mold

Abstract

The present invention relates to a mold body (1) for continuous casting of metal, having a longitudinal direction L between an upper end (4) and a lower end (5), and having a cooling structure (7,7a) in at least one partial region of the outer surface (6) of the mold body (1) to improve cooling. The cooling structure (7) comprises at least one V-shaped region having two legs and one tip that face each other at an opening angle, with the tip directed toward the lower end (5).

Description

Technical Field

[0001] The present invention relates to a mold body for continuously casting a metal according to the features in the first part of claim 1.

Background Art

[0002] A mold body for continuously casting a metal defines a mold cavity having an upper end portion and a lower end portion in the casting direction, either alone (mold tube) or in combination with another mold body (mold plate). The mold body is cooled on the outside. Most of the mold body is made of copper and has the problem of transporting the heat of the molten metal from the inside of the mold to the outside of the mold. Here, the heat transfer coefficient from the outside of the mold to the cooling medium plays a decisive role. The cooling medium is usually water guided in a closed circuit. The water flows at a flow rate of typically 6 to 14 m / s and flows turbulently somewhat faster in part on the outer surface of the mold body. A heat flux density in the region of a mold level of 3 to 7 MW / m 2 is common. The cooling water contacts the outer wall of the mold at a speed of about 10 m / s and is heated by 6 to 12 K during this time. The temperature of the outer wall of the mold is usually 120 to 300 °C, and the inside is about 250 to 450 °C. The wall thickness of the mold body depends on the format. The wall thickness is usually 8 to 12% of the casting format in the case of a mold tube and thus has a distance to the cooling water of 10 to a maximum of 35 mm. The mold tube typically has a length of 700 mm to 1200 mm.

[0003] German Patent Specification No. 19508169 discloses a mold for continuously casting a metal having a structure in which the surface on the cooling side has different shapes and / or recesses. The recesses affect the turbulence of the flow. The recesses enlarge the outer surface of the mold and thereby the cooling.

[0004] U.S. Patent No. 5,207,266 discloses a mold body for continuous casting of metal, wherein a portion of the outer surface is provided with a cooling structure to improve cooling. The cooling structure has at least one V-shaped region having two legs and one tip that are parallel to each other and facing each other, the tip being directed toward the end. The V-shaped region is formed as a groove on the outer surface and has width and depth. Coolant flows through the groove. The groove is covered by a support plate.

[0005] Furthermore, prior art can be cited as Chinese Patent Application Publication No. 113798451 and Korean Published Patent No. 20160057.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] German Patent No. 19508169 [Patent Document 2] U.S. Patent No. 5,207,266 [Patent Document 3] Chinese Patent Application Publication No. 113798451 Specification [Patent Document 4] Korean Published Patent No. 20160057 [Overview of the project] [Problems that the invention aims to solve]

[0007] The fundamental problem underlying this invention is to improve the cooling performance of a mold for continuous casting of metals. [Means for solving the problem]

[0008] This problem is solved by a mold having the features of claim 1.

[0009] The mold body according to the present invention for continuous casting of metal has a longitudinal direction between its upper and lower ends in the casting direction. At least one partial region of the outer surface of the mold tube is provided with a cooling structure to improve cooling. The cooling structure comprises at least one V-shaped region having two opposing legs and one tip at an opening angle, the tip directed toward the lower end of the mold tube. The orientation of the tip of the V-shaped region is, in particular, directed in the opposite direction to the flow direction of the cooling medium. The V-shaped region is formed as a groove on the outer surface and has a groove width and groove depth.

[0010] The V-shaped region creates a macrostructure within the boundary layer between the outer surface and the cooling medium flowing turbulently alongside it. These macrostructures cause the cooling medium to swirl more strongly, thus improving heat transfer and heat dissipation from the mold tube wall to the cooling medium.

[0011] Geometrically defined V-shaped regions can be called barriers from a fluid dynamics perspective. These are not individual point-like depressions, but V-shaped structures of a predetermined length and shape. Unlike point-like depressions, the coolant cannot flow laterally around these V-shaped structures, but can only flow over / through them. In this sense, the V-shaped regions constitute a "tripwire" for flow. Therefore, these are not roughness structures, but rather recesses on the outer surface of the mold body in the sense of wave structures, channel structures, or long grooves. In particular, the elongated length of each V-shaped region is greater than the width of one side of the outer surface of the mold tube. The elongated length is the length measured from one endpoint to the other of the V-shaped region as it progresses.

