US3412784A

US3412784A - A mold for continuous casting of flat bars having an oval graphical insert surrounded by a cooled rectangular jacket

Info

Publication number: US3412784A
Application number: US521649A
Authority: US
Inventors: Wieland Hans
Original assignee: Wieland Werke AG
Current assignee: Wieland Werke AG
Priority date: 1965-06-18
Filing date: 1966-01-19
Publication date: 1968-11-26
Anticipated expiration: 1985-11-26
Also published as: BE674023A; DE1265924B; AT258496B; GB1086229A

Description

Nov. 26, 1968 H. W|ELAND 3,412,784

MOLD FOR CCNTINUOUS CASTING OF FLAT BARS HAVING AN OVAL GRAPHCAL INSERT SURROUNDED BY A COOLED RECTANC'ULR JACKET Filed Jan. 19. 1966 4 Sheets-Sheet l bonoraoomoovooo oaoeoooooo INVENTOR HA Ns wuz LAND.

,drrroRNrsY Nov. 26, 1968 MOLD FOR CONTINUOUS CASTING OF FLAT BARS HAVING AN OVAL GRAPHICAL INSERT SURROUNDED BY A COOLED RECTANGULAR JACKET Filed Jan. 19, 1966 4 Sheets-Sheet 2 lililiriiliill'l O a O o o o 0 INVENTOR HANS WIE LAND.

ArroRNEY Nov. 26, 1968 HWIELAND 3,412,784

MOLD FOR CONTINUOUS CASTING OF FLAT BARS HAVING AN OVAL GRAPHICAL INSERT SURROUNDED BY A COOLED RECTANGULAR JACKET ned Jan 19 196e 4 sheets-sheet s INVENTOR -HA NS WIE LAND.

'.rroRNEY Nov. 26, 1968 H. WIELAND 3,412,784

MOLD FOR coNTINuoUs CASTING oF FLAT BARS HAVING AN ovAIJ GRAPHICAL INSERT SURROUNDED BY A COOLED RECTANGULAR JACKET Filed Jan. 19, 1966 4 Sht5-sh6t 4 Fig. n

INVENT OR HA NS WIE LAND.

ORNEY United States Patent O M 14 claims. (ci. 164-283) ABSTRACT OF THE DISCLOSURE A mold for continuously casting fiat bars or plates of metal of rectangular cross-section having a ratio between the transverse length and width greater than 1:1, comprising a graphite insert having open opposite ends and a substantially oval outer peripheral surface and surrounding and defining a mold cavity of an oblong crosssection and a cooled metallic jacket surrounding said graphite insert and engaging therewith under tangential tension so as to exert compressive forces in radial directions upon said graphite insert at all points of its peripheral surface.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates to a mold for continuously casting fiat bars or plates of metal, especially copper.

Description of the prior art For casting copper in a continuous operation, it is well known to employ a mold which consists of a cooled outer metallic jacket and an insert within this jacket which is made of graphite and defines the mold cavity. In order to prevent burning and gradual oxidation of the graphite insert and a resulting roughening and loss of the lubricating effect of its surfaces, it is necessary when using such a mold to insure that the parts of the graphite insert which come in contact with the atmospheric air will not be heated to a temperature higher than approximately 550 C. When casting copper which contains oxygen, this temperature should also not be exceeded at those parts of the graphite insert which only come in contact with the molten metal. In both cases it is therefore necessary that at least the mentioned parts of the graphite insert be cooled as effectively as possible. For attaining the highest possible casting output it is essential that the heat of the graphite insert which it receives from the solidifying copper be conducted from this insert as quickly as possible via the metallic jacket to the cooling medium. This is attained in the known types of molds which are provided with circular mold cavities by a shrink or press fit between the graphite insert and the metallic jacket. If, however, the mold is to be designed for casting bars of a rectangular cross section in which the ratio between the transverse length and width of the bar is considerably higher than 1:1, it is very difficult to maintain the required contact between the graphite insert and the cooled metallic jacket which is necessary for dissipating the heat from the graphite insert as quickly as possible. This is due to the fact that by conventional means it is impossible to attain such a tight engagement between the. fiat surfaces of such a graphite insert and the surrounding metallic jacket as may be attained by a shink or press lit if these surfaces have a circular cross section. Even though it may be possible to attain a good contact between such flat 3,412,784 Patented Nov. 26, 1968 surfaces when they are in a cold condition, such a contact can no longer be assured during the casting operation because of unavoidable thermal stresses which then occur. Thermally insulating gaps will then be formed between the graphite insert and the metallic jacket with the result that the fiow of heat from one to the other will be interrupted and that because of the insufiicient cooling action the casting output of the mold will be reduced.

