A quick-change method for a continuous casting round billet tundish

Abstract

The present application relates to a kind of continuous casting round billet tundish quick-change method, comprising the following steps: first step: molten steel in tundish is poured to predetermined tonnage;Second step: complete the pouring of first pouring, put the first connecting piece of inverted cone shape in crystallizer, so that the first connecting piece and the molten steel in the crystallizer can contract together to liquid core;Third step: after the first connecting piece compaction, put the second connecting piece in crystallizer;Fourth step: start normal second pouring pouring.When the molten steel in the second tundish reaches the specified tonnage, open the tundish stopper, and the molten steel enters the crystallizer to produce the casting billet.By putting the first connecting piece in the crystallizer, the first pouring casting billet can be blocked, to avoid the second pouring protective slag being rolled into the first pouring casting billet deep, to ensure that the casting billet produced after tail cutting meets the standard, realizes the tundish quick-change for large-scale continuous casting round billet.

Description

Technical Field

[0001] This invention relates to the field of quick-change technology for tundishes in continuous casting round billets, and more particularly to a method for quick-change of tundishes in continuous casting round billets. Background Technology

[0002] With the increasing demands of the continuous casting industry and the continuous development of high-efficiency continuous casting machines, the service life of the tundish directly affects the operating efficiency of the continuous casting machine. Previously, although various measures had been adopted to extend the service life of the tundish, it was still impossible to achieve continuous casting for extended periods. Therefore, quick-change technology for the tundish emerged, effectively solving this problem and improving production efficiency.

[0003] The existing quick-change tundish technology between continuous casting cycles has become a widely adopted and effective measure in the industry. However, the aforementioned quick-change tundish technology is only applicable to specifications with a nominal diameter of 500 mm or less. When the specifications are small, the amount of molten steel used is also small, and the solidification rate is fast at the end of the casting process. The protective slag is usually drawn into the mold at a depth of about 3 to 4 meters below the meniscus, which can be removed by simply cutting off the tail of the cast billet. However, for large specifications, after the molten steel is poured, due to the large size and high enthalpy of the steel, the heat cannot be dissipated in a short time. During quick-change, the protective slag from the next ladle will be drawn into the cast billet from the previous ladle and carried by the steel flow to a depth of about 10 to 15 meters below the meniscus of the mold. If it is removed by cutting off the tail at this point, it will cause huge waste, thereby affecting the overall efficiency of continuous casting and making the quick-change technology counterproductive.

[0004] Therefore, the existing quick change process for large-size continuous casting round billets is very prone to causing slag entrapment in the protective slag. Summary of the Invention

[0005] To address the problem that existing quick-change processes for large-size continuous casting billets easily lead to slag entrapment in protective slag, this invention provides a quick-change method for the tundish of continuous casting billets.

[0006] To achieve the objective of this invention, a quick-change method for the tundish of continuously cast round billets is provided, comprising the following steps:

[0007] Step 1: Close the nozzle of the first ladle, rotate the first ladle to the waiting position, and pour the molten steel in the first tundish to the predetermined tonnage;

[0008] Step 2: Complete the first pouring, close the first tundish nozzle, drive away the first tundish car, and put the first inverted cone-shaped connector into the crystallizer so that the first connector and the molten steel in the crystallizer can shrink together toward the liquid core.

[0009] Step 3: After compacting the first connector, place the second connector into the crystallizer;

[0010] Step 4: Move the second tundish to the pouring position, adjust the distance, rotate the second ladle to the pouring position, attach the long nozzle of the second tundish, open the nozzle of the second ladle, and begin the second pouring process normally. When the molten steel in the second tundish reaches the specified tonnage, open the tundish stopper rod, and the molten steel enters the crystallizer to produce the billet.

[0011] In some specific embodiments, in the second step, after the first pouring is completed, the casting speed is reduced to zero, the secondary cooling water is adjusted to the required level, and the three-stage electromagnetic stirring is turned off.

[0012] In some specific embodiments, in the second step, before placing the first connector into the crystallizer, the inside of the crystallizer is purged with argon gas to complete the cleaning of the protective slag.

[0013] In some specific embodiments, in the third step, after placing the second connector into the crystallizer, cold material is added.

[0014] In some specific embodiments, in the fourth step, after the billet is produced, the billet is placed in a slow cooling pit to cool to room temperature, and the oxide scale on the surface of the billet is cleaned off; along the direction of billet pulling, the billet is subjected to ultrasonic testing to detect shrinkage cavities in the billet; the location of the shrinkage cavity is the location of the first connector; the billet is cut off at the location of the first connector.

