periodic fluctuation of the liquid level in the crystallizer of dual-phase steel during continuous casting, uniformly cool the billet shell, prevent steel leakage accidents, and greatly improve the surface quality of the 600MPa-grade dual-phase steel ingot.

[0026] The inventors of the present application found in the process of improving the production process of dual-phase steel that the C content is closely related to the periodic fluctuation of the crystallizer. Compared with the C content of 0.08wt.% to 0.095wt.%, the periodic fluctuation of the crystallizer liquid level of 600MPa grade dual-phase steel is significantly reduced by controlling the C content in the molten steel to 0.095wt.% to 1.1wt.%. Therefore, it is advisable to control the C content in the molten steel for continuous casting to 0.095wt.% to 1.1wt.%. It should be noted that A1 tot refers to the total aluminum content in the molten steel for continuous casting.

[0027] In some embodiments of the present application, using a continuous casting machine to continuously cast molten steel for continuous casting includes: casting the molten steel for continuous casting into a crystallizer for solidification, wherein the amount of steel passing through the crystallizer needs to satisfy: the number of narrow side furnaces ≤ 500 furnaces.

[0028] In the embodiments of the present application, if the crystallizer exceeds this amount of over-steel, the quality of the continuous casting slab produced by continuous casting using the crystallizer will be uncontrolled. The over-steel amount of the crystallizer means that since the thickness of the crystallizer is fixed, the continuous casting of continuous casting slabs of different widths is achieved by increasing the width of the narrow side of the crystallizer or reducing the width of the narrow side of the crystallizer on the continuous casting production line, and in this process, the over-steel amount of the narrow side of the crystallizer is ≤105,000 tons. Since the weight of each furnace of molten steel (210 tons) is fixed, the total amount of molten steel for continuous casting that the crystallizer can carry in the continuous casting process is also limited, and the over-steel amount of the crystallizer can be limited by the number of furnaces of molten steel obtained by smelting.

[0029] In some embodiments of the present application, using a continuous casting machine to continuously cast molten steel for continuous casting includes: making the roll gap of the continuous casting machine conveying the crystallizer meet the standard requirements: ≤ + 1mm.

[0030] In the embodiments of the present application, if the roller gap is larger than this range, it means that the precision of the continuous casting machine is relatively poor, and the conveying rollers of the continuous casting machine sector play a role in supporting and conveying the continuous casting slab. In this way, the molten steel in the slab shell of the continuous casting slab is easily affected by the conveying rollers of the continuous casting machine sector to produce irregular liquid level fluctuations, which aggravates the fluctuation of the molten steel level in the crystallizer. In addition, the continuous casting slab is subjected to additional mechanical stress, and the cracks on the surface of the continuous casting slab will increase. Therefore, it is advisable to set the roller gap of the continuous casting roller, i.e., the conveying roller of the conveying crystallizer, to meet ≤ + 1mm requirement is met to reduce the large fluctuation of the molten steel level in the crystallizer caused by the excessive roll gap and the cracks in the continuous casting slab caused by mechanical stress. It should be noted that since the position of the conveyor roller is adjustable, the roll gap meeting ≤-1mm means that the distance between the slab shell of the conveyor roller for conveying the continuous casting slab and the conveyor roller is a negative value, that is, the height of the section where the adjusted conveyor roller contacts the slab shell is higher than the height of the bottom of the slab shell, and a certain force can be applied to the continuous casting slab after the position of the conveyor roller is adjusted.

[0031] In some embodiments of the present application, using a continuous casting machine to continuously cast molten steel for continuous casting includes: passing a crystallizer containing the molten steel for continuous casting through a bending section and a second cooling section of the continuous casting machine at one time, wherein the second cooling section includes a first second cooling section and a second second cooling section, the amount of steel passing through the bending section needs to satisfy: ≤1200 furnaces, the amount of steel passing through the second cooling section needs to satisfy: ≤4800 furnaces for the first second cooling section, and ≤5500 furnaces for the second second cooling section.

[0032] In some embodiments of the present application, continuously casting molten steel for continuous casting using a continuous casting machine includes: ensuring that the nozzles in sections 0-3 in the secondary cooling section of the continuous casting machine are not blocked, and the total number of blockages of the nozzles in sections 4-8 is ≤5.

[0033] In some embodiments of the present application, using a continuous casting machine to continuously cast molten steel for continuous casting includes: centering the SEN nozzle of the tundish: the inner and outer arc deviation is ≤ 2 mm.

