US3570586A

US3570586A - Machine with caterpillar mold for casting strips from nonferrous metals, especially aluminum and aluminum alloys

Info

Publication number: US3570586A
Application number: US758367A
Authority: US
Inventors: Wilhelm Friedrich Lauener
Original assignee: Prolizenz AG
Current assignee: Alcan Holdings Switzerland AG
Priority date: 1967-09-07
Filing date: 1968-09-09
Publication date: 1971-03-16
Anticipated expiration: 1988-03-16
Also published as: FR1582915A; SE344893B; IS1750A7; CH475811A; DE1758935B2; ES357874A1; NL6812516A; BE718794A; NO121009B; GB1203351A; DE1758935A1; IS990B6; AT287217B; NL157823B; DE1758935C3

Abstract

A caterpillar mold machine for casting strips of metal has mold blocks, guide and drive means for the mold blocks, and supporting and fastening means between the mold blocks and the guide and drive means connecting the mold blocks to the guide and drive means and having a low total heat conductivity.

Description

United States Patent Inventor Wilhelm Friedrich Lauener Langenhard, Switzerland Appl. No. 758,367 Filed Sept. 9, 1968 Patented Mar. 16, 1971 Assignee Prolizenz AG Bahnhofstrasse, Chur, Switzerland Priority Sept. 7, 1967 Switzerland 12505/67 MACHINE WITH CATERPILLAR MOLD FOR CASTING STRIPS FROM NONFERROUS METALS, ESPECIALLY ALUMINUM AND ALUMINUM ALLOYS 10 Claims, 10 Drawing Figs.

US. Cl 164/279, 164/283 Int. Cl 822d 11/06 Field of Search 164/87, 279, 283

References Cited UNITED STATES PATENTS 5/ 1968 Boehm 8/1914 Burkhardt 6/1932 Greene 6/1956 Brownstein FOREIGN PATENTS 8/ 1961 Great Britain Primary Examiner.l. Spencer Overholser Assistant Examiner-R. Spencer Annear Attorney-Emest F. Marmorek ABSTRACT: A caterpillar mold machine for casting strips of v metal has mold blocks, guide and drive means for the mold blocks, and supporting and fastening means between the mold blocks and the guide and drive means connecting the mold blocks to the guide and drive means and having a low total heat conductivity.

Patented March 16, 1971 3,570,586

4 Sheets-Sheet 1 Fig.1

Patented March 16, 197i 4 Sheets-Sheet 2 Fig. 2

Fig. 4

Patented March 16, 1971 4 Sheets-Sheet 5 olo] Fig. 6

Patented March 16, 1971 3,570,586

4 Sheets-Sheet 4 Fig. 8

Fig. 10

MACHENE WITH CATERPILLAR MOLD FOR CASTING STRWS FROM NONFERROUS METALS, ESPECTALLY ALUWUM AND ALUMENUM ALLOYS Reference is had to my copending application, Ser. No. 758,492, filed on Sept. 9, 1968.

The present invention relates to a machine with caterpillar mold for casting strips of nonferrous metals such as zinc, copper and their alloys, but especially of aluminum and aluminum alloys.

Several machines have been developed for the continuous casting of strips. In one machine the mold cavity is defined by a cooperating pair of endless chains of articulated mold blocks, and means are provided for revolving each of said chains about its own center. The chains are mounted so that over a part of their own length they engage with each other and define between them a mold cavity having walls which move continuously as the respective chains are revolved together at the same linear speed. Machines of this kind have been named machines with caterpillar mold." in one of the said machines the mold blocks of one row are not connected but are moved separately in a guide system and maintained in circuit in such a way that they meet again at the pouring end of the mold cavity to form, with the blocks of the other row, a closed mold.

In the book Handbuch des Stranggiessens by E. Herrman'n published in 1958 by the Aluminium-Verlag GmbH in Duesseldorf (Western Germany), the casting in caterpillar molds is described on pages 51 to 63.

According to many proposals a feed spout is provided through which, during operation, the melt flows continuously into the mold, closing back the mold at the inlet. The other end of the mold is closed at the beginning of the casting by a dummy bar and thereafter by the casting. It is possible to make a lateral closing of the mold by means of side dams.

