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WO1994028366A1 - Four a induction modulaire - Google Patents

Four a induction modulaire Download PDF

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Publication number
WO1994028366A1
WO1994028366A1 PCT/AU1994/000289 AU9400289W WO9428366A1 WO 1994028366 A1 WO1994028366 A1 WO 1994028366A1 AU 9400289 W AU9400289 W AU 9400289W WO 9428366 A1 WO9428366 A1 WO 9428366A1
Authority
WO
WIPO (PCT)
Prior art keywords
passageway
pot
inductor
duct
metal
Prior art date
Application number
PCT/AU1994/000289
Other languages
English (en)
Inventor
Delwyn Gloria Jones
Richard Payling
Raymond Osterberg
Original Assignee
Bhp Steel (Jla) Pty. Ltd.
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Bhp Steel (Jla) Pty. Ltd. filed Critical Bhp Steel (Jla) Pty. Ltd.
Priority to AU68382/94A priority Critical patent/AU674085B2/en
Publication of WO1994028366A1 publication Critical patent/WO1994028366A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating
    • H05B6/16—Furnaces having endless cores
    • H05B6/20—Furnaces having endless cores having melting channel only
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B14/00—Crucible or pot furnaces
    • F27B14/06—Crucible or pot furnaces heated electrically, e.g. induction crucible furnaces with or without any other source of heat
    • F27B14/061—Induction furnaces
    • F27B14/065—Channel type
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating
    • H05B6/36—Coil arrangements
    • H05B6/367—Coil arrangements for melting furnaces

