CN116147340A

CN116147340A - Metal or graphite crucible, preparation method thereof and smelting method using same

Info

Publication number: CN116147340A
Application number: CN202210810821.6A
Authority: CN
Inventors: 李碚
Original assignee: Zhengzhou Lide New Material Technology Co ltd
Current assignee: Zhengzhou Lide New Material Technology Co ltd
Priority date: 2022-07-11
Filing date: 2022-07-11
Publication date: 2023-05-23

Abstract

The invention discloses a crucible, which comprises a crucible wall and a crucible bottom, wherein an induction coil surrounds the outer side of the crucible wall; the crucible is made of metal or graphite; the crucible is provided with slits along the height direction of the crucible, so that the crucible is formed into a structure formed by combining a plurality of flaps, and slits between adjacent flaps form gaps. According to the crucible, the electromagnetic field can penetrate through the wall of the crucible to directly heat materials, so that the smelting temperature can be increased, the smelting time can be shortened, and the energy consumption can be reduced; because the electromagnetic field directly heats the materials, the crucible is not required to be heated to a great degree of superheat, so that the loss of the crucible can be reduced, and the service life of the crucible can be prolonged; the superheat degree of the crucible is reduced, and the contact between the molten pool and the crucible wall is weakened due to the magnetic suspension force, so that the pollution of crucible materials to materials is reduced; such a crucible can be used in both pull down ingot technology and directional solidification technology for preparing high-end materials.

Description

Metal or graphite crucible, preparation method thereof and smelting method using same

Technical Field

The invention relates to the technical field of metal and alloy smelting, in particular to a metal or graphite crucible, a preparation method thereof and a smelting method using the same.

Background

Electromagnetic induction smelting techniques include high frequency induction smelting, medium frequency induction smelting, power frequency induction smelting and superaudio induction smelting techniques, which are mainly used for materials with higher requirements on product quality. Under the condition of higher requirements on the product quality, electromagnetic induction smelting (induction smelting for short) needs to be completed under the protection of vacuum or inert gas.

Most of the crucibles used for induction melting are heat resistant ceramic crucibles, such as corundum crucible, magnesia crucible, zirconia crucible, etc., but such crucibles cannot be used in melting some high-end materials because they cause pollution to the materials being melted or because they cannot withstand too high a melting temperature. Therefore, a metal crucible or a graphite crucible is required to be used in some cases. For example, tungsten crucibles for smelting rare earth metals, rare earth alloys and high melting point compounds, molybdenum crucibles, tantalum crucibles, graphite crucibles for smelting refractory metals, copper, aluminum, iridium crucibles for smelting noble metals, semiconductors and preparing single crystals, platinum crucibles, etc. When a metal crucible or a graphite crucible is used, in view of the requirements of crucible materials and the requirements of materials to be melted, it is necessary to perform the melting under a vacuum or inert gas-protected environment, that is, it is necessary to employ a vacuum electromagnetic induction melting technique (vacuum induction melting for short).

In the process of carrying out induction smelting on materials by utilizing a metal crucible or a graphite crucible, because the crucible wall has conductivity, eddy currents induced by an electromagnetic field in the crucible are concentrated and distributed along the outer surface of the crucible wall, and the eddy currents have a shielding effect on the electromagnetic field, so that the electromagnetic field cannot enter the crucible to directly heat the materials in the crucible. The melting process can only rely on an electromagnetic field to heat the crucible to a high temperature, then the high-temperature crucible transfers heat to materials in the crucible through heat conduction, so that the materials are gradually heated, and then melting or reaction of the materials can be realized. Therefore, the technology of adopting a metal crucible or a graphite crucible to perform induction smelting on materials requires that the crucible has great superheat degree and long heat conduction time, thereby limiting smelting temperature, shortening the service life of the crucible, reducing production efficiency, and the crucible wall with high temperature has great pollution to a molten pool caused by the melting effect and chemical reaction of the molten pool.

Disclosure of Invention

The invention designs a metal crucible or a graphite crucible with electromagnetic penetration capability and magnetic suspension effect in order to overcome the problems, and aims to replace the traditional metal crucible or graphite crucible with traditional structure in induction smelting operation, so as to improve smelting temperature, accelerate smelting process, reduce energy consumption, improve production efficiency, reduce crucible loss and lighten pollution of crucible materials to materials. .

The invention adopts the following technical scheme:

in one aspect, the invention adopts a crucible, which comprises a crucible wall and a crucible bottom, wherein the outer side of the crucible wall surrounds an induction coil;

the crucible is made of metal or graphite;

the crucible is provided with slits along the height direction of the crucible, so that the crucible is formed into a structure formed by combining a plurality of flaps, and slits between adjacent flaps form gaps.

