Dynamic control method for continuous casting online surface quenching

Abstract

The invention relates to a continuous casting online surface quenching dynamic control method, which belongs to the technical field of metallurgy, and comprises the following steps: establishing a crystallizer heat transfer calculation model, a secondary cooling heat transfer calculation model, an air cooling heat transfer calculation model and a quenching heat transfer calculation model, calculating a casting blank temperature field according to real-time continuous casting production data, and correcting the model by combining with casting blank surface temperature measurement; determining the casting blank quenching time and the quenching roller speed according to the continuous casting ejection smooth condition; a quenching heat transfer model is adopted, and the quenching water amount of the quenching area outlet position reaching the quenching process required temperature and the quenching process required depth is calculated; and the casting blank is quenched through the quenching roller way speed and the quenching water amount which are calculated according to the real-time continuous casting working condition. The problem that quenching parameters cannot be dynamically adjusted according to continuous casting production working conditions in an existing casting blank surface quenching technology can be solved, and then the stability of the casting blank surface quenching technology is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy and relates to a dynamic control method for continuous casting online surface quenching. Background Art

[0002] Hot delivery and hot charging of continuous casting slabs effectively utilizes the thermal energy of high-temperature continuous casting slabs, offering advantages such as energy savings, improved yield rates, and shortened production cycles. This practice is being actively promoted by steel companies. However, compared to traditional cold charging processes, hot delivery and hot charging of continuous casting slabs is more susceptible to surface cracking during the heating furnace or subsequent rolling process. In-line surface quenching of slabs is the primary method for addressing these cracking issues during hot delivery. Extensive research has been conducted on the mechanisms and applications of in-line surface quenching of slabs.

[0003] Patent application "CN 103302262A" proposes a surface quenching process and apparatus for continuous casting slabs. Before the continuous casting slabs enter the heating furnace, their surface is rapidly cooled on the continuous casting and cutting conveyor rollers, rapidly reducing the temperature to below 600°C. Two upper and lower nozzle groups are arranged between adjacent conveyor rollers of the continuous casting and cutting conveyor rollers to effectively suppress the precipitation of coarse nitrides or carbonitrides of microalloying elements such as Nb, V, Ti, Al, and B at the austenite grain boundaries, thereby avoiding the occurrence of microcracks on the steel plate surface after hot rolling of the microalloyed steel.

[0004] Patent application "CN 10228968 A" discloses a method for directly delivering and loading high-strength low-alloy steel continuous casting billets. The method first uses a cooling medium to rapidly cool the continuous casting billets to below 500°C at a rate of 2 to 5°C / s on the continuous casting roller. After the continuous casting billets are rapidly cooled, they can be directly loaded into the heating furnace after a temperature recovery time of more than 5 minutes. This can avoid the occurrence of surface cracks on the steel plate when the high-strength low-alloy steel continuous casting billets are produced using ordinary hot delivery and hot loading processes.

[0005] Patent application "CN 105642853 A" provides a continuous casting billet cooling treatment method, including the following steps: the billet is separated from the liquid core or solid-liquid mixed state to achieve complete solidification; before the rapid cooling treatment, the billet surface temperature is above 900°C and the billet center temperature is above 1100°C; rapid cooling treatment, forming a low-temperature layer on the billet surface, and terminating the cooling treatment when the billet surface temperature drops to Ar1~(Ar1-300)°C; reheating treatment, terminating the reheating treatment when the billet surface temperature is greater than or equal to Ar1. The above method can increase the surface strength and plasticity, and avoid cracking of the bad material surface during subsequent transportation, lifting, stacking cooling and heating.

