METHOD FOR COATING THE BOTTOM OF A STEEL SPOON.

Abstract

The present invention provides a method for coating the bottom of a steel ladle comprising the steps of positioning a mold at the bottom of the steel ladle; securing the mold by means of a clamping mechanism; applying refractory material to the bottom of the ladle and under the mold; applying a load to the mold; and removing the mold from the refractory material. The present invention is advantageous because it enables an increase in the metallic yield of ladles and a reduction in non-metallic inclusions, which are normally carried along by the vortex formed.

Description

METHOD FOR COATING THE BOTTOM OF A STEEL SPOON TECHNICAL FIELD The present invention relates to a method for lining a steel ladle with a specific refractory material by using a mold that fits into the bottom of the ladle. This allows for the induction of characteristic flow lines, improving flow and providing a high steel slip rate. It also reduces vortex and drainage phenomena, thus minimizing slag passage. This results in increased metallic yield from the ladles and a reduction in non-metallic inclusions that are typically carried along by the vortex. FUNDAMENTALS OF THE INVENTION During the steelmaking process, molten metal is poured from the converter into a steel ladle. As illustrated in Figure 1, the ladle consists of a metal frame 1, internally lined with refractories to withstand the high temperatures of the molten steel. The bottom of the ladle 5, made of refractory bricks, has a region for the impact of the steel jet (impact), typically thicker to resist wear; another region containing a refractory piece with a porous plug for argon injection to optimize the metallurgical process; and a third region comprising the flow control system 2, which includes a gate valve that controls the flow of steel. The gate valve consists of two flat plates with a hole, which, when aligned, allow the steel to pass through. In addition, the ladle undergoes metallurgical treatments for chemical and thermal adjustment of the steel. Next, the ladle is attached to the rolling tower, and the hopper valve is opened to allow the steel to flow into the distributor. Due to the irregular shape of the ladle bottom, some of the steel is retained during pouring, preventing the complete flow of liquid steel from the ladle. This results in reduced metal yield, as the retained steel becomes scrap, which will be reprocessed. This problem entails costs related to energy and time expenditures. Another problem that occurs during ladle flow is vortex formation, which increases rolling time and allows slag to enter the distributor. There is also the phenomenon of slag drainage at the end of rolling. Slag drainage causes the slag to collapse in the final minutes of the flow process, preventing the remaining steel from flowing. In view of this, the need arises for the development of technologies that allow for better steel flow, guaranteeing better metallic performance, reduced rework, and improved steel quality (inclusions). Various techniques have emerged over the years to address some aspects of this fluid dynamic problem. Among the many proposals, the most well-known is the stepped brick assembly. This solution involves having steps along the bottom of the ladle, with the area where the steel from the melting furnace falls being at a greater height, and the deepest area being the region of the drawer valve. However, this solution, which is applied in most projects, only partially improves the problem and is not very efficient, as approximately 1 to 4% of the steel is still retained. Another common solution adopted in some steel mills is tilting the ladle during rolling. This tilt allows much more of the molten steel to drain, increasing the height of the metal column and preventing some of the suction of floating slag. This solution is not very safe, as it requires tilting the ladle using a metal wedge, and it also hinders the handling of the long pipe that directs the molten steel to the distributor. Documents Pl 0307454-4 and W02003072285A1 frAocnn / zznz / E / GALA propose a new solution for reducing the metal retained at the bottom of the ladle and the slag flow through the slag valve system. The solution consists of terraces at different levels above the slag valve, which is located at the bottom of the ladle. These terraces are described as horizontal and serve to retain some of the floating slag. Below the terraces are sloping bottoms that increase the height of the molten metal column, causing it to flow preferentially to the slag valve. The area above the slag valve, called the well, serves as a molten metal reservoir, increasing the metal's residence time in the region and preventing slag carryover. The same solution may also include a set of several bevels, described as bevels.This type of solution is also described in document US 5196051. In this way, the formation of the vortex would be avoided. However, these documents do not present fluid dynamic studies to verify this claim. US patent 4746102 proposes another type of ladle bottom, consisting basically of an inclined ramp for the drawer valve chamber. This solution allows for significant drainage of the molten metal; however, it does not guarantee a reduction in slag passage during leakage due to vortex entrainment and drainage effects. bAocnn / zznz / E / YiAi State-of-the-art documents do not describe in detail the manufacturing process of these funds, indicating that known solutions consist of prefabricated parts that are fitted together at the installation site. Current technologies claim to increase metal yield or even reduce slag passing, but they lack scientific evidence (such as water-based or numerical models) demonstrating how this can occur. They are merely empirical proposals based on interpretations of the phenomena involved. Therefore, such a solution would require further research to guarantee these improvements. Therefore, the prior art lacks a solution capable of providing a steel ladle bottom liner that improves the steelmaking process, is practical to install, and can be carried out on-site. Furthermore, the prior art does not offer a solution capable of providing a ladle bottom liner that maintains the same characteristic profile throughout its