Casting mold ring

Abstract

The invention relates to a casting mold ring (11) comprising a ring body (12) which has pores, the ring body (12) having, in an axial direction (15), a first section (14) and a second section (17) adjoining thereto, and the first section (14) being provided for distributing lubricant. A curable auxiliary agent is introduced into the pores of the second section (17), the auxiliary agent being cured at least in a zone (24) of the second section (17) which zone directly adjoins the first section (14).

Description

[0001] casting mold ring

[0002] The invention relates to a casting mold ring with a ring body having pores, wherein the ring body has a first section and a second section adjoining it along an axial direction, and the first section is provided for the distribution of a lubricant.

[0003] The invention further relates to a mold with a casting ring and a mold base body, wherein the casting ring is held by the mold base body.

[0004] Furthermore, the invention relates to a method for producing a casting mold ring from a ring body which has pores and which has a first section and a second section adjoining it along an axial direction, and the first section is provided for the distribution of a lubricant.

[0005] Continuous casting is a well-known process. In simple terms, a molten material, such as a metallic material, is passed through a die and solidified in the process. For further details of this process, please refer to the relevant prior art.

[0006] The mold can be made of a wide variety of materials. It is known in the art to use molds that are at least partially made of graphite. Graphite has the advantage of self-lubricating properties and relatively high thermal conductivity, both of which are beneficial for the transport and solidification of the molten metal or the solidified material. To improve the lubrication and / or the service life of the mold, it is also known to distribute lubricant through the pores of the graphite. For example, DE 558 177 A1 describes a graphite mold for casting metals that contains a glass or flux as a lubricant, which softens or melts below the solidification temperature of the molten metal.

[0007] In practice, however, other lubricants are also used, such as organic lubricants.

[0008] To protect the mold or to prevent roughening and / or improve the sliding properties of the mold's running surface, which comes into contact with the melt and the solidified melt, various mold designs are known from the prior art.

[0009] JP 2023 / 181315 A describes a continuous casting nozzle with an inner wall surface serving as a mold and an outer wall surface and a graphite base material forming a framework, wherein the graphite base material has pores and the interior of the pores is filled with glassy carbon particles.

[0010] From EP 0 811 446 B 1, a mold for the continuous casting of billets or ingots is known, containing homogeneously distributed, primarily solidified solid particles consisting of individual degenerate dendrites. The mold has a modular design, wherein the first mold element has an inlet opening for introducing the continuous casting material, and at least the inner wall of the first mold element has a low thermal conductivity compared to the continuous casting material; the second mold element has means for introducing lubricant into the mold cavity; the third mold element defines the shaping mold area, and at least its inner wall has a thermal conductivity comparable to that of the continuous casting material. The second mold element has an annular body made of highly porous, temperature-resistant material, the porosity being such that lubricant can diffuse through the porous material.

[0011] EP 0 337 769 B 1 describes a continuous or semi-continuous casting device for casting metallic materials, comprising a mold with an inlet for molten metal and a mold cavity with a discharge means for a water supply exiting through the discharge and intended for cooling the metal, wherein the mold cavity is provided at a distance from its inlet with a permeable ring of graphite for the supply of oil and / or gas, so that an oil and / or gas layer is formed between the metal and the mold wall, which has the effect that the metal cannot come into contact with the mold wall before it solidifies, wherein, with the exception of the side opposite the mold cavity, the surface of the ring is provided with a sealing agent that prevents the escape of the oil and / or gas through the surface.and the ring is equipped in its peripheral direction with longitudinal channels or holes for the supply of O1 and / or gas to said ring through channels extending from the outside of the mold through the mold wall and further into the ring. Further continuous casting devices or molds for this purpose are known from CN 109702156 B, EP 0 530056 Al, EP 1 808 240 Bl and CN 104096810 A.

[0012] The present invention is based on the objective of improving the sliding properties of a mold.

[0013] To solve the problem of the invention, the casting mold ring mentioned at the outset is provided in such a way that a curable auxiliary material is introduced into the pores of the second section, wherein the auxiliary material is cured at least in a zone of the second section immediately adjoining the first section.

[0014] Furthermore, the object of the invention is solved with the aforementioned mold, which has the casting mold ring according to the invention.

