KR100447465B1 - Method and device for casting of metal - Google Patents

Abstract

A method and a device, during casting of metal in a mould (12) which is open in both ends in the casting direction and where, in the mould, an incoming primary flow of melt is braked and split and the secondary flow is controlled by means of static or periodic low-frequency magnetic fields acting on the melt, for ensuring that the upper surface of the melt, the meniscus (17), does not solidify by the provision of at least one inductive heater (18) adapted to apply a magnetic alternating field which acts on and develops heat in and/or compressive forces acting on the melt close to the meniscus.

Description

[0001] METHOD AND DEVICE FOR CASTING OF METAL [0002]

During a continuous or semi-continuous casting process for casting a metal or metal alloy, the hot metal melt is injected into a cooled mold having open ends at both ends in the casting direction. The mold is preferably water-cooled.

While passing through the mold, the molten material is cooled by the water-cooled mold, and the cast strand is formed. When the cast strand leaves the mold, the cast strand has a self-supporting surface layer which solidifies around the residual melt. The melt may be injected into the mold by a number of methods, such as one or more tapping jets, a casting tube that opens below the top surface of the melt in the mold, or a channel that opens into the mold interior.

Regardless of how the melt is injected into the mold, a part of the purpose of braking the hot melt is to prevent uncontrolled ingress of hot melt containing slag particles or other metal particles, To control not only the solidification process but also the thermal distribution in the non-solidified portion of the cast strand.

The inflow of uncontrolled melt in the non-solidified portion of the cast strand is problematic in terms of both quality and manufacturing technology. If the incoming melt is introduced into the mold in an uncontrolled manner, the impact causes the incoming melt to penetrate the internal depth of the uncooled portion of the strand, making it difficult to separate the particles contained in the melt. Instead of separating the particles into a top surface, they attach to the surface of the solidification product. In addition, the self-supporting surface layer is weakened, increasing the risk of the melt destroying the surface layer formed in the mold.

For example, in order to braking and dividing an incoming melt, a configuration in which one or more static or low frequency periodic magnetic fields are arranged in the melt inflow path is known from Swedish Patent Application No. SE 436 251. As described above, if the hot melt passes through the inner depth of the non-solidified portion of the cast strand without braking, problems arise in terms of quality and manufacturing. The uncontrolled second flow may cause problems in terms of quality and manufacturing technology in that the coagulation process is not controlled. If the second flow through the upper surface, i.e. the meniscus, towards the upper portion of the hot melt, is very weak, there is a risk that the meniscus will condense. Since the meniscus is completely or partially coagulated, the condensed meniscus is accompanied by problems in the production technique. Such solidification may be reflected in the quality of the cast strand in the form of surface defects.

If the temperature in the meniscus lowers the dissolution rate of the cast powder supplied to the top surface of the melt, the surface quality is adversely affected by the temperature of the melt which is too low near the meniscus, And is attached to the mold inner wall while passing through the mold.

Attachment of the melt to the mold results in surface defects and in the worst case the coagulated self-supporting layer of the cast strand may be ruptured. This rupture can cause the melt to break the shell of the strand and flow over the cast strand to the bottom of the mold. Therefore, the casting process is interrupted, and time must be spent cleaning the metal flowing out of the casting apparatus before restarting.

If the ascending flow is too strong, the turbulence will form a wave on the upper surface and the slag will flow into the melt from the upper surface, resulting in a problem of the quality, especially the presence of unwanted non-metallic particles in the metal.

It is an object of the present invention to provide a method of manufacturing a metal mold, in which when cast metal is braked and divided by at least one static magnetic or low frequency periodic magnetic field in a mold into which a hot metal melt is injected while both ends are opened in the casting direction, The temperature of the melt / mold and the cast strand / mold is maintained at a sufficiently high temperature while maintaining a sufficiently high temperature of the metal at the top of the meniscus, i.e., the melt, without the risk of undesirable flow and turbulence from occurring in the meniscus , And also to improve the lubrication conditions between the melt / mold and the cast strand / mold, thereby achieving a remarkable improvement in quality and productivity.

