Method for starting casting of round bloom with extra large cross section

Abstract

This invention discloses a method for continuous casting of extra-large cross-section round billets, applicable to continuous casting of round billets with diameters of Φ600~Φ1200mm. The steps include detecting and determining the compliance of the dummy bar deformation, sealing the dummy bar, filling with cold material, and controlling the start-up of casting. The key to this method for continuous casting of extra-large cross-section round billets lies in optimizing the cold material filling method and enhancing the cooling intensity of the part of the dummy bar in contact with the molten steel. This effectively improves the stability and success rate of casting, ensuring a stable 100% success rate, thereby improving economic efficiency and reducing production costs and the workload of workers.

Description

Technical Field

[0001] This invention belongs to the field of continuous casting technology in iron and steel metallurgy. Specifically, this invention relates to a method for continuous casting of extra-large cross-section round billets. Background Technology

[0002] With the rapid development of industries such as wind power, petroleum, and marine engineering, the market demand for large-section, high-quality continuously cast round billets is increasing, especially for ultra-large continuously cast round billets with a diameter of Φ600mm or more. When continuously casting ultra-large cross-section round billets, compared to traditional small-section billets, the weight and specifications of the dummy bar used have changed significantly. The dummy bar is approximately 15m long, with a maximum weight of 20t. The clamping force required during production is much greater, withstanding a maximum high pressure exceeding 400t. If, during production, there are issues such as inaccurate encoder counting, roller slippage, or abnormal malfunctions in the straightening machine, causing a deviation between the programmed position and the actual position of the dummy bar (with a maximum deviation of 800~1000mm), the dummy bar may be pressed during the transition from high to low pressure in the straightening machine. Once the dummy bar is subjected to the high pressure of the straightening machine, it will deform to varying degrees, a phenomenon known as dummy bar bulging. When the deformation exceeds a certain range, difficulty in detaching the dummy bar can occur, potentially leading to serious production accidents such as steel leakage. However, large-sized dummy bars are very expensive, ranging from tens of thousands to hundreds of thousands of yuan. If they are directly replaced after deformation, it will put huge cost pressure on steel companies and reduce economic benefits. Therefore, it is necessary to solve the problem of continuing production after the dummy bar is deformed. For minor deformation, the deformed part can be manually ground off. However, for larger deformation, the dummy bar insertion method can be improved and the casting process parameters can be optimized to stabilize and improve the success rate of dummy bar removal and casting success rate.

[0003] The insertion of the dummy ingot is a crucial step in the pre-casting preparation, and its operational standards and the operator's proficiency largely determine whether the continuous casting can proceed smoothly. For continuous casting machines with extra-large cross-section round billets where the dummy ingot rod is deformed, the larger the cross-section, the higher the risk of casting failure and the higher the accident costs. Incorrect insertion of the dummy ingot or the addition of cold material that is not suitable for the steel grade often increases the risk of production accidents, which has a significant impact on both equipment and product quality.

[0004] In addition, the start-up process and related parameters are also key factors in determining the success of continuous casting. If the start-up calming time, start-up casting speed and other parameters do not meet the requirements, or if the start-up process does not meet the superheat of the molten steel in the ladle, it will lead to major production accidents such as nozzle overflow and steel leakage, which will seriously restrict the company's production stability and competitiveness.

[0005] Chinese Patent CN218361968U discloses a sealing ingot device for ultra-large continuous casting round billets, which achieves safe and stable sealing ingot operation before casting of large-sized continuous casting round billets. It lists the sealing ingot methods for producing Φ1000mm and Φ1200mm cross-section continuous casting round billets, but does not describe the sealing ingot methods for other cross-section continuous casting round billets, nor does it describe the casting process and casting method, and does not describe the method for dealing with the deformation problem of the ingot rod of ultra-large cross-section continuous casting round billets.

[0006] This paper provides a method for continuous casting of extra-large cross-section round billets, particularly focusing on how to improve the success rate of casting, increase economic benefits, and reduce production costs and labor intensity. Summary of the Invention

[0007] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention provides a method for continuous casting of extra-large cross-section round billets, with the purpose of improving the success rate of initial casting.

[0008] To achieve the above objectives, the technical solution adopted by this invention is as follows: a continuous casting method for extra-large cross-section round billets, applicable to the continuous casting of round billets with a cross-section of Φ600~Φ1200mm, comprising the following steps: S1. Deformation detection and compliance judgment of the dummy bar: Detect the actual measured height of the dummy bar, calculate the deformation amount, deformation amount = actual measured height of the dummy bar - original height of the dummy bar, and determine whether the deformation amount meets the preset range; if it does not meet the preset range, repair or replace the dummy bar. S2. Seal the ingot rod: After the ingot rod is sent to the fixed position at the bottom of the crystallizer, seal the gap between the ingot rod and the crystallizer with sealing material; S3. Cold material filling: Iron particles, a cooling frame and a first cold material are laid on the ingot head of the ingot rod, and a second cold material is installed on the cooling frame; S4. Initial Casting Control: Determine the emergence time based on the cross-section of the billet, and control the initial casting speed and casting speed before exiting the crystallizer in combination with the superheat of the molten steel. Adjust the casting speed after the ingot head has completely exited the crystallizer.

[0009] In step S1, the initial height of the guide rod is 165±5mm; the preset range is: When the cross-section of the round billet is Φ600mm, the deformation amount is ≤40mm; When the cross-section of the round billet is Φ700mm or Φ800mm, the deformation amount is ≤45mm; When the cross-section of the round billet is Φ900mm, the deformation amount is ≤50mm; When the cross-section of the round billet is Φ1000mm, the deformation amount is ≤60mm; When the cross-section of the round billet is Φ1100mm or Φ1200mm, the deformation amount is ≤65mm.

[0010] In step S2, the sealing material is high-temperature resistant putty, and the composition of the high-temperature resistant putty meets the following requirements: w(Al2O3) ≥ 28%, w(SiO2) ≤ 38%, w(C) ≥ 8%, and the bulk density of the high-temperature resistant putty under the condition of 110℃×24h is ≥ 1.30g / cm³. 3 ; In step S2, the application width L of the sealing material satisfies 1.5cm≤L≤3.5cm.

[0011] In step S2, the position s of the ingot head of the ingot rod from the top opening of the crystallizer satisfies: When the cross-section of the round billet is Φ600~Φ700mm, s=390mm; When the cross-section of the round billet is Φ800~Φ900mm, s=370mm; When the cross-section of the round billet is Φ1000~Φ1200mm, s=350mm.

[0012] In step S3, the diameter of the second cold material is Φ5~9mm and the height is 180~250mm; the diameter of the first cold material is Φ6~10mm and the height is 140~220mm; and the thickness of the iron particle layer is 0.5~1mm.

