JPH0538555A - Apparatus and method for melting and continuously casting metal - Google Patents

Abstract

PURPOSE:To continuously cast an ingot having no defect by efficiently melting a metal having high m.p. and high reactivity with induction heating. CONSTITUTION:A crucible 2 divided into sectors with slit at upper part is set in a chamber 1 and coil type inductor 3 surrounding the crucible 2 is set and also a crucible lifting device 6, by which upper end face of the crucible 2 can be vertically shifted in the level range of upper end and lower end of the coil type inductor 3, is set. Then, after forming domy molten metal from a base material metal with induction heating, the upper end face of crucible 2 is held at level lower than the upper end level and higher than the lower end level of coil type inductor 3, and an ingot is produced at drawing speed corresponding to raw material supplying speed. The domy molten metal can be directly and efficiently heated from the coil type inductor 3 without intervention of the crucible sectors. Therefore, the ingot having no material defect and surface defect, can be produced in high productivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for melting a metal having a high melting point and a high reactivity in a state of being shielded from the atmosphere and continuously casting it by using a cooling type crucible which is induction-heated. Regarding the method.

[0002]

2. Description of the Related Art A method of melting by induction heating using a cooling type crucible and continuously casting is to melt a metal having a high melting point and high reactivity such as titanium, zirconium, hafnium or alloys thereof, It is used, for example, when manufacturing the ingot.

5 (a) and 5 (b) show US Pat. No. 3,775,091.
It is one of such cooled crucible devices disclosed in the specification. This device is a copper crucible that is arranged in a chamber 41 as shown in the figure, is divided by slits 42c and juxtaposed, and is composed of sectors 42d electrically insulated from each other.
42, a water-cooled coaxial spiral inductor 43 surrounding the outer side thereof, a withdrawal rod 45 of a cast ingot, and a feeder 44 of a slag agent and a raw metal. And the sector 42
Cooling water is caused to flow inside the d, and the coaxial spiral inductor 43
A medium or high frequency alternating current is supplied to the. Crucible
Since the wall of 42 is divided into sectors 42d, the alternating magnetic field of the coaxial spiral inductor 43 induces an electric current in the raw metal charged in the crucible 42, and the raw metal is heated, melted and stirred. The melted metal is cooled below the crucible 42 to form an ingot, which is drawn downward by a drawing rod 45.

Conventionally, in order to avoid direct contact between the molten metal and the crucible in this type of apparatus, an electromagnetic pinch force acting on the molten metal is utilized, and as shown in FIG. A slag layer is formed between the ingot and the ingot. However, the presence of this slag leads to metal contamination by the slag and corrosion of the crucible, and when the melting and casting operations are carried out under vacuum, the slag evaporates and the chamber
This causes an adverse effect such that it adheres to the inside of the 41, and further, the shape of the ingot is deformed during casting, and an extra step is required to peel off the slag adhered to the ingot. Further, since the contact between the ingot and the crucible wall is long, the tensile stress increases, which causes many problems such as promoting cracking of the ingot casting surface.

As an apparatus for solving the above-mentioned problems, FIG. 6 disclosed in French Patent No. 2609655.
There is a device. This device is generally similar to that of U.S. Pat. No. 3,775,091 except that the inner cross-sectional area of the crucible 52 expands downward and no slag is used. By controlling the current value supplied to the inductor 53 as shown in the figure, the molten metal is held above a level slightly higher than the junction between the upper region of the uniform cross section of the crucible 52 and the lower region of the divergent cross section, Prevent the molten metal from coming into contact with the crucible wall electromagnetically. At this time, since the lower region of the crucible 52 is divergent, the molten metal comes into contact with the crucible wall and solidifies in the upper region slightly below the level. Therefore, the solidified metal is not contaminated by the metal of the crucible 52 without using slag, and there is no large tensile stress between the ingot and the crucible wall, so that the ingot can be easily pulled out and a good surface condition can be obtained.

However, when the melting rate is increased to improve productivity, phenomena such as adhesion of unmelted raw material on the solidified surface become remarkable, surface defects of the ingot due to increased tensile stress, unmelted raw material, segregation of alloy components Material defects such as are likely to occur.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the problem of efficiently inductively melting a metal having a high melting point and a high reactivity to continuously produce an ingot having no surface defects or material defects. It is an object of the present invention to provide a melting and casting apparatus and a melting and casting method using the same, which do not have the above-mentioned problems in the conventional method using the cooling type crucible apparatus.

