A method for adjusting the liquid level setting of a crystallizer by casting sequences

Abstract

The application provides a method for adjusting the liquid level setting of a crystallizer by casting lots, comprising the following steps: collecting historical data of the crack length of the copper plate in the crystallizer and the difference between the full liquid level and the empty liquid level of the crystallizer, calculating the liquid level fluctuation value, collecting the high alarm value a1, the low alarm value a2, the high casting value b1 and the low casting value b2 of the crystallizer, and obtaining the casting liquid level range of the crystallizer; and setting the initial liquid level value and casting according to the change of the lot and the surface condition of the copper plate. According to the change of the lot, the liquid level setting value is adjusted, so that the slag line area is not overlapped in the casting process of different lots, and the technical problem that the steel coil appears horizontal crack defects due to the long-time corrosion of the slag line to the same position of the copper plate is avoided.

Description

Technical Field

[0001] This invention relates to the field of continuous casting production technology, and in particular to a method for adjusting the liquid level setting of the crystallizer in separate casting cycles. Background Technology

[0002] In high-speed continuous casting, excessively high surface temperatures and thermal stress can easily occur at the slag line location on the copper plate of the crystallizer, leading to deteriorated mechanical properties, thermal fatigue, cracking, and scratches. These problems affect the surface quality of the cast billet, and consequently cause transverse cracks with an inverted "peak" morphology in the steel coil. To slow down the erosion rate at the slag line location on the copper plate of the crystallizer and reduce cracking and scratches, it is necessary to adjust the crystallizer liquid level setting during the continuous casting process.

[0003] Related technologies employ methods that raise or lower the liquid level over time to prevent the slag line from corroding the same location on the copper plate for an extended period. However, in practical applications, the problem of transverse cracks appearing on the steel coil still exists.

[0004] In summary, there is an urgent need for a method to adjust the liquid level setting of the crystallizer in stages to solve the problems existing in the related technology. Summary of the Invention

[0005] The main objective of this invention is to provide a method for adjusting the liquid level setting of the crystallizer in stages of casting, so as to solve the technical problem of transverse crack defects in steel coils in related technologies.

[0006] To achieve the above objectives, the present invention provides a method for adjusting the liquid level setting of a crystallizer in stages, comprising the following steps:

[0007] S1: Collect historical data on the crack length of the copper plate in the crystallizer and the difference between the full liquid level and the empty liquid level ΔS in the crystallizer, calculate the liquid level fluctuation value Δh, collect the high-level alarm value a1, low-level alarm value a2, high-level casting value b1 and low-level casting value b2 of the crystallizer, and obtain the casting liquid level range of the crystallizer as max(a2, b2)~min(a1, b1);

[0008] S2: Perform casting and set an initial liquid level value; during the casting process, the difference between the liquid level setting value of the previous casting and the next casting is greater than the liquid level fluctuation value Δh, and the difference and sum of the liquid level setting value and the liquid level fluctuation value Δh of any casting are within the casting liquid level range of the crystallizer; when the difference between the liquid level setting value of a certain casting and twice the liquid level fluctuation value Δh is less than max(a2, b2), proceed to step S3;

[0009] S3: Stop casting, collect the surface condition of the copper plate, and evaluate the quality of the copper plate based on the crack situation. When the evaluation value δ≥δ0, return to step S2; when δ<δ0, stop casting and replace the copper plate; δ0 represents the qualified threshold of the copper plate.

[0010] Preferably, the range of the liquid level fluctuation value Δh is (Δh min ,Δh max ), the Δh min Δh max The expressions are as follows:

[0011]

[0012]

[0013] Where θ represents the angle between the length of the nth crack in the copper plate and the horizontal direction of the crystallizer, (l1, l2, ..., ln) n ) represents the historical data set of crack lengths in copper plates, l n ΔS represents the length of the nth crack, and ΔS represents the difference between the full liquid level and the empty liquid level in the crystallizer.

[0014] Preferably, the difference between the full liquid level and the empty liquid level of the crystallizer is the absolute value of the difference between the distance from the full liquid level of the crystallizer to the upper edge of the copper plate and the distance from the empty liquid level of the crystallizer to the upper edge of the copper plate.

[0015] Preferably, the crack length of the copper plate is in the range of 7-10 mm.