[0013] The cooling frame includes an outer ring, a middle ring, an inner ring, and connecting ribs. The outer ring, middle ring, and inner ring are circular ring structures and are coaxially arranged. The connecting ribs are connected to the outer ring, middle ring, and / or inner ring and are perpendicular to the axes of the outer ring, middle ring, and inner ring. In step S3, the quantities of the second cold material and the first cold material are satisfied as follows: When the cross-section of the round billet is Φ600mm, the amount of the second cold material on the outer ring is 40~45, the amount of the second cold material on the middle ring is 30~35, and the amount of the second cold material on the connecting rib is 15~20. In the large flat layer area of ​​the dummy bar head, the quantity of the first cold material is 10~15; In the beveled area of ​​the derrick head, the amount of the first cold material is 5 to 10.

[0014] In step S3, the quantities of the second cold material and the first cold material are satisfied as follows: When the cross-section of the round billet is Φ700mm, the amount of the second cold material on the outer ring is 50~55, the amount of the second cold material on the middle ring is 30~35, the amount of the second cold material on the inner ring is 12~15, and the amount of the second cold material on the connecting rib is 15~20. In the large flat layer area of ​​the dummy bar head, the quantity of the first cold material is 15~20; In the beveled area of ​​the derrick head, the amount of the first cold material is 5 to 10.

[0015] In step S3, the quantities of the second cold material and the first cold material are satisfied as follows: When the cross-section of the round billet is Φ800mm, the amount of the second cold material on the outer ring is 50~55, the amount of the second cold material on the middle ring is 35~40, the amount of the second cold material on the inner ring is 12~15, and the amount of the second cold material on the connecting rib is 30~40. In the large flat layer area of ​​the dummy head, the quantity of the first cold material is 20~25; In the beveled area of ​​the derrick head, the amount of the first cold material is 5 to 10.

[0016] In step S3, the quantities of the second cold material and the first cold material are satisfied as follows: When the cross-section of the round billet is Φ900mm, the amount of the second cold material on the outer ring is 60~65, the amount of the second cold material on the middle ring is 40~45, the amount of the second cold material on the inner ring is 12~15, and the amount of the second cold material on the connecting rib is 30~40. In the large flat area of ​​the dummy bar head, the quantity of the first cold material is 25~30; In the beveled area of ​​the derrick head, the amount of the first cold material is 10~15.

[0017] In step S3, the quantities of the second cold material and the first cold material are satisfied as follows: When the cross-section of the round billet is Φ1000mm, the amount of the second cold material on the outer ring is 70~75, the amount of the second cold material on the middle ring is 45~50, the amount of the second cold material on the inner ring is 15~20, and the amount of the second cold material on the connecting rib is 60~70. In the large flat area of ​​the dummy bar head, the quantity of the first cold material is 40~50; In the beveled area of ​​the derrick head, the amount of the first cold material is 10~20.

[0018] In step S3, the quantities of the second cold material and the first cold material are satisfied as follows: When the cross-section of the round billet is Φ1100mm, the amount of the second cold material on the outer ring is 75~80, the amount of the second cold material on the middle ring is 55~60, the amount of the second cold material on the inner ring is 15~20, and the amount of the second cold material on the connecting rib is 80~90. In the large flat layer area of ​​the dummy bar head, the quantity of the first cold material is 55~60; In the beveled area of ​​the derrick head, the amount of the first cold material is 10~20.

[0019] In step S3, the quantities of the second cold material and the first cold material are satisfied as follows: When the cross-section of the round billet is Φ1200mm, the amount of the second cold material on the outer ring is 80~85, the amount of the second cold material on the middle ring is 60~65, the amount of the second cold material on the inner ring is 15~20, and the amount of the second cold material on the connecting rib is 95~100. In the large flat layer area of ​​the dummy bar head, the quantity of the first cold material is 45~50; In the beveled area of ​​the derrick head, the amount of the first cold material is 15~20.

[0020] In step S3, the filling method of the first cold material in the large flat layer area of ​​the ingot head satisfies the following: When the cross-section of the round billet is Φ600~Φ800mm, the first cold material is filled by laying it flat. When the cross-section of the round billet is Φ900~Φ1200mm, the first cold material is filled by oblique insertion.

[0021] In step S4, the formula for calculating the emergence time is: emergence time = (D / 100-6)×k+1, where D is the cross-section of the round blank, and k is a coefficient and 0.5≤k≤0.7.

[0022] In step S4, the control method for the initial casting speed and the casting speed before exiting the crystallizer is as follows: When the superheat of molten steel is >60℃, the initial casting speed is V1, and the casting speed before exiting the crystallizer is V2, and V1≤V2; When the superheat of molten steel is 30℃~60℃, the initial casting speed is V3, and the casting speed before exiting the crystallizer is V4, with V3≤V4; When the superheat of molten steel is <30℃, the initial casting speed is V5, and the casting speed before exiting the crystallizer is V6, with V5≤V6.

[0023] In step S4, the vibration parameters of the crystallizer are: vibration frequency of 70~120 times / minute and amplitude of 2.0~3.5mm.

[0024] In step S4, the water volume Q in the crystallizer satisfies: Q = 4.25 × D + 2360, where D is the cross-section of the round billet.

[0025] In step S4, the addition parameters of the protective slag in the crystallizer are as follows: it is added after the molten steel has completely flooded the cooling frame, the initial addition amount is 0.4~0.8 kg / t, and the thickness of the protective slag liquid layer in the crystallizer is maintained at 4~8 mm.

[0026] When the derrick head deforms, the first cold material is placed in the gap formed between the protruding structure in the deformation area of ​​the derrick head and the cooling frame.

[0027] The extra-large cross-section round billet continuous casting method of the present invention optimizes the filling method of cold material and enhances the cooling intensity of the part in contact with molten steel at the deformation position of the dummy bar, effectively improving the stability and success rate of casting. It can ensure that the success rate of casting is stably controlled at 100%, improve economic efficiency, and reduce production costs and labor intensity. Attached Figure Description

[0028] This manual includes the following figures, which illustrate the following: Figure 1 This is a flowchart of the continuous casting method for extra-large cross-section round billets of the present invention; Figure 2 This is a schematic diagram of the deformation of the derrick; Figure 3 This is a schematic diagram of molten steel filling when the dummy bar is not deformed; Figure 4 This is a schematic diagram of molten steel filling after the ingot rod is deformed; Figure 5 This is a schematic diagram of the cooling frame structure; Figure 6 This is a diagram illustrating the usage status of the cooling frame; Figure 7 This is a schematic diagram of the first cold material being inserted at an angle; Figure 8 It is a graph showing the casting speed control during the initial pouring stage; The markings in the diagram are as follows: 1. Outer ring; 2. Middle ring; 3. Inner ring; 4. Connecting rib; 5. Large flat area; 6. Beveled area; 7. Groove; 8. Digging head; 9. Cooling frame; 10. Cold material; 11. Molten steel; 12. Protruding structure; 13. First cold material; 14. Second cold material. Detailed Implementation

[0029] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention, and to facilitate its implementation.

