Mould for a continuous casting system and continuous casting system

Abstract

The invention relates to the field of metallurgical systems, specifically a mould for a continuous casting system. The object of the invention is to provide a mould which ensures a reduction in the copper wall temperature alongside small deformations of the copper pipe as a result of the cooling medium pressure. The object is achieved in that, in the region of the meniscus, the inner mould has, in the circumferential direction, at least two, preferably at least four, depressions with a width. All the widths of the depressions added in the circumferential direction have a value of at least 40%, preferably at least 50%, particularly preferably at least 70% of an inner circumference of the inner mould. The depressions have a length of at least 10% of the length of the mould. The depressions are designed with a depth such that the remaining wall thickness of the inner mould in the region of the depression is at least 9 mm, preferably at least 8 mm, particularly preferably at least 7 mm.

Description

[0001] Description

[0002] Title of the invention

[0003] Mold for continuous casting plant and continuous casting plant

[0004] field of technology

[0005] The present invention relates to the field of metallurgical plants, specifically a mold for a continuous casting plant.

[0006] On the one hand, the invention relates to a mold for continuous casting of a metal product, preferably for casting billets or ingots, which has a tubular structure. The mold consists of an inner mold with circumferentially closed side walls, which has a predetermined wall thickness, and an outer cooling medium jacket that circumferentially encloses the inner mold. The mold has a longitudinal length of at least 500 mm, and the mold defines a region in which the meniscus (M) of the liquid metal is located during continuous casting. At least one cooling channel (2a) for the flow of coolant is provided between the cooling medium jacket and the inner mold.

[0007] On the other hand, the invention relates to a continuous casting plant.

[0008] State of the art

[0009] Pipe molds are typically used for formats up to a size of approximately 350x350mm and casting speeds up to 6m / min.

[0010] For example, a 160x160mm format is used particularly in high-speed systems with a maximum casting speed of approximately 5-6 m / min. At these high casting speeds, very high temperatures of up to 370°C occur in the meniscus area of ​​the mold's inner wall, which can lead to damage, such as cracks on the hot side, even after only a short period of use. An effective reduction of these temperatures is only possible by reducing the wall thickness of the copper tube. Typically, the wall thickness of the mold tube is about 10% of the format dimensions; thus, for a 160x160mm format, the copper wall thickness is approximately 16mm. However, reducing the wall thickness results in increased deformation of the copper tube due to primary water pressure. In molds designed for higher casting speeds, the water pressure can rise to 15 bar.For larger formats, the wall thickness is therefore increased accordingly to minimize deformation of the mold tube. However, increasing the wall thickness also raises the temperatures in the mold at a given casting speed. In addition to the primary water pressure, high and often inhomogeneous temperatures in the copper wall also generate additional deformations and corresponding stresses in the mold tube.

[0011] Document WO 2004 / 091826 shows a pipe mold which has a small wall thickness of the copper pipe, which increases the cooling capacity and thus also increases the performance of the continuous casting plant.

[0012] Document WO 2023 / 057917 shows a pipe mold which has a thin-walled copper shell with external longitudinal grooves, which are closed to form cooling channels by a fiber-reinforced composite wrapping.

[0013] Document WO2016178153A1 shows a tubular mold consisting of three tubular bodies. The first tubular body is in contact with the molten metal. The second tubular body surrounds the first tubular body from its upper edge to below the meniscus area. The third tubular body is located below the second tubular body. Cooling channels for the flow of coolant are formed between the outer surface of the first tubular body and the second and third tubular bodies.

[0014] Document WO 2008 / 017402 shows a mold side plate which is reduced in thickness – i.e., the distance between the hot side and the coolant channel base – in areas of increased heat loads.

[0015] Summary of the invention

[0016] The object of the invention is to provide a mold which ensures a reduction in the copper wall temperature while simultaneously minimizing deformation of the copper tube due to the cooling medium pressure.

