US3623536A

US3623536A - Method and mold for continuously casting metallic elements

Info

Publication number: US3623536A
Application number: US874794A
Authority: US
Inventors: Gunther Moritz
Original assignee: Vereinigte Aluminium Werke AG
Current assignee: Vereinigte Aluminium Werke AG
Priority date: 1968-11-12
Filing date: 1969-11-07
Publication date: 1971-11-30
Anticipated expiration: 1988-11-30
Also published as: AT300232B; LU59479A1; NL6916093A; FR2023029A7; CH501445A; NO124521B; DE1808418B1; GB1236291A; BE740661A

Abstract

A mold for continuous casting of metallic elements has a passage which is oriented substantially vertically and has an upper open end and a lower open end so that metal introduced into the upper open end in molten state will solidify within the passage and advance therewithin in solidified form towards and beyond the lower open end. The passage is so configurated that its inner circumferential wall is spaced from the outer surface of the solidified metal element which forms and advances within the passage. The cross section of the passage first diverges and then converges in the direction from the upper open end to the lower open end. Cooling water conduits are provided in the mold and communicate with the passage in the convergent portion thereof, being so arranged that in this portion they cool only the mold and thereby indirectly the solidified metal element, whereupon the water runs along the inner circumferential wall of the passage to the throat or narrowest part of the convergentdivergent cross section where it contacts and directly cools the advancing metal element. The injection of water through the conduits into the convergent portion of the passage produces a venturi action and the resulting underpressure in the passage is utilized to draw air, a desired gas and/or lubricating fluid into the passage.

Description

United States Patent [72] inventor Gunther Moritz Bad Godesberg, Germany [21] Appl. No. 874,794 [22] Filed Nov. 7, 1969 [45] Patented Nov. 30, 1971 [73] Assignee Vereinigte Aluminium-Werke Aktiengesellschaft Bonn, Germany [32] Priority Nov. 12, 1968 [33] Germany [31] P18084183 [54] METHOD AND MOLD FOR CONTINUOUSLY CASTING METALLIC ELEMENTS 11 Claims, 2 Drawing Figs.

[52] US. Cl 164/89, 164/283. 239/428.5 [Sl] int. Cl 822d 11/12 [50] Field of Search 164/89, 283; 239/1323, 428.5, 419.5

[56] References Cited UNlTED STATES PATENTS 2,366,354 1/1945 Robbins 239/4285 3,381,741 5/1968 Gardner 164/283 X 3,463,220 8/1969 Moritz 164/89 X Primary Examiner Robert D. Baldwin Attorney-Michael S. Striker ABSTRACT: A mold for continuous casting of metallic elements has a passage which is oriented substantially vertically and has an upper open end and a lower open end so that metal introduced into the upper open end in molten state will solidify within the passage and advance therewithin in solidified form towards and beyond the lower open end. The passage is so configurated that its inner circumferential wall is spaced from the outer surface of the solidified metal element which forms and advances within the passage. The cross section of the passage first diverges and then converges in the direction from the upper open end to the lower open end. Cooling water conduits are provided in the mold and communicate with the passage in the convergent portion thereof, being so arranged that in this portion they cool only the mold and thereby indirectly the solidified metal element, whereupon the water runs along the inner circumferential wall of the passage to the throat or narrowest part of the convergent-divergent cross section where it contacts and directly cools the advancing metal element. The injection of water through the conduits into the convergent portion of the passage produces a venturi action and the resulting underpressure in the passage is utilized to draw air, a desired gas and/or lubricating fluid into the passage.

PATENTEDNUV 30 IHTI 3,623,536

INVENTOR GuurHEn NMITZ ATTORN EY METHOD AND MOLD FOR CONTINUOUSLY CASTING METALLIC ELEMENTS BACKGROUND OF THE INVENTION The present invention relates generally to the continuous casting of metallic materials, and more particularly to a method of such casting and a mold for carrying out the method. Still more specifically the invention relates to such a method and mold for the continuous casting of metallic elements of small thickness such as wires, bands, tapes and the like.

It is already known to effect continuous casting by introducing the molten metal into the upper open end of a mold passage having a vertical orientation and a lower open end. The molten metal introduced into the passage undergoes cooling as it advances under the influence of gravity through the passage towards and outwardly beyond the lower open end, and as a result of such cooling it solidifies. What emerges from the lower open end of the passage is a metal element of desired cross-sectional configuration. It is known to provide two types of cooling in one and the same mold, namely to cool the entering molten metal in the region of the upstream end of the passage indirectly via the use of cooling water jets, which are directed against a heat-exchange surface with which the metal comes in contact and subsequently to effect direct cooling of the now-solidified metal element at a location downstream of the indirect cooling, that is closer towards the outlet end of the passage. However, it has been found that at the desired casting speeds and the large quantities of water and significant water pressures required under these circumstances, there exists the danger that the cooling water which directly contacts the outer surface of the solidified metal elements might backup and rise into the region of the mold passage where only indirect cooling is desired. This causes the formation of steam within the mold and finally prevents proper casting in that portion of the mold passage where only indirect cooling can be utilized.