[0030] It should be noted that in the following embodiments, the terms "first" and "second" do not represent an absolute distinction in structure and / or function, nor do they represent the order of execution, but are merely for the convenience of description.

[0031] like Figure 1 As shown, this invention provides a method for continuous casting of extra-large cross-section round billets, applicable to the continuous casting of round billets with a cross-section of Φ600~Φ1200mm, comprising the following steps: S1. Deformation detection and compliance judgment of the dummy bar: Detect the actual measured height of the dummy bar, calculate the deformation amount, deformation amount = actual measured height of the dummy bar - original height of the dummy bar, and determine whether the deformation amount meets the preset range; if it does not meet the preset range, repair or replace the dummy bar. S2. Insertion rod sealing: After the insertion rod is sent to the fixed position at the bottom of the crystallizer, the gap between the insertion rod and the crystallizer is sealed with sealing material. S3, Cold material filling: Iron particles, cooling frame and first cold material 13 are laid on the ingot head of the ingot rod, and second cold material 14 is installed on the cooling frame; S4. Initial Casting Control: Determine the emergence time based on the cross-section of the billet, and control the initial casting speed and casting speed before exiting the crystallizer in combination with the superheat of the molten steel. Adjust the casting speed after the ingot head has completely exited the crystallizer.

[0032] Specifically, this invention employs a method for the initial casting of extra-large cross-section round billets in continuous casting based on the deformation of the dummy bar. This method, while maintaining the existing dummy bar deformation, utilizes an improved dummy bar insertion method and optimized initial casting process parameters to steadily improve the success rate of dummy bar removal and initial casting, ensuring the stability of continuous casting production. This method significantly reduces the production cost of frequent dummy bar replacements, effectively avoids safety risks during initial casting, and reduces production accidents such as failed dummy bar removal, billet stagnation, and leaks during initial casting, achieving a simultaneous improvement in production efficiency and profitability. The specific innovations are as follows: (1) By improving the method of inserting the dummy bar to produce continuous casting round billets with cross sections of Φ600~Φ1200mm under the condition of dummy bar deformation, optimizing the filling method of cold material, enhancing the cooling intensity of the part of the dummy bar in contact with the molten steel, the stability of casting and the success rate of casting are effectively improved. (2) Based on the deformation of the dummy bar, the start-up control of the extra-large cross section continuous casting round billet is reasonably set. The start-up calming time, start-up casting speed and other parameters are set to significantly reduce the occurrence of production accidents such as start-up flow storage, overflow and leakage. The start-up success rate is kept stable at 100%.

[0033] In step S1 above, the initial height H of the derrick is 165±5mm; the preset range is: When the cross-section of the round billet is Φ600mm, the deformation is ≤40mm; When the cross-section of the round billet is Φ700mm or Φ800mm, the deformation is ≤45mm; When the cross-section of the round billet is Φ900mm, the deformation is ≤50mm; When the cross-section of the round billet is Φ1000mm, the deformation is ≤60mm; When the cross-section of the round billet is Φ1100mm or Φ1200mm, the deformation is ≤65mm.

[0034] If the deformation of the dummy bar is found to be beyond the range, the dummy bar needs to be repaired or replaced. Otherwise, the solidification of molten steel will cause adhesion at the deformation point, leading to the risk of failure to detach the dummy bar or leakage during casting.

[0035] In step S2 above, the dummy bar is moved to the fixed position at the bottom of the crystallizer. A high-temperature resistant sealing material is used to seal the gap between the dummy bar and the crystallizer to prevent molten steel from overflowing downwards during the initial pouring process. The sealing material is high-temperature resistant putty, and its composition meets the following requirements: w(Al2O3) ≥ 28%, w(SiO2) ≤ 38%, w(C) ≥ 8%, and the bulk density of the high-temperature resistant putty at 110℃ for 24h is ≥ 1.30 g / cm³. 3 ; In step S2 above, the sealing material seals the gap between the copper tube of the crystallizer and the ingot rod. The application width L of the sealing material satisfies 1.5cm≤L≤3.5cm. If L is too small, the seal will not be tight, and molten steel will leak through the gap, causing a steel leakage accident. If L is too large, the sealing material will hinder the cooling effect of the ingot head on the molten steel, and will not play a cooling role around the ingot head and its edges.

[0036] In step S2 above, when the billet is in "holding" mode, the distance s between the ingot head of the ingot dummy bar and the upper opening of the crystallizer must meet the following requirements: When the cross-section of the round billet is Φ600~Φ700mm, s=390mm; When the cross-section of the round billet is Φ800~Φ900mm, s=370mm; When the cross-section of the round billet is Φ1000~Φ1200mm, s=350mm.

[0037] The above settings have the following advantages: 1. The requirement for matching casting speed. Smaller cross-sections require faster initial casting speeds than larger cross-sections. During the initial casting stage, the dummy bar needs to move synchronously with the nascent billet shell. If the speed (s) is too small, the high-speed cast billet is prone to deformation and leakage after leaving the crystallizer due to insufficient shell strength. Increasing s effectively prolongs the solidification time of the billet in the crystallizer and foot roll area, ensuring the billet shell thickness is sufficient to withstand subsequent straightening forces and preventing shell tearing caused by high-speed casting. Conversely, the same principle applies to larger cross-sections.

[0038] 2. The need for stable liquid level control. During initial casting, the molten steel level in the crystallizer needs to be maintained within a certain range for stable casting. Small-section crystallizers have a small cross-sectional area, making them more sensitive to level fluctuations after molten steel injection. If the level (s) is too low, the distance between the dummy bar head and the nozzle will be too close, interfering with the flow trajectory of the molten steel and leading to localized excessively high or low levels, causing defects such as slag inclusions and slag entrapment. Increasing s allows the molten steel to form a more stable flow and temperature field within the crystallizer, which is particularly suitable for the narrow gap characteristics of small-section crystallizers, ensuring the uniformity of the initial solidified shell. Conversely, the same applies to large-section crystallizers. Simultaneously, considering the emergence time and initial casting speed of different cross-sections, to ensure that the molten steel exits the crystallizer with a sufficiently strong shell, the range of s is controlled between 350 and 390 mm.

