Method for coating the bottom of a steel pan and the bottom of a steel pan

Abstract

The present invention provides a method for coating the bottom of a steel pot, comprising the steps of positioning a mold on the bottom of the steel pot; securing the mold with a fastening mechanism; applying a 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 advantageous in that it increases the metal yield of the pot and reduces non-metallic inclusions typically introduced by eddy currents.

Description

Technical Field

[0001] The present invention relates to a method for coating a steel pot with a concrete refractory material using a mold attached to the bottom of the pot, thereby allowing the introduction of characteristic flow lines that improve the flow, provide high-speed exhaustion of the steel, and reduce the phenomena associated with eddies and discharges, thereby reducing the passage of slag. Thus, it is possible to increase the metal yield of the pot and reduce the non-metallic inclusions that are usually entrained by the eddies that form. Background Art

[0002] During the steelmaking process, liquid metal is poured from a converter into a steel pot. Figure 1 As shown, the kettle is a device consisting of a metal shell 1, the interior of which is lined with refractory material to withstand the high temperatures of the liquid steel. The bottom 5 of the kettle is made of refractory bricks, with an area for the injection of the steel jet (impact), which is generally thicker to withstand wear. Another area contains a refractory workpiece with a porous plug for injecting argon to optimize the metallurgical process, and another area is composed of a flow control system 2, which includes a gate valve that controls the passage of steel. The gate valve is composed of two plates with holes that are aligned to allow the steel to pass through.

[0003] Furthermore, the pot undergoes metallurgical treatment to chemically and thermally condition the steel. The pot is then attached to the caster tower, and a gate valve is opened to allow the steel to flow into a distributor. Due to the irregular shape of the pot's bottom, some steel remains when it is drained, preventing all liquid steel from flowing out of the pot. Consequently, metal production is reduced, as this residual steel becomes scrap (which is then reprocessed). This problem represents a significant cost in terms of energy and time consumption.

[0004] Another problem that occurs during the pot flow process is the formation of vortices, which increases pouring time and allows slag to enter the distributor. At the end of the pour, a discharge phenomenon also occurs. This discharge causes the slag to collapse in the last few minutes of the flow process, preventing the flow of the remaining steel.

[0005] In view of this, there is a need for the development of technologies that allow a better flow of the steel, ensure a better metal yield, reduce reprocessing, and improve the quality of the steel (inclusions).

[0006] Over the years, several technologies have emerged to address some of the fluid dynamics issues. Among the various proposals, one of the most well-known is the staggered assembly of bricks. This solution involves providing steps along the bottom of the pot, with the steel from the melting furnace falling at a higher height, and the gate valve area being the deepest. However, this solution, applied in most projects, only partially improves the problem and is not very efficient, as approximately 1% to 4% of the steel still remains.

[0007] Another common solution adopted by some steel mills is to tilt the pot during the pouring process. This tilt allows more liquid steel to drain, increases the height of the metal column, and prevents the ingestion of some of the upper layer of clear slag. This solution is not very safe, as metal spacers are required to tilt the pot, and it also interferes with the operation of the long pipes that guide the liquid steel to the distributor.

[0008] Documents PI 0307454-4 and WO2003072285A1 propose a novel solution to reduce metal entrapment in the bottom of the pot and reduce the passage of slag through the gate valve system. This solution includes platforms of varying heights and a gate valve located at the lowest part of the pot. These platforms are described as horizontal, retaining a portion of the supernatant slag. Below the platforms, there is a sloped bottom, which allows the liquid metal column to rise, preferentially flowing toward the gate valve. A location above the gate, called a sump, acts as a reservoir for the liquid metal, increasing its residence time in this area and preventing slag drag. The same solution can also include a set of multiple chamfers, described as recesses. This type of solution is also described in US Pat. No. 5,196,051. This approach is intended to prevent the formation of vortices. However, these documents do not include fluid dynamics studies to support this claim.

[0009] Document US 4746102 proposes another type of pot bottom, which essentially comprises an inclined slope to the gate valve position. This solution allows the discharge of large amounts of liquid metal, however, it does not guarantee a reduction in the passage of slag during the pouring process due to obstructions (eddy currents) and drainage effects.

[0010] The prior art literature does not describe in detail the manufacturing processes used in these contexts, which indicates that known solutions consist of prefabricated parts that are assembled at the installation site.

