Continuous casting process for controlling center segregation and hot banding cracks of continuously cast slabs

Abstract

This invention discloses a continuous casting process method for controlling center segregation and hot-feeding cracks in continuously cast billets. This method adjusts the casting speed and the total amount of water in the secondary cooling system to shift the solidification end of the billet to the horizontal section, ensuring that the solidification end has not yet reached the straightening section when the billet is straightened, thus avoiding the process risks associated with forced cooling followed by straightening. Forced cooling is applied to the billet surface throughout the entire horizontal secondary cooling zone and a predetermined range upstream of the solidification end, controlling the billet's exit surface temperature below 600℃. This process, through the coordinated control of casting speed and cooling, utilizes forced cooling to enhance the cold compression effect and strengthen center segregation control, while also achieving surface quenching of the billet through continuous forced cooling, eliminating the causes of hot-feeding cracks, and significantly improving the internal and surface quality of the continuously cast billet.

Description

Technical Field

[0001] This invention belongs to the field of metal smelting technology, specifically relating to a continuous casting process method for controlling center segregation and hot-feeding cracks in continuously cast billets. Background Technology

[0002] Continuous casting is the process of solidifying liquid steel into solid steel billets. During the solidification process, selective crystallization occurs, meaning that the structure that solidifies first has a lower alloy content, while the structure that solidifies later has a higher alloy content. The alloy content is high near the end of solidification. This non-uniformity of composition is called segregation. Segregation will cause uneven properties of the steel, so controlling segregation is crucial.

[0003] High-strength low-alloy steels are prone to hot-feed cracking. The mechanism of hot-feed cracking is that the melting temperature of ferrite in low-carbon steel is around 723℃. When the billet is hot-feeded into the furnace, the surface temperature of the billet is around 723℃. During the heating process, the thin film of ferrite near the grain boundaries transforms again into fine austenite, forming a mixed-grain structure composed of austenite refined by phase transformation and the original coarse austenite. At the same time, the residual ferrite film and unmelted second-phase precipitates are still distributed at the austenite grain boundaries, reducing the grain boundary plasticity. These phenomena reduce the high-temperature mechanical properties of the billet, causing stress concentration at the grain boundaries, thus leading to hot brittleness of the steel. In addition, the surface of the billet is subjected to large tensile stress in the initial stage of heating, so cracks are prone to occur in the furnace and propagate during the subsequent rolling process.

[0004] The hot-pressing process, characterized by strong cooling at the solidification end, is a low-cost method for controlling segregation. This process involves strong cooling at the solidification end, causing the billet surface to shrink and compress the core, thus dispersing the liquid core with high solute content and reducing center segregation. However, when the cooling intensity is too high, the billet surface temperature becomes too low, leading to increased brittleness. This makes it easy for transverse cracks to appear on the billet surface during the straightening process. In other words, this method is limited by the billet surface temperature, restricting the cooling intensity at the solidification end and limiting the effectiveness of the hot-pressing process.

[0005] Currently, the main method for controlling hot-feeding cracks is to use red billet quenching to reduce the surface temperature of the billet to below 600℃, so that the surface temperature of the billet is lower than the temperature at which hot-feeding cracks are easily generated. This improves the surface quality of the billet without reducing too much heat loss. However, this requires the purchase of equipment and occupies space, and it is difficult to modify continuous casting machines with compact plant layouts.

[0006] This invention provides a continuous casting process method for controlling center segregation and hot-feeding cracks in continuously cast billets, particularly concerning how to improve the internal and surface quality of continuously cast billet products. Summary of the Invention

