A combined device of a mould nozzle for clean steel slab continuous casting

Abstract

This invention relates to a crystallizer nozzle assembly for clean steel slab continuous casting, comprising a nozzle body, a support, and a comb. The nozzle body has an annular slag-collecting groove on its inner wall. The nozzle body has baffles symmetrically arranged along the narrow side of the crystallizer. The support is located at the top of the crystallizer, and multiple combs are fixed to its bottom. The advantages are: controlling the fluctuation of the liquid level in the crystallizer, ensuring a stable liquid level, reducing the probability of slag entrapment, and thus ensuring smooth production and the metallurgical quality of the steel billet. The annular slag-collecting groove on the inner wall of the nozzle body allows inclusions in the high-temperature molten steel to deposit and stabilize at the groove location as it flows through. This solves the problem of unstable inclusions being washed away by subsequent steel flow and suddenly entering the molten steel, causing abrupt changes in the flow state and contamination of the molten steel.

Description

Technical Field

[0001] This invention belongs to the field of slab continuous casting technology and relates to a crystallizer nozzle assembly device for clean steel slab continuous casting. Background Technology

[0002] The ultra-cleanliness of high-grade steel is a major development direction for related products, and the control of inclusions in steel is a crucial aspect of the production process. However, non-metallic inclusions are unavoidable during steel production, especially in continuous casting. In the mold, molten steel and protective slag become entangled, and various slags trapped in the molten steel are captured and retained in the billet by the solidification front. These inclusions in the billet disrupt the continuity of the steel matrix, adversely affecting its load-bearing capacity, plasticity, impact toughness, and corrosion resistance. Therefore, optimizing the gating nozzle structure, controlling the flow of molten steel and the stability of the protective slag, and thereby improving the metallurgical level of the mold are extremely important.

[0003] Currently, slabs in continuous casting processes often use submerged entry nozzles, see Figure 1 , Figure 2 The molten steel is continuously and in a closed system transported from the tundish to the crystallizer. To ensure the smooth operation of the continuous casting process and the metallurgical quality of the cast billet, the flow state of the molten steel in the crystallizer must be properly controlled. Problems such as excessive free surface velocity, violent surface fluctuations, and poor flow symmetry will lead to the addition of protective slag into the molten steel and difficulty for inclusions to float to the surface within the crystallizer. In addition, nodules formed by inclusions deposited on the nozzle wall can suddenly enter the molten steel under the subsequent flow of steel, causing a rapid change in the flow resistance and resulting in a rapid change in the flow velocity and violent fluctuations in the crystallizer surface. This can lead to slag entanglement within the crystallizer and deteriorate the quality of the billet.

[0004] Achieving reasonable control of the flow field of molten steel in the crystallizer and effectively reducing inclusions in the billet is a technical challenge in continuous casting. Designing an immersion nozzle that can slow down the free surface flow, stabilize the liquid surface fluctuation, and temporarily store nodules is a way to achieve ultra-cleanliness of high-grade steel in high-speed casting. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a crystallizer nozzle assembly device for clean steel slab continuous casting. It utilizes annular slag storage grooves, baffles, and flow control structures such as pin combs on the inner wall of the nozzle to solve technical problems such as excessively fast surface flow of the free liquid surface in the crystallizer, uneven distribution of liquid slag, unstable nozzle nodule formation, and slag entrapment in the molten steel inside the crystallizer during high-speed continuous casting production, thereby achieving efficient metallurgy in the crystallizer.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A crystallizer nozzle assembly for clean steel slab continuous casting includes a nozzle body, a support, and a comb. The inner wall of the nozzle body is provided with an annular slag storage groove. The nozzle body is symmetrically provided with baffles along the narrow side of the crystallizer. The support is set at the top of the crystallizer, and multiple combs are fixed at the bottom of the support.

[0008] The main body of the water inlet has a cavity structure in the middle, and an inlet with a circular shape is provided at the top of the cavity structure; the lower part of the cavity structure has symmetrical side holes along the wide side of the crystallizer, and the cross-section of the side holes is a rectangle with rounded corners on all four sides, and the included angle between the axes of the two side holes is 140° to 160°; the bottom of the cavity structure is concave.

[0009] The water inlet body has a slag storage groove located 250-300mm above the side hole.