[0017] The problem is solved by providing the inner mold in the meniscus region with at least two, preferably at least four, circumferential recesses of a certain width. The sum of the circumferential widths of the recesses is at least 40%, preferably at least 50%, and particularly preferably at least 70% of the inner circumference of the inner mold. The recesses have a length of at least 10%, preferably 15%, more preferably 20%, particularly preferably 25%, and most preferably 30% of the length of the mold. The recesses are designed with a depth such that the remaining wall thickness of the inner mold in the region of the recess is at least 9 mm, preferably at least 8 mm, and most preferably at least 7 mm.

[0018] The widths of the recesses can be designed differently, but in order to achieve the desired cooling effect, the sum of the widths of the recesses in the circumferential direction should have a value of at least 40%.

[0019] The inner circumference of the inner mold is measured on the side that comes into contact with the liquid metal during continuous casting.

[0020] The highest heat input into the inner mold occurs in the meniscus area, where there is either no or only a very thin strand shell. Consequently, the maximum temperature in the inner mold occurs just below the meniscus. Therefore, it is only advisable to reduce the wall thickness appropriately in this area. Outside this area, it can even be beneficial to slightly increase the wall thickness to generally improve the thermal stability of high-speed casting molds.

[0021] The reduction of the mold wall thickness in the meniscus area—with a length of at least 10% of the mold length—is achieved by milling suitable recesses into the mold wall. These recesses can be designed, for example, as slots or rounded indentations. The design of the recesses generally depends on the size and cross-sectional shape of the inner mold. A minimum wall thickness of 7–9 mm is targeted in the recessed area. The inner mold is preferably made of copper. The recesses in the inner mold are open at the top; a bore located in the wall of the inner mold that has no opening in the circumferential direction, but only on the end face, is not considered a recess within the meaning of this invention. Water is a preferred cooling medium for such molds.According to the invention, displacement bodies are arranged directly on the cooling medium jacket in the area of ​​at least 50%, preferably 100%, of the recesses, wherein the displacement bodies form a displacement jacket cooling channel with the recesses and the inner mold, with a predetermined gap.

[0022] Displacement elements can be inserted into recesses to define the flow cross-section and thus achieve a desired flow velocity of the cooling medium. The specified gap depends primarily on the desired flow velocities of the cooling medium within the displacement jacket cooling channel.

[0023] In this way, heat dissipation in the casting surface area is increased and the temperature of the inner mold is reduced. Preferably, the flow velocities of the cooling medium in the meniscus area should be on the order of at least 10 m / s. The embodiment according to the invention provides that the displacement bodies are inserted into a displacement jacket, which surrounds the inner mold circumferentially and has slots in the area of ​​the recesses, in order to establish a defined recess cooling channel between the displacement body and the inner mold and a displacement jacket cooling channel between the displacement jacket and the inner mold.

[0024] In an advantageous embodiment, the recesses begin at a distance below the upper edge of the inner mold, where this distance corresponds to 30% to 50% of the distance between the meniscus and the upper edge of the inner mold. To ensure optimal cooling at the meniscus, the recesses begin above it.

[0025] A preferred embodiment provides that several immediately adjacent displacement bodies are manufactured from a single component and inserted into a displacement shell. This embodiment of the displacement bodies can then be produced, for example, by 3D printing. In this way, several adjacent displacement bodies can be combined, thereby reducing assembly effort.

[0026] A preferred embodiment provides that the displacement bodies are inserted into a displacement jacket which surrounds the inner mold in the circumferential direction and has slots in the area of ​​the recesses in order to establish a defined recess cooling channel between displacement body and inner mold and a displacement jacket cooling channel between displacement jacket and inner mold.

[0027] A practical design provides that the displacement bodies and the displacement jacket are arranged in such a way that the cooling medium can only flow through the recessed cooling channels. This means that no cooling medium flows in the areas between the recesses.

[0028] In this embodiment, the displacement jacket closes off the cooling channel of the displacement jacket, so no cooling medium flows through it. An advantageous embodiment provides that the displacement elements are detachably connected to the cooling medium jacket, preferably by screws.

