EP0178477B1 - Method for producing seamless steel tubes with a great diameter - Google Patents

Method for producing seamless steel tubes with a great diameter Download PDF

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Publication number
EP0178477B1
EP0178477B1 EP85111773A EP85111773A EP0178477B1 EP 0178477 B1 EP0178477 B1 EP 0178477B1 EP 85111773 A EP85111773 A EP 85111773A EP 85111773 A EP85111773 A EP 85111773A EP 0178477 B1 EP0178477 B1 EP 0178477B1
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EP
European Patent Office
Prior art keywords
pipes
seamless steel
diameter
rolling
hollow body
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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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EP85111773A
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German (de)
French (fr)
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EP0178477A1 (en
Inventor
Ulrich Dr.-Ing. E.H. Dipl.-Ing Petersen
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
    • B21C37/06—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of tubes or metal hoses; Combined procedures for making tubes, e.g. for making multi-wall tubes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B23/00—Tube-rolling not restricted to methods provided for in only one of groups B21B17/00, B21B19/00, B21B21/00, e.g. combined processes planetary tube rolling, auxiliary arrangements, e.g. lubricating, special tube blanks, continuous casting combined with tube rolling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B19/00—Tube-rolling by rollers arranged outside the work and having their axes not perpendicular to the axis of the work
    • B21B19/02—Tube-rolling by rollers arranged outside the work and having their axes not perpendicular to the axis of the work the axes of the rollers being arranged essentially diagonally to the axis of the work, e.g. "cross" tube-rolling ; Diescher mills, Stiefel disc piercers or Stiefel rotary piercers
    • B21B19/06—Rolling hollow basic material, e.g. Assel mills
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B19/00—Tube-rolling by rollers arranged outside the work and having their axes not perpendicular to the axis of the work
    • B21B19/02—Tube-rolling by rollers arranged outside the work and having their axes not perpendicular to the axis of the work the axes of the rollers being arranged essentially diagonally to the axis of the work, e.g. "cross" tube-rolling ; Diescher mills, Stiefel disc piercers or Stiefel rotary piercers
    • B21B19/06—Rolling hollow basic material, e.g. Assel mills
    • B21B19/08—Enlarging tube diameter
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/4998—Combined manufacture including applying or shaping of fluent material
    • Y10T29/49988—Metal casting
    • Y10T29/49991—Combined with rolling

Definitions

  • the invention relates to a method for producing pipes of large diameter, starting from hollow continuous casting blocks, which are rolled out by cross rolling over a dome and then expanded in an expanding mill.
  • DD-A-68 215 From DD-A-68 215 a process for the production of seamless pipes is known, starting from hollow blocks produced by continuous casting. These can then be expanded, for example, by cross-rolling over a pressure-loaded dome and then brought to the final dimension in a plug rolling mill, or after cross-rolling they are subjected to a vocational process. The combination of inclined roller / stretch reduction is also planned.
  • the invention based on this prior art, the task is based on making the production of pouring tubes more economical.
  • This object is achieved according to the invention in that the hollow blocks in the cross-rolling mill are rolled out to the final length (length of the finished tube) with a dome that is subjected to tension and that the desired final dimension (diameter, wall thickness) is set by the expansion without stretching in the axial direction.
  • Another advantage is that the dimensions, in particular the tube length, can be kept variable.
  • Fig. 1 shows the process for producing a welded large pipe.
  • the first production unit is the steel mill with a slab caster. Both are shown symbolically in box 1.
  • the starting product is the slab 2, which is rectangular in cross section.
  • a sheet metal rolling mill symbolically represented by box 3.
  • the starting material for tube production the heavy plate
  • U-press As the starting material for the final pipe production in a large pipe mill, this first comes into a so-called U-press, in which a U-shaped body is first produced in the longitudinal direction of the sheet. This U-body is completely bent in the so-called 0-press into a tube with a round cross-section and then welded in the longitudinal direction at the joints. After subsequent heat treatment and adjustment, the manufacturing process for the finished pipe is finished. This manufacturing process is symbolized by box 5. The end result is the welded large pipe 6.
  • the method for producing a seamless large pipe is shown schematically in the same way in FIG. 2.
  • the first production stage symbolically designated by box 7, there is a steelworks with a hollow continuous casting system known per se.
  • the result of this manufacturing stage is a round, thick-walled, hollow steel body, the so-called hollow block, as shown in cross section at 8.
  • this hollow block can be of any length.
  • this hollow block is used in the next process stage 9 in a cross-rolling mill, the main task of which is to produce the intended final length of the finished tube.
  • This cross-rolling mill is primarily represented by a known cross-rolling mill, the dome bar of which is subjected to tension.
  • the hollow block stretched in this way is fed to one or more expansion rolling mills connected in series with mandrel bars which are subjected to tension and which only have the task of determining the diameter of the hollow block to bring the desired dimension with the desired wall thickness and so to produce an extension only in the tangential direction while roughly maintaining the weight per meter or the axial dimension.
  • the exact final dimension is generated in a sizing mill or expander.