In another aspect, the present invention provides a method for preparing the above crucible, comprising:

step 1, inputting a 3D design drawing of a crucible structure into a control system of a printer, and loading metal powder or graphite powder for manufacturing the crucible into a powder supply system of the printer;

step 2, lifting a workbench in a forming system onto a working surface, and conveying powder to the surface of the workbench by utilizing a powder conveying mechanism in a powder supply system to form a powder layer with uniform thickness;

step 3, starting an energy beam generator to enable an energy beam to be emitted onto a powder layer on the surface of the workbench through an energy beam scanning system, and controlling the energy beam scanning system to enable the energy beam to scan according to the structure of the bottom layer section of the crucible by the control system according to the crucible design drawing, so that powder at a scanning position is burned and fused to form a first layer structure of the crucible;

step 4, reducing the height of the workbench equal to the thickness of one layer of raw material powder by using a forming piston, paving a second layer of powder on the surface of the workbench by using a powder feeding mechanism in a powder supply system, and controlling an energy beam to scan on a new powder layer to form a second layer structure of the crucible;

step 5, repeating the step 4 to finish the preparation of the whole structure of the crucible layer by layer from the bottom layer to the top layer;

and 6, purging the excessive powder which exists in the position where the energy beam is not scanned into a recovery box.

In yet another aspect, the invention employs a smelting process using the above crucible.

In a first aspect, a smelting process includes:

s1, after a material is filled into a crucible, vacuumizing a smelting chamber, or filling argon after vacuumizing, and then starting an induction power supply to heat the material;

s2, increasing power after the materials begin to melt and form a molten pool, so that the molten pool is in a suspension state;

s3, carrying out casting work after preserving heat for a period of time in a suspension state.

In a second aspect, a smelting process includes:

s3, receiving metal vapor generated by a molten pool through a metal vapor receiver arranged above the crucible, and condensing and crystallizing gaseous metal atoms on the metal vapor to form metal crystals.

In a third aspect, a smelting process includes:

s1, a separating structure is arranged between a crucible bottom and a crucible wall, a pull rod extending downwards is arranged on the lower end face of the crucible bottom, and the pull rod extends to the lower side of a smelting chamber through vacuum sealing and is combined with a pull ingot driver;

s2, after the materials are filled into the crucible, vacuumizing a smelting chamber, or filling argon after vacuumizing, and then starting an induction power supply to heat the materials;

s3, increasing power after the materials begin to melt and form a molten pool, so that the molten pool is in a suspension state;

s4, starting a pull ingot driver after the materials are melted, and pulling down a pull rod to enable a molten pool on the bottom of the crucible to move out of the crucible downwards along with the pull rod to be cooled and solidified to form an ingot blank.

In a fourth aspect, a smelting process includes:

s1, a separating structure is arranged between a crucible bottom and a crucible wall, a pull rod extending downwards is arranged on the lower end face of the crucible bottom, the pull rod extends to the lower side of a smelting chamber through vacuum sealing and is combined with an ingot pulling driver, and a temperature field device is arranged below the crucible;

s4, starting a pull ingot driver after the materials are melted, and pulling down the pull rod to enable a molten pool on the bottom of the crucible to solidify under the condition of axial temperature gradient when the molten pool moves out of the lower opening of the crucible downwards along with the pull rod, so as to form an ingot blank of directional crystallization.

In a fifth aspect, a smelting process includes:

s1, after a non-conductive compound or semiconductor material is filled into a crucible, a conductive ignition material is buried into the non-conductive compound or semiconductor material;

s2, vacuumizing a smelting chamber, or filling argon after vacuumizing, starting an induction power supply to preheat the material to a conductive temperature, enabling the high-temperature material to form induction current under the action of an electromagnetic field, heating and melting from the inside, and expanding a melting range to the periphery until the material is completely melted;

s4, carrying out casting work after preserving heat for a period of time in a suspension state.

Compared with the metal or graphite crucible in the prior art, the invention has the following advantages:

the electromagnetic field can penetrate through the wall of the crucible to directly heat the materials, so that the smelting temperature can be increased, the smelting time can be shortened, and the energy consumption can be reduced;

because the electromagnetic field directly heats the materials, the crucible is not required to be heated to a great degree of superheat, so that the loss of the crucible can be reduced, and the service life of the crucible can be prolonged;

the crucible superheat degree is reduced, and the contact between the molten pool and the crucible wall is weakened due to the magnetic suspension force, so that the pollution of crucible materials to materials is reduced, and the effect has a special significance for the production process with high heating temperature, long smelting time and strict product requirements;

such crucibles can be used in both pull down and directional solidification techniques for preparing high end materials, and non-split metal and graphite crucibles cannot be used in these techniques;

the crucible of the present invention can be used to melt a compound or semiconductor that is not conductive at room temperature using an inductive power supply.

Drawings

FIG. 1 is a view of a metal crucible or graphite crucible of the present invention having a split structure;

FIG. 2 is a schematic illustration of the formation of eddy currents and magnetic levitation forces in a crucible of the present invention;

FIG. 3 is a cross-sectional view of a crucible with a groove machined at the slit of the crucible flap;

FIG. 4 is a schematic view showing the magnetic levitation effect of the bottom surface of the molten pool by changing the shape of the inner surface of the bottom of the crucible;

FIG. 5 is a diagram of a crucible and an induction coil arrangement for obtaining a magnetic levitation force in an upward direction and a magnetic levitation force having an upward component force;

FIG. 6 is a diagram showing a configuration of a crucible having a cylindrical crucible wall and a conical crucible bottom and an induction coil;

FIG. 7 is a diagram of a crucible with a crucible cover, a crucible plug, and a crucible holder in a smelting furnace;

FIG. 8 is a 3D printed drawing of a crucible of the present invention;

FIG. 9 is a crucible with a tilt casting function in a melting furnace;

FIG. 10 is an apparatus for distilling metal using the crucible of the present invention;

FIG. 11 is an apparatus for pulling down a dummy ingot using a crucible of the present invention;

FIG. 12 is an apparatus for melting a compound using a crucible of the present invention.

