EP4603209A1

EP4603209A1 - Repair system and method for repairing a casting channel

Info

Publication number: EP4603209A1
Application number: EP24157793.1A
Authority: EP
Inventors: Rief Andreas; Birgit Bellgardt-Dolc; Jürgen PERNOT; Stefan Pischek; Beat HEINRICH; Kurt Ackermann
Original assignee: Refractory Intellectual Property GmbH and Co KG
Current assignee: Refractory Intellectual Property GmbH and Co KG
Priority date: 2024-02-15
Filing date: 2024-02-15
Publication date: 2025-08-20
Also published as: WO2025172350A1; TW202545657A

Abstract

To provide an easier solution for the repair of worn-out casting channels (2) a repair tube (1), comprising a tube wall (10) having an inner surface (I) with an inner diameter (i1) defining an inner space (S) and having an outer surface (O) with an outer diameter (o1) is provided. The tube wall (10) has a plurality of openings (101) connecting the inner surface (I) to the outer surface (O) and is longitudinally inserted into the casting channel (2), such that after insertion a cavity (C) in between the outer surface (O) and the casting channel (2) is formed. A repair mix (3) is pressed from the inner space (S) of the repair tube (1) through said plurality of openings (101) to fill said cavity (C) by using a pressing tool (4).

Description

The current disclosure relates to a method for repairing a casting channel of a refractory part of a metallurgical vessel and to a repair system for repairing a casting channel of a refractory part of a metallurgical vessel and use of said repair system.
A metallurgical vessel is used for containing and/or treating liquid metal. A metallurgical vessel has an outer shell, e.g., made of steel, and an inner lining, e.g., made of refractory material. The inner lining is at least partially in contact with the liquid metal or slag and thus experiences wear over time. The metallurgical vessel may further comprise refractory parts having casting channels for casting, i.e., draining the contained liquid metal and/or slag. Various types of refractory parts having casting channels are known, e.g., tapholes, nozzles etc. Wear of the casting channels can lead to non-uniformity and increased casting channel diameter. The former leads to unstable flow pattern whereas the latter increases the risk of steel infiltrations. Due to the flow of metal or slag through a casting channel leading to mechanical stress, wear of said casting channel usually exceeds wear of the lining of the metallurgical vessel. Thus, casting channels might be worn out while the lining of the metallurgical vessel might still be in proper condition. Therefore, in case of a steel casting ladle, the refractory part comprising the casting channel usually has to be replaced about every 10 to 20 heats while the lining is only replaced about every 60 or more heats.
When worn out, the casting channel may also be repaired to minimize or even eliminate the number of required refractory replacements during a vessel's lining life. This is particularly beneficial when replacement of the refractory part comprising the casting channel is demanding, labor intensive, dangerous and/or time consuming, which is the case, e.g., for an inner nozzle of a slide gate.
Repairing a casting channel using mortar is generally a known procedure and can be done by directly applying said mortar. KR 2003/0014936 A discloses spraying mortar through holes from a tube inserted into a casting channel.
EP 3 259 085 B1 shows application of repair mix by usage of centrifugal force by rotation of a tube. In any case the tube is removed from the nozzle after the repair has been finished.
However, known repair methods usually lead to unsatisfactory results. Applying the mortar in the intended amount to the desired position within the casting channel and ensuring it stays there is one of the main challenges to be overcome.
It is an object of the current disclosure to provide an easier solution for the repair of worn-out casting channels.
This object has been achieved by a method for repairing a casting channel of a refractory part of a metallurgical vessel, wherein a repair tube comprising a tube wall having an inner surface with an, preferably constant, inner diameter defining an inner space and having an outer surface with an, preferably constant, outer diameter, the tube wall having a plurality of openings connecting the inner surface to the outer surface, is longitudinally inserted into the casting channel, such that after insertion a cavity in between the outer surface and the casting channel is formed. A repair mix, e.g., mortar, is pressed from the inner space of the repair tube through said plurality of openings to fill said cavity by using a pressing tool.
The object has further been achieved by a repair system for repairing a casting channel of a refractory part of a metallurgical vessel, wherein the repair system comprises a repair tube, the repair tube comprising a tube wall having an inner surface with an, preferably constant, inner diameter defining an inner space and an outer surface with an, preferably constant, outer diameter, wherein the tube wall comprises a plurality of openings connecting the inner surface to the outer surface. The repair tube is longitudinally insertable into the casting channel such that after insertion, a cavity is at least partially formed in between the outer surface of the repair tube and the casting channel. The repair system further comprises a pressing tool, configured to press a repair mix from the inner space of the repair tube through said plurality of openings to fill said cavity.
