EP0273975B1 - Four a induction de plasma - Google Patents

Four a induction de plasma Download PDF

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Publication number
EP0273975B1
EP0273975B1 EP86906036A EP86906036A EP0273975B1 EP 0273975 B1 EP0273975 B1 EP 0273975B1 EP 86906036 A EP86906036 A EP 86906036A EP 86906036 A EP86906036 A EP 86906036A EP 0273975 B1 EP0273975 B1 EP 0273975B1
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EP
European Patent Office
Prior art keywords
melt
crucible
plasmatron
sections
arc
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
Application number
EP86906036A
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German (de)
English (en)
Other versions
EP0273975A1 (fr
EP0273975A4 (fr
Inventor
Nikolai Ivanovich Fomin
Mikhail Petrovich Chaikin
Vladimir Sergeevich Malinovsky
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
VSESOJUZNY NAUCHNO-ISSLEDOVATELSKY PROEKTNO-KONSTRUKTORSKY I TEKHNOLOGICHESKY INST ELEKTROTERMICHESKOGO OBORUDOVANIA VNIIETO
Original Assignee
VSESOJUZNY NAUCHNO-ISSLEDOVATELSKY PROEKTNO-KONSTRUKTORSKY I TEKHNOLOGICHESKY INST ELEKTROTERMICHESKOGO OBORUDOVANIA VNIIETO
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 VSESOJUZNY NAUCHNO-ISSLEDOVATELSKY PROEKTNO-KONSTRUKTORSKY I TEKHNOLOGICHESKY INST ELEKTROTERMICHESKOGO OBORUDOVANIA VNIIETO filed Critical VSESOJUZNY NAUCHNO-ISSLEDOVATELSKY PROEKTNO-KONSTRUKTORSKY I TEKHNOLOGICHESKY INST ELEKTROTERMICHESKOGO OBORUDOVANIA VNIIETO
Priority to AT86906036T priority Critical patent/ATE57052T1/de
Publication of EP0273975A1 publication Critical patent/EP0273975A1/fr
Publication of EP0273975A4 publication Critical patent/EP0273975A4/fr
Application granted granted Critical
Publication of EP0273975B1 publication Critical patent/EP0273975B1/fr
Anticipated expiration legal-status Critical
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    • 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
    • H05B11/00—Heating by combined application of processes covered by two or more of groups H05B3/00 - H05B7/00
    • 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
    • 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
    • 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
    • F27B14/08—Details peculiar to crucible or pot furnaces
    • F27B14/14—Arrangements of heating devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D99/00—Subject matter not provided for in other groups of this subclass
    • F27D99/0001—Heating elements or systems
    • F27D99/0006—Electric heating elements or system
    • 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
    • H05B6/22—Furnaces without an endless core
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D99/00—Subject matter not provided for in other groups of this subclass
    • F27D99/0001—Heating elements or systems
    • F27D99/0006—Electric heating elements or system
    • F27D2099/0031—Plasma-torch heating

