JPH0331770B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plasma melting apparatus that melts raw materials placed in a molten metal pool using a plurality of plasma torches.

In the plasma melting apparatus described above, due to the nature of the plasma torch, multiple plasma arc irradiated parts in the molten metal pool melt rapidly, but between the arc irradiated parts, the raw material melts slowly and remains unmelted. There were some problems.

Accordingly, the present invention provides a plasma melting apparatus configured to allow a plurality of plasma torches to be lightly rotated to enable homogeneous melting of raw materials on the molten metal pool.

Next, embodiments of the present application will be described.

First, a stacked solidification type plasma titanium melting furnace (hereinafter referred to as
This section explains the outline of the PPC melting furnace (abbreviated as PPC melting furnace).

(a) Plasma arc melting Plasma arc is an arc generated between electrodes that is surrounded by a gas flow and contracted by the action of thermal and magnetic pinches to increase its temperature.
In practice, a plasma torch is used in which a water-cooled tungsten rod is used as a cathode, surrounded by an insulated water-cooled copper nozzle, and a working gas is flowed through the gap and ejected from the hole in the nozzle.

Based on this principle, the melting torch is designed to withstand the harsh environment inside the furnace and generate a stable and powerful plasma arc by devising power supply, air supply, water supply and drainage, and has the following characteristics.

(a) Generates extremely high temperatures of 12000℃.

(b) Aims toward the heated object with good directionality and is stable against changes in arc length and atmospheric pressure.

(c) Operated with inert argon gas.

(d) Fine adjustment of output is easy.

(e) A soft plasma arc is generated, with less scattering of heated objects and less noise.

(f) Generates the desired output at large currents and has good heat transfer.

(b) Characteristics of PPC melting PPC melting is a technology developed especially for melting active metals such as titanium and their alloys, in which the raw materials that are continuously charged into a water-cooled crucible are melted by a plasma arc, and the crucible is simultaneously melted. This is a continuous melting and casting process in which a layered and solidified ingot is obtained by pulling down the bottom of the ingot.

The combination of a non-consumable plasma torch, a water-cooled metal vessel, and an argon atmospheric pressure atmosphere allows PPC melting to:

(a) Raw materials can be melted and cast without contamination.

(b) There is no loss or fluctuation due to evaporation of raw materials or alloying components.

(c) Raw materials in various shapes can be used as they are, and slag for refining can also be added.

(d) Power can be adjusted freely, and melting conditions and solidification conditions can be set arbitrarily.

(e) Uniform heating can be obtained, the molten metal can be kept shallow, and good layered solidification is possible.

(c) Next, virgin raw materials (sponge titanium, additive alloys, etc.) as well as various scraps such as wire rods, plate cuts, and die plates are melted as raw materials, and the obtained ingots and VA remelted ingots are detailed. The results of the survey are as follows.

(a) PPC can be dissolved even with 100% scrap.

(b) There is no increase in impurities.

(c) In PPC melting, low-speed or high-speed melting is possible, and a sufficiently dense electrode for VA can be obtained.

(d) PPC dissolution removes the magnesium chloride contained in the sponge, making VA dissolution more stable and easier than usual.

(e) The secondary ingot exhibits the same appearance, composition, cleanliness, degree of segregation, and mechanical properties as the material melted by VA or more. This leads to the conclusion that the process of PPC primary melting + VA remelting produces superior quality ingots more economically.

(d) Next, we will explain the points to keep in mind when designing a PPC melting furnace.

When designing, we not only maximized the features of PPC melting mentioned above, but also paid careful attention to productivity, safety, operability, and maintainability, and provided the following features.

(a) Addition of raw materials, melting, and casting are all carried out in the same airtight structure as the vacuum vessel.

(b) The atmosphere can be completely replaced with argon gas by evacuation.

(c) Virgin materials and scrap can be continuously and smoothly supplied from the outside using two feeders.

(d) The raw material passage is wide, and raw materials can be added softly centered around the crucible.

(e) The plasma arc automatically rotates around the crucible, and the effect of the stirring coil is added to heat a wider area.

(f) There is no need to lift or lower the torch to stop arc generation.

(g) The crucible is replaceable and the ingot size can be changed.

(h) The ingot chamber is small due to the multi-stage cylinder type ingot lowering.

(i) It has four safety measures against abnormal pressure increase inside the reactor: a relief valve, a rupture port, automatic crucible separation, and an explosion-proof wall.

(j) All operational operations and monitoring of conditions inside the reactor are conducted remotely, and each operation is automated.

Next, an example of the configuration, operation, and specifications of the embodiment will be explained.

This furnace consists of the main body (raw material storage tank, melting chamber, crucible, ingot chamber), raw material supply equipment (weighing machine, belt and bucket conveyor, moving hopper, drum feeder, seat), vacuum exhaust equipment (oil rotary pump,
It consists of a mechanical booster pump), oil supply equipment, air supply equipment (argon and air), water supply and drainage equipment, and electrical equipment (plasma DC power supply, power panel, relay panel, plasma control panel, furnace body operation panel). The basic specifications of this furnace are as follows.

(a) Application Production of titanium ingots for consumable electrodes (b) Model PPC-2000T (c) Melting raw materials Titanium sponge, master alloy, titanium or alloy scraps (up to 80 mm square) (d) Ingot dimensions Diameter 355 mm and 435 mm maximum length
3000mm (cylindrical) (e) Ingot weight Maximum 2000Kg (f) Plasma output 540kW (g) Melting atmosphere Argon gas (atmospheric pressure) (h) Raw material feeder Rotating drum (260Kg/unit x 2)
(i) Ultimate vacuum level 1.3Pa (j) Main power supply for utilities: 3-phase, 60Hz, 3300V, 1220kVA Cooling water: 1.2m ³ /min Compressed air: 5m ³ _N /Charge (maximum 1.5m ³ _N /
min) Argon gas: 0.3 to 0.7 m ³ _N /min during melting, maximum 1 m ³ _N /min x 8 min during gas replacement Next, each part of the above furnace will be explained in order.