It is well known, as mentioned above, to provide the mold blocks with coolant passageways for the purpose of cooling them continuously by means of a liquid coolant. It is also well known to dissipate the heat taken up by the mold blocks by immersing them into a liquid coolant or by spraying them with the coolant after they have left the mold. This cooling method offers the possibility of controlling the temperature of the mold blocks, that is to say, to maintain them at a temperature suitable for casting or solidifying the melt, whereas mold blocks which are constantly cooled by water circulation are relatively cold when they reach the inlet of the mold cavity.

All machines of the kind described above have the disadvantage that the mold blocks become unusable after a relatively short time because of constant changes of temperature, as they are distorted in consequence of the extremely high thermal stresses. Thereby the cooling faces (the inner walls) of the mold, named also mold walls, become uneven and the joints at the abutting faces of the successive mold blocks become loose; the strip which is being cast will obtain a nonuniform cross section, an uneven surface, and at the joints of the mold blocks will even have ledges and fins as the melt flows into the interstices.

Finally, a looseness between the mold blocks can also appear and the melt can flow out of the mold. There is also the problem of tightening the feeding spout in the mold as a reverse flow of the melt must be prevented. The greater the distortion of the mold blocks, the more difficult it is to achieve an adequate tightness.

The above-mentioned difficulties increased with the increased width of the strip. For this reason these machines have only been used up to now for the casting of relatively small strip widths and for metals and alloys with relatively low melting temperatures.

Among a great number of constructions only the machines of the Hunter-Douglas Corporation have been successful l-iandbuch des Stranggiessens, supra, pages 536/37 and 540/41) in the way of casting strips made of aluminum and aluminum alloys. I

The Hunter-Douglas machine is substantially characterized by the fact that coolant passages are formed in each of the cooling thus obtained renders possible to maintain the temperature of the mold blocks at a relatively low level so that they will be distorted only within tolerable limits.

The newest and widest machine of this kind is designed for.

the casting of 16 mm. thick and 533 mm. wide aluminum alloy strips. At the side with rotating coolant distributors the Hunter-Douglas machine is inaccessible and the cooling system is intricate. Moreover, such a machine cannot be designed for casting strips of much greater width, for instance of from 600 to 800 mm., as with such widths the mold blocks of the described construction would be distorted to an intolerable extent.

For an economic casting of good quality metal strips of greater width, for instance from 600 to 800 mm. or more, the following conditions must be substantially fulfilled:

1. The mold blocks must be accurately guided and without the influence of heat in the section where they form the mold. Deviation from the theoretically determined path may not be permitted to exceed, at most, a few tenths of 1 mm.

2. The surface of the mold which comes into contact with the strip must remein in the original shape over the whole zone of the temperature change, through which zone the mold blocks run cyclically. Differences should not exceed a few tenths of 1 mm.

3. The contact surfaces between the adjacent mold blocks must assure an efficient closing of the parting lines in order to obtain a strip with a substantially finless surface.

It is accordingly among the principal objects of the invention to provide a machine that avoids the aforesaid drawbacks of the prior art, and meets the preceding requirements.

Further objects and advantages of the invention will be set forth in part in the following specification and in part will be obvious therefrom without being specifically referred to, the same being realized and attained as pointed out in the claims hereof.

The present invention is based on strict adherence to the above-mentioned conditions and the avoidance, on the one hand, of any direct contact of the mold blocks with the guide and drive members, and on the other hand, that the mold blocks have such a shape and are held in such a manner that they may dilate freely but are notdistorted to any undue extent. ln this manner the accurate functioning of the guide and drive members is not impaired by thermal influences in the mold blocks and one obtains a substantially uniform thickness of the cast strip.

The machine with caterpillar mold according to the invention is generally characterized by the fact that the mold blocks are not in direct contact with the guide and drive members but are connected to them by supporting and fastening means of low heat conductivity in such a way that the heat transfer from the mold blocks to the guide and drive members by conduction is substantially precluded.

Through this measure the guide and drive system for the mold blocks is warmed up at most to body temperature, thus avoiding any substantial heat induced warping.

Moreover, the mold blocks are not substantially distorted.

