A continuous casting method combining a structure and a process of a mold submerged entry nozzle

Abstract

This invention discloses a continuous casting method combining a crystallizer immersion nozzle structure and process. 1) For low-carbon and ultra-low-carbon steel grades: the steel throughput is 3.5–5.5 t / min, and the maximum inner diameter of the matching nozzle is φ80 mm; the nozzle outlet angle is downward 15–30°; the ratio of the nozzle outlet side hole area to the center hole area S 侧 / S 内 =2.0~3.0; The bottom of the nozzle adopts a concave design, with a depth of 10~12mm; The thickness of the nozzle wall is 27~30mm; The insertion depth of the nozzle is 150mm~250mm; The total argon blowing rate of the stopper rod + upper nozzle is 5l / min~15l / min; 2) For high carbon and low alloy steel grades: the steel throughput is 1.5~3.5t / min, and the maximum inner diameter of the matching nozzle is φ70mm; The outlet inclination angle of the submersible nozzle is 10~15° upward or 15~20° downward; The ratio of the outlet side hole area to the center hole area of ​​the nozzle S 侧 / S 内 =1.0~2.0. This method can effectively control the entrapment of protective slag and bubbles in the crystallizer, promote the aggregation and growth of inclusions and their floating, and prevent uneven growth of the solidified shell.

Description

Technical Field

[0001] This invention relates to a continuous casting method, and more particularly to a continuous casting method that combines a crystallizer immersion nozzle structure and process. Background Technology

[0002] The flow state of molten steel within the mold has a significant impact on slag entrainment, inclusion capture by the protective slag, and the formation of cracks in the cast billet. Therefore, the mold is the final link in controlling the cleanliness of molten steel. Approximately 80% of surface and subsurface defects are generated within the mold. The design of the submerged entry nozzle parameters is a crucial factor affecting the molten steel flow rate in the mold. Optimizing the shape of the submerged entry nozzle allows for control of the molten steel flow field parameters. To achieve the optimal flow rate under every continuous casting condition, the dimensions, outlet angle, bottom shape, and immersion depth of the submerged entry nozzle must be determined.

[0003] Therefore, the surface quality of the cast billet largely depends on the flow field and free surface characteristics within the mold. Optimizing the parameters of the submerged entry nozzle to obtain reasonable molten steel flow field and free surface characteristics is an economical and efficient approach. An unreasonable submerged entry nozzle structure design can lead to asymmetrical and unstable flow field in the mold. This asymmetrical flow field results in non-uniform growth of the solidified billet shell and violent fluctuations in the liquid surface, which in turn causes the entrapment of protective slag, forming inclusion defects and affecting the surface quality of the final product. Furthermore, an unreasonable nozzle structure can also affect the surface velocity of the liquid surface in the mold. Excessive surface velocity will shear and entrain liquid or solid protective slag into the molten steel. These protective slag particles are large and irregularly shaped, leading to linear defects in the final rolled plate. Conversely, insufficient surface velocity results in excessively low temperatures at the meniscus of the mold, affecting the melting of the protective slag and thus its lubrication effect between the copper plate and the billet shell, causing surface defects in the cast billet and potentially leading to leaks. Especially for ultra-low carbon automotive panel steel, the lower surface flow rate can lead to excessive growth of the meniscus solidification groove structure, which aggravates the capture of floating inclusions, bubbles and slag, resulting in the deterioration of the surface cleanliness of the billet. In severe cases, the surface cleanliness of the billet can only be improved by flame cleaning, which will seriously affect the steel production.

