A method for adjusting the size of a slab cut in a continuous casting strand by means of cutting speed online control

Abstract

The application discloses a method for adjusting the size of a cutting tumor of a continuous casting billet through an online cutting speed control, and belongs to the field of steelmaking and continuous casting. The method is applied to a continuous casting production line comprising a flame cutting machine, a straightening and leveling machine and a burr machine, and comprises the following steps: according to the cross section specification of the billet, process parameters are retrieved and edge positioning is completed; the automatic cutting mode is switched to; according to the width of the billet, the length of the fixed size and the basic cutting speed, an adaptive cutting speed coefficient is selected, and the oxygen pressure and the height of the cutting nozzle are adjusted; the cutting is automatically started at the set length of the fixed size; the burr thickness is detected online at the burr machine side, the burr thickness is taken as a feedback signal, when the thickness is less than or equal to 1 mm, the pulling speed and the cutting speed are synchronously reduced, when the thickness is greater than or equal to 1.5 mm, the original speed is adjusted back, and a closed loop control loop is formed. The application solves the technical problems that the size of the cutting tumor cannot be accurately controlled online in the process of the flame cutting of the existing continuous casting billet, and that the residual cutting tumor causes scabbing defects in subsequent rolling, does not need to additionally increase equipment investment, is easy to implement, and has wide industry applicability.

Description

Technical Field

[0001] This invention belongs to the field of steelmaking continuous casting technology, specifically relating to a method for adjusting the size of the cut mark on a continuously cast billet by online control of the cutting speed. Background Technology

[0002] Continuous casting (CVS) is a production process in which high-temperature molten steel is continuously poured into a water-cooled crystallizer. After initial solidification to form a billet shell, the billet is continuously pulled out using a straightening machine. Following secondary cooling, straightening, and length-cutting, the final billet of the desired specifications is obtained. Due to its significant advantages such as short production process, high metal yield, low energy consumption, and ease of automation, CVS technology has become the mainstream billet forming process in modern steel production and is widely used globally.

[0003] In continuous casting production lines, length cutting is a crucial process for transforming cast billets from continuous production to single-length billets. Currently, the most common length cutting method in the industry is flame cutting. The basic principle of flame cutting is as follows: first, a preheated flame is used to heat the part of the cast billet to be cut to above the metal's ignition point. Then, high-pressure cutting oxygen is introduced, causing the heated metal to undergo a violent exothermic oxidation reaction with pure oxygen, generating liquid metal oxide slag. Simultaneously, the mechanical force of the high-speed cutting oxygen stream blows the slag away from the cut, thus achieving continuous separation of the cast billet. Flame cutting has advantages such as simple and reliable equipment, stable cutting surface quality, and wide applicability to a wide range of cast billet cross-sections, and is widely used in various square billet, rectangular billet, and slab continuous casting production lines.

[0004] However, during flame cutting, it is inevitable that molten metal and oxide slag will splash downwards from the cut. Under the combined influence of the cutting oxygen flow and gravity, these high-temperature liquid substances flow along the lower edge of the cut surface and adhere to the lower edge and surface of the billet cut. As the cutting process progresses, these adhered substances gradually cool and solidify, forming irregular protruding mixtures of metal and slag along the lower edge of the billet cut surface, commonly referred to in the industry as "cutting nodules" or "cutting burrs." The size of the nodules is influenced by a combination of factors, including cutting speed, oxygen pressure, nozzle height, billet surface temperature, and the chemical composition of the billet.

[0005] For certain steel grades, due to their chemical composition and physical properties, the burrs formed during the cutting process can form a strong metallurgical bond with the billet matrix after cooling and solidification. This manifests as the burrs firmly adhering to the lower edge and surface of the billet end. Such strongly bonded burrs are often difficult to completely remove using only the conventional burr removal equipment—the deburring machine—equipped in the continuous casting production line. Deburring machines typically use mechanical impact, scraping, or milling to remove burrs from the billet end. However, for burrs with strong adhesion and high hardness, a certain height of burr will still remain at the billet end after removal.

[0006] These residual burrs are pressed directly into the steel substrate surface by the rolls during subsequent rolling processes. Under high-temperature rolling conditions, the residual burrs cannot form a complete metallurgical bond with the steel substrate, instead forming metal folds or layers on the steel surface, the so-called "scalding" defect. Scalding defects are a common and serious defect in steel surface quality, directly affecting the appearance quality and performance of the product. Steel products with scalding defects may require surface grinding, increasing processing costs; in severe cases, they may lead to product downgrading or even scrapping, resulting in significant yield losses and economic losses.