[0015] In some specific embodiments, the first connector is a funnel structure in the shape of an inverted cone; a cross handle is provided at the outlet of the first connector to facilitate the insertion of the first connector into the crystallizer.

[0016] In some specific embodiments, the second connector includes: a base with multiple through holes to allow molten steel to pass through the base; multiple steel bars evenly distributed around the axis of the base on the sides of the base to support the cast billet; and multiple steel wires sequentially looped around the axis of the base and wrapped around the multiple steel bars to restrict the steel bars so that the second connector forms a barrel-shaped structure.

[0017] In some specific embodiments, the nominal diameter of the cast billet is greater than or equal to 600 mm.

[0018] In some specific embodiments, before placing the first connector into the crystallizer in the second step, a first preset time is required; after completing the first pouring in the second step, a second preset time is required before starting the second pouring in the fourth step; the range of the first preset time is 2 minutes to 4 minutes; the range of the second preset time is 12 minutes to 15 minutes.

[0019] In some specific embodiments, the height of the first connector is greater than or equal to 70% of the nominal diameter of the continuously cast round billet; the vent diameter of the first connector is 50% of the nominal diameter of the continuously cast round billet.

[0020] The beneficial effects of this invention are:

[0021] The present invention discloses a quick-change method for tundishes in continuous casting of round billets. During the replacement of the tundish with a new one, an inverted conical first connector is placed inside the crystallizer. This first connector contracts towards the liquid core along with the molten steel, sealing the billet from the first casting. This prevents the protective slag from being drawn deeper into the billet during the second casting, facilitating the subsequent billet trimming process and ensuring that the produced billets meet normal industrial standards. This method achieves quick tundish changeover for large-scale continuous casting, thereby ensuring production efficiency and a high yield rate. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the workflow of a quick-change method for tundish in continuous casting of round billets according to the present invention;

[0023] Figure 2 yes Figure 1 The diagram shows the working state of the quick-change method for the tundish of continuously cast round billets.

[0024] Figure 3 yes Figure 1 The diagram shows another working state of the quick change method for the tundish of continuously cast round billets.

[0025] Figure 4 yes Figure 2 or Figure 3 Structural schematic diagrams of some specific embodiments of the first connector shown;

[0026] Figure 5 yes Figure 2 or Figure 3 Structural schematic diagrams of some specific embodiments of the second connector shown;

[0027] Figure 6 yes Figure 1 A schematic diagram of the quick-change tundish for continuous casting round billets.

[0028] In the attached diagram, 100 is the first connector; 110 is the cross handle; 200 is the second connector; 210 is the base; 220 is the steel bar; 230 is the steel wire; 300 is the crystallizer; 400 is the billet; 410 is the billet of the first casting; 420 is the billet of the second casting; and 430 is the liquid core. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0030] Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar symbols denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0031] In the description of this invention, it should be understood that the terms "top", "bottom", "inner", "outer", "axis", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention or simplifying the description, and do not 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.

[0032] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0033] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," "fixing," "linking," "hinging," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0034] Reference Figure 1 , Figure 2 , Figure 3 Figure 4 , Figure 5 and Figure 6A quick-change method for the tundish of continuously cast round billets includes the following steps:

[0035] Step 1: Close the first ladle nozzle, rotate the first ladle in the ladle pouring position to the ladle waiting position, and pour the molten steel in the first tundish in the tundish pouring area to the predetermined tonnage;

[0036] Step 2: After completing the first pour, close the first tundish nozzle, move the first tundish car to the tundish preparation area, and place the inverted cone-shaped first connector 100 into the crystallizer 300 so that the first connector 100 and the molten steel in the crystallizer 300 can contract together towards the liquid core 430.

[0037] Step 3: After compacting the first connector 100, place the second connector 200 into the crystallizer 300;

[0038] Step 4: Move the second tundish car from the tundish preparation area to the tundish pouring position, adjust the distance, rotate the second ladle to the ladle pouring position, attach the long nozzle of the second tundish, open the nozzle of the second ladle, and begin the second pouring process normally. When the molten steel in the second tundish reaches the specified tonnage, open the tundish stopper rod, and the molten steel enters the 300mm crystallizer, producing a 400mm billet.

