Mold having partially coated mold plate

Abstract

A mold for continuous casting of metals is delimited by mold plates, between which a molten metal is cast to form a metal strand. At least one mold plate is provided with an exit-side full-surface wear-resistant coating, at least in an inner zone extending in the casting direction. The mold plate has an entry-side region which is uncoated or at least partially coated with a coating pattern. A boundary line between the entry-side region and the exit-side full-surface coating extends, at least in parts, obliquely with respect to a transverse direction of the mold, said transverse direction being perpendicular to the casting direction. The boundary line contains a plurality of line flanks rising obliquely in the casting direction and a plurality of line flanks falling obliquely in the direction opposite the casting direction, rising and falling line flanks being arranged in alternation.

Description

[0001] Mould with partially coated mould plate

[0002] The invention relates to a mold for the continuous casting of metals.

[0003] Continuous casting is a continuous casting process in which metal is poured through a bottomless mold (die) and drawn off at the mold outlet with a solidified shell and usually still a liquid core. Both ferrous alloys (e.g., steels) and non-ferrous alloys, such as copper alloys or aluminum, can be continuously cast.

[0004] While molds for smaller cross-sections (e.g. for casting billets) are usually designed as tubes or shaped tubes, molds for larger cross-sections (e.g. for casting slabs or blooms) often consist of individual plates.

[0005] In the inlet area of ​​the mold, high heat dissipation must be ensured 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.

[0006] In an area of ​​the mold where the strand shell is forming and is still thin, there is a risk of the thin strand shell tearing open. To ensure high production reliability, this risk should be kept as low as possible.

[0007] It is known to provide mold plates in the outlet soapy area with a wear-resistant coating in order to reduce the plate wear occurring during the casting process and, if necessary, to create an improved sliding properties of the surface.

[0008] The coating reduces heat dissipation in the soapy area, which can be tolerated due to the lower requirements in this area.

[0009] Excessive wear of the mold plate can occur in the transition zone between the uncoated portion of the mold plate and the coating. This wear occurs primarily in the uncoated section just before the transition to the coating. Even if the rest of the mold plate shows no damage, this area of ​​the plate may be so severely damaged that the entire surface of the mold plate facing the strand must be reworked.

[0010] CN 110076306 A describes a fully coated mold plate with different coating thicknesses in the inlet and outlet areas.

[0011] EP 3 213 838 B1 describes a mold plate with filler material sections in the inlet area to achieve greater or lesser heat dissipation. The mold plate can be provided with a coating that is also present in the inlet area.

[0012] One object underlying the invention can be seen in the creation of a wear-optimized mold that meets the requirements for heat dissipation. The object underlying the invention is solved by the features of claim 1. Examples and further developments are the subject of the dependent claims.

[0013] Accordingly, a mold for the continuous casting of metals is delimited by mold plates, between which a molten metal is poured to form a metal strand. At least one mold plate is provided, at least in an inner zone extending in the casting direction, with a soapy, full-surface, wear-resistant coating. The mold plate has a soapy inlet region which is uncoated or at least partially coated with a coating pattern. A boundary line between the soapy inlet region and the soapy, full-surface coating runs at least in sections obliquely with respect to a transverse direction of the mold oriented perpendicular to the casting direction. The boundary line contains a plurality of line flanks which rise obliquely in the casting direction and a plurality of line flanks which fall obliquely in the opposite casting direction, with rising and falling line flanks being arranged alternately.

[0014] The inlet soapy area is uncoated or at least partially coated with a coating pattern, which ensures high heat dissipation in this area. The full-surface, wear-resistant coating in the outlet soapy area makes it possible to effectively protect this area, which is subject to higher mechanical stress, from wear. The boundary line between the two areas, which runs diagonally at least in sections, ensures that the transition from the softer, uncoated area to the harder, fully coated area extends over a certain distance, over which increasing support of the strand shell is achieved in the casting direction. This prevents excessive wear of the inlet-side uncoated area in front of the boundary line in the casting direction, which occurs with a boundary line running normal to the casting direction (i.e. in the transverse direction of the mold).