[0016] Preferably, the method further includes detecting the liquid level in the crystallizer using a liquid level detector; if the detected value is greater than a set value, the stopper rod is closed; if the detected value is less than the set value, the stopper rod is opened.

[0017] Preferably, the insertion depth of the immersion nozzle of the crystallizer is the same in the different casting cycles.

[0018] Preferably, the insertion depth is 90-110 mm.

[0019] Preferably, the copper plate qualification threshold δ0 is 8.

[0020] The beneficial effects of this invention are as follows:

[0021] This invention adjusts the liquid level setting value according to the changes in casting cycles, and calculates a suitable liquid level fluctuation value based on historical data of the crack length of the copper plate and the difference between the full and empty liquid levels in the crystallizer. This ensures that slag line areas do not overlap during different casting cycles, avoiding the technical problem of transverse crack defects in steel coils caused by prolonged slag line corrosion at the same location on the copper plate. At the same time, calculating the liquid level fluctuation value based on historical data of the crack length of the copper plate and the difference between the full and empty liquid levels in the crystallizer can, on the one hand, avoid slag line overlap, extend the service life of the copper plate and improve product quality, and on the other hand, improve the utilization efficiency of the copper plate and reduce production costs. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that all directional indicators (such as up, down, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicator will also change accordingly.

[0024] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature.

[0025] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0026] During their research on continuous casting, the inventors discovered that the method of raising or lowering the liquid level over time, as used in related technologies, still resulted in transverse cracks in steel coils in practical applications. This is because the set liquid level is merely a theoretical value. In actual casting, the liquid level fluctuates with the injection of molten steel and the continuous casting process. Consequently, the slag line area before and after liquid level adjustment overlaps, causing the copper plate in the overlapping area to be corroded by the slag line for an extended period, thus affecting product quality. Furthermore, the inventors found that the crack length in the copper plate is closely related to the range of liquid level fluctuations, and therefore provided the following technical solution:

[0027] This invention provides a method for adjusting the liquid level setting of a crystallizer in stages, comprising the following steps:

[0028] S1: Collect historical data on the crack length of the copper plate in the crystallizer and the difference between the full liquid level and the empty liquid level ΔS in the crystallizer, calculate the liquid level fluctuation value Δh, collect the high-level alarm value a1, low-level alarm value a2, high-level casting value b1 and low-level casting value b2 of the crystallizer, and obtain the casting liquid level range of the crystallizer as max(a2, b2)~min(a1, b1);

[0029] S2: Perform casting and set an initial liquid level value; during the casting process, the difference between the liquid level setting value of the previous casting and the next casting is greater than the liquid level fluctuation value Δh, and the difference and sum of the liquid level setting value and the liquid level fluctuation value Δh of any casting are within the casting liquid level range of the crystallizer; when the difference between the liquid level setting value of a certain casting and twice the liquid level fluctuation value Δh is less than max(a2, b2), proceed to step S3;

[0030] S3: Stop casting, collect the surface condition of the copper plate, and evaluate the quality of the copper plate based on the crack situation. When the evaluation value δ≥δ0, return to step S2; when δ<δ0, stop casting and replace the copper plate; δ0 represents the qualified threshold of the copper plate.

[0031] This invention adjusts the liquid level setting value according to the changes in casting cycles, and calculates a suitable liquid level fluctuation value based on historical data of the crack length of the copper plate and the difference between the full and empty liquid levels in the crystallizer. This ensures that slag line areas do not overlap during different casting cycles, avoiding the technical problem of transverse crack defects in steel coils caused by prolonged slag line corrosion at the same location on the copper plate. At the same time, calculating the liquid level fluctuation value based on historical data of the crack length of the copper plate and the difference between the full and empty liquid levels in the crystallizer can, on the one hand, avoid slag line overlap, extend the service life of the copper plate and improve product quality, and on the other hand, improve the utilization efficiency of the copper plate and reduce production costs.

[0032] In some embodiments, the quality evaluation criteria are as shown in Table 1:

[0033] Table 1 Quality Evaluation Standards

[0034] Copper plate surface condition score No cracks 10 Microcracks (crack depth ≤ 0.3mm, can be eliminated by polishing) 8 Cracking (crack depth ≤ 0.5mm, difficult to eliminate by polishing) 6 Medium-sized cracks (crack depth ≤ 1 mm) 4 More severe cracks (crack depth ≤ 1.5 mm) 2 Severe cracks (crack depth > 1.5 mm) 0

[0035] Note: If the condition is determined to be between two copper plate surface conditions, the score will be the midpoint between the two.

