Method for improving success rate of one-time flame cleaning of continuous casting sheet billet

Abstract

The invention discloses a method for improving the success rate of one-time flame cleaning of a continuous casting slab, and belongs to the field of steelmaking continuous casting. The method comprises the steps that a special stack position is arranged in a reservoir area for a continuous casting slab needing to be subjected to flame cleaning, scrapped cushion blanks with the width larger than or equal to 1.7 m and the deformation quantity smaller than or equal to 2 mm are laid on the stack position in a longitudinal full laying mode, and the overall levelness of the slab to be cleaned is controlled to be smaller than or equal to 10 mm after the slab to be cleaned is placed; the program linkage logic of the flame cleaning machine is optimized, the detection time of a roller way steel clamping capturing signal is prolonged from 0.5 second to 1 second, the first-order oxygen pressure linkage is changed from the operation condition to the starting condition, and meanwhile the downstream pressure low linkage threshold value of an oxygen main pipe valve is adjusted from 10.5 kg / cm < 2 > to 9.5 kg / cm < 2 >. According to the method, through multi-dimensional collaborative optimization from blank preparation, equipment control, energy guarantee to process monitoring, the one-time success rate and operation stability of flame cleaning of the continuous casting sheet billet are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to steelmaking continuous casting, and in particular to a method for improving the success rate of one-time flame cleaning of continuous casting slabs. BACKGROUND

[0002] Instability of continuous casting slabs during casting in the continuous casting workshop of a steel mill includes slabs with liquid surface fluctuations, sudden speed drops, package changes, nozzle changes, and other production abnormalities or slabs with surface damage caused by transport rollers and cutting machines. The slabs need to be cleaned by a flame cleaning machine according to the required cleaning depth to remove the defects and impurities on the surface of the slabs. The slabs cleaned by the machine are called machine-cleaned slabs.

[0003] When the instability during continuous casting includes slabs with liquid surface fluctuations, sudden speed drops, package changes, nozzle changes, and other abnormal slabs caused by transport rollers and cutting machines, the abnormal slabs are strictly prohibited from being directly hot sent to a hot rolling mill for rolling. The slabs must be specially cleaned by a machine, manually cleaned, and regeneratively cut to check and confirm their eligibility before being sent to the next process for rolling. Otherwise, the flow of abnormal slabs will cause rolling blockage in the next process, such as casting process instability causing slag inclusion and skin buckling blockage, transport roller / cutting machine abnormality causing skin buckling blockage, and so on. The flow of serious red card / package change double pouring abnormal slabs will even cause rolling steel breakage and force the rolling line to stop. The flame cleaning machine plays an important role in the last link, and through the set cleaning depth, the impurities and defects floating on the surface of the slabs are removed to the greatest extent to ensure stable quality. Therefore, the quality assurance of machine-cleaned slabs is an important means for large steel mills to produce high-grade slabs and reduce the rolling blockage rate.

[0004] However, during the flame cleaning of the slabs, factors such as continuous casting slab type, system interlocking, compressed air, etc. will cause interruptions or poor cleaning effects during flame cleaning, such as stuck steel, missed cleaning, etc. To ensure the stability and control of the surface quality of the slabs, such defects in the continuous casting slabs need to be cleaned by flame for the second time. Such slabs are also called heavy machine-cleaned slabs. However, the slabs cleaned by flame for the second time will cause uneven thickness on the surface of the slabs, increased machine cleaning debris, and two preheating pits in the slabs, which will have a greater impact on quality, cost, and efficiency. Therefore, it is extremely necessary to improve the one-time pass rate of flame cleaning.

[0005] There is no special research and solution on improving the success rate of flame cleaning by external enterprises. Shanghai Dongzhen Metallurgical Engineering Technology Co., Ltd. proposes a head positioning and cleaning middle card steel detection system for flame cleaning of slab (CN201910056291.9), which mainly uses a laser range finder to realize accurate measurement of the size of the slab, and relies on accurate size data to accurately position and stop through PLC, so as to realize the accuracy of the preheating position of the head cleaning of the slab. In addition, Wuhan Wugang Industry Gold Source Material Industrial Development Co., Ltd. proposes a one-key cleaning system and method for slab flame cleaning machine (CN201911176939.2), which mainly uses sensors and signal feedback to realize the automation of the action of flame cleaning through PLC. The existing technology realizes new technology and adds new functions by adding new equipment or adding control programs, but does not propose a related solution to the problems in the flame cleaning process, and still cannot solve the process exception problem. SUMMARY

[0006] The purpose of the present application is to provide a method for improving the success rate of one-time flame cleaning of continuous casting slab, aiming to improve the success rate of one-time flame cleaning of slab, reduce the occurrence of secondary or more flame cleaning of slab, and improve the yield of slab and the surface and rolling quality of slab.