[0007] Furthermore, continuous casting is a continuous process, and various fluctuations in operating conditions are inevitable in actual production. For example, when anomalies occur in subsequent processes requiring temporary stops of straightening or when production organization adjustments lead to a reduction in casting speed, the residence time of the billet in the cutting zone will be correspondingly extended, resulting in a decrease in the surface temperature of the billet and an intensification of surface oxidation, forming a thicker layer of iron oxide. Under such surface conditions, flame cutting will be affected by the penetration ability of the flame, the cutting speed, and the fluidity of the slag, making it difficult to control the size and shape of the burr, further increasing the difficulty of burr removal.

[0008] In existing technologies, the methods for addressing the problem of burr removal are relatively limited. Some production lines reduce burr by adjusting cutting parameters (such as reducing cutting speed and increasing oxygen pressure), but these adjustments are often qualitative, based on operator experience, lacking a real-time feedback mechanism and unable to provide precise dynamic control based on the actual size of the burr. Some production lines also attempt to address the problem of incomplete burr removal by improving the structure of the deburring machine or increasing its deburring capacity, but this requires increased equipment investment and modification costs, and is not a fundamental solution.

[0009] Therefore, how to achieve online, real-time, and precise control of the size of the burr during the flame cutting process of continuously cast billets without increasing equipment investment, so that the burr is always kept within the range that the burr machine can completely remove, and fundamentally avoid residual burrs forming scab defects in subsequent steel rolling processes, is a technical problem that urgently needs to be solved in the current continuous casting production field. Summary of the Invention

[0010] In view of this, the purpose of the present invention is to solve the above problems and provide a method for adjusting the size of the cut mark on a continuously cast billet by online control of the cutting speed.

[0011] To achieve the above objectives, the present invention provides the following technical solution: A method for adjusting the size of the burr mark on a continuously cast billet by online control of the cutting speed, applied to a continuous casting production line including a flame cutter, a straightener, and a deburring machine, includes the following steps: Step 1: Based on the cross-sectional specifications of the billet to be cut, retrieve the corresponding process parameter group in the flame cutting control system, activate the secondary pressure preheating function, and position the edge of the billet in semi-automatic mode to determine the cutting starting point. Step 2: After edge positioning is complete, switch the flame cutter to automatic cutting mode; Step 3: Based on the billet width, fixed length, and basic cutting speed, select an appropriate cutting speed coefficient, and adjust the cutting oxygen pressure and nozzle height to the corresponding process range; Step 4: When the straightening machine conveys the billet to the set length, the flame cutter starts automatically. The cutting torch preheats from one edge of the billet and completes continuous cutting from top to bottom. Step 5: On the deburring machine side, the thickness of the burr at the end of the billet after cutting is detected online, and the detected burr thickness is used as a feedback signal. When the burr thickness is ≤ the first thickness threshold, the drawing speed and cutting speed are reduced simultaneously. When the burr thickness is ≥ the second thickness threshold, the drawing speed and cutting speed are adjusted back to the original speed, forming a closed-loop control loop based on the burr thickness, so as to realize the online dynamic control of the burr size.

[0012] Furthermore, in step one, after moving the cutting gun to a position 10-20mm away from the edge of the billet, the edge positioning button is pressed, and the system automatically identifies and completes the precise positioning of the cutting starting point.

[0013] Furthermore, in step three, the cutting speed coefficient ranges from 1.8 to 3.5.

[0014] Furthermore, the cutting speed coefficient is set in segments according to the different cross-sectional specifications of the cast billet.

[0015] Furthermore, in step three, the cutting oxygen pressure is adjusted to 0.8–1.1 MPa.

[0016] Furthermore, in step three, the height of the cutting nozzle is adjusted so that the distance between the top of the blue flame core of the cutting flame and the top surface of the billet is maintained at 20-30 mm.

[0017] Furthermore, in step four, the trigger position for the automatic start of the flame cutting machine is above the initial position of the limit cutting roller conveyor.

[0018] Furthermore, the first thickness threshold is 1 mm, and the second thickness threshold is 1.5 mm.

[0019] Furthermore, before step five, the process includes: when the production process is interrupted or the drawing speed is reduced, resulting in a decrease in the surface temperature of the billet cutting area and an increase in the degree of oxidation, the cutting speed of the cutting torch is slowed down for areas with a higher degree of oxidation on the billet surface, and the cutting speed is restored to the original speed after the cutting passes through the area.

