A submerged entry nozzle and method for improving billet quality

Abstract

This invention relates to the field of submerged entry nozzle technology, specifically to a submerged entry nozzle and method for improving the quality of cast billets. It includes a submerged entry nozzle and an argon blowing system; the main body of the submerged entry nozzle is a long cylinder open at the top and closed at the bottom; the lower part of the main body has an upper outlet and a lower outlet; the upper outlet is inclined upwards, and the lower outlet is inclined downwards, with the upper outlet located above the lower outlet; the argon blowing system includes an inlet pipe, a lower connecting pipe, and an outlet pipe; the inlet pipe is connected to an argon gas pipeline, extending into the upper part of the side wall of the main body; the lower connecting pipe is vertically installed on the side wall of the main body, with its top connected to the inlet pipe, its bottom located at the upper outlet, and its bottom connected to the outlet pipe; argon gas enters through the inlet pipe, passes through the lower connecting pipe, and is ejected through the outlet pipe. This significantly improves the quality of the cast billets.

Description

Technical Field

[0001] This invention relates to the field of submerged entry nozzle technology, specifically to a submerged entry nozzle and method for improving the quality of cast billets. Background Technology

[0002] During continuous steel casting, eddies frequently form on the surface of the molten steel in the crystallizer, which entrain the protective slag covering the surface into the molten steel. This is called "eddy slag entrainment." The entrained protective slag remains in the billet, forming large particle inclusions, which lead to various inclusion defects in the rolled product. For example, surface defects in thin plates used for automotive panels, and flaw detection defects in thick plates used for shipbuilding, bridges, and containers, etc., which can result in the scrapping of steel and cause significant economic losses.

[0003] Currently, the "slag entrainment" problem can only be controlled by adjusting the outlet angle of the submerged entry nozzle, the argon blowing volume, and stabilizing the steel pouring flow, but the results are not ideal. It can be said that there is still no truly effective method to solve the "slag entrainment" problem. Furthermore, unstable flow causing liquid level fluctuations can lead to slag inclusions on the surface of the billet. The impact of the flow stream on the billet shell also causes uneven shell thickness, leading to defects such as longitudinal cracks in the billet.

[0004] Chinese patent document CN201644781U discloses "A crystallizer immersion nozzle for preventing slag entrapment in continuously cast slabs." While it overcomes the problems of large liquid surface fluctuations and excessively high surface flow velocities caused by unreasonable size and orifice shape of the crystallizer immersion nozzle during continuous casting, effectively preventing the entrapment of protective slag and reducing defects such as slag entrapment and inclusions on the slab surface, it suffers from the problem of excessive downward impact of the molten steel flowing out of the immersion nozzle, resulting in low molten steel surface temperature in the crystallizer and poor melting of the protective slag, thus affecting the quality of the continuously cast slab. Chinese patent document CN101219464 discloses "A continuous casting crystallizer device capable of controlling the liquid surface flow field and fluctuations." While it can reduce and suppress slag entrapment in the crystallizer, thereby improving the quality of the continuously cast slab, it suffers from the problem of carrying protective slag into the molten steel and hindering the flow of protective slag due to the consumption of metal plates. Furthermore, its complex mechanism increases the difficulty of operation and production costs, making it unsuitable for demand. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides an immersion nozzle and method for improving the quality of cast billets, which can significantly improve the quality of cast billets.

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

[0007] A submerged entry nozzle for improving billet quality includes a submerged entry nozzle and an argon blowing system. The submerged entry nozzle body is a long cylinder with an open top and a closed bottom. The lower part of the body is provided with an upper outlet and a lower outlet. The upper outlet is inclined upwards, and the lower outlet is inclined downwards, with the upper outlet located above the lower outlet. The argon blowing system includes an inlet pipe, a lower through pipe, and an outlet pipe. The inlet pipe is connected to an argon gas pipeline and extends into the upper part of the side wall of the body. The lower through pipe is vertically installed on the side wall of the body, with its top connected to the inlet pipe and its bottom located at the upper outlet. The bottom of the lower through pipe is connected to the outlet pipe. Argon gas enters through the inlet pipe, passes through the lower through pipe, and is ejected through the outlet pipe.

