JP2002192332A - Floating melting casting equipment - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To improve casting quality by reducing the falling distance of a molten metal in a levitation melting casting apparatus in which the molten metal is poured into a mold from a tap hole at the bottom of a crucible. A hollow cylindrical body is directly connected to a tapping hole at the bottom of a crucible, and a pull-out drive plug is slidably provided in the hollow portion. 14 is fitted to the tap hole 4. At the time of casting, the pull-out drive plug 14 is connected to the drive mechanism 16 via the drive rod 15.
The molten metal in the crucible 1 is drawn into the mold 11 and solidified by cooling to cast a cylindrical ingot. Since the molten metal is drawn into the mold 11 as the drawing drive plug 14 is lowered, almost no drop occurs between the tap hole 4 and the mold 11 and the quality of the molten metal is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a levitation melting casting apparatus for melting a metal material while floating the metal material from a crucible, and more particularly to an improvement in means for pouring a molten metal into a mold.

[0002]

2. Description of the Related Art In a levitation melting casting apparatus, a metal material is melted away from a water-cooled crucible or in a soft contact state, so that a high-purity molten metal can be formed without mixing of impurities.
It has features such as being able to dissolve high melting point metals and obtaining a uniform composition by electromagnetic stirring, and is suitable for dissolving active metals, high melting point metals, alloys, and the like. In such a levitation melting and casting apparatus, the technology of taking out the molten metal of the molten metal material from the crucible is important and various studies have been made. There is a method of pouring a molten metal into a mold from a gate, and this bottom tapping technique is disclosed in JP-A-5-15950 and JP-A-7-1995.
No. 245182.

FIG. 3 is a perspective view in vertical section showing an example of the above-mentioned conventional apparatus of the bottom tapping type. In FIG. 3, the crucible 1
Is provided with upper and lower two coils 2 and 3 on the outside, and a crucible-shaped bottom of the crucible 1 is provided with a tap hole 4. The crucible 1 is configured by arranging a plurality of segments made of copper in the circumferential direction, the segments are electrically insulated from each other, and each segment is cooled by water cooling. High-frequency currents are supplied to the coils 2 and 3 from the high-frequency power supplies 5 and 6, respectively, and the metal material 7 is melted in the crucible 1. The tap hole 4 is closed by a movable stopper 8 during melting of the metal.

When an electric current is applied to the coils 2 and 3, an eddy current is induced in each segment of the crucible 1, and an eddy current is also induced in the metal material 7 by a magnetic flux penetrating from a slit between the segments. . Since the directions of these eddy currents are opposite to each other on the facing surfaces as shown in the figure, the electromagnetic force acting between them becomes a repulsive force, and the metal material 7 floats away from the crucible 1. The metal material 7 is heated by Joule heat and melts in a floating state. The illustrated device is a two-coil, two-power-supply type, and the upper coil 2 is mainly used for heating, and the lower coil 3 is mainly used for levitation. In order to take out the molten metal from the crucible 1, as shown in FIG. 4, the lever arm 9 of the plug drive mechanism (not shown) is turned in the direction of the arrow, and the plug 8 attached to the tip is removed. As a result, the molten metal falls from the tap hole 4 as shown in the figure and flows into a mold (not shown).

[0005]

However, such a conventional bottom tapping type floating melting casting apparatus has the following problems. In other words, the molten metal is dropped from the tap at the time of tapping, but the drop distance from the tap to the bottom of the mold is long, and the flow of the free-falling water flows between the taps into a stable laminar flow. No. for that reason,
In some cases, a desired casting quality cannot be obtained. In such a case, the quality is improved by performing a hot working process such as hot forging after casting. In addition, the levitation melting casting apparatus is usually installed in a vacuum chamber. In particular, the apparatus having a swivel type plug driving mechanism as shown in the conventional example shown in FIG. The device becomes larger.

It is therefore an object of the present invention to improve the casting quality by minimizing the falling distance of the molten metal at the time of tapping and to reduce the volume of the vacuum chamber.