Abstract

A method of forming seamless metal tubing and pipes of large diameter in excess of 500 mm diameter. A thickwalled hollow body is made by continuous casting. Rolling the continuously cast hollow body over a mandrel in an oblique rolling mill to the desired weight per unit length. Radially expanding the rolled hollow body while maintaining its weight per unit length.

Description

Die Erfindung betrifft ein Verfahren zum Herstellen von Rohren großen Durchmessers, wobei von Hohlstranggußblöcken ausgegangen wird, die durch Schrägwalzen über einen Dom ausgewalzt werden und anschließend in einem Aufweitewalzwerk aufgeweitet werden.The invention relates to a method for producing pipes of large diameter, starting from hollow continuous casting blocks, which are rolled out by cross rolling over a dome and then expanded in an expanding mill.

Stahlrohre großen Durchmessers, insbesondere für Pipelines, werden nahezu ausschließlich aus geschweißten Rohren hergestellt. Der Grund liegt im wesentlichen in der wirtschaftlichen Herstellungsweise geschweißter Stahlrohre gegenüber nahtlosen Stahlrohren großer Abmessungen. Gleichwohl wäre es wünschenswert, für die meisten der Anwendungsgebiete von Stahlrohren großen Durchmessers nahtlose Rohre zu verwenden, um das Unsicherheitsrisiko einer Schweißnaht sowohl bei Verlegung als auch bei dem Betrieb zu vermeiden. Bekanntlich sind Schweißnähte immer ein Festigkeitsproblem, wodurch auch bei der Herstellung solcher Rohre ein hoher Aufwand sowohl für die Kontrolle von Schweißnähten als auch für das Nachvergüten erforderlich ist.Steel pipes of large diameter, especially for pipelines, are almost exclusively made from welded pipes. The reason lies essentially in the economical production method of welded steel pipes compared to seamless steel pipes of large dimensions. However, it would be desirable to use seamless tubes for most of the applications of large diameter steel tubes to avoid the risk of uncertainty of a weld both during installation and operation. As is known, weld seams are always a problem of strength, which means that even in the manufacture of such pipes, a high outlay is required both for the inspection of weld seams and for the subsequent tempering.

Es sind zwar Verfahren bekannt, bei denen Rohre unter Auswalzen von großen Hohlblöcken hergestellt werden. Die technischen und wirtschaftlichen Schwierigkeiten liegen dabei einerseits in der Erzeugung der großen Blöcke, andererseits in der Verwendung spezieller, aufwendiger Walzwerke.Methods are known in which pipes are produced by rolling out large hollow blocks. The technical and economic difficulties lie on the one hand in the production of the large blocks, on the other hand in the use of special, complex rolling mills.