[0015] Furthermore, the object of the invention is solved by the aforementioned method, according to which a curable auxiliary material is introduced into the pores of the second section, and the auxiliary material is cured at least in a zone of the second section immediately adjoining the first section.

[0016] An advantage of this method is that it prevents changes in lubricant penetration. Organic lubricants tend to polymerize at elevated temperatures. This leads to a clogging of the pores in the graphite and a consequent negative impact on lubricant penetration. Due to the blockage of the pores in the affected areas, the lubricant flow is diverted to areas of lower resistance. This shifts the lubricant cushion out of the working area, and the lubrication for continuous casting collapses. If this occurs, the casting process must be stopped, and the graphite ring requires maintenance. The invention manipulates the available porosity, also known as permeability, before the casting process begins, preventing the lubricant flow from diverting. This is achieved by introducing the additive into the unused sections of the mold ring.By curing the additive at least immediately adjacent to the first section, the size of the first section can be more precisely defined by a clear demarcation from the second section. According to one embodiment of the invention, the ring body can have a third section with pores, wherein the first section is arranged axially between the second and third sections, and a curable additive is introduced into the pores of the third section, curing at least in a zone of the third section immediately adjacent to the first section. This achieves a separation of the first zone from the two end faces of the mold ring or the die, thus protecting the lubricant in the pores of the first section from excessive heat exposure.

[0017] According to a preferred embodiment of the invention, the excipient can comprise water glass or a curable synthetic resin. This simplifies the production of the curable zone, as the excipient can be cured with a gaseous curing agent. Carbon dioxide is particularly suitable for curing water glass. An amine can be used for curing the synthetic resin.

[0018] According to a further preferred embodiment of the invention, the ring body is formed from graphite. This achieves, on the one hand, the aforementioned advantages of using graphite in molds. On the other hand, it also has the advantage that, according to a further embodiment of the invention, the carbon dioxide for hardening the water glass can be generated in situ from the graphite. According to one embodiment of the invention, this can be done by heating the first section, whereby, according to another embodiment, the heating of the first section can be carried out inductively, with a laser beam, or with a burner. By generating the carbon dioxide in the first section, this section is more precisely defined, since the water glass is formed upon reaching the boundary between the first and second sections.The first and third sections harden, thus preventing further penetration of the unhardened water glass into the first section. The use of a laser beam, an induction coil, or a burner has the advantage that the mold ring can be heated more easily and locally, which also simplifies defining the size of the first section for lubricant incorporation. According to another embodiment of the invention, however, the carbon dioxide can also be introduced separately into the pores of the first section, for example, by means of a carbon dioxide pressure pulse.

[0019] The curing of the auxiliary material, at least in the zone of the third section immediately adjoining the first section, is preferably carried out according to the invention.

[0020] To improve the aforementioned effects, according to the design variant, it may be provided that the pores in the second section are filled with the additive to at least 1% of the volume fraction of the open porosity and / or that the pores in the third section are filled with the additive to at least 4% of the volume fraction of the open porosity.

[0021] According to a further embodiment of the invention, it can be provided that the water glass is produced simultaneously with or after the production of the carbon dioxide from the ring body by heating the first section, which allows the formation of the first section to be better "controlled".

[0022] According to one embodiment of the invention, the auxiliary material is preferably introduced under overpressure or underpressure, as this allows the pores in the second or third section to be populated more quickly.

[0023] According to a further embodiment of the invention, the curing of the auxiliary material, in particular water glass, can be carried out using microwaves. Curing by microwaves has the advantage that it reduces the need for post-processing of the ring body.

[0024] To better understand the invention, it is explained in more detail with reference to the following figures.

[0025] They each show, in simplified, schematic form:

[0026] Fig. 1 a continuous casting plant;

[0027] Fig. 2 shows a mold with a casting ring in side view;

[0028] Fig. 3 shows a section of a casting mold ring with incorporated hardening agent; Fig. 4 shows a section of the casting mold ring according to Fig. 3 with incorporated hardening agent and incorporated auxiliary agent;

[0029] Fig. 5 shows a variant of the in situ production of the hardening agent;

[0030] Fig. 6 shows a variant of the in situ production of the hardening agent;

[0031] Fig. 7 shows a variant of the in situ production of the hardening agent;

[0032] Fig. 8 shows the graphical representation of the displacement of the lubricant pad over the

[0033] Time.

