Ingot mould with partially coated ingot mould

Abstract

A mold for continuous casting of metals is bounded by mold plates, between which molten metal is poured into a metal strand. At least one mold plate is provided with a full-surface, wear-resistant coating on the outlet side, at least in an inner zone extending in the casting direction. The mold plate has an inlet-side area that is either uncoated or at least partially coated with a patterned coating. A boundary line between the inlet-side area and the full-surface coating on the outlet side is at least partially inclined relative to a transverse direction of the mold oriented perpendicular to the casting direction.

Description

[0001] The invention relates to a mold for continuous casting of metals.

[0002] Continuous casting is a continuous casting process in which metal is poured through a bottomless mold (chill) and drawn off at the outlet of the mold with a solidified shell and usually still molten core. Both ferrous alloys (e.g., steels) and non-ferrous alloys, such as copper alloys or aluminum, can be continuously cast.

[0003] While molds for smaller cross-sections (e.g. for casting billets) are usually designed as a tube or shaped tube, molds for larger cross-sections (e.g. for casting slabs or pre-blocks) often consist of individual plates.

[0004] High heat dissipation must be ensured in the inlet area of ​​the mold to enable high throughput (high casting speed). The strand shell forms in this area. Further along the mold, lower heat dissipation can be tolerated, while higher demands are placed on the wear resistance of the mold walls.

[0005] In the area of ​​the mold where the strand shell is forming and is still thin, there is a risk of the thin strand shell tearing. This risk should be minimized to ensure high production reliability.

[0006] It is known to provide mold plates in the outlet-side area with a wear-resistant coating in order to reduce plate wear occurring during the casting process and, if necessary, to create improved sliding properties of the surface.

[0007] The coating reduces heat dissipation in the outlet area, but this can be tolerated due to the lower requirements in this area.

[0008] Excessive wear can occur in the transition area between the uncoated and coated sections of the die plate. This wear primarily affects the uncoated portion just before the transition to the coating. Even if the rest of the die plate shows no damage, this area may be so severely damaged that the entire surface of the die plate facing the extrusion strand requires reworking.

[0009] CN 110076306 A describes a fully coated die plate with different coating thicknesses in the inlet and outlet areas.

[0010] EP 3 213 838 B1 describes a mold plate which incorporates filler material sections in the inlet area to achieve either lower or higher heat dissipation. The mold plate may be coated, and this coating may also be present in the inlet area.

[0011] One of the underlying objectives of the invention can be seen as creating a wear-optimized mold that meets the requirements for heat dissipation.

[0012] The problem addressed by the invention is solved by the features of claim 1. Exemplary embodiments and further developments are the subject of the dependent claims.

[0013] Accordingly, a mold for continuous casting of metals is bounded by mold plates between which molten metal is poured to form a metal strand. At least one mold plate is provided with a full-surface, wear-resistant coating on the outlet side, at least in an inner zone extending in the pouring direction. The mold plate has an inlet-side area that is either uncoated or at least partially coated with a patterned coating. A boundary line between the inlet-side area and the full-surface coating on the outlet side is at least partially inclined relative to a transverse direction of the mold oriented perpendicular to the pouring direction.

[0014] The uncoated or at least partially coated inlet area ensures high heat dissipation. The full-surface, wear-resistant coating in the outlet area effectively protects this mechanically more stressed region from wear. The boundary line between the two areas, which runs at least partially diagonally, ensures that the transition from the softer, uncoated to the harder, fully coated area extends over a certain distance, thus providing increasing support for the strand shell in the casting direction. This prevents excessive wear of the uncoated inlet area in the casting direction upstream of the boundary line, which would occur with a boundary line running perpendicular to the casting direction (i.e., transversely to the mold).

[0015] In particular, this measure can prevent a mold plate from showing damage in the area just before the boundary line after a relatively short period of use, thus preventing the need for rework (e.g., rewelding), even if the rest of the mold plate is still undamaged. In other words, the at least partial inclination of the boundary line mitigates the wear-critical area of ​​the mold just before the (usually transverse) boundary line.

[0016] Furthermore, at least partially tilting the boundary line may reduce the risk of the strand shell tearing open.

