CN101111333A - Equipment and method for continuously casting magnesium billet or magnesium plate using electromagnetic field - Google Patents

Abstract

A device and method for continuously casting magnesium billet or magnesium plate by using electromagnetic field compensates the small latent heat of solidification of magnesium, controls the solidification speed, and stirs the molten metal in the mold through the electromagnetic field, so that continuous casting can be carried out. The apparatus comprises: a mold for continuous casting of cast billets or slabs; coils located outside said molds to which electric current can be applied; and cooling nozzles located outside said molds and cast billets or slabs. During casting, a current is applied to the coil at a frequency of 2 to 1,000D, or a current of 50 to 10,000A is applied at a frequency of 200 to 200,000D. By applying a low-frequency or high-frequency electromagnetic field to a mold during continuous casting of magnesium, a magnesium billet or block with improved internal quality and no surface defects can be produced at a high casting speed.

Description

Equipment and method for continuously casting magnesium billet or magnesium plate using electromagnetic field

technical field

The invention relates to equipment and method for continuously casting magnesium billet or magnesium plate by using electromagnetic field. The equipment can compensate the small solidification latent heat of magnesium and control the solidification speed by applying high-frequency or low-frequency electromagnetic field, so that continuous casting can be carried out.

More specifically, the present invention relates to an apparatus and method for continuously casting magnesium billets or slabs using an electromagnetic field, which applies a low-frequency electromagnetic field to molten metal during continuous casting of magnesium, thereby heating the molten metal, thereby enabling compensation of magnesium The small solidification latent heat controls the solidification speed; the equipment also includes a low-frequency electromagnetic stirring device located under the mold, so that high-quality billets without surface defects can be produced at high casting speeds.

In addition, the present invention relates to equipment and methods for continuously casting magnesium billets or slabs using electromagnetic fields. Electromagnetic stirring device, so that the billet without surface defects can be produced at high casting speed.

Background technique

Magnesium alloys are very lightweight metals that are widely used due to their excellent physical properties such as high specific strength, excellent electromagnetic interference (EMI) shielding, excellent heat dissipation and vibration Various fields, from lightweight components for transportation to components for electronic devices for information communication. Since the latent heat of solidification of magnesium is very small, it will solidify rapidly during the casting process, so it cannot be cast by conventional continuous casting methods.

In addition, since magnesium products are usually manufactured by die casting, there are no patents or reports on continuous casting of magnesium. The only exception is that the twin-roll continuous casting method is used to manufacture magnesium plates.

Meanwhile, since the latent heat of solidification of the magnesium alloy is small, it solidifies rapidly during the casting process, and thus has various defects after solidification, continuous casting of the magnesium alloy is difficult. For continuous casting of magnesium alloys, it is necessary to suppress cooling greatly, so there is a limit to the increase of casting speed.

LKR in Austria has developed a method of continuously casting magnesium slabs called MGACAST. This method is used to continuously cast magnesium slabs by modifying the conventional direct chill (DC) casting method used to continuously cast aluminum. Since this method forms many defects on the surface of the cast magnesium plate, there is a problem that it is necessary to use flame cleaning to remove the defects from the surface of the magnesium plate, and its casting speed is very low.

In addition, although the magnesium plate can be manufactured by horizontal continuous casting, many defects are formed on the surface of the cast magnesium plate, and the casting speed is extremely low.

Contents of the invention

technical problem

In view of the above problems, we have made the present invention. An object of the present invention is to provide an apparatus and method for continuously casting magnesium billet or magnesium slab by using an electromagnetic field, which can prevent various surface defects from forming during the casting process, speed up the casting rate, and reduce internal defects and increase productivity.

Another object of the present invention is to provide an apparatus and method for continuously casting a magnesium billet or a magnesium slab using an electromagnetic field, which can reduce internal defects by stirring molten metal to form an equiaxed structure, and can also increase productivity.

Technical solutions

According to one aspect of the present invention, the above objects and others are achieved by providing an apparatus for continuous casting of magnesium billets or slabs using electromagnetic fields, said apparatus comprising: a mold for continuous casting of cast billets or slabs; Coils outside the mould, which can be used to apply current to them; cooling nozzles located outside the mould, and the cast billet or sheet.

Preferably, a low frequency current is applied to said coil and a replaceable ring is provided in the upper part within said mould.

Preferably, said ring is made of graphite.