[0004] Therefore, in actual continuous casting production, how to control the optimal molten steel flow field in the crystallizer under different conditions through scientific and reasonable submerged entry nozzle parameter design, based on the different process quality requirements of different steel grades and the different main contradictions of crystallizer flow field and quality control, is of great significance for preventing the entrapment of protective slag and bubbles, promoting the aggregation and growth of inclusions and floating, and preventing uneven growth of solidified billet shell. It is also a key technical problem that metallurgical technicians are researching and focusing on. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a continuous casting method that combines the structure and process of immersion nozzle in the crystallizer to improve the quality of the cast billet.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: 1) For low-carbon and ultra-low-carbon steel grades: the steel throughput is 3.5 to 5.5 t / min, and the maximum inner diameter of the matching nozzle is φ80 mm; the outlet inclination angle of the nozzle is downward 15 to 30°; the ratio of the area of ​​the outlet side hole to the area of ​​the center hole of the nozzle is S 侧 / S 内 =2.0~3.0; The bottom of the sprue adopts a concave design, with a depth of 10~12mm; The thickness of the sprue wall is 27~30mm;

[0007] The insertion depth of the water inlet is 150mm to 210mm; the total argon blowing rate of the stopper rod and the upper water inlet is 5l / min to 15l / min;

[0008] 2) For high-carbon and low-alloy steel grades: throughput 1.5–3.5 t / min, with a maximum matching nozzle inner diameter of φ70 mm; the outlet inclination angle of the submerged nozzle is 10–15° upwards or 15–20° downwards; the ratio S of the outlet side hole area to the center hole area of ​​the nozzle... 侧 / S 内 =1.0~2.0; The bottom of the sprue adopts a concave design, with a depth of 10~12mm; The thickness of the sprue wall is 27~30mm;

[0009] The insertion depth of the water inlet is 110mm to 150mm; the total argon blowing rate of the stopper rod and the upper water inlet is 7l / min to 15l / min.

[0010] Furthermore, in step 1), the total argon blowing rate of the stopper rod and the upper water inlet is 5 l / min to 10 l / min.

[0011] Furthermore, in step 1), the bottom of the sprue adopts a large wave-shaped concave bottom design.

[0012] Furthermore, in step 2), the bottom of the sprue adopts a large wave-shaped concave bottom design.

[0013] The beneficial effects of adopting the above technical solution are as follows: This invention, through an economical and efficient approach of optimizing the submerged nozzle structure design and process parameters, obtains reasonable molten steel flow field (double reflux) and free liquid surface characteristics (symmetric and stable) under different conditions based on the different process quality requirements of different steel grades and the different main contradictions between the flow field and quality control of the crystallizer. This effectively controls the entrainment of protective slag and bubbles in the crystallizer, promotes the aggregation, growth and floating of inclusions, and prevents uneven growth of the solidified billet shell. Thus, it ensures both the quality of the cast billet and the smooth operation of continuous casting production, improves quality, reduces accidents, and reduces costs and increases efficiency. Attached Figure Description

[0014] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0015] Figure 1 This is a schematic diagram of the dual reflux crystallizer described in this invention;

[0016] Figure 2 This is a schematic diagram of the immersion-type water inlet structure described in this invention.

[0017] In the diagram: 1. Sprue 1; 2. Sprue wall; 3. Bottom of sprue 3; 4. Outlet side hole; φ. Inner diameter of sprue; D. Thickness of sprue wall; α. Outlet inclination angle of sprue. Detailed Implementation

[0018] Figure 1 As shown, during the steel casting process, the molten steel in the crystallizer, under the impact of the pouring flow, splits into two reflux zones along the stream. The upper reflux zone flows upward along the side wall of the crystallizer to near the molten steel surface and then towards the nozzle. The lower reflux zone, after impacting the side wall of the crystallizer, is pushed downward to a certain depth by inertia and then flows upward along the center of the crystallizer to near the nozzle. During this flow process, the impact force on the side wall of the crystallizer significantly affects the uniformity of the billet shell on the side wall and the magnitude of the upper and lower reflux velocities. An increase in the upper reflux velocity directly affects the stability of the molten steel surface in the crystallizer and the size of the vortex generated by the interaction of the refluxes on both sides of the nozzle. The molten steel surface in the crystallizer fluctuates due to the reflux. If the fluctuation is too small, it will affect the dissolution and diffusion of inclusions in the steel into the slag; if the fluctuation is too large, it will cause slag to be entrained into the steel, affecting the quality of the steel.

