US3463220A - Method for continuous casting of thin bands,plates - Google Patents

Description

G- MORITZ 3,463,220

METHOD FOR CONTINUOUS CASTING OF THIN BAND S, PLATES Aug. 26, 1969 5 Sheets-Sheet 1 Filed July 20, 1966 INVENTOR 643 /4 fiflru g F/GZ METHOD FOR CONTINUOUS CASTING OF THIN BANDS, PLATES Filed July 20, 1966 5 Sheets-Sheet 2 FIG INVENTOR Gdalkar Hon lg NGGJJEIM ATTORN EY G. MORITZ Aug. 26, 1969 METHOD FOR CONTINUOUS CASTING 0F THIN BANDS, PLATES Filed July 20, 1966 5 Sheets-Sheet 5 INVENTQR G t/1H1 or N 17. 1.

Mu aa of #17, ATTORNEY United States Patent 3,463,220 METHOD FOR CONTINUOUS CASTING OF THIN BANDS, PLATES Guenther Moritz, Bad Godesberg, Germany, asslgnor to Vereinigte Aluminium-Werke Aktiengesellschaft, Bonn, Germany Filed July 20, 1966, Ser. No. 566,589

Claims priority, application Germany, July 25, 1965,

V 28,969; Dec. 10, 1965, V 29,888; Dec. 11, 1965,

Int. Cl. B22d 11/12 U.S. Cl. 164-4 7 Claims ABSTRACT OF THE DISCLOSURE A method for continuous casting of thin metal bands or plates in which a continuous stream of molten metal passing through a chill is first indirectly cooled in a first passage portion of the chill with a cooling fluid formed by a mixture of water and air so that outer surface portions of the stream of metal are solidified, whereafter the partly solidified metal strand is directly cooled in a second passage portion of the chill in which longitudinally extending portions of the strand are supported by feeding the mixture of water and air under pressure against unsupported portions of the strand.

The present invention relates to a method for continuous casting of thin bands, plates and the like having preferably a thickness of less than 30 mm. in either substantially horizontal or substantially vertical direction.

Various methods for the continuous casting of thin bands or plates in horizontal direction are known in which the walls confining the cast strand move together with the latter in the casting direction. In these known methods, bands moving with the cast strand are used, or the strand is guided between cooled rolls. These known methods require for their execution complicated and expensive apparatus and these methods have also the d18- advantage that a change of the form giving parts of the apparatus, as well become necessary during operating trouble or during change of the cross section of the strand to be cast, will require considerable time.

Methods and apparatus are also known in which the metal to be cast is fed in liquid form into one end of a vertically extending passage through a water cooled mold or chill and in which the molten metal is solidified at least at outer surface portions thereof by indirect cooling provided by the water cooled chill. In such an arrangement, however, the metal shrinks during its passage through the water cooled chill so that the solidified outer portions of the metal strand will become disengaged from the water cooled wall portions forming the passage through the chill, whereby the cooling effect provided by the chill onto the metal is considerably reduced so that the cast and only partly solidified metal strand may be heated up again by its hot liquid core which may lead to a destruction of the solidified outer skin thereof.

Methods and apparatus are also known in which spray rings are provided surrounding the strand of cast metal as it leaves the mold or chill for spraying a mixture of cooling water and air against the partly solidified strand so as to further cool and completely solidify the material thereof. This method and apparatus has however the disadvantage that complete solidification of the metal strand occurs only outside of the chill at a location where the strand leaving the chill is not supported at all.

It is an object of the present invention to provide for a method which overcomes the disadvantages of the above described methods and apparatus known in the art.

3,463,220 Patented Aug. 26, 1969 It is an additional object of the invention to provide for a method for continuous casting of thin bands, plates and the like in either horizontal or vertical direction and in such a manner that the molten metal fed into a chill is subjected in the latter to an extensive cooling action so that the metal before leaving the chill is solidified to such an extent that breakage of the cast metal strand is positively avoided.