[0011] Known techniques in the prior art claim to increase metal yield or even reduce slag throughput, but they offer no scientific explanation (either through water or numerical modeling) as to how this occurs. Instead, they simply offer empirical suggestions based on interpretations of the relevant phenomena. In other words, such solutions require more results to confirm such improvements.

[0012] Therefore, the prior art lacks a solution that can provide a steel pot bottom coating that can improve the steelmaking process and is easy to install and can be carried out at the operating site. In addition, the prior art does not provide a solution that can provide a pot bottom coating with the same characteristic profile throughout its entire life. Summary of the Invention

[0013] Purpose of the Invention

[0014] The object of the present invention is to provide a method for producing a monolithic pot bottom coating (refractory concrete) with a characteristic profile by using a metal mold in order to improve the flow of liquid steel, allow greater depletion of steel, and reduce the passage of slag.

[0015] Another objective of the present invention is to develop a coating that includes inclined channels connecting the pot endpoints, smoothly directing the flow to the gate valve system. The channel slope can be formed into a curved or straight profile. The channel slope accelerates the steel flow, which helps maintain slag and partially disrupts eddy currents at the gate valve location.

[0016] Furthermore, one object of the present invention is to provide for the construction of barriers adjacent to the gate valve system during on-site concrete pouring. These barriers have the function of disrupting the circular motion characteristic of the vortex flow. These barriers, referred to herein as chamfers, are formed during the concrete pouring process or are prefabricated and inserted on-site.

[0017] To achieve the above-mentioned object, the present invention provides a method for coating the bottom of a steel pot, comprising the following steps: positioning a mold at the bottom of the steel pot; fixing the mold by a clamping mechanism; applying a refractory material to the bottom of the steel pot and placing it under the mold; applying a load to the mold; and removing the mold from the refractory material. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A cross-sectional view of a steel pan is shown.

[0019] Figure 2 A cross-sectional view of a steel pot having a pot bottom is shown according to one form of the present invention.

[0020] Figure 3 Contour areas with different configurations according to the present invention are shown.

[0021] Figure 4 Another form of the steel pan bottom coating according to the present invention is shown;

[0022] Figure 5 A mould according to the invention is shown.

[0023] Figure 6 A cross-sectional view of one end of a mold according to the present invention is shown.

[0024] Figure 7 A longitudinal sectional view showing a coupling system and a mold in a gate valve according to the present invention is shown.

[0025] Figure 8 A support system for a mould according to the invention is shown.

[0026] Figure 9Another form of pot bottom according to the present invention is shown.

[0027] Figure 10 Another form of pot bottom according to the present invention is shown.

[0028] Figure 11 Another form of pot bottom according to the present invention is shown.

[0029] Figure 12 A prefabricated workpiece according to a mode of the invention is shown. DETAILED DESCRIPTION

[0030] The following description will begin with a preferred embodiment of the invention applied to the bottom of a steel pan. However, it will be apparent to those skilled in the art that the invention is not limited to any particular form, nor to a particular method of coating a steel pan.

[0031] As already mentioned, Figure 1 A schematic diagram of a steel pot used in the steelmaking process is shown. The pot comprises a pot bottom 1 made of refractory material. In addition, the pot comprises a valve seat 2 formed as a gate valve that allows the steel to flow.

[0032] Typically, the bottom of the kettle receives the steel jet from the converter at a location with the thickest refractory material, thus being the highest point in the kettle. From this location, the liquid steel diffuses into the rest of the kettle until the liquid level rises. However, in some areas of the kettle, insufficient steel flow occurs. To address this issue, a coating background that improves steel depletion has been proposed.

[0033] Figure 2 A first form of the steel pot bottom coating according to the present invention is shown, which is applied to a steel pot including an impact area 16 and a valve seat 2. The pot bottom coating according to the present invention has a printed feature profile determined to form a characteristic flow channel, which is formed due to the thickness variation of the profile extending from a larger thickness area to a smaller thickness area of the pot bottom.

[0034] In this form, the pot bottom only includes the impact piece 16 and the valve seat 2. The mold has a C-shaped shape, in which the end protrudes from a point on one side of the pot bottom adjacent to the impact area 16 in the area of greater thickness in a generally circular manner, passes through the valve seat 2 in the area of lesser thickness, and reaches a point on the opposite side adjacent to the impact area 16 in the area of greater thickness. This form allows the blind area near the impact area 16 in the area of greater thickness to be connected to the outlet valve in the area of lesser thickness.

