DE2363609A1 - METAL CASTING METHOD AND DEVICE - Google Patents

Description

Patent Attorneys Dipl.-Inc- F. \ v'eic <-v * vn,

Dipl.-Ing. H, Weickma.nn, Dipl.-Phys. Dr. K. Fincke Dipl.-Ing. F. A. ¥ eickmann, Dipl.-Chem. B. Huber

S MUNICH 86, DEN

PO Box 860 820

MÖHLSTRASSE 22, CALL NUMBER 98 3921/22

SUMITOMO.METAL IBDUSTRIES LIMTTED,

15s 5-chome, Kitahama, Higashi-ku, Osaka City, Japan SUI-IITOMO SHIPBUILDING AKD MACHIIiERY CO. LTD. 2-2-1, Obternachi, Chiyocla-ku, Tokyo, Japan

Method and apparatus for casting metal

The invention relates to metal casting, and more particularly to a method and an apparatus for. Casting of metal that allow Avoid or reduce macro- or micro- or micrometallographic heterogeneities, which are mainly in the center of Cast ingots or continuously cast strands arise and on gradual Cooling, cooling or rapid cooling are due to liquid metal that is poured into the mold or into the liquid metal core which remains within a solidified metal shell. This process creates a magnetostatic field with over 10,000 Gauss applied to the melt or the liquid metal in the core during the solidification of the same to form a block or strand with homogeneous metallographic structure '.

It is known that when solidifying metal, the center of the formed Body or the casting center tends to a kind of heterogeneous structure, which is usually called center porosity, center deposition or internal cracks

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education is referred to, this tendency then essentially hexvoiced becomes when the liquid metal is rapidly cooled in a resting state. Reference is made to Japanese patent 33 025/1972 in this regard. It is also known that this heterogeneity is avoided or reduced can only be achieved by moving the molten metal up to its Solidification and that various types of devices have been proposed for this purpose in order to move the liquid metal by means of to effect electromagnetic force.

The prior art methods of achieving movement of the liquid metal due to electromagnetic forces include a rotating electromagnetic field method such as that in US Pat Japanese Patent 99 62/1956 were published, wherein a method a device for generating an electromagnetic field with a Three-phase alternating current is used as in the Japanese patent 32 486/1972 is published and another method uses a wandering electromagnetic field device operated by "Wf echseist rom, as described in U.S. Patent 3,656,537. All of these known methods have resorted to a copper wire coil, which surrounds the shape or is placed very close to this shape or the metal shell and which is operated with a single-phase or three-phase alternating current; whereby the liquid metal is moved electromagnetically due to the changing magnetic field that is built up in the melt and due to the eddy current © »induced in the melt.

In the known methods in which alternating current to generate a Motive power is used, require large amounts of electricity, which by ' the copper wire coil must be sent through. Therefore they show Ampere turns of the copper wire coil have an extremely high value, so that water cooling or oil cooling is necessary in order to see the joule of heat to remove. In addition, the coil of the magnetic field generator has overall very large dimensions. Especially in the case when the coil

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surrounds a large cast body, the operability is due to the Joul * see head limited and the cost of a practical unit are enormous.

According to the invention, it is different from the techniques mentioned above prior art that have sought refuge in alternating magnetic fields "in order to obtain a strong motive force, a very intense one Magnetostatic field of at least more than 10,000 Gauss in the molten metal built up by a single magnet.

As a result, the size and cost of the magnetic field generator can be considerable be reduced. While a sufficient electromagnetic movement effect with a single magnetic field generator or magnet according to the invention can be obtained, the molten metal can have another strong electromagnetic motion effect by a combination of a Variety of magnetostatic field generators are added, which are so arranged are that the most efficient magnetic flux distribution is obtained »On in this way it is possible to generate a strong movement force that could not be generated with the known alternating current method, namely this power is generated with an extremely small and particularly cheap device generated when compared to a known device.