(A) Raw material supply Raw materials are first put into an automatic weighing machine with an accuracy of ±0.05%. The weighing machine cuts out titanium and two types of alloy base materials from their respective storage hoppers using an electromagnetic feeder, and weighs them in 20 kg units at a time using a load cell to achieve a predetermined blending ratio. After weighing, the three brands of raw materials are mixed and cut onto a belt conveyor, conveyed on the floor, and led to a bucket conveyor. This conveyor transports raw materials to the drum feeder installed above the furnace body.
It consists of several buckets, each of which receives 20 kg of raw materials. The operation up to this point is called bucket charging and is performed automatically. When this is completed, the charging side door of the drum feeder opens, the movable hopper moves to the opening, and the raw material in the bucket is fed into the drum feeder. The drum feeder is
It is a cylindrical airtight container with an inner diameter of 1100 mm and a length of 3800 mm, with a rotating drum that is almost inscribed inside it. The inner surface of the rotating drum has a spiral partition. The partition is within the entire length of the drum.
It has 13 pitches. The drum charging operation automatically charges 20 kg of raw material into each pitch.
Therefore, the drum is charged at a total of 13 locations along the entire length of the drum. When drum charging is complete, the hopper is evacuated, the charging side door is closed, and the interior is evacuated to 6.5 Pa, after which argon is introduced to atmospheric pressure. When melting begins and it is time to supply raw materials, the seal valve on the cut-out side of the drum feeder opens, and the raw materials in the partition are mixed by the rotation of the drum and moved to the outlet, where cut-out begins. The cut raw material passes through the chute and heads to the raw material storage tank inside the melting chamber. The raw material is braked here, slowing down, and falling directly into the center of the crucible. The rotating drum is 0~
The speed can be finely adjusted within a range of 0.4 rpm, and the raw material path leading to the crucible is over 140 mm, so raw materials of various shapes can be supplied quantitatively and smoothly. There are two drum feeders, and while one is cutting, material is charged to the other, and the feeder is switched every 260 kg. This repeated operation is called raw material supply and is automated, including gas replacement. In addition, the charging status of raw materials in each bucket or drum is displayed graphically in the control room.
You can check the remaining amount at a glance.

(B) Melting and casting The furnace shell of the melting chamber has an inner diameter of 1700 mm, a height of 1200 mm, a water-cooled jacket structure with an inner surface made of stainless steel and an outer surface made of mild steel, and is divided into upper and lower parts. A raw material storage tank is inserted into the central opening at the top, and 6
A book plasma torch is installed symmetrically towards the inside of the crucible. At the bottom, an ignition rod for generating a plasma arc is attached so that it can be moved in and out just below the torch. The lower part is fixed to the floor and supports the entire melting chamber, and the upper part is supported by rollers and can rotate around the raw material storage tank, allowing the six torches to be rotated up to ±60 degrees.
It can turn at speeds up to 1 rpm. A hydraulic cylinder is used for this turning, and the connections are specially designed to ensure smooth turning and airtightness.

The crucible has a jacket-type water-cooled structure with copper on the inside and stainless steel on the outside. It has a solenoid coil inside that generates direct current and low frequency alternating current magnetic fields.

The ingot chamber has an inner diameter of 900 mm and an inner height of 5500 mm, has an ingot lowering device inside, and is supported on a truck by four hydraulic jacks. A crucible is placed on top of the ingot chamber, and the crucible is connected to the melting chamber by the upward movement of a hydraulic jack and the subsequent force of a spring. The ingot lowering device consists of a multi-stage hydraulic cylinder and a stub clamp attached above it. Prior to melting, the stub left by VA melting is clamped and the multistage cylinder is placed inside the stretching crucible.

To begin melting, first evacuate the furnace. 7500/min oil rotary pump and 1500m ³ /h
A mechanical booster pump was used to pump the air to 6.5Pa in 13 minutes. Afterwards, argon is introduced and maintained at atmospheric pressure. These operations are automatically performed when the furnace body is replaced with argon.

Next, we will supply water and power, prepare the melting system, and move on to plasma arc ignition. By igniting the torch, the ignition rod is automatically inserted, the pilot arc is ignited, the main arc is generated, and the ignition rod is retracted, and the plasma arc is directed into the crucible and the stub end face begins to melt. The melting status is shown in two colors.
ITV provides detailed information in the control room.
To supply power to the six torches, a dedicated DC power supply consisting of a high-voltage power receiving board, a power factor correction capacitor board, one high-voltage transformer each, and six thyristor boards with ignition circuits is used. It has excellent constant current and soft start, can output either 6 individual circuits or 3 circuits in parallel, and can adjust the current of multiple torches over a wide range with a single setting device.

When the end face of the stub is melted and a molten metal is formed, the raw material is added to the center of the molten metal by the above-mentioned raw material supply operation, and then the multi-stage cylinder starts to descend at a low speed by the ingot lowering operation. As it progresses, the lower part of the molten metal is cooled in the crucible, and the laminated solidified ingot that has grown gradually is drawn out into the ingot. During this time, the plasma arc rotates by the automatic rotation of the torch while the direction of the arc is controlled by the magnetic field generating coil, and the entire inside of the crucible is irradiated to rapidly melt the added raw material. The molten metal is also subjected to the stirring force of the magnetic field, and is heated evenly.

The ingot withdrawal amount is displayed graphically on the operation panel by receiving a signal from a stroke meter installed in the ingot chamber.
The melting speed is determined by adjusting the rotational speed of the drum, and the ingot drawing speed is set accordingly, but once the operator has set it, there is almost no need to perform any operations. There is also almost no need to operate the torch, other than the initial power adjustment to control the water temperature. Therefore, this furnace can be operated by one worker.

In the production of titanium ingots for consumable electrodes, the true specific gravity is
Raw materials can be fed at high speeds to obtain ingots with a specific gravity of 90%. Therefore, when producing an ingot with a diameter of 435 mm, it is possible to melt at a rate of more than 300 kg/h, and the power consumption can be less than 1,800 kWh/t.

During melting, the atmosphere inside the furnace is constantly monitored by a dew point meter, and if the pressure inside the furnace rises abnormally for some reason, the relief valve opens, and when the pressure rises further, the crucible is automatically separated from the melting chamber, and the melting chamber The explosion-proof port installed in the reactor is destroyed and the pressure inside the reactor is released.
Workers do not have to enter the explosion-proof wall around the reactor body during operation, so they are not in any danger.

(C) Removal of the ingot When a predetermined amount of melting is completed, the cooling process is automatically started by stopping the arc, and the ingot is cooled while maintaining the argon atmosphere, after which it is replaced with air. After cooling, the crucible and ingot chamber are placed on a trolley by operating the ingot chamber lifting jack, and moved horizontally by hydraulic drive to the ingot removal position. The crucible is removed with a crane, the stub clamp is released, and the ingot is lifted out with a crane. The removed ingot is turned upside down and the stub portion is clamped in a VA furnace, where it is remelted as a consumable electrode.

(D) Melting cycle time An example of a series of work times for dissolving PPC is shown below.