[0006] Patent application "CN 114672628 A" discloses a slab surface quenching system and process based on the end of a continuous casting machine. By arranging a spray device at the outlet of the fan-shaped section to implement a fully continuous quenching process on the slab surface, the temperature within the range of 0 to 10 mm below the upper and lower surfaces of the continuous casting slab after online ignition is rapidly reduced from above 930°C to below 600°C, achieving the purpose of dispersed precipitation of carbonitrides and transformation of austenite to ferrite or bainite, fundamentally improving the plasticity of the slab surface structure and eradicating the generation of hot-delivery cracks in micro-alloyed steel slabs.

[0007] The aforementioned patents all involve the application of surface quenching for ingots. They primarily define parameters such as the starting temperature, quenching water volume, cooling rate, hardenable layer depth, and quenching end temperature based on the surface quenching mechanism. However, based on actual production conditions in steel mills, it has been found that even after surface quenching ingots using the methods described in these patents, hot-feed cracking can still occur in the ingots during subsequent heating furnaces and hot rolling processes. The primary reason for these issues is that, influenced by the molten steel supply rhythm and temperature, the continuous casting casting temperature, casting speed, and cooling intensity typically vary. The cross-sectional temperature of the ingot also varies during quenching, resulting in varying requirements for surface quenching time and quenching water volume. Furthermore, the methods described in these patents cannot dynamically adjust the quenching water volume as continuous casting production conditions change, resulting in either too weak or too strong surface quenching, impacting the surface quenching effect. These issues are currently a key factor limiting the widespread application of in-line surface quenching for ingots. Summary of the Invention

[0008] In view of this, on the basis of fully understanding the surface quenching mechanism of the ingot and the changing laws of the production conditions of the continuous casting process, this application proposes a dynamic control method for online surface quenching of continuous casting, so as to dynamically adjust the surface quenching time and quenching water volume according to the changes in the continuous casting production conditions, so as to meet the demand for improvement of hot delivery cracks in the surface quenching of the ingot when the production conditions of the continuous casting process change.

[0009] In order to achieve the above object, the present invention provides the following technical solutions:

[0010] A dynamic control method for continuous casting online surface quenching, comprising the following steps:

[0011] S1: According to the continuous casting production conditions, the mold heat transfer calculation model, the secondary cooling heat transfer calculation model, the air cooling heat transfer calculation model and the quenching heat transfer calculation model are established;

[0012] S2: Based on the real-time continuous casting process parameters during the production process, the mold heat transfer calculation model and the secondary cooling heat transfer calculation model are used to calculate the temperature field of the cast strand in the mold and the secondary cooling zone, and the mold heat transfer calculation model, the secondary cooling heat transfer calculation model and the calculated temperature field are corrected based on the temperature measurement results of the cast strand surface at the continuous casting machine outlet to obtain the cross-sectional temperature distribution of the cast strand at the continuous casting machine outlet;

[0013] S3: Based on the cross-sectional temperature distribution of the cast billet at the continuous casting machine outlet and the time it takes for the cast billet to reach the entrance of the quenching zone after exiting the continuous casting machine, the air cooling heat transfer calculation model is used to calculate the temperature field of the cast billet from the continuous casting machine outlet to the entrance of the quenching zone, and the surface temperature measurement results of the cast billet at the entrance of the quenching zone are used to calibrate the air cooling heat transfer calculation model and the calculated temperature field to obtain the cross-sectional temperature distribution of the cast billet at the entrance of the quenching zone;

[0014] S4: Determine the quenching time that satisfies the billet forward running condition based on the billet cutting length, billet drawing speed, flame cutting time, deburring time and billet running time on the conveyor roller, and calculate the quenching roller speed based on the length of the quenching area;

[0015] S5: Calculating the quenching water volume that meets the quenching requirements based on the quenching heat transfer calculation model and the quenching process requirements of the steel grade according to the cross-sectional temperature distribution of the slab at the entrance of the quenching zone and the quenching time under the slab forward condition;

[0016] S6: dynamically adjusting the actual quenching roller speed and quenching water volume according to the calculated quenching roller speed and the quenching water volume that meets the quenching requirements, and the billet enters the quenching area for surface quenching;

[0017] S7: According to the surface temperature measurement result of the ingot at the exit of the quenching area, the quenching heat transfer calculation model is corrected, and the next ingot is quenched.