Preferably, the mold has a circular or rectangular cross-section, and the coil is arranged around the mold.

Preferably, the cooling nozzles cool the mould, coil and cast billet or sheet by spraying water directly on them.

Another aspect of the present invention provides a method for continuously casting magnesium billets or magnesium slabs using an electromagnetic field. The method uses the equipment for continuously casting magnesium billets or magnesium slabs using an electromagnetic field according to the above aspect of the present invention. A current with a frequency of 2 to 1,000□ is applied to the coil of the above device.

Another aspect of the present invention relates to an apparatus for continuously casting magnesium billets or magnesium slabs using an electromagnetic field, the apparatus comprising: a mold in which slits are formed for continuous casting of cast billets or slabs; a coil to which electric current can be applied; and an electromagnetic stirring device located in the lower part of the mould.

Preferably, the mold has sections separated by the slits in which cooling water channels are formed.

Preferably, the slit is formed in the central area of the mould, extending from below the upper end of the mould to above the lower end of the mould.

Preferably, the slit has a width of 0.2-0.3□ and is filled with a vitrified bond so that an electromagnetic field can be applied to the molten metal in the mold while preventing leakage of the molten metal.

Preferably, the mold has a circular or rectangular cross-section around which the coil is provided.

Preferably, the equipment further includes a cooling nozzle located between the mold and the electromagnetic stirring device.

Preferably, the cooling nozzle sprays water directly on the cast billet or plate and the electromagnetic stirring device, thereby cooling them.

Another aspect of the present invention provides a method for continuously casting magnesium billets or magnesium slabs using electromagnetic fields, the equipment used in the method is the equipment for continuously casting magnesium billets or magnesium slabs using electromagnetic fields according to other aspects of the present invention, wherein the A current of 50-10,000A with a frequency of 200-200000□ is applied to the coil of the equipment, and a current of 20-1,000A is applied to the electromagnetic stirring device of the equipment at a frequency of 2-100□.

Beneficial effect

According to the invention, the device comprises: a mold formed of copper or copper alloy with good electrical conductivity; a coil located outside the mold for applying an electromagnetic field to the mold during the casting of magnesium, thereby The molten magnesium is heated by induction, and the contact pressure between the mold and the solidified unit is reduced by electromagnetic pressure to avoid the formation of surface defects during casting; an electromagnetic stirring device is set at the lower part of the mold to increase the casting speed and Mold depth (depth of pool).

In addition, the present invention uses a low-frequency electromagnetic field when casting magnesium, including a mold made of copper, copper alloy or aluminum alloy with good conductivity, and a coil outside the mold, which is used to apply an electromagnetic field to the mold. The electromagnetic field inductively heats the molten magnesium while stirring the molten metal with a low-frequency electromagnetic field, enabling continuous casting.

Exemplary configurations and operations of the present invention will be described below with reference to the accompanying drawings. It should be noted, however, that the present invention is not limited to these specific configurations, and the following descriptions are given as examples for understanding the present invention.

Brief description of the drawings

The above and other objects, features and other advantages of the present invention can be more clearly understood by the following detailed description, taken in conjunction with the accompanying drawings, in which:

1 is a conceptual diagram of a device for continuously casting a magnesium billet or a magnesium slab using an electromagnetic field according to a first embodiment of the present invention, the device includes a circular mold, and a coil to which a low-frequency current can be applied;

Fig. 2 is a plan view of the equipment used in the first embodiment, which equipment includes a circular mold, and a coil to which a low-frequency current can be applied;

3 is a conceptual diagram of a device for continuously casting a magnesium billet or a magnesium plate using an electromagnetic field according to a second embodiment of the present invention, the device includes a circular mold, and a coil that can apply a high-frequency current to it;

Fig. 4 is a plan view of the equipment used in the second embodiment, the equipment includes a circular mold, and a coil to which a high-frequency current can be applied;

Fig. 5 a and Fig. 5 b are a kind of variation figure of the equipment used in the second embodiment of the present invention, and this equipment comprises rectangular mould;

Fig. 6 is a schematic diagram showing the direction of current in the mold of the device of the present invention and the direction of the magnetic field it produces;

7 is a schematic diagram comparing the surface of molten metal formed by a conventional casting technique and the surface of molten metal obtained by applying a low-frequency current and a high-frequency current by an apparatus according to the present invention;

Figures 8a and 8b are photographs of the surface of a magnesium billet manufactured by conventional techniques and equipment according to the invention, respectively.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a conceptual diagram of an apparatus for continuously casting a magnesium billet or a magnesium slab using an electromagnetic field according to a first embodiment of the present invention.