service life. OBJECTIVES OF THE INVENTION It is an objective of the present invention to provide a method for developing a coating for a monolithic ladle bottom (refractory concrete), through the use of a metal mold, with a characteristic profile, with the objective of improving the flow of liquid steel, allowing greater sliding of the steel and reducing the passage of slag. Another objective of the present invention is to develop a lining comprising inclined channels connecting the extreme points of the ladle, smoothly directing the flow to the gate valve system. The channels can be inclined to form curved or straight profiles. The channel inclination allows for the acceleration of the steel flow, which aids in supporting the slag in the gate valve chamber and contributes to vortex breaking. Furthermore, it is an objective of the present invention to propose the construction, during concrete pouring in the facility, of barriers near the gate valve system. These barriers serve to break the characteristic circular motion of the vortex. These barriers, herein called bevels, are either created during the concrete pouring process or are prefabricated and inserted in the facility. SUMMARY DESCRIPTION OF THE INVENTION To achieve the above objectives, the present invention provides a method for lining the bottom of a steel ladle comprising the steps of positioning a mold at the bottom of the steel ladle; securing the mold by means of a clamping mechanism; applying refractory material to the bottom of the ladle and under the mold; applying a load to the mold; and removing the mold from the refractory material. BRIEF DESCRIPTION OF THE FIGURES Figure 1 illustrates a cross-section of a steel spoon. Figure 2 shows a cross-sectional view of a steel spoon with a spoon bottom according to an embodiment of the present invention. Figure 3 illustrates the profile regions of different configurations according to the present invention; Figure 4 shows another modality of the steel ladle bottom lining according to the present invention; Figure 5 shows a mold according to the present invention. Figure 6 shows the cross-section of one end of a mold according to the present invention. Figure 7 shows a longitudinal section of the mold and a coupling system in the drawer valve according to the present invention. Figure 8 shows a support system for the mold according to the present invention. Figure 9 shows another modality of the spoon bottom according to the present invention. Figure 10 shows another modality of the spoon bottom according to the present invention. Figure 11 shows another modality of the spoon bottom according to the present invention. Figure 12 illustrates a prefabricated part according to a modality according to the present invention. DETAILED DESCRIPTION OF THE INVENTION The following description will begin with preferred embodiments of the invention, applied to a steel ladle bottom. However, as will be evident to a person skilled in the art, the invention is not limited to any particular embodiment, nor to a specific method of coating a steel ladle. As previously mentioned, Figure 1 illustrates a steel ladle used in the steelmaking process. The ladle comprises a ladle bottom 1 made of refractory material. Additionally, the ladle includes a valve seat 2 shaped like a drawer valve, allowing the steel to drain. In general, the bottom of the ladle has a section that receives the steel stream from the converter. This section has the greatest refractory thickness and is therefore located at the highest point of the ladle bottom. From this section, the molten steel spreads throughout the rest of the ladle until the level rises. However, in some areas of the ladle, insufficient steel flow occurs. To address this problem, a lining is proposed to improve steel flow. Figure 2 illustrates a first embodiment of a steel ladle bottom lining according to the present invention applied to a steel ladle comprising an impact region 16 and a valve seat 2. The ladle bottom lining according to the present invention has a characteristic imprinted profile that is determined to form characteristic flow channels that are formed due to the variation in thickness of the profile that extends from a region of greater thickness to a region of lesser thickness of the ladle bottom. In this configuration, where the ladle bottom comprises only an impact piece 16 and a valve seat 2, the mold has a C-shape. One end projects substantially circularly from a point adjacent to one side of the impact region 16 in the thicker region onto the ladle bottom, passing through the valve seat 2 in the thinner region, to a point adjacent to the opposite side of the impact region 16 in the thicker region. This shape allows the dead zones near the impact region 16 in the thicker region to be interconnected to the outlet valve in the thinner region. Depending on the arrangement of the drawer valve in relation to the other regions of the ladle, the profile shape may vary, in order to optimize as much as possible and eliminate dead zones that could store steel in the ladle. The printed profile must eventually have a different characteristic shape to improve flow, depending on the type of ladle used. For example, the ladle may have a second outlet valve region, through which the steel is emptied for rolling. Some ladles may also have a porous plug, commonly used for inert gas injection to improve steel refining. In this way, it was verified that the ideal is for the mold to occupy or promote coverage of the largest possible area of ​​the ladle bottom (excluding the impact region). This ensures maximum coverage of the dead zones, allowing the capture of the metallic steel that would not be converted through the valve seat. The mold thus creates depressions, interconnecting the common points with the drawer valve region. Figure 3 illustrates the regions of the ladle bottom that can be occupied by the profile under different configurations, taking into account the position of the impact region 16, the valve seat 2, and the porous plug 19. Considering the different ladle bottom configurations, two important regions can be identified: the useful improvement region 17, which is the area where the new profile will be positioned to improve flow, with the point furthest from the valve seat 2 