[0035] Depending on the placement of the gate valves relative to other areas of the pot, the shape of the profile can be varied in order to optimize as much as possible and eliminate dead zones where steel may be stored within the pot.

[0036] Depending on the type of pot used, the final printed profile should have different features to improve flow. For example, the pot may have a second outlet valve area, through which the steel will drain into the casting. Some pots may also have a porous plug, which is often used for inert gas injection to improve steel refining.

[0037] Therefore, it was found that the mold should ideally occupy or cover as much of the pot bottom area as possible (except for the impact area). This ensures maximum coverage of the blind area, allowing the capture of metal steel that cannot be converted by the valve seat. In this way, the mold creates a depression that connects the point to the common interconnection of the gate valve area.

[0038] Figure 3 The diagram shows the areas of the pot bottom that can be occupied by profiles with different configurations, taking into account the locations of the impact zone 16, the valve seat 2, and the porous plug 19. Considering the different configurations of the pot bottom, two important areas can be considered: the effective improvement zone 17, which is where the new profile for flow improvement will be located. This is the point farthest from the valve seat 2, or the zero point, from which the bottom thickness decreases toward the valve seat, creating a region of greater depth. Another highlighted area is the decision zone 18, which represents the possible location of the valve seat 2 and the porous plug 19.

[0039] In the case of a pot without a porous plug 19, the resulting design is simple and straightforward, i.e. interconnecting the various remote points with the valve seat 2, with Figure 2 C-shaped profile shown.

[0040] In case the bottom of the pot has a porous plug, the profile needs to be adjusted in a way that prevents the feature path from passing through the porous plug. Figure 4 One mode of the invention is shown, which is used in a case where the pot bottom has a plug 19 between the end points of the profile, and therefore it is necessary to apply an offset around the plug 19. In other words, the feature profile used in the mold must be able to form a feature curve around the porous plug 19, keeping it in the thicker area at the pot bottom.

[0041] For coating steel pans, it is recommended to use Figure 5 Example mold 3. It can be seen that the mold 3 has a preferred curved box-like shape, the cross-sectional shape of which corresponds to the contour to be printed on the bottom of the pot. In this form, the mold 3 has a corresponding Figure 2 The profile shape 10 of the profile is shown. This curved profile prevents the occurrence of stress concentrations in the concrete 5. Furthermore, it has been found that the curved form also helps reduce head losses in the area closest to the impact zone. However, the mold can be manufactured with an angular shape, a trapezoidal shape with slight bevels at its edges, or a straight shape.

[0042] Furthermore, the mould has a thickness that varies along its length and corresponds to the height variation that it is desired to apply to the bottom of the pot, in order to improve the flow of the steel. Figure 6 Shown according to Figure 5 A cross-sectional view of one end of the mold showing the change in height.

[0043] Besides this, the mould 3 comprises, in its upper region, a system for its fixing and support, and in its lower region, a fixing system and hatches for the concreting, as will be described below.

[0044] At the start of the coating process, the pot 1 is released for refractory retrofitting.

[0045] The mold 3 is then inserted from above via a crane and positioned over the bottom of the steel pot 1 to be coupled to the valve 2 , thereby connecting the end point of the steel pot to the gate valve 2 system.

[0046] The mould 3 is then clamped to produce the coating. Preferably, the mould 3 is attached to the valve seat 2 at the bottom of the steel pot 1 .

[0047] Then, a refractory material 5 is applied to the bottom of the pot 1 and fills the space below the mould 3 so that the coating conforms to the characteristic profile according to the invention. Preferably, the refractory material used is refractory concrete.

[0048] To ensure the desired contour, it is recommended to partially fill the interior of the mold 3 by forming a hollow or recessed portion containing a load 4. The load 4 can be made of concrete itself, or filled with the same material as the mold (steel, fiber, wood, etc.), as long as it provides sufficient weight to the structure. This operation compensates for the buoyancy of the concrete 5 being molded. Since the mold 3 is manufactured in the form of a box 10, i.e., hollow inside, the buoyancy generated is too great and could damage the mold clamping mechanism. Therefore, it is necessary to calculate the partial volume 4 to be filled to ensure that the weight of the mold is balanced with the buoyancy generated by the concrete.

[0049] Mold 3 has beveled surfaces to create a profile that preferentially allows steel to flow through. The mold's zero point should be as far from the valve seat 2 as possible to allow steel to be captured from blind spots. Starting from the zero point, there is a depth difference relative to the valve seat 2. In other words, the contours of mold 3 create two preferential concrete height levels. This height difference allows flow through the channel formed by mold 3, picking up steel from distant points in areas of greater thickness and creating preferential flow toward the valve 2 in areas of lesser thickness. The resulting accelerated flow creates a force that holds the slag longer, thus preventing discharge.