According to a first embodiment, a device 1 for continuously casting magnesium billets or slabs using an electromagnetic field comprises: a mold 11 for solidifying molten metal 15, a coil 12 located outside said mold 11 for applying a low frequency current thereto , a ring 13 positioned on the inner upper surface of the mold 11 to control the solidification of the molten metal so as to be able to cast smoothly, used to cool the ring 13, the casting billet or plate 14 and the cooling water of the mold 11 Nozzle 16.

2 is a plan view of an apparatus for continuously casting a magnesium billet or a magnesium slab using an electromagnetic field according to a first embodiment.

Although the mold 11 and coil 12 are shown to have a circular cross-section, the mold 11 and coil 12 may have a rectangular or other shaped cross-section.

As shown in FIG. 6, when a low-frequency current is applied to the coil 13, a magnetic field and a current are induced in molten magnesium 15 within a mold 11 made of a metal having good electrical conductivity.

These induced currents not only heat the molten metal through Joule heating, but also generate electromagnetic forces in the molten metal by interacting with the electromagnetic field. When the molten metal is heated by the induced current, the cooling effect of the cooling water is weakened at the unit where the molten metal is first solidified, so that the molten metal can be solidified stably.

The electromagnetic force generated in the molten metal 15 has a gradient, the electromagnetic force at the surface of the molten metal is larger, and the electromagnetic force inside the molten metal is smaller, so that the molten metal is stirred in the mold and the internal structure of the billet is improved. .

The mold 11 is made of a material with good electrical conductivity such as aluminum or copper alloy. A ring 13 of graphite may be inserted into the mold 11 to provide a lubricating effect to promote good casting of the cast billet or slab while delaying cooling of the cast billet or slab.

The length of the ring 13 extends from the upper part of the mold to about 20 mm below the surface of the molten metal, and the thickness is equal to or greater than 2□. When the ring 13 is damaged, it can be replaced with a new ring.

The ring 13 delays the cooling of the molten metal and at the same time reduces the friction between the cast billet or plate and the mould, through the exothermic effect and heat transfer weakening effect produced by the interaction of the graphite and the electromagnetic field.

The frequency of the low-frequency electromagnetic field applied to the coil 12 is 2-1,000□, and the frequency is determined according to the size of the cast billet or plate. The current intensity is also determined according to the size of the cast billet or plate and the casting speed.

The mold 11 and the cast billet or plate 14 are cooled by direct cooling with cooling water through nozzles 16 . The cooling water cools the mold 11 , the ring 13 inside the mold 11 and the coil 12 simultaneously.

3 is a conceptual diagram of an apparatus for continuously casting a magnesium billet or a magnesium slab using an electromagnetic field according to a second embodiment of the present invention.

According to the second embodiment, the equipment 100 for continuous casting of magnesium billets or magnesium plates using electromagnetic fields includes: a mold 101 for solidifying molten metal 105; a coil 102 located outside the mold 101 to which high-frequency current can be applied; Located at the lower part of the mold 101, an electromagnetic stirring device 103 for stirring the molten metal 105; Nozzle 104 for cooling.

In the equipment 100 for continuously casting magnesium billets or magnesium slabs using an electromagnetic field according to the second embodiment, the mold 101 has a cooling water channel 107 formed therein through which cooling water circulates, and the mold 101 also includes a channel 107 A manifold 108 is associated for the supply and discharge of cooling water.

FIG. 4 is a plan view of an apparatus 100 for continuously casting magnesium billets or slabs using an electromagnetic field according to the present invention.

Although the mold 101 and coil 102 are shown to have circular cross-sections, the mold 101 and coil 102 may have rectangular or other shaped cross-sections.

The mold 101 is formed with a slit 109 along the casting direction so as to apply a high-frequency electromagnetic field to the molten magnesium. As shown in FIG. 3 , each slit 109 is formed in the middle region of the mold 101 such that each slit 109 extends from below the upper end of the mold 101 to above the lower end of the mold 101 . The length of the slit 109 is within a range that does not adversely affect the rigidity of the mold 101 .