● Ingot removal and preparation for melting; 72 minutes ● Raw material charging into the vat; 12 minutes ● Raw material drum charging; 10 minutes ● Argon replacement in the melting furnace body; 14 minutes ● Melting and casting; 300 to 400 minutes ● Cooling and air replacement ;265 minutes In other words, one melting cycle takes 11 to 13 hours, and monthly production of 75 tons or more is possible with three-shift operation.
This furnace can of course be applied to other active metals such as niobium and zirconium, and is also effective as a primary melting furnace for various functional materials (hydrogen storage alloys, shape memory alloys, superconducting alloys, etc.).

Next, the melting and casting apparatus will be explained based on the drawings. As shown in FIG. 1, the apparatus includes a raw material supply facility A, a plasma melting device B, and a casting device C. First, in the raw material supply facility A, the bucket conveyor 11 has 13 buckets 12, and after receiving the raw material weighed by a weighing device (not shown) into the buckets 12, it is transferred to the upper hopper 1.
Transport towards 3. A drum feeder 15 used as a raw material supply device is provided on a frame 14 constructed next to the conveyor. Two drum feeders 15 are provided side by side (the other is hidden behind the one shown in FIG. 1).
A charging port 16 is provided at one end of each drum feeder 15.
The hopper 13 is equipped with a hopper 13 and is capable of receiving raw materials. The charging port 16 is closed with a door when raw materials are not being charged. Further, a chute 17 is connected to the other end of the drum feeder 15.

Next, in the plasma melting apparatus B, a melting chamber 20 is fixed to the frame 14 at a position below the drum feeder 15. The melting chamber 20 is constructed to be able to be sealed internally, and is provided with a raw material charging section 21 in the upper center. The upper part of the charging part 21 is covered by an airtight surrounding part 22, so that the melting chamber 20 can be kept in a sealed state. Further, the airtight enclosure portion 22 is connected to the chute 17 . On the other hand, below the charging section 21, a guide tube 23 integrally formed with the airtight surrounding section 22 hangs down, and the raw material charged from the chute 17 toward the charging section 21 is guided by the guide tube 23. It is designed so that it falls into the center of the crucible, which will be described later. Six plasma torches 24 are attached to the melting chamber 20 around the charging section 21. These plasma torches 24 are mounted at intervals of 60 degrees from each other, and the internal cathodes of each are connected to the negative terminal of a dedicated DC power supply. A support rod 25 is provided at the bottom of the dissolution chamber 20 so as to be freely movable left and right in the figure. An arching piece 26 is attached to the tip of the support rod 25. Further, the rear end of the support rod 25 is connected to a reciprocating device 27 so that the support rod 25 can move in the above-mentioned direction.

Next, the casting apparatus C will be explained. This casting device C is provided inside the pit 31. A supporting leg 32 is provided at the bottom of the pit 31, and a long rail 33 is provided above the supporting leg 32 in a direction perpendicular to the plane of the paper in FIG. The trolley 34 has wheels 3
4a, so that it can move along the rail 33. A hydraulic jack 35 is attached to the truck 34, and an ingot chamber 36 is attached to its piston rod via a bracket 35a. A crucible 37 is provided in the upper part of the ingot chamber 36, and the crucible 37 fits into a through hole formed in the lower part of the melting chamber 20. As is well known, the crucible 37 forms a molten metal pool therein. An ingot pulling device 38 is provided inside the ingot chamber 36. This pulling device 38 is constructed with a multi-stage cylinder. A stub clamp 39 is provided at the upper end of the pulling device 38, and a stub 4 constituting the crucible bottom inside the crucible 37 is attached to the stub clamp 39.
0 is attached, and the stub clamp 39 is provided with a power supply terminal for supplying power to the stub so that it can be connected to the positive terminal of the DC power supply of each plasma torch.

Next, the operation of the above-mentioned structure will be explained step by step based on FIG. In FIG. 2, the drum feeders 15 are shown side by side for ease of understanding. First, as shown in FIG. 2A, raw materials are charged into each drum feeder 15 with the seal valve 43 on the outlet side of each drum feeder 15 closed, and the internal space thereof is replaced with argon gas. Further, with the seal valve 43 closed, the interiors of the melting chamber 20 and the ingot chamber 36 are evacuated, and argon gas is further fed to a pressure of 1 atmosphere. Next, as shown in FIG.
Move it below 4. Next, as shown in C, a plasma arc is ignited between the arc ignition piece 26 and each plasma torch 24. Next, as shown in D, the arcing piece 26 is laterally retracted from below each plasma torch 24 to form a main arc from each plasma torch 24 toward the stub 40. In this state, the upper end of the stub 40 is melted by the plasma arc, and a molten metal pool 37a is formed there. Next, as shown in E, the seal valve 43 in one drum feeder 15 is opened, and the raw material is fed into the charging section 21 of the melting chamber 20 via the chute 17. The raw material is guided by the guide tube 23 and falls toward the center of the molten metal pool 37a. The fallen raw material is then melted by a plasma arc from the plasma torch 24. When the raw materials are sequentially melted as described above, the lowering device 38 is operated to lower the stubs 40 one after another. The speed of the descent is the molten metal pool 37
The speed is such that the upper surface of the crucible is always at a constant height, that is, the speed is set to correspond to the amount of the raw material charged into the crucible per unit time. By continuing such operations, the molten material created by melting the raw material charged earlier into the crucible is cooled by the water-cooled crucible 37 and becomes an ingot 44 integrated with the stub 40. As the stub 40 descends, the ingot 44 is successively pulled out downward and becomes longer as shown in FIG. 2E. When the raw material in one drum feeder 15 is completely supplied to the melting chamber while continuing the above operations, the seal valve 43 of that drum feeder 15 is closed as shown in F, and the seal of the other drum feeder 15 is closed. Open the valve 43 (in this case, the inside of the drum feeder 15 on the side where the seal valve 43 is opened has been replaced with argon gas in advance),
The raw material is supplied from the drum feeder 15 to the melting chamber 20 in the same manner as in the above case. Then, the empty drum feeder 15 is again charged with raw material from the bucket conveyor 11. By repeating the above operations, when an ingot 44 of a predetermined size is formed as shown in G, the supply of raw materials to the melting chamber 20 is stopped, and the generation of plasma arc is also stopped. Thereafter, the ingot 44 is cooled while the inside of the ingot chamber 36 is kept in an argon atmosphere. When the ingot 44 has cooled to a temperature at which it will not oxidize even when exposed to air, the inside of the ingot chamber 36 is replaced with air. Thereafter, as shown in H, the ingot chamber 36 and crucible 37 are separated from the melting chamber 20, and moved to the ingot removal position using the cart 34. Thereafter, as shown in H, the crucible 37 is removed by the crane 42, the stub clamp is released, and the ingot 44 is lifted out by the crane. The removed ingot 44 is then charged upside down as shown in I into a well-known remelting furnace, and the ingot is remelted as a consumable electrode, and then remelted as shown in J. An ingot 45 is formed. In this case, remelting is performed until a portion to be reused as the stub 40 remains. The remaining stub 40 is loaded into the ingot pulling device 38 again, and
It is used for casting operations similar to those described above.

