NO811916L - APPARATUS AND PROCEDURE FOR CONTINUOUS CASTING OF METAL STRAPS - Google Patents

Abstract

An oscillating cooled mold assembly for the continuous high-speed casting of metallic strands, (12) especially upcasting strands of copper alloys such as brass, has a hollow die (112) in fluid communication with a melt (14) typically held in a casting furnace (16). coolerbody surrounds the die in a tight-fitting relationship to form a solidification front in the melt as it advances through the casting zone of the die. During assembly, the die is preferably slip fit in the coolerbody (103). A shoulder on the die engages a lower face of the coolerbody (103) and, together with a small irregularity on the upper coolerbody wall, prevents any axial movement of the die before it thermally expands against the coolerbody. An insulating member (118) located between the die and the coolerbody and below the solidification front fixes the location of the front within a dimensionally uniform area of the die. The insulating member is preferably a ring of a material such as casting silica that has a low coefficient of thermal expansion, a low porosity, and is highly resistant to thermal shock. The insulating member (118) also preferably creates a steep longitudinal temperature gradient at its upper end to promote a high cooling rate over a relatively short casting zone. An insulating hat encloses the coolerbody, allowing it to be immersed in the melt and preferably deeply immersed to a level above the casting zone The strand or rod formed from the solidified melt is pulled through the die while the mold oscillates in a direction substantially parallel to the direction of travel of the rod.

Description

The present invention relates to the casting of metal strands in general and, more specifically, to a system where a cooled, oscillating mold device is used for continuous high-speed casting of strands of copper and copper alloys containing brass.

It is in itself a well-known process to cast unlimited lengths of metal strands from a molten mass, whereby the molten mass is drawn through a cooled mold. The mold usually comprises a casting element of a refractory material, e.g. graphite which is cooled by means of an enveloping water jacket. US patent 3,354,936 thus mentions a cooled casting device which is introduced sealed into the bottom part of a molten mass container, for casting large ingots. Under the influence of gravity, the molten mass is advanced through the mould. During casting, however, there is a risk that the molten mass "breaks out", and that the molten mass container must be emptied or tilted, in order to repair or replace the mold or the casting element.

Horizontal casting through a cooled mold has also been attempted. In addition to the difficulties associated with breakouts and replacement, gravity can cause uneven hardening resulting in a casting of non-uniform cross-section or of inferior surface quality.

Different devices for casting have also been used. Previous attempts are discussed in US Patents 2,553,921 and 2,171,132. The former describes a water-cooled, metallic "casting pipe" with an external ceramic coating which is immersed in a molten mass. in practice it has proved impossible to find a usable metal for the casting tube, the castings are subjected to uneven cooling and condensed metal vapors are deposited in a gap that forms between the casting tube and the outer coating due to the materials' different thermal expansion coefficients. According to the latter patent document, a water-cooled "mantle" is also used, but this is mounted above the molten mass, so that this must be sucked up to the mantle by vacuum action. A refractory, coaxial extension of the mantle is introduced into the melt. This coaxial extension is necessary to prevent "mushroom formation", i.e. formation of a massive metal mass of larger diameter than the cooled mantle. In the same way as with the device according to US patent 2,553,921, in gaps that occur due to thermal expansion, in this case between the mantle and the extension, condensed metal vapors can collect, causing poor surface quality or interruptions in the casting.

Newer devices and methods for casting are known from US patent document 3 746 0 77 and 3 872 913. According to the latter document, the problems in connection with heat expansion will be avoided by using a "nozzle" where only the tip is placed in the molten mass. The upper end of the nozzle is enclosed by a water-cooled jacket. As the surface of the molten mass is located below the cooling zone, a vacuum chamber will be required at the upper end of the nozzle, so that the molten mass can be sucked up to the cooling zone. However, the presence of such a vacuum chamber will limit the string drawing speed and also require sealing.

According to the above-mentioned US patent document 3,746,077, a cooling jacket and part of an encapsulated nozzle are immersed in the molten mass,

and the vacuum chamber thereby becomes redundant. The immersion depth is sufficient for the molten mass to be advanced to the hardening zone, without the device being immersed deeply. Both the mantle and the interface between mantle and nozzle are protected from the molten mass by means of an enveloping, insulating outer layer. The lower end of the outer layer rests against the lower outer surface of the nozzle and thereby blocks a direct flow of molten mass to the coolant jacket.

The above systems can generally be said to be of the "closed" mold type, in that the liquid metal communicates directly with the hardening front. The cooled mold will typically be fed from an adjacent container which is filled with molten mass. In contrast, in an "open" mold system, the melt will be fed directly through a supply pipe to a mold in which it is cooled very rapidly. Open mold systems are usually used when casting large ingots of steel and sometimes aluminium, copper or brass. However, open mold casting is not used in the production of products with a small cross-section,

because it is very difficult to control the level of the liquid mass and consequently of the location zone of the curing front.

A difficulty that arises in connection with closed mold casting is due to the heat expansion of the mold tray channel between the starting point of the hardening front and the point of complete hardening, which is called the "trumpet mouth". This condition results in the formation of expansions in the casting cross-section which are wedged against a narrower part of the casting element. The wedged section can break and form an immovable "skull". Such shells can cause the string to be interrupted, or they can be deposited on the casting element and cause surface defects on the castings. It is therefore important that the casting channel maintains a uniform dimension in the casting zone. According to the aforementioned patents 3,872,913 and 3,746,077, these problems are brought under control due to a relatively weak, vertical temperature rise along the nozzle, partly as a result of a moderate cooling rate, to create a largely flat curing front. With such moderate temperature curves, acceptable quality castings can only be produced at a relatively low speed, typically between 12 and 102 cm per my.

Condensation of metal vapors represents another, significant problem when casting through a cooled mold. Condensation is particularly troublesome when casting elements of base metal, zinc or other alloys that boil at temperatures below the alloy's melting point. Zinc vapor will easily penetrate both the materials that are usually used for the production of casting elements and the usual insulating materials, and can condense to liquid in critical zones. Liquid zinc that is deposited on the mold near the hardening front can boil at the outer surface of the casting and thereby cause a surface defect in the form of blistering. Because of these difficulties, the existing casting apparatus and techniques are not suitable for commercial high speed production of good quality brass strings.

The way in which the casting is pulled through the cooled mold also represents an important aspect of the casting process. A cyclic pattern comprising a withdrawal stroke followed by a dwell is commercially used in connection with the casting device known from the above-mentioned US patent 3,872,913. US patent 3,908,747 describes a controlled, reversed working stroke for forming casting skin, prevention of casting interruptions and compensation of casting shrinkage during cooling in the mold. A reversed stroke for partial remelting of the casting is likewise discussed in British Patent 1 087 026. US Patent 3 354 936 describes a pattern of relatively long, forward strokes followed by periods during which the movement of the casting is stopped and reversed during a relatively short work rate. This pattern is used when casting large ingots, to avoid inverted tempering. In all these systems, however, the stroke rates and net casting rates are slow. In the '936 system, e.g. the forward beats a duration of three to twenty seconds, the backward beats a duration of one second, and the net speed is thirty-three to thirty-eight cm/min.