In the accompanying drawings,

FIG. 1 is a fragmentary elevational view, partly in section, of a caterpillar mold machine inaccordance with the invention;

FIG. 2 is a large scale fragmentary plan view, partly in section, showing a mold block, its guide means and portions of its drive means, as well as the supporting and fastening means for the mold block connecting it to the guide and drive means;

FIG. 3 is a fragmentary side elevational view of some of the parts shown in H6. 2;

FIG. 4 is an elevational view, the mold blocks having been removed for simplicity of presentation;

FIG. 5 is a perspective view of a mold block;

FIG. 6 is an elevational view of the mold block of FIG. 5, showing the underside thereof in relation to the position of the mold block in FIG. 5;

FIG. 7 is a plan view of the mold block of FIG. 5;

FIG. 8 is a fragmentary end elevational view of a modified mold block;

FIG. 9 is a large scale fragmentary sectional view of the mold block of FIG. 8; and

FIG. 10 is a fragmentary plan view, partly in section, similar to FIG. 2, but embodying the modification of FIGS. 8 and 9.

The principle of the caterpillar casting machine according to FIG. 1 has been explained earlier herein. It should be noted, however, that the casting mold 100 is formed by a double row of mold halves 101, each of which forms two endless chains. At the region 103 where the casting metal is poured in,-the mold halves 101 which lie opposite one another come to lie next to one another and move in this position for a certain distance, along which the caterpillar mold halves 100 form. The casting metal flows from a trough 104 through a nozzle 105 into the closed casting mold 100. In this example, the solidified strip 106 emerges from the bottom of the casting mold 100 and is transported away by means of conveyor roller pairs 107 and 108. The explanatory remarks furnished in relation to FIGS. 2 to 7 and 8 to 10 disclose the characteristics of the machine which is designed in accordance with the present invention. I

For the successful casting with a machine of this type, it is a condition to prevent an appreciable thermal flow from the mold blocks to the supporting and revolving system. The necessity of this condition was not recognizedor undoubtedly was not realized-in former constructions. There are, for instance, caterpillar molds in which the mold blocks are connected to one another by tongues and driven by gears with which they are in direct contact.

In the caterpillar casting machine according to the invention the mold blocks are supported on guide members by one or more intermediate parts of small section. In this way the guide and drive members remain substantially cold.

In the following, some numerical dimensions are given, but it will be understood that they are included only for the purpose of exemplification and explanation, but not in any limiting sense.

FIG. 2 shows schematically the connection of a mold block 10 (FIG. 5) to a supporting guide member 11 made of steel. The mold block 10 rests on this guide member 11 by four supports, namely steel bolts 12, having a diameter of 10 mm. and a length of 45 mm. with hardened, rounded ends of a radius of 22.5 mm. which rest on backings 13 made of hardened steel. These backings 13 are sunk with one end in the mold block 10 and with the other end in the guide member 11.

The fastening is done by means of a steel bolt of mm. diameter, screwed into a bored hole 14 in the middle of the mold block 10. The said bolt 15 is tightly pulled against the guide member 11 by means of a nut 16 with interposed cup springs 17. I

The backings 13 are in the form of plane discs having a raised rim; normally the rounded ends of the steel bolts 12 come only into substantially punctiform contact with the plane part of the backings 13 so that the heat transmission is negligible. When the mold block 10 expands or contracts, and thus changes its length, the steel bolts 12 will assume a slightly sloping position; this change of position is, however, frictionless so that no strains occur in the mold block 10 and the guide member 11. The said slight sloping position of the steel bolts 12 does not effect any diminution of the distance between the mold block 10 and the guide member 111, as the ends of the steel bolts 12 are formed as sectors of a sphere, the radius of which (22.5 mm.) amounts to one-half of the bolt length (45 mm.).

The mold block 10 is maintained in the central position relative to the guide member ll by means of three

guide pieces

21, 22 and 23 screwed on to the guide member 11 and slide in

grooves

18, 19 and 20 (FIGS. 6 and 7), without being hindered in its change in length as a consequence of temperature changes. The guide piece 23 prevents any lateral displacement and the

guide pieces

21 and 22 prevent any displacement in the direction of movement of the mold. The axes of the

guide pieces

21, 22 and 23,.being in the same plane and in the prolonged direction of the grooves, intersect at a point H (FIG. 6), hereafter called fixed point which relative to the guide member 11 cannot be displaced in the parallel plane.