The device comprises a 1-crucible, a 2-crucible wall, a 3-crucible bottom, a 4-induction coil, a 5-flap, a 6-gap, a 7-molten pool, an 8-groove, a 9-molten pool bottom, a 10-crucible bottom induction coil, an 11-crucible cover, a 12-crucible frame, a 13-insulating and heat-insulating material, a 14-smelting chamber, a 15-crucible plug, a 16-mold, a 17-energy beam generator, an 18-energy beam scanning system, a 19-molding system, a 20-powder supply system, a 21-control system, 22-metal powder or graphite powder, a 23-molding piston, a 24-workbench, a 25-powder supply roller, a 26-energy beam, a 27-crucible layer structure, a 28-injection ring, a 29-gas nozzle, a 30-metal vapor receiver, 31-metal vapor, 32-metal crystals, 33-pull rods, 34-ingots, a 35-temperature field device, 36-ignition material, 37-compound or semiconductor material.

Detailed Description

The following detailed description of embodiments of the invention, provided in the accompanying drawings, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, based on the embodiments of the invention, which are apparent to those of ordinary skill in the art without inventive faculty, are intended to be within the scope of the invention.

As shown in fig. 1, the present embodiment provides a metal crucible/graphite crucible 1 including a crucible wall 2 and a crucible bottom 3. As the present embodiment, the crucible wall 2 and the crucible bottom 3 may have a unitary structure or may have a split structure. The current output by the induction power supply generates an electromagnetic field through the induction coil 4 surrounding the crucible 1, and in order to improve the action efficiency of the electromagnetic field, a small gap should be kept between the induction coil 4 and the outer wall of the crucible. The shape of the cross section (referring to the cross section parallel to the axial direction of the crucible, see also the section A-A in fig. 1) of such a metal crucible or graphite crucible may be circular, rectangular, square, or other shape, or may be a combination of cross sections of different shapes in the height direction. The crucible bottom 3 can be a plane, a conical surface, a hemispherical surface, a spherical table surface, a paraboloid and other curved surfaces, and can also adopt a combination of bottom surfaces with different shapes.

In the present embodiment, the crucible 1 has slits along the height direction of the crucible, and the crucible 1 is constituted by combining a plurality of flaps 5, and gaps 6 are provided between adjacent flaps 5. Due to the existence of the gap 6, the electromagnetic field can penetrate through the crucible 1 and enter the crucible, and the materials in the crucible are directly heated.

As shown in fig. 2, another function of the split structure of the crucible 1 is to generate electromagnetic levitation force on the material: the electromagnetic field B generated by the induction coil 4 forms an induced current I in each crucible flap 5, the eddy currents I in the flaps 5 are combined into an equivalent annular current I1 on the inner wall of the crucible, the electromagnetic field B entering the crucible 1 induces the material in the crucible to form eddy currents I2, and the heat generated by the eddy currents I2 causes the material to melt. After the material is melted, a molten pool 7 is formed, the vortex I2 is only distributed on the surface of the molten pool 7, and the direction of the vortex I2 is always opposite to the direction of the equivalent current I1 of the inner wall of the crucible, so that an ampere force F of electromagnetic action exists between the vortex I2 and the crucible, and the force F acts on the surface of the molten pool, and the direction of the force F is always perpendicular to the wall 2 of the crucible and points to the center of the crucible, namely the electromagnetic levitation force. The surface of the molten pool 7 is separated from the inner wall of the crucible 1 under the action of the repulsive force F, so that a suspension state is formed. Arrows and F represent repulsive forces generated between I1 and I2.

In the present embodiment, since the electromagnetic field is attenuated when passing through the slit 6 of the crucible flap 5, the wider the slit 6 is, the better the penetrating effect of the electromagnetic field is, but the too large the slit 6 causes leakage of the liquid metal. The width of the slit 6 may be selected in the range of 0.02mm to 20mm, and the optimal width of the slit 6 is 0.1mm to 5mm. Further, the width of the slit 6 may be varied in the height direction of the crucible 1, and a larger slit width may be selected at a position higher than the molten pool 7, so that the resistance of the slit to the electromagnetic field is reduced as much as possible.

In the present embodiment, since the types of the melting materials and the batch sizes of the crucible 1 are greatly different, the coverage of the size of the crucible 1 is large. The diameter or side length of the inner wall of the cross section of the crucible 1 may cover a range of 5mm to 500 mm; the height may be in the range 5mm to 2000 mm. Increasing the thickness of the crucible wall 2 increases the distance that the electromagnetic field experiences to penetrate the gap 6, so decreasing the wall thickness increases the penetration efficiency of the electromagnetic field. However, too small a wall thickness reduces the strength of the crucible 1 and shortens the life of the crucible. Further, the thickness of the crucible wall 2 of the present embodiment may be selected in the range of 0.1mm to 100 mm. The larger the size of the crucible 1, the greater the thickness of the crucible wall 2. The thickness of the crucible wall 2 is also related to the material of the crucible and the melting point of the material to be smelted, the thickness of the noble metal crucible is smaller, and the thickness of the crucible used for smelting the low-melting-point material is also smaller. The dimensions and thickness of the cross section of the crucible can vary in the height direction of the crucible 1. In order to increase the penetration effect of the electromagnetic field, it is also possible to machine a groove 8 in the outer wall of the crucible at the slit 6, which serves to reduce the actual wall thickness of the crucible at the slit 6, see fig. 3.