The repair system can be used by inserting the repair tube longitudinally into a casting channel, such that after insertion a cavity in between the outer surface of the repair tube and the casting channel is formed, wherein a repair mix, e.g., mortar, is pressed from the inside of the repair tube through said plurality of openings to fill said cavity.
By using the method and system as disclosed herein precise, robust and fast repair or reconstruction of a casting channel is achieved while exchange of the refractory part comprising the casting channel is not necessary. This leads to higher availability due to elimination of downtime of the metallurgical vessel. Also, operational safety for operators is increased and heavy/exhausting work is eliminated. The repair mix can be applied more easily compared to State-of-the-Art techniques.
A casting channel has a nominal (transverse) channel diameter, preferably being constant. After experiencing wear, the channel diameter of the casting channel is (at least partially) extended and thus (at least partially) larger than the nominal channel diameter. Said extended channel diameter may vary along the longitudinal axis and in certain regions may still be equal to the nominal channel diameter.
The repair tube disclosed herein is a hollow cylinder having a wall, preferably with a circular base. The base might also be oval etc. The wall of the repair tube has a thickness, which may be in the range of 0.1 mm to 20 mm and preferably is constant for the whole of the repair tube. If the material of the repair tube comprises metal, in particular if the repair tube is supposed to be left inside the casting channel of the refractory part, a wall thickness of 0.1 mm to 5 mm might be beneficial. If the material comprises refractory material a wall thickness of 5 mm to 20 mm might be beneficial.
The repair tube has a first and a second longitudinal end, which preferably are open. A repair tube having a tube wall with at least partially smaller outer diameter than the casting channel diameter is longitudinally inserted into the casting channel. The outer diameter of the repair tube is equal to or smaller than the casting channel diameter, wherein it is preferable if the outer diameter is smaller than the casting channel diameter.
The pressing tool may comprise a displaceable piston. The repair mix can be pressed through said plurality of openings by displacing a piston via the pressing tool, e.g., by pushing or pulling said piston through the repair tube.
Preferably the piston has a diameter fitting to the inner diameter of the repair tube.
The repair mix can be pressed through said plurality of openings by displacing the piston via the pressing tool, whereas the piston is at least partially displaced within the inner space of the repair tube. Preferably, the repair mix can be pressed through said plurality of openings by pulling or pushing the piston longitudinally through the repair tube. The piston might comprise a head for displacing the repair mix and/or a shaft for actuating the head.
It is advantageous if the piston is placed at the repair tube before the repair tube is inserted into the casting channel.
Preferably the pressing tool comprises a base, e.g. a collar, for positioning the pressing tool at the casting channel. The collar might comprise a recess for placement of the piston. If the piston comprises a head and a shaft, the base might comprise a sliding opening for sliding the shaft.
If a base comprising a siding opening is present and the piston comprises a head and a shaft, the shaft is slid through the sliding opening of the collar, which in turn pushes the head through the repair tube and thus displaces the repair mix through the openings. If the base comprises a recess the head can be placed within a recess before the shaft is slid through the sliding opening.
The pressing tool can comprise mechanical and/or hydraulic components. The pressing tool might comprise hydropneumatics components, e.g., an expandable membrane. The repair mix might also be pressed through said plurality of openings by a gas, e.g., compressed air. Also, an Archimedean screw might be used for displacing the repair mix.
If a piston is displaced to press the repair mix through the plurality of openings, the head of the piston can be detachable from the shaft such that it is lost after serving its purpose.
The repair tube serves as an armoring structure during the repair process to keep the repair mix at the intended position within the casting channel and to prevent the repair mix from losing its shape during setting.
After the repair mix is pressed into said cavity in between the outer surface of the repair tube and the casting channel, it is possible that the repair tube can be removed from the casting channel of the refractory part, which is then preferably done before the repair mix is completely hardened. In this case the repair mix forms the new casting channel and thus it is beneficial if the outer diameter of the repair tube is equal to the nominal diameter of the casting channel.