The width of each slit 109 is equal to or greater than 0.1□, preferably 0.2˜0.3□. The number of the slits 109 is within a range that does not adversely affect the rigidity of the mold 101 . Each slit 109 is provided to induce high frequency and is preferably filled with a vitrified bond or the like to prevent leakage of the molten metal 105 .

Since the penetration depth of the high-frequency electromagnetic field in the molten metal is extremely small, it is difficult for the applied high-frequency electromagnetic field to enter the mold 101 made of copper. Therefore, the slit 109 is formed by machining in the mold 101 so that a high-frequency electromagnetic field can be efficiently applied to the molten metal 105 . On the other hand, the low-frequency electromagnetic field can be applied to the molten metal in the copper mold because it has a large penetration depth in the molten metal. There is therefore no need to form slits in the mold.

5a and 5b are diagrams of a rectangular mold 101' of an apparatus for continuously casting magnesium billets or slabs using an electromagnetic field according to a second embodiment. Specifically, Fig. 5a is a front view of a rectangular mold 101', wherein a slit 109' is formed in the middle region of the mold, extending from below the upper end of the mold 101' to above the lower end of the mold 101'. The length of the slit 109' is within a range that does not adversely affect the rigidity of the mold 101'.

The width of each slit 109' is equal to or larger than 0.1□, and the range of the number of slits 109' is subject to the fact that the rigidity of the mold will not be negatively affected.

Fig. 5b is a sectional view along the line A-A' of Fig. 5a, in which separate cooling water passages 107' for cooling the mold 101' are formed in each section 110' separated by slits.

Regarding the apparatus 100 used in the second embodiment, as shown in FIG. 6 , when a high-frequency current is applied to the coil 102 , a magnetic field and a current are induced in the molten magnesium 105 in the mold 101 separated by the slit 109 .

These induced currents not only heat the molten metal 105 by Joule heating, but also generate electromagnetic forces in the molten metal 105 by interacting with the magnetic field. The electromagnetic force increases the curvature of the molten metal 105 surface S where the molten metal 105 contacts the mold 101 (see FIG. 3 ), while reducing the contact pressure between the cast billet or sheet 106 and the mold 101 .

With the apparatus in the embodiment, the surface of the molten metal can be strongly heated by Joule heating, so that the solidification rate can be controlled while increasing the latent heat of solidification, so that continuous casting can be performed without causing problems caused by uneven solidification and quenching. Defects caused by cold.

The apparatus 100 for continuously casting magnesium billets or ingots using an electromagnetic field according to the second embodiment also has a nozzle 104 connected to the lower part of the mold 101, which cools the cast billet or plate 106 by directly injecting gas or water. .

In addition to controlling the cooling of the cast billet or plate 106 by a high-frequency electromagnetic field, thereby enabling continuous casting, the apparatus in the second embodiment may also include an electromagnetic stirring device 103 connected to the lower part of the mold 101, and the stirring device 103 uses To stir the molten metal 106 to control its internal quality.

When the electromagnetic stirring device 103 is rotated in the circumferential direction in the mold 101 to rotate the molten metal 105, the columnar structure of the molten metal is broken, so that the overall structure of the cast billet or plate 106 becomes an equiaxed structure, thereby providing Billet with good casting structure.

A method of continuously casting a magnesium billet or a magnesium slab using the apparatus 100 in the second embodiment will be described below.

In order to provide a cast billet or plate 106 with good surface quality and internal quality, a high frequency current of 50˜10,000 A and a frequency of 200˜200,000 □ is applied to the coil 102 .

In addition, a current of 20 to 1,000 A with a frequency of 2 to 100□ is applied to the electromagnetic stirring device 103 . The frequency of the coil or the electromagnetic stirring device is determined according to the size of the billet 106, and the intensity of the current is also determined according to the size of the cast billet or plate and the casting speed. According to the present invention, although the cast billet or sheet 106 as described above has a circular or rectangular cross-section, the billet may have other shapes.

Fig. 7 is an explanatory diagram comparing the surface of molten metal obtained by a conventional casting technique with the surface of molten metal obtained by applying a low-frequency current and a high-frequency current using the apparatus of the present invention.

Referring to Fig. 7, in a conventional casting operation, the surface of the molten metal is in contact with the mold at a right angle, so when the billet is produced while moving downward, severe friction occurs between the molten metal and the mold, making the casting The surface quality of the billet or plate deteriorates.

