A method for improving the success rate of quick change of tundish in slab continuous caster

Abstract

The present application relates to the field of metallurgy, in particular to a method for improving the success rate of tundish quick change in slab continuous casting machine. The steps include ensuring that the mold is only left with a liquid slag layer and controlling the thickness of the liquid slag layer before the final casting of the old tundish, adding starting slag into the mold and fully melting it into liquid state; picking out the slag ring and slag strip in the mold after the final casting of the old tundish, and melting the fine slag strip; controlling the amount of water sprayed in each link of the straightening machine at the time of stopping and straightening; improving the lifting speed of the tundish and the walking speed of the tundish car during the tundish quick change process, setting the pre-centering scale and pre-centering rod for pre-centering; smearing silicone on the corner seam of the mold before the starting of the new tundish, and inserting the flow barrier and iron sheet into the mold; controlling the time of starting, the slope of the speed-up rate of straightening, and the holding time of the casting speed after the starting of the new tundish. The application of the present application in the tundish quick change process can shorten the quick change time, reduce the generation of waste billets, reduce the risk of accidents, and improve the success rate of quick change.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, specifically to a method for improving the success rate of quick tundish changeover in slab continuous casting machines. Background Technology

[0002] The tundish is a refractory container used in the continuous casting process of steel, serving to hold molten steel and pour it into the crystallizer. Due to the limited lifespan of the refractory material in the working layer, continuous casting tundishes require shutdown and replacement with a new tundish after a certain pouring time, resulting in low efficiency. Quick-change tundish technology refers to the rapid replacement of the tundish without stopping the continuous casting machine, allowing the old and new slabs to fuse and enabling continuous operation, effectively increasing the continuous casting machine's capacity.

[0003] In existing technologies, when tundish quick-change is performed on slab continuous casting machines, the long replacement time between the old and new tundishes and the additional time required for centering after the new tundish is in place result in a long stop-and-straighten time for the continuous casting machine. This leads to the molten steel in the crystallizer easily solidifying and shrinking, forming a crust, and solidified protective slag strips and slag rings are likely to exist in the crystallizer. As a result, the old and new slabs are difficult to effectively fuse after the quick-change, producing scrap slabs and increasing production costs. At the same time, the slabs in the sector section are prone to bulging due to the static pressure of the molten steel, posing a risk of horizontal slab accidents. Summary of the Invention

[0004] To address the technical problems of long tundish quick change time, difficulty in fusion of old and new slabs after tundish quick change, and potential accident risks in slab continuous casting machines, this invention provides a method to improve the success rate of tundish quick change in slab continuous casting machines. Corresponding measures are taken before and after final pouring in the old tundish, during the tundish quick change process, and before and after pouring in the new tundish to shorten the tundish quick change time, promote better fusion of old and new slabs, and reduce accident risks.

[0005] The technical solution of the present invention is as follows:

[0006] A method for improving the success rate of quick ladle change in slab continuous casting machines, the specific measures are as follows:

[0007] (1) Before the final casting of the old tundish, ensure that only liquid slag layer remains in the mold, and control the thickness of the liquid slag layer.

[0008] (2) Before the final casting of the old intermediate ladle, add the casting slag into the crystallizer and make the casting slag fully melt into liquid state;

[0009] (3) After the final casting of the old tundish, pick out the slag rings and slag strips in the crystallizer, and crush the fine slag strips that cannot be picked out and press them into the molten steel to melt them, so as to ensure that there is no crust on the liquid surface and no slag strips on the top of the billet shell, so as to prevent the new and old billet joints from being difficult to fuse after quick replacement due to the presence of slag strips or crust on the liquid surface in the crystallizer.

[0010] (4) Control the amount of spray water in each link of the straightening machine when the straightening machine stops, so as to ensure that the billet after exiting the crystallizer does not cool and harden prematurely due to excessive water volume, making it difficult to pass through the straightening zone or even causing a horizontal billet accident, and that the billet shell does not remelt due to insufficient water volume, resulting in steel leakage.

[0011] (5) Increase the lifting speed of the tundish and the traveling speed of the tundish car during the quick change of the tundish, and shorten the time required for the new tundish to go from the start-up to the predetermined casting position;

[0012] (6) Set a pre-alignment ruler for quick tundish change on the tundish car, and set a pre-alignment rod at the same position on the old and new tundishes. During the quick tundish change process, perform offline inner and outer arc pre-alignment of the nozzle on the new tundish to ensure that the nozzle is in the extended line of the crystallizer center in the front and back direction, thus shortening the subsequent alignment time.