[0017] The boundary line can contain a plurality of line flanks rising obliquely in the casting direction and a plurality of line flanks descending obliquely in the opposite casting direction, with rising and descending line flanks arranged alternately. Such structures make it possible to gradually build up the support of the strand shell caused by the coating over a certain transition region.

[0018] The angle between an ascending line flank and a descending line flank can be, for example, between 40° and 140°, and in particular between 70° and 110°. The length of the transition region can be influenced by choosing the angle.

[0019] For example, the boundary line may, at least in sections, have a jagged, wavy, crenellated or otherwise varying shape in the direction of casting.

[0020] The variation in the boundary line profile, measured in the casting direction as the distance between the inlet-side and outlet-side reversal points of the boundary line profile, can, for example, lie in a range between 30 and 200 mm, particularly between 60 and 150 mm. This variation can correspond to the length of the transition region in which the support of the strand shell (at least in the inner zone) is built up to 100%.

[0021] Measured transversely to the mold, the variation width of the boundary line profile, measured as the distance between adjacent outlet-side reversal points of the boundary line profile, can range between 30 and 200 mm, particularly between 60 and 150 mm. Thus, for example, a variation width can be set that essentially corresponds to the variation height of the boundary line profile (e.g., with a deviation equal to or less than 50%, 30%, 20%, or 10%). However, it is also possible to select a variation width that differs significantly from the variation height.

[0022] The inlet-side area can be completely uncoated in the inner zone extending in the casting direction (which can also extend across the entire width of the plate). However, it is also possible for this area to be at least partially coated with a coating pattern, such as striped coating structures. This coating pattern allows for partial support of the strand shell in the inlet-side area before the transition region.

[0023] If the coating pattern has strip-shaped coating structures, these can be designed to intersect.

[0024] Intersecting, strip-shaped coating structures, or other methods, can be used to create a coating pattern that defines an array of island-like, uncoated areas on the mold plate. It can be advantageous if the boundary lines of these areas are oriented obliquely relative to the transverse direction of the mold. This allows the wear-reducing effect of oblique boundary lines between coated and uncoated areas to be applied locally to the uncoated areas of the mold plate within the coating pattern.

[0025] In particular, it is possible that the entire boundary line course and / or all edge lines of fields have no sections oriented in the transverse direction.

[0026] Examples and embodiments of the invention are explained in more detail below with reference to the drawings. The elements in the drawings are not necessarily to scale. Identical reference numerals denote corresponding or similar parts. The features of the various illustrated embodiments can be selectively combined, provided they are not mutually exclusive, and / or they can be selectively omitted if they are not described as absolutely necessary. Figure 1 shows a schematic cross-sectional view of an example of a mold. Figure 2 shows a diagram in which the desired local heat flux density is plotted as a function of the mold length. Figure 3 shows a first example of a mold plate with uncoated and coated areas in a top view. Figures 4A to 4CThe diagrams show exemplary curves of the boundary line between the uncoated area and the coated area. Figure 5 shows a second example of a mold plate with uncoated and coated areas in a top view. Figure 6 A third example of a mold plate with uncoated and coated areas in a top view is shown.

[0027] Figure 1 Figure 1 shows an exemplary cross-section through a mold 100. The mold 100 is a casting form by means of which a metal strand 120 is formed from molten metal 110. The process is continuous, i.e., the molten metal 110 is introduced, for example, by means of a casting tube 130 into the inlet-side region 101 of the mold 100, from which the metal strand 120 emerges in an outlet-side region 102. The emerging metal strand 120 has a shape that is determined by the casting form (mold 100).

[0028] Within the mold 100, a strand shell 122 forms in the inlet-side area 101 due to cooling on the mold walls. This shell must have sufficient stability in the outlet-side area 102 to allow further processing of the metal strand 120 after it exits the mold 100, for example, to guide it and, if necessary, redirect it in a large arc. The strand shell 122 surrounds the liquid core (molten metal 110) of the metal strand 120, which is usually still present at the outlet of the mold 100. After the metal strand 120 has solidified completely, it can then be cut into individual slabs (not shown).