With these objects in view, the method according to the present invention for continuous casting of thin bands, plates and the like mainly comprises the steps of feeding molten metal in a continuous stream and with a predetermined casting speed through a passage of a chill having a cross section substantially equal to the cross section of the band to be cast, cooling the walls forming a first portion of the passage so as to indirectly cool the metal passing therethrough and to solidify outer surface portions thereof so as to form an at least partly solidified strand of metal, supporting the strand along longitudinally extending and transversely spaced surface portions thereof in a second portion of the passage, and feeding a cooling fluid under pressure and at a speed greater than the aforementioned casting speed in longitudinal direction through said second portion of the passage in contact with the surface portions of the strand which are not supported so as to directly cool the strand.

By the direct contact of the cooling fluid with the cast partly solidified strand in the second portion of the passage, the cooling effect produced by the cooling fluid on the strand will not be affected by any shrinkage of the strand so that the latter will be efiectively cooled and substantially completely solidified before leaving the chill.

Up to now it was considered not possible to continuously cast thin bands or plates by direct cooling with water, but it was considered necessary to produce first billets of substantial cross section and to subsequently subject these billets to a rolling process to form therefrom thin bands or thin plates.

The method according to the present invention permits however the production of thin bands and thin plates in a continuous casting process so that a subsequent rolling process for forming such thin bands or plates and the necessary rolling mill for carrying out this rolling process becomes unnecessary.

The method according to the present invention has therefore, as compared with known methods for the production of thin bands and plates, the advantage of smaller initial cost for the apparatus, of simpler operation and the possibility to more quickly exchange the parts which define the form of the cast strand.

During execution of the method according to the present invention it has been noticed that during cooling of the strand in the chill by a liquid cooling medium, especially during casting of alloys of relatively small tensile strength and use of high casting speeds, which for economical reasons are desirable, a tearing of the cast strand did occasionally occur. Experiments have shown that this drawback could be avoided when for the direct cooling of the cast strand in the chill a mixture of water and air has been used.

According to a further feature of the present invention, a mixture of water in air is therefore used for direct cooling of the cast strand in the chill, whereby the chill is constructed in such a manner that such a mixture of air and water may be directly produced in the chill. Experience has shown that with the use of a mixture of air and water for direct cooling of the cast strand in the chill, the tendency of the strand to tear has been greatly reduced. It is thereby advantageous to use also in the first portion of the passage a mixture of water and air for indirectly cooling the molten metal fed into the chill. In this way is possible to vary the cooling intensity to a greater extent than is possible during use of a liquid cooling medium. One possibility to vary the cooling intensity in the indirectly cooled as Well as in the directly cooled portion of the chill consists in varying the amount of water and air which is passed through the chill.

It is also possible to control the cooling speed in an automatic manner by sensing the temperature of the strand of solidified metal emanating from the chill and to vary the amount of water and air to be fed into the chill according to the sensed temperature.

The novel features which are conidered 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 drawings, in which:

FIG. 1 is a longitudinal cross section through a chill according to the present invention in which the passage through the chill is horizontally arranged;

FIG. 2 is a partial perspective view of the passage through the chill viewed from the outlet end, or the left end as viewed in FIG. 1, of the passage;

FIG. 3 is a longitudinal cross section of a chill similar to that shown in FIG. 1 with the passage through the chill arranged in vertical direction;

FIG. 4 is a perspective view of the passage viewed from the outlet end, that is the bottom end as viewed in FIG. 3;

FIG. 5 is a longitudinal cross section through a further modification of the chill constructed for producing a mixture of cooling water and cooling air therein; and

FIG. 6 is a cross section similar to FIG. 5, drawn to a smaller scale, and illustrating also schematically means for automatic control of the amount of cooling water and cooling air fed into the chill.