[0013] (7) Before pouring into the new tundish, apply silicone to the corner seam of the crystallizer and insert baffles and iron plates into the crystallizer to prevent steel leakage accidents caused by large corner seams of the crystallizer.

[0014] (8) After the new tundish is opened for casting, control the emergence time, the slope of the straightening and speed-up, and the holding time of the straightening and speed-up to ensure that the straightening and speed-up cycle is reasonable and stable, prevent the sticking alarm caused by the opening of casting and the sticking leakage, and avoid the risk of the billet lying due to excessive low casting speed time and excessive cooling intensity of the joint.

[0015] Furthermore, the method described in this invention can be applied to the quick change process of the tundish in a 200mm thick slab continuous casting machine.

[0016] Furthermore, in step (1), the specific implementation method to ensure that only a liquid slag layer remains in the protective slag in the crystallizer is as follows: use an oxygen-burning pipe to gently stir the center of the molten steel surface, press the solid protective slag floating on the surface of the molten steel into the molten steel, and ensure that the solid protective slag melts in the molten steel.

[0017] Furthermore, in step (1), when the remaining steel in the old tundish is 15-16t, the thickness of the protective slag liquid layer in the crystallizer is controlled to be 15±1mm.

[0018] Furthermore, in step (2), when the remaining steel in the old tundish is 12-15t, starter slag is added to the crystallizer. The addition position is where the old tundish nozzle extends into the crystallizer. When the slab cross-section size is 200*1820-2000mm, 10-15kg of starter slag is added. When the slab cross-section size is 200*2010-2200mm, 15-18kg of starter slag is added.

[0019] Furthermore, in step (5), the measures to increase the lifting speed of the intermediate ladle are to adjust the speed of the throttle valve of the hydraulic system of the intermediate ladle and the lifting time of the intermediate ladle; the measures to increase the traveling speed of the intermediate ladle are to adjust the reference value of the high speed of the traveling motor of the intermediate ladle and control the time taken for the new intermediate ladle to travel from start-up to the predetermined casting position to be less than 1 minute.

[0020] Furthermore, in step (6), the pre-alignment ruler is a graduated ruler, and the installation steps for the pre-alignment ruler and the pre-alignment rod are as follows:

[0021] a. Place the old tundish on the tundish car platform and center it to confirm that the old tundish nozzle is located at the center of the inner and outer arcs of the crystallizer;

[0022] b. Install a pre-alignment ruler at any position on the side of the intermediate tundish platform. The pre-alignment ruler is perpendicular to the side where it is installed and parallel to the plane on which the intermediate tundish platform is located. Install a pre-alignment rod on the old intermediate tundish. The pre-alignment rod is perpendicular to the bottom surface of the old intermediate tundish and extends beyond the bottom surface of the old intermediate tundish. The length of the extended portion is not greater than the thickness of the intermediate tundish platform. The pre-alignment rod is installed on the old intermediate tundish at a position corresponding to the position of the pre-alignment ruler, ensuring that the pre-alignment rod can fit against the pre-alignment ruler and that at least one side of the pre-alignment rod falls within the scale range of the pre-alignment ruler.

[0023] c. Confirm the installation position of the pre-alignment marker on the old intermediate tundish, and install the same pre-alignment marker at the same position on the new intermediate tundish.

[0024] Furthermore, the specific usage method of the pre-alignment scale and pre-alignment rod is as follows: Before the tundish quick change, record the reading of the old tundish pre-alignment rod on the pre-alignment scale; during the tundish quick change, move the new tundish so that the pre-alignment rod of the new tundish is in contact with the pre-alignment scale and the reading is consistent with that of the old tundish, thus achieving pre-alignment.