Next, FIG. 3, which shows the plasma melting apparatus B in detail, will be explained. The melting chamber 20 has a hollow furnace wall 50 surrounding the space above the molten metal pool 37a in the crucible 37. The furnace wall is composed of a lower furnace wall 51 and an upper furnace wall 52. Both of these furnace walls 51 and 52 have a water-cooled structure as is well known. The upper part of the lower furnace wall 51 and the upper furnace wall 52
A connecting member 53 is provided at the connecting portion with the lower part of the furnace, and the upper furnace wall 52 is rotatable with respect to the lower furnace wall 51. However, those lower furnace walls 51
Separation means is provided between the upper furnace wall 52 and the inside of the furnace wall 50 and the outside,
No gas flow occurs between the inside and outside of the furnace wall 50. Next, the airtight enclosure 22 includes a cylindrical portion 54 and a plate 55 closing the upper end of the cylindrical portion 54. An inspection port 56 and a raw material inlet 57 are provided in the side wall of the cylindrical portion 54 . The inlet 57 is provided with a pipe 57a communicating with the chute 17. Further, a connecting portion between the lower part of the cylindrical part 54 and the upper part of the upper furnace wall 52 is constructed using a connecting member 58, so that the upper furnace wall 52 is rotatable with respect to the cylindrical part 54. It is also provided with separation means similar to those described above. Next, the guide tube 23 is also called a raw material storage tank, and consists of a right cylindrical upper guide tube 59 and a tapered lower guide tube 60 connected to the lower end thereof. The inner surface of the lower guide tube 60 is provided with a lining 61 made of titanium. The airtight enclosure 22 and the guide cylinder 23 are integrally formed as described above, and have a water-cooled structure as is well known. Next, a guide tube 67 fixed to the plate 55 is provided in a hanging shape at the axial center position of the tube portion 54 and the upper guide tube 59. This guide tube 67 is lined with titanium. Therefore, there is a possibility that the titanium raw material sent from the feed port 57 collides with this guide cylinder 67, and a part of the guide cylinder 67 is scraped off, which enters the crucible 37 together with the raw material and is melted. However, the purity of the ingot formed as described above does not decrease. The lower part of the guide tube 67 is provided with a limiter 68 made of titanium and formed into a cylindrical shape. This limiter 68 is provided within the guide tube 67 so as to be able to move up and down, and is attached to the lower end of the elevating tube 69. An inner cylinder 70 is inserted into the limiter 68 and the elevating cylinder 69, and they have a double pipe structure. Further, the upper part of the elevating tube 69 is provided with a water supply port 71 and a drain port 72. Cooling water sent from the water supply port 71 flows into the inner cylinder 70 and the restriction body 68,
After flowing through the elevator cylinder 69 as shown by the arrow and cooling them, they are discharged from the drain port 72. A support frame 73 is attached to the plate 55, and an elevating cylinder 74 is attached to the upper part of the support frame 73. A piston rod 75 of the cylinder 74 is connected to the elevating cylinder 69 via a coupling 76, so that the restriction body 68 can be moved up and down by the operation of the cylinder 74. In this specification, the cylinder 74, the elevating tube 69, etc. are also referred to as elevating means for the restricting body 68.

Next, the plasma torch 24 is electrically insulated and mounted on the upper furnace wall 52 using a well-known torch mount 62. On the other hand, in the lower part of the melting chamber 20, the arcing piece 26 is attached to the support rod 25 using a bracket 63, and this combination is also referred to herein as an ignition rod. Further, this arcing piece 26 is stored in a storage chamber 64 formed in a part of the lower furnace wall 51 by moving the support rod 25 to the right in the figure. On the other hand, a magnetic field generating coil 78 for deflecting the plasma arc emitted from the plasma torch 24 is provided around the crucible 37 as is well known.

Next, the configuration of the connecting portion between the lower furnace wall 51 and the upper furnace wall 52 will be explained based on FIGS. 4, 5, 7, and 8. In the connecting portion, the connecting member 53 has a flange 81 fixed to the lower furnace wall 51 and a flange 82 fixed to the upper furnace wall 52. A retainer 9 formed in an annular shape is attached to the flange 81.
A base 98 of 7 is fixed using a bolt 96. The holding body 97 has a cylindrical holding wall 99, and two grooves formed on the outer circumferential side of the holding wall 99 each have an O.
Rings 100, 100 are held. Further, a grease supply groove 101 is provided between the O-rings 100, 100 over the entire circumference of the retaining wall 99. A grease supply hole 102 communicating with the grease supply groove 101 is formed inside the holding body 97 . As is well known, the supply hole 102 is connected to a greasing port and a greasing port, and is always connected to the supply groove 101.
It is now possible to supply grease to the Holder 9
A large number of supports 83 for supporting the weight of the upper furnace wall 52 are attached to the upper surface of the base 98 at 7, as shown in FIG. This support body 83 consists of a bearing 103 attached to the upper surface of the base 98 and a support roller 104 rotatably attached to the bearing 103. On the other hand, the flange 82 has a seal body 1 formed in an annular shape.
A base 107 of 06 is attached using bolts 105. The seal body 106 has a cylindrical seal wall 108
The inner surface of the wall 108 is in contact with the O-ring 100. Former sealing wall 10
8 and the O-ring 100 prevent the atmosphere inside the melting chamber from leaking to the outside and prevent outside air from flowing into the inside of the melting chamber. This structure is also referred to as separation means in this specification.
The separating means may be of any other known configuration. Grease is supplied to the contact portion between the seal wall 108 and the O-ring 100 through the grease supply groove 101, so that the life of the O-ring 100 is extended. An annular backing plate 109 is attached to the lower surface of the base 107 of the seal body 106, and the backing plate 109 is attached to the support roller 10.
It's on top of 4. Next, on the inner peripheral side of the retaining wall 99, there is a heat shielding wall 110 made up of a part of the upper furnace wall 52, and the retaining wall 99 is heated by the radiant heat of the plasma arc in the melting chamber. This is designed to prevent the O-ring 100 from becoming damaged due to high temperatures. Base 9 in holding body 97
A vibration stopper 84 is provided on the upper surface of the furnace wall 8 to prevent the upper furnace wall 52 from wobbling. This steady rest 84 includes a support block 114 and a steady rest roller 115.
A support block 114 is provided on the upper surface of the base 98 so as to be movable in the left-right direction (radial direction of the furnace wall 50) in FIG.
A steady roller 115 is rotatably attached to the holder. A set screw 117 is screwed onto the upright portion 116 integrally formed on the outer peripheral side of the base 98, and by rotating the set screw 117, the support block 114 is moved in the above direction. The roller 115 can be brought into pressure contact with the outer peripheral surface of the seal wall 108 without any gaps. Incidentally, unnecessary rotation of the set screw 117 is prevented by a lock nut 118. In this way, the upper furnace wall 52 is supported by the supporter 83 against the lower furnace wall 51, and the steadying device 8
4, the upper furnace wall 52 can be smoothly rotated with a light force with respect to the lower furnace wall 51. Support 8
3 is provided with a cylindrical dustproof cover 111 attached to the flange 81, and the flange portion at the upper end of the dustproof cover 111 is inserted into the inside of the groove 112, and the above-mentioned separate Dust is prevented from entering the means, the support 83 and the steady rest 84. As a result, the upper furnace wall 52 can always rotate smoothly with respect to the lower furnace wall 51.