Definitions

  • This invention relates to electric induction furnaces of the kind known as submerged-resistor furnaces or channel induction furnaces.
  • Such furnaces may be used to melt non-ferrous metals and metallic alloys.
  • they comprise a refractory hearth or pot adapted to hold a charge of metal to be melted and a so-called inductor.
  • the inductor is essentially a transformer comprising an endless ferro-magnetic core, a primary winding sleeved on said core, and a secondary circuit linking said core and comprising a loop of molten metal in a secondary passageway defined by a refractory body.
  • the secondary passageway is generally U-shaped and opens at its ends into the interior of the furnace pot, so that the secondary circuit is completed through the pool of metal in the pot. At start up it is necessary to charge the passageway and pot with sufficient molten metal to establish the secondary circuit. Once started, it is desirable for the furnace to run continuously for an extended period, during which further liquid or solid metal is charged into the pot from time to time.
  • a conventional inductor comprises a refractory body of sufficient strength to withstand the considerable hydrostatic head of molten metal in the lower parts of the secondary passageway, and to assist in maintaining the integrity of the furnace pot having regard to the fact that the pot has openings formed in it to provide communication between the interior of the pot and the passageway within the refractory body.
  • the ferro-magnetic core and the primary winding or windings are normally housed within the refractory body.
  • a major deficiency of prior known inductors is the tendency for cracks to form in the refractory body allowing molten metal to leak from the furnace or reach a primary winding, with consequent destruction or at least electrical failure thereof.
  • a failure requires the replacement of a prior known bolt-on inductor, then the level of liquid metal in the furnace pot has to be lowered to below the entrances of the secondary passageway or passageways. This is a troublesome and dangerous operation. It must be remembered that if a lot of metal is left in the pot, and as a result, or for some other reason, the replacement of a faulty inductor takes longer than intended, the residual metal in the secondary passageways of other inductors may freeze. In so doing the metal contracts and may destroy a sound inductor or inductors in its or their entirety.
  • An object of the present invention is to alleviate the above- indicated deficiencies of prior known furnaces and to provide a furnace of enhanced reliability.
  • the invention is founded on the appreciation that the pumping effect is dependent on the shape of the secondary passageway, and in particular on the shapes of the end parts of the passageway communicating with the pool of molten metal in the pot. If those end parts differ, so that the flow patterns in the circulating metal near the ends of the passageway also differ, it has been found that pressure differentials created at the ends of the passageway are such that it becomes unnecessary for the passageway to be below the liquid level in the pot while to achieve circulation of molten metal around the secondary circuit at velocities of some metres per second.
  • the inductor structure to be relatively lightly constructed; it enables the inductor to be of modular form, in that said tubular duct on the one hand and the core and primary winding on the other hand may be provided as separable, independently replaceable units, and in that the inductor as a whole and the pot may likewise be separable, independently replaceable units; it enables a reliable pot devoid of secondary passageway entrance holes to be used; and it enables, for example, one spare tubular duct to be retained for servicing one or more furnaces in lieu of a complete stand-by furnace.
  • the invention consists in a modular inductor for an induction furnace of the kind comprising a pot having an upper open mouth and which is adapted to hold a pool of molten metal having a maximum liquid level, said inductor comprising duct means defining an open ended, secondary passageway having two end parts and an intermediate part, an endless ferro-magnetic core encircling that part of the duct means defining the intermediate part of the passageway, a primary winding sleeved on the core, and connector means whereby the intermediate part of the passageway may be connected to suction means; said duct means being positionable so that the end parts of the passageway extend into such a pot from above said liquid level to below that level so that, in use, the open ends of the passageway are submerged in the pool of molten metal, and being shaped so that one of the open ends of the passageway has a larger cross-sectional area than that of the other open end.
  • Figure 1 is a diagrammatic perspective view of a modular inductor according to the invention.
  • Figure 2 is a view similar to figure 1 of the duct means of the inductor of figure 1.
  • Figure 3 is a centre plane section of the duct means of figure 2.
  • the illustrated inductor comprises duct means 4, a ferro-magnetic core 5 and a primary winding 6 sleeved upon the core 5.
  • the duct means 4 comprise an inverted U shaped, rigid tubular duct, being, in this instance, a ceramic pipe 7 and an asymmetric canoe 8.
  • the pipe 7 and canoe 8 define a secondary passageway having an intermediate part 9 and two end parts 10 and 11 respectively.
  • a spigot 12 extending from the pipe 7 constitutes connector means whereby the intermediate part 9 of the passageway may be connected to suction means, not shown.
  • the canoe 8 is essentially an open bottomed, asymmetric ceramic shell, united to the pipe 7.
  • the canoe 8 may be at least partly submerged in the pool of molten metal in a furnace pot having an open mouth through which the end parts of the pipe 7 may extend from above.
  • the hollow interior of the canoe 8 is filled with liquid metal, to put the end parts 10 and 11 of the secondary passageway into direct communication with the pool of molten metal. It will be seen, in this instance, that the enlargement of one end of the secondary passageway is created by the shape of the canoe 8.
  • the duct means may be no more than a U or other shaped pipe, in which event the passageway enlargement is due to the shape of an end part of the pipe itself.
  • the pipe ends are attached to a snout, that is to say an elongated body of refractory material defining a passage extending through it.
  • the snout may extend through a side wall of the pot or over the lip of the pot.
  • the upper end of the snout is open above the liquid level to allow connection of a tubular duct with end parts of different cross-sectional area.
  • the lower end of the snout lies under the level of liquid metal in the pot.
  • the snout is inclined to allow the inductor to be positioned away from the congested area above the pot while providing access to the pool of liquid metal in the pot.