[0034] It should be noted that the inner and outer arcs refer to the upper and lower surfaces of the continuous casting slab, respectively. If the inner and outer arc deviation is greater than 2mm, the continuous casting molten steel will have a biased flow phenomenon in the process of flowing from the SEN nozzle to the crystallizer, that is, there is more molten steel on one side and less molten steel on the adjacent other side, resulting in asymmetric flow of the continuous casting molten steel from the SEN nozzle to the crystallizer. The asymmetric flow of the continuous casting molten steel is likely to cause liquid level fluctuations in the crystallizer, as well as unsteady flow in the flow field in the crystallizer, which is also likely to cause slag entanglement defects in the crystallizer. Therefore, it is necessary to set the inner and outer arc deviation of the SEN nozzle and the crystallizer to ≤2mm.

[0035] In the embodiments of the present application, the SEN nozzle refers to the channel through which the molten steel for continuous casting in the tundish flows into the crystallizer. The SEN nozzle of the tundish for transferring the molten steel for continuous casting is aligned with the crystallizer so that the inner and outer arc deviation is reduced to less than or equal to 2 mm. This allows the molten steel for continuous casting in the crystallizer to flow evenly from the tundish to the crystallizer, reducing the fluctuation of the molten steel level caused by the asymmetric steel flow and the slag roll defect caused by the non-steady-state flow.

[0036] In some embodiments of the present application, using a continuous casting machine to continuously cast molten steel for continuous casting includes: centering the SEN nozzle of the tundish: the inner and outer arc deviation is ≤1.5mm.

[0037] In some embodiments of the present application, using a continuous casting machine to continuously cast molten steel for continuous casting includes: setting the continuous casting speed of the continuous casting machine to 0.9 m / min to 1.3 m / min.

[0038] In some embodiments of the present application, the continuous casting of the molten steel for continuous casting using a continuous casting machine includes: setting the continuous casting speed of the continuous casting machine to 0.9 m / min to 1.2 m / min.

[0039] The inventors of the present application discovered that when producing 600MPa-grade dual-phase steel, it was found that the continuous casting speed was closely related to the periodic fluctuation of the crystallizer, and the surface defects were also related to the pulling speed. The reason is that the shell of this 600MPa-grade dual-phase steel billet grows slowly, the billet shell is relatively thin, and the crack sensitivity is strong. At a higher pulling speed, the rapid contact and collision of the conveying rollers can easily cause the billet shell to rupture, resulting in aggravated periodic fluctuations of the liquid level and steel leakage. Therefore, the present application improves the existing continuous casting pulling speed of 600MPa-grade dual-phase steel, reducing the pulling speed to 0.9m / min~1.3m / min, so that the continuously cast slab in the crystallizer can form a relatively thick billet shell to reduce crack sensitivity, thereby reducing the influence of the pulling speed on the periodic fluctuation of the molten steel of the 600MPa-grade dual-phase steel in the crystallizer.

[0040] For example, the continuous casting speed of the continuous casting machine may be 1.0 m / min, 1.1 m / min, 1.2 m / min, or 1.3 m / min.

[0041] The technical solution of the present application is further illustrated by means of specific embodiments and comparative examples.

[0042] Example 1

[0043] A method for suppressing periodic fluctuation of a 600MPa grade dual-phase steel crystallizer liquid level comprises: providing molten steel for continuous casting of 600MPa grade dual-phase steel for continuous casting, the casting length is 15 furnaces, the grade is: H6000DPD, wherein, in terms of mass percentage, the composition of the molten steel for continuous casting is: C content is 0.105wt.%, Mn content is 1.9wt.%, Si content is 0.20wt.%, Altot content is 0.03wt.%, Cr content is 0.18wt.%, and the balance is iron. The continuous casting machine is used to continuously cast the molten steel for continuous casting, including: casting the molten steel for continuous casting in a crystallizer for solidification, wherein the following conditions need to be met: the amount of steel passing through the crystallizer is 225 furnaces; the amount of steel passing through the bending section of the continuous casting machine is 536 furnaces; the amount of steel passing through the second cooling section is: the amount of steel passing through the first second cooling section is 2578 furnaces, and the amount of steel passing through the second second cooling section is 3578 furnaces; and the roll gap of the continuous casting machine is within the standard requirements ( + 1mm); the nozzles of the second cooling section of the continuous casting machine in sections 0-3 are not blocked, and the total number of blockages of the nozzles in sections 4-8 is 4; the SEN nozzle is measured for centering when the molten steel for continuous casting is poured: the inner and outer arc deviation is 1.5mm, and the two-stream drawing speed of the continuous casting machine 1# and 2# is 1.3m / min. Thus, the continuous casting billet with the specification of width×length=240mm×1300mm is obtained.