Next, the configuration of the connecting portion between the upper furnace wall 52 and the surrounding portion 22 will be explained based on FIGS. 9 and 10. The connecting member 58 has a flange 121 fixed to the upper furnace wall 52 and a flange 122 fixed to the airtight enclosure 22. Both flanges 121,1 mentioned above
Separation means and a plurality of supporting devices are provided between 22. In addition, those separate means,
As for the supporting device and the steadying device, since they have the same structure as the above-mentioned lower connecting portion, parts that are considered to be functionally equivalent will be given the same reference numerals with the letter e and redundant explanation will be omitted.

Next, FIG. 6 shows a rotating device 85 connected to the upper furnace wall 52. As shown in FIG. A gear 86 is attached to the outer peripheral surface of the upper furnace wall 52. On the other hand, a hydraulic cylinder 87 is attached to a frame (not shown), and a rack 89 is attached to its piston rod 88. Pinion 9 meshed with rack 89
0 is a drive shaft 9 supported by bearings 92, 92.
3 are connected via a linking mechanism 91. A drive gear 94 is attached to the drive shaft 93, and the gear 94 meshes with the gear 86. In the rotating device 85 having such a configuration, the hydraulic cylinder 8
7's piston rod 88 expands or contracts, the pinion 90 rotates in one direction or in the opposite direction. The movement is an interlocking mechanism 9
1. It is transmitted to the drive gear 94 via the drive shaft 93, and the drive gear 94 similarly rotates. the result,
The upper furnace wall 52 reciprocates in one direction or the opposite direction as shown by the arrow. The rotation angle is set, for example, in the range of 60° in one direction and 60° in the opposite direction based on the intermediate position of the reciprocating rotation. The speed is such that, for example, a movement of 120° is performed in 0.3 to 3 minutes.

Since the upper furnace wall 52 is configured to reciprocate as described above, the entire range of the molten metal pool 37a in the crucible 37 can be uniformly heated as shown in FIG. The raw materials to be charged can be completely and quickly dissolved without leaving anything behind.

That is, in Fig. 11, if the arc spot of the plasma arc emitted from one plasma torch is in the range indicated by _A1 , then the surrounding range indicated by _A2 is where the raw material is heated due to rapid heat transfer. Dissolves rapidly. As time passes further, the heat of the arc spot _A1 spreads further to the periphery, and another plasma torch located at a symmetrical position 120 degrees apart from the plasma torch forming the arc spot indicated by _A1 above. Similar heating by arc from two plasma torches melts the area designated A ₃ . The plasma arc forming the arc spot indicated by A ₁ above is deflected by the magnetic flux generated from the magnetic field generating coil 78 to form an arc spot indicated by A ₁ '. Therefore, the raw material is rapidly dissolved in the surrounding area A ₂ ', and the dissolution range further expands as time passes. If the direction of the magnetic flux is reversed, the arc will similarly be deflected to a symmetrical position with respect to A ₁ , forming an arc spot as shown by A ₁ ″.The deflection of the arc by the magnetic flux will simultaneously cause the other two It also occurs in plasma torches, and the melting range is similarly expanded.As a result, depending on the plasma arc emitted from the three plasma torches,
A range of raw materials as indicated by A ₃ ' are dissolved relatively quickly. Furthermore, since the plasma torch is equipped with three other plasma torches in addition to the three mentioned above, these plasma torches can melt the raw materials in the range indicated by A ₃ ″ relatively quickly. As mentioned above, since the upper furnace wall 52 reciprocates, the above-mentioned A ₃ ' or
_The range of A ₃ '' will reciprocate from side to side in FIG. All parts of the raw material inserted into the plasma torch are melted quickly and homogeneously.The range of reciprocating rotation of the plasma torch is as follows:
The area in the crucible that is irradiated with the arc from one plasma torch may be such that the area that is irradiated with the arc from the adjacent plasma torch partially overlaps.

Next, the advancing/retracting device 27 for the arcing piece 26 shown in FIG. 12 will be explained. Fixed frame 12
Bearings 129 and 130 are attached to 7 and 128, respectively, and a screw rod 131 is rotatably supported by these bearings. Nut 13 is attached to screw rod 131.
2 are screwed together, and the nut 132 is the connector 13.
3 to the support rod 25. Support rod 2
5 is a power supply terminal 2 that supplies power to the arcing piece 26;
5' is provided, connected to the positive electrode of the DC power source of each plasma torch, and connected to the same potential as the stub 40. A motor 134 with a speed reducer is attached to the frame 127, and a sprocket 135 attached to its output shaft is connected to a sprocket 136 attached to a threaded rod 131 through a chain 137.

In the case of such a configuration, the motor 134
When the sprocket 135 operates and the sprocket 135 rotates, the rotation is transmitted to the sprocket 13 through the chain 137.
6, and as a result, the screw rod 131 rotates. Rotation of the threaded rod 131 causes the nut 132 to move to the right or left in the figure, and this movement is transmitted to the support rod 25 via the connector 133. As a result, the arcing piece 26 is moved from the housing 64 to the position shown in FIG.
It is possible to advance to a position between the tip of the crucible and the stub 40 in the crucible 37, or conversely, to retreat into the storage part 64 from the position shown in the figure.

