Steel pot bottom and method for coating a steel pot bottom

Abstract

The present invention provides a method for coating the bottom of a steel pot, comprising the steps of placing a mold on the bottom of the steel pot, securing the mold with a clamping mechanism, attaching refractory material to the bottom of the steel pot and below the mold, applying a load to the mold, and removing the mold from the refractory material. The present invention is effective because it allows for increased metal yield in the pot and reduced non-metallic inclusions that would normally be entrained by the formed vortex.

Description

[Technical Field]

[0001] The present invention relates to a method for coating a steel ladle with a concrete refractory material using a mold attached to the bottom of the ladle, which allows for improved flow by introducing characteristic flow lines, increasing the steel reduction rate, reducing the phenomena associated with vortices and drains, and reducing slag passage, resulting in an improved metal yield in the ladle and a reduction in non-metallic inclusions that would normally be entrained by the formed vortices. [Background technology]

[0002] During the steelmaking process, molten metal is tapped from a converter into a steel ladle. As shown in Figure 1, the ladle is a piece of equipment consisting of a metal casing 1, the interior of which is lined with refractory material to withstand the high temperatures generated by the molten steel. The bottom of the ladle 5, made of refractory bricks, typically has an area for the molten steel jet (impact) to be injected, which is thickened to withstand wear, another area containing refractory products with porous plugs for argon injection to optimize the metallurgical process, and a flow control system 2 including a gate valve to control the passage of the molten steel. The gate valve consists of two flat plates with holes that, when aligned, allow the passage of molten steel.

[0003]

[0003] The ladle then undergoes metallurgical treatment, which involves chemical and thermal conditioning of the steel. The ladle is then attached to a caster tower, and the gate valve is opened to allow the molten steel to flow into a distributor. Due to the irregular shape of the ladle bottom, some of the molten steel remains when emptying, and not all of the molten steel can flow out of the ladle. This residual molten steel thus becomes scrap that will be reprocessed, resulting in a reduced metal yield. This problem represents costs associated with energy and time consumption.

[0004]

[0004] Another problem that can occur during tapping from the ladle is the formation of vortices, which can lengthen the casting time and cause slag to flow into the distributor, and also the formation of drainage at the end of the casting, which causes the slag to collapse during the last few minutes of the flow process and block the flow of the remaining molten steel.

[0005]

[0005] Therefore, there is a need for technological developments that improve the flow of molten steel, increase metal yield, reduce rework, and improve the quality (inclusions) of steel.

[0006]

[0006] Several technologies have emerged over the years to counteract some of this hydrodynamic problem. The best-known of the various proposals is the brick staggering. This solution involves creating a step along the bottom of the ladle, elevating the drop point of the molten steel from the melting furnace and making the gate valve area the deepest. However, this solution, as applied in most projects, is not very efficient, as it only partially improves the problem and approximately 1-4% of the steel still remains.

[0007]

[0007] Tilting the ladle during casting is another common solution employed by some steel mills. This tilting allows for more molten steel to be discharged, increases the height of the metal column, and avoids some of the slag suction that floats to the surface. This solution is unsafe because it requires the use of metal shims to tilt the ladle, and it also hampers the handling of the long tubes that conduct the molten steel to the distributor.

[0008]

[0008] References PI0307454-4 and WO2003072285 propose a novel solution to reduce metal accumulation at the bottom of the ladle and slag passing through the gate valve system. This solution consists of terraces at different levels, each with a gate valve at the bottom of the ladle. According to the description, these terraces are horizontal and serve to trap some of the slag floating on the surface. Below the terraces, the base is sloped, thereby increasing the height of the molten metal column and allowing the molten metal to flow preferentially into the gate valve. The area above the gate valve, known as the sump, serves as a reservoir for the molten metal, increasing its residence time in that area and preventing slag entrapment. The same solution may also include a set of chamfers, described as recesses. This type of solution is also described in U.S. Pat. No. 5,196,051. In this way, vortex formation is prevented. However, these documents do not present any fluid dynamics studies to support this claim.

[0009]

[0009] U.S. Patent No. 4,746,102 proposes another type of ladle bottom, which basically consists of a slope up to the gate valve position. This solution allows a large amount of molten metal to be discharged, but does not guarantee a reduction in the passage of slag during tapping due to the entrainment (vortex) and drainage effects.

[0010]

[0010] The state-of-the-art literature does not describe these background manufacturing processes in detail, and so known solutions are presented as consisting of pre-made products that are installed at the installation site.