Definitions

  • the invention relates to a field of electrical engineering and relates in particular to electrical heating devices, specifically a plasma induction furnace.
  • the performance of different melting furnaces and the quality of the metal or alloy to be produced depend significantly on the type and intensity of movement of the melt in the crucible.
  • Induction melting furnaces are largely known which contain an inductor with a crucible arranged therein, which is lined with a refractory lining. They ensure contactless energy supply to the insert in the crucible, i.e. Batch, melt or batch-melt mixture.
  • the insert is mixed using the electromagnetic field of the inductor.
  • induction melting furnaces operated at normal frequency (50 to 60 Hz)
  • the speed of the melt is high, which ensures effective melting of the solid insert and homogenization of the melt.
  • there is increased wear on the crucible chuck and increased oxidation of the melt which leads to contamination of the metal with inclusions of various types.
  • a metal ejection from the crucible is possible.
  • Such induction furnaces therefore have a limit in terms of the specific power to be supplied within 300 to 400 kW / t.
  • the natural circulation in induction melting furnaces in which the inductor is connected to a single-phase supply source, takes place in two circuits, which lie in the vertical plane, in the upper and lower part of the crucible, in each of which the melt of the insert circulates separately, by mixing is going on weakly.
  • Such a type of circulation in induction furnaces leads to the formation of a convex meniscus on the surface of the melt, which increases the amount of slag that rolls down to the walls of the crucible, destroys its feed and contaminates the melt.
  • devices are used in which the circulation of the insert is generated in a circuit with the aid of a running field which ensures that the insert is mixed over the entire crucible height while reducing the meniscus (AE Slukhotsky , VS Nemkov, NA Pavlov, AV Bamune, Ustanovka induktsionnogo nagreva. Energoizdat, Leningradskoe otdelenie / induction heating system, publisher Energoizdat, Leningrad department /, 1981, pp. 246 to 247).
  • the insert can be heated and mixed both simultaneously and alternately.
  • inductors are used: a single-phase inductor for heating and a three-phase inductor for mixing, which are equipped with electrostatic filters to protect the feed source against penetration of one frequency into the other.
  • the oven has a divided inductor, which is alternately connected to different food sources.
  • the supply circuit of the induction melting furnace is considerably complicated, only two types of circulation are generated: in two circuits - when connecting the inductor to a single-phase supply source, in a circuit - when connecting it to a three-phase supply source.
  • Plasma induction furnaces which contain an inductor with a crucible arranged therein and an arc plasmatron, the circuit of which is closed via the melt.
  • these furnaces make it possible, for example, to double the productivity of the process of melting metals and alloys, due to the combination of the local and the spatial heating of the insert.
  • the quality of the metals and alloys to be produced is improved due to the in-depth refining of the melt to remove non-metallic inclusions and harmful substances.
  • the melt can be treated with both inert and active plasma-forming gases. How the mixing process of use in plasma induction furnaces is carried out is therefore of particular importance for the performance increase of the furnaces and the quality improvement of the metals and alloys to be obtained by melting.
  • the inner surface of the crucible is made of an electrical insulating material, and is provided with a magnesite lining and provides the electrical insulation of the plasmatron circuit from the inductor circuit.
  • a bottom electrode for closing the plasmatron circuit is arranged in the bottom of the crucible.
  • the inductor is connected to a single-phase power source with an output frequency of 150 Hz.
  • a three-phase system for electromagnetic mixing is provided, which contains three inductors, each of which is connected to a phase of a three-phase supply source with a frequency of 60 Hz.
  • the invention has for its object to provide a plasma induction furnace with such a design of the crucible and such an electrical coupling of the crucible with a plasmatron, by which a predetermined type of circulation of the melt in the crucible depending on the technological process in the melting process and thus the performance of the plasma induction furnace can be increased.
  • the object is achieved in that, in the case of a plasma induction furnace which contains an inductor with a crucible arranged therein, the side wall of which is cylindrical, and an arc plasmatron, the circuit of which is closed via the melt located in the crucible, according to the invention the side wall of the crucible is perpendicular arranged sections is formed, which consist of a current-conducting material and are electrically insulated from one another, at least one of which is connected in series in the plasmatron circuit in such a way that the current direction in the plasmatron arc coincides with the current direction in the crucible section or is opposite thereto.
  • Such a constructive design of the crucible of the plasma induction furnace allows a predetermined type of circulation of the melt, depending on the technological process stage when metals and alloys are melted, due to the electromagnetic interaction of fields generated by the inductor current and the current in the sections of the crucible with those flowing in the melt Streams are created.