In order to overcome this deficiency, it has already been proposed to make the walls of the graphite insert so thin that they will bend outwardly in the direction toward the cooled metallic jacket under the hydrostatic pressure of the liquid metal within the mold. Although such a construction insures that the heat will at all times be dissipated very quickly from the graphite insert so that a high casting speed may be attained, it is unavoidable that the thin plate-shaped walls of the graphite insert will very soon be worn off and must then be replaced by a new set. Since they have to be so thin, these walls are also very fragile and their replacement can therefore be effected only with great caution and difliculty. Consequently, the advantage of the high casting speed which is attained by employing such a graphite insert is nullified by the expense of the frequent repairs which have to be made and by the length of time of the interruptions in the casting operation which are caused by these repairs.

Summary of the invention The principal objects of the present invention are to provide a mold which is designed so as to eliminate the above-mentioned disadvantages and is provided with a graphite insert with thick walls, and which permits bars or plates of metal, especially copper, to be cast at a high rate of speed and to be uniformly cooled along their entire cross-sectional area without thereby increasing the length of time of the casting operation and without impairing the properties and surface quality of the cast metal.

For attaining these and other objects, the invention consists in the novel design and construction of the graphite insert, of the cooled metallic jacket surrounding this insert, and of the outer cooling jacket of the mold, and in the particular arrangement of these elements and their particular combination with each other.

According to the invention, the graphite insert which defines and forms an oblong, substantially rectangular mold cavity is provided with an outer peripheral surface of an oval shape on which the cooled metallic jacket is mounted under tangential tension so as to exert compressive forces in radial directions upon the graphite insert at all points of its peripheral surface. This construction insures that all points of the outer surface of the graphite insert will be at all times in intimate contact with the cooled metallic jacket so that the best possible heat transfer will be attained at all times from the graphite insert via the metallic jacket to the cooling medium which surrounds the entire mold.

A preferred structural feature of the invention consists in producing the cooled metallic jacket of a metal band which is spirally wound under tension around the peripheral surface of the graphite insert and the adjacent windings of which are tightly connected to each other, preferably by soldering.

If the mold cavity which is defined and formed by the graphite insert and extends in the casting direction 'has a substantially rectangular oblong cross-sectional shape, it is another advantageous feature of the invention to make the outer surface of the graphite insert which engages wit'h the metallic jacket of an elliptical cross section. This outer surface may also form an ellipsoidal curve which is preferably composed of two pairs of arcs in which the opposite arcs of each pair are congruent.

In any event, the curved parts of the outer surface of the graphite insert which extend along the wider sides of the mold have a weak curvature, while those which extend along the lnarnower sides of the mold have a sharp curvature.

Although the graphite insert may consist of a single piece of material, it is more preferably made of several parts, for example four parts, which interengage with each other, preferably by means of Z-shaped butt joints. rIhcse parts of the graphite insert are held together by being tightly wrapped by the metal band, that is, by winding the band under tension around the assembled insert. The start and the end of the metal band are then secured to the cover and the bottom of the cooling jacket.

Since the metal jacket is cooled during the casting operation, while the graphite insert is heated, the latter expands to a greater extent in the direction toward the metal jacket and thereby exerts an even greater pressure against this jacket than it does in the cold condition, so that the heat transfer will be further improved.