It is known per se to vibrate a form of continuous casting, in order to achieve a loosening effect which will facilitate the movement of the newly cast rod through the mold and also, more importantly, prevent tension cracks in the solidifying casting skin if the mold advance speed falls below one part. of the cycle exceeds the speed of the bar being cast. Furthermore, the casting process rates associated with mold oscillation will allow the rod to be pulled out of the mold at a constant speed, which will facilitate further processing after casting, such as transforming the rod into a strip. An oscillating mold device of particularly suitable construction is described in US patent application serial no. 117 028, to which reference is made.

It is therefore a main object of the present invention to produce a coolable mold device and a method for continuous casting of high-quality metal strands, particularly of copper and copper alloys containing brass, at production rates that are many times higher than those that have previously been possible with closed form systems.

Another object of the ■■ invention is to produce a mold device which oscillates largely in the same direction as the casting direction of the rod, with little or no lateral movement.

Another object of the invention is to produce such a coolable mold device for casting with the mold device in vibrating motion and immersed in the molten mass.

Another purpose is to produce such a mold device which enables a strong temperature rise along a casting element, particularly at the lower end of a hardening zone, without resulting shell formation or dimensional changes in the casting zone.

Another object is to produce a casting extraction process for use with such a mold device for the purpose of producing high-quality strands at exceptionally high speeds.

A further object of the invention is to produce a mold device with the above-mentioned advantages, which can be produced at a relatively low price, is easy to handle and durable.

A coolable, oscillating mold device for continuous high-speed casting of metal strands comprises a hollow casting element of refractory material. A molten mass, preferably of copper or a copper alloy, for example brass, is in liquid contact with one end of the casting element. A cooling device, preferably water-cooled, is closely fitted around the casting element. Cooling devices have a high cooling capacity, which produces a hardening front in a casting zone at a distance from the end of the casting element in proximity to the molten mass. Means are arranged for transporting the molten mass through the mold device for the purpose of hardening a rod or string. The mold device is stored for swinging movement in a •direction largely parallel to the rod's direction of advance through the mold, and the means which give the mold device an oscillating movement during the advancement of the rod or string, induce a satmme effect as both forward and backward strokes in the casting process. As a result of the swinging movement of the mold simultaneously with the extraction of the rod or string at a constant speed, the relative movement between the mold and the rod can be controlled to a large extent. Means are arranged for the delivery of cooling medium to the cooled form during the swinging movement.

In a preferred version of the invention, the cooling manifold extension section is connected to the cooling device, for supplying coolant to it. The manifold extension section is in turn connected to a supply manifold from which it receives refrigerant. By means of a hood enclosing the cooling device and the manifold extension section, these parts are thermally isolated from the melt. The insulation cap is attached to the supply manifold by means of spring-loaded mounting elements. The manifold extension section comprises three concentric tubes that delimit two intermediate, elongated ring channels, one of which is designed for the delivery of refrigerant to the cooling device, while the other serves to collect the refrigerant from the cooling device. The two innermost pipes are slidably fitted into O-ring packing boxes in the supply manifold.

The means for producing the shape oscillation include at least one hydraulic drive controlled by a servo valve and a computer system. Types of shape oscillation waves can be produced which give unlimited variation in withdrawal speed, return speed and dwell time. This is particularly useful when determining optimal mold movement programs for various casting alloys.

The casting element preferably has a uniform cross-section in the longitudinal direction. The inner wall may be slightly conical or stepped upwards. The casting element is preferably slidably fitted into the cooling device, to facilitate replacement. Within the thermal expansion towards the cooling device, the casting element is held against axial movement by means of a weak projection, in the corresponding cooling wall part near the upper edge and a stop in the outer wall of the casting element, which is brought into contact with the underside of the cooling device. Furthermore, in the preferred version, a metal foil sleeve is introduced between the outer insulating part and the adjacent recess, to facilitate the dismantling of the insulator.

The cooling device is preferably of double-wall construction with an annular chamber between the walls. The inner wall adjacent to the casting element is preferably formed of a whole block of age-hardened chrome-copper alloy, and the outer sleeve is preferably made of stainless steel. The lower ends of the inner and outer walls or "parts" are preferably attached by a copper/gold solder joint. A circulating water stream has a temperature and flow rate within a typical, defined range which provides a high cooling rate for the molten mass which is advanced through the casting element, while at the same time the deposition of water vapor condensate on the mold device or the casting is prevented. A vapor barrier and gaskets are preferably arranged between the submerged end of the cooling device and the enclosing insulation.

The invention is described in more detail below with reference to the accompanying drawings, in which: Fig. 1 shows a simplified perspective view of a string manufacturing plant based on the use of oscillating mold devices and the methods according to the present invention, Fig. 2 shows a side view, partially in section, of the oscillating mold and support structure in connection with a furnace that receives a molten mass, Fig. 3 shows a perspective view of the support structure for the oscillating mold, Fig. 4 shows a separate section of the supply manifold extension section and the molding element of the construction according to Fig. . 2, Fig. 5 shows an enlarged view of the cooling device and the molding element shown in Fig. 4, Fig. 6 shows an upper plan view of the cooling device according to fig. 5, Fig. 7-9 schematically show positions for the casting element in a molten mass during various steps in the swinging movement of the mold, Fig. 10 shows a simplified vertical section where the furnace according to' fig. 1 is shown in its lower and upper extreme position in relation to the mold assemblies, Fig. 11 and 12 show simplified vertical sections of alternative arrangements for controlling the expansion of the casting element under the casting zone. Fig. 13 shows a carriage for storage of an oscillating mold, Fig. 14 shows a separate plan view of the carriage device in the construction according to fig. 2 for storing and moving the oscillating mold, and Fig. 15 shows a side view, partly in section, of the carriage device according to fig. 14.

It is in fig. 1 shows a suitable plant for the continuous production of metal strings of indefinite length by casting the strings through cooled molds in accordance with the invention. Four strands 12 are cast simultaneously from a molten mass which is taken up in a casting furnace 16. The strands, which can have different cross-sectional shapes, such as square or rectangular, and diameters, are described in the following as having a circular cross-sectional shape with a diameter between 6 and 51 mm.

As can be seen from fig. 1, the strings 12 are cast in four cooled molding devices 18 which are stored on four vertically movable carriage assemblies 20. An extractor machine 22 pulls the strings at constant speed through the molding devices and directs them to a pair of booms 24 and 24' which guide the strings to four coilers 26 of the pouring type, where the strings are collected in coils. Each boom 24 is hollow to guide cooling air which is supplied through channels 28 along the boom.