According to the invention, the magnetostatic field is generated by direct current by means of constructed of a superconducting solenoid magnet. The superconducting solenoid is made of a superconducting metal, which has the property of having an electrical resistance of zero at a liquid temperature To have helium of -268.9 C. For example, an intermetallic niobium-tin compound and a niobium-titanium alloy are used for this purpose for use, this metal at the dex temperature of liquid helium when connected to DC power. Since the solenoid has no electrical resistance at working temperature, a very fine wire or thread used v / grounding with a large number

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of turns can be arranged in a room. As the whole Solenoid can easily be kept at the temperature of liquid helium, it is just as easily possible to generate a high magnetostatic field of 70,000 to 100,000 Gauss in the center of the solenoid.

Further details, advantages and features of the invention emerge from the following description in conjunction with the claims and the drawing, in which the invention is illustrated by way of example «In the drawing shows:

Fig. 1 is a schematic representation of a device in which superconducting Solenoid magnets according to the invention are used in a calm casting process;

FIG. 2 shows schematic representations of devices according to the invention ^LSS, which come in a continuous casting process for the application;

5 shows a refrigeration regulator; -

Fig. 6 is a schematic.es circulation system for liquid helium, which at

a continuous casting process according to the invention toii '__

Application comes; and

7A each is a graph showing the sulfur and carbon sample content distributions shows in an ingot obtained according to the invention and in such an ingot in which no electromagnet " field effect takes place.

Fig. 1 shows a device according to the invention with a superconducting Solenoid magnet that is used to generate near one side of a permanent mold an intense magnetostatic field is arranged within the liquid metal in the mold. In Fig. 1, reference numeral 1 denotes a Form made of a non-magnetic material and the reference numeral 2 a solid metal jacket which surrounds the liquid metal 3. The reference number 5

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denotes the superconducting solenoid magnet that is near one side the mold is arranged so that the magnetic flux generated by this magnet acts on the liquid metal. The solenoid magnet 5 is within one Refrigeration controller 7 is arranged and is held in the required position by a non-magnetic carrier 8 in this arrangement. The refrigeration regulator 7 has an insulated high-performance boiler, which is an evacuated double-walled Has insulating structure made of a non-magnetic metal. This boiler is filled with liquid helium, the liquid level 9 in the is essentially kept at a constant level. The liquid helium is filled up from a supply line 10 and the evaporated helium is returned to a helium liquefier by means of a return line 11 » The refrigeration regulator has an upper flange 21 which is connected to a power supply 21 for supplying heavy current to the solenoid magnet 5 is provided is. Thermal insulation 15 is placed between the cold regulator and the mold to protect the wall of the cold regulator. The magnetic flux 6, which is generated by the solenoid magnet and acts on the liquid metal, can relative to the liquid metal by reciprocating vertically of the refrigeration controller by means of a "frame 13 movable in the vertical direction or by horizontally moving the mold on wheels 16 and" Rails 17 are moved so that the intense magnet ο static field is effective can act on the liquid metal and cause it to flow in the desired direction. Of course it is to this one Purpose desirable to move both the refrigeration regulator and the mold at the same time. It is also possible to have the refrigeration regulator in a horizontal position To move direction and shape in vertical direction «

Figs. 2 to 4 show other forms of the invention for a continuous Casting methods are used. The refrigeration controller is not shown in this procedure, but is included. In Figs. 2 and 3 denoted the reference numeral 1 * a bottomless water-cooled mold and the reference numeral 2 a solidified metal shell that has not yet solidified

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or liquid metal 3 surrounds. The strand containing the liquid metal "'

is essentially at constant speed in the direction of the arrow deducted. In these arrangements, two solenoid magnets are opposed to each other Poles (north and south poles) directed towards the envelope. In the case of Fig. 2, both solenoid magnets 5 and 5-1 are on the same side of the casing, but arranged in different heights «With this arrangement it is possible to adjust the magnetic field strength or the magnetic flux density by changing the distance between the two magnets. In the case of Fig. 3, the two solenoid magnets 5 and 5-1 are on opposite sides Sides of the casing in different vertical positions.

arranges. With this arrangement of the solenoid magnets in relation to the lateral In the direction of the strand according to the example according to FIG. 2, an extremely improved effect can be achieved.