[0008]

One of the present inventions is shown in FIG.
(A), (b) and FIG.
The following equipment is the gist.

A vertical conductive crucible 2, a coil-shaped inductor 3 surrounding the crucible, a pull-out rod 5 for supporting the ingot and pulling it downward, and a crucible lifting device 6 described above. The crucible 2 has a chamber 1 for blocking all of the above from the atmosphere, and the crucible 2 has a plurality of vertically extending slits 2c whose walls are filled with an electric insulating material.
The upper member 2a having a segment structure divided into 2d, and the lower member 2b having an integral structure which is not divided into sectors joined to the upper member, and the upper member and the lower member are internally connected to each other for cooling. There is a medium flow passage 2f,
The crucible lifting device is capable of moving an upper end of the crucible up and down between an upper end and a lower end of the coil-shaped inductor.

Another aspect of the invention features the following method of using the above apparatus.

First, the metal base material charged in the crucible is induction-heated and melted to form a dome-shaped molten metal that rises above the upper end surface of the crucible, and then the upper end surface of the crucible is set to the upper end of the coil-shaped inductor. It is maintained at a level lower than the level and higher than the lower end level to supply the raw material metal to the dome-shaped molten metal, and the ingot is drawn downward at a drawing speed corresponding to the material supply speed. Continuous casting method.

[0012]

The device and method of the present invention will now be described in detail with reference to the drawings.

FIG. 1 (a) is a longitudinal sectional view of an example of the device of the present invention,
FIG. 1B is a horizontal sectional view taken along the line AA of FIG.
FIG. 2 is a partial cross-sectional perspective view of the crucible portion of the device of the present invention.

In these figures, 1 is an exhaust port 1a at the bottom.
A chamber having a vertical shape and the same cylindrical crucible 2 is installed therein, and a coil-shaped inductor 3 is provided so as to surround the crucible 2. The coil-shaped inductor 3 is connected to a power source by a lead wire (not shown), and conduits (not shown) are connected to the water supply port 2h and the drain port 2i.

A vibrating feeder 4 for supplying the raw material metal R is disposed above the crucible 2, and a pull-out rod 5 is provided below the vibrating feeder 4 for supporting the solidified ingot melted in the crucible 2 and pulling it downward. There is.

The crucible 2 is made of a conductive material, such as copper, and is composed of an upper member 2a and a lower member 2b. As shown in FIG. 2, the structure of the upper member 2a is a segment structure in which a plurality of sectors 2d divided by vertically extending slits 2c are arranged in a cylindrical shape, and a gap between the slits 2c is filled with an electric insulating material. It A cooling water passage 2f is provided inside each sector. The lower member 2b has a cooling water passage 2e, 2g in which a hollow right circular cylindrical hollow body is double formed, and has an integral structure that is not divided into sectors. The water supply port 2h and the water discharge port 2i are connected to a flexible bellows copper pipe (not shown) so as not to hinder the raising and lowering of the crucible 2. The cooling water supplied from the water supply port 2h to the cooling water passage 2e of the lower member 2b is discharged to the drain port 2i via the cooling water passage 2f of each sector 2d of the upper member 2a and the cooling water passage 2g of the lower member 2b. .. The lower end of the crucible 2 is placed on the crucible support plate 2k via the electric insulating material 2j.

The crucible lifting device 6 is, for example, a crucible support plate.
It is composed of a female screw member 6a attached to 2k, a male screw rotating rod 6b, a rotating rod supporting plate 6c, and a rotating mechanism 6d. Female thread member
Four pieces of 6a are mounted on the crucible supporting plate 2k with center symmetry. A thrust ball bearing 6e is attached to the upper and lower ends of the male screw rotating rod 6b, and the upper and lower parts are fixed by rotating rod support plates 6c provided on the upper and lower ends. A rotation mechanism 6d, for example, a bevel gear 6f and a transmission (not shown), a clutch, a rotation motor, and the like are attached to the male screw rotation rod 6b. By rotating the rotary rod 6b in this manner, the support plate 2k is moved up and down by the pinion-rack mechanism, and the crucible 2 can be moved up and down by a predetermined distance.

Next, a method for manufacturing an ingot by melting the raw material metal R using the above apparatus and performing continuous casting will be described.