[0018] Furthermore, the continuous casting production conditions include the effective length of the crystallizer, the length of the secondary cooling zone, the length of the air cooling zone, the length of the quenching zone, the type of steel produced, the cross-section of the ingot, the temperature of the molten steel in the tundish, the billet drawing speed, the cooling water volume of the crystallizer, the temperature difference of the cooling water inlet and outlet of the crystallizer, the cooling water volume of the secondary cooling zone, the quenching cooling water volume, the roller speed after the ingot cutting, the roller speed of the quenching zone, the cooling water temperature of the secondary cooling zone, the quenching cooling water temperature and the ambient temperature.

[0019] Furthermore, the crystallizer heat transfer calculation model, secondary cooling heat transfer calculation model, air cooling heat transfer calculation model and quenching heat transfer calculation model are established using the explicit finite difference method or the implicit finite difference method, and the heat transfer coefficient in each model is obtained in combination with the continuous casting production conditions to calculate the temperature field of the ingot.

[0020] Furthermore, the real-time continuous casting process parameters include the type of steel produced, the cross-section of the ingot, the temperature of the molten steel in the tundish, the casting speed, the water volume in the crystallizer, the temperature difference between the inlet and outlet water of the crystallizer, the water volume in the secondary cooling zone, the secondary cooling water temperature and the ambient temperature. The data are directly read from the continuous casting machine PLC.

[0021] Furthermore, the surface temperature measurement results of the ingot are collected by temperature measuring equipment arranged on the upper and lower surfaces of the ingot. The upper surface temperature measuring equipment is directly above the ingot and perpendicular to the upper surface of the ingot, and the lower surface temperature measuring equipment is directly below the ingot and perpendicular to the lower surface of the ingot.

[0022] Furthermore, the correction of the crystallizer heat transfer calculation model, the secondary cooling heat transfer calculation model, the air cooling heat transfer calculation model and the quenching heat transfer calculation model is carried out by adjusting the heat transfer coefficient formula in the model so that the error between the billet surface temperature measurement results and the model calculation results is within ±0.3%.

[0023] Furthermore, the time it takes for the slab to reach the entrance of the quenching zone after exiting the continuous casting machine is calculated using the following formula:

[0024]

[0025] Among them, T1 represents the time it takes for the billet to reach the entrance of the quenching area after leaving the continuous casting machine; L1 represents the distance from the outlet of the continuous casting machine to the origin of the flame cutting; L2 represents the distance from the position sensor before the quenching area to the entrance of the quenching area; V1 represents the casting speed of the continuous casting machine; V2 represents the roller speed before quenching; T2 represents the time it takes for the billet to run from the origin of the flame cutting to the position sensor before the quenching area.

[0026] Furthermore, the time it takes for the billet to run from the flame cutting origin to the position sensor before the quenching area is obtained through the flame cutting start signal and the billet signal from the position sensor before the billet reaches the quenching area. The specific time is the difference between the times when the two signals are emitted.

[0027] Furthermore, the quenching water volume that meets the quenching requirements refers to the use of this water volume for surface quenching, which can reduce the temperature within a certain depth range on the surface of the ingot to the temperature required by the quenching process.

[0028] Furthermore, the quenching process requires a depth of 10 to 15 mm, and the quenching process requires a temperature that is the starting temperature for the transformation of austenite to pearlite in the produced steel.

[0029] The beneficial effect of the present invention lies in the fact that the dynamic control of online surface quenching performed by the method according to the present invention fully considers the changes in production conditions during the continuous casting process, such as the steel type, casting temperature, casting speed, and cooling water volume, and their impact on the cross-sectional temperature field of the slab at the start of quenching. This ensures that the quenching roller speed and quenching water volume for surface quenching of the slab are optimized to meet the current slab temperature conditions. Compared with the existing technology, this method can dynamically adjust the quenching time and quenching water volume according to changes in continuous casting production conditions, ensuring the application effect of slab surface quenching, thereby effectively solving the problem of hot delivery cracking of the continuous casting slab.