Aus der DD-A-68 215 ist ein Verfahren zur Herstellung nahtloser Rohre bekannt, wobei von durch Stranggießen erzeugten Hohlblöcken ausgegangen wird. Diese können dann bspw. durch Schrägwalzen über einen auf Druck beanspruchten Dom aufgeweitet und anschließend in einem Stopfenwalzwerk auf die endgültige Abmessung gebracht werden oder nach dem Schrägwalzen werden sie einem Pilgerverfahren unterworfen. Vorgesehen ist auch die Kombination SchrägwalzenJStreckreduzieren.From DD-A-68 215 a process for the production of seamless pipes is known, starting from hollow blocks produced by continuous casting. These can then be expanded, for example, by cross-rolling over a pressure-loaded dome and then brought to the final dimension in a plug rolling mill, or after cross-rolling they are subjected to a pilgrimage process. The combination of inclined roller / stretch reduction is also planned.

Da Aufweiten von Hohlblöcken durch Walzen ist auch der DE-C 628 393 zu entnehmen.Since expanding hollow blocks by rolling can also be found in DE-C 628 393.

Der Erfindung. liegt ausgehend von diesem Stand der Technik die Aufgabe zugrunde, die Herstellung von Gießrohren wirtschaftlicher zu gestalten.The invention. based on this prior art, the task is based on making the production of pouring tubes more economical.

Gelöst wird diese Aufgabe erfindungsgemäß dadurch, daß die Hohlblöcke im Schrägwalzwerk auf die endgültige Länge (Länge des Fertigrohres) mit einem auf Zug beanspruchten Dom ausgewalzt werden und daß durch das Aufweiten ohne Streckung in axialer Richtung die gewünschte Endabmessung (Durchmesser, Wandstärke) eingestellt wird.This object is achieved according to the invention in that the hollow blocks in the cross-rolling mill are rolled out to the final length (length of the finished tube) with a dome that is subjected to tension and that the desired final dimension (diameter, wall thickness) is set by the expansion without stretching in the axial direction.

Durch die Kombination dieser Verfahrensschritte ist es möglich, in wirtschaftlicher Weise, also mit vergleichsweise geringem Aufwand an Anlagen und damit Investitionen, nahtlose Stahlrohre großen Durchmessers herzustellen und damit die bekannten Risiken der geschweißten Großrohre infolge der Unsicherheit der Schweißnaht zu vermeiden. Dies ist von besonderer Bedeutung für Rohre, die aus schwer schweißbaren Stählen herzustellen sind oder unter einem sehr hohen Innendruck stehen. Ebenson ist dies von Bedeutung für Rohre, die in schwierigen klimatischen Verhältnissen verwendet werden sollen oder deren Handhabung keine besondere Sorgfalt zuläßtThe combination of these process steps makes it possible to produce seamless steel pipes of large diameter in an economical manner, that is to say with relatively little outlay on plants and thus investments, and thus to avoid the known risks of the welded large pipes as a result of the uncertainty of the weld seam. This is particularly important for pipes that are made from difficult to weld steels or that are under a very high internal pressure. This is also important for pipes that are to be used in difficult climatic conditions or whose handling does not require special care

Ein weiterer Vorteil ist, daß die Abmessungen, insbesondere die Rohrlänge betreffend, variabel gehalten werden können.Another advantage is that the dimensions, in particular the tube length, can be kept variable.

In der Zeichnung ist ein Ausführungsbeispiel des Verfahrensablaufes nach der Erfindung im Vergleich zur konventionellen geschweißten Herstellung von Großrohren schematisch dargestellt.In the drawing, an embodiment of the process sequence according to the invention is shown schematically in comparison to the conventional welded manufacture of large pipes.