[0044] Example 2

[0045] A method for suppressing periodic fluctuation of the liquid level of a 600MPa grade dual-phase steel crystallizer comprises: providing molten steel for continuous casting of 600MPa grade dual-phase steel for continuous casting, the casting length is 15 furnaces, the grade is: H6000DPD, wherein, in terms of mass percentage, the composition of the molten steel for continuous casting is: C content is 0.096wt.%, Mn content is 1.8wt.%, Si content is 0.21wt.%, Altot content is 0.02wt.%, Cr content is 0.17wt.%, and the balance is iron. The continuous casting machine is used to continuously cast the molten steel for continuous casting, including: casting the molten steel for continuous casting into a crystallizer for solidification, wherein the following conditions need to be met: the crystallizer steel overload is 240 furnaces; the bending section steel overload of the continuous casting machine is 800 furnaces; the second cooling section steel overload is: the first second cooling section steel overload is 2670 furnaces, and the second second cooling section steel overload is 3780 furnaces; and the roll gap of the continuous casting machine is within the standard requirements ( +1mm); the nozzles of the second cooling section of the continuous casting machine in sections 0-3 are not blocked, and the total number of blockages of the nozzles in sections 4-8 is 3; the SEN nozzle is measured for centering when the molten steel for continuous casting is poured: the inner and outer arc deviation is 1.8mm, and the two-stream drawing speed of the continuous casting machine 1# and 2# is 1.2m / min. Thus, the continuous casting billet with the specification of width×length=240mm×1300mm is obtained.

[0046] Example 3

[0047] A method for suppressing periodic fluctuation of a 600MPa grade dual-phase steel crystallizer liquid level comprises: providing molten steel for continuous casting of 600MPa grade dual-phase steel for continuous casting, the casting length is 15 furnaces, the grade is: H6000DPD, wherein, in terms of mass percentage, the composition of the molten steel for continuous casting is: C content is 0.108wt.%, Mn content is 1.9wt.%, Si content is 0.23wt.%, Al tot content is 0.03wt.%, Cr content is 0.19wt.%, and the balance is iron. The continuous casting machine is used to continuously cast the molten steel for continuous casting, including: casting the molten steel for continuous casting in a crystallizer for solidification, wherein the following conditions need to be met: the crystallizer has a steel overload of 300 furnaces; the bending section of the continuous casting machine has a steel overload of 654 furnaces; the second cooling section has a steel overload of 2857 furnaces for the first and second cooling sections, and a steel overload of 3756 furnaces for the second and second cooling sections; and the roll gap of the continuous casting machine is within the standard requirements ( + 1mm); the nozzles of the second cooling section of the continuous casting machine are not blocked in the 0-3 sections, and the total number of blockages of the nozzles of the 4-8 sections is 5; the SEN nozzle is measured for centering when the molten steel for continuous casting is poured: the inner and outer arc deviation is 1.2mm, and the two-stream drawing speed of the continuous casting machine 1# and 2# is 1.3m / min. Thus, the continuous casting billet with the specification of width×length=240mm×1300mm is obtained.

[0048] Example 4

[0049] A method for suppressing periodic fluctuation of a 600MPa grade dual-phase steel crystallizer liquid level comprises: providing molten steel for continuous casting of 600MPa grade dual-phase steel for continuous casting, the casting length is 15 furnaces, the grade is: H6000DPD, wherein, in terms of mass percentage, the composition of the molten steel for continuous casting is: C content is 0.101wt.%, Mn content is 1.7wt.%, Si content is 0.23wt.%, Al tot content is 0.04wt.%, Cr content is 0.20wt.%, and the balance is iron. The continuous casting machine is used to continuously cast the molten steel for continuous casting, including: casting the molten steel for continuous casting in a crystallizer for solidification, wherein the following conditions need to be met: the crystallizer has a steel overload of 225 furnaces; the bending section of the continuous casting machine has a steel overload of 538 furnaces; the second cooling section has a steel overload of 2578 furnaces for the first and second cooling sections, and a steel overload of 3578 furnaces for the second and second cooling sections; and the roll gap of the continuous casting machine is within the standard requirements (+ 1mm); the nozzles of the second cooling section of the continuous casting machine are not blocked in the 0-3 sections, and the total number of blockages of the nozzles of the 4-8 sections is 4; the SEN nozzle is measured for centering when the molten steel for continuous casting is poured: the inner and outer arc deviation is 1.5mm, and the two-stream pulling speed of the continuous casting machine 1# and 2# is 1.3m / min. Thus, the continuous casting billet with the specification of width×length=240mm×1300mm is obtained.

