Liquid-cooled plate mold

Abstract

A liquid-cooled plate mold for continuous casting of metals has highly heat-conductive mold plates of copper or a copper alloy. The mold plates have a water side. A fastening support for each mold plate is provided for securing the mold plate thereon. The fastening support is in the form of a water box or a support plate. Fastening elements for securing the mold plates to the fastening supports are provided. Shaped parts having a thread are arranged on the water side of the mold plates. The shaped parts form fastening pieces that are non-positively connected by soldering connections or welding connections to the mold plates, wherein the fastening elements engage the fastening pieces.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to a liquid-cooled plate mold for the continuous casting of metals, in particular, of steel materials, comprising highly heat-conductive mold plates of copper or copper alloys which are connected by means of fastening bolts with a fastening support in the form of a water box or a support plate, respectively.

[0003] 2. Description of the Related Art

[0004] The plate attachment of mold plates of identical thickness by means of welded-on bolts is known. As a result of the plate expansion caused by temperature increase during the casting operation, additional bending loads and tension loads result, especially in the case of short bolts, and this can cause failure of the welding connection.

[0005] The patent document DE 197 16 450 A1 describes a liquid-cooled mold for continuous casting of thin steel slab with two oppositely positioned wide sidewalls, each comprised of a copper plate and a steel support plate. The copper plates, which delimit a cavity of the mold, are detachably connected by means of metal bolts of a CuNiFe alloy to the support plates. The metal bolts are welded onto the copper plates. When doing so, a nickel ring is additionally used as a welding additive. In the copper plates cooling medium channels are provided, and cooling medium bores are provided in the area of the transverse section planes of the metal bolts. The gist of the aforementioned mold is the feature that metal bolts of a CuNiFe alloy are being used. As a result of using such, especially hard drawn, metal bolts, a significant strength increase with only minimal strength fluctuations in regard to the welding connections with a copper plate is said to be achievable. Expediently, bolt welding methods that are known in the art are used for the attachment of the metal bolts on the copper plates.

[0006] The patent document WO 95/21 036 describes an assembly group of a mold for continuous casting of steel with a support plate. A copper or copper alloy plate with excellent heat conducting properties is screwed onto the support plate and a relatively thin cover layer of copper or copper alloy is soldered onto the copper plate. If desired, the plate with excellent heat conducting properties can be omitted and the cover layer can be soldered directly onto the support plate. The cover layer contacts and cools the cast strand passing through when moving through the mold. When the cover layer shows cracks or wear, the solder connection is melted in order to remove it and a new layer is soldered onto the thermally conductive layer or the support plate.

[0007] The patent document DE 198 01 728 C1 discloses a continuous casting mold for casting strands of, preferably, steel. The mold is comprised of mold plates and water boxes which are connected to one another and between which a water cooling system is provided with the aid of water guiding channels. The water guiding channels are arranged at the side of the water box facing the mold plate and not within the mold plate. A continuous casting mold of this configuration is improved in that the wide side of the mold with its elements copper plate and/or water box with water guiding channels or with a water box without water guiding channels, but with a connecting plate having water guiding channels, is secured by means of clamping bolts. They have substantially conical clamping bolt heads which are secured in conical recesses of the copper plate.

[0008] In this configuration, the bolt head of the clamping head should have a special conical shape or be conical-lamella-shaped, and, advantageously, should be comprised of the same material as the copper plate of the continuous casting mold. In order to optimize the heat conductivity between the clamping bolt/clamping bolt head and the copper plate, the surfaces between the copper plate and the clamping bolt/clamping bolt head can be provided with a highly conductive layer of metal, preferably silver. A further improvement of the connection of the copper plate and clamping bolt is achieved when the connection is provided on the cold side of the copper plate with a seal against water passage across the surface in the direction of the hot side.

[0009] The patent application DE 198 35 119.9, not yet published, concerns a mold wall of a continuous casting device for casting a metal strand, in particular, a steel strand, with a water box and an inner mold plate connected by bolts to the water box. The bolts have a bolt neck, respectively, penetrating the water box and having a bolt neck cross-section, and a bolt head, secured in the inner mold plate and having a bolt head cross-section. For simplifying securing of the bolt in the inner mold plate, it is suggested that the bolt head cross-section of at least one of the bolts is greater than the bolt neck cross-section of this bolt, and that the inner mold plate has a groove which tapers in a direction toward the water box for receiving the bolt head of this bolt.