[0029] A preferred embodiment provides that the cavity cooling channel is adjusted by means of displacement elements such that the flow velocity is at least as high, preferably higher, than in a region before and / or after the cavities. Preferably, the flow velocity in the cavity channel is at least 10 m / s, more preferably at least 12 m / s, and most preferably 15 m / s. By knowing the respective system parameters of a continuous casting plant for which the mold is to be used, such as coolant pressure and coolant quantity, the flow velocities in the cavity channel can be specifically adjusted by means of the displacement elements.

[0030] In a preferred embodiment, the side walls of the inner mold below the meniscus, preferably below the recesses, are at least partially curved inwards in the circumferential direction; preferably, a maximum normal distance of the curved side wall from the straight shape is 0.3%-5% of the respective width of the side walls.

[0031] The side walls therefore press slightly into the extrusion. The side walls of the inner mold could be straight in the upper area and then develop an increasingly pronounced bulge towards the mold exit. This bulge, i.e., the maximum normal deviation from the assumed straight contour, could correspond to 0.5 to 5% of a side width.

[0032] In an advantageous embodiment, the side walls of the inner mold below the meniscus, preferably below the recesses, are at least partially curved inwards in the longitudinal direction; preferably, the maximum normal distance of the side wall in the longitudinal direction from the straight shape is 0.2%-2% of the length of the mold.

[0033] In a preferred embodiment, the recesses have a circumferential radius of at least 2 mm, preferably at least half the width of the recess, and / or a longitudinal radius of at least 2 mm, preferably in a region two to ten times the width of the recess. These radii ensure a more uniform flow of the cooling medium. In an advantageous embodiment, the cross-sectional shape of the mold is a polygon, preferably an octagon, preferably with equal sides, a rectangle, and / or a square or a circle.

[0034] A particularly advantageous embodiment provides that the length of the recesses has a maximum length of 20%, particularly preferably 25%, most preferably 30% of the length of the mold.

[0035] A suitable design provides that the area in which the meniscus of the liquid metal is located during continuous casting lies 50mm to 180mm, preferably 60mm to 100mm below the top edge.

[0036] Another preferred embodiment provides that the inner side walls of the inner mold each have several raised and recessed areas on their inner surfaces, resulting in a ribbed surface on one side wall. This design creates a channel between the raised and recessed areas on the inner surfaces. This prevents or minimizes thermal distortion of the cast product within the mold.

[0037] The task is also solved by a continuous casting plant, which includes a mold with a previously described design.

[0038] A suitable design provides that the continuous casting plant is equipped with a cooling medium pump and a control device for adjusting cooling medium velocities in the area of ​​the depressions of at least 10m / s.

[0039] Brief description of the drawings

[0040] The properties, features, and advantages of this invention described above, as well as the manner in which they are achieved, will become clearer and more readily understandable in connection with the following description of an exemplary embodiment, which is explained in more detail in conjunction with the drawings. These drawings show:

[0041] Figs. 1-5 show a schematic representation of a mold with recesses in the area of ​​the meniscus; description of the embodiments

[0042] Figures 1-5 show a mold 1, which is surrounded by the inner mold 2 and a cooling medium jacket 3 in the circumferential direction UR. The inner mold 2 has recesses 4 extending longitudinally LR. In this embodiment, displacement elements 5, attached to the cooling medium jacket 3, are arranged in the area of ​​the recesses 4 and project into them. Furthermore, in this embodiment, a displacement jacket 6 is provided between the cooling medium jacket 3 and the inner mold 2. The displacement elements 5 are inserted into slots in this jacket and project into the recesses 4.

[0043] Figure 2 shows an enlarged view of the recesses 4 and the displacement body 5. The inner mold 2 has a wall thickness W, and the remaining wall thickness Wv in the recesses results, with a gap S between the inner mold and the displacement body 4.

[0044] The recesses have a width B and a radius Rb in the lateral direction. The sum of all widths B of the recesses 4 in the circumferential direction UR should be at least 40% of the inner circumference of the inner mold 2 in order to achieve the desired cooling effect.