[0039] Specifically, the first connector 100 is made of aluminum refractory material, which can withstand the high temperature and corrosion of molten steel. Furthermore, the first connector 100 is inverted conical in shape. After the first pouring operation is completed in the crystallizer 300 via the first tundish car, the first tundish car is driven away, and a first preset time is waited for the first pouring billet 410 to cool to a certain extent. Then, the first connector 100 is placed into the crystallizer 300. At this time, under the action of gravity, the first connector 100 will contract towards the liquid core 430 along with the still-uncooled molten steel from the first pouring. At this point, the first connector 100 can be pressed down using an iron rod or pestle to gently compact it, thus sealing the first pouring billet 410. Simultaneously, starting from the completion of the first pouring, after a second preset time, the first pouring billet 410 is allowed to cool to a certain extent before the second tundish car is opened. The second pouring is then completed in the crystallizer 300 via the second tundish. Once the second pouring billet 420 has also cooled, a complete billet 400 is obtained. The first connector 100 prevents the protective slag from being drawn deeper into the billet 400 when the second tundish is opened, thereby reducing the tail length of the subsequent billet 400. This allows for quick changeover operations for large-size continuous casting round billets while ensuring production efficiency and producing qualified billets.

[0040] In some specific embodiments of the present invention, in the second step, after the first pouring is completed, the turntable can be rotated 90 degrees to place it in the pouring waiting position, and the pouring speed can be reduced to zero to stop pouring. This facilitates the removal of the first tundish car, and the second cooling water is adjusted to the required level. At the same time, the three-stage electromagnetic stirring is turned off, thus providing convenient conditions for the subsequent step of placing the first connector 100.

[0041] In some specific embodiments of the present invention, in the second step, before placing the first connector 100 into the crystallizer 300, the crystallizer 300 is purged with an argon gas pipe to clean the protective slag. By purging the crystallizer 300 with an argon gas pipe, the protective slag in the crystallizer 300 is cleaned as much as possible before the second pouring process. This measure, in conjunction with the subsequent placement of the first connector 100 into the crystallizer 300, further reduces the amount of protective slag in the crystallizer 300, thereby preventing the protective slag from the second pouring process from being drawn deeper into the billet 400.

[0042] In some specific embodiments of the present invention, after placing the second connector 200 into the crystallizer 300 in the third step, cold material is added. The added cold material can accelerate the cooling of the second-cast billet 420, which helps to form a complete billet 400. The second connector 200 can also cool the second-cast billet 420, and the added cold material effectively connects the first-cast billet 410 and the second-cast billet 420.

[0043] In some specific embodiments of the present invention, in the fourth step, after the billet 400 is produced, it is placed in a slow cooling pit to cool to room temperature, and the oxide scale on the surface of the billet 400 is cleaned off. Following the casting direction, the billet 400 is subjected to ultrasonic testing to detect shrinkage cavities. The location of the shrinkage cavity is the location of the first connector 100. The billet 400 is then trimmed at the location of the first connector 100.

[0044] Specifically, the first connector 100 prevents the protective slag from being drawn deeper into the billet 410 of the first casting in the second casting. Simultaneously, during the second preset waiting period before the second casting, starting from the completion of the first casting, a large shrinkage cavity will form at the location of the liquid core 430 at the bottom of the first connector 100 because no more molten steel is added to the crystallizer 300. At this time, the billet 400 is subjected to UT (ultrasonic testing) flaw detection using an ultrasonic testing device. UT flaw detection can easily detect the absence of bottom waves in the billet 400, and the location of this absence of bottom waves is the location of the first connector 100 within the billet 400. This allows for the accurate determination of the tail length of the billet 400, which is generally between 3 and 4 meters. The remaining billet 400 after the cutting process is the normal billet, meeting normal industrial standards. Compared to the original tail-cutting length of about 10 meters or even 15 meters, only 3 to 4 meters of length is cut off, ensuring a product qualification rate of 400 for the produced billets, thus realizing the application of tundish quick change technology in large-size round billet continuous casting.

[0045] In some specific embodiments of the present invention, the first connector 100 is an inverted cone-shaped funnel structure, with the bottom end of the funnel facing the first casting billet 410. By compacting the inverted cone-shaped funnel structure of the first connector 100, the first connector 100 can seal the first casting billet 410 more tightly. At the same time, through the inclined structure of the inverted cone shape, the first connector 100 can more easily shrink towards the liquid core 430 together with the uncooled end of the first casting. A cross handle 110 is provided at the funnel position at the top of the first connector 100. The cross handle 110 consists of two horizontal beams, the two ends of which are respectively connected to the side wall of the funnel position at the top of the first connector 100, so that the two horizontal beams are staggered to form a cross structure. This allows the operator to place the first connector 100 into the crystallizer 300 through the cross handle 110.