[0012] The effect of the tripwire for generating turbulence can be repeated by arranging the multiple V-shaped regions according to the present invention in a series of positions in the longitudinal direction of the mold and / or in a series of positions transverse to the longitudinal direction. Transverse to the longitudinal direction means, in particular, an angle of 90° with respect to the longitudinal direction. The term “transverse” includes angles other than 90°, except for 0° and 180°.

[0013] The set length of the longitudinal V-shaped region generates additional turbulence and vortices, particularly near the surface of the mold. Furthermore, the V-shaped region e expands the outer surface of the mold. These factors result in improved cooling.

[0014] In the case of V-shaped regions arranged sequentially in the longitudinal direction, one or more of the V-shaped regions overlap in the longitudinal direction depending on the size of the opening angle of the V-shaped regions. Preferably, the opening angle of the V-shaped regions is in the range of 30° to 150°, measured from leg to leg. The opening angle is composed of the angles of the two legs, and these leg angles are each related to the longitudinal direction of the mold body. Therefore, the angles of the legs are each 15° to 75°. Preferably, the angles of the legs are of equal magnitude. However, the angles of the legs may be different from each other.

[0015] Multiple V-shaped regions arranged sequentially in the longitudinal direction can be arranged side by side with respect to the flow direction or side by side with respect to the longitudinal direction. The number of V-shaped regions arranged side by side with respect to the longitudinal direction can be 1 to 50, particularly 1 to 10. Preferably, the number of V-shaped regions arranged side by side is less than 5, preferably 3 V-shaped regions.

[0016] V-shaped regions arranged side by side can be connected to each other to form a wave structure. The wave structure may be uniform, that is, all opening angles of the V-shaped regions of the wave structure are equal. In essence, a uniform opening angle can be provided for all V-shaped regions of the mold tube. This makes it possible to achieve a parallel structure that can be placed on the outer surface at relatively short distances from each other. In this case, the legs of two V-shaped regions arranged one behind the other in the longitudinal direction extend parallel to each other.

[0017] The V-shaped region is formed as a groove on the outer surface. The groove has a groove width and groove depth measured transversely to the longitudinal direction of the groove. The groove width is preferably in the range of 2 to 10 mm, and the groove depth is in the range of 0.1 to 2 mm. Preferably, the groove depth is at least 0.3 mm. However, in the sense of the present invention, a groove depth of at least 0.1 mm should no longer be classified on the order of roughness, but functionally should be classified in the tripwire region. The groove width and groove depth are preferably constant along the entire length of the groove. Selectively, the groove depth and / or groove width are varied to suit local cooling characteristics.

[0018] The grooves can have a rounded, rectangular, or trapezoidal cross-section. Accordingly, in the case of a rectangular cross-section, the groove depth can be constant. In the case of a rounded cross-section, the groove depth is maximum at the center of the groove. In the case of a trapezoidal cross-section, the groove depth on the side into which the coolant flows can be greater than that on the other side. The coolant flows to some extent along the first side, swirls within the deepest region of the groove, then flows out of the groove again via the rising groove bottom on the other side, and flows into the next groove. Generally, grooves have the effect of reducing the average distance between the coolant and the surface to be cooled, i.e., the inside of the mold, in addition to expanding the surface area. This locally enhances the cooling effect.

[0019] The distance between the parallel-extending legs of adjacent V-shaped regions preferably matches at least the groove width. The distance is preferably 2 to 10 mm. The distance should be selected so that additional microscopic turbulence is generated near the surface. This turbulence enhances the cooling effect.

[0020] In particular, a large amount of heat should be extracted in the meniscus region of the mold, i.e., the mold body, which is adjacent to the upper end. The meniscus region is the area where the mold level of the molten metal is located during casting. Therefore, the cooling structure should extend over a maximum of 30% of the length adjacent to the upper end. In other areas of the mold tube, the cooling structure according to the present invention is not necessary. Therefore, from a manufacturing technical standpoint, it is more advantageous to place the cooling structure only in the area of ​​approximately 30% of the length adjacent to the upper end. In addition, the cooling structure should begin at a distance of less than 50 mm from the upper end of the mold tube.