The melt mass is produced in one or more melting furnaces (not shown), or in a combined melting and storage furnace (not shown). Although the present invention is suitable for the production of strings of many different metals and alloys, it is particularly concerned with the production of strings of copper alloys, especially brass. By means of a ladle 30 which is suspended from an overhead crane (not shown), the molten mass is transferred from the melting furnaces to the casting furnace 16. The ladle preferably has a spout of the teapot type, in order to be able to transfer the molten mass with a minimum of foreign material such as slag and foam. To facilitate the transfer, the ladle is pivotably stored in a cradle 32 on a casting platform 34. Through a ceramic pouring vessel 36, the molten mass is led from the ladle 30 to the interior of the casting furnace 16. The outlet end of the vessel 36 is located below the furnace cover and at a point in distance from the mold assemblies 18. In continuous production, in contrast to batch casting, additional molten mass is transferred to the furnace when it is approximately half full, so that the molten mass is mixed both chemically and thermally.

The furnace is mounted on a scissor-type hydraulic elevator trolley 38 with a group of load cells 38a (fig. 10) for sensing the weight of the furnace with its contents. The furnace's height position is controlled by output signals from the load cells 38a, so that the level of the molten mass in relation to the cooling device is regulated automatically. As is most clearly evident from fig. 10, the furnace can be moved between a lower extreme position in which the mold parts 18 are located at a distance above the surface of the molten mass 14 when the furnace is filled, and an upper extreme position (shown by broken lines) in which the mold parts are located near the bottom of the furnace. The height of the furnace is continuously adjusted during casting, in order to maintain the selected immersion depth of the mold parts 18 in the molten mass. In the lower position, the mold parts are accessible for replacement and maintenance, after the oven has been rolled to one side.

It should be noted that the production plant described usually includes auxiliary equipment for level control, such as probes and floats, in addition to periodic, manual measurement by means of a submerged wire. These or other conventional level measurement methods and control systems can also be used instead of the load cells, as the primary system. Although the present invention is described in connection with fixed mold parts and a movable casting furnace, other arrangements may also find application. The furnace can be kept at the same level and melt mass supplied periodically or continuously, to maintain the same level. Other options include a very deep dive, which will make level regulation redundant. A significant advantage of the invention is the possibility of such a deep immersion. Each of these arrangements has advantages and disadvantages which will be obvious to the person skilled in the art.

The casting furnace 16 is a 965-mm coreless induction furnace with a pressed-in aluminum liner that is heated by a power source. An oven of this size and type can accommodate approx. five tons of molten mass. The oven 16 has a pouring spout 16a which leads to an overflow and pouring vessel 42 (fig. 10).

As further appears from fig. 1, the extractor machine 22 comprises four pairs of opposing pinch rollers 44 which are each located in a friction system against one of the strings 12. The pinch rollers 44 are connected by a common shaft which is driven by a servo-controlled, reversible hydraulic motor 46. A conventional hydraulic pump unit for variable volume and constant pressure, which produces pressure up to 210 kp// cm 2, drives the motor 46.

A conventional electronic programming device (not shown) produces a program of signals that control the operation of the motor 46 through a conventional servo system. The program includes a programmed start phase routine which gradually increases the extraction speed. The drive rollers 44 can be individually released from a selected string 12, without interrupting the progress of the other strings.

Fig. 2 shows a mold device 18 which is immersed in a molten mass 14 in a furnace 16. It is in fig. 2 shows a protective cone 48 which melts away after the device 18 has been lowered into the molten mass 14. The protective cone 48 is usually made of copper, and will dissolve completely in less than one minute. The purpose of the protective gel' is to prevent foam and other impurities from penetrating into a casting element 112 during immersion. After the device is immersed in the molten mass and the cone is dissolved, molten metal is drawn through the device 18. The process is initially started by inserting a massive starter rod (with a bolt at the end) through the casting element 112, from the upper end of the device, and down into the molten mass . Molten metal will solidify on the bolt, and when the rod is pulled through the casting element 112, molten metal will follow and solidify along the way. After a hardened rod or string 12 has been introduced between the pinch rollers 44, the starter rod (with a small piece of the string 12) is separated from the rest of the string 12. After being formed by the molten mass 14, the string 12 is continuously drawn out with constant speed using one or more pairs of pinch rollers 44.

The string 12 is thus continuously moved from the molten mass at a constant speed of normally 51-102 cm/min in the direction shown by an arrow 52. During the advancement of the string 12, the entire forming device 18 will oscillate in the vertical direction. In general, the device 18 is connected to a carriage device 20 for controlled swing movement.

During the swing movement, the mold device 18 is cooled by a coolant which is transferred through flexible pipes 56 to a manifold 54 which is mounted on the carriage device 20. This cooling system is particularly described in connection with Figs. 3 and 4.

It is pointed out that even if* in the production plant according to fig. 1, four independently oscillating forming devices 18 are provided for the production of four strings 12, any number of row-positioned forming devices can be used, depending on the particular production requirements.

As the mold device 18 oscillates during the casting process, large, dynamic forces will develop which must be absorbed by the support structure. The substructure which absorbs these loads with minimal deflection is described in detail below in connection with fig. 2 and 3. As can be seen from fig. 3, the support structure as a whole is arranged in the form of a rigid steel box. The vertical loads are absorbed by the construction's column elements 58, 60, 62 and 64, which consist of steel H-beams. The column elements 58, 60, 62 and 64 are joined together through horizontal H-steel beams 66, 68, 70 and 72. The horizontal elements 66, 68, 70 and 72 are preferably welded to the column elements 58, 60, 62 and 64. The horizontal H-beams 66, 68, 70 and 72 are positioned in such a way that the flange surfaces run in a horizontal direction for reasons of maximum rigidity while absorbing the loads caused by the swinging movement. The beams 72 and 74 are further reinforced by angle rails acc. 72a and 74a which are welded to the beams. The beams 66 and 70 are braced in the vertical direction by struts 75, 76, 78 and 80, also made of steel. The lower part of the load-bearing structure is further reinforced by steel beams 82 and 84.

The carriage structure is connected to the angle rails 72a and 74a which hold the entire carriage through the horizontal H-beams 72 and 74. The carriage load paths are carried forward to the frame foundation through beams 86, 88, 78, 80, 75 and 76. Steel H-beams 89 and 90 are welded between the horizontal beams 68 and 72. These beams 89 and 90 support the oscillating carriage's superstructure in the form of vertical H-beams 91 and 92 and horizontal H-beams 93, 94 and 95. The beams 93 and 95 are welded to the steel beam 74 which connects the upper ends of the column beams 60 and 64. The rigidity of the structure is increased by means of the stiffened H-steel beams 86 and 88.