On the other hand, in the electromagnetic casting using the apparatus of the present invention to apply a high-frequency current, the penetration depth of the high-frequency electromagnetic field is very shallow due to the nature of the high frequency, and thus concentrates on the surface of the molten metal, making the molten metal The surface has an extremely large radius of curvature. Thus, the friction between the cast billet or slab and the mold can be reduced.

Therefore, since the electromagnetic force is concentrated on the surface of the molten metal, its stirring effect on the inside of the molten metal is small, so that the molten metal can be kept stable. However, because the internal quality of the molten metal cannot be improved due to the low stirring force on the molten metal, an electromagnetic stirring device is provided for the equipment of the present invention to improve the internal quality of the molten metal.

In addition, in the electromagnetic pouring using the apparatus of the present invention to apply a low-frequency current, the low-frequency electromagnetic field has a deep penetration depth and thus interacts with a deeper part of the molten metal, thereby improving the stirring effect. However, compared with high-frequency current, low-frequency current is less effective in improving surface quality. Regardless of the lower surface quality improvement effect, the device of the present invention using low-frequency current has the advantage of low device cost.

8a and 8b are photographs of the surface of the cast billet 106 produced after melting the AZ31 magnesium alloy. Figure 8a is a photograph of the surface of a cast billet 106 without an applied electromagnetic field according to conventional techniques. The cast billet 106 has many surface defects and cannot be produced by conventional casting operations.

Figure 8b is a photograph of the surface of a cast billet 106 to which an electromagnetic field has been applied according to the invention. The cast billet 106 has no surface defects and can be produced by increasing the casting speed to equal to or greater than 0.4 m/min.

Industrial Applicability

As can be clearly seen from the above description, the present invention provides the following beneficial effects: a magnesium or magnesium alloy cast billet or plate with improved internal quality can be produced at an accelerated casting speed without surface defects.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will understand that various changes, additions and substitutions can be made without departing from the scope and spirit of the present invention disclosed in the appended claims . It should be noted that these changes, additions and substitutions are included within the scope of the present invention.

Claims (14)

1. A device for continuously casting magnesium billets or magnesium plates utilizing an electromagnetic field, comprising: Molds for continuous casting of billets or slabs; a coil located outside said mould, allowing the application of electric current; Cooling nozzles located outside the mold and cast billet or sheet. 2. Apparatus as claimed in claim 1, characterized in that a low frequency current is applied to said coil, a replaceable ring being provided in the upper part within said mould. 3. The apparatus of claim 2, wherein the ring is made of graphite. 4. The apparatus of claim 1, wherein the mold has a circular or rectangular cross-section and the coil is disposed around the mold. 5. The apparatus of claim 1, wherein said cooling nozzles cool said mould, coil and casting billet or sheet by spraying water directly on them. 6. A method for continuously casting magnesium billets or magnesium slabs using an electromagnetic field, the method uses the equipment as claimed in any one of claims 1-5, wherein the coil applied frequency of the equipment in the casting process is 2 to 1,000□ current. 7. A device for continuously casting magnesium billets or magnesium slabs using an electromagnetic field, the device comprising: Molds for continuous casting of magnesium billets or slabs, the molds having slots formed therein; a coil located outside said mould, allowing the application of electric current; An electromagnetic stirring device located at the lower part of the mould. 8. The apparatus of claim 7, wherein the mold has sections separated by the slits in which cooling water channels are formed. 9. The apparatus of claim 8, wherein the slit is formed in a central region of the mold extending from below the upper end of the mold to above the lower end of the mold. 10. The equipment according to claim 8, wherein the slit has a width of 0.2-0.3□ and is filled with a vitrified bond so as to apply an electromagnetic field to the molten metal in the mold while preventing leakage of the molten metal. 11. The apparatus of claim 7, wherein said mold has a circular or rectangular cross-section, said coil being provided around said mold. 12. The apparatus of claim 7, further comprising a cooling nozzle located between the mold and the electromagnetic stirring device. 13. The apparatus of claim 12, wherein the cooling nozzles cool the cast billet or sheet by spraying water directly on it and the electromagnetic stirring device. 14. A method for continuously casting magnesium billets or magnesium slabs using an electromagnetic field, the method using the equipment described in any one of claims 7-13, wherein, during the casting process, the frequency of 200 to 200,000□ A current of 50-10,000A is applied to the coil of the equipment, and a current of 20-1,000A is applied to the electromagnetic stirring device of the equipment at a frequency of 2-100□.

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