[0020] The beneficial effects of this invention are as follows: 1. This invention establishes a closed-loop control circuit based on burr thickness, performs online real-time detection of burr thickness on the burr machine side, and uses the detection data as feedback signal to dynamically adjust the pulling speed and cutting speed. This breaks through the limitations of the prior art that relies on the operator's experience for qualitative adjustment, and realizes precise and automated online control of the burr size, ensuring that the burr is always within the size range that the burr machine can completely remove, thus fundamentally solving the problem of burr residue.

[0021] 2. This invention retrieves the corresponding process parameter set in the control system according to the cross-sectional specifications of the billet, and selects an appropriate cutting speed coefficient based on the billet width, fixed length and basic cutting speed. This achieves precise matching between the cutting process parameters and the billet specifications, effectively controlling the amount of slag generated and the splashing behavior during the cutting process, and reducing the size of the cut head from the source of the cutting process.

[0022] 3. This invention controls the cutting oxygen pressure within the range of 0.8 to 1.1 MPa and adjusts the nozzle height to maintain the distance between the top of the blue flame core and the top surface of the billet at 20 to 30 mm. This ensures the optimal match between the heat input of the cutting flame and the cutting oxygen blowing force. While ensuring the quality of the cutting section, it effectively controls the amount and adhesion range of molten slag splashing, further reducing the size of the cut end.

[0023] 4. This invention addresses the abnormal situation where iron oxide scale (black scale) appears on the surface of the billet due to the suspension of straightening or reduction of drawing speed during the production process. By slowing down the cutting speed in areas with deeper oxidation and restoring the original speed after the normal area is restored, this invention effectively solves the problems of abnormally large cut-off size and unstable cutting quality under abnormal conditions, ensuring the consistency and controllability of cut-off size under various working conditions.

[0024] 5. This invention switches the flame cutting machine to automatic cutting mode and uses the system to automatically identify and complete edge positioning and cutting start point determination, which reduces the impact of manual intervention and operational differences on cutting quality, improves the stability and repeatability of the cutting process, and is conducive to the consistency of the cut size control effect.

[0025] 6. This invention does not require additional equipment modification or investment in existing flame cutting machines and deburring machines in continuous casting production lines. It can achieve online control of the cut-off size simply by optimizing the configuration of process parameters and improving the control strategy. It is easy to implement, does not affect the normal production rhythm, and has significant economic benefits and wide industry applicability.

[0026] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Detailed Implementation

[0027] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0028] Example 1 A method for adjusting the size of the cut mark on a continuously cast billet by online control of the cutting speed is applied to a continuous casting production line that includes a flame cutter, a straightener, and a deburring machine. The specific implementation steps are as follows: Step 1: Process Parameter Selection and Edge Positioning. Based on the cross-sectional specifications of the billet to be cut, retrieve the corresponding process parameter set from the process parameter database of the flame cutting control system. Activate the secondary pressure preheating function, and move the cutting torch to the preset position 10-20mm from the edge of the billet in semi-automatic operation mode. Then press the edge positioning button. The system automatically identifies the edge contour of the billet through the built-in sensor and accurately positions the cutting start point.

[0029] Step 2: Mode Switching. After edge positioning is complete, switch the flame cutter's operating mode from semi-automatic to automatic cutting mode, and the system will enter automatic waiting-to-cut state.

[0030] Step 3: Selection of Cutting Speed ​​Coefficient and Adjustment of Process Parameters. Based on the current width, length, and basic cutting speed of the billet, select an appropriate cutting speed coefficient in the control system. The speed coefficient ranges from 1.8 to 3.5 and can be set in segments according to different cross-sectional specifications of the billet. For example, a lower speed coefficient can be selected for small-section billets, and a higher speed coefficient for large-section billets. Simultaneously, adjust the cutting oxygen pressure to the range of 0.8–1.1 MPa and adjust the nozzle height to maintain a distance of 20–30 mm between the tip of the blue flame core and the top surface of the billet, ensuring optimal matching between flame heat input and cutting oxygen blowing force.

[0031] Step 4: Automatic Cutting. The continuously cast billet is continuously pulled out by the straightening machine. When the billet reaches the set length (i.e., above the initial point of the limit cutting roller), the flame cutter automatically starts. The cutting torch preheats from one edge of the billet. After sufficient preheating, it continuously cuts the billet from top to bottom, achieving fixed-length segmentation.