The carriage arrangement 20 (fig. 2) is shown in more detail in fig. 13. This device 20 is constructed of steel corner plates 201 and 202 which are welded to a bottom plate 203 and a back plate 205. A top plate 207 is welded to the back plate 205 and the corner plates 201 and 202 to complete the construction. Plates 201 and 202, with a thickness of approx. 25 mm, is made easier by being provided with holes acc. 209 and 210.

The carriage device 20 supports the manifold 54 (fig. 2) by means of bolts which are passed through holes 211a (fig. 13) which surround an opening 213 in the bottom plate 203. The cast string passes through the opening 213 on its way towards the pinch rollers 44 (Fig. 2). As can be seen from fig. 13 and 14, the carriage device is forced to move in a vertical direction along the rails 215. These rails 215 are separated from the angle plates 201 and 202 by means of spacers 217. The rails 215 and the spacers 217 are bolted and riveted to the corner plates 201 and 202.

The rails 215 have beveled edges which lie closely against chamfered running rollers 219 (fig. 14). The rollers 219 are bolted to the structure 221. The structure 221 includes box sections which increase rigidity. The construction 221 is bolted to the superstructure described in connection with fig. 3.

As shown in fig. 14 and 15, the carriage device 20 is supported on a hydraulic cylinder 225, for turning in the vertical direction. The piston in the hydraulic cylinder 225 is attached to the upper plate of the carriage device 20 by means of a mounting element 227. The hydraulic cylinder 225 is controlled by a servo valve 229 by means of a manifold block 231.

The hydraulic cylinder 225 is itself stored in arms 233 (fig. 14) which are bolted to the structural part 221. The servo valve 229 is controlled by a calculator (not shown) which determines the desired mutual movement between string and form with a view to satisfactory hardening of the cast strand. In particular, the mold oscillation will produce the same effect in relation to the rod or string 12 as a pattern of forward or backward strokes of the string or rod itself.

Figs 7-9 show the effect of mold oscillation on the mold skin distribution, and serve as a reference for the terms "forward" and "backward" strokes. In fig. 7, the mold device 18 is shown at its lowest point in the molten mass 14. At exactly this point, the mold device's acceleration in the upward direction begins, as shown by a small arrow 41. At the same time, the speed of the string in the upward direction is greater than the speed of the mold in the upward or forward direction. It should be noted that the curing skin 12a of the strand 12 is very thin. In fig. 8, the mold device 10 is shown approximately midway in its upward and downward path in the molten mass. As the shape reaches its midpoint, its upward velocity is greater than that of the string. This is due to the acceleration of the forming device in the upward direction, which is approx. 2 g in most cases. It is emphasized again that the speed of the string is constant and that only the speed of the forming device varies. In fig. 8, a hardening front 29 is moved almost to the surface of the melt. The casting skin 12a is thicker than the skin shown in fig. 7 .

Fig. 9 shows the mold in its upper outermost position in the path of movement. At the particular stage according to fig. 9, the speed of the mold in the upward or forward direction is equal to zero, and the mold is about to begin its downward movement back to the position according to fig. 7. In this position shown, the cast skin is thickest. The forward and backward speeds can be set separately in the calculator, to achieve optimal surface quality and material structure. It will appear from fig. 7-9 that the term "forward stroke" denotes the movement of the mold assembly away from the melt mass, while the expression "backward stroke" denotes the movement of the mold assembly further into the melt mass.

A preferred version of the form device 18 is shown in fig. 4 and 5, from which it is clear how the coolant is supplied to the device continuously. The coolant, preferably water, is introduced into the manifold 54 through an inlet 100 and flows downwards through an annular channel 101 in a manifold extension section 102 and continues into a cooling device 103 for cooling a mold 104. The coolant is returned through an annular channel 105 and out through a outlet 106. The channels 101 and 105 consist of the annular spaces which are bounded by three concentric pipes 107, 108 and 109, all of steel. The outer pipe 107 is connected to the manifold 54 by a connecting flange. The two inner pipes 108 and 109 are slidably inserted through O-ring packing boxes 110

in the manifold 54. It is thereby possible to compensate for dimensional changes due to rising temperatures.

The concentric tube pattern of the manifold extension section 102 allows high flow rates of the coolant in association with a reduction of the cross-sectional area of the device which must oscillate in the melt in the furnace. Reduction of the cross-sectional area is important to limit the hydrodynamic load on the oscillating casting mold device.

As shown in detail in fig. 5, a tubular molding element 112 is enclosed by the cooling device 103. The lower end part 112a of the molding element 112 projects over the underside 103a of the cooling device. The casting element portion 112a and at least one part of the cooling device are immersed in the molten mass during casting. Under the influence of cuprostatic pressure, liquid molten mass is forced into the casting element in the direction of the cooling device. In the initial phase, a straight length of rod is introduced into the casting element through a graphite plug and placed with its lower end, which is preferably connected with a bolt, at a certain distance above a normal hardening or casting zone 114. The immersion depth is chosen so that the liquid molten mass reaches the casting zone 114 where the molten mass, due to rapid heat transfer from the mass to the cooling device, solidifies and forms a massive casting without flowing past the starter rod. The melt mass closest to the casting element will cool faster than the melt mass in the middle, so that an annular "skin" is formed around a liquid core. The interface between liquid and solid mass forms a hardening front 114a across the casting zone 114. It is preferred that the top point of the hardening zone 114a is always below the 14 surface of the molten mass. As the hardening is initiated in the zone of the casting element 112 which is provided with an insulating bushing 118, the location of the hardening front is well defined. It is a main feature of the invention that the casting zone is characterized by a high cooling rate and a steep, vertical temperature gradient at the lower end, so that the zone extends over a relatively small length of the casting element 112. These features are a result of the hardening of the molten mass is introduced in the zone of the casting element which is equipped with the insulating part or bushing 118.

It should be noted that although the present invention is described in connection with a preferred, upward casting direction, it is also suitable for use in horizontal and downward casting. It will therefore be understood that the term "lower" means closest to the melt, while the term "upper" means furthest from the melt. When casting down, the "lower" end of the mold will in reality be above the "upper" end.

The casting element 112 is made of a refractory material which largely does not react with the metal vapors and other vapors present in the casting area, particularly at temperatures above 1090°c. The material is usually graphite, although good results have also been achieved with boron nitride. Specifically, a graphite marketed by the Oco Graphite Company under the trademark DFP-3 has been shown. to have exceptional durability and good thermal properties. Regardless of the choice of material for the casting element, it is preferably degassed in a vacuum furnace before installation, in order to remove volatile substances which, by reacting with the molten mass, could cause initial failure or induce surface defects on the casting. The vacuum environment will also prevent oxides of the graphite at the high outgassing temperatures, for example 400°C for 90 minutes in a coarse pump vacuum. It will be realized by the person skilled in the art that the other components of the pump device must also be freed from volatile substances, especially water. , before use. Components made from the refractory material "Fiberfrax" (carborundum co.'s trade name for refractory paper material of aluminum silicon oxide) are pre-treated by heating to approximately 815°c, while other components, e.g. of silicon oxide, normally heated to 177-204°c.