It is a further object of the present invention to provide an apparatus for carrying out the method.

The present invention relates to a method for continuous or semicontinuous casting of a metal or metal alloy in a cooled mold.

The present invention is based on the idea that a first flow of a hot metal melt is supplied to a cooled mold having open ends at both ends in the casting direction so that the first flow of such melt, while the metal is cast in the mold, Or a periodic low-frequency magnetic field so that the temperature of the metal remains high enough on the top surface of the melt, i.e., the meniscus. The invention also relates to an apparatus for carrying out the method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Fig. 1 shows an embodiment of the invention provided in a casting in a conventional mold for continuous or semicontinuous casting, Fig. 2 shows a mold which is partially filled with metal during casting, The embodiment of the invention provided in the casting in Fig.

During the casting of the metal in the mold in which the first flow of the hot metal melt is fed, with both ends open in the casting direction, according to the invention, the first flow into which the metal melt flows, acts across the casting direction The preferred temperature control and casting conditions for the melt adjacent to the meniscus are braked and divided by a magnetostatic or low frequency periodic magnetic field, and the conditions of casting are such that a magnetic alternating field acting on the melt adjacent to the melt surface, And the like. Here, the inductive heater may be composed of a single-phase or a multi-phase.

An alternating magnetic field, preferably a high frequency alternating magnetic field, acts on the melt to generate heat in the melt so that the temperature of the melt adjacent to the meniscus can be controlled simultaneously, or alternatively, the high frequency alternating magnetic field causes the compressive force . By the compressive force, the pressure between the mold wall and the melt is reduced, and the lubrication condition can be greatly improved.

Therefore, there is an advantage that the surface characteristics of the cast strand are improved and the casting speed can be improved without deteriorating the surface characteristics. This advantage is usually made possible by the combination of compressive force and braking by a magnetostatic or low frequency periodic magnetic field, in accordance with the present invention. If only a high frequency magnetic field is applied to generate a compressive force acting on the melt, there is a risk that the melt surface in the mold direction will become unstable when casting at least heavy metals or metal alloys such as steel.

By combining one or more static or low frequency periodic magnetic fields that stabilize the surface of the melt as well as the braking of the incoming melt and one or more high frequency magnetic fields that generate either or both of the heat in the melt and the compressive force acting on the stable surface, Quality and manufacturing technology are significantly improved in casting compared to the prior art.

According to a first embodiment of the present invention, by providing one or more static or low frequency periodic magnetic fields acting on the non-solidified portion of the cast strand in the mold to control the second flow generated in the melt, the temperature distribution is further controlled . That is, such a magnetostatic or low-frequency periodic magnetic field is applied to act on the second flow path occurring in the melt to control the temperature distribution in the non-solidified portion of the cast strand. Thus, since a safe and reliable casting process can be maintained, for example, productivity such as casting structure and content, as well as productivity and casting speed, is improved.

In accordance with the present invention there is provided a method of controlling at least one static or low frequency periodic magnetic field that stabilizes the surface of a melt as well as braking of the incoming melt and at least one high frequency magnetic field that generates both a compressive force acting on the stable surface and / The control of the temperature distribution is equally improved by providing it at the inlet end of the hot-top casting or in combination with the insulating sleeve directly connected to the inlet end of the mold.

During casting, the insulating sleeve is at least partially filled with molten metal, and an inductive heater is disposed at the sleeve height for temperature control of the melt present in the sleeve. By applying one or more alternating magnetic fields to the molten metal present in the insulating sleeve, such alternating magnetic fields act on the melt adjacent to the meniscus of molten metal present in the insulating sleeve. Thus, heat is generated in the melt existing in the insulating sleeve, and the temperature in the melt can be controlled. At the same time or incidentally, the high frequency alternating magnetic field generates a compressive force acting on the melt, and this compressive force significantly reduces the pressure between the walls of the sleeve and the melt, thereby greatly improving the lubricating conditions.