[0021] In a special embodiment of the cooling structure, the cooling structure extends towards the side surface, i.e., for example, towards the corner of the mold tube or the edge side of the mold plate, and the depth of the groove decreases towards the side surface. Similarly, the cooling structure can also extend in the casting direction, i.e., the depth of the groove decreases gradually. Thereby, a smoother transition between the region with the cooling structure and the region without it is achieved. In this case, the cooling structure can extend over a region larger than 30% in the meniscus region described above or down to 30% below the calculated mold level of the mold body.

[0022] Supplementary or optionally, the V-shaped region can be narrowed in the casting direction by gradually shortening the legs, whereby the legs become geometrically slightly, i.e., small, and in some cases also shallower in depth.

[0023] When the mold body is formed as a mold plate, the described cooling structure, particularly hot spots with particularly high heat loads, can be provided in a plurality of sub-regions. Such sub-regions can start at a distance of 30% of the length of the mold plate or can be arranged adjacent to the lower end.

[0024] A special formation can be realized in the case of a circular mold tube, i.e., a cooling structure that surrounds 360° in the region of the meniscus, whereby the cooling structure is arranged over the entire peripheral region.

[0025] The mold tube according to the present invention is provided in particular for manufacturing a rectangular cross-sectional format. In this case, the mold tube has an outer surface having multiple sides. Cooling structures can be placed on multiple sides, in particular on all sides. Basically, it is possible to form the same cooling structure on all sides. However, the present invention also considers that the sides may have different cooling structures, and that there may be differences in the number and size of the individual grooves. Basically, it is also possible to use cooling structures with different opening angles on each side. In the case of a mold plate having cooling structures in multiple sub-regions, the cooling structures may differ in shape and size from one another, as described above for the mold tube.

[0026] In order to generate vortices, an advantageous development of the present invention is intended to have at least one ridge formed on the outer surface upstream of the groove in the flow direction and optionally additionally downstream of the groove in the flow direction. The ridge may extend over a portion of the length of the groove, preferably over the entire length of the groove. In particular, the ridge is directly adjacent to the groove. The ridge preferably protrudes 0.1 to 2 mm, particularly 0.1 to 1 mm, from the outer surface of the groove. The groove can be manufactured by a roller forming process. During roller forming of the groove, the displaced material can be used to form at least one ridge. The ridge, in particular, has a bead-like cross-section with a radius.

[0027] The present invention presents a mold body (mold tube, mold plate) for casting molten metal, which is made of copper or a copper alloy, has an enhanced heat transfer coefficient in the region of highest thermal stress, i.e., the meniscus region, and can efficiently equalize different cooling capacities, especially around the mold tube. Considering the special usage conditions of the mold tube or mold plate, it has been found that a channel structure arranged in a V-shape with its tip facing in the opposite direction to the flow direction of the cooling medium is advantageous.

[0028] In addition, the mold body according to the present invention corresponds to the type of mold described at the beginning, namely, the mold body is guided within a closed circuit and used in combination with a cooling medium having a flow velocity of 6-14 m / s on the outer surface of the mold, resulting in a heat flux density within a meniscus region of 3-7 MW per square meter. The typical length of the mold body in the form of a mold tube is 700-1200 mm. The cooling water is in contact with the mold body for about 100 ms. During this contact time with the mold tube, it is heated by 6-12 K. The mold wall temperature, in the case of the mold body according to the present invention, is typically 120-300°C on the outside and 250-450°C on the inside. The mold body wall thickness depends on the format and is usually 8-12% of the casting format, preferably 10-35 mm.