First, after fixing the base material of the ingot to the tip of the drawing bar 5, the drawing bar 5 is raised and inserted until the upper end of the base material almost coincides with the intermediate height of the coil-shaped inductor 3, and the crucible. The crucible 2 is placed where the upper end of 2 corresponds to the middle height of the coiled inductor 3. However, it is not necessary to specifically limit the arrangement position of the crucible 2 at the stage of starting the operation.

Next, when cooling water is supplied from the water supply port 2h of the crucible 2 and a medium-wave or high-frequency alternating current is supplied to the coil-shaped inductor 3, the induced current is supplied to the inner surface of the crucible 2 via the sector 2d of the crucible 2. Flows, the base material is heated, and is eventually melted, and at the same time, the molten portion is dome-shaped bulged by the action of the electromagnetic pinch force. Thereafter, while monitoring the crucible 2 with a TV motor, the crucible elevating device 6 is used to slowly raise the crucible 2 upward so that the upper end surface of the crucible 2 is lower than the center level of the coil-shaped inductor 3 and the lower end. Keep level higher than level.

In such a state, as shown in FIG. 3, the melting operation is performed without interposing a crucible sector between the coil-shaped inductor and the dome-shaped molten metal.

Then, the raw material metal R is supplied to the dome-shaped molten metal formed on the upper end of the base material, and the drawing rod 5 is lowered at a speed corresponding to the raw material supply speed to bring the dome-shaped molten metal to a predetermined position. The ingot is manufactured while holding.

During the above series of operations, the closed chamber 1
The atmosphere inside can be adjusted arbitrarily. It is usually operated in Ar gas or vacuum atmosphere. Therefore, even a highly reactive metal can be dissolved without causing oxidative contamination.

FIG. 3 is a diagram schematically showing the dome-shaped formation of molten metal when the method of the present invention is carried out. As shown in the figure, since the crucible 2 does not exist on the inner front surface of most of the coil-shaped inductor 3, the dome-shaped molten metal M and the coil-shaped inductor 3 have a direct electromagnetic interaction.
Therefore, the electromagnetic energy distributed to the crucible is reduced,
The heating efficiency of the dome-shaped molten metal M is increased, and the productivity of the device is improved.

Since most of the sector 2d is arranged in a region below the contact point between the dome-shaped molten metal M and the inner wall of the sector 2d, which is almost coincident with the starting point of the solidified shell, the dome-shaped molten metal M has the above-mentioned contact point. The vibrating molten metal surface 7a which is the starting point is generated.
However, even if an instability phenomenon such as vibration occurs on the molten metal surface 7 in this way, the force to push back from the coil-shaped inductor 3 to the central portion works, so that molten metal spills or the coil-shaped inductor 3 and the dome shape. The molten metal M does not directly contact with each other to generate a spark, and safe and stable production can be performed.

FIG. 6 is a diagram showing the state of formation of dome-shaped molten metal when a conventional cooling type crucible apparatus is used. In this method, the upper end of the crucible 2 is set so as to substantially coincide with the upper end of the coil-shaped inductor 3. In this case, the vibrating molten metal surface 7a of the dome-shaped molten metal M comes into contact with the inner wall of the sector 2d to fix the solidified shell 8, and eventually grows and sticks to the surface of the ingot I, increasing the tensile stress of ingot drawing. Surface defects such as cracks occur in the ingot I. Further, a sector is provided between the coil-shaped inductor 3 and the dome-shaped molten metal M.
Since 2d intervenes and electromagnetic energy loss occurs in sector 2d, heating efficiency decreases. Therefore, if the production rate is increased, undissolved raw materials are likely to occur, and material defects such as segregation of alloy components are likely to occur during alloy production.

Hereinafter, the method of using the device of the present invention and its effects will be described in detail with reference to examples.

[0028]

EXAMPLE A titanium ingot was manufactured using the apparatus shown in FIG. 1, and its purity and surface properties were examined.

The crucible 2 has an inner diameter of 60 mm, an outer diameter of 100 mm, and a height of 1.
It is made of 80 mm copper. The upper member 2a of the crucible 2 having a segment structure is composed of 16 sectors of internal water-cooling structure 2d with a height of 120 mm, and the gap between adjacent sectors is 0.8 mm and is filled with an insulator such as mica or alumina.