[0039] The cooling frame is made of steel, such as Figures 5 to 7 As shown, the cooling frame includes an outer ring 1, a middle ring 2, an inner ring 3, and a connecting rib 4. The outer ring 1, middle ring 2, and inner ring 3 are circular ring structures and are coaxially arranged. The diameter of the outer ring 1 is larger than the diameter of the middle ring 2, and the diameter of the middle ring 2 is larger than the diameter of the inner ring 3. The connecting rib 4 is connected to the outer ring 1, middle ring 2, and / or inner ring 3 and is perpendicular to the axis of the outer ring 1, middle ring 2, and inner ring 3. Multiple connecting ribs 4 are provided, and the connecting ribs 4 are distributed in a crisscross pattern, so that multiple grids are formed in the ring-enclosed area of ​​the cooling frame. Each grid is formed by adjacent connecting ribs 4 and the corresponding outer ring 1, middle ring 2 or inner ring 3. The grid is used to insert the second cold material 14. Multiple second cold materials 14 are provided. The second cold materials 14 are respectively hung on the outer ring 1, middle ring 2, inner ring 3 and connecting ribs 4, so as to achieve the cooling effect.

[0040] In this embodiment of the invention, the second cold material 14 has a U-shaped structure and is a metal part used to enhance the cooling effect of the cooling frame area. The U-shaped structure facilitates installation and mounting on the cooling frame. The first cold material 13 is a straight-thread coarse cold material, which is made of threaded steel. The first cold material 13 is used to place in the deformation area of ​​the ingot head.

[0041] In step S3 above, the diameter of the second cold material 14 is Φ5~9mm and the height is 180~250mm; the diameter of the first cold material 13 is Φ6~10mm and the height is 140~220mm; iron particles are evenly spread in the upper sealing material covering area of ​​the ingot head to form an iron particle layer with a thickness of 0.5~1mm, and the iron particles are metal granules.

[0042] A dummy bar is installed at the end of the dummy bar. The dummy bar, as the starting component for traction of the billet in the continuous casting process, is used to achieve the initial bonding between the molten steel and the dummy bar during the initial pouring stage. When the high-temperature molten steel is continuously poured into the crystallizer, it quickly solidifies into one with the dummy bar. For example... Figure 2 As shown, if the dummy bar deforms, the deformation amount is calculated as: dummy bar actual measured height - dummy bar original height H. The main structure of the dummy bar head includes a flat area 5 and a beveled area 6. The flat area 5 is the planar load-bearing area on the dummy bar head, serving as the primary surface for cold material filling and initial contact with molten steel. The beveled area 6 connects to the end of the flat area 5, with both beveled areas 6 located on the same side of the flat area 5. A dovetail-shaped groove is formed between the two beveled areas 6 to allow molten steel to pass through. The original height H of the dummy bar, marked in the figure, is the initial height parameter of the dummy bar head in its undeformed state and serves as the benchmark for subsequent dummy bar deformation detection.

[0043] When the dredger head is in a non-deformed state (such as...) Figure 3 As shown in the figure, during the casting process, after the molten steel is pretreated by the cold material and the cooling frame, it is evenly spread and comes into contact with the working surface of the ingot head. The contact area between the molten steel and the ingot head can achieve a sufficient and uniform cooling effect, ensuring the stability of subsequent bonding.

[0044] When the derrick head deforms (such as...) Figure 4 As shown, the deformation area of ​​the dummy bar forms a protruding structure, with gaps naturally forming on both sides of this structure. Due to this protrusion, the cooling frame cannot maintain a close fit with the dummy bar, making it easy for high-temperature molten steel to seep into these gaps during casting. Because the cooling intensity in the gap area is insufficient, it is difficult to form a strong and structurally stable bond between the molten steel and the dummy bar. Furthermore, due to the insufficient cooling effect, the shell formed in this area is the thinnest and has the lowest strength. When the billet is pulled out of the crystallizer by the dummy bar, the shell is prone to tearing, ultimately leading to a steel leakage accident.

[0045] Therefore, it is necessary to specifically improve the cooling intensity of the aforementioned gap area. This can be achieved by adding a first cold material 13 to the gap area. The first cold material 13 can be placed in the gap between the protruding structure of the ingot head deformation area and the cooling frame to enhance the cooling effect of the molten steel in the gap and avoid the problem of a thin billet shell.

[0046] In step S3 above, the quantity of the second cold material 14 and the first cold material 13 must meet the following requirements: 1. When the cross-section of the round billet is Φ600mm, the number of second cold materials 14 on the outer ring 1 is 40~45, the number of second cold materials 14 on the middle ring 2 is 30~35, and the number of second cold materials 14 on the connecting rib 4 is 15~20. In the large flat area 5 of the derrick head, the number of first cold materials 13 is 10 to 15; In the inclined area 6 of the ingot head, the number of first cold materials 13 is 5 to 10.

[0047] 2. When the cross-section of the round billet is Φ700mm, the number of second cold materials 14 on the outer ring 1 is 50~55, the number of second cold materials 14 on the middle ring 2 is 30~35, the number of second cold materials 14 on the inner ring 3 is 12~15, and the number of second cold materials 14 on the connecting rib 4 is 15~20. In the large flat layer area 5 of the derrick head, the number of first cold materials 13 arranged is 15 to 20; In the inclined area 6 of the ingot head, the number of first cold materials 13 is 5 to 10.

[0048] 3. When the cross-section of the round billet is Φ800mm, the number of second cold materials 14 on the outer ring 1 is 50~55, the number of second cold materials 14 on the middle ring 2 is 35~40, the number of second cold materials 14 on the inner ring 3 is 12~15, and the number of second cold materials 14 on the connecting rib 4 is 30~40. In the large flat area 5 of the derrick head, the number of first cold materials 13 arranged is 20 to 25; In the inclined area 6 of the ingot head, the number of first cold materials 13 is 5 to 10.

[0049] 4. When the cross-section of the round billet is Φ900mm, the number of second cold materials 14 on the outer ring 1 is 60~65, the number of second cold materials 14 on the middle ring 2 is 40~45, the number of second cold materials 14 on the inner ring 3 is 12~15, and the number of second cold materials 14 on the connecting rib 4 is 30~40. In the large flat area 5 of the derrick head, the number of first cold materials 13 arranged is 25 to 30; In the inclined area 6 of the derrick head, the number of first cold materials 13 is 10 to 15.

[0050] 5. When the cross-section of the round billet is Φ1000mm, the number of second cold materials 14 on the outer ring 1 is 70~75, the number of second cold materials 14 on the middle ring 2 is 45~50, the number of second cold materials 14 on the inner ring 3 is 15~20, and the number of second cold materials 14 on the connecting rib 4 is 60~70. In the large flat area 5 of the derrick head, the number of first cold materials 13 arranged is 40 to 50; In the inclined area 6 of the derrick head, the number of first cold materials 13 is 10 to 20.