[0050] Comparative Example 1

[0051] A method for suppressing periodic fluctuation of a 600MPa grade dual-phase steel crystallizer liquid level comprises: providing molten steel for continuous casting of 600MPa grade dual-phase steel for continuous casting, the casting length is 15 furnaces, the grade is: H6000DPD, wherein, in terms of mass percentage, the composition of the molten steel for continuous casting is: C content is 0.800wt.%, Mn content is 1.8wt.%, Si content is 0.18wt.%, Al tot content is 0.03wt.%, Cr content is 0.18wt.%, and the balance is iron. The continuous casting machine is used to continuously cast the molten steel for continuous casting, including: casting the molten steel for continuous casting in a crystallizer for solidification, wherein the following conditions need to be met: the crystallizer has a steel overload of 225 furnaces; the bending section of the continuous casting machine has a steel overload of 536 furnaces; the second cooling section has a steel overload of 2578 furnaces for the first and second cooling sections, and a steel overload of 3577 furnaces for the second and second cooling sections; and the roll gap of the continuous casting machine is within the standard requirements ( + 1mm); the nozzles of the second cooling section of the continuous casting machine in sections 0-3 are not blocked, and the total number of blockages of the nozzles in sections 4-8 is 4; the SEN nozzle is measured for centering when the molten steel for continuous casting is poured: the inner and outer arc deviation is 1.5mm, and the two-stream drawing speed of the continuous casting machine 1# and 2# is 1.3m / min. Thus, the continuous casting billet with the specification of width×length=240mm×1300mm is obtained.

[0052] Comparative Example 2

[0053] A method for suppressing periodic fluctuation of a 600MPa grade dual-phase steel crystallizer liquid level comprises: providing molten steel for continuous casting of 600MPa grade dual-phase steel for continuous casting, the casting length is 15 furnaces, the grade is: H6000DPD, wherein, in terms of mass percentage, the composition of the molten steel for continuous casting is: C content is 0.902wt.%, Mn content is 1.9wt.%, Si content is 0.18wt.%, Al tot content is 0.05wt.%, Cr content is 0.19wt.%, and the balance is iron. The continuous casting machine is used to continuously cast the molten steel for continuous casting, including: casting the molten steel for continuous casting and solidifying it in a crystallizer, wherein the following conditions need to be met: the crystallizer has a steel overload of 225 furnaces; the bending section of the continuous casting machine has a steel overload of 536 furnaces; the second cooling section has a steel overload of 2578 furnaces for the first and second cooling sections, and a steel overload of 3578 furnaces for the second and second cooling sections; and the roll gap of the continuous casting machine is within the standard requirements ( + 1mm); the nozzles of the second cooling section of the continuous casting machine in sections 0-3 are not blocked, and the total number of blockages of the nozzles in sections 4-8 is 4; the SEN nozzle is measured for centering when the molten steel for continuous casting is poured: the inner and outer arc deviation is 1.5mm, and the two-stream drawing speed of the continuous casting machine 1# and 2# is 1.6m / min. Thus, the continuous casting billet with the specification of width×length=240mm×1300mm is obtained.