[0019] Based on the above theory, the continuous casting method combining the submerged entry nozzle structure and process of the crystallizer adopts the following structure and process:

[0020] 1. The submerged nozzle adopts a structural design and process method with a large inner diameter and deep insertion to reduce the upper backflow and enhance the lower backflow. This method is suitable for low carbon and ultra-low carbon steel grades, such as SPHC and IF steel, where the main problem is the control of nozzle 1 blockage and inclusions.

[0021] 1) Large inner diameter:

[0022] ① Reasonable matching of the inner diameter φ of the sprue and the steel flow rate: the steel flow rate is 3.5~5.5t / min, and the matching inner diameter of the sprue φ≤80mm, preferably 70mm≤φ≤80mm;

[0023] While a large-diameter submersible nozzle can reduce clogging at nozzle 1, it can also cause molten steel flow deviation when the steel cleanliness is poor and the steel throughput is low (small cross-section, low casting speed). This leads to an asymmetrical and unstable flow field in the crystallizer, resulting in mold flux entrapment defects. In this case, the "slag entrapment" on the surface of the continuously cast billet is not due to large fluctuations in the crystallizer level during casting, but rather to unstable steel flow. Unstable steel flow causes localized vortices in the middle of the wide face of the crystallizer, which entrap mold flux, forming a "slag entrapment" defect. If the vortex collides with the steel flow stream from the side outlet, the mold flux drawn in by the vortex will be impacted by the stream to a deeper position in the crystallizer, thus forming a large-scale "slag entrapment" defect. Therefore, the large inner diameter of nozzle 1 is relative; the nozzle inner diameter must match the actual steel throughput, i.e., the continuous casting machine speed and the billet cross-section.

[0024] ② The outlet angle α of water inlet 1 is downward 15-30°;

[0025] ③ The ratio S of the area of ​​the outlet side hole of water inlet 1 to the area of ​​the center hole 侧 / S 内 =2.0~3.0, and matches the outlet angle and shape; since the water inlet generally has two outlet side holes, this area ratio is the ratio of the sum of the areas of the two outlet side holes to the area of ​​the central hole, i.e., S 侧 S is the sum of the areas of the two outlet side holes of the sluice gate. 内 It is the cross-sectional area of ​​the inner diameter of the sluice gate;

[0026] ④ The bottom of the nozzle 3 adopts a concave design, with a depth of 10-12mm, preferably a large wave-shaped concave bottom. This is because when using a submerged entry nozzle with a concave bottom, the molten steel stream is buffered within the groove at the bottom, reducing turbulent kinetic energy. The velocity of the molten steel flowing out from the side of the nozzle is smaller, thus reducing the kinetic energy of the stream. The liquid surface in the crystallizer is more stable than when using a convex bottom submerged entry nozzle. Moreover, the wave-shaped concave bottom of the nozzle can effectively dissipate the molten steel flow velocity, suppressing high-speed molten steel from directly rushing out of the nozzle. The jet shape is more divergent, which is conducive to the floating and removal of inclusions. At the same time, it reduces the impact depth of the jet in the crystallizer, reduces the surface velocity of the crystallizer, and reduces the fluctuation of the molten steel surface in the crystallizer.

[0027] ⑤ The thickness of the nozzle wall 2, D = 27-30 mm; although increasing the thickness of the nozzle wall can enhance the nozzle's resistance to thermal shock and corrosion, it also reduces the distance between the outer wall of the nozzle and the copper plate of the crystallizer, which is not conducive to slag formation; the increase in wall thickness will lead to an increase in the impact depth of the flow stream, causing the thermal center of the molten steel to move downward and the speed at which the molten steel impacts the narrow edge of the crystallizer to increase, which is not conducive to the melting of the protective slag, and will increase the adhesion and cracking rate.