[0011]

[0011] Techniques already known from the state of the art claim to be able to improve metal yield or even reduce slag passing, but they do not provide scientific evidence (water models or numerical models) of how this can happen. They are merely empirical suggestions based on an interpretation of the phenomena involved. In other words, such solutions require more experience to guarantee such improvements.

[0012]

[0012] Thus, the state of the art lacks a solution that can improve the steelmaking process and provide a steel ladle bottom coating that is practical to install and can be performed in the field. Furthermore, the state of the art does not offer a solution that can provide a ladle bottom coating that has the same characteristic profile throughout its entire service life. Summary of the Invention [Problem to be solved by the invention]

[0013]

[0013] The object of the present invention is to provide a method for developing a one-piece pot bottom coating (refractory concrete) with a distinctive profile using a metal mold, with the aim of improving the flow of molten steel, resulting in more molten steel discharge and less slag passing through.

[0014] A further object of the present invention is to develop a coating with angled channels connecting the ends of the ladle to smoothly direct the flow to the gate valve system. The channel angle can be formed into a curved or straight profile. The channel angle allows for acceleration of the molten steel flow, which helps to maintain the slag at the gate valve and partially breaks down the vortex.

[0015]

[0015] A further object of the present invention is to propose the installation of a barrier near the gate valve system during on-site concrete casting, the barrier having the function of breaking up the circular motion characteristics of the vortex. Here, this barrier is called a chamfer and can be made during concrete casting or preformed and inserted on-site. [Means for solving the problem]

[0016]

[0016] In order to achieve the above-mentioned object, the present invention provides a method for coating the bottom of a steel pot, which includes the steps of placing a mold on the bottom of the steel pot, fixing the mold with a clamping mechanism, attaching refractory material to the bottom of the steel pot and below the mold, applying a load to the mold, and removing the mold from the refractory material. [Brief explanation of the drawings]

[0017] [Figure 1] A cross section of a steel pot is shown. [Figure 2] 1 is a cross-sectional view of a steel pot having a pot bottom according to an embodiment of the present invention. [Figure 3] 10 shows different configurations of profile regions according to the present invention; [Figure 4] 3 shows another embodiment of a steel ladle bottom coating according to the present invention. [Figure 5] 1 shows a mold according to the present invention. [Figure 6] 1 shows a cross section of one end of a mold according to the present invention. [Figure 7] 1 shows a longitudinal section of a mold and joining system in a gate valve according to the invention. [Figure 8] 1 shows a support system for a mold according to the present invention. [Figure 9] 3 shows another embodiment of the pot bottom according to the present invention. [Figure 10] 3 shows another embodiment of the pot bottom according to the present invention. [Figure 11] 3 shows another embodiment of the pot bottom according to the present invention. [Figure 12] 1 shows a ready-made product according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018]

[0029] The following description begins with a preferred embodiment of the invention as applied to the bottom of a steel pan, however, as will be apparent to those skilled in the art, the invention is not limited to any particular aspect, nor is it limited to any particular method of coating a steel pan.

[0019]

[0030] As already mentioned, Figure 1 shows a diagram of a steel ladle used during the steel making process. The ladle comprises a ladle bottom 1 made of refractory material. Furthermore, the ladle comprises a valve seat 2 formed as a gate valve for the flow of molten steel.

[0020]

[0031] Generally, the bottom of the ladle has the thickest refractory material and is therefore located at the highest point of the ladle. From this point, the molten steel spreads to other parts of the ladle, causing the molten steel level to rise. However, in some areas of the ladle, the molten steel does not flow sufficiently. To solve this problem, coating backgrounds have been proposed to improve the drainage of molten steel.

[0021]

[0032] 2 shows a first embodiment of a steel pot bottom coating according to the present invention applied to a steel pot having an impact area 16 and a valve seat 2. The pot bottom coating according to the present invention has a printed characteristic profile determined to form a characteristic flow path formed due to the thickness variation of the profile extending from a thicker region to a thinner region of the pot bottom.

[0022]

[0033] In this embodiment, where the pot bottom comprises only the impact receiving portion 16 and the valve seat 2, the mold is C-shaped with an end that projects from a point adjacent to the side of the impact area 16 in the thicker region, in a substantially circular shape, over the pot bottom, through the valve seat 2 in the thinner region, and to a point adjacent to the opposite side of the impact area 16 in the thicker region. This allows the dead zone near the impact area 16 in the thicker region to be interconnected with the outlet valve in the thinner region.