[0007]

In order to solve the above-mentioned problems, the present invention comprises a coil outside a crucible having a tap at the bottom, and a high-frequency current is passed through the coil to thereby form the crucible and its crucible. An eddy current is induced in the metal material inside, the metal material is floated from the crucible by the eddy currents, and heated and melted, and in the flotation melting casting apparatus in which the generated molten metal is poured into the mold from the tap hole, the mold is formed. By forming a hollow cylindrical shape and directly connecting to the tap hole of the crucible, a pull-out drive plug fitted to the tap hole is slidably provided in the hollow portion of the mold, and by pulling down the pull-out drive plug at the time of tapping, The molten metal is drawn into the mold and solidified by cooling (claim 1). According to the first aspect, the direct connection between the crucible tap and the mold eliminates useless space therebetween, and minimizes the falling distance of the molten metal. Also, by drawing the molten metal into the mold following the pulling-down operation of the pull-out drive plug, the molten metal can be poured into the mold in a laminar flow with almost no drop. Further, since the pull-out drive plug moves linearly in the mold, its drive space is small.

[0008] The pull-out drive plug can be made of the same material as the metal material. In that case, the upper part of the pull-out drive plug is configured to be removable and replaceable,
If the upper portion is formed of the same material as the metal material, the basic portion of the pull-out drive plug can be used repeatedly and is economical (claim 3). It is preferable that only the lower part of the pull-out drive plug is water-cooled (claim 4). Thereby, the upper portion of the pull-out drive plug is melted by the heat from the molten metal, and when the pull-out drive plug is lowered, the upper end portion is welded with the molten metal so that the molten metal can follow the pull-down drive plug lowering operation well. Can be.

Further, the pull-out drive plug can be made of a copper material. In this case, it is preferable that the entire pull-out drive plug is water-cooled (claim 6). Thus, a solidified layer is formed at a lower portion of the molten metal adjacent to the pull-out driving plug, and it is possible to improve the separation of the molten metal when the pull-out driving plug is lowered at a high speed.

Further, the mold is preferably water-cooled to promote solidification of the molten metal (claim 7). Further, it is preferable to arrange a coil for flowing a high-frequency current outside the upper end of the mold (claim 8). Thus, the molten metal in the crucible that receives heat from the mold can be reheated. In this case, a slit may be formed at the upper end of the mold in which the coil is disposed to help infiltration of magnetic flux from the coil (claim 9). Preferably, the slit extends below the lower surface of the coil, so that the penetration of magnetic flux is better (claim 10). On the other hand, it is preferable that the mold is electrically insulated from the crucible, thereby preventing a short circuit between the mold and the crucible and damage due to electric discharge.
1).

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS.
An embodiment of the present invention will be described. Here, FIG. 1 is a longitudinal sectional perspective view of the levitation melting casting apparatus during melting of a metal material, and FIG. 2 is a view of the apparatus of FIG. 1 during casting. Note that the same reference numerals are used for the portions corresponding to the conventional example. First, FIG.
, The crucible 1 is substantially the same as the conventional example, and is composed of a plurality of copper segments, and each segment is cooled by cooling water that is supplied and drained in the direction of the arrow through a water supply and drainage jacket 10 that is connected to the upper surface of the crucible.

Here, a mold 11 is directly connected to the tap hole 4 at the bottom of the crucible. The mold 11 is supported on a mold base 12 in the form of a hollow cylinder made of a copper material, and is electrically insulated from the crucible 1 by a minute space or an insulating material to prevent damage due to short circuit or electric discharge. In this case, the part 3a of the lower coil 3 arranged at the bottom of the crucible 1 is arranged outside the upper end of the mold 11, and in the upper part where the lower coil 3 is arranged, the part 3a is circumferentially attached to the mold 11. A plurality of slits 11a arranged in a line are cut in the axial direction, and the slits 11a extend below the lower surface of the coil 3a. Although the cooling pipe is not shown, the mold 11 is water-cooled. The slit 11a of the mold 11 may be provided in the entire axial direction. Also, mold 1
1 is not limited to a hollow cylindrical shape (the inner peripheral shape is circular), and the inner peripheral shape of the cylindrical body may be a polygon such as a quadrangle or a hexagon or any other shape.