[0028] 2) Deep insertion:

[0029] ① The insertion depth of sprue 1 is 150-210mm;

[0030] ② The total argon blowing rate of the stopper rod and the upper water inlet is 5-15 l / min; for steel grades with extremely high surface quality requirements, such as automotive panels and electroplated bright plates, the total argon blowing rate of the stopper rod and the upper water inlet is 5-10 l / min.

[0031] ③ The surface velocity of molten steel in the crystallizer is 0.25~0.33m / s (1 / 4 position), and the velocity difference between the two sides inside the crystallizer is ≤0.05m / s; maintain the symmetrical and stable flow field of molten steel in the crystallizer and reduce the probability of slag entrainment in the molten steel;

[0032] ④ Improve the cleanliness of molten steel and control the total oxygen content (TO) of molten steel in the tundish to ≤20ppm; a low total oxygen content in molten steel in the tundish indicates high cleanliness, which helps to reduce nozzle blockage and the resulting asymmetric and unstable flow field caused by the molten steel flow deviation in the crystallizer.

[0033] 2. The submerged nozzle adopts a structural design and process method with a small inner diameter and shallow insertion to enhance the upper backflow and weaken the lower backflow. This method is suitable for high carbon and low alloy steels, such as high carbon steel, silicon steel, and stainless steel, where the main contradiction is the melting of protective slag and the control of surface defects.

[0034] 1) Small inner diameter:

[0035] ① Reasonable matching of nozzle inner diameter and steel throughput: The maximum steel throughput is 1.5~3.5t / min, and the matching nozzle inner diameter is φ70mm at most, and preferably 60mm≤φ≤70mm;

[0036] ② The outlet inclination angle α of the submersible nozzle is 10-15° upward or 15-20° downward;

[0037] ③ The ratio S of the area of ​​the outlet side hole to the area of ​​the center hole of water inlet 1 侧 / S 内 ==1.0~2.0, and matched with the outlet angle and shape; because reducing the size of the outlet side hole 4 is beneficial to increasing the center wave height of the crystallizer, which in turn is beneficial to stabilizing the flow field of the crystallizer. The principle is: under the condition that the inner diameter of the inlet hole of the submersible nozzle remains unchanged, reducing the area of ​​the side hole is beneficial to increasing the average velocity of the outlet flow stream of the outlet side hole 4, reducing the possibility of "backflow vortex" generated at the top of the outlet side hole 4, and is beneficial to improving the uniformity of the steel flow on both sides of the outlet side hole 4, making the flow field of the crystallizer more uniform;

[0038] ④ The bottom of the sprue 3 adopts a concave design, with a depth of 10-12mm, among which a large wave-shaped concave bottom is the best;

[0039] ⑤ The thickness of the sprue wall 2 is D = 27~30mm.

[0040] 2) Shallow insertion:

[0041] ① The insertion depth of sprue 1 is 110-150mm;

[0042] ② The total argon blowing rate of the stopper rod and the water inlet is 7-15 l / min.

[0043] Example 1: The continuous casting method combining the crystallizer immersion nozzle structure and process adopts the following specific structure and process.

[0044] A fully automated steel plant uses a 1650 continuous casting machine and a 2050 hot rolling mill to produce plates and hot coils. When producing low-carbon and ultra-low-carbon steel grades, such as SPHC and IF steel, where the main challenges are controlling nozzle blockage and inclusions:

[0045] (1) The submersible nozzle structure selected is as follows:

[0046] The inner diameter of the sprue is φ80mm, and the steel throughput is 3.5~5.5t / min; the side opening of the sprue is rectangular, with a length of 90mm and a width of 70mm. The calculated ratio S of the area of ​​the side opening to the area of ​​the center opening is... 侧 / S 内 =2.2; the outlet angle is 30° downward; the bottom of the outlet adopts a large wave-shaped concave bottom with a depth of 12mm; the thickness of the outlet wall is 30mm.