[0030] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0032] Figure 1 This is a flow chart of dynamic control of continuous casting online surface quenching according to an embodiment of the present invention;

[0033] Figure 2 The cross-sectional temperatures of the inlet and outlet of the quenching zone when the casting speed is 0.8 m / min in the embodiment of the present invention;

[0034] Figure 3 The cross-sectional temperatures of the inlet and outlet of the quenching zone when the casting speed is changed to 1.0 m / min and no quenching dynamic control is performed in the embodiment of the present invention;

[0035] Figure 4 The cross-sectional temperature of the inlet and outlet of the quenching zone when the quenching dynamic control is performed when the casting speed becomes 1.0m / min. DETAILED DESCRIPTION

[0036] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0037] It should be noted that the illustrations provided in the following embodiments are merely schematic illustrations of the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be changed arbitrarily, and the component layout may also be more complex.

[0038] In the following description, numerous details are discussed to provide a more thorough explanation of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the embodiments of the present invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring the embodiments of the present invention.

[0039] Example 1:

[0040] The present invention provides a dynamic control method for continuous casting online surface quenching, the method comprising the following steps:

[0041] S1: According to the continuous casting production conditions, establish the mold heat transfer calculation model, secondary cooling heat transfer calculation model, air cooling heat transfer calculation model, and quenching heat transfer calculation model;

[0042] S2: Calculating the temperature field of the slab in the slab and the secondary cooling zone using the mold heat transfer calculation model and the secondary cooling zone heat transfer calculation model based on real-time continuous casting process parameters during the production process. Correcting the mold heat transfer calculation model, the secondary cooling zone heat transfer calculation model, and the calculated temperature field using the surface temperature measurement results of the slab at the continuous casting machine outlet to obtain a cross-sectional temperature distribution of the slab at the continuous casting machine outlet.

[0043] S3: Based on the cross-sectional temperature distribution of the cast billet at the continuous casting machine outlet and the time it takes for the cast billet to reach the entrance of the quenching zone after exiting the continuous casting machine, the air cooling heat transfer calculation model is used to calculate the temperature field of the cast billet from the continuous casting machine outlet to the entrance of the quenching zone, and the surface temperature measurement results of the cast billet at the entrance of the quenching zone are used to calibrate the air cooling heat transfer calculation model and the calculated temperature field to obtain the cross-sectional temperature distribution of the cast billet at the entrance of the quenching zone;

[0044] S4: Determine the quenching time that satisfies the billet forward movement condition based on the billet cutting length, billet drawing speed, flame cutting time, deburring time, and billet running time on the conveyor roller, and calculate the quenching roller speed based on the length of the quenching area;

[0045] S5: Calculating the quenching water volume that meets the quenching requirements based on the quenching heat transfer calculation model and the quenching process requirements of the steel grade according to the cross-sectional temperature distribution of the slab at the entrance of the quenching zone and the quenching time under the slab forward condition;

[0046] S6: dynamically adjusting the actual quenching roller speed and quenching water volume according to the calculated quenching roller speed and the quenching water volume that meets the quenching requirements, and the billet enters the quenching area for surface quenching;

[0047] S7: According to the surface temperature measurement result of the ingot at the exit of the quenching area, the quenching heat transfer calculation model is corrected, and the next ingot is quenched.

[0048] In this embodiment, the continuous casting production conditions include the effective length of the crystallizer, the length of the secondary cooling zone, the length of the air cooling zone, the length of the quenching zone, the type of steel produced, the cross-section of the ingot, the temperature of the molten steel in the tundish, the billet drawing speed, the cooling water volume of the crystallizer, the temperature difference of the cooling water inlet and outlet of the crystallizer, the cooling water volume of the secondary cooling zone, the quenching cooling water volume, the roller speed after the ingot is cut, the roller speed in the quenching zone, the cooling water temperature of the secondary cooling zone, the quenching cooling water temperature, and the ambient temperature.