In the present embodiment, increasing the number of lobes of the crucible lobes 5 corresponds to increasing the total width of the gaps 6 between the crucible lobes, which is advantageous for increasing the efficiency of the electromagnetic field entering the crucible, but too many lobes reduce the strength of the crucible and increase the manufacturing cost. The number of the segments of the crucible segments 5 depends on the inner diameter of the crucible, and the number of the segments can be selected according to the inner diameter of the inner wall of the crucible on the cross section or the ratio P of the side length L of the crucible to the side length L of the segments, specifically, the range of the P value is 5:1 to 50:1, at 8: 1-20: 1, the number of corresponding petals is 4 to 100 petals, and 10 to 50 petals are the most preferable. As another embodiment, the number of petals 5 depends on the size of the crucible cross-section. Specifically, the crucible with the diameter smaller than 50mm can be designed according to 6-20 petals; the crucible with the diameter of more than 50mm and less than 300mm can be designed according to 12-50 petals; the crucible with the diameter larger than 300mm can be designed according to 30-100 petals.

In the present embodiment, the slit 6 of the crucible flap may be the lowest point of the crucible extending from the highest point of the crucible 1, or may be a distance from a certain height position without being slit, and a seamless ring may be left, so as to maintain the overall structure of the crucible 1. The location of the seamless ring may be at some position in the uppermost, lowermost, or middle of the crucible. The number of seamless rings may be 1, 2 or more. In some embodiments, the direction and shape of the slit 6 is a straight line parallel to the crucible axis. In other embodiments, the gap 6 may be a diagonal, curved or serpentine line extending from between the upper and lower ends of the crucible in order to increase the cumulative total length of the gap 6 and increase the path of the electromagnetic field through the crucible wall 2.

In the present embodiment, since a high electromagnetic field efficiency can be obtained only by keeping a small gap between the coil 4 and the outer wall of the crucible 1, the shape of the coil 4 generating the electromagnetic field matches the outer shape of the crucible 1. Since the crucible 1 has a generally columnar shape, the coil 4 has a generally columnar shape. Since the direction of the ampere force F generated by the electromagnetic field to the bath is perpendicular to the side wall of the coil 4, in this case the magnetic levitation force has no upward component, the surface of the bath 7 in the crucible forms a gap with the inner wall of the crucible under the action of the force F, but as the distance from the top of the bath 7 increases, the pressure that the gravity of the bath 7 forms on the surface thereof increases, so that the bath 7 will form a hump-like shape with a small upper diameter and a gradually increasing lower diameter. The magnetic suspension effect of the molten pool 7 is gradually weakened at the middle part and the lower part, and the magnetic suspension effect is hardly generated at the bottom of the molten pool 7. The inner wall of the crucible bottom 3 is designed to be a conical surface, a hemispherical surface, a spherical table surface, a paraboloid or other types of curved surfaces with inclination, and the bottom surface 9 of the molten pool can also be separated from the inner wall of the crucible under the action of F force in the direction perpendicular to the axis of the crucible, so that a certain magnetic suspension effect is obtained, and the magnetic suspension effect is shown in fig. 4.

In this embodiment, as shown in fig. 5, the effect of improving the melting effect is achieved by further obtaining a magnetic levitation force in an upward direction in the molten pool, particularly in the bottom of the molten pool. In addition to the induction coil 4 on the side of the crucible wall 2, the provision of a crucible bottom induction coil 10 below the crucible bottom 3 can generate an additional magnetic levitation force in upward direction on the bottom of the bath 7.

In the present embodiment, as shown in fig. 5, the magnetic levitation force F generated by the crucible wall 2 with the taper angle α and the induction coil 4 having a large upper end diameter and a small lower end diameter has not only the component force Fa in the inward direction but also the component force Fb in the upward direction. The larger the taper angle α, the larger the upward component force Fb. Therefore, in order to obtain a magnetic levitation force in the upward direction, or a magnetic levitation force with an upward component force, the shape of the crucible 1 and the configuration of the induction coil 4 may be configured in several forms:

the crucible 1 and the induction coil 4 are integrally configured in a tapered shape with a large upper part and a small lower part, see fig. 5;

the crucible wall 2 and the induction coil 4 outside the crucible wall are columnar, and the crucible bottom 3 and the crucible bottom induction coil 10 below the crucible bottom are in a shape with taper and big top and small bottom, see fig. 6;

it will be appreciated that the crucible bottom induction coil 10 may be integral with the crucible side induction coil 4 in series connection with each other or may be a separate induction coil which is in force interaction with the crucible side induction coil 4.