Brief description of the drawings The features and advantages of the present invention will become further apparent from the following detailed description which is to be read with reference to the accompanying drawings, in which- FIGURE l shows a cross section which is taken along the line I-I of FIGURE 2;

FIGURE 2 shows a cross section which is taken along the line II-II of FIGURE 1;

FIGURE 3 shows a cross section which is taken along the line III-III of FIGURE l;

FIGURE 4 shows an enlarged cross section which is taken along the line IV-IV of FIGURE 3; while FIGURE 5 shows a development of the inner wall 25 of the water jacket and illustrates one quarter of the peripheral surface of this wall which is located in the left upper part of FIGURE 3.

Description of the preferred embodiment As illustrated in the drawings, the graphite insert according to the invention preferably consists of four separate parts, namely, the two longitudinal plates 1 and the two transverse plates 2 which interengage with each other by means of Z-shaped contact surfaces 19 in order to prevent them from yielding or shifting inwardly when subjected to external pressure. The outer peripheral surface of the graphite insert 1, 2 has an elliptical or at least substantially elliptical shape and it is enclosed by a coil 3 which consists of a copper band and is wound thereon under tension and thus forms a cooled metal jacket which engages upon the outer surface of the graphite insert and very effectively dissipates the heat of the latter and thus also the heat of the metal which is poured into this insert.

The `graphite insert -1, 2 together with the metallic cooling jacket 3 is clamped within a frame which consists of a lower supporting ring 8 and an upper supporting ring 4 which are connected to each other by spacer bolts 9 which extend through bores in the graphite insert and are screwed by screw threads 22 into the lower supporting ring 8. The upper ends of spacer bolts 9 carry nuts 10 which are tightened so as to clamp the two supporting rings 4 and 8 and the intermediate graphite insert 1, 2 tightly together. The graphite insert and the two supporting rings 4 and 8 are separated by

plates

6 and 7 to which the upper and Ilower ends of the copper coil 3 are soldered at a and 15b, respectively.

The upper supporting ring 4 is secured to an annular water jacket which lhas an outer wall S and an inner wall and is tightly closed at its lower end by a ring 23 and at its upper end by a ring 24. Between this ring 24 and the upper supporting ring 4 a gasket ring 14 is placed and the two rings 4 and 24 are secured to each other by screws 13. The inner wall 25 of the water jacket Cil which is spaced from the outer wall tof the graphite insert and from the cooling jacket 3 thereon is provided with spray Iholes 11. Within the central part of the wider sides of wall 25 these spray holes 11 are spaced at smaller distances from each other than those which are provided within the narrower ends of wall 25. For circulating the cooling water through the water jacket S, 25, its lower end is provided at diagonally opposite points with pipe sockets 17. Underneath the graphite insert 1, 2 an annular pipe 12 is secured by arms 27 to the lower supporting ring 23. This pipe 12 is supplied through a pipe 18 with water 'under pressure which is sprayed through inwardly directed holes 21 in the wall of pipe 12 directly upon the copper bar 28 as it emerges from the mold for the purpose of further cooling the metal.

The graphite insert 1, 2 which is Ilimited at its upper and lower ends by the supporting rings 4 and 8 is inserted from above into the

water jacket

5, 23, 24, 25 and it is secured to the upper supporting ring 4 by the screws 13.

For producing the mold, the upper side of the first winding of the copper band 3 is tapered in its longitudinal direction, as indicated in FIGURE 4, and soldered at 15a to the upper supporting plate 7. The copper band is then wound under tension around the outer surface of the graphite insert l, 2 and the joints 20 between the adjacent windings are closed by soldering. The required tension of the coil windings is attained by passing the copper band 3 during the winding operation through a friction brake. After the graphite insert 1, 2 Ihas been completely covered by the copper band 3, the lower end of the latter is soldered at 15b to the lower supporting plate `6, as shown in FIGURE l, and the excessive part is cut olf flush with the lower edge of the soldered joint 15b.

The cooling water passes through the pipes 17 into the

water jacket

5, 23, 24, 25 and is sprayed from the latter under pressure through the spray holes 11 upon the copperband jacket 3 around the graphite insert 1, 2 and it then flows downwardly along this jacket 3.