[0047] (2) The process parameters for the sprue used are as follows:

[0048] Insertion depth 160-210mm, with a fixed insertion depth of 180mm for IF steel used in automotive panels; total argon blowing rate of stopper rod + top nozzle: 5-15 l / min for low carbon steel, 5-10 l / min for IF steel; when producing high surface finish steels such as IF steel for automotive panels, control the surface flow velocity of molten steel in the crystallizer to 0.25-0.33 m / s (1 / 4 position), and the velocity difference between the two sides of the crystallizer ≤0.05 m / s; molten steel undergoes RH vacuum treatment, and the total oxygen content (TO) of the molten steel in the tundish is ≤20 ppm.

[0049] (3) Production performance:

[0050] Number of tundish castings: 14 heats for low carbon steel SPHC and 8 heats for IF steel; Degradation rate of slag inclusions (impurities) defects in hot-rolled and cold-rolled steel: ≤1.5% for low carbon steel SPHC and ≤2.7% for IF steel.

[0051] Example 2: The continuous casting method combining the immersion nozzle structure and process of the crystallizer adopts the following specific structure and process.

[0052] A fully automated steel plant uses a 1650 continuous casting machine and a 2050 hot rolling mill to produce plates and hot coils. When producing low-carbon and ultra-low-carbon steel grades, such as tinplate and IF steel, where the main challenges are controlling nozzle blockage and inclusions:

[0053] (1) The submersible nozzle structure selected is as follows:

[0054] The inner diameter of the sprue is φ70mm, and the steel throughput is 3.5~4.5t / min; the ratio of the area of ​​the outlet side hole to the area of ​​the center hole is S. 侧 / S 内 =2.0; the outlet angle is 15° downward; the bottom of the outlet adopts a large wave-shaped concave bottom with a depth of 11mm; the thickness of the outlet wall is 27mm.

[0055] (2) The process parameters for the sprue used are as follows:

[0056] Insertion depth 150-210mm, with a fixed insertion depth of 180mm for IF steel used in automotive panels; total argon blowing rate of stopper rod + top nozzle: 5-15 l / min for low carbon steel, 5-10 l / min for IF steel; when producing high surface finish steels such as IF steel for automotive panels, control the surface flow velocity of molten steel in the crystallizer to 0.28-0.33 m / s (1 / 4 position), and the velocity difference between the two sides of the crystallizer ≤0.05 m / s; molten steel undergoes RH vacuum treatment, and the total oxygen content (TO) of the molten steel in the tundish is ≤18 ppm.

[0057] (3) Production performance:

[0058] Number of tundish castings in tundish: 12 heats for low carbon steel tinplate, 8 heats for IF steel, etc.; Degradation rate of slag inclusion (impurity) defects in hot-rolled and cold-rolled steel: ≤1.2% for low carbon steel tinplate, etc., ≤2.5% for IF steel, etc.

[0059] Example 3: The continuous casting method combining the crystallizer immersion nozzle structure and process adopts the following specific structure and process.

[0060] A fully automated steel plant uses a 1650 continuous casting machine and a 2050 hot rolling mill to produce plates and hot coils. When producing low-carbon and ultra-low-carbon steel grades, such as SPHC and IF steel, where the main challenges are controlling nozzle blockage and inclusions:

[0061] (1) The submersible nozzle structure selected is as follows:

[0062] The inner diameter of the sprue is φ76mm, and the steel throughput is 4.5~5.5t / min; the ratio of the area of ​​the sprue outlet side hole to the area of ​​the center hole is S. 侧 / S 内 =3.0; the outlet angle is 30° downward; the bottom of the outlet adopts a large wave-shaped concave bottom with a depth of 10mm; the thickness of the outlet wall is 28mm.