In the machine shown, the contact length of the

guide pieces

21, 22 and 23 with the walls of the

grooves

18, 19 and 20 amounts to about 35 mm. and the engagement depth to about 10 mm. Between the guide member 11 and the mold block 10 there is an interspace which very substantially prevents the heat flow from the mold block 10 to the guide member 11. Preferably a reflective metal sheet 24 (FIG. 2) for instance of stainless steel or anodized aluminum, is disposed between each mold block 10 and each guide member 11 and serves to reflect the thermal radiation. This metal sheet is provided with holes having preferably a clearance of one or more millimeters for the passage of the. supports 12, the steel bolt 15 and the

guide pieces

21, 22 and 23. The sheet 24 is pressed by means of four compression springs 25 made for instance from 2 mm. steel wire against bearing spacers 26 which determine the distance from the strip block 10.

Heat-insulating material may be used in place of the reflective metal sheet 24.

In the embodiment according to FIGS. 2 to 7 the mold blocks 10, according to the invention as explained hereinbefore, are not directly bound to the guide member 11 (the mold block 10 and the guide member 11 are not in actual contact), but by means of four supports 12 of 10 mm. diameter and the steel bolt 15 of 20 mm. diameter.

EXAMPLE As the surface 40 of the mold block 10 that is averted from the molding wall 36 (FIG. 5) measures 430x 188 mm., it has an area of 80840 mm? The supports I2 have altogether a section of 314 mm. but their heat conduction is practically negligible as the contact of both their ends is only punctiform. The steel bolt 15 has asection of 314 mm? If one rounds off this cipher in consideration of the section of the compression springs 25 to 350 mm? it appears that in the present embodiment the ratio of the surface 40 of the mold block 10 averted from the molding wall 36 to the section of the metallic connecting pieces is more than 200:1. The term metallic parts of relatively small section used for characterizing the machine according to the invention signifies that the total cross section area of the metallic connecting pieces (12, 15, 25) is 200 times smaller than the area of the connecting surface 40 of the mold block 10 which is parallel to the molding surface 36. In

other words, the total heat conductivity of the connecting pieces between the mold block 10 and the guide member 11 should, in the order of magnitude, be preferably 200 times smaller than the heat conductivity of the mold block 10.

Of course, one is interested in producing metallic connecting pieces such as the said supports 12 and the bolt 15 from metal of as small as possible heat-conductivity. For instance, according to FIG. 2, the connecting

pieces

12, 15 are made from ordinary steel. One could also use stainless chromenickel steel for instance which has a much lower heat conductivity than that of the ordinary steel which is generally used for screws, bolts and the like. For the described construction however, normal steel is quite adequate to maintain a substantially cold condition of the guide and drive members.

Instead of tiltable supports 12, one can also use yielding supports which securely connect the mold block to the guide member 11 and which, by change of length of the former, are only elasticmly defonned.-'

It is also possible to use rigid supports on which the moldblock it) is guided during changes in length of the mold block it). The sliding surfaces in this case are provided with a selflubricating glide lining, for instance of graphite or boron nitride; instead of a glide lining, small bearing rollers could be used.

The mold block can also be spaced from the guide member ll without any special supports; this can be done by means of a heat-insulated plate made of one or several pieces, on which plate the mold block 10 slides away from the fixed point l-I, during changes in length of the mold block it).

Moreover, it is possible to safeguardagainst displacement by means of securing the mold block it) with a bolt which passes through both this block 10 and the guide member 11. This bolt also serves to determine the fixed point and by one or more guide members 21 to 23, prevents distortion in the parallel plane.

The guide member ll is provided on both sides with a length of toothed rack 27 (FIG. 3) corresponding to the length E (FIG. 5) of the mold block 10. A driving gear 28 (FIG. 2) engages said toothed rack 27 on both sides in order to move the mold. At the ends of the axle 29, the centerline of which lies in the division plane of two mold blocks 10 (see FIG. 3), are guide rolls 30. The axle 29 is supported in bores 31 (FIG. 1). Opposite said axle 29 forked guides 32 (FIG. 3) are provided that grip the articulated pieces 33 of the neighboring guide member 11. The rolls 30 run in the high-precision machined guides 34 of a machine body 35 (FIG. 1). As the guide member ll remains cold, a very precise guidance is warranted independently from the temperature variations in the mold blocks 10.