SUMMARY OF THE INVENTION It is, accordingly, an object of the present invention to overcome the aforementioned disadvantages.

More particularly it is an object of the present invention to provide an improved method of continuously casting molten metal elements, particularly metal elements of small thickness such as wires, tapes, bands and the like.

A further object of the invention is to provide a mold for carrying the novel method into effect.

In pursuance of the above objects, and others which will become apparent hereafter, one feature of the invention resides in a mold for continuous casting of metallic elements, particularly elements of small thickness such as wires and bands, which mold comprises, briefly stated, wall means defining an upright passage having an inlet end portion bounded by a forming surface, an outlet end portion and a convergentdivergent cross section in direction from the former to the latter of these end portions. Feed means feeds into the inlet end portion a stream of molten metal for forming therein solidification and advancement as a metallic element through the passage to the outlet end portion. Cooling means introduces into the region of the inlet end portion water in such a manner as to indirectly cool the metallic element and into the region of convergent-divergent cross section jets of water in such a manner as to directly cool the metallic element, and it further serves for producing in this passage an underpressure sufficient to aspirate auxiliary fluids in the passage.

The production of the underpressure is based, of course, on the fact that in the throat of the passage, that is the region of narrowest cross section where the convergent and divergent portions of the passage merge, a venturi effect is produced by the injection of the jets of cooling water into the divergent portion of the passage. In this manner backup or rising of the cooling water from the region of the convergent-divergent cross section of the passage into the entrance end of the passage in which indirect cooling only is to be effected, is avoided. The underpressure is utilized to aspirate auxiliary fluids into the passage. Thus, air may be aspirated in this manner and become admixed with the cooling water so that the latter does not impinge in form of jets upon the outer surface of the advancing solidified metallic element, but rather in form of a spray, with a resulting decreasing of the cooling intensity and a concomitant decrease in the tendency towards formation of cracks and fissures in the material of the solidified metal element, which tendency is of course highly undesirable particularly at the high casting speeds which are required in molds of this type. Furthermore, in this manner the cooling intensity can be reduced to such an extent that the solidified element will still be warm as it issues from the downstream end of the passage and can thus still be formed in warm state directly on leaving the downstream end and immediately after being formed by casting.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective fragmentary section through a mold according to the present invention, with the casing direction being indicated by the illustrated arrow; and

FIG. 2 is a fragmentary vertical section, taken in the casting direction, through the mold according to the present invention and as shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Considering FIGS. 1 and 2 in conjunction with one another it will be seen that reference numeral 1 identifies a chamber which accommodates molten metal which is to be cast. Chamber 1 may be considered a feed means from which molten metal is fed into the upstream open end of the casting passage of the mold. Suitable means, which are not illustrated and fonn no part of the present invention, serve to maintain the level of molten metal in the chamber 1 constant by supplying additional molten metal whenever needed.

The mold is of generally annular configuration in the manner which is already well known in the art. It is provided with a cover plate 4 separating the upper portion 5 of its passage from the chamber 1, a space 3 being provided through which the chamber 1 communicates with the portion 5.

The cover plate 4 consists of a heat-insulating material, that is a material having a low thermal conductivity, and as illustrated it closes that side of the space 5 which faces away from the outlet end of the mold passage.

Reference numeral 6 identifies the circumferential wall surfaces surrounding the space 5 provided at the inlet end portion of the passage and in which the actual forming of the molten metal takes place. Reference numeral 7 identifies water chambers into which cooling waster is introduced under pressure in suitable manner, not illustrated because it forms no part of the present invention. The chambers 7 communicate via the round cross section channel 8 with the space 5, so that the water flows through the channels 8, cooling the surfaces 6 surrounding the space 5 and thus indirectly-but not directlycooling the molten metal which has been introduced from the chamber 4 and which advances in the direction indicated by the arrow in FIG. 1 and solidifies to become a metal element.

As the jets of water issue from the openings 9, the impinge upon the now solidified metal element 10 to efiect direct cooling of the same. It will be appreciated that as the molten metal enters through the space 3 into the space 5, it will immediately solidify in its outer circumferential surface regions upon contact with the water-cooled inner circumferential surfaces 6 bounding the space 5.