[0045] In Fig. 3, the recess 4 has a radius RI in the longitudinal direction LR. This allows for a more uniform flow of coolant within the mold. A displacement cooling channel 4a forms between the recess 4 and the displacement body 5. The flow velocity can be adjusted by the size of the gap between the recess 4 and the displacement body 5. A cooling channel 3a is formed upstream and downstream of the recesses 4 by the cooling medium jacket 3 and the inner mold 2.

[0046] Figure 4 shows an embodiment with a curved side wall 2b. This curved side wall has a maximum normal distance 2c of the curved side wall from the straight form in the circumferential direction UR of 0.3%–5% of the respective width of the side walls Bs.

[0047] Figure 5 shows the mold 1 and the meniscus M. The mold 1 has a length L. It can be seen that the recesses 4 are arranged over a length L1 in the area of ​​the meniscus. In a subsequent area with a length L2, the inner mold 2 is designed without recesses. The recesses 4 in the area of ​​the meniscus M provide a higher cooling effect and simultaneously give the inner mold the necessary stability against deformation. The recesses begin at a distance A from an upper edge 2a of the inner mold. This distance A preferably corresponds to 30% to 50% of the distance D between the upper edge 2a and the meniscus M. Figure 6 shows an exemplary embodiment in which the inner side walls of the inner mold each have several raised areas 7 and recessed areas 8, resulting in a ribbed surface on one of the side walls.This design creates a channel 9 between the inner raised areas 7 and the inner recesses 8.

[0048] Although the invention has been further illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples and other variations can be derived by the person skilled in the art without leaving the scope of protection of the invention.

[0049] Reference symbol list

[0050] 1 mold

[0051] 2 inner molds

[0052] 2a Top edge

[0053] 2b Side wall

[0054] 2c Maximum normal distance

[0055] 3 Cooling medium jacket

[0056] 3a Cooling channel

[0057] 4. Further Study

[0058] 4a Deep cooling channel

[0059] 5 displacement bodies

[0060] 6 Displacement mantle

[0061] 7 inner side elevations

[0062] 8 inner recesses

[0063] A distance

[0064] B Width

[0065] Bs width of the side walls

[0066] D distance

[0067] L Length of the mold

[0068] L1 Length of the depressions

[0069] L2 Length of following area

[0070] LR longitudinal direction

[0071] M Meniscus

[0072] Rb radius in the latitude direction

[0073] RI radius in longitudinal direction

[0074] S gap

[0075] UR circumferential direction

[0076] W wall thickness

[0077] Wv Remaining wall thickness

Claims

Claims 1. Mold (1) for continuous casting of a metal product, preferably for casting billets or ingots, which has a tubular structure, comprising an inner mold (2) with circumferentially closed side walls (2b) which has a predetermined wall thickness (W) and an outer cooling medium jacket (3) which surrounds the inner mold (2) circumferentially (UR), the mold (2) having a longitudinal length (LR) of at least 500 mm, wherein the mold (2) defines a region in which the meniscus (M) of the liquid metal is located during continuous casting, wherein at least one cooling channel (3a) for the flow of coolant is provided between the cooling medium jacket (3) and the inner mold (2), characterized in that at least two, preferably at least four, recesses (4) are arranged in the circumferential direction (UR) of the inner mold (2) in the region of the meniscus (M), wherein the recesses (4) exhibit widths (B),The sum of the circumferential widths (B) of the recesses (4) results in a value of at least 40%, preferably at least 50%, particularly preferably at least 70% of the inner circumference of the inner mold (2), and the length (L1) of the recesses (4) comprises at least 10%, preferably 15%, more preferably 20%, particularly preferably 25%, and most preferably 30% of the length (L) of the mold (1), wherein the recesses (4) are designed with a depth such that the remaining wall thickness (Wv) in the area of ​​the recess is at least 9 mm, preferably at least 8 mm, and most preferably at least 7 mm, wherein displacement bodies (5) are arranged directly on the cooling medium jacket (3) in the area of ​​at least 50%, preferably at 100%, of the recesses (4), and wherein the displacement bodies (5) form a recess cooling channel (4a) with the recesses (4) of the inner mold. (2) form, with a predetermined gap (S), wherein the displacement bodies (5) are enclosed in a displacement shell (6),which surrounds the inner mold (2) in the circumferential direction (UR) and has slots in the area of ​​the recesses (4), are used to establish a defined recess cooling channel (4a) between the displacement body (5) and the recesses (4) of the inner mold (2) and a displacement jacket cooling channel between the displacement jacket (6) and the inner mold (2).