being the zero point, from which the bottom thickness decreases towards the seat, creating a region of greater depth. Another important region is the critical region 18, representing the area where the valve seat 2 and the porous plug 19 can be located. In the case that the spoon does not have a porous plug 19 the final design is direct, i.e., the distant points are interconnected with the valve seat 2 with a C-shaped profile as in Figure 2. If the ladle bottom has a porous plug, the profile must be adapted to prevent the characteristic path from passing over the porous plug. Figure 4 illustrates an embodiment of the invention used when the ladle bottom has a plug 19 between the end points of the profile, thus requiring a deviation around the plug 19. In other words, the characteristic profile used in the mold must be able to form characteristic curves that contour the porous plug 19, keeping it within the thickest region of the ladle bottom. To create the coating for the steel ladle, the use of mold 3, as exemplified in Figure 5, is proposed. As can be seen, mold 3 has a box-like shape, preferably curvilinear, whose cross-sectional form corresponds to the profile to be imprinted on the ladle bottom. In this configuration, mold 3 has a profile 10, corresponding to the profile illustrated in Figure 2. This curvilinear profile prevents the occurrence of stress concentrators in the concrete 5. Furthermore, it was verified that the curved shape also helps reduce pressure loss from runoff in the region closest to the impact zone. However, the mold can be manufactured with corner shapes, having a trapezoidal or slightly inclined straight shape at its edges. Additionally, the mold has a thickness that varies along its length, corresponding to the desired height variation at the bottom of the ladle to improve steel flow. Figure 6 illustrates a cross-section of one end of the mold, as shown in Figure 5, where the height variation can be observed. In addition to this, mold 3 comprises in its upper region a system for its fixing and support, and, in its lower region, a fixing system and hatches for concreting that will be described later. At the start of the lining process, ladle 1 is released for refractory reformation. Next, mold 3 is inserted from above, via an overhead crane, and positioned on the bottom of the steel ladle 1 to couple to the valve 2, to connect end points of the steel ladle to the drawer valve system 2. Mold 3 is then secured for the lining process. Preferably, mold 3 is fitted into the valve seat 2, at the bottom of the steel ladle 1. Next, the refractory material 5 is applied to the bottom of the ladle 1, filling the space below the mold 3, to form the lining with the characteristic profile according to the present invention. Preferably, the refractory material used is refractory concrete. To ensure the desired profile is achieved, it is proposed to partially fill the interior of mold 3, creating a hollow or concave section with a load 4. This load 4 can be made from the concrete itself or even filled with the same material as the mold (steel, fiber, wood, etc.), provided it gives the structure sufficient weight. This action helps to counteract the thrust force of the concrete 5 being molded. Since mold 3 is made in a box-like format 10, meaning it is hollow, the thrust generated would be very strong, potentially breaking the mold's locking mechanism. Therefore, it is necessary to calculate the partial volume to be filled 4 to ensure the balance between the weight of the mold and the thrust force generated by the concrete. Mold 3 is inclined to create a profile that allows preferential flow of the steel through it. The zero point of the mold should be as far as possible from the valve seat 2, allowing steel to be captured from dead zones. From the zero point, there is a difference in depth relative to the valve seat 2. In other words, there are two preferential levels of concrete height, generated by the profile of mold 3. This difference in height allows flow through the channel formed by mold 3, capturing steel from distant points in a region of greater thickness and generating preferential flow in the direction frAocnn / zznz / E / GALA towards valve 2 in a region of lesser thickness. The accelerated flow generated produces a lifting force for the slag for a longer period, preventing drainage. To improve the application of the refractory material and the shaping of the steel ladle bottom, it is necessary to keep the mold fixed until the refractory material has set. In this regard, the method according to the present invention provides a fixing mechanism. According to Figure 7, mold 3 is fixed and locked in the valve seat 2. In the center of the valve, a central pin 6 is inserted, which fits into mold 3, which through a fixing system 9 will be locked to prevent movement of mold 3 during concreting. Preferably, as seen in Figure 8, the mold has a support point 11 to prevent stress on the tips of the mold 3 due to the weight generated by the internal rocking provided by the load 4. Preferably, the support point 11 is simply formed by an extension or projection of the body of the mold 3 itself, with a central eyelet to allow the passage of a support pin 12. However, the support point can be formed by a piece fitted or coupled to the mold to allow fixing with the pin 12. bRocnn / zznz / E / YiAi In this way, the support system allows the mold to remain level during load application. To allow for ideal height adjustment, pin 12 has holes 13 that allow for adjustment during fixing and preparation for applying the refractory material, and then the mold is supported at the bottom of the ladle. Once the concrete pouring is complete, the support pin 12 is removed, taking care to vibrate the concrete and avoid voids. The height adjustment system can alternatively utilize any other system that allows for height adjustment, such as a threaded system, which is turned to raise the form. Thus, the present invention provides a method that allows a practical installation that can be applied directly to a steel ladle bottom, enabling improvement during the steelmaking process. Preferably, the lining base according to the present invention may include an anti-vortex system to prevent the formation of the vortex phenomenon. For this