[0023]

[0034] Depending on the placement of the gate valve relative to other areas of the ladle, the profile shape can be varied to optimise as much as possible and to eliminate dead zones that could trap molten steel within the ladle.

[0024]

[0035] The printed profile will ultimately have different characteristic shapes to improve flow depending on the type of ladle used. For example, the ladle may have a second outlet valve area through which the molten steel leaks into the casting. Some ladles may also have porous plugs, commonly used for inert gas injection to improve steel refining.

[0025]

[0036] Therefore, it was found that the mold should ideally occupy or cover as much of the bottom of the pot as possible (excluding the impact area). This maximizes coverage of the dead zone and allows for the capture of any metal that does not pass through the valve seat. In this way, the mold creates a recess that interconnects the gate valve area and the common area.

[0026]

[0037] Figure 3 shows the areas of the pot bottom that can be occupied by profiles with different configurations, taking into account the locations of the impact area 16, the valve seat 2, and the porous plug 19. Considering the different configurations of the pot bottom, two critical areas can be considered: the useful improvement area 17, where new profiles for flow improvement can be placed; the zero point, located furthest from the valve seat 2, from which the thickness of the bottom decreases to the valve seat, creating a deeper area. Another highlighted area is the critical area 18, which represents the area where the valve seat 2 and porous plug 19 can be placed.

[0027]

[0038] If there is no porous plug 19 in the pan, the final design is simple, i.e., a C-shaped profile interconnects the valve seat 2 and the remote points as in FIG.

[0028]

[0039] If there is a porous plug in the bottom of the pot, the profile must be tailored so that the characteristic path does not pass over the porous plug. Figure 4 shows an embodiment of the invention used when the bottom of the pot has a plug 19 between the endpoints of the profile, requiring offsetting around the plug 19. In other words, the characteristic profile used for the mold must be able to create a characteristic curve that bypasses the porous plug 19 to keep it within the thicker region of the pot bottom.

[0029]

[0040] For coating steel pans, it is proposed to use a mold 3 as illustrated in FIG. 5. As can be seen, the mold 3 preferably has a curved, box-like shape, the cross-sectional shape of which corresponds to the profile to be printed on the bottom of the pan. In this embodiment, the mold 3 has a profile shape 10 corresponding to the profile shown in FIG. 2. This curved profile prevents stress concentrations from occurring in the concrete 5. Furthermore, it has been found that the curved shape also helps to reduce the head loss of the flow in this area closest to the impact zone. However, the mold can also be manufactured with corner shapes with slightly beveled edges, such as trapezoidal or straight-type shapes.

[0030]

[0041] Additionally, the mold has a thickness that varies along its length and corresponds to the height variations that are desirable to apply to the bottom of the ladle to improve the flow of molten steel. Figure 6 is a cross section of one end of the mold from Figure 5, where the height variations can be seen.

[0031]

[0042] In addition, the mould 3 is provided in its upper area with a system for its fixing and support, and in its lower area with a fixing system and hatches for concrete pouring, which will be described later.

[0032]

[0043] At the start of the coating process, the pot 1 is freed up for refractory modification.

[0033]

[0044] Next, the mold 3 is inserted from above by a crane and placed on the bottom of the steel ladle 1 and connected with the valve 2 so that the end points of the steel ladle are connected to the gate valve 2 system.

[0034]

[0045] The mould 3 is then clamped to create the coating. Preferably, the mould 3 is attached to the valve seat 2 at the bottom of the steel ladle 1.

[0035]

[0046] A refractory material 5 is then applied to the bottom of the pot 1, filling the space below the mold 3, so as to adapt the coating to the characteristic profile according to the invention. Preferably, the refractory material used is refractory concrete.

[0036]

[0047] To ensure the desired profile is achieved, it is proposed to create a hollow or recessed area in the mold 3 and partially fill it with a load 4. The load 4 can be made of concrete itself or even filled with the same material as the mold (steel, fiber, wood, etc.), as long as it provides sufficient weight for the structure. This compensates for the buoyancy of the concrete 5 being cast. Since the mold 3 is in the form of a box 10, i.e., hollow inside, the generated buoyancy can be so great that it could destroy the mold clamping mechanism. Therefore, the partial volume 4 to be filled must be calculated to ensure that the weight of the mold is balanced against the buoyancy generated by the concrete.

