Crystallizer nozzle combination device for continuous casting of clean steel slab

Abstract

The crystallizer nozzle combination device comprises a nozzle body, a support and nail combs, an annular slag storage groove is formed in the inner wall of the nozzle body, baffles are symmetrically arranged on the nozzle body in the narrow edge direction of the crystallizer, the support is arranged on the top of the crystallizer, and the nail combs are fixed to the bottom of the support. The device has the advantages of controlling the liquid level fluctuation of the crystallizer, ensuring the stable liquid level, reducing the slag entrapment probability and further ensuring the smooth production and the metallurgical quality of steel billets. The annular slag storage groove is formed in the inner wall of the nozzle body, high-temperature molten steel flows through the nozzle body, inclusions in the molten steel can be deposited and stably nodulated at the position of the slag storage groove, and then the problems that due to the fact that unstable nodules are scoured by follow-up steel flow, fall off and suddenly enter the molten steel, the flowing state of the molten steel suddenly changes, and the molten steel is polluted are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of slab continuous casting and relates to a crystallizer water inlet assembly device used for clean steel slab continuous casting. Background Art

[0002] Ultra-cleaning of high-grade steel is the main development direction of related products, and the control technology of inclusions in steel is an important link in the production process. In the process of steel production, non-metallic inclusions are inevitable, especially in the continuous casting process, the molten steel and the protective slag in the crystallizer are mixed, and the various slags involved in the molten steel are captured by the solidification front and retained in the ingot. These inclusions in the billet destroy the continuity of the steel matrix and have an adverse effect on its bearing capacity, plasticity, impact toughness and corrosion resistance. Therefore, it is very important to optimize the pouring nozzle structure, control the flow of molten steel and the stability of protective slag, and then improve the metallurgical level of the crystallizer.

[0003] At present, submerged nozzles are often used in slab continuous casting processes. Figure 1 , Figure 2 , the molten steel is transported from the tundish to the crystallizer in a closed and continuous manner. In order to ensure the smooth progress of the continuous casting process and the metallurgical quality of the ingot, the flow state of the molten steel in the crystallizer must be reasonably controlled. If there are problems such as excessive free surface velocity, violent liquid level fluctuations, and flow symmetry, the flow of the molten steel is not good, which will lead to the addition of protective slag to the molten steel and the difficulty of inclusions floating in the crystallizer. In addition, the nodules formed by the deposition of inclusions on the wall of the water inlet suddenly enter the molten steel under the subsequent flushing of the steel flow, resulting in an instantaneous change in the resistance to the flow of the molten steel, causing a rapid change in the flow velocity of the molten steel and violent fluctuations in the crystallizer liquid level, thereby causing the slag to be mixed in the crystallizer and deteriorating the quality of the ingot.

[0004] How to reasonably control the flow field of molten steel in the crystallizer and effectively reduce inclusions in the billet is a technical challenge in the continuous casting process. Designing an immersion nozzle that can slow down the free liquid surface flow, stabilize liquid surface fluctuations, and temporarily store nodules is a way to achieve ultra-clean high-grade steel under high-speed casting. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a crystallizer water nozzle combination device for continuous casting of clean steel slabs, which utilizes flow control structures such as annular slag storage grooves on the inner wall of the water nozzle, baffles, and nail combs to solve technical problems such as excessively fast flow of the free liquid surface of the crystallizer, uneven distribution of liquid slag, unstable water nozzle nodules, and slag rolling of molten steel in the crystallizer that occur during high-speed continuous casting production, thereby achieving efficient metallurgy of the crystallizer.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A crystallizer nozzle assembly device for continuous casting of clean steel slabs comprises a nozzle body, a bracket, and a nail 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 direction of the crystallizer, the bracket is arranged on the top of the crystallizer, and a plurality of nail combs are fixed on the bottom of the bracket.

[0008] The middle of the nozzle body is a cavity structure, and an entrance is provided at the top of the cavity structure, which is circular; the lower part of the cavity structure is symmetrically provided with side holes along the wide side direction of the crystallizer, and the cross-section of the side holes is a rectangle with rounded corners on all sides, and the angle between the axes of the two side holes is 140° to 160°; the bottom of the cavity structure is a concave bottom.