[0007] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention provides a continuous casting process method for controlling center segregation and hot-feeding cracks in continuously cast billets, with the purpose of improving the internal and surface quality of continuously cast billet products.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a continuous casting process method for controlling center segregation and hot-feeding cracks in continuously cast billets. During the continuous casting process, molten steel is formed in a crystallizer and then passes through the arc section, straightening section, and horizontal section of the continuous casting machine to complete solidification and conveying. The billet is cooled by a secondary cooling system. The continuous casting speed and the total specific water volume of the secondary cooling system are matched and adjusted to move the solidification end of the billet to the axial range of the horizontal section, so that the solidification end of the billet does not reach the straightening section when the straightening process is completed. In the secondary cooling zone of the horizontal section within a preset range upstream of the solidification end of the billet and thereafter, a strong cooling process is applied to the surface of the billet throughout the entire process, controlling the surface temperature of the billet when it exits the continuous casting machine to be below 600℃. The specific water volume of the horizontal section corresponding to the strong cooling process is 0.6~0.9L / kg, and the total specific water volume of the secondary cooling system is 0.9~1.5L / kg.

[0009] When casting peritectic steel, the continuous casting speed is controlled at 1.3m / min to 1.5m / min, and the specific water volume before the horizontal section is controlled at 0.3L / kg to 0.6L / kg.

[0010] After the aforementioned strong cooling process, the surface temperature of the billet exiting the continuous casting machine is controlled between 550℃ and 600℃.

[0011] After the billet enters the horizontal section, the full-section strong cooling process of the horizontal section is started from 21m away from the meniscus of the crystallizer. The strong cooling zone covers the entire end range of the horizontal section from 21m to 26m. The specific water volume of the strong cooling process is stably controlled at 0.75L / kg.

[0012] The solidification end of the billet is located within the axial range of the inlet side of the horizontal section, and the axial distance between the solidification end and the outlet of the straightening section is not less than 1m.

[0013] The starting axial position of the forced cooling process is no earlier than 1m upstream of the end of the solidification of the billet, and the ending axial position of the forced cooling process coincides with the outlet end of the horizontal section.

[0014] The cooling intensity of the intensive cooling process is higher than the secondary cooling intensity when the billet passes through the arc section and the straightening section.

[0015] Within the arc section before the straightening section, the intensity of the secondary cooling decreases uniformly along the pulling direction, while the thickness of the billet shell increases uniformly along the pulling direction.

[0016] After undergoing strong cooling treatment, the billet is directly fed into the heating furnace while hot after exiting the continuous casting machine. During the hot feeding process, the surface temperature of the billet is not lower than 500℃.

[0017] The continuous casting process method for controlling center segregation and hot-feeding cracks in continuously cast billets of the present invention, through matching and regulating the casting speed and the secondary cooling water ratio, moves the solidification end to the horizontal section, so that the straightening process of the billet is completely completed before the strong cooling zone, avoiding the process risk of straightening after strong cooling. The cooling intensity at the solidification end is no longer limited, which can enhance the cold pressing effect and strengthen the control capability of center segregation. At the same time, the surface quenching of the billet is achieved through strong cooling throughout the process, eliminating the inducing factors of hot-feeding cracks and improving the internal and surface quality of the continuously cast billet. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Non-creative modifications and parameter adaptations made by those skilled in the art based on the inventive concept are all within the scope of protection of the present invention.

[0019] This invention addresses the technical problems existing in current continuous casting processes. In the prior art, the control of center segregation and hot-feeding cracks in continuously cast billets are two separate process systems, with irreconcilable contradictions. For controlling center segregation, the mainstream industry approach is a strong cooling "hot pressing" process at the solidification end. This process applies strong cooling to the surface of the billet at the solidification end, utilizing the rapid solidification shrinkage of the surface layer to compress the liquid core, dispersing the solute-rich residual liquid core and thus reducing center segregation. However, in existing solutions, the solidification end is often within the straightening or arc-shaped section. Significantly increasing the cooling intensity to enhance the hot pressing effect would cause the surface temperature of the billet to drop to the third brittle range of steel during straightening, easily generating straightening transverse cracks. Therefore, the cooling intensity at the solidification end is always strictly limited by the straightening process, preventing further improvement in the hot pressing effect and creating a significant bottleneck in center segregation control. To control hot-feeding cracks, the mainstream approach in the industry is to use a red billet quenching process at the outlet of the continuous casting machine. This process reduces the surface temperature of the billet to below 600°C through secondary quenching, thus avoiding the critical range of hot brittleness. However, this process requires the addition of dedicated quenching equipment, resulting in high equipment investment and modification costs. Furthermore, the secondary cooling further increases the heat loss of the billet, which contradicts the energy-saving purpose of hot-feeding and hot-charging. At the same time, the existing two separate processes cannot simultaneously address the internal and surface quality of the billet. Often, while controlling center segregation, it exacerbates the risk of surface cracks, and while controlling hot-feeding cracks, it fails to solve the problem of center segregation.

