EP0739667B1 - Method of casting metal and apparatus therefor - Google Patents
Method of casting metal and apparatus therefor Download PDFInfo
- Publication number
- EP0739667B1 EP0739667B1 EP96302915A EP96302915A EP0739667B1 EP 0739667 B1 EP0739667 B1 EP 0739667B1 EP 96302915 A EP96302915 A EP 96302915A EP 96302915 A EP96302915 A EP 96302915A EP 0739667 B1 EP0739667 B1 EP 0739667B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- mould
- mould chamber
- chamber
- molten metal
- melting furnace
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D18/00—Pressure casting; Vacuum casting
- B22D18/06—Vacuum casting, i.e. making use of vacuum to fill the mould
Definitions
- the present invention relates to a method of casting a metal and an apparatus therefor. More particularly, the present invention relates to a novel method of casting metal and an apparatus for the application of such method, which permits achievement of a high-quality casting free from entrapment of impurities, gas contamination or gas defects, and is particularly, but not exclusively, useful for casting active metals such as titanium.
- the present inventors carried out extensive studies on means for obtaining such high-quality casting products, and have established a method permitting casting of an active metal, in particular for active and high-melting-point metals such as titanium and alloys thereof, which allows casting at a high efficiency with a high productivity.
- the method thus established is essentially characterized by the combination of semi-levitation melting a metal, which involves melting a metal while partially magnetic-floating the metal, and reduced-pressure suction casting.
- This permits melting and casting of an active metal such as titanium by the semi-levitation melting process which is different from conventional processes using a refractory crucible, thereby inhibiting deterioration of quality caused by refractory contamination. It also makes it possible to conduct continuous melting and casting, and to carry out casting of highly uniform castings and ones with complicated shapes by the application of the reduced-pressure casting process.
- the semi-levitation melting process forming a feature of this method will be described in further detail below.
- This process is a kind of levitation (magnetic floating) melting process which comprises induction-heating a material charged in a melting crucible, and holding the resultant molten material without causing contact with the inner wall of the melting crucible.
- the levitation melting process is one of the melting processes which allow, when melting a metallic material charged in a melting crucible, the prevention of contamination of the molten metal from chemical reactions caused by contact of the metal with the inner wall of the crucible, thereby achieving an improvement in quality.
- the process of levitation melting can be further divided into two processes: full-levitation melting process, which comprises fully floating a molten metal within the furnace by the action of electromagnetic force; and semi-levitation melting which comprises using a water-cooled copper crucible, and causing the molten metal to float by electromagnetic force while keeping the bottom of the material in a solidified state.
- An outline of the semi-levitation melting process is as follows.
- a peripheral wall of the main body which is formed into a cylindrical shape and has a bottom, is circumferentially divided to form a plurality of segments into which cooling water is supplied in circulation.
- the individual segments are insulated from each other with an insulating material.
- Doughnut-shaped high-frequency induction coil turns are arranged at prescribed annular intervals on the outside of the water-cooled copper crucible. The material is induction-heated upon charging the material into the crucible by supplying high-frequency current to the induction coil.
- the material Upon heating the material to a prescribed temperature, the material partially melts, while the lower material in contact with the bottom of the water-cooled copper crucible is kept in its solidified state.
- the molten material is kept floating in the non-contact state relative to the inner wall of the crucible under the effect of electromagnetic force generated by the penetration of the molten material into the crucible.
- An example of a semi-levitation melting process is known from JP-A-04/182056.
- levitation melting as a melting process having the features as described above is simply called “levitation melting” hereafter.
- the present invention provides a method of casting a molten metal comprising the steps of:
- the pressure within the mould chamber and the space above the levitation melting furnace is reduced to below 26.7 kPa (200 torr), most preferably below 13.3 kPa (100 torr).
- the pressure is increased by between 6.67-66.7 kPa (50 to 500 torr) in the space above the levitation melting furnace by an atmosphere control mechanism.
- the present invention also provides apparatus for casting a molten metal comprising a levitation melting furnace, a mould chamber arranged above the levitation melting furnace and a gas-permeable mould housed within said mould chamber, said mould chamber further including a suction pipe for delivering molten metal to the mould having one end in communication with the mould and the other end arranged to be lowered into the levitation melting furnace, characterised in that said mould chamber comprises a double-structure mould comprising an outer mould chamber having an outer cover to close the outer mould chamber, an inner mould chamber having an inner cover to close the inner mould chamber, said inner mould chamber housing said mould and including said suction pipe for delivering molten metal to said mould, and in that an atmosphere control mechanism is provided to blow an inert gas into a space above the levitation melting furnace to cause molten metal to rise up through the suction pipe.
- a sliding mechanism is provided to lower the mould chamber toward the levitation melting furnace.
- the mould chamber comprises an inner and an outer mould chamber which are slidably coupled together.
- a mould keeper is arranged to press and keep the mould in the inner mould chamber.
- the sliding mechanism has an elastic body, of which compression causes descent and of which repulsive force causes accent.
- the atmosphere control mechanism is provided with exhaust pressure reducing means and inert gas supply means.