The casting element 112 is largely tubular with a constant inner channel diameter and a practically uniform wall thickness. The inner wall of the casting element is highly smooth to provide little frictional resistance to the axial or longitudinal movement of the casting through the casting element, and to reduce wear. The casting element's similarly smooth outer wall is located during the casting process in a pressure system against the enclosing inner wall 103b of the cooling device 103. The wall surface 103b inhibits the casting element's radial expansion due to the heat effect from the molten mass and the casting, and promotes a very efficient heat transfer from the casting element to the cooling device, as a result of the resulting pressure contact.

The press fit between the casting element and the cooling device is important, as a poor fit that leaves gaps will severely limit the heat transfer from the casting element to the cooling device. A tight fit is also important to prevent longitudinal movement of the casting element in relation to the cooling device due to friction or "drag effect" between the casting and the casting element during the drawing of the casting through the element. On the other hand, the casting element should be able to be removed quickly and easily from the cooling device if it is damaged or worn. It has been shown that all these purposes will be achieved if the mutually corresponding surfaces of the casting element and the cooling device are machined to narrow tolerances that allow a "sliding fit", i.e. an axially directed, sliding introduction and removal of the casting element. The dimensions of the casting element and the corresponding wall surface 103b are chosen in such a way that, due to the casting element's thermal expansion during casting, a press fit is formed. Although the casting element material's coefficient of thermal expansion (5 x 10 ^ in./in.°F) is much lower than that of the heat sink (10 x 10 ^ in./in.°F), the casting element is so much hotter than the heat sink that the temperature difference more than compensates for -the shell in thermal expansion coefficients. The casting element's mid-part temperature through the wall thickness in the casting zone is assumed to be approx. 538°C at a melt mass temperature of 1093°C. The cooling device has approximately the same temperature, normally 27-38°c, as the coolant flowing through.

Mechanical locking is used to secure the casting element

in the cooling device during low-speed operation or during set-up within the element is expanded due to the heat from the molten mass. An uncomplicated eyelet element in the form of a screw or a locking plate has proven to be impractical, because it is cooled by the cooling device with consequent condensation and collection of metal vapors. Such metal deposits can cause surface defects in the casting and/or weld the locking element in its position, which will greatly inhibit the replacement of the casting element. Zinc vapor present when casting brass is particularly troublesome. A useful solution is to arrange a small elevation or irregularity 103c on the inner wall 103b of the cooling device, for example by producing a punching burr using a mandrel. A narrow step 116 which is arranged on the outside of the casting element and which is brought into contact with the underside of the cooling device (or, more accurately expressed, against an "external" insulating bushing or ring 118 which is placed in a recess 103d in the bottom of the cooling device) serves for setting the casting element for assembly, and will further counteract any irregular and high forces that may occur, e.g. in the initial phase. It should also be noted that the one-piece construction of the casting element eliminates joints, especially joints between different materials,

which can collect condensed vapors or direct them to others

flat parts. A one-piece casting element is also easier to replace and maintain than a multi-section element.

Of the alternative arrangements for creating an appropriate, tight-fitting connection between the casting element and the cooling device, ordinary press fitting and heat shrinking can be mentioned. When press fitting, a lubricant of molybdenum sulphide is used, to reduce the probability of the casting element being fractured during the press fitting process. The lubricant will also fill processing scratches on the casting element. During heat shrinkage, the cooling device is caused to expand during heating, after which the casting element is introduced and the tight-fitting connection is created by cooling the assembly. Both the press fitting and the heat shrinking, however, require that the entire mold assembly 18 be dismantled from the cooling water manifold, when a molding element is to be replaced. Compared to the sliding fit, this will prove to be clearly more time-consuming, inappropriate and expensive.

While in the preferred version of the invention a one-piece casting element with a uniform channel diameter is used, it is also possible to use a casting element with a conical or stepped inner wall which tapers in the upward direction, or a multi-section casting element which is composed of two or more parts which are mounted end to end. Tapering in an upward direction is desirable with a view to compensating for the casting's contraction during cooling. Close contact with the casting over the full length of the casting element increases the cooling effect of the mold assembly. Increased cooling is important because it helps to prevent the formation of a central cavity due to uncompensated shrinkage of the molten center of the casting.

In order to reduce the cost, the casting element can be manufactured with an oppositely tapering outer wall,' instead of an upwardly tapering inner wall, or the inner wall 103b in the cooling device. The casting element's thermal expansion in the cooling device during casting produces the desired, upwardly conical shape of the casting element's highly smooth inner wall. The multi-section casting elements can either have a constant channel diameter, or different channel diameters, to produce a stepped, upwardly tapering shape. To avoid troublesome metal deposits between the casting element sections, the joints between the sections should exclusively be above the casting zone. viaere Can the upper section of the sections above the casting zone be press fit fitted, as it is most likely that the lower section will be damaged and have to be replaced.

Without limiting effect, it can be mentioned, as an example, that a casting element, produced in one piece of Poco-type graphite, and suitable for casting 19-mm rod material, "has a length of about 273 mm and a constant wall thickness of about 3 -5 mm. the wall thickness will generally vary with the diameter of the casting. The length of the projecting casting member section 112a is typically 51 mm.

The cooling device 103 is largely cylindrical with a longitudinal central channel which is delimited by the inner wall 103b. The interior of the cooling device includes a channel, generally denoted by 120, which guides the circulating coolant, preferably water, through the cooling device. A number of inlet openings 120a and outlet openings 120b for the coolant are arranged at the upper end of the cooling device. As is clear from fig. 6, these openings are arranged in concentric circles with sufficient openings to provide a high flow rate, typically approx. 8.3 liters per kg casting per minute. A pair of O-rings 122 and 123, preferably of wear-resistant fluoroelastomer, seal the manifold extension section 102 (Fig. 5) in fluid communication with the inlet and outlet ports. A mounting flange 124 on the cooling device is provided with openings 124a which receive bolts (not shown) for securing the form assembly to the manifold extension section. The flange is also provided with an opening (not shown) for the discharge of gases from the annular space between the cooling device and an insulating cap ( fig. 4), through a pipe (not shown) in the manifold 54, to the outside air.

The cooling device has four main components: an inner part 126, an outer part 128, a jacket closure 130 and the mounting flange 124. The inner part is made of an alloy which has excellent heat transfer properties, good dimensional stability and which is hard and durable. Age-hardened copper is preferred, e.g. in an alloy with the designation CDA. 182. The outer part 128, shutter hinge 130 and mounting flange 124 are preferably made of stainless steel and in particular "free machin-ing" 303 stainless for the ring 130 and flange 124, and 304 rust free for the outer part 128. Stainless steel is sufficiently resistant against mechanical stresses, has similar thermal expansion properties as chrome copper and is very resistant in the casting environment. When using stainless steel, very large pieces of age-hardened copper become redundant, thereby simplifying the manufacture of the cooling device.