[0020] The continuous casting process method for controlling center segregation and hot-feeding cracks in continuously cast billets provided by this invention mainly involves adjusting the casting speed and the secondary cooling water ratio to move the solidification end of the billet to the horizontal section of the continuous casting machine, thus completely eliminating the limitation of the straightening process on the cooling intensity at the solidification end and significantly improving the cooling intensity at the solidification end compared to existing technologies. Simultaneously, through a full-process strong cooling process near the solidification end and throughout the entire horizontal section thereafter, two major technical effects are achieved within a single process system: First, the radial compression effect of the billet surface shrinkage on the liquid core during strong cooling creates a cold compression effect, effectively controlling center segregation of the billet; second, the surface temperature of the billet exiting the continuous casting machine is stably controlled below 600℃ through full-process strong cooling, achieving a surface quenching effect and eliminating the root cause of hot-feeding cracks. No new equipment or modifications to the secondary cooling chamber structure are required, resulting in extremely low industrial implementation costs and strong adaptability.

[0021] This invention provides a continuous casting process method for controlling center segregation and hot-feeding cracks in continuously cast billets. During continuous casting, molten steel is formed in a crystallizer and then passes through the arc section, straightening section, and horizontal section of the continuous casting machine to complete solidification and conveying. The billet is cooled by a secondary cooling system. The continuous casting speed and the total specific water volume of the secondary cooling system are matched and adjusted to move the solidification end of the billet forward into the axial range of the horizontal section, so that the solidification end of the billet does not reach the straightening section when the billet completes the straightening process. In the secondary cooling zone of the horizontal section within a preset range upstream of the solidification end of the billet and thereafter, a strong cooling process is applied to the surface of the billet throughout the entire process, controlling the surface temperature of the billet when it exits the continuous casting machine to be below 600°C. The specific water volume of the horizontal section corresponding to the strong cooling process is 0.6~0.9 L / kg, and the total specific water volume of the secondary cooling system is 0.9~1.5 L / kg.

[0022] When casting peritectic steel, the continuous casting speed is controlled at 1.3m / min to 1.5m / min, and the secondary cooling water volume is controlled at 0.3L / kg to 0.6L / kg.

[0023] After the aforementioned strong cooling process, the surface temperature of the billet exiting the continuous casting machine is controlled between 550℃ and 600℃.

[0024] After the billet enters the horizontal section, the full-section strong cooling process of the horizontal section is started from 21m away from the meniscus of the crystallizer. The strong cooling zone covers the entire end range of the horizontal section from 21m to 26m. The specific water volume of the strong cooling process is stably controlled at 0.75L / kg.

[0025] The solidification end of the billet is located within the axial range of the inlet side of the horizontal section, and the axial distance between the solidification end and the outlet of the straightening section is not less than 1m.

[0026] The starting axial position of the forced cooling process is no earlier than 1m upstream of the end of the solidification of the billet, and the ending axial position of the forced cooling process coincides with the outlet end of the horizontal section.

[0027] The cooling intensity of the intensive cooling process is higher than the secondary cooling intensity when the billet passes through the arc section and the straightening section.

[0028] Within the arc section before the straightening section, the secondary cooling intensity increases uniformly along the drawing direction, and the billet shell thickness increases uniformly along the drawing direction, thus avoiding bulging deformation and intermediate cracks caused by uneven billet shell growth.