  • the constructive design of the crucible according to the invention thus makes it possible to produce any type of circulation of the melt which is required, depending on the technological process step when melting metals or alloys, in the plasma induction furnace without the structure of the furnace having to be considerably complicated.
  • the plasma induction furnace contains an inductor 1 (FIG. 1) with a crucible 2 arranged therein. Similar to inductors in known plasma induction furnaces, the inductor is designed in the form of a tube with a round or special cross section, which lies around the crucible 2 according to a helical line.
  • the crucible 2 has the shape of a cylinder, its side wall being formed by vertically arranged sections 3 (FIGS. 1, 2) which consist of a current-conducting material, in particular of metal ceramic. In the embodiment of the plasma induction furnace shown in FIGS. 1, 2, five sections 3 are shown. Depending on the outer dimensions of the crucible 2, the number and the material of these sections 3 can be different. It is expedient to select the number of sections within 5 to 35, as a result of which optimal energy characteristics of the plasma induction furnace, e.g. the efficiency, the performance can be guaranteed.
  • the sections 3 of the crucible 2 can also be made from other current-conducting materials such as graphite, metal.
  • the sections 3 are electrically insulated from one another by electro-insulating layers 6 consisting of magnesite, which lie between the sections 3 and have been applied to the surfaces of the sections 3 facing the inside of the crucible 2, to the bottom 5, to the end faces of the sections 3.
  • the thickness of each layer 6 depends on the material and application method of the electrical insulation.
  • the electrical insulation from Al 2 0 3 can be applied, for example, by the vapor deposition process.
  • the plasma induction furnace also contains a direct current arc plasmatron 7 (Fig. 1).
  • the plasmatron 7 is mounted in the lid 8 of the crucible 2 and causes the batch 9 to be heated and melted down by means of a plasma arc 10.
  • the inner surface of the lid 8 is provided with a lining layer 11.
  • a segment-shaped part 12 (FIG. 2) of the crucible 2 (FIG. 1) lying in the vicinity of one of the sections 3 of the crucible 2 is insulation-free.
  • This part 12 (FIG. 2) serves to supply current to the melt 4 (FIG. 1), via which the circuit of the plasma cartridge 7 is closed.
  • the section 3 of the crucible 2, to which the part 12 (FIG. 2) of the base 5 (FIG. 1) adjoins, is connected to the circuit of the plasmatron 7.
  • the current direction in the arc 10 of the plasmatron 7 coincides with the current direction in section 3 (the current directions are indicated by arrows in FIG. 1).
  • Power supply terminals 13, 14 of the plasma cartridge 7 are connected to a supply source, in the embodiment in question - to a direct current source.
  • An AC power source can be used as the power source. If a DC plasmatron is used, it is connected to the AC power source via a rectifier. Only one AC power source is used for the AC plasmatron. When using an AC power source, a power source can be used for the inductor.
  • one of the terminals - 13 - is connected to the bottom 5 of the crucible 2 and the other terminal 14 to a power supply 15 arranged in the upper part of section 3, while another power supply 16, which is located in the lower part of this section 3, with the plasmatron 7 is connected.
  • the section 3 is connected to the circuit of the plasma cartridge 7 in such a way that the current directions in the section 3 and in the arc 10 of the plasma cartridge 7 are in opposite directions.
  • the power supply 15 is connected to the terminal 13 and the Plasmatron 7 to the terminal 14.
  • the bottom 5 of the crucible 2 is completely covered with the electrical insulation layer 6, while part 17 of the inner surface of the section 3, which is connected to the circuit of the plasmatron 7, is insulation-free and serves to supply current to the melt 4.
  • FIG. 4 shows a plasma induction furnace, the crucible 18, which is enclosed by an inductor 19 designed in a known manner, contains twelve sections 20 (FIG. 5), which, as in known induction furnaces, are designed with a cooled composite crucible.
  • Each section 20 consists of a metal, for example Copper, and has a circulation channel 21 for a coolant, as which water, gas, cryogenic liquid can be used.
  • the sections 20 are electrically isolated from one another with the aid of electrical insulating layers 22, 23, for example made of Al 2 O 3 , which have been applied by vapor deposition to the surfaces facing the inside of the crucible 18 and to one another.
  • An electrical insulation layer for example made of magnesite or alundum, can additionally be applied to the surfaces facing the interior of the crucible 18.
  • the lid 24 of the crucible 18 was made similar to the lid 8.
  • FIG. 6 shows an embodiment of the plasma induction furnace similar to the furnace shown in FIGS. 4, 5, in which all sections 20 of the crucible 18 are connected to the circuit of the plasma cartridge 7 in such a way that the current directions in the arc 10 and in the sections 20 coincide.
  • the current leads 31 arranged in the upper part of the sections 20 are connected to the terminal 14 and the current leads 32 located in the lower part of the sections 20 are connected to the Plasmatron 7.