[0015] In particular, this measure can prevent a mold plate from developing damage in the area just before the boundary line after a relatively short period of use, requiring rework (e.g., rewelding), even if the rest of the mold plate is not yet damaged. In other words, by tilting the boundary line at least in sections, the wear-critical area of ​​the mold just before the boundary line (which usually runs transversely) is mitigated.

[0016] In addition, the inclination of the boundary line, at least in sections, may possibly reduce the risk of the strand shell tearing open.

[0017] The majority of line flanks rising obliquely in the casting direction and the majority of line flanks falling obliquely in the counter-casting direction, which are arranged alternately, ensure that the support of the strand shell caused by the coating is increasingly built up over a certain transition region.

[0018] The angle between a rising line flank and a falling line flank can, for example, be between 40° and 140°, in particular between 70° and 110°. The length of the transition region can be influenced by the choice of the angle. For example, the boundary line can, at least in sections, contain a jagged, wavy, crenellated, or otherwise varying boundary line shape in the casting direction.

[0019] A variation height of the boundary line profile, measured in the casting direction as the distance between the inlet and outlet reversal points of the boundary line profile, can, for example, be in a range between 30 and 200 mm, in particular 60 and 150 mm. The variation height 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%.

[0020] Measured in the transverse direction of the mold, the variation width of the boundary line, measured as the distance between adjacent outlet-side reversal points of the boundary line, can be in a range between 30 and 200 mm, in particular 60 and 150 mm. Thus, for example, a variation width can be set that essentially corresponds (e.g., with a deviation equal to or less than 50%, or 30%, or 20%, or 10%) to the variation height of the boundary line. However, it is also possible to select a variation width that deviates significantly from the variation height.

[0021] The inlet-facing region can be completely uncoated in the inner zone extending in the casting direction (which can also extend across the entire plate width); however, it is also possible for this region to be at least partially coated with a coating pattern having, for example, strip-shaped coating structures. The coating pattern makes it possible to partially support the strand shell in the inlet-facing region before the transition region. If the coating pattern has strip-shaped coating structures, these can be designed so that they intersect.

[0022] Through intersecting strip-shaped coating structures or in other ways, the coating pattern can be achieved to define an array of island-shaped, uncoated fields on the mold plate. It can be advantageous if the edge lines of the fields are oriented diagonally relative to the transverse direction of the mold. This allows the wear-reducing effect of diagonal boundary lines between coated and uncoated areas to be applied locally to the uncoated fields of the mold plate in the coating pattern.

[0023] In particular, it is possible that the entire boundary line and / or all edge lines of fields do not have any sections oriented in the transverse direction.

[0024] Examples and possible 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. Like reference numerals designate corresponding or similar parts. The features of the various illustrated embodiments may be selectively combined, provided they are not mutually exclusive, and / or they may be selectively omitted unless described as absolutely necessary.

[0025] Figure 1 shows a schematic cross-sectional view of an example of a mold. Figure 2 shows a diagram plotting the desired local heat flux density as a function of the mold length.

[0026] Figure 3 shows a first example of a mold plate with uncoated and coated areas in plan view.

[0027] Figures 4A to 4C show exemplary courses of the boundary line between the uncoated area and the coated area.

[0028] Figure 5 shows a second example of a mold plate with uncoated and coated areas in plan view.

[0029] Figure 6 shows a third example of a mold plate with uncoated areas and areas coated with a coating pattern in plan view.

[0030] Figure 1 shows, by way of example, a cross-section through a mold 100. The mold 100 is a casting mold 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 pouring tube 130 into the inlet 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 predetermined by the casting mold (mold 100).

[0031] Within the mold 100, a strand shell 122 forms on the mold walls in the inlet region 101 as a result of the cooling process. This strand shell 122 must have sufficient stability in the outlet region 102 to enable the metal strand 120 to be further processed after it has exited the mold 100, for example to guide it and, if necessary, to deflect 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 on the outlet side of the mold 100. After the metal strand 120 has completely solidified, it can then be cut into individual slabs (not shown).