Referring now to the drawings, and more specifically to FIGS. 1 and 2 of the same, it will be seen that the chill C shown in FIG. 1 is formed with a substantially central passage 1 therethrough which in the arrangement shown in FIG. 1 is horizontally arranged and which has an inlet end at the right side, as viewed in FIG. 1, and an outlet end at the left side. The walls of the chill forming further an enclosed space 6 about the passage 1 into which a cooling fluid, for instance cooling water, is fed through an inlet opening 6 from a source of cooling water, not shown in the drawing. The passage 1 has a first passage portion 1a extending from the right inlet end, as viewed in FIG. 1, and having a cross section substantially identical to the cross section of the strand to be cast in the apparatus, that is a band, a plate, or the like, of small thickness, preferably of a thickness less than 30 mm. The second portion 1b of the passage 1 extends from the inner end of the first passage portion 1a up to the left outlet end of the passage. A plurality of slots 7 extend in longitudinal direction of the second passage portion 1b transversely spaced from each other, as best shown in FIG. 2, to define between themselves a plurality of ribs 8. The slots 7 are open toward the second passage portion 1b and the slots 7 and ribs 8 are preferably arranged on opposite wall portions and respectively aligned with each other as shown in FIG. 2. Bores 4 inclined at about to the longitudinal axis of the passage 1 extend from the inner ends of the slots 7 closely adjacent to the first passage portion 1a and bores 5 provide communication between the outer ends of the bores 4 and the space 6 of the chill so that cooling water may flow from the space 6 through the bores 5 and 4 into the respective slots 7. The arrangement includes further a plate 2 of refractory material abutting against the right end wall, as viewed in FIG. 1, of the chill C, and the plate 2 is formed with a slot 3 therethrough which communicates with the inlet end of the passage 1 and through which by means of known construction, not shown in the drawing, molten metal is continuously fed into the passage 1.

The molten metal reaching the inlet end of the passage will be indirectly cooled during passage thereof through the first passage portion 1a and partly solidified, and in the second passage portion 1b the cooling water passing through the slots 7 will come in direct contact with the partly solidified metal to further cool and solidify the same as it passes through the second passage portion 1b. The cooling efficiency in the second passage portion will not be detrimentally affected by any shrinkage of the metal strand, since even if the metal shrinks to a considerable extent in this passage portion the cooling water will still remain in contact with the metal.

The arrangement shown in FIGS. 3 and 4 is substantially the same as the arrangement discussed in connection with FIGS. 1 and 2, the only difference being that in this arrangement the passage 1 is arranged in vertical direction so that the strand may be cast in vertical direction.

The arrangement shown in FIG. 5 differs from the above two described arrangements in that the chill C shown in FIG. 5 is constructed so that a mixture of cooling water and compressed air may be used for cooling the cast strand in the second passage portion 112 of the passage 1 through the chill. For this purpose the chill is constructed in such a manner that the walls thereof define besides the central passage 1 therethrough a first enclosed space 12 and a second enclosed space 16 arranged in the manner as shown in FIG. 5. A plurality of longitudinal extending slots 7 extend along the second passage portion 1b of the central passage 1 through the chill, which slots 7 are transversely spaced from each other to define between themselves a plurality of ribs 8 as clearly shown and described in connection with FIGS. 1 and 2. A plurality of bores 13 provide communication between the enclosed space 12 into which compressed air is fed through inlet opening 12 as will be described later on in detail and the inner ends of the slots 7. Each of the bores 13 has a bore portion 13 extending closely adjacent and substantially parallel to the first passage portion 1b and a nearly vertical bore portion providing communication between the bore portion 13' and the space 12.