[0007] The factors affecting the success rate of one-time flame cleaning of slab mainly include four main problems: abnormal and non-horizontal slab shape of continuous casting slab, program interlocking signal interference and poor setting range, unstable compressed air pressure of flame cleaning machine body, and long-term failure of flame cleaning pool system monitoring.

[0008] I. Abnormal and non-horizontal slab shape of continuous casting slab

[0009] The abnormal and non-horizontal slab shape of continuous casting slab mainly includes slab sagging and slab warping. In the cleaning process, the movement amplitude is too large, which is easy to cause the slab to hit the machine cleaning body or stop against the roller, causing the body to retreat and miss cleaning, steel clamping, and scratch defects. Through long-term tracking experiment and cumulative data analysis, it is found that when the deformation of the continuous casting slab shape exceeds 10 mm (warping or sagging), the slab shape will hit the machine cleaning body nozzle during the machine cleaning process, causing the body to retreat and miss cleaning or stop against the roller, causing steel clamping abnormalities.

[0010] In the continuous casting slab yard, special stacks are divided for flame cleaning slabs. According to the stacking structure of the yard and the size of the slab produced by the continuous casting machine, the best way is to pad the slab according to the maximum size that can be produced or to find the average size of the production by compromise. By using the longitudinal full-paving method, the levelness of the flame cleaning machine slab is improved to ensure smooth transportation during the flame cleaning process.

[0011] II. Interlock signal interference and poor setting range:

[0012] Interlock is essentially to prevent the expansion of abnormal occurrence, so as to protect the equipment, but the range of interlock is not reasonable, or the signal interference caused by the complex environment of the scene, will frequently cause interlock alarm, resulting in frequent emergency shutdown of steel defects.

[0013] ① The forward command and forward running feedback of the drive block are changed to frequency converter operation to prevent false triggering caused by interference signals; at the same time, the roll steel capture signal is optimized from 0.5S to 1S to prevent fluctuation interference, and the system detection sensitivity false triggering causes abnormal steel;

[0014] ② The machine cleaning first-order oxygen pressure interlock is changed from the running condition to the starting condition, which triggers an alarm reminder during the running process, and the next block cleaning interlock protection is avoided when the block cleaning occurs. The abnormal problem of steel is avoided. The low pressure of the oxygen manifold valve is adjusted from 10.5 Kg / cm2 to 9.5 Kg / cm2, which reduces the excessive gas consumption of the oxygen pressure and causes the low pressure interlock to occur;

[0015] ③ The machine cleaning program link is added in the finishing PDA to monitor the machine cleaning data, which is convenient for fault query and processing.

[0016] III. Unstable compressed air pressure of flame cleaning machine body:

[0017] The process of flame cleaning requires that the minimum compressed air pressure meet 0.6MPa, otherwise the body cannot be stabilized during cleaning, resulting in retraction and missing cleaning. Due to the large number of compressed air user points in the plant, and the variable amount of each time period, the machine cleaning process is often affected by the large amount of gas used by other user points, resulting in insufficient air pressure during machine cleaning, which causes the slab to be missed during cleaning.

[0018] The best solution is to solve this problem from the design. The design ensures that the compressed air to the machine cleaning body gas port pressure meets 0.6MPa. If it is not considered in the early design and there are many user points, according to the amount of gas measured and tracked from the main pipe to the user end, the gas inlet interface of the user end is divided to avoid too many user points concentrated in one interface, which causes the body pressure to be unstable.

[0019] IV. Flame cleaning molten pool system monitoring damage and high long-term failure:

[0020] The machine cleaning molten pool system camera monitoring is installed directly above and obliquely below the cleaning position, and the function is mainly to detect whether the cleaning starts and the process is abnormal in real time, so that the operator can find it in time. However, due to the poor environment of the cleaning position, a large amount of water vapor and slag splashes during the machine cleaning process, resulting in a high damage rate of the lens of the molten pool camera, which causes the function to be invalid for a long time.