[0009] A slag storage groove is provided in the nozzle body at 250 to 300 mm 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 outside the nozzle body.

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

[0013] The nail comb is immersed in the molten steel to a depth of 100 to 150 mm.

[0014] The nail comb is composed of a plurality of alloy nails arranged in rows and columns, wherein the odd-numbered rows have 3 to 5 alloy nails and the even-numbered rows have 2 to 4 alloy nails. The alloy nails in the odd-numbered rows are different in length from those in the even-numbered rows.

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

[0016] The baffle and the nozzle body are an integrated structure.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention can control the fluctuation of the liquid level in the crystallizer, ensure a stable liquid level, reduce the probability of slag rolling, and thus ensure smooth production and the metallurgical quality of the steel billet.

[0019] 2. The present invention sets an annular slag storage groove on the inner wall of the nozzle body. The high-temperature molten steel flows through the nozzle body, and the inclusions in the molten steel can be deposited and stably nodulated at the position of the slag storage groove, thereby solving the problem that the unstable nodules are washed off by the subsequent steel flow and suddenly enter the molten steel, causing the flow state of the molten steel to change suddenly and pollute the molten steel.

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

[0021] 4. The nozzle body adopts a narrow and long flat hole side outlet design to prevent the molten steel from directly impacting the narrow surface initial solidification shell too much, while improving the temperature uniformity in the crystallizer.

[0022] 5. The nail comb can prevent slag from rolling. The design of the number, arrangement and insertion depth of the alloy nails can control the relative movement of slag and molten steel near the surface of the molten steel, and alleviate the rolling of slag in the narrow surface near the surface caused by the rapid flow of the rising stream of molten steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the principle front view of a conventional submerged nozzle.

[0024] Figure 2 This is a top view of the principle of a conventional submerged nozzle.

[0025] Figure 3 It is a structural schematic diagram of the present invention.

[0026] Figure 4 This is the main view of the nozzle body.

[0027] Figure 5 It is a side view of the nozzle body.

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

[0029] Figure 7 It is the principle front view of the present invention.

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

[0031] In the figure: 1- nozzle body 2- bracket 3- crystallizer 4- nail comb 5- slag storage groove 6- side hole 7- baffle. DETAILED DESCRIPTION

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

[0033] See Figure 3-Figure 8 A crystallizer nozzle assembly device for continuous casting of clean steel slabs includes a nozzle body 1, a bracket 2, and a nail comb 4. The nozzle body 1 is arranged in a 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 direction of the crystallizer 3. The bracket 2 is arranged on the top of the crystallizer 3, and a plurality of nail combs 4 are fixed to the bottom of the bracket 2.

[0034] The middle of the nozzle body 1 is a cavity structure, and the top of the cavity structure is provided with an inlet, which is circular and has a diameter of 150-200 mm. The lower part of the cavity structure is symmetrically provided with side holes 6 along the wide side direction of the crystallizer 3, and the cross section of the side hole 6 is a rectangular with rounded corners on all sides, with a width of 60-100 mm, a length of 80-150 mm, and a fillet radius of 10-20 mm.

[0035] The axis angle of the two side holes 6 is 140° to 160°, and the two side holes 6 are inclined downward, and the bottom of the cavity structure is a concave bottom. Preferably, the bottom of the cavity structure is a conical structure with a depth of 130 to 170 mm. The use of this deep concave bottom structure can play a role in buffering and rebounding the incoming flow during high-speed and high-flow casting. At this position, the turbulence intensity is large and the energy dissipation is high, which can reduce the speed of the flow when leaving the side hole 6, and reduce the direct scouring of the flow on the primary shell of the narrow surface of the crystallizer 3.