[0037]

[0048] Mold 3 has a sloped section that allows the molten steel to form a profile that allows preferential flow. The zero point of the mold should be as far away from valve seat 2 as possible, so that the molten steel can be captured from the dead zone. There is a difference in depth from the zero point relative to valve seat 2. In other words, there are two preferential levels of concrete height created by the profile of mold 3. This height difference allows the concrete to flow through the channel created by mold 3, capturing molten steel from distant locations in the thicker areas and generating preferential flow toward valve 2 in the thinner areas. The generated accelerated flow creates a force that maintains the slag for a longer period of time, avoiding the drain phenomenon.

[0038]

[0049] To improve the application of the refractory and the shaping of the steel pan bottom, it is necessary to keep the mold clamped until the refractory has been shaped. In this regard, the method according to the invention provides for the use of a clamping mechanism.

[0039]

[0050] According to Figure 7, the mould 3 is clamped and locked to the valve seat 2. A central pin 6 is inserted into the centre of the valve, which is connected to the mould 3, which is locked by a clamping system 9 so that it does not move during concrete pouring.

[0040]

[0051] Preferably, as can be seen in Figure 8, the mould has a fulcrum 11 to avoid stress on the mould tip 3 due to the weight caused by the internal balance provided by the load 4. Preferably, the fulcrum 11 is simply formed by an extension or protrusion of the body of the mould 3 itself, with a small hole in the centre for the passage of a support pin 12. However, the fulcrum could also be formed by a part fitted or attached to the mould so that it can be fixed by the pin 12.

[0041]

[0052] The support system thus allows the mould to be kept level during loading. To allow for optimal height adjustment, the pins 12 have holes 13 which allow adjustment during clamping and preparation for the application of the refractory material, after which the mould is supported by the pot bottom.

[0042]

[0053] Once the concrete is complete, the support pins 12 are removed, taking care to avoid voids and vibrate the concrete. Alternatively, the height adjustment system can be any other system that allows for height adjustment, such as a screw system that rotates to raise the mold.

[0043]

[0054] The present invention therefore provides a practical installation that can be applied directly to the bottom of the steel ladle, allowing for improvements during the steel making process.

[0044]

[0055] Preferably, the coating background according to the present invention may include a vortex prevention system to prevent the formation of vortex phenomena. For this purpose, the mold 3 may be provided with an opening or hatch 20, as seen in FIG. 5, located near the opening corresponding to the valve seat, allowing the concrete to rise during concrete pouring. More specifically, the hatch 20 allows the concrete level to rise at this opening during concrete pouring, forming a chamfer. At this stage, an external vibrator can be used to ensure the concrete is homogenized.

[0045]

[0056] In addition to the printed characteristic profile, the coating on the bottom of the pot will have an anti-vortex system formed by chamfers 14 and 15 near the valve seat, which create flow disturbances and prevent the formation of vortices.

[0046]

[0057] As previously mentioned, a vortex is a hydrodynamic phenomenon that can suck slag into the valve. The anti-vortex system can include at least one chamfer 14, and preferably the system includes two chamfers 14 and 15. Thus, the present invention provides a method and a ladle bottom coating that can increase the flow of molten steel and prevent the occurrence of the vortex phenomenon.

[0047]

[0058] Figures 9, 10 and 11 show other applications of the coating method of the present invention to different ladle bottoms. Each coated bottom is equipped with a vortex breaker system, distinctive flow channels and a pre-formed impact bearing 16. The impact bearing is located higher than the bottom and aids the flow of molten steel. The edges of the impact bearing are convex, which promotes flow at the edges of the ladle and prevents breakage caused by sharp corners. The impact bearing is produced by pre-forming into a special shape, which is then hardened and dried in a controlled environment. The aim of this work is to obtain a high-strength precast (higher mechanical requirements) for use in the impact area.

[0048]

[0059] Note that each background shown in Figures 9-11 has a different profile, but falls within the corresponding region shown in Figure 3. Therefore, when molding each background, a mold with a different characteristic profile must be used to create the desired profile in each situation.

[0049]

[0060] Thus, the present invention provides a method of pot bottom coating and a mold having a shape that can improve the steelmaking process and that can be more easily formed, either on-site or pre-fabricated.

[0050]

[0061] Specifically, FIG. 11 shows an embodiment of the present invention applied to the bottom of a ladle with an impact area 16, a valve seat 2, and a porous plug 19. In this configuration, the impact area 16 is located adjacent to the wall of the steel ladle, and the valve seat 2 is located adjacent to one side of the impact area. The porous plug 19 is located adjacent to the other side of the impact area. In this way, the profile used has an end closer to the porous plug 16 and extends to the valve seat 2. Furthermore, for more efficient use, the profile has a large area to maximize the number of dead zones. In this way, molten steel can flow from the area near the porous plug 19 to the valve seat. Chamfers 14 and 15 are installed near the valve seat 2 to reduce the effects of vortices.