Fig. 1 zeigt das Verfahren zur Herstellung eines geschweißten Großrohres. Die erste Produktionseinheit ist das Stahlwerk mit einer Brammenstranggußanlage. Beide sind symbolisch im Kästchen 1 dargestellt. Das Ausgangsprodukt ist die im Querschnitt rechteckige Bramme 2. Diese wird im nächsten Verarbeitungsgang nach einer Zwischenerwärmung einem Blechwalzwerk zugeführt, symbolisch dargestellt durch Kästchen 3.Fig. 1 shows the process for producing a welded large pipe. The first production unit is the steel mill with a slab caster. Both are shown symbolically in box 1. The starting product is the slab 2, which is rectangular in cross section. In the next processing step, after intermediate heating, it is fed to a sheet metal rolling mill, symbolically represented by box 3.

Nach der Adjustage ist mit 4 das Ausgangsmaterial für die Rohrherstellung, das Grobblech, dargestellt. Dieses kommt als Ausgangsmaterial für die endgültige Rohrherstellung in einem Großrohrwerk zunächst in eine sog. U-Presse, bei dem in Längsrichtung des Bleches zunächst ein U-förmiger Körper hergestellt wird. Dieser U-Körper wird in der sog. 0-Presse vollends zu einem im Querschnitt runden Rohr gebogen und daran anschließend an den Stoßstellen in Längsrichtung verschweißt. Nach nachfolgender Wärmebehandlung und Adjustieren ist der Herstellungsvorgang zum fertigen Rohr beendet Dieser Fertigungsgang ist durch das Kästchen 5 symbolisiert Das Endergebnis ist das gechweißte Großrohr 6.After the finishing line, the starting material for tube production, the heavy plate, is shown at 4. As the starting material for the final pipe production in a large pipe mill, this first comes into a so-called U-press, in which a U-shaped body is first produced in the longitudinal direction of the sheet. This U-body is completely bent in the so-called 0-press into a tube with a round cross-section and then welded in the longitudinal direction at the joints. After subsequent heat treatment and adjustment, the manufacturing process for the finished pipe is finished. This manufacturing process is symbolized by box 5. The end result is the welded large pipe 6.

Das Verfahren zur Herstellung eines nahtlosen Großrohres ist in derselben Weise schematisch in Fig. 2 dargestellt In der ersten Fertigungsstufe, symbolisch mit dem Kästchen 7 bezeichnet, befindet sich ein Stahlwerk mit einer an sich bekannten Hohlstranggußanlage. Das Ergebnis dieser Fertigungsstufe ist ein runder, dickwandiger, hohler Stahlkörper, der sog. Hohlblock, wie bei 8 im Querschnitt dargestellt. Dieser Hohlblock kann im Prinzip beliebig lang sein.The method for producing a seamless large pipe is shown schematically in the same way in FIG. 2. In the first production stage, symbolically designated by box 7, there is a steelworks with a hollow continuous casting system known per se. The result of this manufacturing stage is a round, thick-walled, hollow steel body, the so-called hollow block, as shown in cross section at 8. In principle, this hollow block can be of any length.

Nach einer evtl. notwendigen Nacherwärmung wird dieser Hohlblock in der nächsten Verfahrensstufe 9 in ein Schrägwalzwerk eingesetzt, dessen Hauptaufgabe darin besteht, die vorgesehene endgültige Länge des fertigen Rohres zu erzeugen. Dieses Schrägwalzwerk wird vornehmlich durch ein bekanntes Schrägwalzwerk, dessen Domstange auf Zug beansprucht wird, dargestellt.After a possibly necessary reheating, this hollow block is used in the next process stage 9 in a cross-rolling mill, the main task of which is to produce the intended final length of the finished tube. This cross-rolling mill is primarily represented by a known cross-rolling mill, the dome bar of which is subjected to tension.