[0034] It should be noted at the outset that in the differently described embodiments, identical parts are provided with the same reference numerals or component designations, and the disclosures contained in the entire description can be applied analogously to identical parts with the same reference numerals or component designations. Furthermore, the positional designations chosen in the description, such as top, bottom, side, etc., refer to the figure directly described and illustrated, and these positional designations must be applied analogously to the new position if the position changes.

[0035] Figure 1 shows a highly simplified representation of a continuous casting plant 1, particularly a continuous casting plant. Specifically, a horizontal continuous casting plant 1 is shown. However, the invention can also be used in vertical continuous casting plants 1.

[0036] The continuous casting plant 1 comprises a pouring crucible 2 (tundish), a mold 3, and a vent 4. For further details of such continuous casting plants 1, reference is made to the prior art. The molten metal, in particular the liquid metal, is transferred from the pouring crucible 2 into the mold 3, where it is formed into a continuous casting product 5. In the mold 3, the molten metal solidifies at least in an outer shell, so that the continuous casting product 5 can be withdrawn. A core of the continuous casting product 5 may still be molten or viscous after leaving the mold 3.

[0037] Figure 2 shows a section through the mold 3. The mold 3 is a so-called open mold 3, meaning it has no bottom. The molten metal enters the mold 3 through an inlet opening 6, and the molten metal, at least partially solidified to form the continuous casting product 5, exits the mold 3 through an outlet opening. The size of the inlet opening 6 can be varied, if necessary, by means of a cross-sectional reduction element 8. This also allows the flow behavior of the molten metal to be influenced.

[0038] The mold 3 has a mold base 9. The mold base 9 can also be referred to as a cooling element, since a cooling system 10 is arranged or formed within it. The cooling system 10 serves, on the one hand, to cool the mold 3 itself. On the other hand, a cooling medium can be applied via the cooling system 10 to the continuously cast product 5 exiting the mold 3 for its further cooling, as indicated in Fig. 2.

[0039] The mold base 9 also serves to hold a casting ring 11. The casting ring 11, or a ring body 12 of the casting ring 11, is in direct contact with the melt, so that the shape of the continuously cast product 5 is defined by the casting ring 11 or the ring body 12. For this purpose, a ring body 12 of the casting ring 11 has the cross-sectional shape required for the shape of the continuously cast product 5. The ring body 12 can, for example, have a circular, oval, rectangular, or generally polygonal cross-section. However, this list is not intended to be limiting to the invention. The casting ring 11 can encompass or consist of the ring body 12.

[0040] The casting mold ring 11 or the ring body 12 preferably comprises or is formed from graphite. However, the casting mold ring 11 or the ring body 12 can also consist of or comprise another material, for example a ceramic material such as Al₂O₃.

[0041] The ring body 12 has a porosity for receiving a lubricant (also referred to as a release agent), in particular an organic lubricant. This is indicated in Figures 3 and 4 for a section of the ring body 12. The porosity is formed at least in the area of ​​a contact surface 13 with the melt or the partially solidified melt. However, the entire ring body 12 can also be porous. The pores can have a size of less than 0.1 mm, for example, between 0.001 mm and less than 0.01 mm. The ring body 12 can have a permeability of between 1.4 x 10⁻⁶, either partially or entirely. 14 m 2and 1.8 x 10 14 m 2 exhibit.

[0042] The permeability is measured analogously to the setup described in Hao Eiu and Ying Xu, "Gas permeability measurement in porous graphite under steady-state flow," Materials Research Express, Volume 9, Number 2 (available at htips: / / opsdence.iop.ofg / archive / l0.1088 / 2053-159l / ac50d7 / meta). Essentially, the Darcy coefficients are determined. The measurement method is based on determining the dependence of the pressure drop on the flow rate. This is described by the Darcy-Forchheimer law extended to include compressibility, as explained in the cited publication. Dried air is used as the working medium. The pressure is selected between 3 bar and 8 bar. The operating temperature is 21 °C. Cooling due to expansion is not considered at the low mass flow rates of less than 40 l / h. The flow rate at three different pressures, the permeability, and the momentum coefficients (the Fitting coefficients) are determined.The result is averaged over 6x5x5 measuring points for three pressures.