When in contact with the melt, the mold blocks 10 become 1 unevenly heated, and consequently compression stresses appear in the warmer zones and tensile stresses in the colder ones. These stresses become relatively higher with a given temperature distribution, the more so when the warmer zones are prevented from dilating freely. The said stresses cause the distortion of the mold blocks 10 and moreover lead to fatigue phenomena and fissures in the mold surface which very disadvantageously influence the working life of the mold blocks 10. A further development of the machine according to the invention fulfills the second requirement when casting wide strips in the caterpillar mold.

In the case of the embodiment of the machine according to FIGS. 2 to 7, the mold blocks ill have such a thickness G F (see H6. 5) that even the greatest amount of heat supplied by the metal melt does not reach the rear surface 40 of the mold blocks 110, and during subsequent cooling of the molding wall 36, after leaving the casting section, becomes withdrawn through the said molding wall by the coolant. In other words, the mold blocks 10 of this embodiment are so constructed that during the casting operation the heat flow takes place substantially in the zone which is turned towards the molding wall 36, whereas there is only an insignificant variation in temperature in the zone adjacent to the surface 40 averted from the molding wall 36.

According to the last condition, the mold blocks 10 should comprise a warm and a cold zone. The warm zone 37 of the mold block it) acts as a part of the mold which makes contact with the melt or cast strip thereby taking over the heat transfer, while the purpose of the cold zone 33 is for the constant maintenance of the desired determined position so that the mold surface which is in contact with the cast strip during the operation remains always in accurate alignment and constantly retains its shape.

The warm zone 37 has such a volume that it can store the heat withdrawn from the melt or cast strip at least during one passage through the casting section. The thickness G F (FIG. 5) is suitably 8 to times, but preferably 10 to l5 times greater than the dimension of the mold cavity which determines the thickness of the strip to be cast, which is about 16 to 40 times, but preferably 20 to 30 times greater than the depth C of the mold recess, as the thickness of the strip to be cast is equal to twice the depth C.

On the return way to the entrance of the casting section, the warm zone of the mold blocks 10 becomes cooled to the desired temperature by dipping into, or spraying with, a liquid coolant.

The temperature of the mold block it) in greater depth remains substantiallyuninfluenced during the passage through the casting section and also through the cooling section as soon as a detennined operating temperature is attained. By limiting the main heat exchange in a part of the mold block It) turned towards the molding wall 36 and having a zone with an insignificant heat exchange on the other side 40, it is also possible to maintain the limit of distortion of the mold to a tolerable extent, even with greater mold widths, for instance for strips of 600 to 800 mm. width. This condition is important, not only with regard to the perfect operation of the machine but also when making strips which are as thick at the edges as they are in the middle.

In the following the zone of the mold block 10in which the substantial heat exchange. takes place is named the warm zone 37 and the other the cold zone" 38. The adequate size of the cold zone 38 insures the necessary stiffness. The part of the mold block 10 which lies under the layer participating in the heat exchange, that is to say, the cold zone 38, has the purpose of keeping the distortion of the mold block 10 within safe limits. If the cross section or the surface moment of inertia of the mold block it) is sufficiently large, it is possible to maintain the bending of the cooling face 36 (forming surface) within a few tenths of 1 mm. during the cycle of operation. If one has to cast a 600 mm. wide aluminum strip, it results in a mold block thickness D (FIG. 5) of 250 mm.; only one-fifth of the mass of the mold block 10 (warm zone 37) participates in the heat transfer, the other four-fifths having the purpose of stiffening the warm zone. Deflection of the mold block 10, which always takes place, can be largely compensated by a suitable machining of the cooling face 36 (molding wall).