[0010] The bottom of the cavity structure is a conical structure.

[0011] The support is arranged along the wide side of the crystallizer and is located outside the water inlet body.

[0012] The depth of the slag storage groove is 130-170mm, and the slag storage groove has a structure that is wider at the top and narrower at the bottom.

[0013] The depth to which the comb is immersed in the molten steel is 100-150 mm.

[0014] The comb is made up of several alloy pins arranged in an alternating pattern, with 3 to 5 alloy pins in odd-numbered columns and 2 to 4 alloy pins in even-numbered columns. The alloy pins in odd-numbered columns have different lengths than those in even-numbered columns.

[0015] The diameter of the alloy nail is 8-20 mm.

[0016] The baffle and the sprue body are an integral structure.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] 1. This invention enables control of liquid level fluctuations in the crystallizer, ensures a stable liquid level, reduces the probability of slag entrapment, and thus ensures smooth production and the metallurgical quality of the steel billet.

[0019] 2. The present invention provides an annular slag storage groove on the inner wall of the nozzle body. When high-temperature molten steel flows through the nozzle body, the inclusions in the molten steel can be deposited and stabilized at the slag storage groove, thereby solving the problem of sudden changes in the flow state of the molten steel and contamination of the molten steel caused by unstable nodules being washed away and falling into the molten steel by the subsequent steel flow.

[0020] 3. The baffle design of the nozzle body along the narrow side of the crystallizer alleviates the problem of vortex formation and mixing of protective slag on the free liquid surface in the crystallizer due to poor flow symmetry.

[0021] 4. The nozzle body adopts a narrow and flat hole side outlet design to prevent the molten steel from directly impacting the narrow surface primary solidification shell due to excessive concentration, while improving the temperature uniformity inside the crystallizer.

[0022] 5. The pin comb plays a role in preventing slag entanglement. By designing the number, arrangement, and insertion depth of the alloy pins, the relative movement between slag and molten steel near the surface of the molten steel can be controlled, thus alleviating the slag entanglement caused by the backflow of molten steel and slag near the surface of the narrow face due to the excessively fast flow of the rising molten steel stream. Attached Figure Description

[0023] Figure 1 This is a front view of the principle of a conventional submersible sprue.

[0024] Figure 2 This is a top view of the principle of a conventional submersible sprue.

[0025] Figure 3 This is a schematic diagram of the structure of the present invention.

[0026] Figure 4 This is the front view of the sprue body.

[0027] Figure 5 This is a side view of the sprue body.

[0028] Figure 6 This is a top view of the present invention.

[0029] Figure 7 This is the main view of the principle of the present invention.

[0030] Figure 8 This is a top view illustrating the principle of the present invention.

[0031] In the diagram: 1-Sprue body 2-Support 3-Crystallizer 4-Pin comb 5-Slag storage groove 6-Side hole 7-Baffle. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0033] See Figures 3-8 A crystallizer nozzle assembly for clean steel slab continuous casting includes a nozzle body 1, a support 2, and a comb 4. The nozzle body 1 is arranged inside the crystallizer 3. The inner wall of the nozzle body 1 is provided with an annular slag storage groove 5. The nozzle body 1 is symmetrically provided with baffles 7 along the narrow side of the crystallizer 3. The support 2 is set on the top of the crystallizer 3, and multiple combs 4 are fixed at the bottom of the support 2.

[0034] The main body 1 has a cavity structure in the middle, with an inlet at the top. The inlet is circular with a diameter of 150-200 mm. The lower part of the cavity structure has symmetrical side holes 6 along the wide side of the crystallizer 3. The side holes 6 have a rectangular cross-section with rounded corners, a width of 60-100 mm, a length of 80-150 mm, and a corner radius of 10-20 mm.

[0035] The included angle between the axes of the two side holes 6 is 140° to 160°, and the two side holes 6 are inclined downwards, with a concave bottom at the bottom of the cavity structure. Preferably, the bottom of the cavity structure is a conical structure with a depth of 130 to 170 mm. This deep concave bottom structure can buffer and rebound the incoming flow during high-speed, high-flow-rate casting. The turbulence intensity is high and the energy dissipation is high at this position, which can reduce the velocity of the flow stream when it leaves the side holes 6 and reduce the direct scouring of the primary billet shell on the narrow face of the crystallizer 3 by the flow stream.