  • the bottom 27 is completely insulation-free and connected to the terminal 13.
  • the force F of the electromagnetic field on the melt 4 is indicated in FIG. 7, 8a, b, 10a, b, 12a, b with arrows.
  • the type of circulation of the melt 4 is given in the plasma induction furnaces shown in FIGS. 1, 2, 3, 4, 5, 6 with closed lines "1" in FIGS. 7, 9, 11, 13.
  • the plasma induction furnace is operated as follows.
  • the cover 8 is closed and the plasmatron 7 is brought into the ignition position of the arc 10. Then a voltage is supplied to the inductor 1 and the plasmatron 7 and the arc 10 is ignited.
  • the insert Under the action of the arc 10 of the plasmatron 7 and the electromagnetic field of the inductor 1, the insert begins to melt down.
  • the arc 10 melts the insert layer quickly through its thickness, burns between the surface of the melt 4 and the plasmatron 7 and gives off its heat intensively to the surrounding insert.
  • the length of the arc 10 becomes shorter, the conditions for the heat emission from the arc 10 to the melt 4 deteriorate.
  • the conditions for supplying energy from the inductor 1 to the melt 4 are improved.
  • the circulation of the melt 4 takes place in natural two circuits, which has a favorable effect on the heat exchange. Thereafter, to remove harmful accompanying substances on the surface of the melt 4 in the crucible 2 through special holes (not shown in the drawing) in the Dickel 8, a slag is added in portions to the overheated melt 4 in a predetermined order.
  • the circulation of the melt 4 is brought about in such a way as is shown by closed lines "1" in FIG. 7.
  • the voltage at the inductor 1 is continuously reduced or the voltage at the terminals 13, 14 is increased, which in the first case leads to a current draw in the inductor 1 and in the second case to a current increase in the circuit of the plasmatron 7.
  • the force F (FIG. 7) on the melt 4 (FIG. 1) is weakened by the section 3 connected to the circuit of the plasmatron 7, which leads to the circulation of the melt 4 in the horizontal plane in the entire volume of the crucible 2.
  • the surface of the melt 4 has no meniscus, and a continuous supply of the slag under the arc 10 of the plasmatron 7 is ensured, its melting and heating accelerating, which leads to an increase in the furnace output.
  • the homogeneity of the melt 4 in the total volume of the crucible 2 is also improved.
  • This constructive design of the crucible 2 makes it possible to rapidly change the type of movement of the melt from the circulation in the vertical plane to the circulation in the horizontal plane by continuously changing the current in the inductor 1 or in the arc 10 of the plasma cartridge 7.
  • the predetermined type of circulation is generated, in which the accumulation of the used slag at the tapping point is ensured for its removal.
  • Refractory metals and alloys e.g. Tungsten are usually melted in plasma induction furnaces with the cooling crucible 18 (FIGS. 4, 5, 6).
  • a coolant is introduced into the channels 21 of the sections 20 and the channel 28 of the base 27, which coolant circulates during the entire melting process.
  • the arc 10 is ignited.
  • a section flows through the sections 20 connected to the circuit of the plasma cartridge 7, the direction of which is opposite to the current direction in the arc 10 of the plasma cartridge 7.
  • the melt 4 is mixed thoroughly, and the surface of the melt 4 acquires a convex shape.
  • the current of the arc 10 flowing through the melt 4 will strive to flow along the surface of the melt 4 in the vicinity of the electrically insulated sections 20 connected to the circuit of the plasma cartridge 7.
  • a component of the force of the electromagnetic field of the sections 20 on the current flowing through the arc 10 and the melt 4 thus arises in the upper part of the melt 4 and is directed downward to the bottom 27 of the crucible 18.
  • the size of this component decreases.
  • the component directed from the periphery toward the center of the melt 4 of the similar interaction of the electromagnetic field generated by the current in the sections 20 with the current flowing through the melt 4 increases, thereby pushing the melt 4 away from the sections 20 of the crucible 18 is increased.
  • the specific power to be supplied by the inductor 19 can be increased in that, as a result of the connection of the sections 20 of the crucible 18, their current direction with the current direction in the arc 10 of the plasma cartridge 7 coincides, the resulting force F (FIG. 12a, b) of the electromagnetic field on the circuit of the plasma cartridge 7 can be weakened by the inductor 19 on the melt 4 (FIG. 6).
  • the circulation type "1" (Fig. 13) is similar to the circulation taking place under the effect of the electromagnetic field from the inductor 19, only the speed of movement of the melt 4 changes Period by the inductor 19 of the melt 4 to be supplied leads to an increase in the furnace output.
  • the present plasma induction furnace can preferably be used in the metallurgical industry, in technological processes when melting different metals and alloys, e.g. on the tungsten, molybdenum basis, especially in processes associated with the use of highly active hot slags.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Furnace Details (AREA)
  • Discharge Heating (AREA)
  • Crucibles And Fluidized-Bed Furnaces (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • Electric Stoves And Ranges (AREA)
  • General Induction Heating (AREA)