[0043] The lubricant is to be contained only in a first section 14 of the ring body 12, or supplied to the contact surface 13, i.e., to emerge onto the contact surface 13 during operation. The first section 14 can have a length in an axial direction 15 through the mold 3 that is between 5% and 50% of the total length 16 of the mold 3 in the axial direction 15. For example, the first section can have a length in the axial direction 15 between 20 mm and 40 mm. The ring body 12 thus has at least one second section 17. The second section 17 adjoins the first section 14 directly in the axial direction 15.

[0044] The second section 17 extends in the axial direction 15 from a first axial end face 18 of the ring body 12 in the area of ​​the exit opening 7 of the mold 3 to the first section 14.

[0045] In the embodiment shown in Figures 3 and 4, the ring body 12 has a third section 19. The third section 19 extends from a second axial end face 20 of the ring body 12 in the region of the inlet opening 6 of the mold 3 to the first section 14. Thus, the first section 14 is arranged or formed in the axial direction 15 between the first and the third sections 17, 19. The third section 19 can have a length in the axial direction 15 that is between greater than 0% and up to and including 5% of the total length 16 of the mold 3 in the axial direction 15.

[0046] It is provided that a curable additive is introduced into the pores of the second section 17 and the optional third section 19. In Fig. 4, this is represented by triangles, while the open pores of the first section 14 are represented by circles. The additive can only be introduced into the region of the ring body 12 adjoining the contact surface 13. Preferably, however, the infiltration of the ring body 12 with the curable additive is carried out in such a way that the entire ring body 12 in the second and optionally third sections 17, 19 is filled with the additive.

[0047] The curable additive differs from the lubricant in the first section 14 of the ring body 12. The purpose of arranging or embedding the additive in the pores of the second and, optionally, third sections 17, 19 is to prevent the lubricant from migrating into these sections. Reference is made to Fig. 8, which was created during the evaluation of the present invention using a graphite ring as the casting mold ring 11. The x-axis represents the total length 16 of the ring body 12 in mm, and the y-axis represents the velocity of the lubricant supply to the contact surface 13 in m / s. The upper third of the illustration shows a section of the ring body 12 corresponding to Figs. 3 and 4, with the first, second, and third sections 14, 17, 19.

[0048] The displacement of the lubricant cushion from the working area, i.e., the first section 14, into the second section 17 over time can be seen from the three trajectories 21-23 of the lubricant supply. As a consequence, the lubrication of the mold ring 11 and thus of the mold 3 collapses.

[0049] To prevent this, it is provided that the auxiliary material is cured at least in a zone 24 of the second section 17 and, if applicable, of the third section 19, which is immediately adjacent to the first section 14.

[0050] In Fig. 4, this zone 24 extends through the entire thickness 25 of the ring body 12, measured perpendicular to the total length 13. As Figs. 6 and 7 show, the zone 24 can also extend only over a portion of the total thickness 25. In this case, the zone 24 can also be dome-shaped, with the zones 24 of the second and third sections 17, 19 being "fused" into a common zone 24.

[0051] The auxiliary material is preferably water glass, in particular sodium, potassium, or ethium water glass. However, another auxiliary material may also be used, provided that it achieves the described effect of preventing the displacement of the lubricant pad in the axial direction 15 and that this auxiliary material is usable at the respective operating temperature of the mold 3. For example, in addition to water glass, a curable synthetic resin, in particular a polyurethane resin, a furan resin, or a phenolic resin, may also be used as an auxiliary material.

[0052] The excipient preferably consists entirely of water glass or a synthetic resin. However, it may also contain additives that improve the processing of the excipient, such as its infiltrability.

[0053] The hardening of water glass can be carried out with carbon dioxide. The hardening of PUR can be carried out, for example, with an amine. During hardening, cross-linking of molecular chains occurs. Hardening preferably takes place in the aforementioned zone 24 directly upon contact of the filler with the hardening agent. For this purpose, the hardening agent can be introduced into the pores of the first section 14 beforehand. The hardening agent is preferably gaseous, or a gas is used as the hardening agent.

[0054] For the curing of a furan resin, for example polyethylene polyamine in combination with furfuryl alcohol can be used, for the curing of a phenolic resin, for example trimethylamine, and for the curing of a PUR, for example methylamine.