[0025] Furthermore, in step (8), when the molten steel in the tundish reaches about 8-12 tons, the stopper is opened and the tundish is started to pour; when the pouring cross-section size is 200*1820mm, the emergence time is 30-50s; when the pouring cross-section size is 200*2000mm, the emergence time is 35-55s; when the pouring cross-section size is 200*2200mm, the emergence time is 40-60s; after starting the straightening process, the pulling speed is controlled at 0.3m / min and maintained for 60s to slag, and then the pulling speed is increased to 1m / min at a slope of 0.2m / min2. When the liquid slag height in the crystallizer reaches 8-15mm, the pulling speed is increased to the target pulling speed at a slope of 0.05m / min every 15s-35s.

[0026] The beneficial effects of this invention are as follows:

[0027] (1) The present invention provides a method for improving the success rate of quick change of tundish in a 200mm thick slab continuous casting machine. It improves the lifting speed of the tundish and the traveling speed of the tundish car during the quick change process, and sets a pre-alignment ruler and pre-alignment rod for quick change of tundish. During the quick change process, the new tundish is pre-aligned, which shortens the time spent in the quick change process, improves work efficiency and reduces the degree of solidification and crusting of molten steel in the crystallizer.

[0028] (2) The present invention controls the protective slag in the crystallizer to maintain a liquid state before and after the final pouring of the old tundish and before the start of pouring of the new tundish, so as to prevent foreign objects from being present at the junction of the old and new billets after the quick change due to the presence of excessively large or excessive slag bars. In addition, the start-up slag is added before the final pouring of the old tundish to further reduce the degree of steel crusting during the quick change process, promote the effective fusion of the old and new billets after the quick change of the tundish, prevent steel leakage accidents, effectively reduce the output of scrap billets, improve the quality of steel billets, and save production costs.

[0029] (3) This invention controls the amount of spray water in each section of the straightening machine after the straightening machine stops, applies glue to the corner seam of the crystallizer and sets up a diversion plate before the new tundish is started to pour, and controls the emergence time, straightening speed-up slope and straightening speed holding time after the new tundish is started to pour, thereby reducing the risk of steel leakage accidents and billet lying accidents before and after quick change, while ensuring production efficiency. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a flowchart illustrating how the present invention is applied to the intermediate package quick change process.

[0032] Figure 2 This is a front view of the installation position of the pre-alignment marker and pre-alignment ruler in Example 1.

[0033] Figure 3 This is a left view of the installation position of the pre-alignment marker and pre-alignment ruler in Example 1.

[0034] Figure 4 These are actual photos of the installation positions of the pre-alignment marker and pre-alignment ruler in Example 1.

[0035] In the diagram, 1-old intermediate package, 2-intermediate package platform, 3-pre-alignment ruler, 4-pre-alignment pole. Detailed Implementation

[0036] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0037] Example 1

[0038] A method for improving the success rate of quick tundish changeover in a 200mm thick slab continuous casting machine is applied to quick tundish changeover in a 200*2300mm cross-section slab continuous casting machine with adjustable width, producing steel billets with a cross-section of 200*2200mm. The specific measures are as follows:

[0039] (1) When the remaining steel in the old tundish is 15t, use an oxygen-burning pipe to gently stir the center of the molten steel surface, press the solid protective slag floating on the surface of the molten steel into the molten steel, ensure that the solid protective slag melts in the molten steel, and control the thickness of the protective slag layer to 15mm.

[0040] (2) When the remaining steel in the old tundish is 13t, add 16kg of casting slag into the crystallizer. The addition position is where the old tundish water nozzle extends into the crystallizer, and the casting slag is fully melted into liquid.

[0041] (3) After the final casting of the old tundish, pick out the slag rings and slag strips in the crystallizer, and crush the fine slag strips that cannot be picked out and press them into the molten steel to melt, ensuring that there is no crust on the liquid surface and no slag strips on the top of the billet shell.

[0042] (4) Control the spray water volume of each stage of the straightening machine when the straightening is stopped. Set the specific safe water volume from the foot roll of the continuous casting machine to the 8th straightening stage as follows: Loop01: 80L / min, Loop02: 45L / min, Loop03: 120L / min, Loop04: 120L / min, Loop05: 80L / min, Loop06: 20L / min, Loop07: 45L / min, Loop08: 18L / min, Loop09: 48L / min, Loop10: 19L / min, Loop11: 89L / min, Loop12: 17L / min, Loop13: 96L / min, Loop14: 19L / min, Loop15: 55L / min, Loop16: 11L / min, Loop17: 70L / min, Loop18: 36L / min, Loop19: 50L / min, Loop20: 10L / min, Loop21: 67L / min, Loop22: 27L / min;

[0043] (5) Adjust the speed of the throttle valve of the hydraulic system of the intermediate tundish car and the rapid lifting and lowering time of the intermediate tundish car, and adjust the reference value of the high speed of the intermediate tundish car's walking motor to increase the lifting and lowering speed of the intermediate tundish car and the walking speed of the intermediate tundish car during the quick change of the intermediate tundish, so as to ensure that the time from starting the new intermediate tundish to the predetermined casting position is less than 1 minute.