[0036] See Figure 4 , Figure 5 A slag storage groove 5 is provided in the nozzle body 1 at 250 to 300 mm above the side hole 6. The depth of the slag storage groove 5 is 130 to 170 mm, and the slag storage groove 5 is a structure of being wide at the top and narrow at the bottom. The bottom width of the slag storage groove 5 is 30 to 50 mm, and the lower opening width of the slag storage groove 5 is 40 to 60 mm. The slag storage groove 5 provides a location for the deposition of inclusions, thereby reducing the formation of unstable nodules on the nozzle wall. The design of the slag storage groove 5 being wide at the top and narrow at the bottom is conducive to the deposition of inclusions and the regular cleaning and removal of nodules after the casting is completed.

[0037] See Figure 1 The support 2 is arranged along the wide side of the crystallizer 3 and outside the nozzle body 1.

[0038] The nail comb 4 is composed of a number of alloy nails arranged in rows and staggered, with 3 to 5 alloy nails in odd-numbered rows and 2 to 4 alloy nails in even-numbered rows. The lengths of the alloy nails in odd-numbered rows are different from those in even-numbered rows. The diameter of the alloy nails is 8 to 20 mm. The alloy nails can be TA1 titanium alloy nails or other high-temperature resistant alloys. The nail comb 4 is immersed in the molten steel liquid surface to a depth of 100 to 150 mm, and the depth can be adjusted according to the actual casting conditions. The anti-slag rolling nail comb 4 composed of alloy nails acts as an obstacle to fluid movement to slow down the slag rolling of the refluxed molten steel near the surface of the narrow surface caused by the excessively fast flow of the molten steel ascending stream.

[0039] See Figure 4 , Figure 5 The baffle 7 is an integrated structure with the nozzle body 1. The baffle 7 is 30 mm thick, 30 to 60 mm long, and 80 to 160 mm 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 mixing of molten steel and protective slag caused by it.

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

[0041] Example:

[0042] See Figure 3-Figure 8 The crystallizer nozzle assembly device for continuous casting of clean steel slabs comprises a nozzle body 1, a bracket 2, and a nail comb 4; the nozzle body 1 is arranged in the crystallizer 3, the nozzle steel liquid inlet center hole is 120mm, the nozzle body 1 has two side holes 6 near the bottom in the wide surface direction of the crystallizer 3, the width is 60mm, the length is 120mm, and the angle between the axis of the side holes 6 is 150°. The inner wall of the nozzle body 1 is arranged with an annular slag storage groove 5 200mm above the side hole 6, the slag storage groove 5 is 60mm deep, the bottom width of the slag storage groove 5 is 30mm, and the opening width of the slag storage groove 5 is 40mm. The bottom of the nozzle is a conical concave bottom with a depth of 100mm. The outside of the nozzle body 1 is symmetrically provided with baffles 7 on both sides along the narrow side direction of the crystallizer 3, the baffle 7 is 30mm thick, 40mm long, 300mm high, and the free liquid surface part is exposed 150±5mm. The bracket 2 is placed and fixed on the upper edge of the cooling wall of the crystallizer 3 and is arranged on both sides of the outside of the nozzle body 1. Seven rows of TA1 titanium alloy nails with a diameter of 10 mm are fixed under the bracket 2, with 4 in odd rows and 3 in even rows, arranged in a staggered manner, and the nail comb 4 is immersed about 100 mm below the liquid surface.

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

[0044] See Figure 7 , Figure 8 The results of finite element numerical simulation show that compared with the conventional slab continuous casting nozzle, the slab continuous casting crystallizer nozzle assembly device with this structure has a slightly lower center position of the rising flow in the crystallizer 3 due to the hindering effect of the nail comb 4 on the flow of molten steel in the protective slag, and the maximum velocity of the rising flow near the narrow surface of the crystallizer 3 is reduced, and the maximum velocity on the free liquid surface is greatly reduced; there is a low-speed and high-pressure area 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 is well symmetrical; the impact flow is dispersed before reaching the narrow side of the crystallizer 3, and the impact on the initial solidification shell is weak. According to formula (1), the liquid level fluctuation index F of the molten steel in the crystallizer 3 is used to evaluate the influence of the liquid level fluctuation:

[0045] F=ρQL V e (1-sinθ) / 4D (1)

[0046] In formula (1): Q L is the volume pulling speed of molten steel, m 3 / s; V e is the impact velocity of the mainstream of the molten steel, m / s; θ is the impact angle of the mainstream of the molten steel, °; D is the distance from the impact point to the free liquid surface, m; ρ is the density of the molten steel, kg / m 3 .