[0055] In the embodiment shown in Fig. 3, the curing agent is introduced into the pores of the first section 14 by means of a gas pulse. The gas can be introduced via pulses lasting several milliseconds. In the case of water glass, carbon dioxide is introduced into these pores. The carbon dioxide can be incorporated over a period of time sufficient to fill the pores across their entire thickness 25. After the carbon dioxide has been incorporated, the water glass is infiltrated into the pores of the second and, if applicable, third section 17, 19. When the water glass comes into contact with the carbon dioxide, it cures, particularly immediately, and zone 24 is formed, as shown in Fig. 4. After the carbon dioxide has been incorporated across the entire thickness 25 of the ring body 12 in this embodiment, the following are shown in Fig.In the variant shown in section 4, the second and third sections 17, 19 are completely separated from each other.

[0056] Within the scope of the invention, it is possible for the auxiliary material to be cured only in zone 24. In this case, zone 24 can preferably have a zone thickness 26 between 2 mm and 3 mm. However, the auxiliary material contained in the pores of the ring body 12 can also be completely cured. If only zone 24 is formed, the uncured portion of the auxiliary material can remain in the ring body 12 or be removed from it.

[0057] According to various embodiments, the pores in the second section 17 can be filled with the additive to at least 1%, preferably between 20% and 100%, of the volume fraction of the open porosity, and / or the pores in the third section 19 can be filled with the additive to at least 4%, preferably between 20% and 100%, of the volume fraction of the open porosity. Thus, the pores can be completely or only partially closed with the additive, with partial closure resulting in a greater extent than the aforementioned lower limit achieving the desired effect of preventing displacement of the lubricant pad. Therefore, it is not necessary for the pores to be completely filled with the additive. Closing the channels may be sufficient to achieve the effect of the invention.

[0058] It is also possible that - apart from zone 24 - pores of the second and, if applicable, third section 17, 19 in the area of ​​the contact surface 13 are sealed with the hardened auxiliary material, or that, alternatively, pores up to a greater layer thickness of the ring body 12, which is less than the total thickness 25 of the ring body 12, are sealed with the hardened auxiliary material.

[0059] In the embodiment shown in Figures 3 and 4, the curing agent is separately pre-embedded in the pores of the ring body 12. According to other embodiments, however, the curing agent can also be produced in situ from the material of the ring body 12 itself. This embodiment can be used particularly in combination with a graphite ring body 12 and carbon dioxide as the curing agent. For this purpose, the ring body 12 can be heated to a suitable temperature. For graphite, this temperature for the in situ formation of carbon dioxide is approximately 600 °C. Preferably, only the first section 14 is heated, so that, as in the embodiment with the gas pulse, a gas cushion is formed in the pores of the first section, which in turn causes the formation of zone 24 upon contact with the auxiliary material / water glass, as described above.

[0060] Figures 5 to 7 illustrate various embodiments for the in-situ formation of carbon dioxide from graphite using sections of the ring body 12. Heating, for example, of only the first section 14, can be carried out inductively using a coil 29 (Fig. 5), a laser beam 27 (Fig. 6), or a burner 28 (Fig. 7). The laser beam 27 allows for greater design flexibility in the carbon dioxide distribution. Furthermore, a narrowly defined porosity range can be achieved.

[0061] Particularly in the variants with in-situ formation of the curing agent, the excipient can be introduced simultaneously with this formation. However, it is also possible (in these variants) for the excipient to be introduced into the pores of the second and, if applicable, third section 17, 19 only after the curing agent has been incorporated / formed. The infiltration of the excipient can be carried out under positive or negative pressure (vacuum). For example, the infiltration of the excipient can be carried out with a pressure differential of 200 mbar or higher.

[0062] Microwave energy can also be used to harden the additive, especially water glass. For this purpose, the ring body 12 is impregnated with the additive and at least the impregnated areas or section 17 or sections 17 and 19 are exposed to microwave energy. Alternatively, the entire ring body 12 can be exposed to microwave energy, for example by treating it in a suitable microwave device.

[0063] The examples shown illustrate or describe possible design variants, and it should be noted that combinations of the individual design variants are also possible.