In the case of continuous casting, the strand is essentially with constant speed withdrawn and this means that the solenoid magnet is constantly moved relative to the liquid metal. This is in this case a movement device for the refrigeration controller, which is connected was mentioned with Fig. 1 is not necessary. The impact effect the magnetostatic field on the liquid metal is not just on the induced eddy current, but also to the density gradient or to the flux density of the field in the liquid metal. With others In words, the liquid metal that is just solidifying is subject to a combined effect of eddy currents and field gradients. In the case of the example according to Fig. 3, the strand is continuously withdrawn, so that within ' a solid shell enclosed liquid metal usually with a Progressing at a speed of 0.5 to 3 meters per minute. Due to the Under the influence of the magneto-static field, forces act on the liquid metal which tend to stop the movement of the metal. However, there is a field gradient is present in the liquid metal, there is also a density gradient of the force acting on the liquid metal, so that the liquid metal

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is moved. Although the field gradient is only created by a single magnet is generated, the magnetic flux pattern can be changed to suit the casting type and the various types of ingots or ingots by appropriately changing the number and arrangement of the solenoid magnets are generated, as shown for example in FIGS. 2 to 4.

The solenoid magnet for generating the magnetic field is thereby determines that various conditions, such as the intensity of the exerted force and the mounting position, are taken into account,

FIGS. 5 and 6 show examples of devices that are used for practicing the Invention are required. Fig. 5 shows an example of a refrigeration controller. The illustrated cold controller or cryostat is generally designated by 7 and consists essentially of an upper part with a lower flange 22 and a lower flange which has a solenoid magnet records. The inside of the same is with a vacuum pump, not shown via a line 23 in connection and is under a pressure of

-5
Maintained 10 mm Hg. Reference numeral 24 denotes a magnet housing, the upper part of which is connected to a line 25. Liquid helium is supplied through a supply line 10 in order to fill the housing 9 and the line 25 to a constant level 9. Vaporized helium is returned through a discharge line 11 to a helium liquefier, as shown in FIG. 6. In this example, the auxiliary coolant used is liquid nitrogen with an evaporation temperature of -195.8 C. A plurality of downwardly hanging fine pipes 27 and is arranged in the upper part of the refrigeration controller. Liquid nitrogen is supplied through a pipe 29 and vaporized nitrogen is discharged outside through a drain pipe. The refrigeration controller used in connection with the present invention

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is used, consists entirely of a non-magnetic material, such as 304 stainless steel. Although not shown, it includes Device a liquid wedge level sensor, a thermometer, a vacuum meter, Power connections for the magnet 5, an adjustment device for the position of the magnet, a safety device and insulating means.

Fig. 6 shows an example of a liquid helium delivery system used in conjunction with a continuous casting process or a bent strand. In this method, liquid metal is poured from a casting system 31 into a bottomless, water-cooled mold 1 '. Solenoid magnets 5 and 5-2 are arranged according to the example of FIG. 3 on the dom path of the strand 2 emerging from the mold 1 * directly below the second cooling zone. Liquid helium and liquid nitrogen are supplied to the refrigeration regulator and the vapor is regenerated in the manner described above. Only the recirculation of helium is shown. Helium gas, which under a pressure of 150 atm. is stored in helium gas bombs 33 and under a pressure of about 1 atm in a helium gas container 34, is fed to a helium gas compressor 35 and the helium gas compressed by the compressor 35 is sent to a high-pressure helium gas container 36 and from there to a helium liquefier 37. In the helium is liquefied, helium gas is subjected to a heat exchange with liquid nitrogen at high pressure and then passed through a gas expander, as a result of which it is converted into liquid helium, which is passed to the refrigeration regulator 7 via a liquid tank 38. Evaporated helium from the refrigeration regulator passes to the helium gas container 34 either through the liquefier 37 or directly for the recovery of liquid helium for recirculation. Although liquid helium is very expensive, essentially no helium is lost in the course of the recirculation, which includes evaporation and liquefaction, since the treated helium circulates in a closed loop. In the iron foundries with production facilities