Danach wird der so gestreckte Hohlblock einem oder mehreren hintereinandergeschalteten Aufweitewalzwerken mit auf Zug beanspruchten Dornstangen zugeführt, die lediglich die Aufgabe haben, den Durchmesser des Hohlblockes auf das gewünschte Maß bei der gewünschten Wandstärke zu bringen und so eine Streckung nur noch in tangentialer Richtung zu erzeugen unter ungefährer Beibehaltung des Metergewichts bzw. der axialen Abmessung. Die genaue Endabmessung wird in einem Maßwalzwerk oder Expander erzeugt. Ist diese erreicht, so besitzt man nach der Adjustage ein Nahtlosrohr 10, dessen Abmessungen abhängig von den angewendeten Verformungsaggregaten und abhängig vom Hohlblock, der aus der Hohlstrangyußanlage kommt, durchaus vergleichbar sind mit denjenigen der geschweißten Großrohre. Ferner ist es denkbar, auch ohne große Schwierigkeiten Abmessungen zu erreichen, die sowohl in der Länge des Großrohres als auch in dessen Durchmesser und Wandstärke den geschweißten Großrohren konventioneller Herstellungsart überlegen sind. Schließlich ist es auch möglich, auf diese Art der Großrohrherstellung sicherer und wirtschaftlicher wegen des fehlenden Schweißrisikos hochwertigeren Stahl zu Großrohren zu verarbeiten. Die Vorteile dieses Herstellungsverfahrens sind insbesondere ein geringerer Aufwand an Anlagen und damit Investitionen, ebenso wie ein geringerer Aufwand an Energie gegenüber geschweißten . Großrohren. Damit ist es auf wirtschaftlich vertretbare Weise möglich, Großrohre zu erzeugen, die nicht das Risiko einer Schweißnaht aufweisen, wirtschaftlicher herzustellen sind und in ihren Abmessungen, insbesondere die Rohrlänge betreffend, variabel gehalten werden können, verbunden mit dem Vorteil der Verarbeitungsmöglichkeit von hochwertigen Stählen.Thereafter, the hollow block stretched in this way is fed to one or more expansion rolling mills connected in series with mandrel bars which are subjected to tension and which only have the task of determining the diameter of the hollow block to bring the desired dimension with the desired wall thickness and so to produce an extension only in the tangential direction while roughly maintaining the weight per meter or the axial dimension. The exact final dimension is generated in a sizing mill or expander. Once this has been achieved, there is a seamless pipe 10 after the finishing, the dimensions of which, depending on the deformation units used and on the hollow block coming from the hollow extrusion plant, are quite comparable to those of the welded large pipes. Furthermore, it is also conceivable to achieve dimensions without great difficulty, which are superior to the welded large pipes of conventional production both in the length of the large pipe and in its diameter and wall thickness. Finally, it is also possible to use this type of large pipe production to process high-quality steel more safely and economically because of the lack of welding risk. The advantages of this manufacturing process are, in particular, a lower outlay on systems and thus investments, as well as a lower outlay on energy compared to welded ones. Large pipes. This makes it possible to produce large pipes in an economically justifiable manner that do not have the risk of a weld seam, are more economical to produce and can be kept variable in their dimensions, in particular with regard to the pipe length, combined with the advantage of processing high-quality steels.

Claims (1)

  1. Process for producing pipes of large diameter, starting from continuously cast hollow blocks which are rolled out by skew rolls across a mandrel and are then expanded in an expanding mill, characterised in that the hollow blocks are rolled out to the final length in the skew rolling mill with a mandrel which is under tension and that the desired final measurement is set by expanding without stretching in the axial direction.
EP85111773A 1984-10-19 1985-09-18 Method for producing seamless steel tubes with a great diameter Expired - Lifetime EP0178477B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT85111773T ATE49143T1 (en) 1984-10-19 1985-09-18 PROCESS FOR MAKING LARGE DIAMETER SEAMLESS STEEL PIPES.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3438395 1984-10-19
DE3438395A DE3438395C1 (en) 1984-10-19 1984-10-19 Process for producing seamless steel pipes of large diameter

Publications (2)