[0036] See Figure 4 , Figure 5 A slag-collecting groove 5 is provided 250-300mm above the side hole 6 inside the nozzle body 1. The depth of the slag-collecting groove 5 is 130-170mm, and the groove 5 has a structure that is wider at the top and narrower at the bottom. The bottom width of the slag-collecting groove 5 is 30-50mm, and the opening width at the bottom is 40-60mm. The slag-collecting groove 5 provides a location for inclusion deposition, thereby reducing the formation of unstable nodules on the nozzle wall. The design of the slag-collecting groove 5, which is wider at the top and narrower at the bottom, facilitates the deposition of inclusions and the periodic cleaning and removal of nodules after casting.

[0037] See Figure 1 The support 2 is set along the wide side of the crystallizer 3 and is located outside the water inlet body 1.

[0038] The comb 4 consists of several alloy nails arranged in staggered rows, with 3-5 alloy nails in odd-numbered rows and 2-4 alloy nails in even-numbered rows. The alloy nails in odd-numbered rows have different lengths than those in even-numbered rows. The diameter of the alloy nails is 8-20mm. The alloy nails can be TA1 titanium alloy nails or other high-temperature resistant alloys. The comb 4 is immersed in the molten steel to a depth of 100-150mm, which can be adjusted according to the actual casting conditions. The comb 4, composed of alloy nails, acts as an obstacle to fluid movement, slowing down the backflow of molten steel and slag mixing near the surface of the narrow face caused by the excessively rapid flow of the rising molten steel stream.

[0039] See Figure 4 , Figure 5 The baffle 7 and the nozzle body 1 are an integral structure. The baffle 7 is 30mm thick, 30-60mm long, and 80-160mm high. The baffle 7 is symmetrically fixed to the nozzle body 1 along the narrow side of the crystallizer 3, which can alleviate the generation of vortices near the free liquid surface of the nozzle body 1 caused by flow asymmetry, thereby reducing the entanglement of molten steel and protective slag caused by it.

[0040] The crystallizer nozzle assembly for clean steel slab continuous casting is suitable for slab continuous casting crystallizer 3 with a wide face range of 1900-2300mm and a narrow face range of 250-300mm. It is suitable for producing slabs (crystallizer 3 cross-section is 300mm×2300mm) under casting speed range of 0.8-1.2m / min.

[0041] Example:

[0042] See Figures 3-8 A sprue assembly for continuous casting of clean steel slabs includes a sprue body 1, a support 2, and a comb 4. The sprue body 1 is located inside the crystallizer 3. The central inlet hole of the sprue is 120mm. Near the bottom of the sprue body 1, on the wide side of the crystallizer 3, there are two side holes 6, each 60mm wide and 120mm long, with an included angle of 150° between their axes. A ring-shaped slag-collecting groove 5 is arranged 200mm above the side holes 6 on the inner wall of the sprue body 1. The groove 5 is 60mm deep, 30mm wide at its bottom, and 40mm wide at its opening. The bottom of the sprue is a conical concave bottom 100mm deep. Symmetrical baffles 7 are provided on both sides of the sprue body 1 along the narrow side of the crystallizer 3. Each baffle 7 is 30mm thick, 40mm long, and 300mm high, with 150±5mm protruding above the free liquid surface. The support 2 is placed and fixed on the upper edge of the cooling wall of the crystallizer 3 and is set on both sides of the outside of the water inlet body 1. Seven rows of TA1 titanium alloy nails with a diameter of 10mm are fixed below the support 2, with four odd-numbered rows and three even-numbered rows, arranged alternately. The nail comb 4 is immersed about 100mm below the liquid surface.

[0043] During continuous casting production, the depth of the nozzle body 1 inserted into the molten steel is 140-160 mm (distance from the center of the nozzle side hole 6 to the surface of the molten steel); the argon blowing rate is 6 ml / s; the casting temperature is 1580-1640℃; and the angle between the axis of the side hole 6 and the horizontal plane is 10°-20°.