In the present embodiment, since the intensity of the ampere force increases with an increase in the frequency of the electromagnetic field, a relatively large magnetic levitation force F can be obtained by increasing the output frequency of the induction power supply. However, increasing the frequency reduces the penetration depth of the electromagnetic field into the material, reducing smelting efficiency. Therefore, in the case of melting by using the crucible of the present embodiment, the frequency range of the induction power source should be set to be within a certain range higher than the frequency used for intermediate frequency induction melting, and may be selected within a range of 0.5kHz to 1000 kHz. In the case of smelting metal, it is preferable to use a supersonic induction power supply, and the frequency range is limited to 3kHz to 80kHz, and is preferably limited to 5kHz to 50 kHz. The frequency is determined in relation to the crucible size, and for crucibles with an inner diameter of less than 50mm, a frequency above 20kHz should be chosen, and for crucibles with an inner diameter of more than 200mm, a frequency below 8kHz should be chosen.

In order to enable the crucible to have better use effect and perfect function, the crucible can be provided with the following auxiliary measures:

in the present embodiment, in order to keep the temperature of the molten bath at the melting process and to increase the melting temperature, a metal or graphite crucible cover 11 may be attached to the upper opening of the crucible 1, see fig. 7. Preferably, the crucible cover 11 is also sewn into a flap-bonded structure, and the seamless crucible cover 11 blocks the path of the magnetic force lines passing through the upper opening of the crucible 1, so that a part of the electromagnetic field cannot enter the crucible.

In the present embodiment, in order to eliminate contamination of the material to be melted by the crucible 1, a coating layer may be prepared on the inner wall of the crucible. The coating material may be the same metals, alloys and compounds as the material to be melted, may be constituent components of the material to be melted, or may be metals, alloys and compounds having a melting point higher than the melting point of the material to be melted. The preparation method of the coating comprises thermal spraying, plasma spraying, magnetron sputtering and the like.

In the present embodiment, as shown in fig. 7, a crucible holder 12 is required for installing a metal crucible or a graphite crucible in a vacuum furnace, and the crucible holder 12 may be made of a metal material such as carbon steel, stainless steel, or copper, or may be made of a heat-resistant ceramic material. The crucible holder 12 of the metal material may be provided with a cooling device, and the copper crucible holder must have a water-cooling structure. A high temperature resistant insulating material 13 such as asbestos, aluminum silicate fiber, alumina, zirconia, magnesia, graphite, etc. is required to be interposed between the crucible frame 12 and the crucible bottom 3.

In this embodiment, the metal or alloy for producing the metal crucible should be a material having a melting point 300 ℃ or higher than the melting point of the material to be melted, and preferably a metal or alloy having a melting point 500 ℃ or higher than the melting point of the material to be melted. The materials of the metal crucible are practically used in many cases, for example, metals such as W, mo, nb, ir, pt, etc., and alloys thereof, for example, alloys such as W-Mo, W-Re, ir-Rh, etc.

The embodiment also provides a preparation method of the metal/graphite crucible, and the method adopts a 3D printing technology. The printer apparatus includes, among other things, an energy beam emitter 17, an energy beam scanning system 18, a shaping system 19, a powder supply system 20, and a control system 21, see fig. 8. The printing process is performed under the condition of gas protection, and the protection gas can be nitrogen, argon or other gases with protection. The preparation of the crucible of the invention by 3D printing reduces the manufacturing difficulty, particularly for crucibles of complex shape, and for crucibles having particular requirements for the geometry of the slit of the flap and for the slit width to vary with the height of the crucible.

Specifically, the method comprises the following steps:

step 1, inputting a 3D design drawing of a structure of a crucible 1 into a control system 21 of a printer, and loading metal powder or graphite powder 22 for manufacturing the crucible into a powder supply system 20 of the printer;

step 2, lifting a workbench 24 in a forming system 19 onto a working surface, and conveying powder 22 to the surface of the workbench 24 by using a powder conveying mechanism 25 in a powder supply system 20 to form a powder layer with uniform thickness; preferably, the powder feeding mechanism 25 is a powder feeding roller.

And 3, starting the energy beam generator 17 to enable the energy beam 26 to be emitted onto the powder layer on the surface of the workbench through the energy beam scanning system 18, and controlling the energy beam scanning system 18 by the control system 21 according to the crucible design drawing to enable the energy beam 26 to scan according to the structure of the bottom layer profile of the crucible, so that the powder at the scanning position is burned and fused to form a first layer structure 27 of the crucible.

Step 4, the forming piston 23 is utilized to reduce the height of the workbench 24 equal to the thickness of one layer of raw material powder, the powder feeding mechanism 25 in the powder feeding system is utilized to lay a second layer of powder on the surface of the workbench 24, and the energy beam 26 is controlled to scan on the new powder layer, so that a second layer structure 27 of the crucible is formed.

And 5, repeating the step 4, so that the whole structure of the crucible can be prepared from the bottom layer to the top layer.

And 6, purging the excessive powder which exists in the position where the energy beam 26 is not scanned into the recovery box. The technology can be used for manufacturing the metal crucible and the graphite crucible with very precise split structures.