In the hollow portion 13 of the mold 11, a pull-out drive plug 14 formed of a cylindrical body is provided so as to be slidable up and down. In the metal melting state shown in FIG. 4 and closes the tap hole 4. In this embodiment, since the mold 11 has a hollow cylindrical shape, the pull-out drive plug 14 is a cylindrical body (the outer peripheral shape is circular). It is decided together. Pull drive plug 1
4 is driven up and down by a drive mechanism 16 via a drive rod 15 slidably penetrating the mold base 12. The drive mechanism 16 includes a lift 17 connected to the drive rod 15.
Is moved up and down by an electric or hydraulic servo mechanism. Crucible 1, Coil 2, 3, Mold 1
1. The mold table 12 and the like are housed in a vacuum chamber 18, and the inside thereof is evacuated to a high vacuum atmosphere by a vacuum exhaust device 19. A space between the lift 17 and the vacuum chamber 18 is elastically closed by a bellows 20.

In such a floating melting casting apparatus, after the metal material 7 is melted, when the pull-out drive plug 14 is pulled down by the drive mechanism 16, the molten metal flows from the tap hole 4 into the mold 11 and solidifies. To form a cylindrical ingot. The ingot is taken out by pushing up into the crucible 1 with the pull-out drive plug 14 and pulling it out from above, or by splitting the mold 11 below the coil 3a. The details of the casting will be described below.

First, a method suitable for gradually cooling the molten metal during casting will be described. In this case, the pull-out drive plug 14
The same type of material (composite material) as the metal material 7 is used, and the pull-out drive plug 14 is not water-cooled, or only the lower part thereof is water-cooled. In the illustrated embodiment, the pull-out drive plug 14
The upper portion 14a is configured to be detachable from the lower base portion 14b so as to be replaceable, and only the upper portion 14a is formed of a common material. Upper part 1 of pull-out drive plug 14 made of common material
4a receives heat from the molten metal and is heated by the magnetic flux of the coil 3a penetrating from the slit 11a of the mold 11a, and changes from a molten state to a semi-molten state from the upper end face downward. The pull-out drive plug 14 is relatively slow, that is, 10 m if it is intended to form columnar crystals, depending on the metal, for example.
In the case where the formation of columnar crystals is not limited to m to 100 mm / hour, the drawing drive is performed downward at several tens to tens of thousands of mm / hour. As a result, while the molten metal is welded to the upper end surface of the pull-out drive plug 14, the mold 1
Heat is removed from the mold 11 while forming a laminar flow, and is continuously solidified.

FIG. 2 shows a state in which a common material is used for the pull-out drive plug 14 and the molten metal 7 is drawn into the mold 11 following the pull-out operation. This pull-out drive
At the start, if the liquid is pushed up slightly upward and then lowered, or if the intermittent operation or the reversible up and down operation is added to the continuous operation during the drawing, the molten metal can be drawn out smoothly. However, since the volume of the molten metal is reduced by solidification, the molten metal does not come into strong contact with the mold 11. Depending on the use conditions such as the type of the metal material and the melting temperature, if the lower part of the mold is tapered, the drawing can be performed more smoothly. The pull-out drive plug portion welded to the molten metal is cut and separated after casting.

Next, a method suitable for rapid casting will be described. In this case, the distraction drive plug 14 is made of a dissimilar metal material having a high thermal conductivity, for example, a copper material, and is entirely water-cooled from the upper portion to the lower portion. In this case, the portion of the molten metal facing the pull-out drive plug 14 is removed from the pull-out drive plug 14 to form a solidified layer. The pull-out drive of the pull-out drive plug 14 is performed at a relatively high speed, for example, 100 mm to 200 mm / sec. By this drawing, the molten metal does not lose heat from the pull-out drive plug 14, and the above-mentioned solidified layer is re-dissolved due to the eddy current flowing through the solidified layer. It flows into the mold 11 with a slight delay (for example, after a few seconds). Also in this case, the molten metal flows into the mold 11 as a laminar flow following the lowering of the pull-out drive plug 14, but the speed is larger than in the previous case, and the quenching is performed by one shot.