[0064] For the sake of clarity, it should be noted that, for a better understanding of the construction of the continuous casting plant 1 and the mold 3, these are not necessarily shown to scale. Reference numerals

[0065] Continuous casting plant

[0066] Pouring crucible

[0067] mold

[0068] Deduction

[0069] Continuous casting product

[0070] Entrance opening

[0071] Exit opening

[0072] Cross-sectional tapering element

[0073] Mold body

[0074] Cooling system

[0075] Casting mold ring

[0076] Ring body

[0077] Contact surface

[0078] Section

[0079] Axial direction

[0080] Total length

[0081] Section

[0082] Front surface

[0083] Section

[0084] Front surface

[0085] Course

[0086] Course

[0087] Course

[0088] Zone

[0089] thickness

[0090] Zone thickness

[0091] laser beam

[0092] burner

[0093] Sink

Claims

Patent claims 1. Casting mold ring (11) with a ring body (12) having pores, wherein the ring body (12) has a first section (14) and a second section (17) adjoining it along an axial direction (15), and the first section (14) is provided for the distribution of a lubricant, characterized in that a curable auxiliary material is introduced into the pores of the second section (17), wherein the auxiliary material is cured at least in a zone (24) of the second section (17) immediately adjoining the first section (14).

2. Casting mold ring (11) according to claim 1, characterized in that the ring body (12) has a third section (19) with pores, wherein the first section (14) is arranged between the second and the third section (17, 19) when viewed in the axial direction (15), and a curable auxiliary material is introduced into the pores of the third section (19), wherein the auxiliary material is cured at least in a zone (24) of the third section (19) immediately adjoining the first section (14).

3. Casting mold ring (11) according to claim 1 or 2, characterized in that the auxiliary material comprises a water glass or a curable synthetic resin.

4. Casting mold ring (11) according to one of claims 1 to 3, characterized in that the ring body (12) is made of graphite.

5. Casting mold ring (11) according to one of claims 1 to 4, characterized in that the pores in the second section (17) are filled with the auxiliary material to at least 1% of the volume fraction of the open porosity.

6. Casting mold ring (11) according to one of claims 2 to 5, characterized in that the pores in the third section (19) are filled with the auxiliary material to at least 4% of the volume fraction of the open porosity.

7. Casting mold ring (11) according to one of claims 4 to 6, characterized in that a hardening agent for hardening the auxiliary material in situ is produced from the graphite.

8. Mold (3) with a mold ring (11) and a mold base body (9), wherein the mold ring (11) is held by the mold base body (9), characterized in that the mold ring (11) is formed according to one of claims 1 to 7.

9. Method for producing a casting mold ring (11) from a ring body (12) having pores and having a first section (14) and a second section (17) adjoining it along an axial direction (15), and the first section (14) being provided for the distribution of a lubricant, characterized in that a curable auxiliary material is introduced into the pores of the second section (17), and the auxiliary material is cured at least in a zone (24) of the second section (17) immediately adjoining the first section.

10. Method according to claim 9, characterized in that the auxiliary material comprises or is water glass, and that the hardening of the water glass is carried out with carbon dioxide.

11. Method according to claim 10, characterized in that the carbon dioxide is introduced into the pores of the first section (14) before the water glass is introduced.

12. Method according to claim 10, characterized in that the ring body (12) is formed from graphite, and that the carbon dioxide is formed from the ring body (12).

13. Method according to claim 12, characterized in that the carbon dioxide is produced from the ring body (12) by heating the first section (14).

14. Method according to claim 13, characterized in that the heating of the first section (14) is carried out inductively or with a laser beam or with a burner.

15. Method according to claim 13 or 14, characterized in that the water glass is produced simultaneously with or after the production of the carbon dioxide from the ring body (12) by heating the first section (14).

16. Method according to claim 9, characterized in that the auxiliary material comprises or is a curable synthetic resin, and that the curing of the synthetic resin is carried out with an A-min.

17. Method according to one of claims 9 to 16, characterized in that a third section (19) with pores is formed on the ring body (12), wherein the first section (14) is arranged between the second and the third section (17, 19) when viewed in the axial direction (15), and a curable auxiliary material is introduced into the pores of the third section (19), wherein the auxiliary material is cured at least in a zone (24) of the third section (19) immediately adjoining the first section (14).

18. Method according to claim 17, characterized in that the curing of the auxiliary material is carried out at least in the zone (24) of the third section (19) immediately adjoining the first section (14) in accordance with one of claims 10 to 16.

19. Method according to one of claims 9 to 18, characterized in that the auxiliary material is introduced into the pores under overpressure or underpressure.

20. Method according to one of claims 9 to 19, characterized in that the curing of the auxiliary material is carried out using microwaves.

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