[0036] In some embodiments, the range of the liquid level fluctuation value Δh is (Δh min ,Δh max ), the Δh min Δh max The expressions are as follows:

[0037]

[0038]

[0039] Where, θ n Let (l1, l2, ..., ln) represent the angle between the length of the nth crack in the copper plate and the horizontal direction of the crystallizer. n ) represents the historical data set of crack lengths in copper plates, l nΔS represents the length of the nth crack, and ΔS represents the difference between the full liquid level and the empty liquid level in the crystallizer.

[0040] This invention provides a specific method for calculating liquid level fluctuation values. The position of the slag line in the height direction of the crystallizer is estimated by the crack length and the angle between the horizontal direction of the crystallizer, and a suitable liquid level fluctuation value is calculated by combining the difference between the full liquid level and the empty liquid level of the crystallizer.

[0041] In some embodiments, the difference between the full liquid level and the empty liquid level of the crystallizer is the absolute value of the difference between the distance from the full liquid level of the crystallizer to the upper edge of the copper plate and the distance from the empty liquid level of the crystallizer to the upper edge of the copper plate.

[0042] In some embodiments, the crack length of the copper plate ranges from 7 to 10 mm.

[0043] By statistically analyzing historical data on the crack length of copper plates, actual production data can be obtained in the actual production process, thus enabling the theoretical results to be better applied to actual production and to solve practical technical problems.

[0044] In some embodiments, the liquid level in the crystallizer is detected by a liquid level detector; if the detected value is greater than a set value, the stopper is closed; if the detected value is less than the set value, the stopper is opened.

[0045] Due to the various external environmental factors that affect the actual production process, in order to avoid excessive deviation between the actual liquid level and the set value, this application uses a liquid level detector on the crystallizer to detect the liquid level in the crystallizer in real time, and reduces the deviation between the detected value and the set value by opening or closing the stopper roller.

[0046] In some embodiments, the insertion depth of the crystallizer immersion nozzle is the same in different casting cycles.

[0047] In some embodiments, the insertion depth is 90-110 mm.

[0048] In some embodiments, the copper plate qualification threshold δ0 is 8.

[0049] Example

[0050] 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 weight, 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.

[0051] Example 1

[0052] A method for adjusting the liquid level setting of a crystallizer in stages includes the following steps:

[0053] S1: Collect historical data on the crack length of the copper plate inside the crystallizer (values ​​between 7-10 mm) and the difference between the full and empty liquid levels in the crystallizer, ΔS (the difference between the full and empty liquid levels is the absolute value of the difference between the distance from the full liquid level to the upper edge of the copper plate (40 mm) and the distance from the empty liquid level to the upper edge of the copper plate (193.9 mm); in this embodiment, ΔS is 153.9 mm). Calculate the liquid level fluctuation value Δh, where the value range of Δh is (Δh...). min ,Δh max ), the Δh min The value is 4.5%, Δh max The value is 6.5%.

[0054] The high alarm value of the crystallizer (95%), the low alarm value (5%), the high casting value (85%), and the low casting value (50%) were collected to obtain the casting liquid level range of the crystallizer as 50-85%.

[0055] S2: Perform casting, setting the initial liquid level value for the first casting to 73%; during the casting process, the difference between the liquid level setting value of the previous casting and the next casting is 7%, and the difference and sum of the liquid level setting value and the liquid level fluctuation value Δh of any casting are within the casting liquid level range of the crystallizer; when the difference between the liquid level setting value of a certain casting and twice the liquid level fluctuation value Δh is less than max(a2, b2), proceed to step S3;

[0056] S3: Stop casting, collect the surface condition of the copper plate, and evaluate the quality of the copper plate based on the crack situation. When the evaluation value δ≥δ0, return to step S2; when δ<δ0, stop casting and replace the copper plate; δ0 represents the qualified threshold of the copper plate, and its value is 8.

[0057] In this embodiment, the liquid level in the crystallizer is detected by a liquid level detector. If the detected value is greater than a set value, the stopper rod is closed; if the detected value is less than the set value, the stopper rod is opened.

[0058] In this embodiment, the insertion depth of the immersion nozzle of the crystallizer is the same in different casting cycles.