It is preferred that after the repair mix is pressed into said cavity, the repair tube can be left inside the casting channel of the refractory part. The repair tube then remains in the former casting channel and thus is used as "lost part" and serves as a template for the new casting channel being held in position by the repair mix filling the cavity between the former casting channel and the outer surface of the repair tube. In this case the inner surface of the repair tube is used as a new casting channel and thus it is beneficial if the inner diameter of the repair tube is equal to the nominal diameter of the casting channel. Leaving the repair tube inside the casting channel of the refractory part leads to higher robustness and durability as the repair tube is more stable than solely repair mix. Also, a pull-out or an inadequate displacement of repair mix is at least partially prevented which might otherwise happen if the repair tube is removed. If it is intended to leave the repair tube inside the worn-out casting channel, it is preferably done when the repair tube has open longitudinal ends. The repair tube might be longer than the casting channel to be repaired and thus might protrude from the casting channel after the repair process. If the repair tube remains inside the worn casting channel and thus represents the new casting channel, any protruding part might be removed, e.g., broken off.
Preferably the (inner space of the) repair tube can, at least partially, be filled with the repair mix prior to its introduction into the (worn-out) casting channel. This allows a safe preparation and filling of the repair tube e.g. in a safe area away from any metallurgical vessel or heat. Alternatively, the inside of the repair tube can also be supplied with repair mix after its introduction into the casting channel. Also, a container containing repair mix can be provided, e.g., at the pressing tool.
Preferably, all of the repair mix is supplied to the inner space of the repair tube prior to the step where the repair mix is pressed from the inner space of the repair tube through said plurality of openings to fill said cavity by using a pressing tool. Preferably, no more repair mix is supplied to the inner space of the repair tube during the step where the repair mix is pressed from the inner space of the repair tube through said plurality of openings to fill said cavity by using a pressing tool. This has the advantage, that the amount of repair mix to be used can be easily and reproducibly be detected and maintained.
The repair tube can comprise a mesh, wherein the plurality of openings is formed by said mesh. The mesh might comprise wire and/or ceramic material. The former is more robust, the latter is cheaper and uses less material.
The repair tube may comprise metal, preferably steel and/or refractory material and/or cardboard. The repair tube may comprise fiber material, wood, plastic, coal, glass fiber etc.
The repair tube can have a length of 100 mm to 2500 mm, preferably 200 to 700 mm. For the casting channel of a ladle repair tubes with a length of about 200 to 700 mm might be used. For the casting channel of an electric arc furnace repair tubes with a length of about 2500mm and a diameter of about 100 mm to 200 mm might be used.
Preferably the shortest distance between two opposite parallel lines tangent to the circumference (in the sense of an enclosing boundary of a an opening out of the plurality of openings) of each opening out of the plurality of openings, such as a diameter in case of circular opening, such as a (smaller) side length in case of a square or of a rectangle, is 0.5 to 15 mm, preferably, 2 mm to 10 mm, most preferably 3 mm to 5 mm. The diameters can be chosen according to the wall thickness and/or the consistency of the repair mix.
The plurality of openings might have one or more of the following shapes: circular, squared, rectangular, oval. The plurality of openings might also have the shape of a, preferably transversal, slit or long hole.
Preferably the plurality of openings each have an open area of 3 to 113 mm², preferably 10 to 16 mm². The open area can be chosen according to the wall thickness and/or the consistency of the repair mix.
Preferably the plurality of openings comprise at least 9, preferably at least 18, preferably at least 27 openings.
Preferably the total area of all openings relative to the area of the outer surface (area of the material on the outer surface without openings) is in the range of 1 to 50%.
When the plurality of openings is formed by a mesh, the total area of all openings relative to the area of the outer surface (area of the material on the outer surface without openings) might be in the range of 50 to 95%.
The repair mix is preferably prepared with a penetration depth determined according to ISO 13765-1:2004(E), at an ambient temperature of 25°C and a temperature of the mix of 25°C, in the range of 15 mm to 40 mm, preferably 20 mm to 35 mm. This range of the penetration depth relates to a consistency range which has proven to be highly reliable in various application scenarios and environments, due to at least two effects: (i) the consistency is such, that spill out from the inner space before the pressing step is hugely reduced, and (ii) pressing the repair mix from the inner space is possible with a reduced force.
The repair mix is preferably a refractory repair mix. The repair mix preferably comprises refractory material, such as e.g. refractory mortar, refractory castable. The repair mix might comprise alumina, especially tabular alumina as the main component, e.g. more than 85 weight % of the repair mix might consist of tabular alumina. The repair mix might further comprise a chemical binder, such as a phosphate-based binder or a binder based on sodium silicate (waterglass). The repair mix preferable comprises 1 to 10 weight % of chemical binder, more preferably 3 to 8 weight % of chemical binder. The repair mix may further comprise metal oxides, such as SiO₂.
The outer diameter of the repair tube may be 30 mm to 110 mm and/or the inner diameter of the repair tube may be 25 mm to 105 mm.
Figs. 1 to 6b show exemplary, schematic, and non-limiting advantageous embodiments of the invention, wherein