The inner part is made from a single, cylindrical ingot of solid (crack-free) chrome copper. Besides the consideration of economic and operational safety advantages, the composite cooling device construction is determined by the difficulty of producing a whole ingot of chromium copper, which is large enough to form the entire cooling device. Longitudinal holes 120c are drilled deep into the inner part, to form the inlets 120a. The holes 120c extend at least to the casting zone, and preferably somewhat longer, as shown in fig. 5. The lower ends of the longitudinal holes 120c are connected through transverse bores 120d. The inner part's upper and lower end portions are threaded at 126a and 126b, to receive the mounting flange 124 and closure ring 130, respectively, for structural strength. The closure includes an internal, upward-facing recess 130a in contact with a corresponding abutment on the inner part, which serves to increase the strength of the solder joint, slow down the flow of cooling water in the joint zone and align the ring in relation to the inner part. An outer, upward-facing recess 130b is in liquid-tight contact with the lower end of the outer part 128.

Since the threaded connection at 126a will leak if insufficiently sealed, and because the joint must be able to resist re-dissolution and aging of softened radiator ducts, the joint is also copper/gold soldered. While copper/gold brazing is a conventional technique, the procedure below will provide a reliable joint that will last in the foundry environment. First, the mutually corresponding surface parts of the closure ring and the inner part are copper plated. The coating, which preferably has a thickness of 0.025 to 0.051 mm, must cover the threads, the recess 130a and the groove 130c. The solder material is then applied, by wrapping a wire of the material around the inner part in a solder groove 126c above the threads and in the groove 130c at the upper end of the closing ring 130. Two turns of a wire consisting of sixty percent copper and forty percent gold and with a diameter of 1, 59 mm is preferably used in the solder slot 126c and three mandrels in the slot 130c. A solder paste of the same alloy is applied to the mutually corresponding surface parts. The threaded closure ring is pulled tightly onto the inner part, and the assembly is placed in an oven, soldered end down, and preferably in contact with a supported sheet of refractory alumina-silicon oxide paper material, for example of a type sold by Carborundum Co. under the trademark Fiberfrax. The soldering temperature is measured using a thermoelement which rests against the bottom of one of the longitudinal holes 120c.

In the oven, the assembly is heated to a temperature just below the melting point of the solder alloy for a shorter period of time, e.g. to between 960 and 977°c for ten minutes. The atmosphere in the oven is protected (inert or vacuum) to avoid oxidation. The assembly is then quickly heated to the flow temperature of the solder alloy (1016-1038°C), and then immediately cooled to room temperature, likewise in a protected atmosphere. Solution treatment of the chromium copper is preferably carried out during a separate, second process step, by heating the part to a temperature of 932-954°c for 15 minutes in a protected atmosphere, with subsequent rapid liquid cooling.

After the closure is connected to the inner part, the remaining assembly involves TIG welding of stainless steel

■type 304 to type 303 using rod type 308, after the parts have been preheated to 204°c. The largely cylindrical outer part 128 is welded at 134 to the closure ring. The outer part's upper end part includes an inner recess 128a which is adapted to the mounting flange 124 immediately outside the water outlet openings 120b. These parts are joined through a welding seam 136. The closure and the mounting flange separate the outer part from the inner part, thereby delimiting an annular water circulation channel 120e which runs between the transverse channels 120d and the outlet openings 120b. A screw-shaped spacer 138 is installed in the channel 120e , to create a swirling water flow that will promote a more uniform and efficient heat transfer to the water.. The spacer 138 is preferably made from a 6.35 mm copper stud. 140 which is attached to the inner part A combined aging (hardening) treatment of the chrome copper and stress relief of the welded,

stainless steels are carried out at a temperature of 482°c for at least two hours in a protected atmosphere. The cooling device is then machined and leak tested.

By way of example only, the cooling water is led through the inlets 120a, the holes 120c and 120d and the spiral flow path

which is delimited by the channel 120e and the spacer 138, to the outlets 120b. The water will flow in a typical quantity of approx. 8.3 liters per kg hardened strand in the casting zone per minute. A typical flow rate is 95 liters per minute. The correct water temperature is limited at the lower end by condensation of water vapour. On humid days, condensation can occur at 21°c, and usually at temperatures below 27°c. It will usually be preferred that the water temperature does not exceed 49°c. It should be noted that the functions of the inlet and outlet holes can be reversed, i.e. that the water can be advanced to the outer ring of holes 120b and diverted from the inner ring of holes 120a, without significantly reducing the efficiency of the cooling device. However, the distance between the casting element and the inner hole group is a factor that affects the efficiency of the heat transfer from

the casting to the water. For a 19 mm string, the distance is typically approx. 16 mm. Thereby, the inner part 126 can be redrilled for casting a 25 mm string and receiving an appropriately sized outer insulator 118. In general, the described mold device will provide a cooling rate that is high compared to conventional water jacket coolers for cooled mold casting in closed systems.

Another important feature of the invention is the outer insulating bushing 118 which ensures unchanged dimensions of the casting element in the casting zone and prevents an excessive, outward expansion (trumpet mouth) of the casting element below this zone, which can lead to casting interruptions, initial defects or surface defects. The bushing 118 is also important in that it causes an abrupt change in the casting element temperature in the axial direction immediately below the casting zone. In the absence of the bushing 118, there would for example be a sharp temperature gradient in the casting element entrance zone to the cooling device, so that at the lower portion 112a of the casting member would form a trumpet-shaped casting skin. This extended portion cannot be pulled past the casting zone and into the cooling device. It will wedge and break free from the casting, and may remain in position while casting continues. Such a wedged portion may cause poor surface quality or breakage of the string This is prevented a v the bushing 118 which mechanically limits the outward expansion of the casting element immediately below the casting zone 114. With the help of the bushing, the casting element is also insulated to a large extent against the cooling device, whereby a moderate temperature change is achieved in the casting element zone between the underside 103a of the cooling device and a point just below the lower edge of the casting zone 114.

The bushing is made of a refractory material with a relatively low thermal expansion coefficient, relatively low porosity and good thermal shock resistance. The low coefficient of thermal expansion limits the outward radial pressures from the bushing against the cooling device and will, in conjunction with the cooling device, force the graphite to maintain a largely uniform inner diameter in the casting element. Due to the low coefficient of thermal expansion, the bushing 118 will also be easily removed from the cooling device by evenly heating the entire assembly to approx. 120°C. A suitable material for the bushing 118 is cast silicon oxide glass (SiO 2 ) which can be machined.