[0029] The mold 100 can, for example, have four mold plates that define the mold 100 in all directions transverse to the pouring direction. A known design consists of two opposing broad side plates and two opposing narrow side plates. The broad side plates and narrow side plates can be oriented perpendicular to each other, meaning the mold 100 can have a rectangular cross-section. In the Figure 1 The plates shown 105, 106 can alternatively be either opposing broadside plates or opposing narrowside plates.

[0030] The broad side panels 105, 106 have a larger transverse dimension than the narrow side panels 105, 106. The invention will now be explained with reference to broad side panels, without limitation of generality.

[0031] Figure 2This illustrates the heat dissipation requirements in a mold 100 along the mold length (in mm) using various steels. High heat dissipation is required in the area directly below the casting surface (meniscus M), as shown in the circled area. Heat dissipation can be lower in the outlet-side area 102, but here, due to the already stable strand shell, higher demands are placed on the wear resistance of the plates 105, 106.

[0032] The representation in Figure 2This refers to a low-carbon steel grade that is cast at varying speeds (in meters per minute) in mold 100. Similar quality requirements can apply to all metals and / or molds 100. The higher the casting speed, the greater the demands on the mold 100's ability to effectively dissipate heat, particularly in the inlet area 101.

[0033] Figure 3 Figure 1 shows a first example of a mold plate 105_1. The mold length (corresponding to the length of the mold plate 105_1) is denoted by KL. The width of the mold plate 105_1 is B. The pouring direction runs in the direction of the mold length KL.

[0034] The inlet-side area 101 of the mold plate 105_1 is uncoated in the example shown here (uncoated areas are shown hatched). It borders an outlet-side area 102, which is fully coated (shown without hatching). In the Figure 3 In the example shown, both areas extend over the entire width B of the mold plate 105_1.

[0035] A boundary line G between the inlet-side, uncoated area 101 and the outlet-side, coated area 102 is at least partially inclined relative to the transverse direction (width) of the mold 100. In the example shown here, the boundary line G has exclusively inclined sections. However, it is also possible that the boundary line G also has sections oriented perpendicular to the casting direction (i.e., in the transverse direction).

[0036] For example, the boundary line G, at least in an inner zone Z extending in the pouring direction, can contain a plurality of line flanks G1 rising obliquely in the pouring direction and a plurality of line flanks G2 descending obliquely in the opposite pouring direction, or it can be formed solely from such line flanks. The rising and descending line flanks G1, G2 can alternate. In particular, the boundary line G, at least in the inner zone Z, can be realized in a zigzag shape, as shown in Figure 3 This is shown as an example.

[0037] An angle α between an ascending line flank G1 and a descending line flank G2 can, for example, be between 40° and 140°, preferably 70° and 110°.

[0038] Further characteristics defining the boundary line profile can include a variation height (VH) and a variation width (VB) of the boundary line (G). The variation height (VH) is measured in the pouring direction as the distance between inlet-side and outlet-side reversal points of the boundary line profile (G). The variation width (VB) is calculated as the distance between adjacent outlet-side reversal points of the boundary line profile (G).

[0039] Both the variation height (VH) and the variation width (VB) can vary over a wide range. In particular, they can each, for example, lie in a range between 30 and 200 mm, preferably more preferably between 60 and 150 mm.

[0040] The variance height (VH) can be essentially equal to the variance width (VB), however, it is also possible that the variance height (VH) is greater or – as in the example in Figure 3 The example shown is smaller than the range of variation VB.

[0041] The inner zone Z can, for example, be equal to or greater than 50%, 60%, 70%, 80%, or 90% of the width B of the mold plate 105_1, or correspond to the entire width (100%) of the mold plate 105_1.

[0042] The Figures 4A to 4C Figure 1 shows further possible boundary line profiles G between the inlet-side region 101 and the outlet-side region 102 of the mold 100. All boundary line profiles G can be periodic. The period length can be constant or vary along the boundary line profile. The period length corresponds to that in Figure 3 The variation range VB (which can also vary between different reversal points) is explained using a zigzag-shaped boundary line G.

[0043] Figure 4A shows a wavy boundary line profile G. A boundary line profile G is also possible, which has peaks at the outlet-side reversal points and curves at the inlet-side reversal points, see [reference]. Figure 4B It is also possible to create the outlet-side reversing points with curves and the inlet-side reversing points with points. In general, the inlet-side and / or outlet-side reversing points can be, for example, obtuse-angled, acute-angled, curved, acutely curved, or shallow-arched.