Fig. 1 shows a cross-section of a section of a metallurgical vessel wall including a refractory part having a casting channel,
Fig. 2a shows a cross-section of the refractory part having a casting channel in unworn state, i.e. before experiencing wear,
Fig. 2b shows a cross-section of the refractory part having a casting channel after experiencing wear,
Fig. 3 shows a repair system comprising a repair tube having a plurality of openings and further comprising a pressing tool,
Fig. 4a and 5a show cross-sectional views of a repair tube being inserted into the casting channel of the refractory part,
Fig. 4b and 5b show cross-sectional views of repair mix being pressed through the plurality of openings of the repair tube by use of the pressing tool,
Fig. 6a shows a cross-section of the repaired casting channel of the refractory part after removal of the repair tube,
Fig. 6b shows a cross-section of the repaired casting channel without removal of the repair tube.

Fig. 1 shows a cross-section of a section of a wall of a metallurgical vessel 5. The metallurgical vessel 5 contains liquid metal (not displayed). The wall of the metallurgical vessel 5 comprises an outer (steel) shell 52 and a lining 51. Within the lining 51 a refractory part 50 having a casting channel 2 is provided. The casting channel 2 connects the inside of the metallurgical vessel 5 (in Fig. 1 located at the top) with the outside of the metallurgical vessel (in Fig. 1 located at the bottom).
As shown in Fig. 1, the refractory part 50 might be an inner nozzle and a slide gate 7 might be present on the outside of the casting channel 2 to start or stop the flow of liquid metal or slag from the metallurgical vessel 5 through the casting channel 2. In Fig. 1 the slide gate 7 is in open position and is connected to the metallurgical vessel 5 via a slide gate mount 71. Slide gate controls, outer nozzles, etc. are not displayed in Fig. 1. Preferably the slide gate 7 is removed from the slide gate mount 71 before the casting channel 2 is repaired.
Fig. 2a shows a cross-section of the refractory part 50 from Fig. 1 in unworn state. The casting channel 2 has a channel diameter d2 which initially equals the nominal channel diameter d0. Preferably the nominal channel diameter d0 is constant along the whole of casting channel 2.
During operation of the refractory part 50, the casting channel 2 experiences wear which leads to the channel diameter d2 of the casting channel being (at least partially) extended. Thus, the channel diameter d2 is (at least partially) larger than the nominal channel diameter d0. Said extended channel diameter d2 may vary along the longitudinal axis and in certain regions may still be equal to the nominal channel diameter d0. Fig. 2b shows a cross-section of worn casting channel 2 of refractory part 50 having an unevenly extended channel diameter d2 along the longitudinal axis. The nominal channel diameter d0 is here indicated with dashed lines.
Fig. 3 shows a repair tube 1 of a repair system for repairing a casting channel 2 of a refractory part 50 of a metallurgical vessel 5 in a 3D view and in a cut view. The repair tube 1 has a first and a second longitudinal end A, B and a tube wall 10. The tube wall 10 has an inner surface I with an inner diameter i1 and an outer surface O with an outer diameter o1. An inner space S is defined by the inner surface I. Preferably the inner diameter i1 and/or the outer diameter o1 is constant. The tube wall 10 comprises a plurality of openings 101 connecting the inner surface I to the outer surface O. The repair system also comprises a pressing tool 4 configured to displace a repair mix, e.g., mortar, 3 (not depicted in Fig. 3) from the inner space S of the repair tube 1 through said plurality of openings 101 (as shown in Fig. 5). Preferably at least 9, more preferably at least 18 and most preferably at least 27 openings 101 are in place.
For example, a repair mix comprising 92.5% Al₂O₃, 2.2% SiO₂, 0.2% Fe₂O₃, 0.1% TiO₂, 0.1% MgO and 5.0% P₂O₅ can be used.
The repair tube 1 can comprise a wire mesh, wherein the plurality of openings 101 is formed by said wire mesh. The repair tube 1 may comprise metal, preferably steel, and/or refractory material. The length of the repair tube 1 may be 200 to 700 mm, the outer diameter o1 may be 30-110 mm.
The repair tube 1 by way of example disclosed comprises circular openings 101. Other shapes might be used, e.g., squared, rectangular and/or oval openings 101 or openings 101 in the shape of a slit or long hole. A combination of variously shaped openings might be utilized in one repair tube 1.