Publication Number Publication Date
EP0178477A1 EP0178477A1 (en) 1986-04-23
EP0178477B1 true EP0178477B1 (en) 1990-01-03

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EP85111773A Expired - Lifetime EP0178477B1 (en) 1984-10-19 1985-09-18 Method for producing seamless steel tubes with a great diameter

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US (1) US4809423A (en)
EP (1) EP0178477B1 (en)
JP (1) JPS6199503A (en)
KR (1) KR890003804B1 (en)
AT (1) ATE49143T1 (en)
DE (2) DE3438395C1 (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19520833C2 (en) * 1994-06-16 1998-06-04 Mannesmann Ag Process for the production of a seamless hot-worked pipe
IT1316715B1 (en) * 2000-03-03 2003-04-24 A M T Robotics S R L PROCEDURE FOR THE REALIZATION OF METAL TUBES AND RELATED EQUIPMENT
DE10219155C1 (en) * 2002-04-29 2003-12-18 Welser Profile Ag A metal mining plug
CN100574909C (en) * 2004-01-16 2009-12-30 住友金属工业株式会社 The manufacture method of seamless pipe
WO2010128197A1 (en) * 2009-05-06 2010-11-11 Luvata Espoo Oy Method for producing a cooling element for pyrometallurgical reactor and the cooling element

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Publication number Priority date Publication date Assignee Title
US605027A (en) * 1898-05-31 Mechanism for- expanding or enlarging metallic tubes
DE628393C (en) * 1936-04-02 Friedrich Peters Rolling mill for expanding hollow bodies
US401143A (en) * 1889-04-09 flagler
US324118A (en) * 1885-08-11 Process of manufacturing tubing
US1712972A (en) * 1927-11-08 1929-05-14 Ralph C Stiefel Method of forming blanks for making seamless tubes
US1858920A (en) * 1928-03-23 1932-05-17 Nat Tube Co Method of making seamless tubes
US1973687A (en) * 1932-02-23 1934-09-11 Bolton C Moise Tube mill
US2025439A (en) * 1933-05-20 1935-12-24 Brownstein Benjamin Mandrel bar for continuous tube rolling mills
US2306771A (en) * 1940-08-27 1942-12-29 Nat Tube Co Method of making metallic tubes
DE1752116A1 (en) * 1968-04-05 1971-05-13 Mannesmann Ag Method and apparatus for manufacturing seamless steel tubes
US3581384A (en) * 1967-06-28 1971-06-01 Mannesmann Ag Method of producing seamless metal tubes
DE1752078A1 (en) * 1968-03-30 1971-07-15 Mannesmann Ag Process for the manufacture of seamless steel tubes of large diameter
DD68215A (en) * 1968-06-27 1969-08-05 Mannesmann Ag METHOD AND DEVICE FOR PRODUCING SEAMLESS PIPES
BE754607A (en) * 1969-08-18 1971-01-18 Mannesmann Ag HOLLOW BODY MANUFACTURING PROCESS
US4091524A (en) * 1974-07-19 1978-05-30 Ali Bindernagel Process for producing pipe blooms
JPS57177812A (en) * 1981-04-24 1982-11-01 Kawasaki Steel Corp Manufacture of large sized seamless pipe and its device
JPS58199603A (en) * 1982-05-18 1983-11-21 Nippon Steel Corp Continuous production of seamless pipe
JPS5912362A (en) * 1982-07-13 1984-01-23 Sumitomo Electric Ind Ltd Apparatus for measuring space electric field

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Publication number Publication date
DE3438395C1 (en) 1986-04-10
ATE49143T1 (en) 1990-01-15
EP0178477A1 (en) 1986-04-23
JPS6199503A (en) 1986-05-17
DE3575090D1 (en) 1990-02-08
KR890003804B1 (en) 1989-10-05
US4809423A (en) 1989-03-07
KR860003064A (en) 1986-05-19

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