Next, FIGS. 13 to 17 show the arcing piece 26.
The shape of the plasma torch and the ignition situation of the plasma torch by the arcing piece 26 are shown. Arc landing piece 26
is made of graphite, and is sized so that it can be positioned between the tip of each plasma torch 24 and the space within the crucible 37 (where the stub 40 is present), as shown in the figure. There is. In addition, in the process of retreating from the exit position to the storage position in the storage chamber 64 as shown in FIG. It is formed.
Therefore, the lower surface, ie, the surface 2 facing the molten metal pool, of the arcing piece 26 is lower than the upper surface, ie, the torch facing surface 26'.
6″ is wider.

Next, the ignition operation of the plasma torch 24 will be explained. First, the advancing/retracting device 27 is operated to position the arching piece 26 at the position shown in FIGS. 12 and 13. In this case, the distance between each tip of the entire plasma torch 24 and the arcing piece 26 is as follows:
The pilot arc from the torch 24 is smaller than the distance between the torch and the stub.
The distance is set in advance so that it can reach the target, that is, the ignition starting distance (for example, about 40 mm). Also, by rotating the upper furnace wall 52, a plurality of plasma torches 24
are positioned symmetrically with respect to the direction in which the arching piece 26 moves forward and backward. Next, each plasma torch 2
4 and blows it out from the nozzle, and each plasma torch 2
A voltage for plasma arc formation is applied between the cathode No. 4, the material to be melted (stub) in the crucible 37, and the arc starting piece 26. In this state, a high frequency discharge is caused between the cathode and the nozzle of the plasma torch, as is well known, to form (ignite) a pilot arc. Then, as is well known, a main arc 140 is formed from the cathode of the torch to the arc starting piece 26. In this case, the main arc 140 is set to the minimum current value necessary to maintain the arc. Although the formation of the main arc from each plasma torch 24 toward the arc-starting piece 26 as described above is performed simultaneously for the six plasma torches 24, this may be performed individually. Next, once the main arc from the plasma torch to the arcing piece 26 is formed as described above, the advancing/retracting device 27 is operated to move the arcing piece 26 from between the torch 24 and the material to be melted 40 into the storage chamber 64. Evacuate towards. The speed is, for example, about 500 mm per minute. When retracting the arcing piece 26 in this way, when the arcing piece 26 is withdrawn from between each plasma torch 24 and the object to be melted (stub) 40, the main The arc is from the torch 24 to the material to be melted 40
I look forward to it. When a main arc 140 is formed from all the torches toward the object 40, the current value of the main arc is increased to start melting the object 40.

When the plasma torch 24 is ignited using the arc ignition piece 26 as described above, as shown in FIG. Arrow 1 due to the current flowing through the piece
As shown by 41, a force is applied in a direction escaping from the arcing piece 26. The arcs 140 emitted from each plasma torch 24 are also subject to mutually attractive forces, ie, forces as indicated by arrows 142 in FIG. 16. Therefore, when retracting the arcing piece 26 as described above, the arc from the plasma torch 24 on the opposite side (the left side in FIG. 16) of the direction in which the arcing piece 26 is retracted with respect to the central axis of the crucible 37 At 140, the above two forces cancel each other out. Moreover, Arc 140
Force 14 due to the current flowing from to the arcing piece
1, the arc is bent in the direction in which the length of the arc reaching the object 40 to be melted becomes shorter,
Since it is easy to secure a current path with the object 40 to be melted, the arc can be stably transferred from the arc starting piece 26 to the object 40 to be melted. On the other hand, the plasma arc 140 emitted from the torch 24 (the torch shown on the right side in FIG. 16) located on the retracting direction side of the arcing piece 26 with respect to the central axis of the crucible is caused by the escape force 141 and the arc. Mutual attraction force 1
42 are in the same direction, and furthermore, the direction in which the arc 140 is bent is the direction in which the length of the arc reaching the object to be melted 40 becomes longer, making it difficult to secure a current path with the object to be melted 40. When the plasma arc 140 attempts to move from the arcing piece to the object to be melted 40, the arc 140 is sprung up at the rear end of the arcing piece 26, does not reach the object to be melted 40, loses the current path, and is extinguished. However, since the rear end portion of the arcing piece 26 when it retreats is formed on the slope 26a as described above, the plasma arc 140 from the plasma torch 24 to the arcing piece 26 is prevented by the arcing piece 26 retracting. Even when moving away from the arc, contact between the arc 140 and the arcing piece 26 can be maintained up to the lower part of the arcing piece 26, that is, the portion close to the object 40 to be melted. Moreover, the plasma gas, which is the medium of the arc 140 ejected from the plasma torch toward the object 40, can be smoothly directed toward the object 40 even when the arc starting piece 40 leaves the arc, thereby preventing arc disturbances. Don't let it happen. As a result, the plasma gas quickly reaches the object 40 to be melted, and at the same time, a part of the arc 140 easily reaches the object 40 to secure a current path, thereby reducing the current borne by the arc piece. Since the force 141 is weakened, the arc is always maintained stably and a smooth transition can be performed.

Note that the rear end surface of the arched piece when retreating is the 17th
If the arcing piece is vertically formed as shown in the figure, when the arcing piece retreats from between the torch and the object to be melted, the force acting on the plasma arc 140 as described above will be 1.
41,142 makes it difficult for the arc 140 to move toward the object to be melted, causing a large disturbance in the electromagnetic field. As a result, not only the plasma arc 140 emitted from that torch but also the arcs already emitted from other torches toward the object to be melted are affected by the disturbance of the electromagnetic field and extinguished. However, as described above, in this apparatus, since the rear end surface 26a of the arcing piece 26 is formed as described above, the transition of the plasma arc from the arcing piece to the object to be melted is stabilized as described above. It is done.

Next, FIG. 18 shows an example in which the shape of the rear end of the arching piece when retracted is different. The rear end of the arching piece may not be formed into a straight slope as described above, but may be formed into a convex slope as shown in FIG. 18.