[0063] (2) The process parameters for the sprue used are as follows:

[0064] Insertion depth 200-250mm, with a fixed insertion depth of 200mm for IF steel used in automotive panels; total argon blowing rate of stopper rod + top water inlet: 5-10 l / min for low carbon steel, 5-10 l / min for IF steel; when producing high surface finish steels such as IF steel for automotive panels, control the surface flow velocity of molten steel in the crystallizer to 0.25-0.30 m / s (1 / 4 position), and the velocity difference between the two sides inside the crystallizer ≤0.04 m / s; molten steel undergoes RH vacuum treatment, and the total oxygen content (TO) of the molten steel in the tundish is ≤20 ppm.

[0065] (3) Production performance:

[0066] Number of tundish castings: 16 heats for low carbon steel SPHC and 8 heats for IF steel; Degradation rate of inclusions (impurities) defects in hot-rolled and cold-rolled steel: ≤1.0% for low carbon steel SPHC and ≤2.0% for IF steel.

[0067] Example 4: The continuous casting method combining the crystallizer immersion nozzle structure and process adopts the following specific structure and process.

[0068] A fully integrated steel plant uses a 1650 continuous casting machine and a 2050 hot rolling mill to produce plates and hot-rolled coils. When producing high-carbon and low-alloy steels, such as 45Mn, W780QX, and HC980FG, which are high-carbon, duplex, and hot-formable high-strength low-alloy steels, the main challenges are controlling the melting of the protective slag and surface defects.

[0069] (1) The submersible nozzle structure selected is as follows:

[0070] The inner diameter of the sprue is φ70mm, and the steel throughput is 2.5~3.5t / min; the side opening of the sprue is rectangular, with a length of 70mm and a width of 50mm. The calculated ratio S of the area of ​​the side opening to the area of ​​the center opening is... 侧 / S 内 =1.27; the outlet angle is 15° downward; the bottom of the outlet adopts a large wave-shaped concave bottom with a depth of 12mm; the thickness of the outlet wall is 28.5mm.

[0071] (2) The process parameters for the sprue used are as follows:

[0072] Insertion depth: 110-150 mm; Total argon blowing rate of stopper rod + water inlet: 7-15 L / min.

[0073] (3) Production performance:

[0074] Six heats were cast in the tundish; the surface quality of the billet was good, with no cracks or dents; there were no warnings of sticking or leakage accidents.

[0075] Example 5: The continuous casting method combining the crystallizer immersion nozzle structure and process adopts the following specific structure and process.

[0076] A fully automated steel plant uses a 1650 continuous casting machine and a 2050 hot rolling mill to produce plates and hot-rolled coils; the main challenges in producing ferritic stainless steel, such as 409L, are controlling the melting of protective slag and surface defects.

[0077] (1) The submersible nozzle structure selected is as follows:

[0078] The inner diameter of the sprue is φ60mm, and the steel throughput is 1.5~2.5t / min; the side opening of the sprue is rectangular, with a length of 70mm and a width of 48mm. The calculated ratio S of the area of ​​the side opening to the area of ​​the center opening is... 侧 / S 内 =1.62; the outlet angle is 5° upward; the bottom of the outlet adopts a large wave-shaped concave bottom with a depth of 12mm; the thickness of the outlet wall is 28.5mm.

[0079] (2) The process parameters for the sprue used are as follows:

[0080] Insertion depth: 120-150 mm; Total argon blowing rate of stopper rod + upper water inlet: 7-15 L / min;

[0081] (3) Production performance:

[0082] Six heats were cast in the tundish; the surface quality of the billet was good, with no cracks or dents; there were no warnings of sticking or leakage accidents.

[0083] Example 6: The continuous casting method combining the immersion nozzle structure and process of the crystallizer adopts the following specific structure and process.