EXAMPLE On the mold block 10, shown as an example in FIG. 5, the width A is 600 mm. and the width B of the molding wall recess 36 is 550 mm. As the mold block 10 is intended for the casting of 18 mm,thick strips from aluminum or aluminum alloys, the depth C of its recess 36 (which is the molding wall) is about 9 mm. The mold block 10 has a thickness D of 255 mm. and a length E of 188 mm. in the casting direction. The ratio of the thickness D to the length E is therefore 255/188 1.36 the mold block 10 is thicker than it is long.

The casting machine (see FIG. 1 comprises 24 mold blocks 10 in each caterpillar track. On each side lie six mold blocks 10 which are either pressed against or lying over each other to form the mold; thus the mold has a length of 6 X 188 mm. l 128 mm. During the traveling of the mold blocks it] on the track where they fonn the molding cavity, that is to say the mold itself in cooperation with the opposite mold blocks, the heat flows perpendicularly into the warm zone 37 and reaches approximately the thermal limit indicated by the broken line 39. After having left the casting zone the mold blocks 10 can EXAMPLE With a casting speed of 2.5 m./min. (casting metal: aluminum) the depth F of the thermal limit 39 amounts to about 50 to 60 mm. and the thickness G of the cold zone (supporting part) to about 205 to mm. On the separating mold blocks it) the following temperatures were measured:

Middle of the forming wall 36 210 C.

Edge of the forming wall (still in the depth of the recess) Thermal limit 39 (middle) 100 C.

Thermal limit 39 at the sidewalls of the mold block 10 80 C. After cooling by water spray the following average temperatures were measured:

Middle of forming wall 36 l l C. Edge of the forming wall 36 (still in the depth of the recess) Middle of the thermal limit 39 105 C.

Thermal limit of the sidewalls of the mold block 60 Should the ratio of the thickness G to the depth F (that is to say, of the supporting part to the warm part) be too small, the temperature variations in the warm part (warm zone) would cause a constant distortion of the latter and it would not be possible to cast wide strips with the necessary accurate section. The mold block must therefore comprise a supporting part 38 (cold zone) which is mechanically very resistant and which, in equilibrium, does not undergo any substantial variations during the casting operation and can also hold the warm part 37 so strongly that the latter cannot undergo any undue distortion during the casting operation. In the described example the cold part 38 (cold zone) is about four times as thick as the warm part 37 (warm zone).

EXAMPLE With a casting speed of 2.5 m./min. (casting metal: aluminum) the following average temperatures were measured on the mold blocks 10 leaving the casting section:

Middle of the face 40 70 C.

Mold wall 41 in the neighborhood of the corner 42 60 to At the thermal limit the temperatures were, as above, 80 to 100 C. After cooling with water sprays, the following temperatures were measured at the pouring side of the mold blocks 10:

Middle of the face 40 60 to 70 C.

Mold wall 41, in the neighborhood of the corner 42 60 to One can see that the temperature does not substantially vary in the cold part. As the mold blocks 10 are made preferably of steel which has a low coefficient of thermal expansion, it is possible, by choice of a sufficient thickness, to give them a stiffness which enables the satisfactory casting of for instance 600 mm. to 800 mm. wide aluminum strips.

The embodiment according to FIGS. 8 to 10 is especially adapted for the casting of very wide strips, for instance of 700 to 1,500 mm. or more. In this case, it is advantageous to use mold blocks 43 composed of plates 44 instead of the massive blocks 10, the plates being disposed perpendicularly to and in the longitudinal direction of the casting.

The plates 44 which compose the mold block 43 are pressed together by means of two or more tie rods 45. In this way an elastic body of relatively small resistance to bending is formed, said body being connected to the guide member 46 in the same way as the massive mold blocks 10 and by this means is kept in position. With composed mold blocks 42 it is necessary to make the guide member 46 much stronger than is necessary with massive mold blocks 10.

The stiffening cold part 38 of the massive mold blocks 10 would be inefficient in mold blocks 43 composed of plates 44, so that the part 38 is dispensed with. Moreover, it would be unsuitable to choose the same thickness D as with the massive mold blocks 10. The total thickness of the mold blocks 43 composed of plates 44 which is most suitable for the purpose is for instance I00 to 150 mm. but may exceed or fall below these sizes. The stiffness provided by the cold part 38 with massive mold blocks 10 must be guaranteed here in another way, for instance by increasing the number of supports 12 and steel bolts'15 and by making the guide member 46 stronger,

for instance up to the two or threefold moment of inertia, by strengthening the guide member 46 by means of a steel block 47 (FIG. 10).