[0010] Finally, the German published document 15 08 902 discloses a liquid-cooled plate mold for continuous casting of high-melting metals in which a mold wall is connected by fastening screws to a support frame. Round rods are provided which are inserted into bores of the mold wall transverse to the casting direction and are provided with threaded bores for receiving fastening screws. The assembly expenditure for this configuration is considerable.

SUMMARY OF THE INVENTION

[0011] It is an object of the present invention to control or minimize for a liquid-cooled plate mold of the aforementioned kind the difficulties and problems in the area of the connection of the inner mold plates, comprised of copper or copper alloys, with bearing, supporting, or shape-providing support plates or water box plates of copper or steel during the temperature changes occurring during the continuous casting operation and to provide a safe type of attachment for tension-loaded as well as thermally loaded fastening elements on inner mold plates of copper, which attachment can be realized with economically feasible expenditure of cost and labor and is suitable to provide a longer and failure-free service life.

[0012] In accordance with the present invention, this is achieved in that in the on the water side of each mold plate shaped parts provided with threads are arranged and connected by soldering connections or by welding connections with the mold plates in a non-positive way as a fastening piece.

[0013] Such soldering connections and/or welding connections can be produced easily, on the one hand, and have fatigue strength under reversed stresses of, for example, 100 N/mm2, on the other hand.

[0014] Advantageously, for this connection, the shaped parts or fastening pieces are preferably produced of a material with excellent conducting properties such as CuAg, CuCrZr, CuNiBe, or CuNiFe.

[0015] The fastening pieces can be connected by a soft solder layer with high shearing strength with the mold plates.

[0016] However, it is also possible to use the measure of connecting the fastening pieces by a hard solder layer with the mold plates, wherein preferably a silver-containing or copper-containing hard solder is used as a solder metal.

[0017] It is furthermore possible to connect the fastening piece with the mold plate by high-temperature soldering. The heating of the soldering location can be realized in this context by electron beam or by electric current.

[0018] It is particularly advantageous to connect the fastening piece with the mold plate by electron beam welding.

[0019] For this purpose, the fastening piece can also be inserted into a shallow, round recess of relatively minimal depth at the backside of the mold plate. The welding connection is then carried out annularly along the separating location between the mold plate and the fastening piece. The electron beam can impinge perpendicularly or at an angle onto the surface of the mold. The fastening pieces can be provided with a step or shoulder which is of such a size that it is flush with the upper rim of the recess, as illustrated in FIG. 2.

[0020] The fastening pieces, as described above, can be produced of a metal material of good conducting properties or a suitable steel alloy.

BRIEF DESCRIPTION OF THE DRAWING

[0021] In the drawing:

[0022] FIG. 1 is a section of a portion of an inner mold plate with a shaped part attached by soldering and fastening bolts of a support plate screwed into the shaped part;

[0023] FIG. 2 shows in section a detail of FIG. 1 with the shaped part attached by electron beam welding.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The part of a liquid-cooled plate mold illustrated in FIG. 1 for continuous casting of high-melting metals, such as steel, comprises a highly heat-conductive mold plate 1 of copper or copper alloy which is connected by means of fastening elements in the form of fastening bolts 2 on a fastening support. The fastening support can be a water box, e.g., the backside of the water box, or a support plate 4 provided with channels 3 for the cooling water. The channels for the cooling water can also be located within the mold plate.

[0025] According to the invention, on the water side of the mold plate 1 shaped parts 6 with threaded bores 5 for screwing in the fastening bolts 2 are arranged and connected by a non-positive connection with the mold plate 1 by means of soldering connections 7, 7′ in order to provide fastening pieces. The shaped parts or fastening pieces 6 are preferably produced of a metal material having good conducting properties such as CuAg, CuCrZr, CuNiBe, or CuNiFe. The fastening pieces 6 are connected by a soft solder layer 7 with the mold plates 1. The soft solder layer 7 with a high shearing strength is preferably produced of a solder material of the alloys L CdZn or L CdZnAg or L SnCdZn.