Thus, the utility of the advantages presented by the cast-iron casting to significantly improve the surface properties of the cast strand, improve the cast structure of the strand, and improve the casting speed without the risk of degrading the quality is significantly increased. Thus, these advantages can be achieved by combining at least one static or low frequency periodic magnetic field that stabilizes the surface of the melt and a compressive force generated by a high frequency magnetic field acting on the stable surface.

If only a high frequency magnetic field is used to generate a compressive force acting on the melt, the pressure reduction at the surface of the melt in the sleeve direction becomes unstable when casting at least a heavy metal such as steel or a metal alloy, So that excellent and uniform lubrication is threatened. By combining one or more static or low frequency periodic magnetic fields acting on the solids in the mold with one or more high frequency magnetic fields acting on the melt in the insulating sleeve, a significant improvement in terms of quality and manufacturing techniques can be achieved do.

Thus, it is possible to avoid the coagulation of the melt present in the insulating sleeve, in particular to form a solidified surface charge, thereby avoiding adhesion to the wall surface of the sleeve.

In particular, an important point is that the melt can be prevented from solidifying and sticking to the transition from the sleeve to the cooled mold. This also may be achieved by the incoming first metal flow being in an overtemperature state, but this approach provides a state in the mold / sleeve that is very difficult and dangerous to control, which can lead to catastrophic failure such as surface defects, poor casting structures, Results.

The above two embodiments are preferably combined to further improve the temperature distribution of the melt during casting and, in particular, the control of the temperature distribution associated with the initial solidification step in the melt adjacent to the cooled mold in a continuous or semi-continuous casting process can do.

In the embodiment of the present invention shown in Figs. 1 and 2, the first flow of the hot melt is introduced into the mold 12, which is open at both ends in the casting direction. During the continuous or semi-continuous casting process, one or more cast strands are formed in the mold 12, wherein the mold 12 is usually a water-cooled copper mold.

A magnetostrictive or low frequency periodic magnetic field is applied to the non-solidified portion (13) of the cast strand (11) to braking and splitting the melt flowing into the mold (12), the first flow of the hot melt Penetrates deeply into the interior of the cast strand 11 and controls the flow of the non-solidified portion 13 of the strand.

To apply a magnetostatic or low frequency periodic magnetic field, the magnetic pole may consist of a permanent magnet or an inductive coil provided with a direct current or a low frequency alternating current as shown in the figure. The magnetic poles include the cores 14a, 14b, 14c and 14d and the windings 15a, 15b, 15c and 15d arranged around the cores 14a, 14b, 14c and 14d, 14b, 14c, 14d and return paths 16a, 16b are arranged between the poles 14a, 14b, 14c, 14d to connect the poles together as external circuits, And forms a closed magnetic circuit together with a working magnetic field.

The applied first or lower frequency periodic magnetic field brakes and splits the first flow of the incoming hot melt to provide an excellent condition for reducing the risk of slag entering the melt and at the same time separating the non-metallic particles.

As a result of the splitting, a second flow occurs and the circulation of the melt in the non-solidified portion 13 in the cast strand 11 is somewhat controlled. The second magnetostatic or low frequency periodic magnetic field controls the generation of the second flow, and above all, to ensure sufficient heat supply to the meniscus, i.e., the top surface 17 of the melt, and also to ensure that the meniscus 17 coagulates It is necessary that a sufficiently strong flow should occur near the meniscus 17. This flow is controlled so that the cast powder and other non-metallic particles are not strong enough to be drawn into the melt.

In order to ensure that a sufficient amount of heat is supplied to the melt adjacent to the meniscus 17 so that there is no danger of the non-metallic particles being drawn into the melt, in accordance with the present invention, The placed inductive heater 18 complements the static system, and the inductive heater 18 is a single or multi-phase heater.

When an alternating magnetic field, preferably a high frequency alternating magnetic field, acts in the melt, heat is generated in the melt so that the temperature of the melt adjacent to the meniscus can be controlled. At the same time or additionally, the high frequency alternating magnetic field generates a compressive force acting on the melt 13. This compressive force reduces the pressure between the wall of the mold 12 and the melt 13, thereby significantly improving the lubrication conditions.