[0029] The present invention will be described below with reference to the embodiments illustrated in the schematic drawings. [Brief explanation of the drawing]

[0030] [Figure 1] Perspective view of the mold body in the form of a mold tube according to the first embodiment. [Figure 2] Figure 1: Side view of the upper end of the mold tube [Figure 3] Perspective view of the second embodiment of the mold [Figure 4] Side view of the upper end region of the mold body in Figure 3. [Figure 5] Cross-sectional view of the mold through the groove in Figure 4. [Figure 6] Cross-sectional view of the second embodiment of the groove [Figure 7] Cross-sectional view of the third embodiment of the groove [Figure 8] Cross-sectional view of the fourth embodiment of the groove [Figure 9] A mold in the form of a mold plate. [Figure 10] Perspective view of the mold in Figure 9. [Modes for carrying out the invention]

[0031] Figure 1 shows a mold body 1 in the form of a mold tube for continuous casting of metal. The mold body 1 has a rectangular cross-section, and its walls 3 define a rectangular mold hole 2 extending from the upper end 4 to the lower end 5 of the mold body 1. The mold body 1 is slightly curved in the longitudinal direction L. The casting direction G for liquid metal extends from the upper end 4 to the lower end 5. The outside of the mold body 1 is cooled by cooling water. The flow direction S of the cooling water is opposite to the casting direction G.

[0032] The mold body 1 is made of copper. The mold body has a substantially smooth outer surface 6, except for the cooling structures 7 present on the illustrated sides 8 and 9 of the outer surface 6. The two cooling structures 7 shown on sides 8 and 9 are identical. The same cooling structures 7 are also present on the invisible sides.

[0033] The cooling structure 7 has a length L1 measured in the longitudinal direction L, which corresponds to approximately one-third of the length L2 of the mold tube 1. The cooling structure 7 starts at a distance A1 of approximately 50 mm from the upper end 4.

[0034] Figure 3 shows a detailed side view of the cooling structure 7. The cooling structure 7 consists of a plurality of V-shaped regions 10 arranged sequentially in the longitudinal direction L. Each V-shaped region 10 has two legs 11, 12 of equal length and a tip 13 with a radius R connecting the two legs 11, 12 to each other. The tip 13 is oriented toward the lower end 5, i.e., in the opposite direction to the flow direction S. Thus, in the region below the cooling structure 7, the cooling structure 7 is V-shaped. At the upper end of the cooling structure 7, the cooling structure 7 terminates substantially parallel to its upper width and at a distance from the upper end 4. The length of the legs 11, 12 of the upper V-shaped region 10 gradually decreases toward the center of the side view 8, so that the central V-shaped region 10 becomes substantially smaller and narrower toward the lower, i.e., adjacent V-shaped region 10 in the casting direction.

[0035] The V-shaped region 10 extends over this side 8 of the outer surface 6, over approximately 80% of the measured outer width of side 8 of the mold body 1. The mold body 1 has outwardly rounded corners / edges between adjacent side surfaces 8,9, and these corners / edges do not have cooling structures 7 in the sense of the present invention. The cooling structures 7 terminate at a distance parallel to the rounded edges of the mold body 1.

[0036] In this embodiment, 10 to 20, specifically 17, V-shaped regions 7 are arranged sequentially in the longitudinal direction L. All V-shaped regions 10 have the same opening angle W1, which can be 30° to 150° in the case of a mold tube with the configuration according to the present invention. In this embodiment, the opening angle is 90°. Due to the parallel arrangement and the same opening angle W1, all the legs 12 located on one side of the tip portion 13 or the legs 11 located on the other side are positioned parallel to each other. The legs 11, 12 or V-shaped regions 10 are each formed as grooves 14 on the outer surface 6. Each groove 14 has the same groove width B1 and groove depth T1. Figure 5 shows a cross-section of the groove 14. The groove has a groove width B1 of 4.6 mm and a groove depth T1 of 1.5 mm. The bottom of the groove is formed with a radius of R of 2.5 mm.

[0037] Figure 6 shows an embodiment having a rectangular groove. Here, the groove width B1 is constant, as is the groove depth T1.

[0038] The embodiment in Figure 7 differs from the embodiment in Figure 6 in that, with a constant groove width B1, the groove depth T1 on one side 15 of the groove 14 is greater than the groove depth T1 on the opposite side 16, which has a groove depth T2. As a result, the cross-section is trapezoidal. On the screen, the lower side 15 is the side from which the coolant first flows.