In the 3D printing technique of the present invention, the energy beam may be of various types such as a laser beam, an electron beam, a plasma beam, and the like. It is understood that any 3D printing apparatus capable of printing metal/graphite can be used to prepare the metal/graphite crucible, and is within the scope of the present invention.

The embodiment also provides a plurality of methods for smelting materials by using the metal/graphite crucible, which specifically comprises the following steps:

first aspect:

and 1, after the materials are loaded into the crucible 1, vacuumizing the smelting chamber 14, or filling argon after vacuumizing, and then starting an induction power supply to heat the materials.

And 2, after the materials begin to melt and a molten pool appears, increasing the power to enable the molten pool 7 to appear in a suspension state. The suspension state is marked by the degree of hump formed by the molten pool 7, and the diameter of hump is less than 2/3 of the inner diameter of the crucible. In this state, the outer wall of the bath 7 is sufficiently separated from the inner wall of the crucible, with the best melting effect.

And 3, carrying out casting work after preserving heat for a period of time in a suspension state. In some embodiments, the casting process employs a tip-over casting technique, in which the crucible 1 is tipped over by a tip-over device, and a melt of material is poured into the mold 16 to cool, as shown in fig. 9. In other embodiments, the casting process may also employ bottom casting techniques employing a crucible 1 with a bottom casting nozzle at the bottom 3 of the crucible, the bottom casting nozzle being shielded by a crucible plug 15 during smelting, the crucible plug 15 being moved during casting to enable the material melt to be poured along the bottom casting nozzle into a mold 16 below the crucible, see FIG. 7. In both casting modes, the power of the induction power supply is maintained during casting to maintain the molten pool in suspension and flow out of the mold 16, so that the material melt is almost completely injected into the mold 16 with little material remaining in the crucible.

Second aspect:

as shown in fig. 10, the crucible of the present embodiment can be used for a distillation purification technique of a metal. The auxiliary equipment and process used for the distillative purification of metals are similar to those used for smelting, but it is necessary to install a metal vapor receiver 30 above the crucible 1 to receive the metal vapor 31 generated by the bath 7, and to condense and crystallize the gaseous metal atoms thereon to form metal crystals 32. It can be understood that the heating temperature of the technology is high, the process time is long, the requirement on impurity content is very strict, and the technical requirement is hardly met by adopting the existing non-split metal crucible or graphite crucible.

Third aspect:

as shown in fig. 11, the crucible 1 of the present embodiment can produce a product of excellent quality by using the pull-down ingot technique. Specifically, the crucible bottom 3 and the crucible wall 2 are provided with a separation structure, the crucible bottom 3 is used as a crystallizer to be installed at the lower opening of the crucible wall 2, the lower end surface of the crucible bottom 3 is provided with a pull rod 33 which extends downwards, and the pull rod 33 extends to the lower side of the smelting chamber 14 through vacuum sealing and is combined with a pulling ingot driver. After the materials are melted, a pulling ingot driver is started, a pull rod 33 is pulled down, so that a molten pool 7 on the crucible bottom 3 moves out of the crucible downwards along with the pull rod 33 to be cooled and solidified to form an ingot blank 34. To obtain the desired product quality, the speed of the pull-down process must be very low, typically limited to a range of 0.1mm/min to 100mm/min, and for most materials, the pull-down speed is limited to a range of 1mm/min to 20 mm/min. The advantage of using the drop-down ingot technique is that the solidification process of the liquid material is a sequential solidification from bottom to top, so the ingot 34 is very dense in material and free of metallurgical defects such as shrinkage cavities, voids, porosity and cracks. It will be appreciated that prior art non-split metal/graphite crucibles cannot be used in the pull down ingot art because the temperature of such crucibles is high and the process of pulling down the ingot requires a significant amount of time, typically several hours or more, during which time the contamination of the material by the high temperature crucible walls is significant and can result in rejection of the product of the pull down ingot.

Fourth aspect:

as shown in fig. 11, the crucible of the present embodiment can also be used for directional solidification techniques. The directional solidification technique is a technique requiring a higher requirement than the pull-down ingot technique, and requires that a temperature field device 35 is arranged in the process of pulling down the pull-down ingot so that the molten pool 7 above the crucible bottom 3 solidifies under the condition of axial temperature gradient when moving downwards out of the lower mouth of the crucible along with the pull rod 33, forming an ingot blank 34 of directional crystallization, and obtaining the purification effect. It will be appreciated that impurities in the bath 7 act as a core for non-spontaneous nucleation and disrupt the directional crystallisation process, so that the cleanliness of the bath must be maintained during directional solidification. In addition, the directional solidification process requires very low pull-down speeds, typically an order of magnitude lower than pull-down ingot technology. In the face of such stringent impurity requirements and longer metallurgical processes, neither prior art metal crucibles nor graphite crucibles can be used.