[0008] Furthermore, the angle between the upper outlet and the axis of the main body is α, where 50°≤α≤80°;

[0009] Furthermore, the angle between the lower outlet and the axis of the main body is β, where 55°≤β≤85°.

[0010] Furthermore, the distance between the upper outlet and the lower outlet is S, where 50mm ≤ α ≤ 150mm.

[0011] Furthermore, the upper outlet has two holes that are symmetrically arranged on the left and right.

[0012] Furthermore, the lower outlet has two holes that are symmetrically arranged on the left and right.

[0013] Furthermore, the immersion nozzle is installed on the tundish.

[0014] Furthermore, the upper part of the body is trumpet-shaped, and the lower part is cylindrical.

[0015] A method for improving the quality of cast billets, based on the aforementioned submerged entry nozzle for improving cast billet quality, specifically includes the following steps:

[0016] 1) Bake the immersion sprue before use;

[0017] 2) Install the immersion nozzle on the tundish, and connect the argon blowing system inlet pipe to the argon gas pipeline;

[0018] 3) Before pouring, turn on the argon blowing system. Argon gas enters through the inlet pipe, passes through the lower pipe, and is ejected through the outlet pipe.

[0019] 4) During the continuous casting process, adjust the argon flow rate according to the slag formation of the protective slag and the fluctuation of the liquid level in the crystallizer. When the fluctuation of the liquid level in the crystallizer is greater than ±5mm, increase the argon flow rate by 10% to 90%; conversely, when the melting of the protective slag on the liquid level in the crystallizer is more than 10% below the set value, decrease the argon flow rate by 10% to 90% until the continuous casting is completed.

[0020] Compared with the prior art, the present invention has at least the following technical effects or advantages:

[0021] The immersion inlet of this invention consists of an upper outlet and a lower outlet. The upper outlet faces upwards, allowing the molten steel flowing out to pass over the surface of the crystallizer before descending into the depths of the liquid phase cavity. The lower outlet faces downwards, allowing a small portion of the molten steel to flow towards the billet shell, while the majority flows directly downwards into the depths of the liquid phase cavity. Argon gas enters through the inlet pipe, passes through the lower pipe, and exits through the outlet pipe, blowing argon gas into the molten steel to form argon bubbles. Its function is to regulate the flow rate of the molten steel flowing out through the upper outlet; a larger argon flow results in a smaller molten steel flow, and vice versa. This regulates the flow rate of the molten steel passing over the surface of the crystallizer, thereby regulating the slag formation rate of the protective slag, reducing surface fluctuations, and ultimately controlling the quality of the cast billet.

[0022] ① The flow rate of the molten steel stream flowing across the liquid surface is adjustable at any time, which is beneficial for billet quality control; ② The amount of "head-on collision" of molten steel streams near the submerged entry nozzle is greatly reduced, thus significantly reducing slag entrapment: the impact of the molten steel streams on the liquid surface near the nozzle is reduced or even eliminated; ③ The molten steel stream flowing out of the upper outlet flows directly across the liquid surface and contacts the protective slag, instead of impacting the narrow edge of the billet shell first and then turning back to the liquid surface, thereby reducing the chance of inclusions being captured by the solidification front of the billet shell, thus reducing the inclusion content in the billet; ④ The molten steel stream flowing out of the upper outlet flows directly across the liquid surface to the surface of the crystallizer, making the liquid flow more stable, so the fluctuation amplitude of the crystallizer liquid surface is significantly reduced, reducing the occurrence of slag inclusions in the billet shell, and at the same time reducing the depth of oscillation marks; ⑤ The impact of the stream on the billet shell is reduced, improving the unevenness of the billet shell thickness and reducing the occurrence of defects such as longitudinal cracks; ⑥ The liquid surface temperature is higher, which is conducive to accelerating the melting of the protective slag. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure and process principle of the present invention.

[0024] Figure 2 yes Figure 1 A magnified view of a portion of the image.