[0029] After undergoing strong cooling treatment, the billet is directly fed into the heating furnace while hot after exiting the continuous casting machine. During the hot feeding process, the surface temperature of the billet is not lower than 500℃.

[0030] The continuous casting machine used in this embodiment of the invention is a straight-arc slab continuous casting machine. After the molten steel is continuously formed into a slab through the crystallizer, it is conveyed and solidified sequentially through the foot roller section, arc section, straightening section and horizontal section of the continuous casting machine, and finally delivered hot through the billet discharge roller table. The secondary cooling system of the continuous casting machine is divided into multiple independent and controllable cooling zones. The arc section, straightening section and horizontal section correspond to independent cooling circuits. The cooling water volume and cooling intensity of each cooling circuit can be adjusted independently. The strong cooling process in this embodiment of the invention is implemented entirely based on the horizontal section cooling circuit of the original secondary cooling system of the continuous casting machine. No new hardware equipment is added and no modification is made to the structure of the secondary cooling chamber. In this embodiment of the invention, the solidification end refers to the axial position where the liquid core of the billet completely disappears and the solid fraction reaches 100% along the casting direction; the total cooling water volume of the secondary cooling system refers to the ratio of the total cooling water volume of the secondary cooling system per unit time to the mass of molten steel cast per unit time during continuous casting; the horizontal section cooling water volume refers to the ratio of the cooling water volume of the horizontal section cooling circuit per unit time to the mass of molten steel cast per unit time, with the unit being L / kg.

[0031] Specifically, in this embodiment of the invention, the continuous casting speed and the total amount of water in the secondary cooling are matched and adjusted. The casting speed and the total amount of water in the secondary cooling are positively correlated and matched. When the casting speed is increased, the total amount of water in the secondary cooling is increased simultaneously, and when the casting speed is decreased, the total amount of water in the secondary cooling is decreased simultaneously. This ensures that the solidification end of the billet moves stably forward to the axial range of the horizontal section, and that when the billet completes the straightening process, the solidification end has not reached the straightening section. That is, the straightening process of the billet is completely completed before the strong cooling zone at the solidification end, thus avoiding the process risk of "straightening after strong cooling" from the root. The total water volume of the secondary cooling process is controlled at 1.2~1.5L / kg. This parameter range has been verified by a large number of industrial tests. It can ensure that the solidification end of the billet moves stably to the horizontal section, and avoid the excessive cooling intensity of the arc section causing the surface temperature of the billet in the straightening section to enter the brittle range. At the same time, the solidification end of the billet is preferably set in the axial range of the inlet side of the horizontal section, and the axial distance between the solidification end and the outlet of the straightening section is not less than 1m, so as to reserve sufficient adjustment space for the initial setting of the strong cooling process.

[0032] In this embodiment of the invention, a strong cooling process is applied to the surface of the billet throughout the entire horizontal section of the secondary cooling zone, within a preset range upstream of the end of the billet's solidification. The starting axial position of the strong cooling process is 0.5m to 1m upstream of the end of the billet's solidification, and the ending axial position of the strong cooling process coincides with the outlet end of the horizontal section of the secondary cooling zone, ensuring that the entire solidification process of the billet is within the strong cooling zone. The specific water volume in the horizontal section corresponding to the strong cooling process is controlled at 0.6~0.9L / kg. This parameter range is the range for achieving the technical effect of the embodiment of the present invention. If the specific water volume in the horizontal section is less than 0.6L / kg, the cooling intensity is insufficient. On the one hand, the surface shrinkage of the billet is insufficient, the cold pressing effect is weak, and the center segregation cannot be effectively controlled. On the other hand, the surface temperature of the billet exiting the continuous casting machine cannot be reduced to below 600℃, and the surface quenching effect cannot be achieved, and hot delivery cracks cannot be controlled. If the specific water volume in the horizontal section is greater than 0.9L / kg, the cooling intensity is too large, the temperature gradient between the surface and core of the billet is too large, and excessive internal stress is easily generated, causing surface micro-cracks. At the same time, excessive cooling leads to excessive heat loss of the billet, which violates the energy-saving intention of hot delivery and hot charging. During the forced cooling process, the core of the billet still retains an unsolidified liquid core. The surface layer of the billet undergoes rapid solidification and shrinkage due to forced cooling, which exerts a continuous radial compression effect on the liquid core in the core, i.e., the thermal compression effect. This disperses the residual liquid core enriched with solute at the end of solidification, inhibits the accumulation of solute elements towards the center of the billet, and controls the generation of center segregation from the root. At the same time, through forced cooling throughout the entire horizontal section from the end of solidification, the surface temperature of the billet when it exits the continuous casting machine is stably controlled below 600℃, preferably between 550℃ and 600℃. This completely avoids the critical temperature range of hot brittleness for high-strength low-alloy steel, peritectic steel, and other steel grades, achieving a surface quenching effect for the billet and fundamentally eliminating the microstructural factors that induce hot-feeding cracks.