[0032] The mold 100 can, for example, have four mold plates that delimit the mold 100 in all directions transverse to the casting direction. A structure comprising two opposing broad side plates and two opposing narrow side plates is known. The broad side plates and narrow side plates can be oriented perpendicular to one another, i.e., the mold 100 can have a rectangular cross-section. The plates 105, 106 shown in Figure 1 can alternatively be either opposing broad side plates or opposing narrow side plates.

[0033] Broadside plates 105, 106 have a greater extent in the transverse direction than narrowside plates 105, 106. In the following, the invention is explained with reference to broadside plates without restricting generality.

[0034] Figure 2 illustrates the requirements for heat dissipation in a mold 100 along the mold length (in mm) using various steels. In the area directly below the casting level (meniscus M), high heat dissipation is required; see the circled area. In the outgoing, soapy area 102, heat dissipation may be lower; however, higher demands are placed on the wear resistance of the plates 105, 106 due to the already stable strand shell.

[0035] The illustration in Figure 2 refers to a steel grade with a low carbon content, which is cast at different speeds (in meters per minute) in the mold 100. Similar qualitative requirements can apply to all metals and / or molds 100. The higher the casting speed, the higher the requirements for the ability of the mold 100 to effectively dissipate heat, particularly in the soapy inlet area 101.

[0036] Figure 3 shows a first example of a mold plate 105_l. The mold length (corresponding to the length of the mold plate 105_l) is designated KL. The width of the mold plate 105_l is B. The casting direction runs in the direction of the mold length KL.

[0037] The inlet-soapy region 101 of the mold plate 105_l is uncoated in the example shown here (uncoated regions are shown hatched). It borders on an outlet-soapy region 102, which is fully coated (shown without hatching). In the example shown in Figure 3, both regions extend across the entire width B of the mold plate 105_l.

[0038] A boundary line G between the inlet soapy, uncoated region 101 and the outlet soapy, coated region 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 for the boundary line G to also have sections oriented normal to the casting direction (i.e., in the transverse direction).

[0039] The boundary line G contains, for example, at least in an inner zone Z extending in the casting direction, a plurality of line flanks G1 rising obliquely in the casting direction and a plurality of line flanks G2 falling obliquely in the opposite casting direction, or it can be formed solely from such line flanks. The rising and falling line flanks G1, G2 occur alternately. In particular, the boundary line G can be realized in a zigzag shape, at least in the inner zone Z, as shown by way of example in Figure 3.

[0040] An angle a between a rising line flank Gl and a falling line flank G2 can be, for example, between 40 ° and 140 °, preferably 70 ° and 110 °.

[0041] Further features characterizing the boundary line progression can be a variation height VH and a variation width VB of the boundary line G. The variation height VH is measured in the casting direction as the distance between the inlet and outlet soapy reversal points of the boundary line progression G. The variation width VB results from the distance between adjacent outlet soapy reversal points of the boundary line progression G.

[0042] Both the variation height VH and the variation width VB can vary over a wide range. In particular, they can each be within a range between 30 and 200 mm, preferably between 60 and 150 mm.

[0043] The variation height VH can be substantially equal to the variation width VB, but it is also possible that the variation height VH is greater or - as in the example shown in Figure 3 - smaller than the variation width VB.

[0044] The inner zone Z can, for example, be equal to or greater than 50% or 60% or 70% or 80% or 90% of the width B of the mold plate 105_l or correspond to the entire width ( 100%) of the mold plate 105_l.

[0045] Figures 4A to 4C show further possible boundary line courses G between the inlet-side region 101 and the outlet-side region 102 of the mold 100. All boundary line courses G can be periodic. The period length can be constant or vary along the boundary line course. The period length corresponds to the variation width VB explained in Figure 3 using a zigzag-shaped boundary line course G (which can also vary between different reversal points).