[0026] However, it is also possible to employ the measure of connecting the fastening pieces 6 by a hard soldering layer 7′ with the mold plates 1, wherein the solder metal is preferably copper solder alloy or a silver solder alloy.

[0027] It is moreover possible to connect the fastening pieces 6 by high-temperature soldering by means of an electron beam or by means of electrical current with the mold plates 1.

[0028] The hard solder connection provides at soldering temperatures above approximately 450° C. a comparatively high strength in comparison to a soft solder connection; however, in comparison to the soft solder connection, it is somewhat more prone to solder fractures when subjected to changing temperatures and requires a higher expenditure during manufacture and cannot be removed (by melting) without affecting the surrounding material, in particular, copper, in the case of repairs.

[0029] One embodiment of the invention suggests that the soldering surface of the mold plates for the fastening pieces 6 is metallized for an exact positioning of the fastening pieces 6.

[0030] An inventive embodiment also suggests that the fastening pieces 6 are shaped parts with preferably annular cross-section which are inserted into congruent shallow recesses 8 of relatively minimal depth (see FIG. 1), for example, up to 5 mm, in the backside of the mold plate 1 and are soldered therein, and that the support plate 4 has a cooling medium bore 9 having a spacing on all sides relative to the fastening piece 6 positioned in the bore 9 and being in flow communication with at least one cooling medium channel 3. The cooling medium bore 9 can also be provided in the plate of the water box.

[0031] This configuration of the bolt attachment has the advantage that the fastening piece 6 as well as the shaft of the bolt 2 are exposed to the flow of cooling water and are therefore sufficiently cooled. Thus, the endangerment of the solder connections is reliably prevented.

[0032] For the same purpose, according to another embodiment of the invention, it is suggested to provide the support plate 4 with receiving bores 2′ for receiving the fastening bolts 2, which receiving bores 2′ have a diameter that is greater than the shaft diameter of the fastening bolts 2. This results in the formation of annular gaps 10, and, according to the invention, each of these annular gaps 10 is connected with a cooling medium bore 9 supplying cooling water.

[0033] The aforementioned embodiment has furthermore the advantage that temperature-caused expansion differences between the mold plate 1 and the support plate 4 can be compensated easily.

[0034] Moreover, if desired, it is possible to use the measure of arranging the cooling medium channels 3 either in the mold plate 1 or in the support plate 4 or in a plate of the water box contacting the mold plate.

[0035] Finally, the cooling medium channels 3 in the mold plate 1 can be configured either as grooves or as channel bores extending preferably in the casting direction.

[0036] FIG. 2 shows in section a detail of FIG. 1 with the shaped part 6, which, as an alternative solution of the aforementioned object, is fixedly connected by an electron beam welding seam 12 with the mold plate 1. The welding seam is positioned at the exterior side of the shaped part (fastening piece) 6. Before welding is carried out, the outer diameter of the shaped part, which in cross-section is annular, has a diameter which is greater by 1 to 8 mm in the area of the welding seam 12. For the electron beam welding step, the mold plate 1 can have in the area of the attachment a minimal material projection which corresponds approximately to the height of the welding seam depth. The shaped part (fastening piece) 6 is provided with an inner thread 5 for attachment of the fastening bolt 2 (FIG. 1). The shaped part can also be in the form of a bolt with outer thread.

[0037] The channels 3 of the support plate 4 for supplying cooling water are indicated only partially, and the bore 9 supplying the cooling water is also only partially indicated.

[0038] While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

Claims

1. A liquid-cooled plate mold for continuous casting of metals, the plate mold comprising:

highly heat-conductive mold plates of copper or a copper alloy, the mold plates having a water side;

a fastening support for each one of the mold plates configured to have the mold plate secured thereon, wherein the fastening support is in the form of a water box or a support plate;

fastening elements configured to secure the mold plates to the fastening supports;

shaped parts having a thread and being arranged on the water side of the mold plates, wherein the shaped parts form fastening pieces that are non-positively connected by soldering connections or welding connections to the mold plates, wherein the fastening elements engage the fastening pieces.

2. The plate mold according to

claim 1, wherein the fastening pieces are comprised of a conducting metal material selected from the group consisting of CuAg, CuCrZr, CuNiBe, and CuNiFe.