  • the snout performs a similar function in relation to an inductor according to the invention as does the conventional throat used in relation to conventional, bolt on inductors in a conventional induction furnace, namely to provide a passage through which liquid metal enters and egresses the secondary passageway.
  • the relevant component provides an enlargement of one end of the passageway, and that end only, to provide different flow patterns near the respective entrances to the passageway, thereby optimising the pumping effect of the inductor.
  • mounting means are used that provide for independent support of the duct means 4, and of the core 5 and primary winding 6. This enables those items to be replaced independently of each other if need be.
  • the mounting means and the inductor as a whole may be flexible in design, as there is no particular limitation on the shape of the intermediate portion of the tubular duct.
  • the core 5 lies in a vertical plane suspended directly above the pot, and the intermediate part 9 of the secondary passageway is an inverted U shape with its crotch portion extending through the core window and its legs extending downwardly through the mouth of the pot.
  • the tubular duct may lie in one plane.
  • it may comprise a horizontally disposed U shaped intermediate part with down turned end parts dipping into the pool in the pot.
  • the lightness and independent mountability of the modular inductors allows a plurality of them to be positioned around the pot at elevations relative to the surface of the pool in the pot to accommodate such design concepts as the need to stir lower corners of the pot, or to direct molten metal directly at a strip being coated, either from above or below.
  • U shaped parts may be combined by sharing a common inlet passage to form a W shaped passageway.
  • the W shaped part should be energised by two primary coils, one for each side leg of the W, and preferably the cross- sectional area of the centre leg should be twice that of each of the two side channels to maximise the ease of flow.
  • the pot would be furnished with a lid to cover its mouth.
  • Such a lid would have clearance holes through it for the end parts the secondary tubular duct. It is preferably made from thermally insulating material, and is then relied upon to protect the primary winding or windings from heat radiated from the surface of the pool.
  • the pipe 7 is rigid enough to be self-supporting, for example it may be made from the material currently marketed under the trade mark MARSINT. That material is essentially a zirconia stabilised aluminium titanate. Alternatively, an unstabilised aluminium titanate ceramic, such as that marketed under the trade mark TIT, silica glass or other appropriate chemically stable, heat resistant material may be used.
  • the ceramic pipe of the duct means especially if constructed from
  • MASINT or TIT or equivalent and the suspension of the duct means above the pot, offer many advantages over the prior art. Because the ceramics are prefired there is no need for the long dry-out and preheat schedules required by conventional designs. Because of the superb thermal shock resistance of the preferred ceramics, the ceramic components may be placed in contact with the liquid pot metal much more quickly than for conventional inductors. Because of the location of the inductor and because it is independently mounted, when replacing inductors there is no need to pump out metal from the pot to below the throats of the inductors as in the conventional design which has inductors mounted on the side or bottom of the pot, thus saving time, reducing metal losses during pump-out, and the need for a stand-by pot. The combined advantages mean that an inductor can be changed in an hour compared with the 96 to 140 hours typically required with previous designs.
  • the spigot 12 is at highest point of the of the pipe 7 and enables a connection to be made to suction means, such as a vacuum pump or other evacuating means. This is required to enable liquid metal to be drawn into the secondary passageway so as to fill it at the time of start up of the furnace. Furthermore some ceramic materials suitable for use as duct material are porous, and when such material is used the evacuating means may be operated from time to time to dispose of accumulated air from within the secondary passageway.
  • the height of a liquid which can be supported by one atmosphere is such that the height, h, atmospheric pressure, p, density of the liquid, p, and acceleration due to gravity, g, are related by:
  • liquid aluminium with a density of 2400 kgm- 3 the height is 4.3m, while for liquid zinc with a density of 6600 kgm- 3 , the height is 1.6m.
  • Other liquid metals and liquid metal mixtures such as zinc/aluminium and zinc/aluminium/silicon, will vary according to their density. Such heights are therefore those which can be supported by suction means producing a perfect vacuum above the liquid metal in the secondary passageway. These heights represent the maximum possible height obtainable with a vacuum system attached to the duct.
  • suitable furnaces can conveniently be made with the tubular ducts rising to a height in the range of from 0.5 to 1.5m above the pot's minimum operating liquid level. A typical height of from 0.5 to 1.5m requires only a partial vacuum.
  • the vacuum required for 0.75m is about 0.83 bar, while for zinc it is about 0.52 bar.
  • Other liquids will vary according to their density.
  • the vacuum system required to raise and support the liquid in the passageway consists of a liquid ring vacuum pump, capable of operating over the pressure range 0.04 to 1 bar, a 12 L vacuum chamber, two gas inlet valves (the first one manual and the second one automatic) connected to a nitrogen gas supply, level detection means for upper and lower limits, and suitable vacuum hoses and connections and electrical controls.
  • the vacuum pump is operated continuously and the vacuum pressure first adjusted manually using the first gas inlet valve to set the liquid level in the passageway to just below that required, and then the vacuum and hence the liquid height is adjusted by turning the second gas inlet valve on or off automatically to keep the liquid metal between the upper and lower limits.
  • the lower limit must be such that the U or W shaped passageway is completely filled with liquid metal.
  • the vacuum chamber dampens the response of the system, in that the height of the liquid is controlled more by the vacuum pressure in the large chamber rather than by the relatively small volume in the spigot 12 or its equivalent.
  • An inert gas such as nitrogen gas is preferred so as to reduce oxidation of the liquid metal, though air or any other suitable gas may be used.
  • the enlargement of the end of the secondary passageway may be effected by shaping the tubular duct or canoe, as the case may be, in a variety of ways.
  • the passageway may be said to have an outwardly flared or belled mouth and the term "enlarged cross-sectional area" as applied to a passageway includes passageways having an outwardly flared or belled mouth.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Furnace Details (AREA)