[0084] A fully integrated steel plant uses a 1650 continuous casting machine and a 2050 hot rolling mill to produce plates and hot-rolled coils. When producing high-carbon and low-alloy steels, such as 45Mn, W780QX, and HC980FG, which are high-carbon, duplex, and hot-formable high-strength low-alloy steels, the main challenges are controlling the melting of the protective slag and surface defects.

[0085] (1) The submersible nozzle structure selected is as follows:

[0086] The inner diameter of the sprue is φ70mm, and the steel throughput is 2.5~3.5t / min; the ratio of the area of ​​the outlet side hole to the area of ​​the center hole is S. 侧 / S 内 =2.0; the outlet angle is 20° downward; the bottom of the outlet adopts a large wave-shaped concave bottom with a depth of 11mm; the thickness of the outlet wall is 27mm.

[0087] (2) The process parameters for the sprue used are as follows:

[0088] Insertion depth: 110-150 mm; Total argon blowing rate of stopper rod + water inlet: 7-12 l / min.

[0089] (3) Production performance:

[0090] There were 12 heats of continuous casting in the tundish; the surface quality of the billet was good, with no cracks or dents; there were no warnings of sticking or leakage accidents.

[0091] Example 7: The continuous casting method combining the crystallizer immersion nozzle structure and process adopts the following specific structure and process.

[0092] A fully automated steel plant uses a 1650 continuous casting machine and a 2050 hot rolling mill to produce plates and hot-rolled coils; the main challenges in producing ferritic stainless steel, such as 430L, are controlling the melting of the protective slag and surface defects.

[0093] (1) The submersible nozzle structure selected is as follows:

[0094] The inner diameter of the sprue is φ62mm, and the steel throughput is 1.5~2.5t / min; the ratio of the area of ​​the sprue outlet side hole to the area of ​​the center hole is S. 侧 / S 内 =1.0; the outlet angle is 15° upward; the bottom of the outlet adopts a large wave-shaped concave bottom with a depth of 10mm; the thickness of the outlet wall is 30mm.

[0095] (2) The process parameters for the sprue used are as follows:

[0096] Insertion depth: 110-140 mm; Total argon blowing rate of stopper rod + upper water inlet: 10-15 L / min;

[0097] (3) Production performance:

[0098] Five heats were cast in the tundish; the surface quality of the billet was good, with no cracks or dents; there were no warnings of sticking or leakage accidents.

Claims

1. A continuous casting method combining a crystallizer immersion nozzle structure and process, characterized in that: 1) For low-carbon and ultra-low-carbon steel grades: throughput 3.5–5.5 t / min, with a maximum matching nozzle inner diameter of φ80 mm; nozzle outlet inclination angle downwards 15–30°; the ratio S of the nozzle outlet side hole area to the center hole area... 侧 / S 内 =2.0~3.0; The bottom of the sprue adopts a concave design, with a depth of 10~12mm; The thickness of the sprue wall is 27~30mm; The insertion depth of the nozzle is 150mm to 210mm; the total argon blowing rate of the stopper rod and the upper nozzle is 5l / min to 15l / min; the bottom of the nozzle adopts a large wave-shaped concave bottom design; 2) For high-carbon and low-alloy steel grades: throughput 1.5–3.5 t / min, with a maximum matching nozzle inner diameter of φ70 mm; the outlet angle of the submersible nozzle is 10–15° upwards or 15–20° downwards; the ratio S of the outlet side hole area to the center hole area of ​​the nozzle... 侧 / S 内 =1.0~2.0; The bottom of the sprue adopts a concave design, with a depth of 10~12mm; The thickness of the sprue wall is 27~30mm; The insertion depth of the nozzle is 110mm to 150mm; the total argon blowing rate of the stopper rod and the upper nozzle is 7l / min to 15l / min; the bottom of the nozzle adopts a large wave-shaped concave bottom design.

2. The continuous casting method combining a crystallizer immersion nozzle structure and process according to claim 1, characterized in that: In step 1), the total argon blowing rate of the stopper rod and the upper water inlet is 5 l / min to 10 l / min.

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