[0051] 6. When the cross-section of the round billet is Φ1100mm, the number of second cold materials 14 on the outer ring 1 is 75~80, the number of second cold materials 14 on the middle ring 2 is 55~60, the number of second cold materials 14 on the inner ring 3 is 15~20, and the number of second cold materials 14 on the connecting rib 4 is 80~90. In the large flat layer area 5 of the ingot head, the number of first cold materials 13 is 55 to 60; In the inclined area 6 of the derrick head, the number of first cold materials 13 is 10 to 20.

[0052] 7. When the cross-section of the round billet is Φ1200mm, the number of second cold materials 14 on the outer ring 1 is 80~85, the number of second cold materials 14 on the middle ring 2 is 60~65, the number of second cold materials 14 on the inner ring 3 is 15~20, and the number of second cold materials 14 on the connecting rib 4 is 95~100. In the large flat area 5 of the derrick head, the number of first cold materials 13 arranged is 45 to 50; In the inclined area 6 of the ingot head, the number of first cold materials 13 is 15 to 20.

[0053] In step S3 above, the filling method of the first cold material 13 in the large flat layer area 5 of the ingot head meets the following requirements: When the cross-section of the round billet is Φ600~Φ800mm, the first cold material 13 is filled by laying it flat, such as... Figure 6 As shown; When the cross-section of the round billet is Φ900~Φ1200mm, the first cold material 13 is filled by oblique insertion, such as... Figure 7 As shown.

[0054] In the cold material filling operation of step S3, the filling method of the first cold material 13 in the large flat layer area 5 of the ingot head must match the cross-sectional specifications of the round billet to be produced: like Figure 6 As shown, when the cross-section of the round billet to be produced is Φ600mm to Φ800mm, the first cold material 13 is laid out in a flat manner in the large flat area 5. The first cold material 13 is laid out horizontally in the large flat area 5 of the dummy head, and the cooling frame is placed above the dummy head. The length direction of the first cold material 13 is perpendicular to the axis of the cooling frame and the dummy head, and efficient and uniform cooling can be achieved through surface contact. like Figure 7As shown, when the cross-section of the billet to be produced is Φ900mm to Φ1200mm, the first cold material 13 is arranged in a slanted manner in the large flat layer area 5 of the corresponding ingot head. The first cold material 13 passes downward through the cooling frame and contacts the large flat layer area 5 of the ingot head. The first cold material 13 is in an inclined state and leans against the cooling frame. The slanted arrangement is designed for the characteristics of large cross-section billets with large steel volume and high heat dissipation requirements. By increasing the distribution density of the cold material in the space and the length of the heat dissipation path, the cooling intensity is ensured to match the solidification requirements of the large cross-section billet, and stable cooling is achieved in the casting process of billets of different specifications.

[0055] In step S4 above, the formula for calculating the emergence time is: Emergence time = (D / 100-6)×k+1, where D is the cross-section of the round blank, and k is a coefficient and 0.5≤k≤0.7.

[0056] In step S4 above, the upper and lower limits of the emergence time satisfy the following conditions: When the cross-section of the round billet is Φ600mm, the emergence time is 1 minute; When the cross-section of the round billet is Φ700mm, the lower limit of the emergence time is 1.5min and the upper limit is 1.7min; When the cross-section of the round billet is Φ800mm, the lower limit of the emergence time is 2min and the upper limit is 2.4min; When the cross-section of the round billet is Φ900mm, the lower limit of the emergence time is 2.5min and the upper limit is 3.1min; When the cross-section of the round billet is Φ1000mm, the lower limit of the emergence time is 3min and the upper limit is 3.8min; When the cross-section of the round billet is Φ1100mm, the lower limit of the emergence time is 3.5min and the upper limit is 4.5min; When the cross-section of the round blank is Φ1200mm, the lower limit of the emergence time is 4min and the upper limit is 5.2min.

[0057] In step S4 above, the control method for the initial casting speed and the casting speed before exiting the crystallizer is as follows: When the superheat of molten steel is >60℃, the initial casting speed is V1, and the casting speed before exiting the crystallizer is V2, and V1≤V2; When the superheat of molten steel is 30℃~60℃, the initial casting speed is V3, and the casting speed before exiting the crystallizer is V4, with V3≤V4; When the superheat of molten steel is <30℃, the initial casting speed is V5, and the casting speed before exiting the crystallizer is V6, with V5≤V6.

[0058] In step S4 above, when the initial casting superheat is >60℃, the casting speed can only be increased after the dummy ingot head has completely exited the crystallizer. The initial casting speed is V1, and the casting speed V2 is used before the dummy ingot head has completely exited the crystallizer, satisfying V1≤V2. When the initial casting superheat is between 30~60℃, the casting speed can only be increased after the dummy ingot head has completely exited the crystallizer. The initial casting speed is V3, and the casting speed V4 is used before the dummy ingot head has completely exited the crystallizer, satisfying V3≤V4. When the initial casting superheat is <30℃, the casting speed can only be increased after the dummy ingot head has completely exited the crystallizer. The initial casting speed is V5, and the casting speed V6 is used before the dummy ingot head has completely exited the crystallizer, satisfying V5≤V6.

[0059] In step S4 above, the values ​​of initial pulling speed V1, pulling speed before exiting the crystallizer V2, initial pulling speed V3, pulling speed before exiting the crystallizer V4, initial pulling speed V5, and pulling speed before exiting the crystallizer V6 satisfy the following: When the cross-section of the round billet is Φ600mm, V1=0.08m / min, V2≤0.12m / min, V3=0.08m / min, V4≤0.13m / min, V5=0.08m / min, V6≤0.14m / min; When the cross-section of the round billet is Φ700mm, V1=0.06m / min, V2≤0.08m / min, V3=0.06m / min, V4≤0.08m / min, V5=0.06m / min, V6≤0.12m / min; When the cross-section of the round billet is Φ800mm, V1=0.06m / min, V2≤0.07m / min, V3=0.06m / min, V4≤0.07m / min, V5=0.06m / min, V6≤0.11m / min; When the cross-section of the round billet is Φ900mm, V1=0.06m / min, V2≤0.06m / min, V3=0.06m / min, V4≤0.06m / min, V5=0.06m / min, V6≤0.10m / min; When the cross-section of the round billet is Φ1000mm, V1=0.05m / min, V2≤0.05m / min, V3=0.05m / min, V4≤0.05m / min, V5=0.05m / min, V6≤0.08m / min; When the cross-section of the round billet is Φ1100mm, V1=0.04m / min, V2≤0.04m / min, V3=0.04m / min, V4≤0.04m / min, V5=0.04m / min, V6≤0.07m / min; When the cross-section of the round billet is Φ1200mm, V1=0.04m / min, V2≤0.04m / min, V3=0.04m / min, V4≤0.04m / min, V5=0.04m / min, and V6≤0.06m / min.