If only one high frequency magnetic field is applied to generate a compressive force acting on the melt, the melt surface 20 is not sufficiently stable with respect to the mold during casting of at least a heavy metal such as steel or a metal alloy, . According to a first embodiment of the present invention shown in Fig. 1, the first and second high-frequency magnetic fields and at least one additional stationary or low-frequency periodic magnetic field are combined to control a second flow occurring in the melt, The compressive force generated by the high frequency magnetic field acts on the stable surface 20 and thus a favorable improvement in terms of quality and production technology can be achieved compared to the conventional technique for continuous or semi-continuous casting have.

The combination of the magnetostatic or low frequency periodic magnetic field and the at least one high frequency magnetic field can improve the casting speed without increasing the surface characteristics of the cast strand 11 and deteriorating the surface characteristics.

According to another embodiment of the present invention, in the second embodiment of the present invention shown in Fig. 2, an insulating sleeve 19 is supplemented at the inlet end of the mold. The insulating sleeve 19 adjacent to the cooled mold is usually used for semi-continuous casting of fragile blanks, such as copper, aluminum or extrusion blanks of alloys based on such metals.

Typically, a plurality of such blanks are cast on a casting table by introducing a molten material from a blast furnace or intermediate container into a plurality of water-cooled molds located in the casting table. At this time, the insulating sleeve is positioned as an extension of the mold 12 over the casting mold 12 in the casting direction.

Thus, the structure of the cast strand is monitored, the surface properties are improved, and the possibility of increasing the casting speed is increased. However, in order to achieve the foregoing, it is required to mount the heat insulating sleeve 19 having excellent precision and repeatable characteristics as well as a technique of the apparatus operating vehicle.

The critical point prevents the melt from solidifying in the sleeve 19 and also prevents the coagulated surface membrane from sticking to the sleeve 19. [ If the solidified surface layer is uniformly formed in the sleeve 19, the desired improvement of the surface properties becomes difficult and if the melt solidifies in the surface charge adhering to the transition from the sleeve 19 to the mold 12 cooled, Dangerous consequences will arise.

If the cast strand 11 continues to fall below the mold 12, the surface film tears and surface defects occur in the longitudinal direction; In the worst case, the solidified surface layer tears and flows down the mold. Another reason for the enlargement of the surface defects is that a surface layer of one piece solidified at the transition between the sleeve 19 and the mold 12 adheres to the transition and enlarges the scratches along the cast strand 11. [

In accordance with the second embodiment of the present invention shown in Figure 2, by disposing the inductive heater 18 at the height of the insulating sleeve 19, the abovementioned dangerous situation is caused by the high frequency magnetic field, which usually acts on the melt in the sleeve, So that the temperature of the melt 13 in the heat insulating sleeve 19 is controlled and the melt can be prevented from being kept in a liquid state.

At the same time, compressive forces acting on the melt 13, preferably on the melt 13 against the sleeve 19, are generated. In particular, the compressive force is reduced between the melt 13 and the sleeve 19, and between the melt 13 and the mold 12, in combination with the magnetostatic or low frequency periodic magnetic field, It is possible to provide an improved lubrication condition between the mold 19 and the melt 13 and between the mold 12 and the cast strand 11 and the mold 12.

Therefore, the static magnetic field stabilizes the surface, and the compressive force applied by the high-frequency magnetic field acts uniformly in time and space. Therefore, according to the present invention, the high-frequency magnetic field acting on the upper fused portion of the mold is combined with the static or low-frequency periodic magnetic field so that the formation of the first solidified surface layer is moved from the sleeve 19 to the mold 12 The lubrication condition is improved.

Thus, the risk of the solidifying surface being formed and adhered to the wall of the sleeve 19 is prevented, and also the melt is prevented from clotting and adhering to the transition from the sleeve 19 to the mold 12 cooled.