purpose, the mold 3, as shown in Figure 5, may comprise open points or hatches 20, positioned near the opening corresponding to the valve seat, which allow the concrete to rise during pouring. More specifically, with the use of the hatches 20, during pouring, the concrete level rises at these open points, forming bevels. At this stage, external vibrators may be used to ensure homogenization of the concrete. In this way, the bottom lining of the ladle will comprise, in addition to the characteristic printed profile, the anti-vortex system formed by bevels 14 and 15 near the valve seat, which generate a disturbance of the flow thus preventing the formation of a vortex. As previously mentioned, the vortex is a fluid-dynamic phenomenon that can draw slag into the valve. The anti-vortex system may comprise at least one bevel 14, and preferably, the system comprises two bevels 14 and 15. Thus, the present invention provides a method and a ladle bottom lining capable of increasing steel slippage and preventing the occurrence of the vortex phenomenon. Figures 9, 10, and 11 illustrate other embodiments of the invention in which the lining method is applied to different ladle bottoms. Each lining bottom comprises an anti-vortex system, characteristic flow channels, and a pre-molded impact piece 16. The impact piece is raised higher than the bottom, aiding the flow of the steel. The piece has a convex edge, which facilitates flow at the end of the ladle and prevents breakage caused by sharp edges. The piece is pre-formed by special molding, cured, and dried in a controlled environment. This process aims to obtain a high-strength pre-molded component for use in the impact zone (highest mechanical stress). It can be seen that each of the bottoms presented in Figures 9 to 11 have different profiles, but they are within the corresponding regions illustrated in Figure 3. Thus, to create the mold for each bottom, a mold with a different characteristic profile must be used to create the desired profile in each situation. Thus, the present invention provides a method for ladle bottom lining and a mold that allows for simpler forming, either on-site or for the manufacture of a prefabricated part, possessing a format capable of improving the steelmaking process. Specifically, Figure 11 illustrates an embodiment of the present invention applied to a ladle bottom comprising an impact region 16, a valve seat 2, and a porous plug 19. In this configuration, the impact region 16 is positioned against the wall of the steel ladle, and the valve seat 2 is positioned adjacent to one side of the impact region. The porous plug 19 is positioned near the other side of the impact region. The profile used thus has an end closer to the porous plug 16 and extends to the valve seat 2. Furthermore, for better utilization, the profile has a large area to reach the maximum number of dead zones. In this way, the steel can flow from the region near the porous plug 19 to the valve seat. To reduce vortex effects, chamfers 14 and 15 are installed near the valve seat 2. Figure 12 illustrates an embodiment of the present invention applied to a steel ladle configured such that the porous plug 19 is positioned adjacent to the impact region 16 and the valve seat 2 is close to a wall of the steel ladle. In this case, the profile has a C-shape as in the first embodiment of the invention, where its ends are each positioned on one side of the impact region 16. It is also noted that the profile passes around the porous plug 19. In addition to providing a simple and practical method for coating the bottom of ladles on-site, the present invention enables the manufacture of prefabricated parts. Mold 3 can be applied to a pre-molded part with a printed profile, which can then be installed in the desired location. Thus, it is verified that the present invention enables a simple and practical method for improving the utilization of steel in ladles with various configurations. Furthermore, it can be verified that the present invention is advantageous both in the application of the coating at the installation site and in the manufacture of prefabricated parts. The advantage of the present invention was observed in experiments on a 1 / 8 scale physical model, in which the flow was simulated using water as the fluid. It was noted that the preferential flow generated by the curved channels, at the end of the water drainage, resulted in a lifting force that prevented surface collapse (drainage phenomenon). The normal flow lines are pulled from various directions, including from the surface (slag). By creating the curved cavities in the bottom, there is preferential acceleration from the periphery to the valve seat 2. In the physical model experiments, using water as the fluid similar to steel, the two configurations were compared: the straight bottom (current) and the bottom proposed by the present invention. Through the analysis of the water flow through the valve, the moment of formation of the drainage phenomenon was observed. At this instant, the volume of water retained in the scoop is marked. The bottom proposed by the present invention obtained a 75% reduction in the volume of water retained in the spoon, which will have an impact on the increase in metal yield. Another advantage of the present invention relates to the type of surface wear during ladle operation. A problem observed in other patent documents described above is how to guarantee the same design until the end of the refractory lining's lifespan. Having curved cavities 10 encourages a preferential flow of water into them during model testing, resulting in preferential wear in the cavities and thus ensuring a consistently curved bottom shape. In other words, the solution proposed by the present invention tends to maintain the same function until the end of the lining's lifespan. Therefore, the present invention provides a method for lining the bottom of a steel ladle that allows for an installation capable of improving the steelmaking process and that is practical to install and can be carried out on-site. Numerous variations are permitted, affecting the scope of protection of the present invention. This reinforces the fact that the present invention is not limited to the specific configurations or embodiments described above.