In the above embodiment, the pull-out drive plug 1
4 shows a case where the common material is used and the molten metal is gradually cooled by lowering it at a relatively low speed, and a case where a copper material is used for the drawing drive plug 14 and the molten metal is rapidly cooled by lowering the material at a relatively high speed. The material, the cooling range, the lowering speed and the like of the pull-out drive plug 14 can be appropriately selected depending on the type of the metal material 7 and the required casting quality, and are not limited to the above embodiment. In addition, the shape of the crucible 1 and the coils 2,
The present invention is applicable regardless of the number 3, frequency of the high-frequency current, and the mode of current control for discharging hot water from the bottom of the crucible.

[0019]

As described above, according to the present invention, since the tapping hole at the bottom of the crucible is directly connected to the mold, the tapping hole and the mold approach, and the molten metal is lowered as the pull-out drive plug which is lowered inside is lowered. Is drawn into the mold, so that the flow of the molten metal becomes a quiet laminar flow, and high-quality casting can be performed. The cooling rate of the molten metal can be adjusted by selecting the material of the pull-out drive plug, the cooling range, and the pull-out speed, and cast products in various crystalline states can be obtained. Further, since the pull-out drive plug has a linear motion, the required movable space is small, and the drive mechanism can be easily installed outside the vacuum chamber. In addition, the installation space of the entire apparatus can be reduced.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional perspective view of a levitation melting casting apparatus showing an embodiment of the present invention during melting of a metal material.

FIG. 2 is a diagram showing a state during withdrawal of the pull-out drive plug of the apparatus of FIG. 1;

FIG. 3 is a vertical cross-sectional perspective view of a conventional levitation melting casting apparatus during melting of a metal material.

FIG. 4 is a view showing a situation during tapping of the apparatus of FIG. 3;

[Explanation of symbols]

Reference Signs List 1 crucible 2 coil 3 coil 4 tap hole 5 high frequency power supply 6 high frequency power supply 7 molten metal material 10 water cooling jacket 11 mold 11a slit 13 mold hollow portion 14 pull-out drive plug 16 drive mechanism 18 vacuum chamber 19 vacuum exhaust device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B 6/32 H05B 6/32

Claims (11)

[Claims] 1. A coil is provided outside a crucible having a tap at the bottom, and an eddy current is induced in the crucible and the metal material therein by flowing a high-frequency current through the coil. Floating and melting the metal material from the crucible while heating and melting the molten metal, and pouring the resulting molten metal into the mold from the tap hole, wherein the mold is formed into a hollow cylindrical shape and directly connected to the tap port of the crucible. A pull-out drive plug fitted to the tap hole is slidably provided in the hollow portion of the mold, and the pull-out drive plug is lowered at the time of tapping, whereby the molten metal is drawn into the mold and cooled and solidified. A floating melting casting apparatus characterized by the following. 2. The levitation melting casting apparatus according to claim 1, wherein said pull-out drive plug is formed of the same material as said metal material. 3. The levitation melting casting apparatus according to claim 1, wherein an upper portion of the pull-out drive plug is detachably replaceable, and the upper portion is formed of the same material as the metal material. 4. The flotation melting casting apparatus according to claim 2, wherein only the lower part of the pull-out drive plug is water-cooled. 5. The levitation melting casting apparatus according to claim 1, wherein said drawing drive plug is made of a copper material. 6. The floating melting casting apparatus according to claim 5, wherein the entirety of the pull-out drive plug is water-cooled. 7. The flotation melting casting apparatus according to claim 1, wherein said mold is water-cooled. 8. The levitation melting casting apparatus according to claim 1, wherein a coil for flowing a high-frequency current is arranged outside the upper end of the mold. 9. The levitation melting casting apparatus according to claim 8, wherein a slit is formed in an upper end portion of said mold in which said coil is disposed. 10. The levitation melting casting apparatus according to claim 9, wherein said slit is extended below a lower surface of said coil. 11. The levitation melting casting apparatus according to claim 1, wherein said mold is electrically insulated from said crucible.