[0059] In this embodiment, the insertion depth is 110 mm.

[0060] Comparative Example 1: S1: Casting was performed with the liquid level set at 73%;

[0061] S2: After a single casting is completed, the surface condition of the copper plate is collected, and a quality evaluation δ is performed (evaluation standard is the same as in Example 1). When δ≥δ0, return to step S1; when δ<δ0, stop casting and replace the copper plate; δ0 represents the qualified threshold of the copper plate, and its value is 8.

[0062] Comparative Example 2: S1: Casting was carried out, with the liquid level set at 75%. Every 60 minutes of casting, the set liquid level was reduced by 2% (73% → 71% → 69%...).

[0063] S2: After a single casting is completed, the surface condition of the copper plate is collected, and a quality evaluation δ is performed (evaluation standard is the same as in Example 1). When δ≥δ0, return to step S1; when δ<δ0, stop casting and replace the copper plate; δ0 represents the qualified threshold of the copper plate, and its value is 8.

[0064] The pass rate of steel coils prepared by the methods of Example 1, Comparative Example 1, and Comparative Example 2 was statistically analyzed, and the service life of individual copper plates was also statistically analyzed. The results are shown in Table 2.

[0065] Table 2 Comparison of Steel Coil Qualification Rate and Copper Plate Service Life

[0066] project Pass rate (%) Copper plate service life (number of casting cycles) Example 1 99.8 4 Comparative Example 1 91.6 2 Comparative Example 2 92.5 2

[0067] As can be seen from the data of Example 1 and Comparative Examples 1-2, the technical solution provided by this application, compared with the prior art, not only extends the service life of copper plates, but also improves the pass rate of steel coils, effectively reduces production costs and solves the problem of transverse crack defects in steel coils in the prior art.

[0068] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method of adjusting a mold level setting for a split shot, characterized by, The method comprises the following steps: S1: collect historical data of crack length of copper plate in crystallizer and liquid level difference of full liquid level and empty liquid level of crystallizer , calculate liquid level fluctuation value , collect high alarm value a1, low alarm value a2, high casting value b1 and low casting value b2 of crystallizer, and get the casting liquid level range of crystallizer as max(a2, b2)~min(a1, b1); S2: casting is performed, and an initial liquid level value is set; during the casting, the difference between the liquid level set value of the previous casting and the liquid level set value of the subsequent casting is greater than the liquid level fluctuation value , and the difference between the liquid level set value of any casting and the liquid level fluctuation value and the sum are within the casting liquid level range of the crystallizer; when the difference between the liquid level set value of a certain casting and twice the liquid level fluctuation value is less than max(a2, b2), step S3 is entered; S3: stop pouring, collect the surface condition of the copper plate, evaluate the quality of the copper plate based on the crack condition, when the evaluation value is less than or equal to S3 , return to step S2; when the evaluation value is greater than S3 , stop pouring and replace the copper plate; S3 represents a copper plate qualified threshold value.

2. The method of claim 1, wherein, The liquid level fluctuation value The value range of the liquid level fluctuation value is (0, 1). , The expression of the liquid level fluctuation value is as follows: , The expression of the liquid level fluctuation value is as follows: ； ； wherein, represents the angle between the n-th crack length of the copper plate and the horizontal direction of the crystallizer, represents a set of historical data of crack lengths of the copper plate, represents the n-th crack length, represents the difference between the full liquid level and the empty liquid level of the crystallizer.

3. The method of claim 2, wherein, The full liquid level of the crystallizer is different from the upper edge of the copper plate, and the absolute value of the difference between the distance from the full liquid level of the crystallizer to the upper edge of the copper plate and the distance from the empty liquid level of the crystallizer to the upper edge of the copper plate.

4. The method of claim 1, wherein, The crack length of the copper plate ranges from 7 mm to 10 mm.

5. The method of claim 1, wherein, The liquid level in the crystallizer is detected by a liquid level detector, and if the detection value is greater than the set value, the stopper is closed; if the detection value is less than the set value, the stopper is opened.

6. The method of claim 1, wherein, The insertion depth of the crystallizer submerged entry nozzle is the same in different pouring times.

7. The method of claim 6, wherein, The insertion depth is 90-110 mm.

8. The method of claim 1, wherein, copper sheet acceptance threshold is 8.

Images