The height of the lower member 2b of the crucible 2 having the segment structure is 60 mm. The coil-shaped inductor 3 has a wall thickness of 2
2 mm crucible with an outer diameter of 12 mm and an average diameter of 120 mm
It has a structure in which it is spirally wound seven times. Further, a vibrating feeder 4 for supplying the raw material titanium R is provided above the crucible 2, and a pull-out rod 5 is arranged below the crucible 2 to continuously draw the cast titanium ingot I downward.

The melting and casting operations were carried out as follows.
First, after making the chamber 1 into an Ar gas atmosphere, the extraction rod 5 is inserted into the crucible 2 and the titanium base material placed on the upper end of the extraction rod 5 is adjusted so that the upper part thereof is in the middle of the height of the coil-shaped inductor 3. The charging was carried out so that the upper end of the crucible 2 was aligned with the upper end of the coil-shaped inductor 3. And coiled inductor 3
A high-frequency current with a frequency of 20 kHz and a current of 1500 A was supplied to.
After 5 minutes, the titanium base material was melted and raised in a dome shape. Therefore, the raw material was supplied and the crucible was lowered by 40 mm without changing the molten metal level. The upper end surface of the crucible 2 was held at a level 50 mm above the lower end level of the coil-shaped inductor 3. After that, the raw material titanium R was supplied from the vibrating feeder 4 at 200 g / min while lowering the pull-out rod 5 at a speed of 1.6 cm / min. Do this for 36 minutes, diameter 58mm, length
An ingot weighing 576 mm and weighing 6.5 kg was manufactured.

As a result of examining the chemical composition of this titanium ingot, oxygen 2,000 ppm, carbon 230 ppm, nitrogen 105 ppm, copper 20 pp
Below m, the balance was titanium and the purity was very high. The surface properties were also very good.

[0033]

By using the apparatus of the present invention, metal can be melted without causing electromagnetic energy loss, and continuous casting can be carried out without using a slag agent. Therefore, it is possible to manufacture a good product without material defects such as unmelted raw material and segregation, or ingot surface defects such as cracks, with high productivity, and it is possible to reduce the ingot maintenance cost and improve the product yield. Is obtained.

[Brief description of drawings]

FIG. 1 (a) is a vertical sectional view showing an example of the device of the present invention.

1 (b) is a horizontal sectional view taken along the line AA of FIG. 1 (a).

FIG. 2 is a partial cross-sectional perspective view of the crucible portion of the present invention.

FIG. 3 is a diagram showing a dome formation state of molten metal when the present invention is carried out.

FIG. 4 is a view showing a dome formation state of molten metal when a conventional cooling type crucible device is used.

FIG. 5 is a view showing an example of a conventional cooling type crucible device.

FIG. 6 is a view showing another example of a conventional cooling type crucible device.

[Explanation of symbols]

1: chamber, 1a: exhaust port, 2: crucible, 2
a: Upper member, 2b: Lower member, 2c: Slit, 2
d: sector, 2e, 2f, 2g: cooling water passage, 2h: water inlet,
2i: Drainage port, 2j: Electrical insulating material, 2k: Crucible support plate, 3: Coil type inductor, 4: Vibrating feeder, 5:
Drawing bar, 6: Crucible lifting device, 6a: Trapezoidal female screw member, 6b: Trapezoidal male screw rotating rod, 6c: Rotating rod support plate,
6d: rotating mechanism, 6e: thrust ball bearing, 6f: bevel gear,
7: molten metal surface, 7a: vibrating molten metal surface, 8: solidified shell

Claims (2)

[Claims] 1. A vertical conductive crucible, a coil-shaped inductor surrounding the crucible, a pull-out rod for supporting an ingot and pulling it downward, an elevating device for the crucible, and The crucible has a chamber for shutting everything off from the atmosphere, and the crucible has an upper member having a segment structure in which the wall is divided into sectors by a plurality of vertically extending slits filled with an electric insulating material, and the upper member. The upper member and the lower member each have a cooling medium flow passage connected to each other, and the crucible lifting device includes: A metal melting and continuous casting apparatus, wherein the upper end can be moved up and down between the upper end and the lower end of the coil-shaped inductor. 2. The apparatus according to claim 1, wherein the metal base material charged in the crucible is heated and melted to form a dome-shaped molten metal rising above the upper end surface of the crucible, and then on the crucible. Hold the end face at a level lower than the upper end level of the coil-shaped inductor and higher than the lower end level to supply the raw material metal to the dome-shaped molten metal and pull out the ingot downward at the extraction speed corresponding to the raw material supply speed. A method for melting and continuously casting metals.