It should be noted that parts that are functionally the same or equivalent to those in the previous figure are given the same reference numerals as in the previous figure with an alphanumeric letter "f", and redundant explanations are omitted.
(Also, the same concept is used in the figures in Figs. 19 to 21, and the redundant explanation is omitted by adding the letter g in the alphabet.) Next, in Figs. 19 to 21, the shapes of the arcing pieces are different. An example is shown. In the arcing piece 26g shown in these figures, the piece 26g
A narrow groove 145 as shown in the figure is formed at the rear end portion when the is retracted. The width of this groove 145 is determined by the width of the plasma torch 24 as shown in FIG.
The center part of the plasma arc irradiated from g to the arcing piece 26g passes through the groove 145 and reaches the material to be melted in the crucible (for example, about 10 mm). Further, as shown in FIG. 21, the groove bottom 145a of the groove 145 is formed as a slope in the same manner as in the above case. (The bottom of this groove is code 145.
It may also be placed on a vertical plane as shown by a′. ) When igniting a plasma torch using the arc ignition piece 26g having such a configuration, the upper furnace wall is rotated so that the irradiation area of the arc from each plasma torch on the arc ignition piece 26g is aligned. 14
Make sure that it is in the position shown in 6. In this state, ignition is performed as described above. The subsequent arcing piece 26g is retracted in the direction indicated by reference numeral 144. When the arcing piece 26g is retracted in this way, the piece 26g moves as shown by the imaginary line, and a groove is formed in the part indicated by the reference numeral 146'.
45, as shown in FIGS. 20 and 21, the center of the arc 140g irradiated toward the groove 145 heads into the crucible through the groove 145 as described above. Therefore, further piece 26
As g recedes, the arc also stably moves from the arc starting piece toward the material to be melted in the crucible. In this case, both edges 145b, 14 of the groove 145
5b, the cross-sectional shape of the edge on the side that becomes the retreating end when the arcing piece retreats is made into an upwardly inclined cross-sectional shape so that the surface facing the molten metal pool is larger than the surface facing the plasma torch. It is possible to obtain an effect equivalent to that of the above, and the above-mentioned arc transition can be performed stably.

Next, FIGS. 22 and 23 show a situation in which raw materials are charged into the melting chamber 20 and melted by an arc from a plasma torch. The operation in that case will be explained below. First, normally, the limiter 68 is moved by the lifting cylinder 74.
is lowered so that its lower end faces the lower opening 60a of the lower guide cylinder 60. In this case, a gap 149 is provided between the inner surface of the opening 60a and the outer surface of the restricting body 68 through which a fine grained or spongy titanium raw material (the size of which is, for example, about 3 mm to 20 mm) can pass. In this state, small titanium raw materials 1 such as spongy or fine granular raw materials are fed from the drum feeder to the charging section 21 through the chute 17 and the feed port 57.
50 is guided toward the center of the melting chamber (the center of the crucible) by an upper guide tube 59 and a lower guide tube 60, and further passes through the gap 149 toward the center of the molten metal pool 37a in the crucible 37. charged. On the other hand, a large titanium raw material 1 such as internal scrap of the raw material fed into the charging section 21
51 cannot pass through the above-mentioned gap 149, and as shown in FIG. 22, it is caught between the lower guide tube 60 and the restrictor 68 and stops there. Once the large raw material 151 has stopped at the above location, the small titanium raw material 150 continues to fall toward the molten metal pool 37a for a while, and then the restriction body 151 is stopped as shown in FIG. 6
8 is raised and the large raw material 151 is dropped toward the molten metal pool in the crucible. In this case, as described above, the small raw materials 150 are first dropped toward the center of the molten metal pool 37a in the crucible 37, and the small raw materials are accumulated there. A large raw material 151 is dropped. Therefore, the small-sized raw materials that have been dropped first and are piled up in the center of the molten metal pool act as a cushioning material, which cushions the impact of the large-sized raw material 151 falling. Even when such a large raw material is charged, scattering of the molten metal is prevented by suppressing the falling speed by the action of the restrictor 68 and by the buffering effect of the small raw material.

The size of the gap 149 can be set variously by appropriately selecting the height at which the limiter 68 is positioned. Thereby, as described above, the size of the raw material to be temporarily stopped within the guide cylinder 60 can be selected from various sizes. Also, as mentioned above, the limiter 68
is located in the melting chamber 20, and the large raw material can be stopped at a position relatively close to the crucible and then dropped into the crucible, which prevents it from falling outside the crucible and damaging the crucible. When a small raw material 150 is charged in advance and a large raw material 151 is charged on top of it, the large raw material 151 is prevented from falling directly into the molten metal in the crucible, so that the molten metal does not overflow onto the crucible. This prevents flying particles from adhering to the torch 24 and damaging it.

Next, FIGS. 24 to 28 show different examples of guide tubes. The guide cylinder shown in these figures is equipped with a buffer means for slowing down the falling speed of the raw material. In the figure, the airtight enclosure 22h
A cylinder body 152 is provided at the axial center position of the cylinder portion 54h and the upper guide cylinder 59h of the guide cylinder 23h. The outer peripheral surface of this cylindrical body 152, except for its upper part, is covered with a protection pipe 153 made of titanium. As a result, even if the raw material fed from the raw material inlet 57h hits the protection pipe 153 and is partially scraped off, and the scraped material falls together with the raw material toward the crucible, It is designed so as not to reduce the purity of the raw materials inside the crucible. A retaining ring 154 is fixed to the lower end of the cylindrical body 152 using a fastener 155.
The ring 154 is connected to the upper end of a cap-shaped substrate 156 . The substrate 156 is made of stainless steel, and its upper surface is covered with a liner 157 made of titanium. This liner 157 is provided for the same purpose as the protection pipe 153. A plurality of support pieces 158 are attached to the lower surface of the substrate 156. A shaft body 159 is supported by these support pieces 158. The shaft body 159 is formed into a ring shape centered on the axis of the cylinder body 152. A connecting piece 160 is swingably suspended from the shaft 159. The upper end portion of a buffer piece 161 made of titanium is fixed to the connecting piece 160 using a plurality of fasteners 162. As a result, the buffer piece 161 can swing like a pendulum in the radial direction of the guide tube 23h about the shaft 159. The connecting piece 160 has a weight 16 integrally formed therewith.
3 is installed. Due to the presence of this weight 163, the buffer piece 161 receives a biasing force that causes its lower end to open outward. Therefore, in the state shown in FIG. 24, the lower end of the buffer piece 161 is connected to the lower guide tube 60.
It is in a state of being in contact with a lining 61h provided on the inner surface of h. In addition, the above protection pipe 153
One end of a plurality of support pieces 164 is attached to the lower end of the support piece 164 . The other end of the support piece 164 is in contact with the inner surface of the upper guide cylinder 59h. As a result, the cylinder 152 is fixedly located at the axial center position of the guide cylinder 59h.