[0039] The groove width B1 is in the range of 2 to 10 mm, but the groove depth is in the range of 0.1 to 2 mm. In the embodiments of Figures 5 and 6, the description of groove depth refers to the deepest part of the groove. In the embodiment of Figure 7, the smaller groove depth T2 is at least 0.1 mm. The groove depth T2 on the other side 15 is larger.

[0040] The distance A2 between the two parallel legs 11 and 12 is the same as the groove width B1. The distance A2 is measured perpendicular to the longitudinal path of the legs 11 and 12.

[0041] In the embodiments shown in Figures 1 and 2, the arrangement of the cooling structure 7 with respect to each side 8 and 9 is mirror-symmetric with respect to the central longitudinal axis of each side 8 and 9. The cooling structure 7 is at the same distance from the left and right edges of the side 8 and 9, respectively, and the legs 11 and 12 are always the same length, so that the tip 13 is always located within the central longitudinal axis on each side 8 and 9.

[0042] Figures 2 and 4 show selective embodiments in which the mold body 1, i.e., the mold tube, has the same basic shape, length, and form. Therefore, refer to the description of the embodiments in Figures 1 and 3. The difference lies in the differently configured cooling structures 7a, which have multiple V-shaped regions 10a to c arranged side by side with respect to the longitudinal direction. Each of the V-shaped regions 10a to c has a tip portion 13a to c and leg portions 11a to c, 12a to c. The adjacent leg portions 11a to b, 12b to c are connected to each other by an arc portion 17, thereby creating a wave structure. Since all the leg portions 11a to c, 12a to c are the same length, a uniform wave structure is obtained. The arc portion 17 and the tip portions 13a to c are formed identically.

[0043] In this embodiment, the cooling structure 7a has the same width as the cooling structure 7 in the first embodiment. The cooling structure 7a begins at the same distance A1 from the upper end 4 of the casting tube 1. The lower end of the cooling structure 7a is somewhat wavy, but not perfectly V-shaped, as in the embodiment of Figure 1, due to the presence of significantly small triple V-shaped regions 10a-c. However, even in this case, the cooling structure 7a extends over approximately one-third of the length L of the mold body 1. For the structure of the V-shaped regions 10a-c, refer to the description in Figures 5-7 showing possible cross-sections of the groove 14.

[0044] With respect to the opening angle W1 and distance A2 of the longitudinally continuous V-shaped regions 10a to c, refer to the description of the first embodiment. Accordingly, the configurations in Figures 2 and 4 show not only the V-shaped regions 10 arranged side by side in the longitudinal direction L, but also additionally the V-shaped regions arranged in the longitudinal direction L in a front-to-back direction. In this embodiment, there are 14 V-shaped regions arranged in a front-to-back direction in the longitudinal direction, and 3 V-shaped regions 10a to c arranged side by side.

[0045] As shown in the embodiments in Figures 1 and 2, the cooling structure 7a flows from below, that is, in the direction opposite to the casting direction G.

[0046] Figure 8 shows an embodiment having an additional raised portion 18 on the outer surface 6, where the raised portion 18 is located upstream of the groove 14 in the flow direction S. The raised portion 18 has a height H1 of 0.1 to 1 mm. The raised portion has a semicircular cross-section and is adjacent to the groove 14 directly, i.e., without any distance. The raised portion is used to generate vortices.

[0047] Figures 9 and 10 show a mold plate in two different diagrams as another example of the mold body 1 having the cooling structure 7. The cooling structure is positioned at a distance from the upper end 4 and lower end 5 and is located on the outer surface 6 at the height of the meniscus. The cooling structure 7 extends over only a portion of the length of the mold plate, but extends over almost the entire width of the mold plate. The coolant flow direction S is from the lower end 5 to the upper end 4 of the mold body 1. A total of six identical V-shaped regions are arranged side by side in the lateral direction, and seven V-shaped regions are arranged front to back in the longitudinal direction. The side by side regions are connected to each other, thereby creating a zigzag structure on the outer surface 6. [Explanation of Symbols]