The arrangement includes further, as in the previously described embodiments, a plate 2 of refractory material formed with a slot 3 through which molten metal is fed into the passage 1 of the chill. The molten metal passing through the first passage portion 1a is indirectly cooled by the cooling air passing through the bore portion 13 and in the second bore portion 1b the cooling air passing through the slots 7 will directly cool the metal passing therethrough. T 0 increase the cooling effect, cooling water is mixed with the air. The cooling water fed into the space 16 through inlet opening '16 passes through bores 17 which respectively communicate with the nearly vertical portions of the bores 13 into the latter. The compressed air passing through the bores 13 entrains the Water so that a mixture of water and air is produced. The addition of water increases the cooling action in the bores 13 especially due to the fact that the water flows in part along the walls forming the bores. The cooling action in the slots 7 along the second passage portion 1b is especially increased due to the fact that the water will emanate from the ends of the bore portions 13' into the slots 7 in substantially atomized form and be evaporated by contact with the hot metal strand so that its evaporating heat will withdraw heat from the strand. Accordingly, an increase of the amount of water in the mixture will preponderantly increase the indirect cooling of the metal strand by the cooled wall portion of the chill, whereas an increase of the amount of air in the mixture will preponderantly increase the direct cooling effect produced by the cooling medium passing through the slots 7 in direct contact with the surfaces of the metal strand.

The amount of air and water in the mixture may be automatically controlled and for this purpose temperature sensing means 22 may be arranged closely adjacent to the outlet end of the passage so as to sense the temperature of the metal strand S emanating from the chill as shown in FIG. 6. The temperature sensing means 22 are connected in a known manner to a pair of valves 19 and 21 to open and close the latter to a greater and lesser degree in dependence on the temperatures sensed by the sensing means 22 so as to control flow of air through the conduits 18 into the space 12 and to control flow of cooling water through the conduit 20 into the space 16.

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 method and apparatus for continuous casting of thin metal bands, plates or the like differing from the types described above.

While the invention has been illustrated and described as embodied in a method and apparatus for continuous casting of thin metal bands, plates or the like, 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 or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A method for continuous casting of thin metal bands, plates and the like comprising the steps of feeding molten metal in a continuous stream and with a predetermined casting speed through a passage of a chill having a cross section substantially equal to the cross section of the band to be cast; forming a cooling fluid comprising a mixture of water and air; cooling the walls forming a first portion of the passage with said cooling fluid so as to indirectly cool the metal passing therethrough to thereby solidify outer surface portions of the metal and to form an at least partly solidified strand of metal; supporting said strand along longitudinally extending and transversely spaced surface portions thereof in a second portion of said passage; and feeding said cooling fluid under pressure and at a speed greater than said casting speed in longitudinal direction through said second portion of the passage in contact with the surface portions of the strand which are not supported so as to directly cool the strand.

2. A method as set forth in claim 1, wherein the speed with which said cooling fluid is fed through said second portion of said passage is a multiple of said casting speed.

3. A method as set forth in claim 1, wherein said speed with which said cooling fluid is fed through said second portion of said passage is at least three times said casting speed.

4. A method as set forth in claim 1, wherein said band is cast with a thickness of less than 30 mm.

5. A method as set forth in claim 1, and including the step of varying the amount of air and Water in the mixture to control the extent of solification of the metal in the chill and the temperature of the cast strand.

6. A method as set forth in claim 5, and including the steps of controlling the cooling speed in the first portion of said passage mainly by regulating the amount of water in the mixture and controlling the cooling speed in the second portion of the passage mainly by regulating the amount of air in the mixture.

7. A method as set forth in claim 5, and including the steps of sensing the temperature of the cast strand as it leaves said chill, and automatically regulating the amount of air and Water in the mixture depending on the temperature sensed.

References Cited UNITED STATES PATENTS 2,651,821 9/1953 Chadwick, et al. 164283 2,782,473 2/1957 Brennan 164-82 2,946,100 7/1960 Baier et al. l64-283 X 3,098,269 7/1963 Baier 164283 3,358,743 12/1967 Adams 164-154 FOREIGN PATENTS 1,055,763 4/ 1959 Germany.

702,719 1/ 1954 Great Britain.

J. SPENCER OVERHOLSER, Primary Examiner R. SPENCER ANNEAR, Assistant Examiner U.S. Cl. X.R.

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