[0049] In this embodiment, the crystallizer heat transfer calculation model, the secondary cooling heat transfer calculation model, the air cooling heat transfer calculation model, and the quenching heat transfer calculation model are established using the explicit finite difference method or the implicit finite difference method, and the heat transfer coefficient in each model is obtained in combination with the continuous casting production conditions to calculate the temperature field of the ingot.

[0050] In this embodiment, the real-time continuous casting process parameters include the type of steel produced, the cross-section of the ingot, the temperature of the molten steel in the tundish, the billet drawing speed, the water volume in the crystallizer, the temperature difference between the inlet and outlet water of the crystallizer, the water volume in the secondary cooling zone, the secondary cooling water temperature, and the ambient temperature. The data are read directly from the PLC of the continuous casting machine, thereby ensuring the real-time nature of the production data and the correspondence between the production data and the ingot.

[0051] In this embodiment, the surface temperature measurement results of the ingot are obtained by using a fixed high-temperature infrared thermometer or an infrared thermal imager as the temperature measuring equipment. The measurement positions are on the upper and lower surfaces of the ingot. The temperature measuring equipment on the upper surface of the ingot is directly above the ingot and perpendicular to the upper surface of the ingot. The temperature measuring equipment on the lower surface of the ingot is directly below the ingot and perpendicular to the lower surface of the ingot, thereby reducing accidental errors in the temperature measurement results.

[0052] In this embodiment, in order to ensure the accuracy of the temperature measurement results, the temperature curve is measured once every 60 seconds during the temperature measurement process, and the temperature measurement result takes the average value of all temperature maxima in the temperature curve, thereby reducing the influence of slag and iron oxide scale on the surface of the ingot on the temperature measurement accuracy.

[0053] In this embodiment, the correction of the crystallizer heat transfer calculation model, the secondary cooling heat transfer calculation model, the air cooling heat transfer calculation model, and the quenching heat transfer calculation model is carried out by adjusting the heat transfer coefficient formula in the model, so that the error between the surface temperature measurement results of the ingot and the model calculation results is within ±0.3%, so that each model has a higher accuracy.

[0054] In this embodiment, the time it takes for the slab to reach the entrance of the quenching zone after exiting the continuous casting machine is calculated using the following formula:

[0055]

[0056] Wherein, T1 is the time from when the billet leaves the continuous casting machine and reaches the entrance of the quenching area, s; L1 is the distance from the exit of the continuous casting machine to the origin of the flame cutting, m; L2 is the distance from the position sensor before the quenching area to the entrance of the quenching area, m; V1 is the casting speed of the continuous casting machine, m / s; V2 is the roller speed before quenching, m / s; T2 is the time it takes for the billet to travel from the origin of the flame cutting to the position sensor before the quenching area, s.

[0057] In this embodiment, the time it takes for the billet to run from the flame cutting origin to the position sensor before the quenching area is obtained through the flame cutting start signal and the billet signal from the position sensor before the billet reaches the quenching area. The specific time is the difference between the times when the two signals are emitted.

[0058] In this embodiment, the quenching water volume that meets the quenching requirements refers to the use of this water volume for surface quenching, which can reduce the temperature within a certain depth range on the surface of the ingot to the temperature required by the quenching process.

[0059] In this embodiment, the quenching process requires a depth of 10 to 15 mm, and the quenching process requires a temperature that is the starting temperature for the transformation of austenite to pearlite of the produced steel, which can be obtained through thermal expansion test.