Downstream of the space 5 and in communication therewith is a space 11, also constituting a part of the inner mold passage, and in which the metallic element which is solidified only in its surface regions but not yet solidified in its interior, is further cooled directly by contact with the cooling water. It is the particular configuration of the space 11 which provides for the desired venturi effect. For purposes of the present disclosure it may be considered that the passage defined by the two spaces 5 and 11 (of which only the former has a molding function while the latter serves a guiding and cooling function) is composed of two portions of convergentdivergent cross section with the convergent portion extending from the inlet 3 to the region of narrowest cross section, corresponding to the throat of a venturi, whereas the divergent portion extends from the region 15 to the outlet end 16 of the portion I 1.

It will be seen that in the region I3 of the convergent portion, the inner circumferential surface bounding the passage is spaced from the outer surface of the advancing now at least partially solidified metallic element 10. In the illustrated embodiment this space or gap 13 is subdivided by a plurality of ridges 14 extending in the casting direction (compare FIG. 1) and being circumferentially spaced from one another. However, it is possible to omit these ridges 14.

It will be appreciated that because of the venturi-shaped configuration of the circumferential surface 12 bounding the passage downstream of the surfaces 6, the gap or space 13 first converges in cross section to the throat 15 and from there diverges in cross section, and that therefore the injection of water jets in the conduits 8 causes in the area of the openings 6 an underpressure. I further provide the air inlet conduits 17 which communicate with the gap 13 in the region of the openings 9 and whose outer ends communicate with the ambient atmosphere, in the illustrated embodiment with the chambers 18 which in turn communicate with the outer atmosphere via openings which can be controlled by suitable valves so that by regulating the valves it is possible to regulate the quantity and pressure of air in the chamber I8 and therefore regulate the quantity of air which enters through the conduits 17 in the gap l3. Such regulation may be effected manually or automatically by suitable means which is well known and forms no part of the present invention.

As reference to FIG. 2 shows particularly clearly, the molten metal entering into the space 5 does not immediately expand to assume a configuration corresponding precisely to the cross-sectional area of the space 5. Instead, because of its surface tension it forms a meniscus so that an annular hollow space 19 develops between the outer surface of the entering molten metal, the surfaces 6 and the cover plate 4. Because the surface of the solidified metallic element 10 does not usually form an airtight seal with the surfaces 6, this space I9 communicates with the cap 13 and therefore with the remainder of the passage, so that the underpressure which develops in the gap 13 also exists in the space I9, with the result that the underpressure can be utilized for aspirating into the space 19 suitable lubricating fluids via the lubricating channels 20 which are provided for this purpose. Inserts 21 of noncombustible porous material are interposed between the outlet ends of the lubricating channels 20 and the space 19, being pervious to the lubricating fluid which is supplied, for instance oil.

It will be appreciated that it is possible also to aspirate other types of auxiliary fluids, for instance a neutral or inert gas if this is desired, or a gas having good heat-conducting properties. The use of an inert gas may serve to reduce or avoid the formation of oxides on the surface of the metallic element 10, whereas the use of a gas having good heat-conductive properties may be desirable if it is found necessary to make the indirect cooling of the cast solidified element 10 more effective.

The lubricating fluid, if and when it is supplied, may be in liquid form or in vapor form. The existing underpressure serves to obtain an even finely divided distribution of the lubricating fluid which facilitates lubrication of the element 10. Naturally, it is possible in all cases to manually or automatically control and regulate the quantity of cooling water, the quantity of air or gas and of lubricating fluid which are introduced into the passage of the mold, and to thereby vary the cooling effectiveness of the water-gas mixture obtained, the cooling obtained in the region where indirect cooling is effected via the surfaces 6, and the amount of lubrication provided.

While it has been found particularly advantageous to provide the ridges 14, which serve to guide the element 10 and the cooling water, the provision of such ridges is not absolutely necessary. Their absence does not affect the advantages and scope of the present invention.

It is emphasized that the present invention is applicable to molds wherein the passage is vertically oriented, as well as to those wherein the passage is substantially horizontally oriented, both such types of molds being known to those skilled in the art, and that the invention resides not in the particular orientation of the casting passage with reference to the horizontal but in those features which have been described above and which are set forth in the appended claims.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a mold for continuous casting of metallic material, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic and specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended I. A method of continuously casting metallic elements, particularly elements of small thickness such as wires and bands, in a mold having a passage composed of an upstream casting portion and a downstream portion provided with an outlet and being of convergent-divergent cross section in direction towards said outlet, comprising the steps of introducing a stream of molten metal into said upstream portion for solidification and advancement as a metal element through said downstream portion towards said outlet; indirectly cooling said element in said upstream portion; directly cooling said element in said downstream portion by introducing into the convergent region of said convergent-divergent cross section jets of water at a velocity requisite for producing in said passage a venturi effect; and utilizing the thus obtained venturi effect for aspirating auxiliary fluid into said passage.