[0054] Comparative Example 3

[0055] A method for suppressing periodic fluctuation of a 600MPa grade dual-phase steel crystallizer liquid level comprises: providing molten steel for continuous casting of 600MPa grade dual-phase steel for continuous casting, the casting length is 15 furnaces, the grade is: H6000DPD, wherein, in terms of mass percentage, the composition of the molten steel for continuous casting is: C content is 0.900wt.%, Mn content is 1.8wt.%, Si content is 0.19wt.%, Al tot content is 0.04wt.%, Cr content is 0.20wt.%, and the balance is iron. The continuous casting machine is used to continuously cast the molten steel for continuous casting, including: casting the molten steel for continuous casting and solidifying it in the crystallizer, wherein the following conditions need to be met: the crystallizer has a steel overload of 600 furnaces; the bending section of the continuous casting machine has a steel overload of 536 furnaces; the second cooling section has a steel overload of 2578 furnaces for the first and second cooling sections, and a steel overload of 3578 furnaces for the second and second cooling sections; and the roll gap of the continuous casting machine is within the standard requirement range (+1mm); the nozzles of the 0-3 sections of the second cooling section of the continuous casting machine are not blocked, and the total number of blockages of the nozzles of the 4-8 sections is 4; when the continuous casting molten steel is poured, the SEN nozzle is measured for centering: the inner and outer arc deviation is 1.5mm, and the two-stream drawing speed of the continuous casting machine 1# and 2# continuous casting drawing is 1.6m / min. Thus, a continuous casting billet with a specification of width×length=240mm×1300mm is obtained.

[0056] Comparative Example 4

[0057] A method for suppressing periodic fluctuation of a 600MPa grade dual-phase steel crystallizer liquid level comprises: providing molten steel for continuous casting of 600MPa grade dual-phase steel for continuous casting, the casting length is 15 furnaces, the grade is: H6000DPD, wherein, in terms of mass percentage, the composition of the molten steel for continuous casting is: C content is 0.903wt.%, Mn content is 1.9wt.%, Si content is 0.18wt.%, Al tot content is 0.02wt.%, Cr content is 0.19wt.%, and the balance is iron. The continuous casting machine is used to continuously cast the molten steel for continuous casting, including: casting the molten steel for continuous casting and solidifying it in a crystallizer, wherein the following conditions need to be met: the crystallizer has a steel overload of 225 furnaces; the bending section of the continuous casting machine has a steel overload of 536 furnaces; the second cooling section has a steel overload of 2578 furnaces for the first and second cooling sections, and a steel overload of 3578 furnaces for the second and second cooling sections; and the roll gap of the continuous casting machine is within the standard requirements ( + 1mm); the nozzles of the second cooling section of the continuous casting machine in sections 0-3 are not blocked, and the total number of blockages of the nozzles in sections 4-8 is 4; the SEN nozzle is measured for centering when the continuous casting molten steel is poured: the inner and outer arc deviation is 2.1mm, and the two-stream drawing speed of the continuous casting machine 1# and 2# is 1.6m / min. Thus, the continuous casting billet with the specification of width×length=240mm×1300mm is obtained.

[0058] The process parameters and the quality of the continuous casting slabs of the 600 MPa grade dual-phase steel of the above embodiment and the comparative example during continuous casting are compared, and the results are recorded in the following Table 1:

[0059] Table 1

[0060]

[0061] The methods of comparative examples 1-4 and comparative examples 1-4 and the data results of Table 1 show that in the process of producing steel using a method that does not comply with the present application, the liquid level fluctuations of the 1# and 2# crystallizers are as high as 13mm~18mm and 12mm~16mm respectively, the flame cleaning loss rate is as high as 6.92%~26.2%, and there is a situation where the entire surface is peeled off. When the method of suppressing the periodic fluctuation of the liquid level in the crystallizer of 600MPa-grade dual-phase steel of the present application was used to produce the 600MPa and dual-phase steels of Examples 1-4 with the grade H600DPD, the results showed that the liquid level fluctuation in the crystallizer at the 1# pulling speed among the two-stream pulling speeds was ±4mm, and the liquid level fluctuation in the crystallizer at the 2# pulling speed was ±3mm. The steel leakage accident was 0, and the surface quality of the continuous casting slab was greatly improved. The continuous casting slab changed from the entire stripping surface and the stripping narrow surface before the improvement to the non-stripping narrow surface and the stripping partial surface, which effectively reduced the steel loss rate caused by the use of flame cleaning to 0% to 1%; and the steel loss rate of most steels using flame cleaning was reduced to below 0.25%.

[0062] Therefore, by adopting the method for suppressing the periodic fluctuation of the liquid level in the crystallizer of 600MPa-grade dual-phase steel of the embodiment of the present application, 600MPa-grade dual-phase steel is produced, and the periodic fluctuation range of the liquid level in the crystallizer of 600MPa-grade dual-phase steel can be reduced from more than ±12mm before the improvement scheme to less than ±5mm, so that the surface quality of 600MPa-grade dual-phase steel is greatly improved, the steel leakage rate in the continuous casting process is effectively reduced, and the downgrading rate and rework rate of the continuous casting slab and the loss rate of flame cleaning are reduced, and the manufacturing cycle of this type of steel product is shortened.