[0060] Example 2:

[0061] The continuous casting machine produces Q355B steel, with a cross-sectional size of 280mm×1600mm, an effective length of 0.80m for the crystallizer, a length of 35.4m for the secondary cooling zone, a length of 53.4m for the air cooling zone, a distance of 6.8m from the continuous casting machine outlet to the flame cutting origin, a distance of 1.8m from the position sensor in front of the quenching zone to the entrance of the quenching zone, a length of 6.0m for the quenching zone, and a length of 5.6m for the produced billet. During the continuous casting process, the molten steel temperature in the tundish was 1540°C, the billet drawing speed was 0.8m / min, and the cooling water volume of the crystallizer was 408m 3 / h, the temperature difference between the inlet and outlet water of the crystallizer is 6.5℃, and the cooling water volume of the secondary cooling zone is 154.4m 3 / h, the initial quenching cooling water volume is 80m3 / h, the roller speed after slab cutting was 15m / min, the roller speed in the initial quenching zone was 6m / min, and the roller speed before quenching was 9.0m / min. The cooling water temperature in the secondary cooling zone was 38°C, and the ambient temperature was 30°C. A high-temperature infrared thermometer was used to measure the temperatures at the continuous casting machine outlet, the quenching zone entrance, and the quenching zone exit. During the continuous casting process, the proposed method for dynamic control of online surface quenching in continuous casting was used to dynamically control the surface quenching of the slab.

[0062] Based on the above continuous casting production conditions, the finite difference method was used to establish heat transfer calculation models for the mold, secondary cooling, air cooling, and quenching. The mold and secondary cooling heat transfer models were used to calculate the temperature field during the continuous casting process, combined with real-time continuous casting process parameters. Temperature measurements at the mold outlet were analyzed using a high-temperature infrared thermometer. 120 temperature readings were collected over 60 seconds on the billet surface. The temperature fluctuated over time, and the average of all maximum values ​​on the temperature curve was 826.2°C. This average was used as the billet top surface temperature at the continuous casting machine outlet. The solidification heat transfer model for the continuous casting process was calibrated based on this temperature, resulting in a calculated temperature of 824.0°C with an error of 0.27%, meeting the required model accuracy. Based on the calibrated billet temperature field, the cross-sectional temperature field at the continuous casting machine outlet was determined. Based on the continuous casting process, the flame cutting start signal was issued at 16:12:12, and the incoming signal from the position sensor before the slab reached the quenching zone was issued at 16:24:27. Based on these parameters, the time it took for the slab to reach the quenching zone entrance after exiting the continuous casting machine was calculated to be 1257 seconds. Based on the cross-sectional temperature field of the slab at the continuous casting machine exit and the time it took for the slab to reach the quenching zone entrance after exiting the continuous casting machine, an air cooling heat transfer model was used to calculate the temperature field of the slab from the continuous casting machine exit to the quenching zone entrance. Analysis of the high-temperature infrared thermometer at the quenching zone entrance revealed a temperature of 761.7°C on the top surface of the slab at the quenching zone entrance. This temperature was used to calibrate the air cooling heat transfer model, resulting in a calculated temperature of 762.0°C with an error of 0.04%. The corrected slab temperature field was used to determine the cross-sectional temperature field at the quenching zone entrance.

[0063] According to the continuous casting billet situation, the quenching time that meets the billet forward condition is determined to be 107s, and the quenching roller speed calculated in combination with the quenching zone length is 3.36m / min. The quenching process requirement temperature of the production steel grade Q355B steel is the starting temperature of the transformation from austenite to pearlite. The static CCT curve test result of the steel is 620℃, and the quenching process requires a depth of 12mm. According to the cross-sectional temperature field of the billet at the entrance of the quenching zone and the quenching time, the quenching heat transfer calculation model is used to calculate the quenching water volume and temperature field required to reduce the temperature of the billet surface to the temperature required by the quenching process within the depth range required by the quenching process, and the quenching water volume is 142.6m 3 / h, quenching depth is 12.1mm. Figure 2 The figure shows the cross-sectional temperature of the ingot before and after quenching under this production condition. The quenching roller speed is adjusted to 3.36m / min and the quenching water volume is 142.6m 3 / h, the ingot enters the quenching area for surface quenching. After quenching, the ingot is hot-transferred and hot-loaded and directly sent to the heating furnace for rolling after heating. The final product quality is good.