[0046] In some specific embodiments of the present invention, the second connecting member 200 includes: a base plate 210, steel bars 220, and steel wires 230. The base plate 210 has multiple through holes, allowing molten steel from the second pour to pass through the base plate 210 and fill the crystallizer 300 up to the top of the first connecting member 100. Multiple steel bars 220 are arranged with their bottom ends evenly distributed around the axis of the base plate 210 on its outer side, and their top ends extending upwards and outwards. These steel bars 220 provide support for the final produced billet 400 and also accelerate the cooling and forming of the billet 420 from the second pour, thereby increasing the cooling rate of the billet 400. Multiple steel wires 230 are arranged around the axis of the chassis 210 and sequentially sleeved on multiple steel bars 220. The multiple steel wires 230 restrict the multiple steel bars 220, thereby controlling their tilt angle. This allows the second connector 200 to form a barrel-like structure, supporting the casting 400. When the casting 400 undergoes ultrasonic testing, abnormal reflected waves (i.e., bottomless waves) can be easily detected. The location of this bottomless wave is the funnel-shaped head of the inverted cone structure of the first connector 100. By cutting off a certain length of the tail from this funnel-shaped head, the tail-cutting process of the casting 400 can be completed.

[0047] In some specific embodiments of the present invention, the nominal diameter of the cast billet 400 is greater than or equal to 600 mm. The first preset time ranges from 2 minutes to 4 minutes. The second preset time ranges from 12 minutes to 15 minutes. The height of the first connector 100 is greater than or equal to 70% of the nominal diameter of the continuously cast round billet. The vent diameter of the first connector 100 is 50% of the nominal diameter of the continuously cast round billet.

[0048] When performing a quick change of tundish on a four-strand, four-channel round billet continuous casting machine with a nominal diameter of 600 mm, the following steps are included:

[0049] Step 1: Close the first ladle nozzle, rotate the first ladle in the ladle pouring position to the ladle waiting position, and pour 10 tons of molten steel from the first tundish in the tundish pouring area.

[0050] Step 2: After completing the first pouring, close the first tundish nozzle, drive the first tundish car to the tundish preparation area, wait 2-3 minutes, and put the inverted cone-shaped first connector 100 into the crystallizer 300 so that the first connector 100 and the molten steel in the crystallizer 300 can shrink together towards the liquid core 430.

[0051] Step 3: Gently press the first connector 100 with an iron rod or iron pestle. After pressing the first connector 100, put the second connector 200 into the crystallizer 300 and put in the cold material.

[0052] Step 4: Move the second tundish car from the tundish preparation area to the tundish pouring position, adjust the distance, rotate the second ladle to the ladle pouring position, attach the long nozzle of the second tundish, open the second ladle nozzle, and begin the second pouring process normally. The time from stopping pouring to resuming normal pouring should be approximately 12 minutes. Once the molten steel in the second tundish reaches the designated tonnage, open the tundish stopper rod, and the molten steel enters the 300mm crystallizer, producing a 400mm billet.

[0053] Step 5: The produced billet 400 is quickly placed into a slow cooling pit. After the billet 400 cools to room temperature, the iron oxide scale on the surface of the billet 400 is cleaned off. Ultrasonic testing is then performed on the billet 400 along the casting direction to detect the location of the shrinkage cavity at the bottom of the first connector 100. The location approximately 3 to 3.5 meters backward from the shrinkage cavity location is the tail section of the billet 400.

[0054] Step 6: Cut off the tail of the 400mm cast billet. The remaining 400mm cast billet after cutting off is the normal billet.

[0055] The diameter of the vent at the top of the first connector 100 is approximately 300 mm, which is the radius of the continuously cast round billet. The height of the first connector 100 is approximately 450 mm.

[0056] When performing a quick change of tundish on a round billet continuous casting machine with a diameter tolerance of 700 mm (four-strand, four-cup), the following steps are included:

[0057] Step 1: Close the first ladle nozzle, rotate the first ladle in the ladle pouring position to the ladle waiting position, and pour 14 tons of molten steel from the first tundish in the tundish pouring area.

[0058] Step 2: After completing the first pouring, close the first tundish nozzle, drive the first tundish car to the tundish preparation area, wait 3-4 minutes, and put the inverted cone-shaped first connector 100 into the crystallizer 300 so that the first connector 100 and the molten steel in the crystallizer 300 can shrink together towards the liquid core 430.