[0033] After being subjected to strong cooling treatment, the billet exits the continuous casting machine and is directly fed into the hot rolling furnace via an insulated roller conveyor. During the hot feeding process, the surface temperature of the billet is not lower than 500℃. This ensures the surface and internal quality of the billet while maximizing the retention of heat in the core of the billet, reducing the fuel consumption of the hot rolling furnace, and achieving the dual benefits of quality improvement and energy saving.

[0034] The technical solutions and effects of the embodiments of the present invention will be verified and explained in detail below through specific examples and comparative examples.

[0035] The general test conditions used in the examples and comparative examples are as follows: The continuous casting machine used in the experiment was a straight arc slab continuous casting machine of a steel plant. The arc radius of the continuous casting machine was 9.5m. The continuous casting machine roller line was divided into a foot roller section, an arc section, a straightening section, and a horizontal section. The starting position of the horizontal section was 18m away from the meniscus of the crystallizer, and the ending position of the horizontal section was 26m away from the meniscus of the crystallizer, which is the starting position of the billet exit roller table of the continuous casting machine.

[0036] The secondary cooling system is divided into 5 independent cooling zones: zone 0 for the foot roller section, zones 1, 2, and 3 for the arc section, zone 4 for the straightening section, and zone 5 for the horizontal section. Each cooling zone uses air mist cooling and the cooling water and air volume can be adjusted independently. All test schemes were implemented through the existing secondary cooling system without adding any new equipment or modifying the structure of the secondary cooling chamber. Example

[0037] This embodiment provides a continuous casting process method for controlling center segregation and hot-feeding cracks in continuously cast billets. The specific process parameters and implementation steps are as follows: 1. Process Parameter Matching and Solidification End Positioning: Based on the continuous casting machine parameters and steel composition, the continuous casting speed was set to 1.4 m / min through solidification heat transfer numerical simulation calculation. The total specific water volume of the secondary cooling system was set to 1.3 L / kg, of which the specific water volume of the horizontal section was 0.75 L / kg, and the total specific water volume of the arc section and straightening section was 0.55 L / kg. Under these process parameters, the solidification end position of the billet was 22 m from the meniscus of the crystallizer, completely within the axial range of the horizontal section (18 m-26 m), meeting the preset requirements.

[0038] 2. Implementation of Full-Process Forced Cooling in the Horizontal Section: After the billet enters the horizontal section, the full-process forced cooling is initiated starting 21m from the meniscus of the crystallizer (i.e., 1m upstream of the solidification end). The forced cooling zone covers the entire end range of the horizontal section from 21m to 26m. The specific water content of the forced cooling process is stably controlled at 0.75L / kg. During the forced cooling process, the core of the billet still retains an unsolidified liquid core. The surface layer of the billet rapidly solidifies and shrinks under forced cooling, generating a continuous radial compression effect on the liquid core in the core, forming a stable cold compression effect. This disperses the residual liquid core enriched with solute at the solidification end and inhibits the accumulation of solute elements towards the center of the billet. Continuous monitoring with an online infrared thermometer shows that the surface temperature of the billet exiting the continuous casting machine (26m) is 560℃~590℃, stably controlled below 600℃, completely avoiding the critical temperature range of hot brittleness, and achieving the surface quenching effect of the billet.