[0044] See Figure 7 , Figure 8 The finite element numerical simulation results show that, compared with the conventional slab continuous casting nozzle, the slab continuous casting mold nozzle combination device with this structure has a slightly lower center position in the rising stream in the mold 3 due to the obstruction effect of the comb 4 on the flow of molten steel and protective slag. The maximum velocity of the rising stream near the narrow side of the mold 3 is reduced, and the maximum velocity on the free liquid surface is significantly reduced. There is a low-speed, high-pressure zone of fluid flow in the slag storage groove 5. The distance from the mainstream impact point to the free liquid surface remains basically unchanged. The local high temperature area is reduced, and the flow field symmetry is good. The impact stream disperses before reaching the narrow side of the mold 3, and the impact on the initial solidification shell is weak. The influence of the liquid surface fluctuation is evaluated according to the molten steel surface fluctuation index F in the mold 3 according to formula (1).

[0045] F = ρQL V e (1-sinθ) / 4D (1)

[0046] In equation (1): Q L The speed at which molten steel is drawn by volume, m 3 / s;V e ρ is the impact velocity of the main stream of molten steel, m / s; θ is the impact angle of the main stream of molten steel, °; D is the distance from the impact point to the free liquid surface, m; ρ is the density of molten steel, kg / m³. 3 .

[0047] Sampling and electron microscopy revealed that, compared with conventional slab continuous casting nozzles, the metallurgical quality of steel billets cast using this slab continuous casting crystallizer nozzle combination device was improved. No large oxide particles were found at the sampling locations, and the calcium, aluminum, and oxygen contents were reduced, with no flaw detection results indicating good performance.

[0048] Examples 1 to 7 are listed below. The specific casting process parameters and the structural parameters of the crystallizer 3 combination device are shown in Table 1. The numerical simulation results are shown in Table 2. The inclusions in the billet and rolled plate are shown in Appendix 3.

[0049] Examples 1 to 7 are listed below. The casting process parameters and the structural parameters of the crystallizer 3 assembly are shown in Table 1, the numerical simulation results are shown in Table 2, and the inclusions in the billet and rolled plate are shown in Table 3.

[0050] Table 1 Casting process parameters and structural parameters of the crystallizer assembly

[0051]

[0052] Table 2 Numerical simulation results

[0053]

[0054]

[0055] Table 3. Inclusions in cast billets and rolled plates

[0056]

[0057] This invention enables control of liquid level fluctuations in the crystallizer, ensures a stable liquid level, reduces the probability of slag entrapment, and thus guarantees smooth production and the metallurgical quality of steel billets.

[0058] Through the above specific embodiments, those skilled in the art can easily implement the present invention. However, it should be understood that the present invention is not limited to the specific embodiments described above. Based on the disclosed embodiments, those skilled in the art can arbitrarily combine different technical features to achieve different technical solutions. Due to space limitations and for the sake of brevity, each of these combined solutions has not been described in detail. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A crystallizer nozzle assembly for clean steel slab continuous casting, characterized in that, The system includes a sprue body, a support, and a comb. The inner wall of the sprue body is provided with an annular slag storage groove. The sprue body is symmetrically provided with baffles along the narrow side of the crystallizer. The support is set at the top of the crystallizer, and multiple combs are fixed at the bottom of the support. The main body of the water inlet has a cavity structure in the middle, and an inlet with a circular shape is provided at the top of the cavity structure; the lower part of the cavity structure has symmetrical side holes along the wide side of the crystallizer, and the cross-section of the side holes is a rectangle with rounded corners on all four sides, and the included angle between the axes of the two side holes is 140°~160°; the bottom of the cavity structure is concave. The water inlet body is provided with a slag storage groove 250-300mm above the side hole; The bottom of the cavity structure is a conical structure; The support is arranged along the wide side of the crystallizer and is located outside the nozzle body; The depth of the slag storage groove is 130~170mm, and the slag storage groove has a structure that is wider at the top and narrower at the bottom; The depth to which the comb is immersed in the molten steel is 100-150 mm; The comb is made up of several alloy pins arranged in an alternating pattern, with 3 to 5 alloy pins in odd-numbered columns and 2 to 4 alloy pins in even-numbered columns. The alloy pins in odd-numbered columns have different lengths than those in even-numbered columns.

2. The crystallizer nozzle assembly for clean steel slab continuous casting according to claim 1, characterized in that, The diameter of the alloy nail is 8-20 mm.

3. The crystallizer nozzle assembly for clean steel slab continuous casting according to claim 1, characterized in that, The baffle and the sprue body are an integral structure.

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