Claims (10)

Wherein at least one first flow of hot molten metal is injected into the mold 12 having open ends at both ends in the casting direction and the first flow of molten molten metal is injected into a static or low frequency periodic magnetic field A method of casting metal by braking and splitting, Wherein at least one alternating magnetic field is configured to generate compressive force and heat acting on the melt on the upper surface of the melt, i.e. near the meniscus, Wherein at least one static magnetic or low frequency periodic magnetic field is additionally disposed across the casting direction to control the second flow of liquid metal occurring in the non-solidified portion of the cast strand. The method of claim 1, wherein the at least one alternating magnetic field is a high frequency alternating magnetic field. A method according to any one of the preceding claims, characterized in that an insulating sleeve (19) is located in the mold (12) or in close proximity to the inlet end of the mold, Wherein the metal casting is carried out by a metal casting method. At least one first flow of hot molten metal is injected into the mold 12, which is open at both ends in the casting direction, and the first flow of molten molten metal is introduced into a static or low frequency periodic magnetic field A method of casting metal by braking and splitting, Wherein at least one alternating magnetic field is configured to generate compressive force and heat acting on the melt on the upper surface of the melt, i.e. near the meniscus, An insulating sleeve (19) is located in the mold (12) or in close proximity to the inlet end of the mold, the insulating sleeve being such that the molten metal is at least partially filled during casting, Wherein the at least one alternating magnetic field is configured to generate compressive force and heat acting on the melt adjacent to the meniscus of the molten metal present in the insulating sleeve. The method of claim 4, wherein the at least one alternating magnetic field is a high frequency alternating magnetic field. The method according to claim 4 or 5, characterized in that the second flow of liquid metal occurring in the non-solidified portion of the cast strand is controlled by a static magnetic field or a low frequency periodic magnetic field disposed across the casting direction Way. Wherein during metal casting in a mold that is open at both ends in the casting direction and is configured to have at least one first flow of hot molten metal, (14a, l4b, 15a, l5b) in the form of either or both of a coil or a permanent magnet provided with a direct current or a low frequency alternating current flows across the casting direction for braking and dividing the first flow of the melt A metal casting apparatus configured to apply a magnetostatic or low frequency periodic magnetic field to the melt present in the mold, At least one inductive heater (18) configured to apply an alternating magnetic field to generate heat and compressive forces acting on the melt proximate to the meniscus, - a magnetic pole adapted to apply to the melt present in the mold one or more additional static or low frequency periodic magnetic fields to control the second flow of liquid metal occurring in the non-solidified portion of the cast strand, Is either a coil or a permanent magnet provided with a direct current or a low frequency alternating current, or either one of them. 8. A mold according to claim 7, characterized in that it comprises an insulating sleeve (19) located in the mold or close to the inlet end of the mold, said insulating sleeve being characterized in that the molten metal is at least partly filled during casting Metal casting equipment. Wherein during metal casting in a mold that is open at both ends in the casting direction and is configured to have at least one first flow of hot molten metal, (14a, 14b, 15a, 15b) in the form of either or both of a coil or a permanent magnet provided with a direct current or a low frequency alternating current flows across the casting direction in order to brak and divide the first flow of the melt. A metal casting apparatus configured to apply a magnetostatic or low frequency periodic magnetic field to the melt present in the mold, At least one inductive heater (18) configured to apply an alternating magnetic field to generate heat and compressive forces acting on the melt proximate to the meniscus, - the insulating sleeve (19) is located in the mold or close to the inlet end of the mold such that during melting the molten metal is at least partly filled in the insulating sleeve and the molten metal present in the insulating sleeve And an inductive heater (18) for applying an alternating magnetic field for generating a compressive force and heat acting on the melt adjacent to the meniscus of the metal casting. The method according to claim 9, wherein the magnetic pole (14a, 14b, 15a, 15b) in the form of either or both of a coil or a permanent magnet provided with a direct current or a low frequency alternating current Further comprising a magnetic pole for applying at least one magnetostatic or low frequency periodic magnetic field to the melt present in the mold to control a second flow of the molten metal.