In the case of the above configuration, the inlet 57
The small raw material fed into h is guided by the upper guide cylinder 59h and falls downward. Further, the raw material is guided by the lower guide tube 60h, moves toward the center, and hits the buffer piece 161. Then, the raw material tilts the buffer piece 161 inward, passes through the gap created between the buffer piece 161 and the lining 61h, and heads toward the lower opening 60ah of the guide tube 60h, and from there, the same process as in the previous case is carried out. It falls into the molten pool inside the crucible. Therefore, in the above case, even if a small raw material enters the guide tube 23h from the inlet 57h with force, the force is removed by the buffer piece 161, and the raw material gently flows into the molten metal pool in the crucible. will be put into the Therefore, the raw material is ensured to fall in the center of the crucible without falling to the edges of the crucible or outside the crucible. Incidentally, the above-mentioned buffering effect is not limited to small-sized raw materials, but is similarly performed on large-sized raw materials. Furthermore, if a raw material that is too light to tilt the buffer piece 161 falls outside the buffer piece 161,
The raw materials are stored there. When the weight of the accumulated material reaches a value sufficient to tilt the buffer piece 161, the accumulated raw materials are removed from the buffer piece 16.
1 is tilted and falls into the crucible.

Next, the guide tube 23h may be provided with a restriction body 68h similar to that described above, as shown in imaginary lines in FIG. Such a restriction body 6
In the case of a structure equipped with 8h, the following functions can be obtained. That is, in the case of a small-sized raw material, it is possible to direct the raw material into the crucible while the falling force of the raw material is removed by the buffer piece 161, as in the case described above. Regarding large raw materials, the buffer piece 161 comes into contact with the limiter 68h as shown by the imaginary line in FIG. 24, so the large raw material 151h stops between the buffer piece 161 and the inner surface of the lower guide cylinder 60h. . and limit body 6
By raising 8h, the raw material 151h can further tilt the buffer piece 161, pass under it, and fall into the crucible from the lower opening 60ah. In this example as well, by selecting various heights at which the limiter 68h is positioned in advance, raw materials larger than a desired size can be temporarily stopped as described above.

In addition, in the description of the items shown in FIGS. 24 to 28, parts that are functionally the same or equivalent to those in the previous drawings will be designated with the same reference numerals as those in the previous drawings with the letter "h" added. Explanation omitted.

As described above, in the present invention, the molten metal pool 3
7a is surrounded by the furnace wall 50, and the upper part of the raw material charging part 21 provided above the furnace wall 50 is also surrounded by the surrounding part 22, so that the above-mentioned molten metal pool 37a
A plurality of plasma torches 24, 24, .
This has the effect of converting the raw material on the molten metal pool 37a into molten metal.

Moreover, not only are the plasma torches 24, 24 provided with a plurality of them, but they are also connected to the molten metal pool 37.
Since it rotates around point a, the raw material on the molten metal pool 37a receives heat extremely evenly,
It also has the excellent effect of quickly changing into a homogeneous molten metal and efficiently obtaining a high-quality molten metal.

Moreover, the plasma torches 24, 24 can be rotated by fixing the lower furnace wall 51 and the surrounding part 22, rotating only the upper furnace wall 52 located in the middle, and attaching them thereto. Since the plasma torch 24 is rotated by the rotation of the plasma torch 24, the plasma torches 24, 24 can be operated relatively easily, and there is also a rational effect that the plasma torches 24 can be operated without requiring much operating energy.

[Brief explanation of drawings]

The drawings show an embodiment of the present application, and FIG. 1 is a schematic vertical cross-sectional view of a melting and casting apparatus, FIG. 2 is a diagram for explaining the operation of the apparatus shown in FIG. 1, and FIG. is a longitudinal cross-sectional view of the melting device, FIG. 4 is a plan view showing the connection between the lower furnace wall and the upper furnace wall, and FIG. 5 is a front view of the same.
Figure 6 is a diagram showing the mechanism of the rotating device for the upper furnace wall, Figure 7 is a cross-sectional view taken along the - line, Figure 8 is a cross-sectional view taken along the - line, and Figures 9 and 10 are the upper furnace wall and the airtight enclosure. Fig. 11 is a plan view for explaining the melting range in the crucible, and Fig. 12 shows the arcing piece in the melting device and its structure. Fig. 13 is a plan view showing the relationship between the plasma torch and the arcing piece, Fig. 14 is a plan view of the arcing piece, Fig. 15 is a - line sectional view, Figures 16 and 17 are diagrams for explaining the transition of the plasma arc from the arc starting piece to the object to be melted.
Fig. 8 is a diagram showing different examples of cross-sectional shapes of the rear end of the arcing piece, Fig. 19 is a plan view showing different examples of the arcing piece, and Fig. 20 is a sectional view showing the relationship between the groove and the plasma arc. , Figure 21 is the same as in Figure 20.
A sectional view taken along the line XI-XI, Fig. 22 is a longitudinal sectional view to explain the movement of the raw material within the guide cylinder, and Fig. 23 shows the relationship between the guide cylinder and the raw material introduced therein, the crucible, and the plasma torch. Longitudinal sectional view shown, No. 24
The figure is a longitudinal sectional view showing different examples of the guide tube, No. 25.
The figure is a longitudinal sectional view showing the relationship between the buffer piece and the member that supports it, Figure 26 is a plan view (partially cut away) of the member shown in Figure 25, and Figure 27 is a diagram showing the relationship between the board and the buffer piece. Figure 28, a diagram showing the relationship in detail, is -
Line sectional view. B... Plasma melting device, 37a... Molten metal pool, 50... Furnace wall, 24... Plasma torch, 2
1... Raw material charging section.

Claims (1)

[Claims] 1. A molten metal pool that receives charged raw materials and melts them there, and a space above the molten metal pool that surrounds the periphery, and a raw material charging section is provided in the center above the molten metal pool. A surrounding part is provided around the furnace wall to surround the upper part of the raw material charging part and includes a raw material inlet, and a surrounding part is installed around the furnace wall to direct plasma toward the molten metal pool. It consists of a plurality of plasma torches designed to emit an arc, and the raw material introduced from the raw material inlet provided in the surrounding part is brought into the molten metal pool, and the raw material is turned into molten metal by the plasma arc. In the plasma melting apparatus, the furnace wall is separated into upper and lower parts at an intermediate position between the molten metal pool position and the plasma torch mounting position, and the lower part of the upper furnace wall is rotated relative to the upper part of the lower furnace wall. They are movably connected, and are equipped with a separating means to separate the inside and outside air in a rotating state.Furthermore, the upper part of the upper furnace wall and the surrounding part are constructed separately, and the surrounding part is separated from the surrounding part. The upper part of the upper furnace wall is rotatably connected to the lower part, and a separation means is provided to separate the inside and outside air in the rotating state, leaving the lower furnace wall and the surrounding part stationary. A plasma melting apparatus characterized in that the plurality of plasma torches can be rotated around the molten metal pool even in a state where the plasma melting apparatus is in a state where the plasma melting apparatus is