2. A method as defined in claim I; and further comprising the step of establishing communication between said passage and the ambient atmosphere so that the auxiliary fluid aspirated into said passage includes air.

3. A method as defined in claim I; and further comprising the step of establishing communication between said passage and a source of gas having good thermal conductivity so that the auxiliary fluid aspirated into said passage includes said gas.

4. A method as defined in claim 1; and further comprising the step of establishing communication between said passage and a source of neutral gas, so that the auxiliary fluid aspirated into said passage includes said gas.

5. A method as defined in claim I; and further comprising the step of establishing communication between the region of convergent cross section of said passage and a source of lubricating fluid, so that the auxiliary fluid aspirated into said passage includes said lubricating fluid.

6. Mold for continuous casting of metallic elements, particularly elements of small thickness such as wires and bands, comprising wall means defining an upright passage having an upstream casting portion and a downstream portion provided with an outlet end and being of convergent-divergent cross section in direction towards said outlet end; feed means for feeding into said upstream portion a stream of molten metal for solidification and advancement as a metallic element through said downstream portion to said outlet end; a plurality of channels having outer ends communicating with a source of auxiliary fluid, and inner ends communicating with said downstream portion in the region of the convergent cross section thereof; and cooling means for introducing into the region of convergent cross section of said passage jets of water in such a manner as to indirectly cool the metallic element in said upstream portion and directly cool the metallic element in said downstream portion and for producing in said passage an underpressure sufficient to aspirate said fluid into said passage, said cooling means comprising a plurality of water conduits communicating with said downstream portion in the region of said convergent cross section adjacent said inner ends of said channels.

7. Mold as defined in claim 6, wherein said cross section of said downstream portion is narrowest at a throat located at the juncture of the regions of convergent and divergent cross section; and wherein said cooling means is operative for introducing said water jets at a velocity requisite for producing a venturi effect in said throat.

8. Mold as defined in claim 7; and further comprising a plurality of ribs provided on an inner surface bounding said downstream portion, and extending in longitudinal direction of said passage at least in the region of said juncture with spacing from one another circumferentially of said passage.

9. Mold as defined in claim 14, wherein at least some of said channels are air channels, and said outer ends thereof communicate with the ambient atmosphere.

l0. Mold as defined in claim 6; and further comprising lubricating fluid conduits having inner ends communicating with said passage in the region of said upstream portion thereof, and other ends communicating with a source of lubricating fluid.

ll. Mold as defined in claim 10; and further comprising porous means interposed between said passage and said lubricating fluid conduits and being pervious to lubricating fluid passing from said lubricating fluid conduits into said passage.

Claims

1. A method of continuously casting metallic elements, particularly elements of small thickness such as wires and bands, in a mold having a passage composed of an upstream casting portion and a downstream portion provided with an outlet and being of convergent-divergent cross section in direction towards said outlet, comprising the steps of introducing a stream of molten metal into said upstream portion for solidification and advancement as a metal element through said downstream portion towards said outlet; indirectly cooling said element in said upstream portion; directly cooling said element in said downstream portion by introducing into the convergent region of said convergent-divergent cross section jets of water at a velocity requisite for producing in said passage a venturi effect; and utilizing the thus obtained venturi effect for aspirating auxiliary fluid into said passage.

2. A method as defined in claim 1; and further comprising the step of establishing communication between said passage and the ambient atmosphere so that the auxiliary fluid aspirated into said passage includes air.

3. A method as defined in claim 1; and further comprising the step of establishing communication between said passage and a source of gas having good thermal conductivity so that the auxiliary fluid aspirated into said passage includes said gas.

5. A method as defined in claim 1; and further comprising the step of establishing communication between the region of convergent cross section of said passage and a source of lubricating fluid, so that the auxiliary fluid aspirated into said passage includes said lubricating fluid.

10. Mold as defined in claim 6; and further comprising lubricating fluid conduits having inner ends communicating with said passage in the region of said upstream portion thereof, and other ends communicating with a source of lubricating fluid.

11. Mold as defined in claim 10; and further comprising porous means interposed between said passage and said lubricating fluid conduits and being pervious to lubricating fluid passing from said lubricating fluid conduits into said passage.