[0039] 3. Hot delivery of billets: After exiting the continuous casting machine, the billets are directly hot-delivered into the hot rolling furnace via the heat-insulating roller conveyor. During the hot delivery process, the surface temperature of the billets is not lower than 530℃, which meets the process requirements of hot delivery and hot charging.

[0040] The billet quality inspection results of this embodiment are as follows: (1) Surface quality: After online surface flaw detector inspection and manual offline sampling inspection, the surface of the billet is free of any surface defects such as transverse cracks, longitudinal cracks, star-shaped cracks, etc., and can be directly hot-rolled without any surface cleaning.

[0041] (2) Low magnification structure and center segregation: According to the GB / T 1979-2001 standard, the low magnification structure of the billet is free of defects such as intermediate cracks, subcutaneous cracks, shrinkage cavities, and porosity. The center segregation level is Class C 1.0, which meets the internal quality requirements of high-end steel.

[0042] (3) Hot delivery crack control: After the billet is directly hot-delivered and hot-rolled, the hot-rolled steel plate is subjected to full-surface flaw detection. There are no surface defects related to hot delivery cracks on the steel plate surface.

[0043] Comparative Example 1 The steel grade, continuous casting machine equipment, and slab cross-sectional specifications of this comparative example are completely consistent with those of Example 1. The only difference is that the continuous casting speed is adjusted to 1.2 m / min, the total water volume of the secondary cooling remains unchanged at 1.3 L / kg, the water volume of the horizontal section is still 0.75 L / kg, and the total water volume of the arc section and the straightening section is 0.55 L / kg.

[0044] Through actual measurement and verification, under the process parameters of this comparative example, the solidification end position of the billet is 18m from the meniscus of the crystallizer, which is exactly at the junction of the straightening section and the horizontal section, i.e., the exit of the straightening section. To ensure the strong cooling effect at the end of solidification, the starting position of the strong cooling process was adjusted to 17m from the meniscus of the crystallizer, and the strong cooling zone covers a range of 17m-26m, of which the 17m-18m range is within the straightening section. According to online infrared thermometer detection, when the billet passes through the straightening section, due to the early implementation of the strong cooling process, the surface temperature of the billet drops to between 700℃ and 750℃, resulting in high brittleness and the appearance of transverse surface cracks on the billet surface.

[0045] Comparative Example 2 The steel grade, continuous casting machine equipment, and slab cross-sectional specifications of this comparative example are completely consistent with those of Example 1. The only difference is that the continuous casting speed is 1.2 m / min, and the total water content of the secondary cooling is reduced to 0.9 L / kg, of which the water content of the horizontal section is 0.75 L / kg, and the total water content of the arc section and the straightening section is 0.15 L / kg.

[0046] Through actual measurement and verification, this comparative example, by reducing the specific water volume in the arc-shaped and straightening sections, moved the solidification end forward to 20m from the meniscus of the crystallizer, placing it within the horizontal section. The starting position of the forced cooling process was 19m from the meniscus of the crystallizer, covering a horizontal section range of 19m-26m. However, due to the significant reduction in the specific water volume in the arc-shaped and straightening sections, the water vapor atomization effect was poor, resulting in intermittent water spraying, uneven secondary cooling, and severe intermediate crack defects detected at low magnification.

[0047] Comparative Example 3 The steel grade, continuous casting machine, slab cross-sectional specifications, casting speed, and total secondary cooling water volume of this comparative example are completely consistent with those of Example 1. The only difference is that the forced cooling process was not implemented in the horizontal section, the water volume of the horizontal section was adjusted to 0.35L / kg, and the total secondary cooling water volume of 0.9L / kg was 0.55L / kg in the arc section and the straightening section.