[0064] During the continuous casting process, the production rhythm changes and the casting speed increases to 1.0m / min. If the dynamic control method is not adopted, the quenching water volume is still 142.6m 3 / h, the cross-section temperature of the ingot before and after quenching is as follows Figure 3 As shown. At this time, the slab quenching depth is 7.5mm, which cannot meet the slab surface quenching requirements. Quenching under this water volume will result in insufficient quenching effect after slab surface quenching, and there is still the possibility of hot delivery cracks in the subsequent heating furnace and hot rolling process. Using the continuous casting online surface quenching dynamic control method proposed in this application, the quenching time is 94s, the quenching roller speed is 3.83m / min, and the quenching water volume is 181.4m 3 / h, the cross-section temperature of the ingot before and after quenching is as follows Figure 4 At this time, the slab quenching depth is 12.2mm, which can meet the surface quenching requirements of the slab. After quenching, the slab is hot-sent and hot-loaded, and directly sent to the heating furnace for rolling after heating. The final product quality is good.

[0065] In summary, the online surface quenching dynamic control method proposed in this application can dynamically adjust quenching parameters according to changes in continuous casting production conditions, ensuring the stability of the surface quenching effect of the ingot, thereby meeting the quenching requirements of continuous casting steel ingots. After adopting this method, the overall crack rate of hot-delivered continuous casting ingots was reduced by approximately 12%, and the hot-delivery and hot-loading rate of continuous casting was increased by approximately 20%.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A dynamic control method for continuous casting online surface quenching, characterized by: The following steps are involved: S1: According to the continuous casting production conditions, the mold heat transfer calculation model, the secondary cooling heat transfer calculation model, the air cooling heat transfer calculation model and the quenching heat transfer calculation model are established; S2: Based on the real-time continuous casting process parameters during the production process, the mold heat transfer calculation model and the secondary cooling heat transfer calculation model are used to calculate the temperature field of the cast strand in the mold and the secondary cooling zone, and the mold heat transfer calculation model, the secondary cooling heat transfer calculation model and the calculated temperature field are corrected based on the temperature measurement results of the cast strand surface at the continuous casting machine outlet to obtain the cross-sectional temperature distribution of the cast strand at the continuous casting machine outlet; S3: Based on the cross-sectional temperature distribution of the cast billet at the continuous casting machine outlet and the time it takes for the cast billet to reach the entrance of the quenching zone after exiting the continuous casting machine, the air cooling heat transfer calculation model is used to calculate the temperature field of the cast billet from the continuous casting machine outlet to the entrance of the quenching zone, and the surface temperature measurement results of the cast billet at the entrance of the quenching zone are used to calibrate the air cooling heat transfer calculation model and the calculated temperature field to obtain the cross-sectional temperature distribution of the cast billet at the entrance of the quenching zone; S4: Determine the quenching time that satisfies the billet forward running condition based on the billet cutting length, billet drawing speed, flame cutting time, deburring time and billet running time on the conveyor roller, and calculate the quenching roller speed based on the length of the quenching area; S5: Calculating the quenching water volume that meets the quenching requirements based on the quenching heat transfer calculation model and the quenching process requirements of the steel grade according to the cross-sectional temperature distribution of the slab at the entrance of the quenching zone and the quenching time under the slab forward condition; S6: dynamically adjusting the actual quenching roller speed and quenching water volume according to the calculated quenching roller speed and the quenching water volume that meets the quenching requirements, and the billet enters the quenching area for surface quenching; S7: According to the surface temperature measurement result of the ingot at the exit of the quenching area, the quenching heat transfer calculation model is corrected, and the next ingot is quenched.