Fifth aspect:

as shown in fig. 12, the crucible of the present embodiment can be used to melt a compound or semiconductor that is not conductive at room temperature using an induction power source, and ignition techniques are required for melting such materials. Specifically, the conductive ignition material 36 is embedded in the non-conductive compound or semiconductor material 37, the inductive power supply is activated to preheat the material to a conductive temperature, the high temperature material is induced to generate heat and melt under the influence of the electromagnetic field, and then the melting range is expanded to the surrounding until all of the material melts. Preferably, the ignition material 36 is generally metal or graphite. It will be appreciated that with prior art crucibles, the ignition material 36 cannot be used inside the material because the electromagnetic field cannot enter the interior of the crucible 1. In this case, although the crucible is heated up under the action of the electromagnetic field to heat the material to the conductive temperature as an ignition material, the crucible wall always pollutes the material in the whole melting process of the material, and the pollution is serious because the temperature of the crucible is high.

In the above five aspects, under the condition of using the crucible of the present embodiment, the cooled inert gas, or the liquid inert gas such as liquid argon, may be injected to the outer wall of the crucible during the melting process. The method for realizing the technology comprises the following steps: with reference to fig. 9, a gas injection ring 28 is provided on the side and/or under the crucible, and a plurality of upwardly opening gas nozzles 29 are provided on the ring, and gas lines are coupled to the injection ring 28 from outside the smelting furnace by vacuum sealing. And when the induction power supply is started to heat the materials, or after the induction power supply is started, a valve for conveying cooled inert gas or liquid inert gas is opened, so that low-temperature gas is sprayed to the crucible through the air spraying ports 29 of the spraying ring 29, and the outer wall of the crucible is cooled. The technology can reduce the temperature of the crucible in the smelting process, reduce the loss of crucible materials and reduce the pollution of the crucible to the materials. It will be appreciated that the above-described means of cooling the crucible cannot be employed with prior art crucibles because the temperature of the material in the prior art crucible is provided by the crucible.

Specific examples:

the present invention provides specific embodiments for a better understanding of the present invention.

Example 1

The vacuum induction melting equipment consists of an induction power supply with the power of 100kW and the frequency of 2500Hz and a vacuum melting chamber with the inner diameter of 1200mm, a tungsten crucible with the inner diameter of 300mm and the height of 280mm is arranged, and a molybdenum crystallizer is arranged above the crucible. The apparatus was used for distillation of metal with a yield of 100kg of metal Dy per furnace. In the prior art, an electromagnetic field of an intermediate frequency power supply heats a tungsten crucible, heat is transferred to dysprosium materials after the tungsten crucible is heated, the distillation process is completed by preserving heat for 5 hours at the temperature of 2000 ℃, and the tungsten content in a distilled product is more than 1000ppm. Under the production process conditions, the service life of the tungsten crucible is less than 100 times.

When the technique of this embodiment was adopted, the size of the tungsten crucible was unchanged with an induction power supply of 100kW at a frequency of 5000Hz, but the whole was divided into 36 flaps with a flap slit width of 2mm. A gas injection ring is arranged below the tungsten crucible, 8 upward opening gas nozzles are arranged on the ring, and a liquid argon pipeline is combined to the injection ring through vacuum sealing. And after the induction power supply is started, a liquid argon valve is opened, so that the low-temperature argon is sprayed to the crucible through the air nozzle of the spraying ring. During the heating process, the dysprosium metal in the crucible is directly heated, melted and evaporated under the action of the electromagnetic field. With the new technology, the time for finishing the distillation process is shortened to 3 hours, and the tungsten content in the distilled product is less than 300ppm. The new technology not only does not need the tungsten crucible to have very high temperature, but also receives the cooling function, so that the service life of the crucible is prolonged to more than 500 times.

Example 2

The prior art crucible is adopted, the smelting equipment consists of a high-frequency power supply with the power of 60kW and the frequency of 100kHz and a smelting chamber with the inner diameter of 500mm, and the tantalum crucible with the inner diameter of 60mm is provided for smelting high-purity aluminum oxide, and the smelting quantity is 500g and the temperature is 2200 ℃. The alumina smelted by the method contains 600ppm of impurity Ta, and the quality is not satisfactory.

The invention adopts a tantalum crucible with the gap width of 0.4mm and divided into 20 segments to replace a crucible without segments to smelt alumina crucible, and a metal aluminum ring is embedded in the crucible as an ignition material. After the induction power supply is started, the aluminum ring is heated and burned, and the heat generated by the aluminum ring heats the aluminum oxide to obtain the electric conductivity. When heating is continued, the alumina is completely melted. The alumina obtained by the treatment has an impurity content lower than 100ppm.

Example 3

The traditional process for preparing Mo-Re alloy targets is powder metallurgy technology.

The Mo-Re alloy casting target material is prepared by the magnetic levitation melting technology of the embodiment. The device consists of a superaudio power supply with the power of 200kW and the frequency of 12kHz and a vacuum chamber with the inner diameter of 1000mm, wherein a crucible adopts a Mo crucible with the inner diameter of 200mm, the crucible is divided into 30 segments, and the segment gap is 1mm. A Mo coating is prepared on the inner wall of the crucible by a plasma spraying technology. The crucible is filled with 80kg of metallic Mo and metallic Re, the smelting temperature is 2800 ℃, the materials are completely melted after 20 minutes of smelting time, and the materials are cast into plate-shaped target blanks after 3 minutes of heat preservation. The slab has high compactness.