[0048] Actual measurements confirmed that the solidification endpoint in this comparative example was 22m from the meniscus of the crystallizer, consistent with Example 1, and within the horizontal section. The surface temperature of the billet during the straightening section was 910℃~940℃, within the plastic range, and no straightening cracks were generated. However, due to the absence of a strong cooling process in the horizontal section, a cold pressing effect could not be achieved, and the surface quenching effect of the billet could not be realized.

[0049] The quality inspection results of the billet in this comparative example are as follows: there are no straightening cracks on the surface of the billet, and the surface quality is qualified; however, the segregation level of the center of the billet is Class C 2.0, which is serious and cannot meet the quality requirements of high-end steel; the surface temperature of the billet when it leaves the continuous casting machine is 710℃~750℃, which is in the critical temperature range of hot brittleness. After the billet is directly hot-sent, hot-sent cracks are likely to occur.

[0050] The present invention has been described above by way of example. 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 of the present invention; 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 continuous casting process method for controlling center segregation and hot-feeding cracks in continuously cast billets, wherein molten steel, after being formed in a crystallizer, sequentially passes through the arc section, straightening section, and horizontal section of the continuous casting machine to complete solidification and conveying, and the billet is cooled by a secondary cooling system, characterized in that: Match and adjust the continuous casting speed and the total specific water volume of the secondary cooling system to move the solidification end of the billet to the axial range of the horizontal section, so that the solidification end of the billet does not reach the straightening section when the billet completes the straightening process; apply a strong cooling process to the surface of the billet throughout the entire secondary cooling zone of the horizontal section upstream of the solidification end of the billet and thereafter, so as to control the surface temperature of the billet when it exits the continuous casting machine below 600℃; the specific water volume of the horizontal section corresponding to the strong cooling process is 0.6~0.9L / kg, and the total specific water volume of the secondary cooling system is 0.9~1.5L / kg.

2. The continuous casting process method according to claim 1, characterized in that, When casting peritectic steel, the continuous casting speed is controlled at 1.3m / min to 1.5m / min, and the specific water volume before the horizontal section is controlled at 0.3L / kg to 0.6L / kg.

3. The continuous casting process method according to claim 1, characterized in that, After the aforementioned strong cooling process, the surface temperature of the billet exiting the continuous casting machine is controlled between 550℃ and 600℃.

4. The continuous casting process method according to any one of claims 1 to 3, characterized in that, After the billet enters the horizontal section, the full-section strong cooling process of the horizontal section is started from 21m away from the meniscus of the crystallizer. The strong cooling zone covers the entire end range of the horizontal section from 21m to 26m. The specific water volume of the horizontal section of the strong cooling process is stably controlled at 0.75L / kg.

5. The continuous casting process method according to any one of claims 1 to 3, characterized in that, The solidification end of the billet is located within the axial range of the inlet side of the horizontal section, and the axial distance between the solidification end and the outlet of the straightening section is not less than 1m.

6. The continuous casting process method according to any one of claims 1 to 3, characterized in that, The starting axial position of the forced cooling process is no earlier than 1m upstream of the end of the solidification of the billet, and the ending axial position of the forced cooling process coincides with the outlet end of the horizontal section.

7. The continuous casting process method according to any one of claims 1 to 3, characterized in that, The cooling intensity of the intensive cooling process is higher than the secondary cooling intensity when the billet passes through the arc section and the straightening section.

8. The continuous casting process method according to any one of claims 1 to 3, characterized in that, Within the arc section before the straightening section, the secondary cooling intensity decreases uniformly along the billet pulling direction, while the billet shell thickness increases uniformly along the pulling direction.

9. The continuous casting process method according to any one of claims 1 to 8, characterized in that, After undergoing strong cooling treatment, the billet is directly fed into the heating furnace while hot, and the surface temperature of the billet is not lower than 500℃ during the hot feeding process.