[0032] Handling Abnormal Operating Conditions: During the cutting process, when abnormal conditions such as stoppage of straightening or reduction in drawing speed occur, the surface temperature of the billet cutting area drops and oxidation intensifies due to prolonged dwell time, forming a thicker layer of iron oxide scale (i.e., the surface color turns black). In this case, for areas with a deeper degree of oxidation on the billet surface, the cutting speed of the corresponding cutting torch should be slowed down to ensure cutting penetration ability and cutting quality under the iron oxide scale condition; after the cutting torch has cut through the oxidized area, the cutting speed should be restored to the original set speed for normal cutting.

[0033] Step 5: Online Detection and Closed-Loop Feedback Control of Burr Thickness. An online detection device is installed on the side of the deburring machine to detect the thickness of residual burrs at the end of the billet after deburring. The detected burr thickness is used as a feedback signal and compared with a preset thickness threshold: when the burr thickness is ≤1mm (first thickness threshold), it indicates that the current burr is extremely thin, and the cutting head may be too large. At this time, the system simultaneously reduces the drawing speed and cutting speed to slow down the cutting speed and increase the cutting heat input, thereby reducing the size of the cutting head; when the burr thickness is ≥1.5mm (second thickness threshold), it indicates that the cutting head has been controlled within an appropriate range, the deburring machine can effectively remove the burr, and the system adjusts the drawing speed and cutting speed back to the original set speed to restore the normal production rhythm.

[0034] Through the aforementioned closed-loop feedback control mechanism, rapid and effective online dynamic control of the burr size is achieved during the continuous casting billet cutting process. This method requires no additional equipment investment; by optimizing existing cutting process parameters and employing a real-time feedback control strategy based on burr thickness, the burr size can be consistently controlled within a range that the burr machine can completely remove. This effectively avoids the problem of scab defects forming at the beginning and end of the steel due to burr residue, thereby improving the steel yield.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for adjusting the size of the burr cut on a continuously cast billet by online control of the cutting speed, applied to a continuous casting production line including a flame cutter, a straightener, and a deburring machine, characterized in that... Includes the following steps: Step 1: Based on the cross-sectional specifications of the billet to be cut, retrieve the corresponding process parameter group in the flame cutting control system, activate the secondary pressure preheating function, and position the edge of the billet in semi-automatic mode to determine the cutting starting point. Step 2: After edge positioning is complete, switch the flame cutter to automatic cutting mode; Step 3: Based on the billet width, fixed length, and basic cutting speed, select an appropriate cutting speed coefficient, and adjust the cutting oxygen pressure and nozzle height to the corresponding process range; Step 4: When the straightening machine conveys the billet to the set length, the flame cutter starts automatically. The cutting torch preheats from one edge of the billet and completes continuous cutting from top to bottom. Step 5: On the deburring machine side, the thickness of the burr at the end of the billet after cutting is detected online, and the detected burr thickness is used as a feedback signal. When the burr thickness is ≤ the first thickness threshold, the drawing speed and cutting speed are reduced simultaneously. When the burr thickness is ≥ the second thickness threshold, the drawing speed and cutting speed are adjusted back to the original speed, forming a closed-loop control loop based on the burr thickness, so as to realize the online dynamic control of the burr size.

2. The method according to claim 1, characterized in that, In step one, after moving the cutting gun to a position 10-20mm away from the edge of the billet, press the edge positioning button, and the system will automatically identify and accurately position the cutting starting point.

3. The method according to claim 1, characterized in that, In step three, the cutting speed coefficient ranges from 1.8 to 3.

5.

4. The method according to claim 3, characterized in that, The cutting speed coefficient is set in segments according to the different cross-sectional specifications of the cast billet.

5. The method according to claim 1, characterized in that, In step three, the cutting oxygen pressure is adjusted to 0.8–1.1 MPa.

6. The method according to claim 1, characterized in that, In step three, the height of the cutting nozzle is adjusted so that the distance between the top of the blue flame core of the cutting flame and the top surface of the billet is maintained at 20-30mm.

7. The method according to claim 1, characterized in that, In step four, the trigger position for the automatic start of the flame cutting machine is above the initial position of the limit cutting roller conveyor.

8. The method according to claim 1, characterized in that, The first thickness threshold is 1 mm, and the second thickness threshold is 1.5 mm.

9. The method according to claim 1, characterized in that, Before step five, the process also includes: when the production process is interrupted or the drawing speed is reduced, resulting in a decrease in the surface temperature of the billet cutting area and an increase in the degree of oxidation, the cutting speed of the cutting torch is slowed down for areas with a higher degree of oxidation on the billet surface. After the cutting passes through the area, the cutting speed of the cutting torch is restored to the original speed.