[0059] Step 3: Gently press the first connector 100 with an iron rod or iron pestle. After pressing the first connector 100, put the second connector 200 into the crystallizer 300 and put in the cold material.

[0060] Step 4: Move the second tundish car from the tundish preparation area to the tundish pouring position, adjust the distance, rotate the second ladle to the ladle pouring position, attach the long nozzle of the second tundish, open the second ladle nozzle, and begin the second pouring process normally. The time from stopping pouring to resuming normal pouring should be approximately 15 minutes. Once the molten steel in the second tundish reaches the designated tonnage, open the tundish stopper rod, and the molten steel enters the 300mm crystallizer, producing a 400mm billet.

[0061] Step 5: The produced billet 400 is quickly placed into a slow cooling pit. After the billet 400 cools to room temperature, the iron oxide scale on the surface of the billet 400 is cleaned off. Ultrasonic testing is then performed on the billet 400 along the casting direction to detect the location of the shrinkage cavity at the bottom of the first connector 100. The location extending approximately 3.5 to 4 meters backward from the shrinkage cavity location is the tail section of the billet 400.

[0062] Step 6: Trim the 400mm tail of the cast billet. The remaining 400mm tail of the cast billet after trimming is the normal billet.

[0063] The diameter of the vent at the top of the first connector 100 is approximately 350 mm, which is the radius of the continuously cast round billet. The height of the first connector 100 is approximately 530 mm.

[0064] In the description of this specification, references to terms such as "an embodiment," "some embodiments," "example," "specific example," or "a specific embodiment" or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0065] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for quick change of tundish for continuous casting round billets, characterized in that, Includes the following steps: Step 1: Close the nozzle of the first ladle, rotate the first ladle to the waiting position, and pour the molten steel in the first tundish to the predetermined tonnage; Step 2: Complete the first pouring, close the first tundish nozzle, drive away the first tundish car, and put the first inverted cone-shaped connector into the crystallizer so that the first connector and the molten steel in the crystallizer can shrink together toward the liquid core. Step 3: After compacting the first connector, place the second connector into the crystallizer; Step 4: Drive the second tundish car to the pouring position, adjust the distance, rotate the second ladle to the ladle pouring position, attach the long nozzle of the second tundish, open the nozzle of the second ladle, and start the second pouring normally. When the molten steel in the second tundish reaches the specified tonnage, open the tundish stopper rod, and the molten steel enters the crystallizer to produce the billet. In the second step, after the first pour is completed, the casting speed is reduced to zero, the secondary cooling water is adjusted to the required level, and the three-stage electromagnetic stirring is turned off. In the second step, before placing the first connector into the crystallizer, the inside of the crystallizer is purged with argon gas to clean the protective slag. In the third step, after placing the second connector into the crystallizer, cold material is added; In the fourth step, after the billet is produced, the billet is placed in a slow cooling pit to cool to room temperature, and the oxide scale on the surface of the billet is cleaned off. Along the casting direction, the billet is subjected to ultrasonic testing using an ultrasonic testing device to detect shrinkage cavities in the billet. The location of the shrinkage hole is the location of the first connector; The casting billet is trimmed at the location of the first connector; The first connector is a funnel-shaped structure in the shape of an inverted cone; The first connector has a cross handle at the outlet to facilitate placing the first connector into the crystallizer; The second connector includes: A chassis, wherein multiple through holes are provided on the chassis to allow molten steel to pass through the multiple through holes into the chassis; Steel bars, wherein there are multiple steel bars, and the multiple steel bars are evenly arranged on the side of the base plate around the axis of the base plate, so that the steel bars can support the casting billet; The steel wires, which are multiple in number, are sequentially sleeved around the axis of the chassis on multiple steel bars to restrict the multiple steel bars so that the second connector forms a barrel-shaped structure.

2. The quick-change method for the tundish of continuously cast round billets according to claim 1, wherein, The nominal diameter of the cast billet is greater than or equal to 600 mm.

3. The quick-change method for the tundish of continuously cast round billets according to claim 1, wherein, Before placing the first connector into the crystallizer in the second step, a first preset time needs to be waited; In the second step, after the first pouring is completed, a second preset time is required before the second pouring begins normally in the fourth step. The first preset time ranges from 2 minutes to 4 minutes; The second preset time ranges from 12 minutes to 15 minutes.

4. The quick-change method for the tundish of continuously cast round billets according to claim 1, wherein, The height of the first connector is greater than or equal to 70% of the nominal diameter of the continuous casting billet, and the vent diameter of the first connector is 50% of the nominal diameter of the continuous casting billet.

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