2. Mold (1) for continuous casting of a metal product, according to claim 1, characterized in that recesses (4) begin at a distance (A) below an upper edge (2a) of the inner mold (2), wherein the distance (A) is 30% to 50% a distance (D) between the meniscus (M) and the upper edge (2a) of the inner mold (2) corresponds to.

3. Mold (1) for continuous casting of a metal product, according to claim 1 or 2, characterized in that several immediately adjacent displacement bodies (5) are made from one component and are inserted into a displacement shell.

4. Mold for continuous casting of a metal product, according to one of claims 3, characterized in that the displacement bodies (5) and the displacement jacket (6) are arranged such that cooling medium can flow exclusively through the recessed cooling channels (4).

5. Mold (1) for continuous casting of a metal product, according to one of claims 3 - 4, characterized in that the displacement bodies (5) are detachably connected, preferably screwed, to the cooling medium jacket (3).

6. Mold (1) for continuous casting of a metal product, according to one of claims 3 - 5, characterized in that the recess cooling channel (4a) is adjusted by means of the displacement bodies (5) such that the flow velocity is at least as high, preferably higher, than in the cooling channel (3a) in a region before the recesses (4) and / or after the recesses (4), preferably the flow velocity in the recess cooling channel (4a) is at least 10m / s, preferably at least 12m / s, most preferably 15m / s.

7. Mold (1) for continuous casting of a metal product, according to one of claims 1 or 6, characterized in that the side walls (2b) of the inner mold (2) below the meniscus (M), preferably below the recesses (4), are at least partially curved inwards in the circumferential direction (UR), preferably a maximum normal distance (2c) of the curved side wall (2b) from the straight shape is 0.3%-5% of a respective width (Bs) of the side walls (2b).

8. Mold (1) for continuous casting of a metal product, according to one of claims 1-7, characterized in that the side walls (2b) of the inner mold (2) below the meniscus (M), preferably below the recesses (4), are at least partially curved inwards in the longitudinal direction (LR), Preferably, the maximum normal distance of the curved side wall (2b) in the longitudinal direction (LR) from the straight shape is 0.2%-2% of the length (L) of the mold.

9. Mold (1) for continuous casting of a metal product according to one of claims 1 - 8, characterized in that the recesses (4) have a circumferential radius (UR) with a radius (R) of at least 2 mm, preferably at least half the width (B) of the recess (4), and / or a longitudinal radius (LR) with a radius (RI) of at least 2 mm, preferably in a region of two to ten times the width (B) of the recess (4).

10. Mold (1) for continuous casting of a metal product according to one of claims 1 - 9, characterized in that a cross-sectional shape of the inner mold (2) is a polygon, preferably an octagon, preferably with equal side lengths, a rectangle and / or a square or a circle.

11. Mold (1) for continuous casting of a metal product according to one of claims 1 - 10, characterized in that the length of the recesses (L1) is a maximum of 20%, particularly preferably 25%, most preferably 30% of the length (L) of the mold (1).

12. Mold (1) for continuous casting of a metal product according to one of claims 1 - 11 , characterized in that the area in which the meniscus (M) of the liquid metal is located during continuous casting is 50mm to 180mm, preferably 60mm to 100mm below the top edge.

13. Mold (1) for continuous casting of a metal product according to one of claims 1 - 12, characterized in that the inner side walls (2b) of the inner mold (2) each have several inner surface elevations (7) and inner surface depressions (8), whereby a surface of the side walls has a ribbing.

14. Continuous casting plant, characterized in that it comprises a mold (1) according to one of the preceding claims.

15. Continuous casting plant according to claim 12, characterized in that it is equipped with a cooling medium pump and a control device for adjusting cooling medium velocities in the area of ​​the depressions (4) of at least 10m / s.

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