Claims (1)

  1. Four à induction et à plasma comportant un inducteur (1, 19) abritant un creuset (2, 18) à paroi latérale cylindrique, et un chalumeau à arc éléctri- que à gaz ionisé (7) dont le circuit électrique est fermé par le métal fondu (4) dans le creuset (2, 18), caractérisé en ce, que la paroi latérale du creuset (2, 18) est formée de sections verticale (3, 20), faites en un matériau électroconducteur et isolées entre elles, au moins une desquellas est inséréa en série dans le circuit électrique dudit chalumeau à arc électrique à gaz ionisé (7) de telle façon que la direction du courant d'arc (10) du chalumeau à arc électrique à gaz ionisé (7) coïncide ou est opposée à la direction du courant dans une section (3, 20) du creuset (2, 18).
EP86906036A 1986-07-04 1986-07-04 Four a induction de plasma Expired - Lifetime EP0273975B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT86906036T ATE57052T1 (de) 1986-07-04 1986-07-04 Plasma-induktionsofen.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/SU1986/000070 WO1988000426A1 (fr) 1986-07-04 1986-07-04 Four a induction de plasma

Publications (3)

Publication Number Publication Date
EP0273975A1 EP0273975A1 (fr) 1988-07-13
EP0273975A4 EP0273975A4 (fr) 1988-09-28
EP0273975B1 true EP0273975B1 (fr) 1990-09-26

Family

ID=21617017

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86906036A Expired - Lifetime EP0273975B1 (fr) 1986-07-04 1986-07-04 Four a induction de plasma

Country Status (7)

Country Link
EP (1) EP0273975B1 (fr)
JP (1) JPH01500152A (fr)
AT (1) ATE57052T1 (fr)
DE (1) DE3674594D1 (fr)
HU (2) HU200405B (fr)
IN (1) IN164477B (fr)
WO (1) WO1988000426A1 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4207694A1 (de) * 1992-03-11 1993-09-16 Leybold Durferrit Gmbh Vorrichtung fuer die herstellung von metallen und metall-legierungen hoher reinheit
WO2014047220A1 (fr) 2012-09-18 2014-03-27 Retech Systems Llc Système et procédé de fusion de matières premières
CN106756073B (zh) * 2016-12-28 2020-10-02 哈尔滨工业大学 一种应用于高熔点高活性金属材料的多功能熔铸设备
JP7428632B2 (ja) 2020-12-14 2024-02-06 信越化学工業株式会社 多孔質ガラス母材の製造方法及び製造装置

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3793468A (en) * 1972-09-22 1974-02-19 Westinghouse Electric Corp Furnace apparatus utilizing a resultant magnetic field or fields produced by mutual interaction of at least two independently generated magnetic fields and methods of operating an electric arc furnace
SE400013B (sv) * 1974-07-23 1978-03-06 Asea Ab Anordning vid likstromsmatade ljusbagsugnar
SE408958B (sv) * 1976-07-05 1979-07-16 Asea Ab Forfaringssett for smeltning av metaller eller metallegeringar
FR2497050A1 (fr) * 1980-12-23 1982-06-25 Saphymo Stel Dispositif de fusion par induction directe en cage froide avec confinement electromagnetique de la charge fondue
SE447846B (sv) * 1982-09-09 1986-12-15 Asea Ab Skenkugn med likstromsvermning
US4495625A (en) * 1983-07-05 1985-01-22 Westinghouse Electric Corp. Magnetic field stabilized transferred arc furnace
SE449132B (sv) * 1984-01-25 1987-04-06 Asea Ab Likstromsljusbagsugn eller skenk for vermning
JPS63106211A (ja) * 1986-05-19 1988-05-11 Anritsu Corp カセツト管理方法

Also Published As

Publication number Publication date
ATE57052T1 (de) 1990-10-15
IN164477B (fr) 1989-03-25
JPH0361318B2 (fr) 1991-09-19
HUT46496A (en) 1988-10-28
EP0273975A1 (fr) 1988-07-13
EP0273975A4 (fr) 1988-09-28
JPH01500152A (ja) 1989-01-19
HU200405B (en) 1990-05-28
DE3674594D1 (de) 1990-10-31
WO1988000426A1 (fr) 1988-01-14

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