[0044] (6) Install a pre-alignment ruler for quick-change intermediate tundishes on the intermediate tundish car, and install pre-alignment rods at the same positions on the old and new intermediate tundishes. The pre-alignment ruler is a graduated ruler. The installation steps for the pre-alignment ruler and pre-alignment rods are as follows:

[0045] a. Place the old tundish on the tundish car platform and center it to confirm that the old tundish nozzle is located at the center of the inner and outer arcs of the crystallizer;

[0046] b. Install a pre-alignment ruler on the side of the intermediate package platform and a pre-alignment pole on the old intermediate package supplier. The installation positions of the pre-alignment ruler and the pre-alignment pole are as follows: Figures 2-4 As shown, the pre-alignment scale is perpendicular to the side where it is installed and parallel to the plane where the intermediate bale platform is located. The pre-alignment rod is perpendicular to the bottom surface of the old intermediate bale and extends beyond the bottom surface of the old intermediate bale. The length of the extended part is not greater than the thickness of the intermediate bale platform. It is ensured that the pre-alignment rod can fit with the pre-alignment scale and that at least one side of the pre-alignment rod falls within the scale range of the pre-alignment scale.

[0047] c. Confirm the installation position of the pre-alignment marker on the old intermediate tundish, and install the same pre-alignment marker at the same position on the new intermediate tundish.

[0048] Furthermore, the specific usage method of the pre-alignment scale and pre-alignment rod is as follows: Before the tundish quick change, record the reading of the old tundish pre-alignment rod on the pre-alignment scale; during the tundish quick change, move the new tundish so that the pre-alignment rod of the new tundish is in contact with the pre-alignment scale, and the reading is consistent with that of the old tundish, thus achieving pre-alignment. The installation positions of the pre-alignment scale and pre-alignment rod are as follows: Figures 2-4 As shown, during the quick change of the tundish, the new tundish nozzle is pre-aligned offline with the inner and outer arcs to ensure that the nozzle is positioned on the extended line of the crystallizer center in the front and rear directions.

[0049] (7) Before pouring from the new tundish, apply silicone to the corner seams of the crystallizer and insert baffles and sheet metal into the crystallizer;

[0050] (8) When the molten steel in the tundish reaches about 8-12 tons, open the stopper rod and start pouring in the tundish. Control the emergence time to 60s. After starting the straightening, control the pulling speed to 0.3m / min and maintain it for 60s to slag. Then, increase the pulling speed to 1m / min at a slope of 0.2m / min2. When the liquid slag height in the crystallizer reaches 15mm, increase the pulling speed to the target pulling speed at a slope of 0.05m / min every 20s.