[0063] The above is only a specific implementation method of the present application. Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working process described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here. It should be understood that the protection scope of the present application is not limited to this. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application.

Claims

1. A method for suppressing periodic fluctuation of the liquid level in a 600MPa grade dual-phase steel crystallizer, characterized in that: include: Provide molten steel for continuous casting, which shall meet the following composition requirements in terms of mass percentage: C content of 0.095wt.% to 1.1wt.%; Mn content of 1.7wt.% to 2.1wt.%; Si content of 0.20wt.% to 0.23wt.%; Al tot: 0.02wt.% to 0.08wt.%; Cr content of 0.17wt.% to 0.23wt.%, and the balance of iron to reduce periodic fluctuation of the crystallizer; The molten steel for continuous casting is continuously cast using a continuous casting machine to obtain a continuously cast slab.

2. The method for suppressing periodic fluctuation of the liquid level in a 600MPa grade dual-phase steel crystallizer according to claim 1, characterized in that: The continuous casting of the molten steel for continuous casting using a continuous casting machine comprises: casting the molten steel for continuous casting into a crystallizer for solidification, wherein the amount of steel passing through the crystallizer needs to meet the following requirement: the number of narrow side furnaces ≤ 500 furnaces.

3. The method for suppressing periodic fluctuation of the liquid level in a 600MPa grade dual-phase steel crystallizer according to claim 1, characterized in that: The method of using a continuous casting machine to continuously cast the molten steel for continuous casting includes: passing a crystallizer containing the molten steel for continuous casting through a bending section and a second cooling section of the continuous casting machine at one time, wherein the amount of steel passing through the bending section needs to satisfy: ≤1200 furnaces, the second cooling section includes a first second cooling section and a second second cooling section, and the amount of steel passing through the second cooling section needs to satisfy: the first second cooling section ≤4800 furnaces, and the second second cooling section ≤5500 furnaces.

4. The method for suppressing periodic fluctuation of the liquid level in a 600MPa grade dual-phase steel crystallizer according to claim 3, characterized in that: The continuous casting of the molten steel for continuous casting using a continuous casting machine comprises: ensuring that the nozzles of sections 0-3 in the secondary cooling section of the continuous casting machine are not blocked, and the total number of blockages of the nozzles of sections 4-8 is ≤5.

5. The method for suppressing periodic fluctuation of liquid level in 600MPa grade dual-phase steel crystallizer according to claim 1, characterized in that: Using a continuous casting machine to continuously cast the molten steel for continuous casting includes: making the roll gap of the continuous casting machine conveying the crystallizer meet the standard requirements: ≤ + 1mm.

6. The method for suppressing periodic fluctuation of the liquid level in a 600MPa grade dual-phase steel crystallizer according to claim 1, characterized in that: The method of using a continuous casting machine to continuously cast the molten steel for continuous casting includes: centering the SEN nozzle of the tundish: the inner and outer arc deviation is ≤2mm.

7. The method for suppressing periodic fluctuation of liquid level in 600MPa grade dual-phase steel crystallizer according to claim 1, characterized in that: The method of using a continuous casting machine to continuously cast the molten steel for continuous casting includes: centering the SEN nozzle of the tundish: the inner and outer arc deviation is ≤1.5mm.

8. The method for suppressing periodic fluctuation of the liquid level in a 600MPa grade dual-phase steel crystallizer according to claim 1, characterized in that: The continuous casting of the molten steel for continuous casting by using a continuous casting machine includes: setting the continuous casting speed of the continuous casting machine to 0.9 m / min to 1.3 m / min.

9. The method for suppressing periodic fluctuation of the liquid level in a 600MPa grade dual-phase steel crystallizer according to claim 1, characterized in that: The continuous casting of the molten steel for continuous casting by using a continuous casting machine includes: setting the continuous casting speed of the continuous casting machine to 0.9 m / min to 1.2 m / min.

10. The method for suppressing periodic fluctuation of liquid level in 600MPa grade dual-phase steel crystallizer according to claim 1, characterized in that: The width×length of the continuous casting billet=240mm×1300mm.

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