Example 4

A high-purity copper alloy is smelted by a superaudio power supply with the power of 100kW and the frequency of 10kHz in a vacuum chamber by using a graphite crucible with the inner diameter of 300mm and the high purity copper alloy with 32 pieces of high purity. The vacuum chamber was evacuated to 3x10 ^-4 And (3) starting an induction power supply to heat the copper alloy raw material, melting, and casting by using a tilting casting technology to obtain the copper alloy rod with the diameter of 60 mm. Analysis showed that the C content of the alloy was less than 10ppm, whereas the C content of the copper alloy product melted with the non-split graphite crucible was higher than 100ppm.

The foregoing is illustrative of the best mode of carrying out the invention, and is not presented in any detail as is known to those of ordinary skill in the art. The protection scope of the invention is defined by the claims, and any equivalent transformation based on the technical teaching of the invention is also within the protection scope of the invention.

Claims

1. A crucible comprises a crucible wall and a crucible bottom, wherein the outer side of the crucible wall surrounds an induction coil;

the crucible is made of metal or graphite;

the crucible is characterized by being provided with slits along the height direction of the crucible, so that the crucible is formed into a structure formed by combining a plurality of petals, and slits between adjacent petals form gaps.

2. The crucible as recited in claim 1, wherein: the metal is a metal or alloy with a melting point higher than that of the smelted material by more than 300 ℃.

3. The crucible as recited in claim 1, wherein: the width of the gap varies in the height direction of the crucible.

4. The crucible as recited in claim 1, wherein: the slit extends from the highest point of the crucible to the lowest point of the crucible;

alternatively, the crucible is left at a certain height without a gap.

5. The crucible as set forth in claim 3 or 4, wherein: the gap is a diagonal, curved or serpentine line extending between the upper and lower end surfaces of the crucible.

6. The crucible as recited in claim 1, wherein: a crucible bottom induction coil is arranged below the crucible bottom.

7. The crucible as recited in claim 6, wherein: the crucible and the induction coil are configured into a shape with taper and big top and small bottom;

alternatively, the crucible wall and the induction coil are columnar, and the crucible bottom induction coil are configured into a shape with taper and big top and small bottom.

8. The crucible as recited in claim 1, wherein: the upper opening of the crucible is provided with a metal or graphite crucible cover, and the crucible cover is slotted to form a structure with a flap.

9. A method of making the crucible of any one of claims 1-8, comprising:

10. A smelting method using the crucible of any one of claims 1 to 8, comprising:

s1, after a material is filled into a crucible, vacuumizing a smelting chamber, or filling argon after vacuumizing, and then starting an induction power supply to heat the material; s2, increasing power after the materials begin to melt and form a molten pool, so that the molten pool is in a suspension state; s3, carrying out casting work after preserving heat for a period of time in a suspension state;

or S1, after the materials are filled into a crucible, vacuumizing a smelting chamber, or filling argon after vacuumizing, and then starting an induction power supply to heat the materials; s2, increasing power after the materials begin to melt and form a molten pool, so that the molten pool is in a suspension state; s3, receiving metal vapor generated by a molten pool through a metal vapor receiver arranged above the crucible, and condensing and crystallizing gaseous metal atoms on the metal vapor to form metal crystals;

or S1, the crucible bottom and the crucible wall are provided with a separation structure, a pull rod extending downwards is arranged on the lower end surface of the crucible bottom, and the pull rod extends to the lower surface of the smelting chamber through vacuum sealing and is combined with the ingot pulling driver; s2, after the materials are filled into the crucible, vacuumizing a smelting chamber, or filling argon after vacuumizing, and then starting an induction power supply to heat the materials; s3, increasing power after the materials begin to melt and form a molten pool, so that the molten pool is in a suspension state; s4, starting a pull ingot driver after the materials are melted, and pulling down a pull rod to enable a molten pool on the bottom of the crucible to move out of the crucible downwards along with the pull rod to be cooled and solidified to form an ingot blank;

or S1, a separating structure is arranged between the crucible bottom and the crucible wall, a pull rod extending downwards is arranged on the lower end face of the crucible bottom, the pull rod extends to the lower side of the smelting chamber through vacuum sealing and is combined with an ingot pulling driver, and a temperature field device is arranged below the crucible; s2, after the materials are filled into the crucible, vacuumizing a smelting chamber, or filling argon after vacuumizing, and then starting an induction power supply to heat the materials; s3, increasing power after the materials begin to melt and form a molten pool, so that the molten pool is in a suspension state; s4, starting a pull ingot driver after the materials are melted, and pulling down a pull rod to enable a molten pool on the bottom of the crucible to solidify under the condition of axial temperature gradient when the molten pool moves out of a lower opening of the crucible downwards along with the pull rod, so as to form an ingot blank of directional crystallization;

or S1, after a non-conductive compound or semiconductor material is filled into a crucible, embedding a conductive ignition material into the non-conductive compound or semiconductor material; s2, vacuumizing a smelting chamber, or filling argon after vacuumizing, starting an induction power supply to preheat the material to a conductive temperature, enabling the high-temperature material to form induction current under the action of an electromagnetic field, heating and melting from the inside, and expanding a melting range to the periphery until the material is completely melted; s3, increasing power after the materials begin to melt and form a molten pool, so that the molten pool is in a suspension state; s4, carrying out casting work after preserving heat for a period of time in a suspension state.