[0050] In order to improve the application of the refractory material and the shaping of the steel pot bottom, the mould must be kept clamped until the refractory material is shaped. In this regard, the method according to the invention provides the use of a clamping mechanism.

[0051] according to Figure 7 , the mold 3 is clamped and locked in the valve seat 2. In the center of the valve, a center pin 6 is inserted, which is coupled to the mold 3, which will be locked by a clamping system 9 to prevent the mold 3 from moving during concrete pouring.

[0052] Preferably, if Figure 8 As shown, the mold has a fulcrum 11 to avoid stress on the mold end 3 due to the weight generated 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 mold 3 itself, with a central hole to allow the passage of the support pin 12. However, the fulcrum can be formed by a part assembled or attached to the mold to allow clamping by the pin 12.

[0053] In this way, the support system allows the mould to remain level during the application of the load.To allow the desired height adjustment, the pin 12 has a hole 13 which allows adjustment during clamping and preparation for applying the refractory material, subsequently supporting the mould on the bottom of the pot.

[0054] When the concrete is finished, the support pins 12 are removed, taking care to vibrate the concrete to avoid voids.The height adjustment system may alternatively use any other system that allows height adjustment, such as a screw system that rotates to raise the mould.

[0055] The present invention thus provides a method that allows for a practical installation that can be directly applied to the bottom of a steel pot, enabling improvements to be achieved in the steelmaking process.

[0056] Preferably, the coating background according to the present invention may comprise an anti-eddy current system to prevent the formation of eddy current phenomena. For this purpose, Figure 5 As shown, the mold 3 may include openings or hatches 20 located near the openings corresponding to the valve seats, which allow the concrete to rise during the concrete pouring process. More specifically, through the use of hatches 20, the concrete height increases at these openings during the concrete pouring process, forming chamfers. An external vibrator may be used at this stage to ensure homogenization of the concrete.

[0057] Therefore, in addition to printing the characteristic contour, the pot bottom coating will include an anti-vortex system formed by chamfers 14 and 15 near the valve seat, which generates a disturbance of the flow and thus prevents the formation of vortices.

[0058] As mentioned above, eddy currents are a fluid dynamic phenomenon that can draw slag into the valve. The anti-eddy current system can include at least one chamfer 14, preferably two chamfers 14 and 15. Thus, the present invention provides a method and a pot bottom coating that can increase steel flow and prevent the occurrence of eddy currents.

[0059] Figure 9 、 Figure 10 and Figure 11 Other forms of the invention are shown. Among them, the coating method is applied to different pot bottoms. Each coated bottom includes an anti-vortex system, a characteristic flow channel and a preformed impact piece 16. The height of the impact piece is higher than the bottom, which helps the flow of steel. The piece has a convex edge, which helps the flow at the end of the pot and prevents damage caused by sharp corners. The piece is previously made into a special shape through molding, and is cured and dried in a controlled environment. This operation is intended to obtain a high-strength preform for use in the impact area (higher mechanical requirements).

[0060] It should be noted that Figures 9 to 11 Each background shown has a different outline, but in Figure 3 Therefore, for the molding of each background, a mold with a different characteristic profile must be used in order to create the desired profile in each case.

[0061] The present invention thus provides a method for coating pan bottoms and a mould allowing simpler forming (either on site or for making preforms) with a shape that improves the steelmaking process.

[0062] Specifically, Figure 11 One form of the present invention is shown applied to a pot bottom comprising an impact zone 16, a valve seat 2, and a porous plug 19. In this configuration, the impact zone 16 is positioned adjacent to the wall of the steel pot, and the valve seat 2 is positioned adjacent to one side of the impact zone. The porous plug 19 is positioned adjacent to the other side of the impact zone. In this manner, the profile used has an end closer to the porous plug 16 and extending to the valve seat 2. Furthermore, for better utilization, the profile has a larger area to achieve the maximum number of blind spots. This allows steel to flow from the area near the porous plug 19 to the valve seat. To reduce eddy current effects, chamfers 14 and 15 are positioned close to the valve seat 2.