The bushing 118 extends in the vertical direction between a lower end surface 118a flush with the underside 103a of the cooling device and an upper end surface 118b slightly above the lower edge of the casting zone. During the production of a 19 mm brass rod, when using a bushing with a wall thickness of approx. 6.4 mm and a length of 35 mm achieved satisfactory results.

In practice, it has been shown that metal vapors penetrate between the inner insulating bushing 118 and the recess I03d in the cooling device, where they condense and attach the ring to the cooling device, thereby making disassembly difficult. This difficulty is solved by placing a thin intermediate layer 142 of steel foil between the ring and the recess. The bushing and the intermediate layer are held in the recess by special heat shrinking in such a way that assembly and disassembly can be easily carried out when the bushing and the cooling device are heated to 204°C.

Figs 11 and 12 show alternative arrangements which will ensure that the casting takes place in a dimensionally uniform part of the casting element, and enable control of the casting element's expansion below the casting zone. Fig. 11 shows a casting element 112</> which is identical to element 112, except that the inner wall of the projecting, lower part 112a is expanded conically in an upward direction. The angle of inclination is chosen to achieve a largely constant channel diameter when the casting element portion expands in the molten mass. However, this is difficult to achieve for manufacturing reasons. In practice, it is also necessary to use both the bushing 118 (shown by broken lines) and the casting element 112' in order to achieve the high production speeds and good casting qualities that are characteristic of the present invention.

Fig. 12 shows an "inner" insulator 114 which is inserted slidingly into a casting element 112" which is identical to the casting element 112, except that it ends flush with the underside 103a of the cooling device. The inner insulator 144 is made of refractory material which does not react with the molten metal and which has a relatively low coefficient of thermal expansion and therefore will not deform the cooling device. The lower end of the insulator 144 projects slightly above the lower end of the casting member 112" and the cooling device and is provided with a stop 144' of enlarged outer diameter, with the same function as the stop 116 on the casting element 112. The insulator's upper end should be close to the upper end of the casting zone, normally approx. 13 mm below the upper edge of the bushing 118. If the upper end extends too high in relation to the external insulator, the string will be molded against the insulator and chipped. The inner insulator's channel dimensions are also of great importance, particularly in the starting phase, during a stop or during deceleration, because the molten mass begins to solidify on the inner insulator 144. To avoid casting interruption, the insulator 144's inner wall must be smooth and conical with an upward expansion. As with the casting element 112', the outer insulator or bushing 118 is used in connection with the inner insulator 144. to reduce the above difficulties.

As further appears from fig. 4, the cooling device 103 and the mani fold extension section 102 are surrounded by a ceramic cap 146, and are thereby thermally insulated from the metal melt, so that the cooling device can carry out its function and cool the mold, so that the bar hardening can take place. The cap 146 is made of a suitable, refractory material, e.g. cast silicon oxide. The cap 146 is attached to the manifold 54 by means of a ring 148 which is forced by a spring 149 against the manifold 54. With this method of attachment, the cap 146 is pulled tightly against the cooling device 103 with clearance for dimensional changes due to different thermal expansion. The spring 149 is pre-tensioned to develop a total force that exceeds the highest occurring G-load during the oscillation, thereby maintaining a seal between the cap 146 and the cooling device 103. The cap enables the immersion of the mold device to a preselected depth in the melt. Although immersion to a level below the casting zone is practical, the extremely high production rate that characterizes the invention is partly a result of relatively deep immersion, at least to the level of the casting zone. An advantage of this type of immersion is that it facilitates the conveyance of the molten mass to the liquid core in the casting in the casting zone.

A vapor shield 150 and gaskets 151 (see also fig. 5) are arranged in the gap between the hood and the cooling device adjacent to the casting element, to prevent the penetration of molten mass and vapors into the gap and to heat-insulate the cooling device further. The gaskets preferably consist of three or four annular layers or "donuts" of the aforementioned refractory Fiberfrax fiber material, while the vapor shield preferably consists of a "doughnut" of molybdenum foil fitted between the gaskets 151. The shield 150 and the gaskets 151 extend from the casting element extension 112a to the outer circumference of the cooling device is flat. The overall thickness, typically 6.4 mm, is sufficient for these layers to be brought into firm contact with the cooling device's underside 103a and the end surface of the cap 146.

During a typical process cycle, the casting furnace 16 is filled with a molten alloy. A rigid bar of stainless steel is used to initiate the casting. A steel bolt is screwed into the lower end of the rod. The rod has the same dimension as the string to be cast, e.g. 19 mm diameter, and can therefore be pushed down through the form device and connected to the extraction machine 22.

During the descent into the molten mass, the casting element part 112a (or a refractory casting element extension such as the inner insulator 144) in the mold device is covered by a cone of a material, preferably solid graphite, which will not contaminate the molten mass being cast. An additional alloy cone 48 of a material, preferably copper, which does not contaminate the melt, covers the lower end of the cap 146. The cones penetrate the slag and foam on the surface of the melt, thereby reducing the amount of foreign particles that are collected under the cooling device and in the casting element. The melt dissolves the cone 48, and the starter rod pushes the smallest graphite cone away from the casting element, after which the cone floats to the side. An advantage of the preferred version of the invention with a projecting casting element portion 112a is that it supports and locates the smallest graphite cone during its descent into the molten mass. To function satisfactorily, the outer surface of the largest cone 48 should form an angle of forty-five degrees or less with the vertical plane.

After the graphite cone has been pushed away, the bolt will be in the molten mass, and the molten mass solidifies on the bolt. During the start-up phase and after that. the strings are advanced sufficiently far above the drive wheels 44, the cast rod is cut under the steel bolt, and the strings are automatically diverted towards the booms 24 and 24'. Before the rod is reset in a storage rack for later use, the short casting piece with the steel bolt is removed. In an alternative design, the starter rod comprises a short piece of a rigid, stainless steel rod which is attached to a flexible cable which, due to its flexibility, can be advanced directly towards the boom 24. The extractor is then accelerated to the output speed of the casting process. Between shifts and during temporary interruptions, e.g. for replacement of a coiler, the string is stopped and clamped. Casting is resumed simply by releasing and accelerating to full speed.