[0025] In the picture:

[0026] 1-Main body 2-Inlet pipe 3-Lower pipe 4-Outlet pipe 5-Upper outlet 6-Lower outlet 7-Crystallizer α-Angle between upper outlet and main body axis β-Angle between lower outlet and main body axis S-Distance between upper outlet and lower outlet Detailed Implementation

[0027] The embodiments of the present invention are described in detail below. To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0029] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0030] In the description of this invention, it should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0031] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0032] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0033] like Figure 1 , Figure 2 As shown, an immersion nozzle for improving the quality of cast billets includes an immersion nozzle and an argon blowing system, wherein the immersion nozzle is installed on the tundish.

[0034] The submersible inlet body is vertically positioned with a vertical axis, and is an elongated cylinder that is open at the top and closed at the bottom. The upper part of the body 1 is a trumpet-shaped cylinder, and the lower part is a straight cylinder.

[0035] The bottom of the main body 1 has an upper outlet 5 and a lower outlet 6. The upper outlet 5 is inclined upwards, and the lower outlet 6 is inclined downwards. The upper outlet 5 is located above the lower outlet 6. The upper outlet 5 is a cylindrical hole, and there are two upper outlets 5, which are symmetrical from left to right. The lower outlet 6 is a cylindrical hole, and there are two lower outlets 6, which are symmetrical from left to right.

[0036] The angle between the upper outlet 5 and the axis of the main body is α, 50°≤α≤80°; the angle between the lower outlet 6 and the axis of the main body is β, 55°≤β≤85°. The distance between the upper outlet 5 and the lower outlet 6 is S, 50mm≤α≤150mm.

[0037] The argon blowing system includes an inlet pipe 2, a lower pipe 3, and an outlet pipe 4. The inlet pipe 2 is connected to the argon gas pipeline and extends horizontally into the upper part of the side wall of the main body. The lower pipe 3 is vertically installed on the side wall of the main body. The top of the lower pipe 3 is connected to the inlet pipe 2, and the bottom of the lower pipe 3 is located at the upper outlet 5. The bottom of the lower pipe 3 is connected to the horizontal outlet pipe 4. Argon gas enters through the inlet pipe 2, passes through the lower pipe 3, and is ejected through the outlet pipe 4.

[0038] The immersion nozzle of this invention consists of an upper outlet 5 and a lower outlet 6. The upper outlet 5 is angled upwards, and the molten steel flowing out from it passes over the molten steel surface of the crystallizer 7 and then flows downwards into the depths of the liquid phase cavity. The lower outlet 6 is angled downwards, and a small portion of the molten steel flowing out from it flows towards the billet shell, while most of it flows directly downwards into the depths of the liquid phase cavity.

[0039] Argon gas enters through the inlet pipe 2 of the argon blowing system, passes through the lower pipe 3, and is ejected through the outlet pipe 4, blowing argon gas into the molten steel to form argon bubbles. Its function is to regulate the flow rate of the molten steel flowing out through the upper outlet 5. A larger argon blowing volume results in a smaller molten steel flow rate, and vice versa. This regulates the flow rate of the molten steel flowing across the surface of the crystallizer, thereby regulating the slag formation rate of the protective slag, reducing surface fluctuations, and ultimately controlling the quality of the cast billet.

[0040] A method for improving the quality of cast billets, based on the aforementioned submerged entry nozzle for improving cast billet quality, specifically includes the following steps:

[0041] 1) Bake the immersion sprue before use;

[0042] 2) Install the immersion nozzle on the tundish, and connect the argon blowing system inlet pipe to the argon gas pipeline;

[0043] 3) Before pouring, turn on the argon blowing system. Argon gas enters through the inlet pipe, passes through the lower pipe, and is ejected through the outlet pipe.

[0044] 4) During the continuous casting process, adjust the argon flow rate according to the slag formation of the protective slag and the fluctuation of the liquid level in the crystallizer. When the fluctuation of the liquid level in the crystallizer is greater than ±5mm, increase the argon flow rate by 10% to 90%; conversely, when the melting of the protective slag on the liquid level in the crystallizer is more than 10% below the set value, decrease the argon flow rate by 10% to 90% until the continuous casting is completed.