2. The dynamic control method for surface quenching during continuous casting according to claim 1, characterized in that: Continuous casting production conditions include the effective length of the crystallizer, the length of the secondary cooling zone, the length of the air cooling zone, the length of the quenching zone, the type of steel produced, the cross-section of the ingot, the temperature of the molten steel in the tundish, the billet drawing speed, the amount of cooling water in the crystallizer, the temperature difference between the cooling water inlet and outlet of the crystallizer, the amount of cooling water in the secondary cooling zone, the amount of cooling water for quenching, the roller speed after ingot cutting, the roller speed in the quenching zone, the cooling water temperature in the secondary cooling zone, the cooling water temperature for quenching and the ambient temperature.

3. The dynamic control method for surface quenching during continuous casting according to claim 1, characterized in that: The mold heat transfer calculation model, secondary cooling heat transfer calculation model, air cooling heat transfer calculation model and quenching heat transfer calculation model are established using the explicit finite difference method or the implicit finite difference method, and the heat transfer coefficient in each model is obtained in combination with the continuous casting production conditions to calculate the temperature field of the casting billet.

4. The dynamic control method for surface quenching during continuous casting according to claim 1, characterized in that: Real-time continuous casting process parameters include the type of steel produced, the cross-section of the ingot, the temperature of the molten steel in the tundish, the casting speed, the water volume in the crystallizer, the temperature difference between the inlet and outlet water of the crystallizer, the water volume in the secondary cooling zone, the secondary cooling water temperature and the ambient temperature. The data are read directly from the continuous casting machine PLC.

5. The dynamic control method for surface quenching during continuous casting according to claim 1, characterized in that: The surface temperature measurement results of the ingot are collected by temperature measuring equipment installed on the upper and lower surfaces of the ingot. The upper surface temperature measuring equipment is directly above the ingot and perpendicular to the upper surface of the ingot, and the lower surface temperature measuring equipment is directly below the ingot and perpendicular to the lower surface of the ingot.

6. The dynamic control method for surface quenching during continuous casting according to claim 1, characterized in that: The correction of the mold heat transfer calculation model, the secondary cooling heat transfer calculation model, the air cooling heat transfer calculation model and the quenching heat transfer calculation model is carried out by adjusting the heat transfer coefficient formula in the model so that the error between the billet surface temperature measurement result and the model calculation result is within ±0.3%.

7. The dynamic control method for surface quenching during continuous casting according to claim 1, characterized in that: The time it takes for the slab to reach the entrance of the quenching area after leaving the continuous casting machine is calculated using the following formula: Among them, T1 represents the time it takes for the billet to reach the entrance of the quenching area after leaving the continuous casting machine; L1 represents the distance from the outlet of the continuous casting machine to the origin of the flame cutting; L2 represents the distance from the position sensor before the quenching area to the entrance of the quenching area; V1 represents the casting speed of the continuous casting machine; V2 represents the roller speed before quenching; T2 represents the time it takes for the billet to run from the origin of the flame cutting to the position sensor before the quenching area.

8. The dynamic control method for surface quenching during continuous casting according to claim 1, characterized in that: The time it takes for the billet to move from the flame cutting origin to the position sensor before the quenching area is obtained through the flame cutting start signal and the billet signal from the position sensor before the billet reaches the quenching area. The specific time is the difference between the two signal emission times.

9. The dynamic control method for surface quenching during continuous casting according to claim 1, characterized in that: The amount of quenching water that meets the quenching requirements means that the use of this amount of water for surface quenching can reduce the temperature within a certain depth range on the surface of the ingot to the temperature required by the quenching process.

10. The dynamic control method for surface quenching during continuous casting according to claim 1, characterized in that: The quenching process requires a depth of 10 to 15 mm, and the quenching process requires a temperature that is the starting temperature for the transformation of austenite to pearlite in the produced steel.

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