During the withdrawal of the string 12, forward strokes will cause the hardened casting formed in the casting or hardening zones. is pulled upwards, whereby the molten mass is brought into contact with the cooled casting element and a skin is quickly formed on this newly exposed element surface. In steady operation, the rod is pulled forward at a constant speed of 508 to 1016 cm per second. minute. At the same time, the entire mold assembly, including the encapsulated molding element 112, oscillates in the vertical direction with an acceleration of approx. lg, thereby achieving a top speed of approx. 10 cm per second in each direction. The swinging motion allows the newly formed skin to strengthen and attach to the previous cast. Due to the cooling device's high cooling capacity and the steep temperature gradient caused by the outer insulator 118, hardening takes place very quickly over a relatively short length of the casting element. As previously mentioned, the typical melting temperatures for oxygen-free copper and copper alloys are approx. 1038-1260°C. When practicing the invention, the insulator (the bushing 118) will insulate the molten mass from the cooling device, whereby the molten mass is maintained in a liquid state in the casting element below the casting zone. Near the top of the insulator, the temperature of the melt will drop rapidly and solidification will begin. When casting 19 mm brass rod at a speed of more than 254 cm/min. the casting zone will run in a longitudinal direction for a length of 25-38 mm. At the upper edge of the casting zone, the strand is solidified. The estimated average temperature of the brass castings in the hardening zone is approx. 900-955°c. The brass casting leaving the mold assembly has a typical temperature of 816°c. A clearance around the string at the upper end of the mold assembly ensures the presence of oxygen or a water-saturated atmosphere to burn off zinc vapors before they condense and flow downwards to the casting zone. The string produced in this way is of exceptionally good quality. The string is characterized by a fine grain size and dendritic structure, good tensile strength and good ductility.

The description includes an oscillating forming device of simple and economically reasonable construction and an extraction process for use in connection with the forming device, which enables the continuous production of high-quality metal strings, particularly of brass, at extraordinarily high speeds. In particular, the mold device and the extraction process represent advanced solutions to the many, serious difficulties associated with the casting environment, such as extreme temperatures and temperature differences, metal and water vapors, foreign particles present in the furnace and differences in the thermal expansion coefficients of the materials that form the mold device.

The invention is further illustrated by the following, non-limiting example.

When using the apparatus according to fig. 2 became a string

12 continuously cast from a molten mass, of automatic brass

(free-cutting brass), CDA 360. 1998 kg of molten alloy was filled into furnace 16 and maintained in a molten state. The alloy CDA has the following composition:

After the casting of a strand 12 has been initiated by lowering a tube with a screw at the end through the casting element 112 in molten mass, with subsequent withdrawal of the tube in a known manner, the hardened strand 12 was pushed forward by the rollers 44 at a speed of 508 cm per minute. At the beginning of the continuous extraction of the string 12, the part 18 of the oscillating mold device was immersed in the molten mass to a depth of approx. 13 cm. During casting, the immersion depth of the part 18 varied between approx. 18 and 8 cm. The temperature during the oscillating movement of the mold was maintained at 1010°C, and molten alloy was supplied to the furnace 16 during casting to the extent necessary to maintain the immersion depth for the mold part 18. The casting element 15 for the production of the string 12 with a diameter of approx. 19 mm had a diameter of 19 mm. The forward and backward shaped speed during the oscillation reached a peak value of 10 cm per Sec. at a mold acceleration of 1 g. The distance traveled by the mold between the upper and the lower position in the melt was approx. 4.5 cm. At the exit of the casting element 112, the string 12 had a temperature of approx. 816°c.

After casting, the bar was hot-rolled with good results. Cast grain size was of fraction 1 mm. The processed structure was finely recrystallized (0.025-0.050 mm) along the cut surface. : It will be obvious to the person skilled in the art that the invention will be able to be modified. Instead of the described casting element 112 which runs along the full length of the cooling device 112, in many cases an element can be used which only projects a short distance above the casting zone. The cooling device can also have many different designs and dimensions. Such modifications fall within the scope of the following requirements.

Claims (11)

1. Process for continuous casting of a metal strand from a metal melt, characterized by process steps that include application of a casting element with a cooling device having a first end which encloses a part of the casting element to enable cooling of parts of the casting element, and an insulating element which is placed between a part of the casting element and cooling device, to isolate a part of the casting element against cooling in the cooling device, and which is located at the first end of the cooling device and extends over a first section between the casting element and the cooling device, immersion of the first end of the cooling device in the molten mass to a depth greater than the first section, to create a hardening front in the casting element below the level of the molten mass, when the molten mass is withdrawn through the cooling device, extraction of molten metal from the molten mass through the casting element which is simultaneously cooled in the cooling device, whereby the cooling causes complete hardening of the molten metal in a strand in a zone of the casting element below the level of the molten mass and above the insulating element, and the hardened strand is withdrawn from the molten mass at a constant speed , and oscillation of the casting element in a direction parallel to the string's direction of advance. 2. Method in accordance with claim 1, characterized in that the first end of the casting element protrudes above the first end of the cooling device. 3. Method in accordance with claim 1, characterized in that the cooling device is flowed through with coolant to a point immediately above the upper edge of the insulating element, so that the hardening of the molten mass in a strand can be initiated in the zone of casting the element that is covered by the insulating element, and so that the molten mass in a strand can harden completely in a zone of the casting element above the insulating element. 4. Procedure in accordance with claim 3, characterized in that the part of the cooling device which is immersed in the molten mass is protected against the heat from the molten mass by means of an insulating material which forms an insulating fence between the molten mass and the cooling device. 5. Method in accordance with claim 1, characterized in that the string is pulled out of the casting element at a speed of 508-1016 cm per minute. 6. Method in accordance with claim 5, characterized in that the casting element oscillates with an acceleration of approx. 1 g in each direction while achieving a top speed of approx. 10 cm per Sec. 7. Method in accordance with claim 6, characterized by a wood oscillation frequency of 12-150 periods per minute. 8. Device for continuous casting of a metal strand from a metal melt, characterized in that it comprises a largely tubular casting element with a first end in liquid connection with the molten mass, a cooling device with a first end enclosing a part of the casting element, to enable cooling of parts of the casting element,' an insulating element which is placed between a part of the casting element and the cooling device, to isolate a part of the casting element against cooling in the cooling device, and which is located at the first end of the cooling element and extends over a first section between the casting element and the cooling device, means for submerging the first end of the cooling device in the molten mass to a depth greater than the first section, for creating a hardening front in the casting element below the level of the molten mass, when the molten mass is withdrawn through the cooling device, means for extracting molten metal from the molten mass through the casting element which is simultaneously cooled in the cooling device, whereby the cooling causes complete hardening of the molten metal in a strand in a zone of the casting element below the molten mass level and above the insulating element, and the hardened strand is extracted from the molten mass at a constant speed, and means for oscillating the casting member in a direction parallel to the direction of string advance in a pattern of forward and backward beats. 9. Device in accordance with claim 8, characterized in that the cooling device is flowed through by coolant to a point immediately above the upper edge of the insulating element, so that hardening can be initiated in the zone of the casting element that is covered by the insulating element, and so that the molten mass in a strand must be able to harden completely in a zone of the casting element above the insulating element. 10. Device in accordance with claim 8, characterized in that the height of the molten mass is continuously adjusted in relation to the cooling device. 11. Device in accordance with claim 10, characterized in that the height of the molten mass is adjusted by means of an elevator which is raised depending on a - signal related to the weight of the molten mass.