[0051]

[0062] 12 shows an embodiment of the present invention applied to a steel pan in which a porous plug 19 is positioned adjacent to the impact region 16 and the valve seat 2 is configured to be adjacent to the wall of the steel pan. In this case, the profile is C-shaped, as in the first embodiment of the present invention, with each end positioned on one side of the impact region 16. Note also that the profile passes around the porous plug 19.

[0052]

[0063] In addition to providing a simple and practical method for coating the bottom of a pot on site, the present invention also allows for ready-made production: the mold 3 can be applied to the preform on which the profile will be printed and then placed in the desired position.

[0053]

[0064] It can thus be seen that the present invention allows for a simple and practical method for improving steel utilization in pans of various configurations. Furthermore, the present invention can be seen to be effective in both in-situ coating applications and pre-fabricated manufacturing.

[0054]

[0065] The advantages of the present invention were observed in experiments using a 1 / 8-scale physical model simulating flow using water as a similar fluid. Furthermore, the preferential flow generated by the curved flow path was observed to exert a sustaining force that prevented the surface from collapsing at the final stage of water emptying (the drain phenomenon). Conventional flow lines pull from various directions, including the surface (slag). Creating a curved cavity at the bottom results in preferential acceleration from the periphery toward the valve seat 2. In physical model experiments using water as the molten steel-like fluid, two configurations were compared: a straight bottom (current) and the bottom proposed by the present invention. By analyzing the water flowing through the valve, the moment of drain formation was observed. The amount of water remaining in the ladle at this moment was recorded. With the proposed background, the amount of water remaining in the ladle was reduced by 75%, which has an impact on improving metal yield.

[0055]

[0066] Another advantage of the present invention relates to the type of surface wear during ladle operation. One problem observed in the previously mentioned patents is how to ensure the same design throughout the life of the refractory coating. Having a curved cavity 10 allows for preferential flow within the cavity during water model testing. This results in preferential wear within the cavity, ensuring a consistently curved bottom shape. In other words, this type of solution proposed by the present invention helps maintain the same functionality throughout the life of the coating.

[0056]

[0067] Thus, the present invention provides a method of coating the bottom of a steel ladle that allows for installation that can improve the steel manufacturing process, is practical to install, and can be performed on-site.

[0057]

[0068] Many variations are possible within the scope of protection of the present invention, and it is therefore emphasized that the present invention is not limited to the above-mentioned specific configurations or embodiments.

Claims

1. 1. A method for coating the bottom of a steel pan, comprising: placing a mold (3) on the bottom of a steel ladle (1), the bottom of the steel ladle having a profile extending from a thicker region to a thinner region and an impact region (16) in the thicker region; Fixing the mold (3) by a clamping mechanism; a step of attaching a refractory material (5) to the bottom of the steel ladle and below the mold (3); applying a load (4) to the mold (3); removing the mould (3) from the refractory material (5); Including, The method further comprises the step of forming a chamfer around an outlet valve from the bottom of the steel ladle through a hatch in the bottom of the mold during application of refractory material, wherein the outlet valve and the chamfer are located in the thinner region of the thickness.

2. 2. The method of claim 1, wherein the refractory material is refractory concrete.

3. 3. The method according to claim 1 or 2, characterized in that the mold has a slope and a straight or curved profile.

4. 4. The method of claim 1, wherein the step of securing the mold with the clamping mechanism includes supporting the mold on a valve seat at the bottom of the steel ladle and locking the structure to prevent movement during application of a load.

5. 5. A method according to any one of claims 1 to 4, characterized in that the load applied to the mould is formed by a quantity of the refractory material or a material comprising steel, fibre or wood that partially fills the mould to compensate for the buoyancy caused by the refractory material on the mould.

6. A bottom of a steel pot, the bottom of the steel pot is formed by a coating of refractory material (5) and has a profile extending from a thicker region to a thinner region and an impact area (16) in the thicker region, and an outlet valve (2) is located in the thinner region of the bottom of the refractory material; The bottom of a steel ladle is characterized in that it comprises at least one chamfer (14, 15) arranged around the valve seat of the outlet valve (2) in the area of ​​thinner thickness.

7. 7. The bottom of a steel pot according to claim 6, wherein the end of the profile is located near the impact area.

8. 8. The bottom of a steel ladle according to claim 6 or 7, characterized in that the profile extends from two distant ends of the impact area located in the thicker area.

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