[0021] ① The built-in cooling air in the molten pool system blows from inside to outside, and the pressure is kept at 4-7 bar;

[0022] ② A flat head gas outlet blowing pipeline is added, the diameter of the gas outlet is controlled to be less than or equal to 3 mm, so that the compressed air forms an air knife at the moment of blowing, which can effectively block the oxidized slag and water mist, and the built-in cooling air is combined to ensure the cleanliness of the molten pool lens and improve the service life of the lens, so that the operator can detect and adjust in real time.

[0023] Beneficial effects: Through multi-dimensional collaborative optimization from blank preparation, equipment control, energy security to process monitoring, the one-time success rate and operation stability of the continuous casting slab flame cleaning are significantly improved. Specifically, the high flatness scrap pad slab is fully laid on the special stacking position, effectively controlling the overall flatness of the slab within 10 mm, avoiding the card steel or uneven cleaning caused by upwarping or down buckling; by prolonging the detection time of the roller card steel signal, changing the first-order oxygen pressure interlocking from the running condition to the starting condition, and adjusting the interlocking threshold from 10.5 kg / cm² to 9.5 kg / cm², the false stop caused by instantaneous interference or pressure fluctuation is greatly reduced; an independent compressed air supply pipeline is configured to ensure that the compressed air pressure during cleaning is stably maintained at more than 0.6 MPa, ensuring the reliability of the burner ignition and the stability of the flame; at the same time, a gas knife blowing device is added at the molten pool monitoring camera, combined with the double air curtain protection inside and outside, effectively preventing water vapor and oxidized slag from adhering to the lens, ensuring the long-term clarity and reliability of the vision system. After the above measures are comprehensively implemented, the one-time success rate of flame cleaning is improved from less than 85% to more than 98%, significantly reducing the return cleaning rate, equipment failure downtime and manual intervention frequency, not only improving the production line operation efficiency, but also enhancing the surface quality guarantee capability of high-end steel, which has outstanding technical effects and significant economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is the application effect diagram of the present application. DETAILED DESCRIPTION

[0025] In order to make the technical scheme of the present application clearer, the present application will be further described in detail below in combination with the drawings and specific embodiments.

[0026] Embodiment 1

[0027] A method for improving the one-time flame cleaning success rate of continuous casting slab, comprising:

[0028] (1) The slab shape of continuous casting slab is affected by many factors during production and output, such as improper internal cooling method in the continuous casting machine, water leakage of the fan-shaped segment, poor water angle of the cutting roller, and too many slabs being produced at the same time for flame cleaning, etc. If the continuous casting slab is deformed by more than 10 mm due to the above factors, defects such as slab leakage, scratches, and steel sticking will occur if direct flame cleaning is performed. Since there are too many factors, it is difficult to completely control and solve the problem. The present technical method is mainly used to correct and restore the level when the slab shape deformation is greater than or equal to 10 mm.

[0029] Considering the large area of Zhanjiang continuous casting slab yard and the lack of slab resources, according to the distribution of machine cleaning capacity, 9 and 6 stacks in the north and south of the yard are designated as machine cleaning stacks. According to the average size of the caster production, 18 pieces of scrap cushion slab with a width of ≥1.7m and a deformation of ≤2mm are found, and the cushion slab is laid in a longitudinal full-paving manner, leaving a 1.2m safety walkway gap between the stacks. When the slab deformation exceeds the standard or cannot be cleaned in time, use the overhead crane to lower the line to the special stack. One is to avoid the problem of inaccurate placement of the crane, and the other is to solve the problem of slab shape deformation caused by uneven stack. Finally, cover the slab with a cap to ensure that the level of the flame cleaning slab meets ≤10mm.

[0030] (2) The principle of roller steel sticking capture chain alarm is that when the slab flame cleaning process is blocked and cannot be transported, the program detects and triggers a chain alarm to cancel the flame cleaning, avoiding continuous melting of the continuous casting slab at the same position, causing the slab to break or burn the body burner, thereby protecting the safety of the flame cleaning machine body. In view of the program chain signal interference problem, through the combination of alarm period monitoring review and background text curve analysis, it is determined that the flame cleaning condition is met, but the program triggers a chain alarm after 0.5S detection due to signal interference, causing the slab to stick steel abnormally. In order to ensure the protection of the equipment body when real steel sticking occurs, the roller steel sticking capture signal is optimized from the original 0.5S to 1S to prevent false alarm caused by fluctuation interference in the 0.5S-0.9S interval. At the same time, the machine cleaning program link is added in the finishing PDA to monitor the machine cleaning data, which is convenient for fault query and processing.