The steel block 47 has

grooves

48, 49 on the side which is turned towards the composed mold block 43, said grooves corresponding to the

grooves

18, 19 and 20 of the mold block 10 (FIG. 6) and having a similar function. The groove 48 corresponds to the previous groove 18 and the groove 49 to the previous groove 20; the groove corresponding to the groove 19 is not visible on FIG. 10. The composed mold block 43 (FIG. 10) has

grooves

50, 51 similar to the massive mold block 10, (FIGS. 6 and 7); the groove 50 corresponds to the previous groove 18, and the groove 51 to the groove 20; the groove corresponding to the groove 19 is not visible in FIG. 10.

There are also

grooves

52, 53 and 54 on the side of the steel block 47 turned towards the guide member 46, said

grooves

52, 53, 54 being disposed in the same manner as the previous grooves l8, l9 and 20 of FIG. 6; for guiding, the

grooves

52, 53 and 54 cooperate with

wedges

55, 56 and 57 which are inserted in

grooves

58, 59 and 60.

The end plates 61 of a composed mold block 43 are made especially strong. Their thickness is preferably from 40 mm. to 80 mm.; their stiffness can be further increased by a rib in order to prevent any undue distortion which may occur during operation in consequence of the nonuniform heating.

If the plates 44 are made from metal sheet of a few millimeters thickness, for instance of from 2 to 5 mm., certain though irregular statistically distributed interstices of a few hundredths of 1 mm. will normally occur in consequence of the natural unevenness of the plates. These interstices allow an unhindered dilation of the plates 44 in the direction of the strip width when the temperature rises.

The manner described in which the mold block is connected to the guide member by the means shown in FIGS. 2, 4, 6 and 7, makes it possible to maintain without great force the cooling face 62 (mold wall) constantly in the desired position and substantially even by means of the guide member 46.

One may also use thicker plates 44 which are advantageously spaced from each other by intermediate layers 63 of heat-resistant material of permanent shape (FIG. 9). These layers 63 may be disposed between all individual plates 44 or between several of them. In order to allow the dilation of the plates in the direction of the strip width, the intermediate layers 63 should reach at most a distance of 20 mm. from the cooling face 62 (mold wall). The thickness d of the intermediate layer 63 in millimeters should be greater than onehalf of the value of the product calculated by multiplying the coefficient of dilation a of the metallic material coming into contact with the melt by the average distance b of two neighboring intermediate layers in millimeters and by the melting temperature T expressed in centigrades, of the metal to becast:

a-b-T d 2 EXAMPLE steel plates 44, the thickness d of the intermediate layers 63 will be at least 0.1 1 mm., for example:

d 2 =0.115 mm.

One may also dispose plates 44 of a different thickness in one and the same mold block 43; this may for instance be advantageous for the connection of the mold block 43 to the guide member 46. The casting capacity depends on the heat conductivity of the mold material. For instance, one may expect about a six times as great a casting capacity when using copper molds instead of steel molds. Because of the relatively great weight of the mold blocks, the use of copper can only be considered in exceptional cases, as copper is very expensive as compared to steel.

If the mold block 43 is made from thin plates 44 of for instance from 2 to 5 mm. thickness, one can dispose at intervals copper or aluminum plates 44 of good heat conductivity. In this way the heat withdrawal may be improved and the casting capacity increased accordingly. in order to warrant a uniform heat withdrawal over the width of the strip in the course of casting, the plates 44 made from different materials must, to be of advantage, amount to less than 40 percent of the thickness of the strip to be cast. :The thickness of the plates made from different materials need not necessarily be the same; for instance, one may dispose alternatively copper plates 44 of 2 mm. thickness and steel plates 44 of 5 mm. thickness or vice versa. The thicknesses of the plates 44 are chosen according to the desired heat conduction of the mold block 43.

The mold blocks or 43 are cooled by spraying a cooling liquid against their

molding face

36 or 62 averted from the cast strip in a case where reduced air pressure is maintained, the rarefied pressure being such that the outflow of cooling liquid out of the case between the same and the mold blocks is prevented by the inflow of air into the case.