- the interior of the mould is kept under a reduced pressure or under vacuum, the reduced pressure or vacuum being retained due to the double structure of the mould chamber, and the molten metal being cast by pressurising.
- defects resulting from entrapment by the atmosphere gas do not occur, thus permitting the casting of a uniform structure.
- the entire operations of casting including stabilization and fine adjustment of the casting speed are very efficiently accomplished by the generation of a difference in pressure caused by blowing of inert gas.
- the present invention is suitable for casting an active metal such as titanium, and because of the absence of inclusions caused by crucible refractories, is effective for ferrous castings.
- the preferred casting apparatus of the present invention comprises a levitation melting furnace 1, and a mould chamber 4 which holds a gas-permeable mould 2 in the interior thereof into which the molten metal is to be cast.
- a suction pipe 3 is also provided for sucking up the molten metal into this mould 2.
- the mould 2 is not limited to a precision-casting mould based on the lost wax process, but may consist of any of various moulds using sand, a metal or the like, which so long as it is permeable may be used.
- the mould chamber 4 has a double structure comprising an inner mould chamber 41 having a mould 2 arranged therein which connects a suction pipe 3 to the mould 2, with an outer mould chamber 42 forming the outer periphery thereof.
- the casting apparatus is provided with a sliding mechanism which moves the inner mould chamber 41 and the outer mould chamber 42 independently up and down, and an atmosphere control mechanism.
- an inner cover 411 for the inner mould chamber 41 and a mould keeper 412 for pressing the mould 2 from above are made vertically slidable, and an outer cover 421 for the outer mould chamber 42 is provided.
- the inner cover 411 and the outer cover 421 are made vertically slidable by independently operating cylinder mechanisms 6 and 7.
- Outer springs 9 are provided between the outer mould chamber 42 and a base 8, and inner springs 10 between the flange portion of the inner mould chamber 41 and the staged portion of the outer mould chamber 42.
- the suction pipe 3 is consequently pulled out from the molten metal.
- the mould chamber 4 is more perfectly closed under the effect of the double structure comprising the inner mould chamber 41 and the outer mould chamber 42, and casting of a product free from defect at meniscus, having a uniform structure and containing minimum impurities is made possible by the absence of entanglement by the atmosphere gas and uniform ascent of molten metal, resulting from casting by reduced pressure and inert gas pressurizing. Control of atmosphere is also easier.
- the outer springs 9, the inner springs 10 and the cylinder piston mechanisms 6 and 7 for ensuring the close contact and sliding property of the inner mould chamber 41 and the outer mould chamber 42 are not limited to particular ones.
- Inert gas is supplied for sealing the furnace during levitation melting, and is continued throughout the entire period of casting except for the period of pressure reduction before casting.
- a suction pipe made from the same metal as the molten metal or base metal of the molten alloy By using a suction pipe made from the same metal as the molten metal or base metal of the molten alloy, the wear tolerance of the suction pipe is increased. Thus, it is preferable to use a suction pipe made from Ti for melting a Ti-Base-alloy.
- the atmosphere in the mould is controlled by the double structure of the mould chamber and the pressure reduction and casting by pressuring of the inert gas make it possible to cast a product with the least defects end excellent uniformity of structure. Furthermore, the pressure difference achieved by the pressure reducing conditions and inert gas blowing permit efficient casting including stabilization and fine adjustment of the casting speed, with a largely improved productivity.
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Furnace Details (AREA)
- Crucibles And Fluidized-Bed Furnaces (AREA)
- Casting Support Devices, Ladles, And Melt Control Thereby (AREA)
Description
- lowering said outer cover to close said outer mould chamber and to bring said outer mould chamber into close contact with said levitation melting furnace;
- lowering said inner cover to close said inner mould chamber;
- lowering said inner mould chamber toward said levitation melting furnace to immerse the end of said suction pipe into the molten metal;
- blowing an inert gas at an increased pressure into the space above the levitation melting furnace to cause molten metal to rise up through the suction pipe and to be cast into the mould;
- withdrawing the suction pipe from the molten metal by raising said inner mould chamber; and
- raising said outer mould chamber from said levitation melting furnace.
Claims (10)
- A method of casting a molten metal comprising the steps of:levitation-melting a metal in an inert atmosphere in a levitation melting furnace (1) under atmospheric pressure, thereby forming molten metal (5);providing a mould chamber positioned above the furnace, and a gas-permeable mould (2) housed within said mould chamber, said mould chamber further including a suction pipe (3) for delivering molten metal to said mould;reducing the pressure in said mould chamber (41,42) and a space (A) above the levitation melting furnace (1) to below atmospheric pressure;lowering said mould chamber (41) and said gas permeable mould toward said levitation melting furnace (1) to immerse an end of said suction pipe (3) into the molten metal (5), the other end of the suction pipe being in communication with the mould (2);raising said mould chamber (4) to withdraw the suction pipe (3) from the molten metal (5); andreturning the pressure in the space (A) above the levitation melting furnace (1) and in the mould chamber (41,42) to atmospheric pressure;lowering said outer cover (421) to close said outer mould chamber (42) and to bring said outer mould chamber into close contact with said levitation melting furnace (1) ;lowering said inner cover (411) to close said inner mould chamber (41);lowering said inner mould chamber (41) toward said levitation melting furace (1) to immerse the end of said suction pipe (3) into the molten metal (5);blowing an inert gas at an increased pressure into the space (A) above the levitation melting furnace (1) to cause molten metal to rise up through the suction pipe and to be cast into the mould (2);withdrawing the suction pipe (3) from the molten metal (5) by raising said inner mould chamber (4); andraising said outer mould chamber (42) from said levitation melting furnace (1).