[0031] In addition, when cleaning large-size continuous casting slabs in the flame cleaning machine, the pressure behind the total pipe valve is lower than 11 Kg / cm2 due to large gas consumption, at which time the oxygen ball tank triggers the gas supplement condition, but due to the influence of the ball tank gas supplement speed, the gas consumption will gradually decrease to 10.5 Kg / cm2, triggering the low pressure alarm of the body oxygen to interrupt the flame cleaning. The principle is mainly to protect the slab from insufficient melting caused by the pressure being lower than 10.5 Kg / cm2, which is the default pressure that cannot meet the flame cleaning. Through experimental tracking, even if the pressure is ≤10.5 Kg / cm2 > 9.5 Kg / cm2 during the flame cleaning process, the flame cleaning effect is still qualified, and considering the risk and loss cost of the slab leakage and slab steel sticking, the leakage of the slab can be cleaned by manual local cleaning, but the risk and disposal cost of the slab steel sticking are much higher than that of the slab leakage, so when the low pressure of the oxygen total pipe valve is adjusted from 10.5 Kg / cm2 to 9.5 Kg / cm2, the first-order oxygen pressure interlock is changed from the running condition to the starting condition, and when the pressure is lower than 9.5 Kg / cm2 during the running process, the system only serves as a reminder and does not interrupt, and the interlock protection cannot be cleaned before the next continuous casting slab cleaning, avoiding the abnormality of the slab sticking when cleaning the slab.

[0032] (3) The compressed air used in the body of the flame cleaning machine is mainly used to push the body to close and stabilize within a certain range during the flame cleaning process, which requires a minimum of 0.6 MPa. However, due to the addition of multiple user points in the Zhanjiang steel plant, the compressed air pressure fluctuates greatly during the cleaning process of the flame cleaning machine, and the consumption is not fixed in each time period, which causes the cleaning process to be often affected by the large gas consumption of other user points, resulting in the compressed air pressure dropping to 0.55-0.57 MPa, which is insufficient to cause the slab to leak during the cleaning process.

[0033] Through tracking the gas consumption at each point during the cleaning process, it is found that the gas outlet for phosphorus removal is always open, causing the body gas consumption to be low. In order to solve the shunting problem, a pipe interface is re-opened at the front end of the DN200 total pipe in the plant, and a DN50 small diameter pipe is laid to give the cleaning machine a special phosphorus removal and purging, which not only meets the phosphorus removal gas consumption of 5 Kg / cm2, but also solves the problem of shunting the body gas consumption of the original phosphorus removal gas at the end, ensuring that the body air pressure is stable and maintained between 0.6-0.62 MPa, and the body does not have abnormal retraction.

[0034] (4) The flame cleaning machine is equipped with a flame molten pool system. This molten pool system mainly uses high-definition high-temperature cameras installed directly above and diagonally below the cleaning position. Its main function is to detect in real time whether there are any abnormalities in the start and process of cleaning, so that the operator can detect them in time. However, due to the harsh environment at the cleaning position, a large amount of water vapor and slag splashes during the machine cleaning process, resulting in a very high damage rate of the lens of the molten pool camera. Basically, after replacing it, the lens will be stuck to the slag after cleaning 1-2 slabs and cannot be viewed, resulting in the long-term failure of this function. As a result, the operator cannot judge the baking and preheating status of the slab during the flame cleaning process, and uneven preheating often occurs, resulting in the slab being missed during cleaning.

[0035] To improve the lifespan of the camera lenses in the molten pool system, leaks were first plugged and sealed in the built-in cooling air pipeline of the molten pool system. This ensured that the built-in cooling air pressure was maintained at 4-7 bar, blowing from the inside out. Simultaneously, a new compressed air supply line was added, and a flat-headed air outlet was welded to the pipe end. The outlet diameter was controlled to be ≤3mm, and the pressure was maintained at 4-7 bar. This created an "air knife" effect when the compressed air was blown out, effectively blocking oxide slag and water mist. Combined with the built-in cooling air, this ensured the cleanliness of the molten pool lenses. After adding this "air knife," the lifespan of the molten pool camera lenses increased from an average of 2 lenses to 1 month. The molten pool monitoring function was restored, allowing operators to confirm any abnormalities during the start-up and process of flame cleaning in real time. Abnormalities such as uneven preheating before start-up could be detected and stopped immediately. After adjusting the equipment, the cleaning was restarted, resolving the issue of large-scale, substandard leaks during start-up.