[0044] Figure 4C shows another example of a boundary line G, which is designed in a crenellated manner, with the individual crenellations being trapezoidal or having sloping side wall sections.

[0045] Furthermore, it illustrates Figure 4CIn an exemplary manner, the boundary line G can also run transversely to mold 100 in sections. A boundary line profile G that includes both transverse and oblique sections is possible for all boundary line profiles G shown here as examples. The reversal points of the boundary line profile G of the Figure 4C are realized as the transverse sections of the boundary line, i.e., not by turning points (as, for example, in the Figures 4A and 4B shown), but formed by straight reversal sections.

[0046] The in the Figures 4A to 4C The exemplary boundary line profiles G shown can be combined in any way.

[0047] In the transition region of length VH in the casting direction, the support of the strand shell 122 by the coating builds up to 0% at least in the inner zone (if the inlet-side area 101 is as in Figure 3(shown without coating pattern) continuously increases to 100%. The transition region can also be described as an area that is at least partially coated in the inner zone Z, which has uncoated free areas that taper in the casting direction.

[0048] Figure 5 Figure 1 shows a top view of a mold plate 105_2, which differs from mold plate 105_1 primarily in that the coating (unhatched area) extends from the edge of mold plate 105_2 to the inlet-side edge. Since the edge areas of mold plate 105_2 offer more favorable conditions for high heat dissipation due to the presence of other mold plates (e.g., narrow-side mold plates), a coating may also be possible in the inlet-side area 101. As shown in Figure 3However, in this example too, there is an inner zone Z within which the boundary line G between the areas 101 and 102 is at least partially oblique to the transverse direction of the mold plate 105_2.

[0049] Figure 6 shows a further embodiment of a mold plate 105_3, which differs from the mold plate 105_2 of the Figure 5 The main difference is that the inlet-side area 101 is at least partially (in the example shown here completely) coated with a coating pattern.

[0050] The coating pattern, for example, features strip-shaped coating structures S. However, the coating structures S can also be curved or implemented in other shapes.

[0051] The coating structures S can intersect. For example, this can form an array-shaped coating pattern of island-shaped, uncoated fields F of the mold plate 105_3.

[0052] The coating pattern can be - as in Figure 6 As illustrated by example, it can be regular. In these and other cases, it can have a constant coating area (or a constant uncoated area (e.g., given by fields F)).

[0053] As already described, a boundary line G between the inlet-side area 101 and the outlet-side full-surface coating (area 102) is at least partially inclined relative to the transverse direction of the mold plate 105_3. Edge lines of fields F can also be oriented inclined relative to the transverse direction of the mold plate 105_3. In particular, it is possible that all edge lines of fields F are oriented inclined relative to the transverse direction of the mold plate 105_3. Edge lines of fields F can at least partially form the boundary line between the inlet-side area 101 and the outlet-side area 102.

[0054] At the in Figure 6In the example shown, the coating structures present in the inlet-side area 101 already provide increased support for the metal strand 120. As in the previous examples, a transition region of length VH also occurs here in the casting direction, across which the support for the metal strand 120 increases continuously from a coating area fraction determined by the coating pattern to 100%.

[0055] The mold plates 105, 105_1, 105_2, 105_3, 106 can be made of a material with good heat conductivity, for example, copper or a copper alloy (e.g., a copper-silicon alloy or a copper-chromium-zirconium alloy). The coating can be a metal coating, for example, a nickel-based alloy or a chromium-based alloy. In particular, the coating can be a NiCrBSi alloy. Alternatively, the coating can be made of a carbide or ceramic material, for example. The coating is applied to the mold plate 105, 105_1, 105_2, 105_3, 106 in such a way that the surface of the (uncoated) mold plate 105, 105_1, 105_2, 105_3, 106 and the surface of the coating meet seamlessly.

[0056] The coating typically has a higher hardness than the softer sheet material. For example, the coating may be a hard coating or it may contain hard materials (e.g., carbides) that increase the coating's wear resistance.