Claims

1. A method for lining the bottom of a steel ladle characterized by comprising the steps of: positioning a mold (3) at the bottom of the steel ladle (1); fixing the mold (3) by means of a fixing mechanism; applying refractory material (5) on the bottom of the ladle and under the mold (3); applying a load (4) on the mold (3); and removing the mold (3) from the refractory material (5).

2. Method according to claim 1, characterized in that the refractory material is refractory concrete.

3. Method according to claim 1 or 2, characterized in that the mold has an inclination and a straight or curved profile.

4. Method according to any of claims 1 to 3, characterized in that the step of fixing the mold by the fixing mechanism comprises supporting the mold in the valve seat at the bottom of the ladle and locking the structure to prevent movement during the application of the load.

5. Method according to any of claims 1 to 4, characterized in that the load applied to the mold is formed by the refractory material or other material whose quantity partially fills the mold to compensate for the thrust resulting from the refractory material under the mold.

6. Method according to any of claims 1 to 5, characterized in that it further comprises the step of forming bevels around an outlet valve at the bottom of the ladle by means of hatches in the bottom of the mold during the application of refractory material.

7. Steel ladle bottom characterized in that it is formed by a refractory material lining (5) and comprising a profile that extends from a region of greater thickness to a region of lesser thickness, and wherein an outlet valve (2) is positioned in the region of lesser thickness of the refractory bottom.

8. Steel spoon bottom according to claim 7, characterized in that it comprises an impact region (16) and the ends of the profile are located near the impact region.

9. Steel ladle bottom according to claim 7 or 8, characterized in that the profile extends from two distant ends of the outlet valve (2) positioned in the thickest region.

10. Steel spoon bottom according to any of claims 7 to 9, characterized in that it comprises at least one bevel (14, 15) positioned around the valve seat (2) in the region of lesser thickness.