[0046] Figure 4A shows a wavy boundary line G. A boundary line G is also possible that has peaks at the exit-seam reversal points and is provided with curves at the entry-seam reversal points, see Figure 4B. It is also possible to realize the exit-seam reversal points with curves and to design the entry-seam reversal points as peaks. In general, the entry-seam and / or exit-seam reversal points can be designed, for example, with an obtuse angle, an acute angle, a curved angle, a pointed angle, or a flat curve.

[0047] Figure 4G shows a further example of a boundary line profile G, which is designed in the manner of a crenellation, the individual crenellations being trapezoidal or formed with inclined side wall sections. Figure 4C further illustrates by way of example that the boundary line G can also run in sections in the transverse direction of the mold 100. A boundary line profile G which has sections running in the transverse direction as well as inclined sections is possible for all of the boundary line profiles G shown here as examples. The reversal points of the boundary line profile G in Figure 4G are realized as the sections of the boundary line running in the transverse direction, i.e. for example not formed by reversal points (as shown, for example, in Figures 4A and 4B), but by straight reversal sections.

[0048] The exemplary boundary line courses G shown in Figures 4A to 4G can be combined with one another in any desired manner.

[0049] In the transition region of length VH in the casting direction, the support of the strand shell 122 by the coating builds up continuously from 0% (when the inlet-soapy region 101 is designed without a coating pattern, as shown in Figure 3) to 100%, at least in the inner zone. The transition region can also be described as a region that is partially coated, at least in the inner zone Z, and has uncoated free areas that taper in the casting direction.

[0050] Figure 5 shows a plan view of a mold plate 105_2 which differs from the mold plate 105_1 essentially in that the coating (non-hatched area) in the edge regions of the mold plate 105_2 extends up to the inlet-side edge of the mold plate 105_2. Since more favorable conditions for high heat dissipation exist in the edge regions of the mold plate 105_2 due to the additional mold plates present there (e.g. narrow-side mold plates), a coating can also be possible in the edge regions in the inlet-side region 101. As in Figure 3, however, this example also has an inner zone Z within which the boundary line G between the regions 101 and 102 is at least partially oblique to the transverse direction of the mold plate 105_2.

[0051] Figure 6 shows a further embodiment of a mold plate 105_3, which differs from the mold plate 105_2 of Figure 5 essentially in that the inlet-soapy region 101 is at least partially (completely in the example shown here) coated with a coating pattern.

[0052] The coating pattern has, for example, strip-shaped coating structures S. However, the coating structures S can also be curved or realized in another form.

[0053] The coating structures S can intersect. For example, an array-shaped coating pattern can be formed from island-shaped, uncoated fields F of the mold plate 105_3.

[0054] The coating pattern can be regular, as shown by way of example in Figure 6. In these and other cases, it can have a constant coating area proportion (or a constant proportion of uncoated area (e.g., given by fields F).

[0055] In the manner already described, here too, a boundary line G between the inlet-side soapy region 101 and the outlet-side full-surface coating (region 102) is at least partially inclined relative to the transverse direction of the mold plate 105_3. Edge lines of fields F can be oriented at an angle relative to the transverse direction of the mold plate 105_3. In particular, it is possible for all edge lines of fields F to be oriented at an angle relative to the transverse direction of the mold plate 105_3.

[0056] Edge lines of fields F can form, at least in sections, the boundary line between the inlet soapy area 101 and the outlet soapy area 102.

[0057] In the example shown in Figure 6, increased support of the metal strand 120 already occurs in the soapy inlet region 101 due to the coating structures present there. As in the previous examples, a transition region of length VH in the casting direction also occurs here, over which the support of the metal strand 120 continuously increases from a coating area proportion predetermined by the coating pattern to 100%.