The mold according to the invention may be employed for producing copper plates with plane smooth outer surfaces. The rate of lpouring and thus also the casting output of the mold may be very high without danger that the graphite insert might become overheated which will therefore remain fully @operative for la long time. Even if lthe same graphite insert is employed for casting large quantities of copper, the louter dimensions of the oontinuously cast product will correspond much more ac-y curately and consistently with the desired dimensions than this was attainable with any molds according to prior constructions. This is due to the fact that the graphite insert is uniformly cooled and that its temperature remains relatively low because of the good heat dissipation.

Although my invention 'has been illustrated and described with reference to the preferred embodiment there. of, I wish to have it understood that it is in no way limited to the details of such embodiment but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, what I claim 1. A mold for continuously casting flat bars or plates of metal of rectangular cross-section having :a ratio between the transverse length and width greater than 1:1 comprising a `graphite insert having open opposite ends and a substantially oval outer peripheral surface and surrounding and defining a mold cavity having a rectangular cross-section with a length to width ratio :substantially greater than 1:1 and a cooled metalic jacket surrounding said graphite insert and engaging therewith under tangenrtial tension so as to exert compressive forces in radial directions upon said graphite insert at all points of its peripheral surface.

2. A mold as defined in claim 1, in which said metallic jacket consists of a metal band which is wound under tension around said peripheral surface of said graphite insert, the edges of the adjacent windings of said band being tightly secured to each other.

3. A mold las defined in claim 2, in which the edges of said adjacent windings of said metal band are soldered to eao'h other.

4. A mold as defined in claim 1, in which the peripheral surface of said graphite insert has Ea substantially elliptical cross section.

S. A mold as defined in claim 1, in which the peripheral surface of said graphite insert forms a curve of an ellipsodial shape which is composed of two pairs of arcs of different diameters, the two :arcs of eaclh pair being congruent and disposed opposite to each other.

6. A mold as defined in claim 1, in which said graphite insert consists of a plurality 'of individual parts adjacent to and interengaging with each other.

7. A mold as defined in claim 6, in which said adjacent parts of :said graphite insert interengage with each other by means of substantially Z-shaped butt joints.

8. A mold as defined in claim 2, further comprising upper and lower supporting plates, means for securing said rsupporting plates to the upper land lower ends of said graphite insert, and means for securing the upper and lower ends of said metal band to said supporting plates.

9. A mold as defined in claim 8, in which said means for securing said supporting plates comprise spacer bolts extending continuously through said upper and lower supporting plates and clamping said plates upon the upper and lower ends of said graphite insert.

10. A mold as dened in claim 8, in which said means for securing said supporting plates comprise spacer bolts extending continuously through bores in said graphite insert and in Said upper and lower supporting plates and clamping said plates and said graphite insert together.

11. A mold as defined in claim 1, further comprising a Water jacket surrounding said metallic jacket on said graphite insert, the inner wlall of said water jacket being spaced from said metallic jacket and having spray holes therein for spraying cooling water upon said metallic jacket, and -means for supplying cooling water to said water jacket.

12. A mold as defined in claim 11, in which said graphite insert together with said metallic jacket thereon is removably inserted into said water jacket, and means for removably securing said graphite insert together with said metallic jacket to said wlater jacket.

13. A 'mold as defined in claim 11, in wlhich said spray holes in said inner wall of said water jacket are spaced at different distances from each other so as to spray a larger quantity of cooling water upon the wider sides of said metallic jacket than upon the narrower sides thereof.

14. A mold as defined in claim 1, further comprising la pipe underneath t-he lower open end of said graphite insert and having inwardly directed spray holes for spraying cooling water upon `all sides of the metal bar or plate emerging from said insert, and means for supplying cooling water to said pipe.

References Cited UNITED STATES PATENTS 2,789,328 4/1957 Ackermann et ral. 164-283 3,059,295 10/1962 Vosskuehler 164-283 3,098,269 7/1963 Baier 164-283 3,237,252 3/1966 Ratcliffe 164-283 XR 3,304,585 2/ 1967 Marclhlik 249-134 XR FOREIGN PATENTS 528,939 8/1956 Canada.

I. SPENCER OVERHOLSER, Primary Examiner.

R. S. ANNEAR, Assistant Examiner.