[0063] Figure 12 One form of the invention is shown applied to a steel pot, configured so that a porous plug 19 is positioned adjacent to the impact zone 16, and the valve seat 2 is close to the pot wall. In this case, the profile has a C-shape, as in the first form of the invention, with its ends each located on one side of the impact zone 16. It should also be noted that the profile bypasses the porous plug 19.

[0064] In addition to providing a simple and practical method for coating the bottom of a pot at the installation site, the present invention also makes it possible to manufacture preforms. The mold 3 can be applied to a preform which will have the printed outline and can be installed at the desired location.

[0065] Thus, it can be seen that the present invention provides a simple and practical method for improving the utilization of steel in pots of various configurations. Furthermore, it can be seen that the present invention is advantageous in terms of coating application (at the installation site and in the manufacture of prefabricated parts).

[0066] The advantages of the invention were observed in experiments on a 1 / 8 scale physical model using water as a similar fluid to simulate the flow. Noting the preferential flow generated by the curved channel, at the end of the emptying of the water, a maintaining force was observed that prevented the collapse of the surface (discharge phenomenon). The normal streamlines pull from all directions, including from the surface (slag). By creating a curved cavity at the bottom, it is possible to obtain a preferential acceleration from the periphery to the valve seat 2. In this physical model experiment, water was used as a steel-like fluid and two configurations were compared: a straight bottom (current) and the bottom proposed by the invention. By analyzing the water flowing through the valve, the moment of the discharge phenomenon was observed. At this moment, the volume of water remaining in the pot was marked. The background proposed by the invention reduces the volume of water remaining in the pot by 75%, which will result in an increase in metal production.

[0067] Another advantage of the present invention relates to the type of surface wear during pot operation. A problem observed in the aforementioned patent document was how to maintain the same design until the end of the refractory coating's life. During water model testing, the curved cavity 10 provided preferential flow within it. This resulted in preferential wear in the cavity, thus ensuring a constant curved bottom shape. In other words, the solution proposed by the present invention tends to maintain the same functionality until the end of the coating's life.

[0068] The present invention thus provides a method for coating the bottom of a steel pan which allows for an installation which can improve the steel manufacturing process and which is a practical installation which can be carried out at the operating site.

[0069] Numerous variations are possible within the scope of the invention. It is therefore emphasized that the invention is not limited to the specific configurations or embodiments described above.

Claims

1. A method for coating the bottom of a steel pot, wherein the steel pot is used in a steelmaking process, characterized in that It includes the following steps: Positioning a mold (3) on the bottom of the steel pot (1), wherein the mold has a C-shape corresponding to the contour to be coated on the bottom of the steel pot, the impact area is located in the area of greater thickness of the bottom of the steel pot, the valve seat (2) is located in the area of less thickness of the bottom of the steel pot, and the mold has a recess extending from the area of greater thickness where the end is located to the area of less thickness, the valve seat (2) is located inside the recess, and both ends of the mold are located in the area of greater thickness of the bottom of the steel pot and adjacent to the impact area; Fixing the mold (3) by a clamping mechanism; Applying refractory material (5) to the bottom of the pot and underneath the mold (3); applying a load (4) to the mold (3); and The mould (3) is removed from the refractory material (5).

2. The method according to claim 1, characterized in that The refractory material is refractory concrete.

3. The method according to claim 1, characterized in that The mold has beveled surfaces and straight or curved contours.

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

5. The method according to claim 1, wherein The load applied to the mold is formed by a refractory or other material in an amount that partially fills the mold to compensate for the buoyancy created by the refractory material below the mold.

6. The method according to any one of claims 1 to 5, characterized in that The method further comprises the step of forming a chamfer around the outlet valve from the bottom of the pot through a hatch in the bottom of the mould during application of the refractory material.

7. A bottom of a steel pot, wherein the steel pot is used in a steelmaking process, characterized in that The steel pot bottom is formed by a coating of refractory material (5) and comprises a C-shaped profile extending from an area of greater thickness where the ends are located to an area of lesser thickness, wherein the valve seat (2) is located in the area of lesser thickness of the refractory bottom, the steel pot bottom comprises an impact area (16) located in the area of greater thickness, and the two ends of the profile are located in the area of greater thickness of the refractory bottom and are adjacent to the impact area.

8. The steel pot bottom according to claim 7, characterized in that: The profile extends from two distal ends located in the region of greater thickness.

9. The steel pot bottom according to any one of claims 7 to 8, characterized in that The steel pot bottom comprises at least one chamfer (14, 15) around the valve seat (2) in an area of smaller thickness.

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