[0060] In step S4 above, the pulling speed adjustment rate after the dummy bar has completely exited the crystallizer is ≤0.02m / min. 2 Speeding is prohibited.

[0061] In step S4 above, the vibration parameters of the crystallizer are: vibration frequency of 70~120 times / minute and amplitude of 2.0~3.5mm.

[0062] In step S4 above, the water volume Q of the crystallizer satisfies: Q = 4.25 × D + 2360, where D is the cross-section of the round billet.

[0063] In step S4 above, the addition parameters of the protective slag in the crystallizer are as follows: it is added after the molten steel has completely flooded the cooling frame, the initial addition amount is 0.4~0.8 kg / t, and the thickness of the protective slag liquid layer in the crystallizer is maintained at 4~8 mm.

[0064] In this invention, the above-mentioned settings, which adjust the casting speed and exit time from the crystallizer according to the starting casting speed and solidification characteristics of different cross-sections, are designed to ensure that the initial billet shell has sufficient thickness and strength, preventing production accidents such as steel leakage. Simultaneously, the settings for casting speed control, vibration parameters, and water volume are also designed to match the solidification characteristics of molten steel at different cross-sections, ensuring stable production and guaranteeing product quality. The addition of protective slag and the setting of slag layer thickness are designed to achieve the desired slag formation effect within the crystallizer, promoting lubrication and heat transfer of the molten steel.

[0065] The extra-large cross-section round billet continuous casting start-up method of this invention has been continuously used in production without any negative quality impact. It reduces the frequency of replacement of the dummy bar after deformation, achieving an annual cost reduction of over one million yuan. At the same time, it effectively avoids the safety risks of continuous casting start-up, reduces the occurrence of production accidents such as dummy bar failure, billet stagnation, and steel leakage during start-up, ensures the stability of continuous casting production, and achieves simultaneous improvement in production efficiency and benefits. Example

[0066] The method for continuous casting of extra-large cross-section round billets in this embodiment is applicable to the continuous casting of round billets with a cross-section of Φ800mm, and includes the following steps: (1) Before production, it was confirmed that the original height of the Φ800mm cross section dummy rod was 165mm, the actual height was 175mm, the deformation range was 10mm, and the deformation was ≤40mm. (2) After the previous production is completed, the continuous casting machine enters the "preparation" mode and starts the ingot feeding operation. When the ingot head is 370mm away from the top of the crystallizer, the ingot feeding is stopped and the continuous casting machine mode is switched to the "hold" mode. (3) Use special high-temperature resistant mortar to seal and fill the gap between the ingot head and the copper tube of the crystallizer to prevent the high-temperature molten steel from overflowing from the gap in the early stage of casting. (4) The composition of the high-temperature resistant mortar used is: w(Al2O3) = 28%, w(SiO2) = 37%, w(C) = 9%, and the bulk density (110℃ x 24h) = 1.31 g / cm³. 3 ; (5) Apply high-temperature resistant putty evenly over a certain width, i.e., the distance from the inner wall of the copper tube of the crystallizer is L=2.5cm; (6) Spread iron particles evenly on the upper part of the mortar-covered area of ​​the ingot head to form an iron particle layer with a thickness of 0.8 mm. The iron particle layer plays a certain cooling role for the high-temperature molten steel in the early stage of casting. The area covered by iron particles is ≥ the area covered by mortar. (7) Slowly place the Φ800mm circular cooling frame, ensuring that the cooling frame is stable and does not shake, and that the upper surface is horizontal; (8) Install the second cold material 14 on the cooling frame. The second cold material 14 has a diameter of Φ5mm and a height of 220mm. There are 50 second cold materials 14 on the outer ring 1, 38 second cold materials 14 on the middle ring 2, 14 second cold materials 14 on the inner ring 3, and 30 second cold materials 14 on the connecting rib 4, for a total of 132.

[0067] The first cold material 13 has a diameter of Φ6mm and a height of 180mm; in the large flat area 5 of the dummy head, there are 20 pieces of the first cold material 13; in the inclined area 6 of the dummy head, there are 8 pieces of the first cold material 13, for a total of 28 pieces of the first cold material 13.

[0068] (9) The deformation of the dummy bar is within the range, and the filling method of the first cold material 13 of the Φ800mm cross-section large flat layer is to lay it flat. (10) Calculate the seedling emergence time according to the model = (D / 100-6)*k+1, where k is 0.6 and the seedling emergence time is controlled at 2.2 minutes; (11) The superheat of the molten steel in the ladle during the initial casting is 55°C. The initial casting speed is 0.06 m / min, and the casting speed is 0.07 m / min before the ingot head is completely out of the crystallizer. (12) After the ingot head has completely exited the crystallizer, start increasing the pulling speed, and the range of the pulling speed is 0.01m / min2; (13) The crystallizer vibrates at a frequency of 90 times per minute with an amplitude of 2.5 mm; (14) The water flow rate of the crystallizer is calculated according to the formula model and set to 5760 NL / min; (15) After the molten steel has completely filled the ingot frame, start adding the mold protective slag. The initial addition amount is 0.4 kg / t. (16) The thickness of the protective slag layer in the crystallizer was measured to be 6 mm and remained stable.

[0069] Following the above steps, the billet formed well after exiting the crystallizer, with no obvious cracks or delamination. Casting was stable, the ingot was successfully removed, and the overall production process was under normal control. Example

[0070] The method for continuous casting of extra-large cross-section round billets in this embodiment is applicable to the continuous casting of round billets with a cross-section of Φ1000mm, and includes the following steps: (1) Before production, it was confirmed that the original height of the Φ1000mm cross-section dummy bar was 170mm, the actual height was 215mm, and the deformation range was 45mm, which met the requirement of ≤60mm: (2) After the previous production is completed, the continuous casting machine enters the "preparation" mode and starts the ingot feeding operation. When the ingot head is 350mm away from the top of the crystallizer, the ingot feeding is stopped and the continuous casting machine mode is switched to the "hold" mode. (3) Use special high-temperature resistant mortar to seal and fill the gap between the ingot head and the copper tube of the crystallizer to prevent the high-temperature molten steel from overflowing from the gap in the early stage of casting. (4) The composition of the high-temperature resistant mortar used is: w(Al2O3) = 30%, w(SiO2) = 36%, w(C) = 10%, and the bulk density (110℃ x 24h) = 1.30 g / cm³. 3 ; (5) Apply high-temperature resistant putty evenly over a certain width, i.e., the distance from the inner wall of the copper tube of the crystallizer is L=3.2cm; (6) Spread iron particles evenly on the upper part of the mortar-covered area of ​​the ingot head to form an iron particle layer with a thickness of 0.5 mm. The iron particle layer plays a certain cooling role for the high-temperature molten steel in the early stage of casting. The area covered by iron particles is ≥ the area covered by mortar. (7) Slowly place the Φ1000mm circular cooling frame, ensuring that the cooling frame is stable and does not shake, and that the upper surface is horizontal; (8) Install the second cold material 14 on the cooling frame. The second cold material 14 has a diameter of Φ5mm and a height of 220mm. There are 70 second cold materials 14 on the outer ring 1, 50 second cold materials 14 on the middle ring 2, 18 second cold materials 14 on the inner ring 3, and 65 second cold materials 14 on the connecting rib 4, for a total of 203.