3. The plate mold according to

claim 1, wherein the soldering connection connecting the fastening pieces to the mold plates is a soft solder layer.

4. The plate mold according to

claim 3, wherein the soft solder layer has high shearing strength and is comprised of a solder alloy material selected from the group consisting of L CdZn, L CdZnAg, and L SnCdZn.

5. The plate mold according to

claim 1, wherein the soldering connection connecting the fastening pieces to the mold plates is a hard solder layer.

6. The plate mold according to

claim 5, wherein the hard solder layer is comprised of a solder alloy material selected from the group consisting of a copper alloy and a silver alloy.

7. The plate mold according to

claim 1, wherein the soldering connection connecting the fastening pieces to the mold plates is a high-temperature soldering connection.

8. The plate mold according to

claim 7, wherein the high-temperature soldering connection is made by using an electron beam or electric current.

9. The plate mold according to

claim 7, wherein the high-temperature soldering connection comprises a high-temperature solder layer comprised of a solder material selected from the group consisting of copper alloy and silver alloy.

10. The plate mold according to

claim 1, wherein the mold plates have solder surfaces where the fastening pieces are connected and wherein the solder surfaces are metallized for enabling an exact positioning of the fastening pieces.

11. The plate mold according to

claim 1, wherein the fastening pieces have an annular cross-section, wherein the mold plate has a back side provided with shallow recesses being congruent to the fastening pieces, wherein the fastening pieces are inserted into the recesses and are connected by the soldering connections in the recesses, wherein the fastening support has one or more cooling medium bores, wherein the cooling medium bore surrounds one of the fastening pieces with a spacing to the cooling medium bore being provided all around the fastening piece, wherein the cooling medium bore is in flow communication with at least one cooling medium channel provided in the plate mold.

12. The plate mold according to

claim 11, wherein the fastening pieces have threaded inserts.

13. The plate mold according to

claim 11, wherein the fastening support has receiving bores for receiving the fastening elements in the form of fastening bolts, wherein a diameter of the receiving bores is greater than a diameter of a shaft of the fastening bolts so that an annular gap is formed between the shaft of the fastening bolt and the receiving bore, wherein each one of the annular gaps communicates with one of the cooling medium bores.

14. The plate mold according to

claim 11, wherein the cooling medium channels are arranged in the mold plate or in the support plate or in a plate of the water box resting against the mold plate.

15. The plate mold according to

claim 11, wherein the cooling medium channels are located in the mold plate and are in the form of grooves or channel bores.

16. The plate mold according to

claim 15, wherein the grooves or channel bores extend in the casting direction.

17. The plate mold according to

claim 1, wherein the fastening elements are fastening bolts with a bolt head, wherein support elements, selected from the group consisting of washers and spring elements, are positioned between the bolt heads and the fastening support.

18. The plate mold according to

claim 1, wherein the welding connection connecting the fastening pieces to the mold plates is an electron beam welding seam.

19. The plate mold according to

claim 18, wherein the electron beam welding seam is arranged on an external side of the fastening pieces.

20. The plate mold according to

claim 18, wherein the fastening piece is annular and has an outer diameter with an enlarged diameter portion in the area where the electron beam welding seam is produced.

21. The plate mold according to

claim 20, wherein the enlarged diameter portion is 1 to 8 mm greater than the outer diameter.

22. The plate mold according to

claim 18, wherein the mold plate has projections in the area where the electron beam welding seam is produced, wherein the projections have a height matching a depth of the electron beam welding seam.

23. The plate mold according to

claim 18, wherein the fastening pieces are comprised of steel.

24. The plate mold according to

claim 18, wherein the fastening pieces are comprised of a high-strength copper alloy.

25. The plate mold according to

claim 18, wherein the fastening elements are fastening bolts.

26. The plate mold according to

claim 25, wherein the fastening bolts have an outer thread.

27. The plate mold according to

claim 25, wherein the fastening bolts have a shaft that has an enlarged diameter portion in the area where the electron beam welding seam is produced.

28. The plate mold according to

claim 27, wherein the enlarged diameter portion is greater by 1 to 8 mm than a diameter of the shaft outside the enlarged diameter portion.

29. The plate mold according to

claim 25, wherein the fastening bolts are comprised of steel.