[0045] When the flow rate of molten steel from the upper outlet 5 is too large, the fluctuation range of the liquid surface in the crystallizer will increase, and the melting rate of the protective slag will also be too large. When the fluctuation range of the liquid surface in the crystallizer is greater than the control range, the argon flow rate is increased to reduce the flow rate of molten steel from the upper outlet 5. Conversely, when the protective slag on the liquid surface in the crystallizer melts too slowly, the argon flow rate is increased to increase the flow rate of molten steel from the upper outlet 5.

[0046] The advantages of this invention are as follows: ① The flow rate of the stream flowing across the liquid surface is adjustable at any time, which is beneficial for billet quality control; ② The amount of "head-on collision" of molten steel streams near the submerged nozzle is greatly reduced, thus significantly reducing slag entrainment: the impact of streams on the liquid surface near the nozzle is reduced or even eliminated; ③ The molten steel stream flowing out of the upper outlet 5 flows directly across the liquid surface and contacts the protective slag, instead of impacting the narrow edge of the billet shell first and then returning to the liquid surface. Therefore, the structure of this invention reduces the chance of inclusions being captured by the solidification front of the billet shell, thereby reducing the inclusion content in the billet; ④ The molten steel stream flowing out of the upper outlet 5 flows directly across the liquid surface to the molten steel surface of the crystallizer, making the flow more stable. Therefore, the fluctuation amplitude of the molten steel surface in the crystallizer is significantly reduced, reducing the occurrence of slag inclusions in the billet shell and reducing the depth of vibration marks; ⑤ The impact of the stream on the billet shell is reduced, improving the unevenness of the billet shell thickness and reducing defects such as longitudinal cracks; ⑥ The liquid surface temperature is higher, which is conducive to accelerating the melting of the protective slag.

[0047] Example 1:

[0048] Continuous casting of automotive steel slabs, slab specifications: width: 1550mm, thickness: 300mm.

[0049] 1. Prepare an immersion nozzle. The upward angle of the upper outlet 5 is 60° with respect to the axis of the immersion nozzle. The downward angle of the lower outlet 6 is 65° with respect to the axis of the immersion nozzle. The distance S between the upper and lower outlets is 85 mm.

[0050] 2. Bake the immersion sprue before use.

[0051] 3. Install the immersion nozzle on the tundish, and connect the argon blowing system inlet pipe 2 to the argon gas pipeline;

[0052] 4. Before pouring, turn on the argon blowing system. Argon gas enters through the inlet pipe 2, passes through the lower pipe 3, and flows out through the outlet pipe 4.

[0053] 5. During the continuous casting process, adjust the argon flow rate to 3.0 L / min based on the slag formation of the protective slag and the fluctuation of the liquid level at the meniscus.

[0054] 6. Continue casting until completion.

[0055] Low-magnification and purity tests revealed that the surface and internal quality of the cast billet were significantly superior to that of billets produced using traditional submerged entry nozzles. The total oxygen content decreased from 0.0029% to 0.0018%, large particle inclusions decreased by 72%, oscillation mark depth decreased by approximately 1.2 mm, slag inclusion defect rate decreased by 65%, and the incidence of longitudinal crack defects decreased from 0.02 times / casting to 0 times.

[0056] Example 2:

[0057] Continuous casting of ship plate steel slabs, slab specifications: width: 1600mm, thickness: 230mm.

[0058] 1. Prepare an immersion nozzle. The upward angle of the upper outlet 5 is 70° with the axis of the immersion nozzle. The downward angle of the lower outlet 6 is 60° with the axis of the immersion nozzle. The distance S between the upper and lower outlets is 95 mm.

[0059] 2. Bake the immersion sprue before use;

[0060] 3. Install the immersion nozzle on the tundish, and connect the argon blowing system inlet pipe 2 to the argon gas pipeline;

[0061] 4. Before pouring, turn on the argon blowing system. Argon gas enters through the inlet pipe 2, passes through the lower pipe 3, and flows out through the outlet pipe 4.

[0062] 5. During the continuous casting process, adjust the argon flow rate to 4.5 L / min based on the slag formation of the protective slag and the fluctuation of the liquid level at the meniscus.

[0063] 6. Continue casting until completion.