[0071] The first cold material 13 has a diameter of Φ8mm and a height of 170mm; in the large flat area 5 of the dummy head, there are 48 pieces of the first cold material 13; in the inclined area 6 of the dummy head, there are 16 pieces of the first cold material 13, for a total of 64 pieces of the first cold material 13.

[0072] (9) The deformation of the dummy bar is within the range, and the filling method of the first cold material 13 of the Φ1000mm cross-section large flat layer is to insert it obliquely; (10) Calculate the seedling emergence time according to the model = (D / 100-6)*k+1, k is 0.7, and the seedling emergence time is controlled at 3.8 minutes; (11) The superheat of the molten steel in the ladle during the initial casting is 35°C. The initial casting speed is 0.05 m / min, and the casting speed is 0.05 m / min before the ingot head is completely out of the crystallizer. (12) After the ingot head has completely exited the crystallizer, start increasing the pulling speed, and the range of the pulling speed is 0.01m / min2; (13) The crystallizer vibration frequency is 80 times / minute, and the amplitude is 2.2 mm; (14) The water flow rate of the crystallizer is calculated according to the formula model and set to 6610 NL / min; (15) After the molten steel has completely filled the ingot frame, start adding the mold protective slag. The initial addition amount is 0.5 kg / t. (16) The thickness of the protective slag layer in the crystallizer was measured to be 7 mm and remained stable.

[0073] Following the above steps, the billet formed well after exiting the crystallizer, with no obvious cracks or delamination. Casting was stable, the ingot was successfully removed, and the overall production process was under normal control.

[0074] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution; or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A method for continuous casting of extra-large cross-section round billets, applicable to the continuous casting of round billets with a cross-section of Φ600~Φ1200mm, characterized in that, Includes the following steps: S1. Deformation detection and compliance judgment of the dummy bar: Detect the actual measured height of the dummy bar, calculate the deformation, and determine whether the deformation meets the preset range; if not, repair or replace the dummy bar. S2. Seal the ingot rod: After the ingot rod is sent to the fixed position at the bottom of the crystallizer, seal the gap between the ingot rod and the crystallizer with sealing material; S3. Cold material filling: Iron particles, a cooling frame and a first cold material are laid on the ingot head of the ingot rod, and a second cold material is installed on the cooling frame; S4. Initial Casting Control: Determine the emergence time based on the cross-section of the billet, and control the initial casting speed and casting speed before exiting the crystallizer in combination with the superheat of the molten steel. Adjust the casting speed after the ingot head has completely exited the crystallizer.

2. The method for continuous casting of extra-large cross-section round billets according to claim 1, characterized in that, In step S1, the initial height of the guide rod is 165±5mm; the preset range is: When the cross-section of the round billet is Φ600mm, the deformation amount is ≤40mm; When the cross-section of the round billet is Φ700mm or Φ800mm, the deformation amount is ≤45mm; When the cross-section of the round billet is Φ900mm, the deformation amount is ≤50mm; When the cross-section of the round billet is Φ1000mm, the deformation amount is ≤60mm; When the cross-section of the round billet is Φ1100mm or Φ1200mm, the deformation amount is ≤65mm.

3. The method for continuous casting of extra-large cross-section round billets according to claim 1, characterized in that, In step S2, the sealing material is high-temperature resistant putty, and the composition of the high-temperature resistant putty meets the following requirements: w(Al2O3) ≥ 28%, w(SiO2) ≤ 38%, w(C) ≥ 8%, and the bulk density of the high-temperature resistant putty under the condition of 110℃×24h is ≥ 1.30g / cm³. 3 ; In step S2, the application width L of the sealing material satisfies 1.5cm≤L≤3.5cm.

4. The method for continuous casting of extra-large cross-section round billets according to any one of claims 1 to 3, characterized in that, In step S2, the position s of the ingot head of the ingot rod from the top opening of the crystallizer satisfies: When the cross-section of the round billet is Φ600~Φ700mm, s=390mm; When the cross-section of the round billet is Φ800~Φ900mm, s=370mm; When the cross-section of the round billet is Φ1000~Φ1200mm, s=350mm.

5. The method for continuous casting of extra-large cross-section round billets according to any one of claims 1 to 3, characterized in that, The cooling frame includes an outer ring, a middle ring, an inner ring, and connecting ribs. The outer ring, middle ring, and inner ring are circular ring structures and are coaxially arranged. The connecting ribs are connected to the outer ring, middle ring, and / or inner ring and are perpendicular to the axes of the outer ring, middle ring, and inner ring. In step S3, the quantities of the second cold material and the first cold material are satisfied as follows: When the cross-section of the round billet is Φ600mm, the amount of the second cold material on the outer ring is 40~45, the amount of the second cold material on the middle ring is 30~35, and the amount of the second cold material on the connecting rib is 15~20. In the large flat layer area of ​​the dummy bar head, the quantity of the first cold material is 10~15; In the beveled area of ​​the derrick head, the amount of the first cold material is 5 to 10.

6. The method for continuous casting of extra-large cross-section round billets according to any one of claims 1 to 3, characterized in that, The cooling frame includes an outer ring, a middle ring, an inner ring, and connecting ribs. The outer ring, middle ring, and inner ring are circular ring structures and are coaxially arranged. The connecting ribs are connected to the outer ring, middle ring, and / or inner ring and are perpendicular to the axes of the outer ring, middle ring, and inner ring. In step S3, the quantities of the second cold material and the first cold material are satisfied as follows: When the cross-section of the round billet is Φ700mm, the amount of the second cold material on the outer ring is 50~55, the amount of the second cold material on the middle ring is 30~35, the amount of the second cold material on the inner ring is 12~15, and the amount of the second cold material on the connecting rib is 15~20. In the large flat layer area of ​​the dummy bar head, the quantity of the first cold material is 15~20; In the beveled area of ​​the derrick head, the amount of the first cold material is 5 to 10.