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of .nitrogen, liquid nitrogen is cheap and light than By-product available »That's why there is no cost factor from Point of view of the running costs »

The following experimental example shows the effects produced by the invention are achievable.

attempt

2,000 kg of a low-carbon molten steel were in one High frequency induction furnace manufactured and placed in a vertical test facility cast for continuous casting, which was provided with a magnetostatic field generator according to the invention. The chemical Composition of the steel was 0.15% carbon, 0.30% silicon, 0.71% manganese, 0.01% phosphorus, 0.012% sulfur and 0.03% soluble Aluminum with the remainder being iron. The bar produced had one Thickness of 130 mm and a width of 26.0 mm. The magneto static The field generator was placed directly below the form with its magnets near one of the broad sides of the ingot, reflecting the arrangement 2 corresponds to “The first half of the steel, namely 1,000 kg, was cast without the application of a magnetic field and the field v / was applied to the remaining half. The thus obtained ingot became samples at the positions corresponding to the supply of 400 kg and 1.600 kg based on the start of pouring. From each of these Samples were test pieces cut out at intervals of 2 to 10 mm in the direction of the thickness of the bar in order to prevent the segregation of the constituents ^ The results of these experiments are shown in Figures 7A and 7B. It can be seen that the ingot obtained by application of a magnetostatic field exhibited very little deposition of carbon and sulfur in the center compared to the bar that was obtained without applying a field. It was also confirmed that the applied magnetostatic field is particularly useful for refiners

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of the primary structure is effective and capable of separating efficiently considerably below 2.0. The data for the magnets used in this experiment were as follows:

Number of magnets: 2

Magnet type and size: solenoid magnet with an inner diameter of 50 mm and an outer diameter of 180 mm as well a width of 50 mm

Number of turns of the solenoid: 22,000

Solenoid wire: copper wire 0.4mm in diameter, the 40 insulated fine Contains wires made of Nb-Ti alloy, with a resin coating after the winding of the wire is applied "

Electricity: 30 amps

Field strength: 70,000 Gauss at the center of the solenoid and 22,000 Gauss at the End of the solenoid.

Initial consumption of liquid helium: 25 liters.

By using a superconducting solenoid magnet, a magnetostatic Field of high force flux density, namely above 10,000 Gauss, which is generated by passing a high current through a conventional solenoid coil could not be obtained, obtained in a large space cheaply and with very small units to exert an effective acting force on the liquid metal. As also confirmed by tests it is possible to suppress precipitations and center porosity and to set the precipitation coefficient to 2, 0 or below lower. In addition to the fact that the growth of dendrites can be suppressed by slight agitation of the liquid metal, become crystalline precipitates or ionized concentrates with higher Susceptibility as the mother melt is influenced by the extremely intense magnetic field and tend towards the higher force flux density

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to be drawn. While using the above experimental results an experimental device for continuous casting was obtained is it can be seen that similar results are obtained in the case of the device according to F5g «1 provided that the mold and magnet are moved relative to one another and that application to larger ingots is possible is. In this case, the mold should be made of a non-magnetic metal such as stainless steel.

For the reasons given above, it is possible to melt the metal quickly to cool without causing damage to a central heterogeneous structure are due. In this way it is possible to do that To pick up the rapid cooling system, so as to increase the strand withdrawal speed increase and thereby reduce the possibility of cracking during the rolling process, so that the invention in large. Measure to improve the Manufacturing of products contributes.