The shortest distance between two opposite parallel lines tangent to the circumference of the each opening 101 of the plurality of openings 101, such as a diameter in case of a circular opening, such as a (smaller) side length in case of a square or of a rectangle each might be 2 mm to 12 mm, preferably 3 mm to 5 mm.
To repair the casting channel 2, the repair tube 10 is longitudinally inserted into the casting channel 2 as shown in Fig. 4a or Fig. 5a. This can be done while the refractory part 50 is mounted in the metallurgical vessel 5 (the metallurgical vessel 5 is not shown in Fig. 4a). If the casting channel 2 of an inner nozzle as refractory part 50 is to be repaired as shown in Fig. 1 it is preferable when the slide gates 7 are removed beforehand. The outer diameter o1 of the repair tube 1 is smaller than the channel diameter d2 of the casting channel 2. Thus, a cavity C is left in between the outer surface O of the repair tube 1 and the worn-out casting channel 2. The repair tube 1 can be prefilled with repair mix 3 as shown in Fig. 4a or Fig. 5a or can be filled with repair mix 3 after the repair tube 1 is inserted into the casting channel 2. For doing so a chamber filled with repair mix 3 can be provided at the pressing tool 4. All of the repair mix 3 is supplied to the inner space S of the repair tube 1 prior to the step where the repair mix 3 is pressed from the inner space S of the repair tube 1 through the plurality of openings 101 to fill the cavity C by using a pressing tool 4. In Fig. 4a and Fig. 5a also a slide gate 7 is depicted to show how the repair tube 1 can be inserted and also how the pressing tool 4 can be applied through from the outside of the metallurgical vessel 5 through said slide gate 7. An additional refractory part, e.g., an outer nozzle, mounted below the slide gate 7 and/or above the slide gate 7 can be dismounted before repairing the refractory part 50 (here an inner nozzle). The outer nozzle and/or the slide gate 7 might also be left mounted during repair.
Preferably the piston 41 as well as the repair mix 3 is placed within the repair tube 1 before the repair tube 1 is inserted into the casting channel 2.
Fig. 4a and 5a respectively show a pressing tool 4 comprising a base 40 and longitudinally displaceable piston with a piston head 41 and a piston shaft 42. Preferably, the piston head 41 has a diameter fitting to the inner diameter i1 of the repair tube 1. The pressing tool 4 shown in the Figures also comprises a base 40 having a sliding hole for sliding the piston shaft 42, which in turn is connected to the piston head 41. The piston head 41 can be configured detachably from the piston shaft 42, in particular when the piston is pushed through the repair tube.
The pressing tool 4 is attached to one end of the repair tube 1.
In Fig. 4b the piston head 41 shown in Fig. 4a is longitudinally pushed through the repair tube 1 away from the base 40 of the pressing tool 4 by actuating the piston shaft 42.
Fig. 5b shows the piston 41 according to Fig. 5a which is pulled through the repair tube 1 to displace the repair mix 3 through the plurality of openings 101. Here also a piston shaft 41 is slid through the base 40 and thus pulling the piston head 42 which displaces the repair mix 3.
After the repair mix 3 is pressed into said cavity C, the repair tube 1 can be removed, in which case the repair mix 3 defines the new casting channel 2 as shown in Fig. 6a. In this case it is beneficial if the outer diameter o1 of the repair tube 1 is equal to the nominal diameter d0 of the casting channel 2.
Instead of removing the repair tube 1, it can also be left inside the casting channel 2 of the refractory part 50, in which case the inner surface I of the repair tube 1 is used as a new casting channel 2 as shown in Fig. 6b, while the openings 101 are filled with repair mix, leaving an even inner surface I and thus casting channel 2. In this case it is beneficial if the inner diameter i1 of the repair tube 1 is equal to the nominal diameter d0 of the casting channel 2.
Preferably after pressing the repair mix 3 through the plurality of openings 101 and into the cavity C, any excess repair mix 3 which was not pressed through the openings 101 has been pressed or pulled through the repair tube 1 and might fall off. Although usually this excess repair mix 3 does not have any negative effect for operation of the casting channel 2 it might also be removed manually if it does not fall off by itself.