- A method as claimed in claim 1, wherein the pressure in the double-structure mould chamber (41,42) and the space (A) above the levitation melting furnace (1) is reduced to below 26.7 kPa (200 torr).
- A method as claimed in claim 2, wherein the pressure is reduced to below 1.33 kPa (100 torr).
- A method as claimed in any of claims 1, 2 or 3, wherein the molten metal (5) is cast into the mould (2) under a pressure increase of between 6.67-66.7 kPa (50 to 500 torr).
- Apparatus for casting a molten metal comprising a levitation melting furnace (1), a mould chamber (41,42) arranged above the levitation melting furnace and a gas-permeable mould (2) housed within said mould chamber, said mould chamber further including a suction pipe (3) for delivering molten metal to the mould having one end in communication with the mould and the other end arranged to be lowered into the levitation melting furnace, characterised in that said mould chamber comprises a double-structure mould comprising an outer mould chamber (42) having an outer cover (421) to close the outer mould chamber, an inner mould chamber (41) having an inner cover (411) to close the inner mould chamber, said inner mould chamber (41) housing said mould (2) and including said suction pipe (3) for delivering molten metal to said mould (2), and in that an atmosphere control mechanism (12, 120) is provided to blow an inert gas into a space (A) above the levitation melting furnace (1) to cause molten metal to rise up through the suction pipe.
- Apparatus as claimed in claim 5, wherein a sliding mechanism is provided to lower the inner and outer mould chambers of the double-structured mould chamber (41,42) toward the levitation melting furnace (1).
- Apparatus as claimed in claim 6, wherein the sliding mechanism is resiliently biased to urge the mould chamber (41,42) away from the levitation melting furnace (1).
- Apparatus as claimed in any of claims 5, 6 or 7, wherein the inner and outer mould chambers are slidably coupled together.
- Apparatus as claimed in any of claims 5 to 8, wherein a mould keeper (412) is provided to retain the mould (2) in position.
- Apparatus as claimed in any of claims 5 to 9, wherein the atmosphere control mechanism (12,120) comprises a pump, an exhaust port (120) and an inlet (12).
Applications Claiming Priority (7)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP10147695 | 1995-04-25 | ||
JP101476/95 | 1995-04-25 | ||
JP10147695 | 1995-04-25 | ||
JP7153008A JP2830777B2 (en) | 1995-04-25 | 1995-06-20 | Metal casting method and apparatus |
JP15300895 | 1995-06-20 | ||
JP153008/95 | 1995-06-20 | ||
US08/637,416 US5722481A (en) | 1995-06-20 | 1996-04-25 | Method for casting metal and apparatus therefor |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0739667A1 EP0739667A1 (en) | 1996-10-30 |
EP0739667B1 true EP0739667B1 (en) | 2001-11-07 |
Family
ID=27309472
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP96302915A Expired - Lifetime EP0739667B1 (en) | 1995-04-25 | 1996-04-25 | Method of casting metal and apparatus therefor |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP0739667B1 (en) |
JP (1) | JP2830777B2 (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN112935223A (en) * | 2019-12-11 | 2021-06-11 | 科华控股股份有限公司 | Structure for preventing sealing failure by modifying vacuum suction casting profiling cylinder outside suction casting chamber |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3544757A (en) * | 1967-05-15 | 1970-12-01 | Material Transformation Associ | Method of melting a levitated mass |
JPS5954458A (en) * | 1982-09-20 | 1984-03-29 | Hitachi Ltd | Method and device for casting by bottom running of molten metal |
US4738713A (en) * | 1986-12-04 | 1988-04-19 | The Duriron Company, Inc. | Method for induction melting reactive metals and alloys |
DE69021103T2 (en) * | 1989-03-17 | 1996-04-11 | Pcc Composites Inc | Pouring device and method. |
JP2541341B2 (en) * | 1990-05-15 | 1996-10-09 | 大同特殊鋼株式会社 | Precision casting method and precision casting apparatus for Ti and Ti alloy |
JP2576685B2 (en) * | 1990-11-19 | 1997-01-29 | 大同特殊鋼株式会社 | Precision casting equipment |
JPH05131265A (en) * | 1991-11-08 | 1993-05-28 | Daido Steel Co Ltd | Pipe joint and production thereof |
-
1995
- 1995-06-20 JP JP7153008A patent/JP2830777B2/en not_active Expired - Fee Related
-
1996
- 1996-04-25 EP EP96302915A patent/EP0739667B1/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
EP0739667A1 (en) | 1996-10-30 |
JPH0910917A (en) | 1997-01-14 |
JP2830777B2 (en) | 1998-12-02 |
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