[0047] Through sampling detection and electron microscope observation, it was found that compared with the conventional slab continuous casting nozzle, the metallurgical quality of the steel billet cast by the slab continuous casting crystallizer nozzle combination device with this structure was improved, there was no large oxide size at the sampling position, the calcium, aluminum and oxygen contents were reduced, and the non-destructive testing results were good.

[0048] Embodiments 1 to 7 are listed below. The specific case casting process parameters and the structural parameters of the crystallizer 3 assembly device are shown in Table 1, the numerical simulation results are shown in Table 2, and the inclusion conditions in the ingot 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 device are shown in Table 1, the numerical simulation results are shown in Table 2, and the inclusions in the ingot and rolled plate are shown in Table 3.

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

[0051]

[0052] Table 2 Numerical simulation results

[0053]

[0054]

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

[0056]

[0057] The present invention can control the fluctuation of the liquid level in the crystallizer, ensure a stable liquid level, reduce the probability of slag rolling, and thus ensure smooth production and the metallurgical quality of the steel billet.

[0058] Through the above specific implementation, the technical personnel in the relevant technical field can easily implement the present invention. However, it should be understood that the present invention is not limited to the above specific implementation. On the basis of the disclosed implementation, the technical personnel in the relevant technical field can arbitrarily combine different technical features to achieve different technical solutions. Due to the limited space and to make the specification concise, the various solutions composed of these combinations are not described one by one. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A crystallizer nozzle assembly device for continuous casting of clean steel slabs, characterized in that: It includes a nozzle body, a bracket, and a nail 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 direction of the crystallizer, the bracket is arranged on the top of the crystallizer, and a plurality of nail combs are fixed at the bottom of the bracket.

2. A crystallizer nozzle assembly device for continuous casting of clean steel slabs according to claim 1, characterized in that: The middle of the nozzle body is a cavity structure, and an entrance is provided at the top of the cavity structure, which is circular; the lower part of the cavity structure is symmetrically provided with side holes along the wide side direction of the crystallizer, and the cross-section of the side holes is a rectangle with rounded corners on all sides, and the angle between the axes of the two side holes is 140° to 160°; the bottom of the cavity structure is a concave bottom.

3. The crystallizer nozzle assembly device for continuous casting of clean steel slabs according to claim 1, characterized in that: A slag storage groove is provided in the nozzle body at 250 to 300 mm above the side hole.

4. The crystallizer nozzle assembly device for continuous casting of clean steel slabs according to claim 1, characterized in that: The bottom of the cavity structure is a conical structure.

5. The crystallizer nozzle assembly device for continuous casting of clean steel slabs according to claim 1, characterized in that: The support is arranged along the wide side of the crystallizer and outside the nozzle body.

6. The crystallizer nozzle assembly device for continuous casting of clean steel slabs according to claim 1, characterized in that: The depth of the slag storage groove is 130-170 mm, and the slag storage groove is a structure that is wide at the top and narrow at the bottom.

7. The crystallizer nozzle assembly device for continuous casting of clean steel slabs according to claim 1, characterized in that: The nail comb is immersed in the molten steel to a depth of 100 to 150 mm.

8. The crystallizer nozzle assembly device for continuous casting of clean steel slabs according to claim 1, characterized in that: The nail comb is composed of a plurality of alloy nails arranged in rows and columns, wherein the odd-numbered columns have 3 to 5 alloy nails and the even-numbered columns have 2 to 4 alloy nails. The alloy nails in the odd-numbered columns are different in length from those in the even-numbered columns.

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

10. The crystallizer nozzle assembly device for continuous casting of clean steel slabs according to claim 1, characterized in that: The baffle and the nozzle body are an integrated structure.

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