[0064] Low-magnification and purity tests revealed that the surface and internal quality of the cast billet were significantly superior to that of billets produced using traditional submerged entry nozzles. The total oxygen content decreased from 0.0032% to 0.0020%, large particle inclusions decreased by 75%, oscillation mark depth decreased by approximately 1.0 mm, slag inclusion defect rate decreased by 77%, and the incidence of longitudinal crack defects decreased from 0.015 times / casting to 0 times.

[0065] This invention eliminates vortices on the surface of molten steel in the crystallizer during continuous casting, preventing the entrapment of protective slag. Simultaneously, it reduces the impact of the flow stream on the billet shell, improves uneven shell thickness, and reduces defects such as longitudinal cracks. This invention significantly improves the quality of cast billets.

[0066] The scope of protection of this invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this invention, based on the technical solution and inventive concept of this invention, should be included within the scope of protection of this invention.

Claims

1. A submerged entry nozzle for improving the quality of cast billets, characterized in that: Including immersion nozzles and argon blowing systems; The body of the immersion nozzle is a long cylinder with an open top and a closed bottom. The lower part of the main body is provided with an upper outlet and a lower outlet; The upper outlet is inclined upward, the lower outlet is inclined downward, and the upper outlet is located above the lower outlet; The angle between the upper outlet and the axis of the main body is α, where 50°≤α≤80°; The angle between the lower outlet and the axis of the main body is β, where 55°≤β≤85°; The distance between the upper and lower outlets is S, where 50 mm ≤ α ≤ 150 mm; The argon blowing system includes an inlet pipe, a lower pipe, and an outlet pipe; The inlet pipe is connected to the argon gas pipeline. The inlet pipe extends into the upper part of the side wall of the main body. The lower pipe is vertically installed on the side wall of the main body. The top of the lower pipe is connected to the inlet pipe, the bottom of the lower pipe is located at the upper outlet, and the bottom of the lower pipe is connected to the outlet pipe. Argon gas enters through the inlet pipe, passes through the lower pipe, and is ejected through the outlet pipe; The upper outlet has an upward outlet angle, and the molten steel flowing out from it flows over the surface of the molten steel in the crystallizer and then downwards into the depths of the liquid phase cavity; the lower outlet has a downward outlet angle, and a small portion of the molten steel flowing out from it flows towards the billet shell, while most of it flows directly downwards into the depths of the liquid phase cavity; argon gas enters through the inlet pipe, passes through the lower pipe, and is ejected from the outlet pipe, blowing argon gas into the molten steel to form argon bubbles. Its function is to regulate the flow rate of molten steel flowing out of the upper outlet. A larger argon blowing volume results in a smaller molten steel flow rate, and vice versa. This can regulate the flow rate of molten steel flowing through the surface of the crystallizer, thereby regulating the slag formation rate of the protective slag and reducing surface fluctuations, thus controlling the quality of the cast billet.

2. The submerged entry nozzle for improving billet quality according to claim 1, characterized in that: The upper outlet consists of two symmetrical holes.

3. The submerged entry nozzle for improving billet quality according to claim 1, characterized in that: The lower outlet consists of two symmetrical holes.

4. The submerged entry nozzle for improving billet quality according to claim 1, characterized in that: The immersion nozzle is installed on the intermediate tundish.

5. The submerged entry nozzle for improving billet quality according to claim 1, characterized in that: The upper part of the body is trumpet-shaped, and the lower part is cylindrical.

6. A method of improving the quality of a cast slab, realized by means of a submerged entry nozzle according to any one of claims 1-5, characterized in that, Specifically, the steps include the following: 1) Bake the immersion sprue before use; 2) Install the immersion nozzle on the tundish, and connect the argon blowing system inlet pipe to the argon gas pipeline; 3) Before pouring, turn on the argon blowing system. Argon gas enters through the inlet pipe, passes through the lower pipe, and is ejected through the outlet pipe. 4) During the continuous casting process, adjust the argon flow rate according to the slag formation of the protective slag and the fluctuation of the liquid level in the crystallizer. When the fluctuation of the liquid level in the crystallizer is greater than ±5mm, increase the argon flow rate by 10%~90%. Conversely, when the melting of the protective slag on the liquid level in the crystallizer is more than 10% below the set value, decrease the argon flow rate by 10%~90% until the continuous casting is completed.

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