For this purpose one utilizes a case opening towards and reaching, within a clearance of several tenths of one millimeter, the mold blocks to be cooled. The said case contains spraying nozzles directed to the

molding walls

36 or 62 and is connected to a device producing the rarefied pressure.

It has proved advantageous to add an emulsion of oil in water to the cooling liquid. A detailed description of the cooling device is given in my copending Pat. application, Ser. No. 758,492, filed Sept. 9, 1968 under the title Method for cooling the mold blocks of a casting machine with caterpillar mold and device for carrying out the method.

I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

I claim:

1. A caterpillar mold machine for casting strips of aluminum and aluminum alloys, comprising a series of mold blocks which interact to form a mold for casting strips, guide means and drive means for said mold blocks free from direct contact with said mold blocks for heat transfer restraint, and supportand fastening means are metallic and have a total heat transfer cross section area the ratio of which relative to the area of the face of the mold blocks averted from the molding wall is less than 1:200.

4. A machine according to claim 1, and a reflecting metallic sheet disposed between the mold blocks and the guide and drive means.

5. A machine according to claim 1, each mold block having a molding wall, said block having a recess in said molding wall to accommodate said casting strips, said block having a thickness measured from the interior of said recess to the rear surface of said block which equals about 16 to 40 times the depth of said recess, said mold block being arranged sufficiently voluminous that in operation a heat flow takes lace substantially in the zone which Is turned towards the mo ding wall, the part adjacent the rear averted from the molding wall being subject only to anegligible temperature change and sufficiently thick so that it maintains the other zone of the mold blocks free from appreciable thermal expansion or distortion.

6. A machine according to claim 1, wherein each mold block comprises plates, and the guide means includes guide members having reinforcing steel blocks maintaining the mold blocks in alignment over said supporting and fastening means.

7. A machine according to claim 6, and intermediate layers of heat insulating material of permanent shape disposed between said plates in each mold block.

8. A machine according to claim 7, wherein the intermediate layers 63 reach at most a distance of 20 mm. from the mold wall.

9. A machine according to claim 1, said guide means including guide members, and guide pieces disposed in grooves in a sliding manner, maintaining the mold blocks during operation in a predetermined central position in relation to the corresponding guide members irrespective of any change of length due to any change of temperature.

10. A machine according to claim 6, wherein said steel blocks have first grooves on the side turned towards the mold block and guide pieces are disposedin said first grooves in .sliding manner and maintain, during operation, the mold blocks in a predetermined central position in relation to the corresponding guide member, second grooves, and wedges inserted in said second grooves.

Claims

1. A caterpillar mold machine for casting strips of aluminum and aluminum alloys, comprising a series of mold blocks which interact to form a mold for casting strips, guide means and drive means for said mold blocks free from direct contact with said mold blocks for heat transfer restraint, and supporting and fastening means disposed between said mold blocks and said guide and drive means forming the only heat transfer connection between said mold blocks and said guide and drive means and having a low total heat conductivity.

2. A machine according to claim 1, the ratio of the total heat conductivity of the supporting and fastening means of each mold block relative to the heat conductivity of each mold block being not more than 1:200.

3. A machine according to claim 1, wherein the supporting and fastening means are metallic and have a total heat transfer cross section area the ratio of which relative to the area of the face of the mold blocks averted from the molding wall is less than 1: 200.

5. A machine according to claim 1, each mold block having a molding wall, said block having a recess in said molding wall to accommodate said casting strips, said block having a thickness measured from the interior of said recess to the rear surface of said block which equals about 16 to 40 times the depth of said recess, said mold block being arranged sufficiently voluminous that in operation a heat flow takes place substantially in the zone which is turned towards the molding wall, the part adjacent the rear averted from the molding wall being subject only to a negligible temperature change and sufficiently thick so that it maintains the other zone of the mold blocks free from appreciable thermal expansion or distortion.

10. A machine according to claim 6, wherein said steel blocks have first grooves on the side turned towards the mold block and guide pieces are disposed in said first grooves in sliding manner and maintain, during operation, the mold blocks in a predetermined central position in relation to the corresponding guide member, second grooves, and wedges inserted in said second grooves.