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Claims (1)

Pa.Jt 1. Vei'falix'en for casting metals, characterized in that the not yet solidified metal, which is present within the mold or within a casing formed from already solidified metal is, is moved by the action of force, whereby this did not solidify Metal through a heterogeneous magnetostatic field with intensities of at least above 10,000 Gauss is treated, at least by a superconducting solenoid magnet is generated, which is arranged in the vicinity of this non-solidified metal. 2. The method according to claim 1, characterized in that the intensity of the magnetostatic field about 70,000 Gauss in the center of the solenoid magnet and 22,000 Gauss at the end of the solenoid magnet, ■ 3. Device for casting metals, characterized by a device (1-, 1 ^J , 2) for receiving the non-solidified metal, a device (5) for generating a heterogeneous magnetostatic
Field in this non-solidified metal, this device for generating the field being provided in the vicinity of one side of the device (1, 1 ') for receiving the melt and by devices
(13, 16, 17) for the relative movement of the receiving device (1, 1 ') and the device (5) for generating the field to one another. 4. Apparatus according to claim 3, characterized in that the device comprises at least one superconducting solenoid magnet (5) for generating the magnetostatic field. 40 98 29/02 9 7 5. Device according to Ans pi-uch 3, characterized in that the device for receiving the molten metal is a mold (1, 1 '). 6. Apparatus according to claim 3, characterized in that the device for receiving the molten metal there is a casing (2) which results from the solidification of the melt. 7. Apparatus according to claim 3, characterized in that the device (5) a magnet ο static to generate the magnetostatic field Can generate field with intensities above 10,000 Gauss in the molten metal. 8. Apparatus according to claim 4, characterized in that the solenoid magnet (5) is hollow and is formed by winding a wire containing very fine superconducting insulated wires and after winding the Wire is provided with a resin coating. 9 »Device according to claim 3, characterized in that the device for generating the magnetostatic field comprises a plurality of superconducting solenoid magnets (5, 5-1, 5-2) which are attached to opposite Sides of the device for receiving the melt with opposite poles, which are directed against opposite sides of this device are, are arranged » 10 «Device according to claim 3, characterized in that the device for generating the magnetostatic field comprises a plurality of superconducting solenoid magnets (5, 5-1, 5-2), which on opposite sides of the device (1, 1 ') for Receiving the melt are arranged with the same poles, which are directed against opposite sides of this device. 409829/0297 11. The device according to claim 5, characterized in that the movement device a device (13) for vertically moving the device (5) for generating the magneto static field. 12. The device according to claim 5, characterized in that the movement device Has wheels (16) attached to a support carriage for the Casting mold (1) are arranged and run on rails (17) which the Support the wheels. 13. Apparatus according to claim 6, characterized in that the movement device is a mechanism for continuously peeling off the solidified metal shell. 14. Apparatus according to claim 13, characterized in that the withdrawal speed this jacket is in the range between 0.5 and 3 meters per minute. 15. The device according to claim 3, characterized in that the device (5) for generating the magnetostatic field comprises a cryostat or cold controller (7) which has at least one superconducting Solenoid magnet (5) and is filled with liquid Heli. \ Xm and that an auxiliary cooling device for cooling the liquid helium and helium recovery devices including a helium liquefier (37) are provided. 16. The device according to claim 15, characterized in that an insulating device (15) is provided between the cryostat (7) and the device for receiving the melt. 17. The device according to claim 15, characterized in that the cryostat (7) is made of a non-magnetic metal and has an evacuated double-walled structure. 409829/0297 . Device according to claim 15, characterized in that the HiHs cooling device a chamber (26) for liquid nitrogen which is arranged in the upper part of the cryostat (7) and a plurality of thin tubes (27) depending from the chamber (26), that a feed tube (28) for the supply of liquid nitrogen and a discharge pipe (29) is provided for discharging vaporized nitrogen are and that the supply pipe (28) and the discharge pipe (29) with the chamber (26) for the liquid nitrogen in connection stand. 19. Device according to claim 15, characterized in that the helium recovery device a gas bomb (33), a gas container (34), a compressor connected to the gas bomb and the gas container (35), a pressurized gas container (36) through the compressor is filled, a helium liquefier (37), the is connected to the pressurized gas container (36), and a tank (38) for liquid helium in which the in the Liquefier generated liquid helium is stored and which is connected to the cryostat (7), which evaporated in the cryostat (7) Helium to the gas container for recovery of the liquid helium for the recirculation, 20. Apparatus according to claim 19 »characterized in that the evaporated Helium reaches the gas container through the liquefier (37) 409829/0297