[0036] Application effect

[0037] like Figure 1 As shown, from 2017 to 2021, Zhanjiang Steelmaking Continuous Casting required secondary flame cleaning (also known as heavy-duty cleaning) of 905 slabs due to cleaning defects caused by instability in the cleaning process. This averaged 181 slabs requiring heavy-duty cleaning each year. Assuming an average loss of 1 ton per slab during flame cleaning, this resulted in a loss of 905 tons of finished steel over the five years, significantly impacting production costs, efficiency, and quality. In May 2022, a big data analysis of the previous five years was conducted to address four main causes, and corresponding technologies and methods were developed. This resulted in a significant reduction in the number of slabs requiring heavy-duty cleaning. The number in 2022 decreased by 131 slabs compared to the average of the previous five years (a 72% decrease), and in 2023 it decreased by 17 slabs compared to 2022 (a 34% decrease). Furthermore, data verification over two consecutive years confirmed the stability and effectiveness of this technology.

[0038] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the patent scope of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for improving the success rate of single-pass flame cleaning of continuously cast slabs, characterized in that, Includes the following steps: S1. For continuous casting slabs that require flame cleaning, a dedicated stacking position is set up in the storage area, and scrap pads with a width ≥1.7m and a deformation ≤2mm are laid on the stacking position in a longitudinal full-lay manner so that the overall levelness of the slab to be cleaned is controlled to ≤10mm after placement. S2. Optimize the program interlock logic of the flame cleaning machine, extending the detection time of the roller conveyor steel jamming capture signal from 0.5 seconds to 1 second, and changing the first-order oxygen pressure interlock from an operating condition to a start-up condition. Simultaneously, the low pressure alarm interlock threshold after the oxygen main valve is increased from 10.5 kg / cm². 2 Adjusted to 9.5 kg / cm 2 ; S3. An independent compressed air supply pipeline is configured for the flame cleaner body to ensure that the compressed air pressure is maintained stably above 0.6MPa during the cleaning process; S4. An air knife blowing device is added to the camera of the flame cleaning molten pool monitoring system. The device sprays 4~7 bar compressed air through a flat-headed air outlet with a diameter of ≤3mm. It works in conjunction with the built-in cooling airflow to prevent water vapor and oxide slag from adhering to the lens.

2. The method for improving the success rate of single-pass flame cleaning of continuously cast slabs according to claim 1, characterized in that, Nine dedicated stacking stations are set up in the north area of ​​the warehouse and six in the south area, with a 1.2m safety walkway gap reserved between adjacent stacking stations.

3. The method for improving the success rate of single-pass flame cleaning of continuously cast slabs according to claim 1, characterized in that, An independent compressed air supply line is drawn from the front end of the DN200 main pipe in the plant, and then through a DN50 pipeline to supply the flame cleaning machine for dephosphorization purging and pressure stabilization, avoiding pressure fluctuations caused by sharing the terminal interface with other air-using equipment.

4. The method for improving the success rate of single-pass flame cleaning of continuously cast slabs according to claim 1, characterized in that, The air knife purging device is connected in parallel with the built-in cooling air pipeline of the molten pool system. Both maintain a pressure of 4~7 bar, forming a double air curtain to protect the camera lens.

5. The method for improving the success rate of single-pass flame cleaning of continuously cast slabs according to claim 1, characterized in that, The flame cleaning machine program monitoring link is integrated into the finishing PDA system to collect and store the operating parameters and alarm information during the cleaning process in real time.

6. The method for improving the success rate of single-pass flame cleaning of continuously cast slabs according to claim 1, characterized in that, When the deformation of a continuously cast slab exceeds 10mm due to production abnormalities, it is prohibited to directly enter the flame cleaning process. It must first be hoisted to the designated stacking position for horizontal correction before cleaning.

7. The method for improving the success rate of single-pass flame cleaning of continuously cast slabs according to claim 1, characterized in that, After the oxygen pressure interlock adjustment, if the pressure drops below 9.5 kg / cm² during the current slab cleaning process... 2 The alarm will be triggered without interrupting the cleaning process, but the cleaning procedure will be prohibited from starting if the pressure is not restored before the next slab is started.

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