[0058] The mold plates 105, 105_1, 105_2, 105_3, 106 can be made of a material with good heat dissipation, 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, made of a nickel-based alloy or a chromium-based alloy. In particular, the coating can be a NiCrBSi alloy. Alternatively, the coating can be formed, for example, from a carbide or a ceramic material. The coating is inserted into the mold plate 105, 105_l, 105_2, 105_3, 106 in such a way that the surface of the (uncoated) mold plate 105, 105_l, 105_2, 105_3, 106 and the surface of the coating border one another without any steps. The coating is generally harder than the soft plate material. For example, the coating can be a hard material coating or hard materials (e.g.B. carbides) may be included in the coating, which increase the wear resistance of the coating.

[0059] The dimensions KL and B of the mold plate 105, 105_l, 105_2, 105_3, and 106 can vary widely. For example, the length KL of the mold plate 105, 105_l, 105_2, 105_3, and 106 can be approximately 900 mm. The width B of the mold plate 105, 105_l, 105_2, 105_3, and 106 is highly variable and can, for example, range between 1750 and 2480 mm. Plate widths B of up to approximately 4000 mm are also possible.

[0060] By creating a transition region with a continuously increasing proportion of the coating surface, a sharp separation from soft to hard along a transverse boundary line can be avoided in the manner described. Instead, a transition region with less local wear is created along the varying boundary line G. Furthermore, the risk of tearing of the thin strand shell 122 may also be reduced, thereby increasing production reliability (lower risk of breakage of the strand shell 122 or strand skin).

[0061] Furthermore, a coating pattern with, for example, checkerboard-like (see Figure 6) or honeycomb-like uncoated fields F in the inlet-side region 101 of the mold 100 can achieve good heat dissipation with simultaneous good wear resistance. By slanting edge lines of fields F, the aforementioned advantages of slanting boundary line sections can also be achieved in the inlet-side region 101. All of the measures presented here as examples, particularly with regard to the boundary line profile G and the (optional) coating pattern, can be combined with one another.

[0062] Furthermore, the coating pattern, if present, does not have to cover the entire inlet-facing region 101. Rather, in the inlet-facing region 101, for example, an upper partial region beginning at the inlet-facing end of the mold plate can be uncoated, and the coating pattern (e.g., the strip-shaped coating structures S) can only be realized in a subsequent region in the casting direction. It is equally possible for a coating pattern to be present at the inlet-facing end of the mold plate, and for a completely uncoated plate region to exist between the coating pattern and the boundary line G, as in Figure 3.

Claims

Patent 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 with a full-surface, wear-resistant coating at least in an inner zone extending in the casting direction and has an inlet-surface area which is uncoated or at least partially coated with a coating pattern, and a boundary line between the inlet-surface area and the full-surface, soapy coating is at least partially inclined relative to a transverse direction of the mold oriented perpendicular to the casting direction,wherein the boundary line contains 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., 2. Mould according to claim 1, wherein an angle between a rising line flank and a falling line flank is between 40° and 140°, in particular 70° and 110°.

3. Mould according to claim 1 or 2, wherein the boundary line at least in sections contains a jagged, wavy, crenellated or otherwise varying boundary line course in the casting direction. 4 . Mould according to claim 3 , wherein a variation height of the boundary line course, measured in the casting direction as a distance between the inlet and outlet soapy reversal points of the boundary line, in a range between 30 and 200 mm, in particular 60 and 150 mm.

5. Mould according to claim 3 or 4, 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.

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

7. Mould according to claim 6, wherein strip-shaped coating structures intersect.

8. A mold according to any one of claims 6 or 7, wherein the coating pattern defines an array of island-shaped, uncoated fields of the mold plate.

9. Mould according to claim 8, wherein edge lines of fields are oriented obliquely with respect to the transverse direction of the mould.

10. 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. 11 . Mould according to one of the preceding claims, wherein the mould is limited by four mould plates, namely two opposing narrow side plates and two opposing wide side plates, wherein the mold plate is a wide side plate.

12. Mold according to one of the preceding claims, wherein the Mould intended for continuous casting of steel alloys.

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