Claims

Method for repairing a casting channel (2) of a refractory part (50) for a metallurgical vessel (5), characterized in that a repair tube (1), comprising a tube wall (10) having an inner surface (I) with an, preferably constant, inner diameter (i1) defining an inner space (S) and having an outer surface (O) with an, preferably constant, outer diameter (o1), the tube wall (10) having a plurality of openings (101) connecting the inner surface (I) to the outer surface (O), is longitudinally inserted into the casting channel (2), such that after insertion a cavity (C) in between the outer surface (O) and the casting channel (2) is formed, and that a repair mix (3) is pressed from the inner space (S) of the repair tube (1) through said plurality of openings (101) to fill said cavity (C) by using a pressing tool (4).
Method according to claim 1, characterized in that the repair mix (3) is pressed through said plurality of openings (101) by displacing a piston (41) via the pressing tool (4).
Method according to claim 2, characterized in that the repair mix (3) is pressed through said plurality of openings (101) by displacing the piston (41) via the pressing tool (4), whereas the piston (41) is at least partially displaced within the inner space (S) of the repair tube (1).
Method according to any of the preceding claims, characterized in that after the repair mix (3) is pressed into said cavity (C), the repair tube (1) is left inside the casting channel (2) of the refractory part.
Method according to any of the preceding claims, characterized in that the inner space (S) of the repair tube (1) is at least partially filled with the repair mix (3) prior to the insertion of the repair tube (1) into the casting channel (2).
Repair system for repairing a casting channel (2) of a refractory part (50) for a metallurgical vessel (5), characterized in that the repair system comprises a repair tube (1), the repair tube comprising a tube wall (10) having an inner surface (I) with an, preferably constant, inner diameter (i1) defining an inner space (S) and an outer surface (O) with an, preferably constant, outer diameter (o1), that the tube wall (10) comprises a plurality of openings (101) connecting the inner surface (I) to the outer surface (O), that the repair tube (1) is longitudinally insertable into the casting channel (2) such that after insertion a cavity (C) is at least partially formed in between the outer surface (O) of the repair tube (1) and the casting channel (2), and that the repair system further comprises a pressing tool (4), configured to press a repair mix (3) from the inner space (S) of the repair tube (1) through said plurality of openings (101) to fill said cavity (C).
Repair system according to claim 6, characterized in that the repair tube (1) comprises a mesh, wherein the plurality of openings (101) is formed by said mesh.
Repair system according to claim 6 or 7, characterized in that the repair tube (1) comprises metal, preferably steel, and/or refractory material and/or cardboard.
Repair system according to any one of claims 6 to 8, characterized in that the repair tube (1) has a length of 100 mm to 2500 mm, preferably 200 to 700 mm.
Repair system according to any one of claims 6 to 9, characterized in that the shortest distance between two opposite parallel lines tangent to the circumference of each opening (101) out of the plurality of openings (101) is 0.5 to 15 mm, preferably, 2 mm to 10 mm, most preferably 3 mm to 5 mm.
Repair system according to any one of claims 6 to 10, characterized in that the outer diameter (o1) of the repair tube (1) is 30 to 110 mm.
Repair system according to any one of claims 6 to 11, characterized in that the inner diameter (i1) of the repair tube (1) is 25 mm to 105 mm.
Repair system according to any one of claims 6 to 12, characterized in that the pressing tool (4) comprises a displaceable piston (41).
Use of a repair system according to any one of claims 6 to 13, wherein the repair tube (1) is longitudinally inserted into a casting channel (2), such that after insertion a cavity (C) is formed in between the outer surface (O) of the repair tube (1) and the casting channel (2), and in that a repair mix (3) is pressed from the inside of the repair tube (1) through said plurality of openings (101) to fill said cavity (C).