[0048] 1. Mold 2 mold hole 3 1 wall 4. Upper end of 1 5 1 Lower end 6. Outer surface of 1 7 6 cooling structure 7a Cooling structure 8 6 side 9 6 side 10 V-shaped area 10a V-shaped area 10b V-shaped area 10c V-shaped area 11 10 legs 11a Legs of 10 11b 10 legs 11c 10 legs 12 10 legs 12a 10 Legs 12b 10 legs 12c 10 legs 13 10 tip 13a 10 tip 13b Tip of 10 13c 10 tip 14 groove 15 14 side 16 14 side 17 Arc 18 Ridge Distance between A1 7,7a and 4 L Longitudinal direction Length of L1 7,7a Length L2 1 G Casting direction S flow direction A2 Distance between 10 and 10 B1 14 width H1 18 Height Depth of T1 14 Depth of T2 14 W1 Opening angle

Claims

1. A mold body (1) for continuous casting of metal, having a longitudinal direction (L) between an upper end (4) and a lower end (5) in the casting direction, wherein at least one partial region of the outer surface (6) of the mold body (1) is provided with a cooling structure (7, 7a) to improve cooling, and the cooling structure (7, 7a) comprises at least one V-shaped region (10, 10a-c) having two opposing legs (11, 11a-c, 12, 12a-c) and one tip (13, 13a-c) that form an opening angle (W1), and the tip (13, 13a-c) is directed toward the lower end (5), A mold body (1) characterized in that a V-shaped region (10, 10a-c) is formed as a groove (14) on the outer surface (6), and has a groove width (B1) and groove depth (T1, T2).

2. The mold body (1) according to claim 1, characterized in that a plurality of V-shaped regions (10, 10a to c) are arranged in a series of front-to-back directions in the longitudinal direction (L) and / or side-by-side with respect to the longitudinal direction (L).

3. The mold body (1) according to claim 2, characterized in that V-shaped regions (10a to c) arranged in a row are connected to each other to form a wave structure.

4. A mold body (1) according to any one of claims 1 to 3, characterized in that the number of V-shaped regions (10a to c) arranged side by side in the longitudinal direction (L) is 1 to 50, particularly 1 to 10.

5. A mold body (1) according to any one of claims 1 to 4, characterized in that the opening angle (W1) of the V-shaped region is within the range of 30° to 150°.

6. A mold body (1) according to any one of claims 1 to 5, characterized in that the tip portions (13, 13a to c) are given a radius.

7. A mold body (1) according to any one of claims 1 to 6, characterized in that the legs (11, 11a to c, 12, 12a to c) of two V-shaped regions (10, 10a to c) arranged sequentially in the longitudinal direction (L) extend parallel to each other.

8. A mold body (1) according to any one of claims 1 to 7, characterized in that the groove width (B1) is in the range of 2 to 10 mm and the groove depth (T1, T2) is in the range of 0.1 to 2 mm.

9. A mold body (1) according to any one of claims 1 to 8, characterized in that the groove depth (T1) on the side (15) through which the coolant flows in the groove (14) is greater than that on the other side (16) of the groove (14).

10. A mold body (1) according to any one of claims 1 to 9, characterized in that the distance (A2) between the legs (11, 11a to c, 12, 12a to c) that extend parallel to each other in adjacent V-shaped regions (10, 10a to c) is at least equal to the groove width (B1).

11. The mold body (1) according to any one of claims 1 to 10, characterized in that the mold body (1) has a length (L2) from an upper end (4) to a lower end (5), and the cooling structure (7, 7a) extends over a maximum of 30% of the length (L2).

12. The mold body (1) according to any one of claims 1 to 11, characterized in that the cooling structure (7, 7a) begins at a distance (A1) of less than 50 mm from the upper end (4).

13. The mold body (1) according to any one of claims 1 to 12, characterized in that the mold body (1) is a mold tube, its outer surface (6) has a plurality of sides (8, 9), and cooling structures (7, 7a) are arranged on the plurality of sides (8, 9), with the sides (8, 9) having different cooling structures (7, 7a).

14. The mold body (1) according to claim 13, characterized in that the cooling structure (7, 7a) has different opening angles (W1).

15. The mold body (1) according to any one of claims 1 to 13, characterized in that the mold body (1) is a mold plate.

16. A mold body (1) according to any one of claims 1 to 15, characterized in that a raised portion (18) is formed on the outer surface (6) upstream of the groove (14) in the flow direction (S) and optionally additionally downstream of the groove (14).

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