[0057] The dimensions KL and B of the mold plate 105, 105_1, 105_2, 105_3, 106 can vary considerably. For example, the length KL of the mold plate 105, 105_1, 105_2, 105_3, 106 can be approximately 900 mm. The width B of the mold plate 105, 105_1, 105_2, 105_3, 106 is highly variable and can range, for example, from 1750 to 2480 mm. Plate widths B of up to approximately 4000 mm are also possible.

[0058] By creating a transition region with a continuously increasing proportion of the coating area, a sharp separation from soft to hard along a transverse boundary line can be avoided as described. Instead, a transition region with lower local wear is created along the varying boundary line G. Furthermore, the risk of tearing of the thin strand shell 122 is potentially reduced, thereby increasing production reliability (lower risk of strand shell 122 or strand skin failure).

[0059] Furthermore, a coating pattern, e.g. checkerboard-like (see Figure 6) or honeycomb-shaped uncoated fields F in the inlet-side area 101 of the mold 100, good heat dissipation with simultaneously good wear resistance is achieved. By means of sloping edge lines of fields F, the aforementioned advantages of sloping boundary line sections can also be achieved in the inlet-side area 101.

[0060] All of the measures shown here as examples, especially with regard to the boundary line G and the (optional) coating pattern, can be combined with each other.

[0061] Furthermore, the coating pattern, if present, does not have to cover the entire inlet-side area 101. Rather, for example, an upper section of the inlet-side area 101, starting at the inlet-side end of the mold plate, may be uncoated, and the coating pattern (e.g., the strip-shaped coating structures S) may only be realized in a subsequent area in the casting direction. It is equally possible that a coating pattern is present at the inlet-side end of the mold plate and that the area between the coating pattern and the boundary line G is as shown in Figure 3 A completely uncoated area of ​​the plate exists.

Claims

1. A mold for the continuous casting of metals, wherein the mold is delimited by mold plates between which a molten metal is cast to form a metal strand, wherein at least one mold plate, in particular at least two opposing mold plates, is provided at least in an inner zone extending in the casting direction with a full-surface, wear-resistant coating on the outlet side and has an inlet-side region which is uncoated or at least partially coated with a coating pattern, and a boundary line between the inlet-side region and the full-surface coating on the outlet side is at least partially oblique with respect to a transverse direction of the mold oriented perpendicular to the casting direction.

2. The mold according to claim 1, wherein the boundary line includes a plurality of line flanks rising obliquely in the casting direction and a plurality of line flanks falling obliquely in the counter-casting direction, wherein rising and falling line flanks are arranged alternately.

3. Mould according to claim 2, wherein an angle between a rising line flank and a falling line flank is between 40° and 140°, in particular 70° and 110°.

4. Mould according to one of the preceding claims, wherein the boundary line at least in sections contains a jagged, wavy, crenellated or otherwise varying boundary line course in the casting direction.

5. Mould according to claim 4, wherein a variation height of the boundary line course, measured in the casting direction as the distance between the inlet-side and outlet-side reversal points of the boundary line course, lies in a range between 30 and 200 mm, in particular 60 and 150 mm.

6. Mould according to claim 4 or 5, wherein a variation width of the boundary line course, measured in the transverse direction of the mould as the distance between adjacent outlet-side reversal points of the boundary line course, lies in a range between 30 and 200 mm, in particular 60 and 150 mm.

7. Mould according to one of the preceding claims, wherein the inlet-side region is at least partially coated with the coating pattern which has strip-shaped coating structures.

8. Mould according to claim 7, wherein strip-shaped coating structures intersect.

9. A mold according to any one of claims 7 or 8, wherein the coating pattern defines an array of island-shaped, uncoated fields of the mold plate.

10. Mould according to claim 9, wherein edge lines of fields are oriented obliquely with respect to the transverse direction of the mould.

11. Mould according to one of the preceding claims, wherein the coating is a metal coating, in particular made of a nickel-based alloy or a chromium-based alloy, a carbide or a ceramic coating.

12. Mould according to one of the preceding claims, wherein the mould is delimited by four mould plates, namely two opposing narrow side plates and two opposing broad side plates, wherein the mould plate is a broad side plate.

13. Mould according to one of the preceding claims, wherein the mould is intended for the continuous casting of steel alloys.

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