Abstract

Un inducteur modulaire (4), destiné à un four à induction à canal, comprend une conduite de circuit secondaire, prenant la forme d'un tuyau en céramique (7) en U renversé, et une barquette en céramique (8) à fond ouvert. Une seule extrémité (11) du passage secondaire défini par la conduite est agrandie. Le tuyau (7) est entouré par un noyau ferromagnétique (5) doté d'une bobine primaire d'excitation (6) emmanchée sur lui. L'inducteur peut présenter son propre support et être placé en tant qu'entité indépendante au-dessus du creuset de four, les extrémités du passage communiquant directement avec une charge de métal fondu présente dans ce creuset. L'agrandissement d'une extrémité du passage permet d'augmenter le transit de métal. Un raccord (12) permet de connecter le passage à une pompe à vide et donc de remplir ce passage avec du métal fondu lors du démarrage.
PCT/AU1994/000289 1993-05-31 1994-05-31 Four a induction modulaire WO1994028366A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU68382/94A AU674085B2 (en) 1993-05-31 1994-05-31 Modular induction furnace

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
AUPL9098 1993-05-31
AUPL909893 1993-05-31
AUPL9597 1993-06-24
AUPL959793 1993-06-24

Publications (1)

Publication Number Publication Date
WO1994028366A1 true WO1994028366A1 (fr) 1994-12-08

Family

ID=25644465

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/AU1994/000289 WO1994028366A1 (fr) 1993-05-31 1994-05-31 Four a induction modulaire

Country Status (2)

Country Link
NZ (1) NZ266736A (fr)
WO (1) WO1994028366A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8158055B2 (en) * 2004-12-22 2012-04-17 Kenzo Takahashi Melting furnace with agitator

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU423999A1 (ru) * 1973-01-09 1974-04-15 Л. П. Пужайло, В. П. Полищук , В. К. Погорский Институт проблем лить Индукционная канальная печь
SU460422A1 (ru) * 1973-03-13 1975-02-15 Всесоюзный Научно-Исследовательский И Проектный Институт Вторичных Цветных Металлов Вниипвторцветмет Индукционна канальна печь
SU565188A1 (ru) * 1975-11-18 1977-07-15 Всесоюзный Научно-Исследовательский И Проектный Институт Вторичных Цветных Металлов Индукционна канальна печь
SU705231A1 (ru) * 1978-07-21 1979-12-25 Khrupin Vasilij A Индукционна плавильна печь
SU853829A1 (ru) * 1980-04-04 1981-08-07 Предприятие П/Я Г-4696 Индукционна канальна печь

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU423999A1 (ru) * 1973-01-09 1974-04-15 Л. П. Пужайло, В. П. Полищук , В. К. Погорский Институт проблем лить Индукционная канальная печь
SU460422A1 (ru) * 1973-03-13 1975-02-15 Всесоюзный Научно-Исследовательский И Проектный Институт Вторичных Цветных Металлов Вниипвторцветмет Индукционна канальна печь
SU565188A1 (ru) * 1975-11-18 1977-07-15 Всесоюзный Научно-Исследовательский И Проектный Институт Вторичных Цветных Металлов Индукционна канальна печь
SU705231A1 (ru) * 1978-07-21 1979-12-25 Khrupin Vasilij A Индукционна плавильна печь
SU853829A1 (ru) * 1980-04-04 1981-08-07 Предприятие П/Я Г-4696 Индукционна канальна печь

Non-Patent Citations (5)

* Cited by examiner, † Cited by third party
Title
DERWENT ABSTRACT, Accession No. 15547W/09, Class M22, Q77, R59; & SU,A,423 999 (LASTING PROBLEMS INST), 23 September 1974. *
DERWENT ABSTRACT, Accession No. 40006A/22, CLass M28, Q77; & SU,A,565 188 (SEC NON-FERR METALS), 31 August 1977. *
DERWENT ABSTRACT, Accession No. 45569E/22, Class J09, M24, X25, Q77; & SU,A,853 829 (ALESHIN AS), 7 August 1981. *
DERWENT ABSTRACT, Accession No. 58169C/33, Class M28, X25, Q77; & SU,A,705 231 (KHRUPIN V A), 5 January 1980. *
DERWENT ABSTRACT, Accession No. 68505W/41, Class M24, Q77; & SU,A,460 422 (NON FERR METAL SCRA), 27 March 1975. *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8158055B2 (en) * 2004-12-22 2012-04-17 Kenzo Takahashi Melting furnace with agitator

Also Published As

Publication number Publication date
NZ266736A (en) 1996-11-26

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