[0051] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A method for improving the success rate of quick ladle changeover in a slab continuous casting machine, characterized in that, Includes the following steps: (1) Before the final casting of the old tundish, ensure that only liquid slag layer remains in the mold, and control the thickness of the liquid slag layer; When the residual steel in the old tundish is 15-16t, the thickness of the protective slag liquid slag layer in the crystallizer is controlled to be 15±1mm. (2) Before the final casting of the old intermediate ladle, add the casting slag into the crystallizer and make the casting slag fully melt into liquid; (3) After the final casting of the old tundish, pick out the slag ring and slag strip in the crystallizer, and crush the fine slag strips that cannot be picked out and press them into the molten steel to melt, ensuring that there is no crust on the liquid surface and no slag strips on the top of the billet shell; (4) Control the amount of water sprayed in each part of the tension leveling machine when the tension leveling machine is stopped; (5) Increase the lifting speed of the tundish and the traveling speed of the tundish car during the quick change of the tundish, and shorten the time required for the new tundish to travel from the start-up to the predetermined casting position; (6) Set a pre-alignment ruler for quick tundish change on the tundish car, and set a pre-alignment rod at the same position on the old and new tundishes. During the quick tundish change process, perform offline inner and outer arc pre-alignment of the nozzle on the new tundish to ensure that the nozzle is at the position of the extended line of the crystallizer center in the front and rear directions. The pre-alignment ruler is a graduated straight ruler. The installation steps for the pre-alignment ruler and the pre-alignment rod are as follows: a. Place the old tundish on the tundish car platform and center it, confirming that the old tundish nozzle is located at the center of the inner and outer arcs of the crystallizer; b. Install a pre-alignment ruler at any position on the side of the intermediate tundish platform. The pre-alignment ruler is perpendicular to the side where it is installed and parallel to the plane on which the intermediate tundish platform is located. Install a pre-alignment rod on the old intermediate tundish. The pre-alignment rod is perpendicular to the bottom surface of the old intermediate tundish and extends beyond the bottom surface of the old intermediate tundish. The length of the extended portion is not greater than the thickness of the intermediate tundish platform. The pre-alignment rod is installed on the old intermediate tundish at a position corresponding to the position of the pre-alignment ruler, ensuring that the pre-alignment rod can fit against the pre-alignment ruler and that at least one side of the pre-alignment rod falls within the scale range of the pre-alignment ruler. The specific usage method of the pre-alignment scale and pre-alignment rod is as follows: Before the tundish quick change, record the reading of the old tundish pre-alignment rod on the pre-alignment scale; when the tundish is quick changed, move the new tundish so that the pre-alignment rod of the new tundish is in contact with the pre-alignment scale and the reading is consistent with that of the old tundish, thus achieving pre-alignment; c. Confirm the installation position of the pre-alignment marker on the old intermediate tundish, and install the same pre-alignment marker at the same position on the new intermediate tundish; (7) Before pouring from the new tundish, apply silicone to the corner seams of the crystallizer and insert baffles and sheet metal into the crystallizer; (8) After the new intermediate package is started to be poured, control the emergence time, the slope of the straightening and acceleration, and the duration of the straightening and acceleration. The process involves opening the stopper rod when the molten steel in the tundish reaches 8-12 tons, and then starting the pouring process. For a pouring section of 200*1820mm, the emergence time is 30-50 seconds; for 200*2000mm, it's 35-55 seconds; and for 200*2200mm, it's 40-60 seconds. After starting the straightening process, the pulling speed is controlled at 0.3m / min and maintained for 60 seconds to allow for slag formation, after which the pulling speed is increased to 0.2m / min. 2 The slope is increased to 1 m / min. When the liquid slag height in the crystallizer reaches 8-15 mm, the speed is increased by 0.05 m / min every 15-35 seconds to reach the target speed.

2. The method for improving the success rate of quick ladle changeover in a slab continuous casting machine as described in claim 1, characterized in that, The method was applied to the quick change process of the tundish in a 200mm thick slab continuous casting machine.

3. The method for improving the success rate of quick ladle changeover in a slab continuous casting machine as described in claim 1, characterized in that, In step (1), the method to ensure that only liquid slag layer remains in the protective slag in the crystallizer is to use an oxygen-burning pipe to gently stir the center of the molten steel surface, press the solid protective slag floating on the surface of the molten steel into the molten steel, and ensure that the solid protective slag melts in the molten steel.

4. The method for improving the success rate of quick ladle changeover in a slab continuous casting machine as described in claim 1, characterized in that, In step (2), when the remaining steel in the old tundish is 12-15t, starter slag is added to the crystallizer. The addition position is where the old tundish nozzle extends into the crystallizer. When the slab cross-section size is 200*1820-2000mm, 10-15kg of starter slag is added. When the slab cross-section size is 200*2010-2200mm, 15-18kg of starter slag is added.

5. The method for improving the success rate of quick ladle changeover in a slab continuous casting machine as described in claim 1, characterized in that, In step (5), the measures to increase the lifting speed of the medium-sized bag are to adjust the speed of the throttle valve of the hydraulic system of the medium-sized bag and the lifting time of the medium-sized bag; The measure to improve the travel speed of the intermediate ladle is to adjust the reference value of the high-speed motor of the intermediate ladle travel motor, and control the time from starting the new intermediate ladle to the predetermined casting position to be less than 1 minute.

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