7. The method for continuous casting of extra-large cross-section round billets according to any one of claims 1 to 3, characterized in that, The cooling frame includes an outer ring, a middle ring, an inner ring, and connecting ribs. The outer ring, middle ring, and inner ring are circular ring structures and are coaxially arranged. The connecting ribs are connected to the outer ring, middle ring, and / or inner ring and are perpendicular to the axes of the outer ring, middle ring, and inner ring. In step S3, the quantities of the second cold material and the first cold material are satisfied as follows: When the cross-section of the round billet is Φ800mm, the amount of the second cold material on the outer ring is 50~55, the amount of the second cold material on the middle ring is 35~40, the amount of the second cold material on the inner ring is 12~15, and the amount of the second cold material on the connecting rib is 30~40. In the large flat layer area of ​​the dummy head, the quantity of the first cold material is 20~25; In the beveled area of ​​the derrick head, the amount of the first cold material is 5 to 10.

8. The method for continuous casting of extra-large cross-section round billets according to any one of claims 1 to 3, characterized in that, The cooling frame includes an outer ring, a middle ring, an inner ring, and connecting ribs. The outer ring, middle ring, and inner ring are circular ring structures and are coaxially arranged. The connecting ribs are connected to the outer ring, middle ring, and / or inner ring and are perpendicular to the axes of the outer ring, middle ring, and inner ring. In step S3, the quantities of the second cold material and the first cold material are satisfied as follows: When the cross-section of the round billet is Φ900mm, the amount of the second cold material on the outer ring is 60~65, the amount of the second cold material on the middle ring is 40~45, the amount of the second cold material on the inner ring is 12~15, and the amount of the second cold material on the connecting rib is 30~40. In the large flat layer area of ​​the dummy bar head, the quantity of the first cold material is 25~30; In the beveled area of ​​the derrick head, the amount of the first cold material is 10~20.

9. The method for continuous casting of extra-large cross-section round billets according to any one of claims 1 to 3, characterized in that, The cooling frame includes an outer ring, a middle ring, an inner ring, and connecting ribs. The outer ring, middle ring, and inner ring are circular ring structures and are coaxially arranged. The connecting ribs are connected to the outer ring, middle ring, and / or inner ring and are perpendicular to the axes of the outer ring, middle ring, and inner ring. In step S3, the quantities of the second cold material and the first cold material are satisfied as follows: When the cross-section of the round billet is Φ1000mm, the amount of the second cold material on the outer ring is 70~75, the amount of the second cold material on the middle ring is 45~50, the amount of the second cold material on the inner ring is 15~20, and the amount of the second cold material on the connecting rib is 60~70. In the large flat area of ​​the dummy bar head, the quantity of the first cold material is 40~50; In the beveled area of ​​the derrick head, the amount of the first cold material is 10~20.

10. The method for continuous casting of extra-large cross-section round billets according to any one of claims 1 to 3, characterized in that, The cooling frame includes an outer ring, a middle ring, an inner ring, and connecting ribs. The outer ring, middle ring, and inner ring are circular ring structures and are coaxially arranged. The connecting ribs are connected to the outer ring, middle ring, and / or inner ring and are perpendicular to the axes of the outer ring, middle ring, and inner ring. In step S3, the quantities of the second cold material and the first cold material are satisfied as follows: When the cross-section of the round billet is Φ1100mm, the amount of the second cold material on the outer ring is 75~80, the amount of the second cold material on the middle ring is 55~60, the amount of the second cold material on the inner ring is 15~20, and the amount of the second cold material on the connecting rib is 80~90. In the large flat layer area of ​​the dummy bar head, the quantity of the first cold material is 55~60; In the beveled area of ​​the derrick head, the amount of the first cold material is 10~20.

11. The method for continuous casting of extra-large cross-section round billets according to any one of claims 1 to 3, characterized in that, The cooling frame includes an outer ring, a middle ring, an inner ring, and connecting ribs. The outer ring, middle ring, and inner ring are circular ring structures and are coaxially arranged. The connecting ribs are connected to the outer ring, middle ring, and / or inner ring and are perpendicular to the axes of the outer ring, middle ring, and inner ring. In step S3, the quantities of the second cold material and the first cold material are satisfied as follows: When the cross-section of the round billet is Φ1200mm, the amount of the second cold material on the outer ring is 80~85, the amount of the second cold material on the middle ring is 60~65, the amount of the second cold material on the inner ring is 15~20, and the amount of the second cold material on the connecting rib is 95~100. In the large flat layer area of ​​the dummy bar head, the quantity of the first cold material is 45~50; In the beveled area of ​​the derrick head, the amount of the first cold material is 15~20.

12. The method for continuous casting of extra-large cross-section round billets according to any one of claims 1 to 11, characterized in that, In step S3, the filling method of the first cold material in the large flat layer area of ​​the ingot head satisfies the following: When the cross-section of the round billet is Φ600~Φ800mm, the first cold material is filled by laying it flat. When the cross-section of the round billet is Φ900~Φ1200mm, the first cold material is filled by oblique insertion.

13. The method for continuous casting of extra-large cross-section round billets according to any one of claims 1 to 12, characterized in that, In step S4, the formula for calculating the emergence time is: emergence time = (D / 100-6)×k+1, where D is the cross-section of the round blank, and k is a coefficient and 0.5≤k≤0.

7.

14. The method for continuous casting of extra-large cross-section round billets according to any one of claims 1 to 12, characterized in that, In step S4, the control method for the initial casting speed and the casting speed before exiting the crystallizer is as follows: When the superheat of molten steel is >60℃, the initial casting speed is V1, and the casting speed before exiting the crystallizer is V2, and V1≤V2; When the superheat of molten steel is 30℃~60℃, the initial casting speed is V3, and the casting speed before exiting the crystallizer is V4, with V3≤V4; When the superheat of molten steel is <30℃, the initial casting speed is V5, and the casting speed before exiting the crystallizer is V6, with V5≤V6.

15. The method for continuous casting of extra-large cross-section round billets according to any one of claims 1 to 12, characterized in that, In step S4, the vibration parameters of the crystallizer are: vibration frequency of 70~120 times / minute and amplitude of 2.0~3.5mm.

16. The method for continuous casting of extra-large cross-section round billets according to any one of claims 1 to 12, characterized in that, In step S4, the water volume Q in the crystallizer satisfies: Q = 4.25 × D + 2360, where D is the cross-section of the round billet.

17. The method for continuous casting of extra-large cross-section round billets according to any one of claims 1 to 12, characterized in that, In step S4, the addition parameters of the protective slag in the crystallizer are as follows: it is added after the molten steel has completely flooded the cooling frame, the initial addition amount is 0.4~0.8 kg / t, and the thickness of the protective slag liquid layer in the crystallizer is maintained at 4~8 mm.

18. The method for continuous casting of extra-large cross-section round billets according to any one of claims 1 to 12, characterized in that, When the derrick head deforms, the first cold material is placed in the gap formed between the protruding structure in the deformation area of ​​the derrick head and the cooling frame.

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