EP0281238A1 - Procédé pour couler des alliages Al-Li - Google Patents

Procédé pour couler des alliages Al-Li Download PDF

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Publication number
EP0281238A1
EP0281238A1 EP88300635A EP88300635A EP0281238A1 EP 0281238 A1 EP0281238 A1 EP 0281238A1 EP 88300635 A EP88300635 A EP 88300635A EP 88300635 A EP88300635 A EP 88300635A EP 0281238 A1 EP0281238 A1 EP 0281238A1
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EP
European Patent Office
Prior art keywords
alloys
casting
rolls
cast
twin
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.)
Withdrawn
Application number
EP88300635A
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German (de)
English (en)
Inventor
David James Lloyd
Iljoon Jin
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.)
Rio Tinto Alcan International Ltd
Original Assignee
Alcan International Ltd Canada
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Filing date
Publication date
Application filed by Alcan International Ltd Canada filed Critical Alcan International Ltd Canada
Publication of EP0281238A1 publication Critical patent/EP0281238A1/fr
Withdrawn legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
    • B22D11/0622—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by two casting wheels

Definitions

  • This invention relates to the casting of Al-Li alloys by means of a twin-roll caster.
  • Various strip casting techniques are known, of which one involves the use of twin-roll type casters, such as the continuous strip casters manufactured by Hunter Engineering Company of Riverside, California.
  • twin-roll caster the molten metal is solidified in the nip of a pair of heavily-chilled steel rolls, which draw the molten metal out of an insulated injector nozzle in close proximity to the rolls, the cast material being in the form of a slab e.g. in a thickness range of up to 25 mm and being typically cast at a speed of 60 to 200 cm/min.
  • the metal is essentially fully solidified when it passes the centre line of the caster rolls; it is subjected to heavy compression and some plastic deformation as it passes through the gap between the rolls, with the consequence that its surfaces are in excellent heat exchange contact with the caster rolls, which are intensively water cooled.
  • twin-roll casters include high cooling rate; no metal-water contact; and direct casting of thin gauge material.
  • Another continuous casting technique involves directing a jet of molten metal from a pressurised vessel at the nip between cooled rotating roll.
  • the process is controlled by the ratio of the molten metal jet velocity to the roll velocity and the jet mass flow rate; and is suitable for making foil of thickness 10-500 microns and width from 1-25 mm.
  • rotation of the rolls is used to draw molten metal from an unpressurised vessel.
  • the twin-­roll casting technique is controlled by the roll speed and the melt temperature; and is suitable for making strip from 1-25 mm, generally 4-15 mm, thick and up to 1.5 m wide.
  • Ribbon casting is described by E. Babic et al in Journal of Physics, 3 (1970), 1014-5; and by Y. V. Murty and R. P. I. Adler in Journal of Materials Science 17 (1982) 1945-54.
  • Use of the technique to cast Al-Li alloys under inert atmosphere is described in JPA 57.11752 and JPA 60 227950.
  • Al-Li alloys can show a 10% density reduction and a 10% stiffness increase compared to conventional Al alloys, and are on this account of great interest to the aircraft and aerospace industries. Ribbon cast Al-­Li alloys would not be suitable for such uses.
  • Al-Li alloys are therefore generally cast in ingot form by a direct chill process in which the molten metal is poured into open-ended mould, in which a solidified skin is formed at the point of contact of the molten metal with the chilled surface of the mould and coolant is applied to the solidified surface of the ingot as it issues from the bottom end of the mould.
  • Such methods have however rather major disadvantages:-
  • Twin-roll casting can avoid a) because there is no exposed water in the system and the problem associated with c) is reduced because the alloy is produced at smaller thickness.
  • twin-roll casting has not previously been used for casting Al-Li alloys. The first is that we have found it completely impossible to twin-roll cast Al-Li alloys in air; we were unable to achieve stable heat transfer from molten metal to chilled rolls. The second is the generally held belief that twin-roll casting of alloys having a long freezing range is unsatisfactory due to the centreline segregation problem outlined above.
  • the third is that, it is generally accepted that Al-Li alloys are more difficult to cast than Al-Mg alloys when alloying additions expressed in percent by weight are the same; and it is known to be difficult to cast commercially acceptable Al-Mg alloys on a twin roll caster.
  • This invention is based on our discovery that, provided suitable casting conditions are maintained, Al-Li alloys having a long melting range can be very satisfactorily cast by means of a twin-roll caster.
  • the invention provides a method of casting an Al alloy by means of a twin-roll caster in which the molten metal is solidified in the nip of a pair of chilled rolls which draw molten metal out from a nozzle adjacent the rolls, an inert gas being used to shield molten metal between the nozzle and the rolls from atmospheric oxidation and the metal being cast in the form of a slab from 2-7 mm thick, characterized in that the Al alloy is an Al-Li alloy.
  • Preferred Al-Li alloys contain from 1.5% to 4.0% Li, and may also include one or more of the following: Cu up to 3.0%; Mg up to 2.0%, Zr up to 0.2%.
  • Typical commercial Al-Li alloy specifications are AA 2090; AA2091; AA8090 and AA8091.
  • This invention can be regarded as an improved method of casting Al-Li alloys; or as an improved method of casting Al-Mg or Al-Cu alloys which comprises including Li in the alloys so as to enable them to be twin-roll cast.
  • molten metal in any supply vessel or channel upstream of the nozzle is also shrouded by inert gas and protected from atmospheric oxidation.
  • a suitable inert gas is argon.
  • the diameter of the twin rolls used for casting have a significant effect on the method.
  • an experimental caster with 30cm diameter rolls, which proved particularly suitable for casting slab from 2-7mm thick.
  • Commercial Hunter casters use twin rolls 60cm or even 90cm in diameter, which are suitable for casting slab from 5-25m thick.
  • small diameter rolls i.e. 20cm to 50cm have advantages: slab cast at 3-4mm thick is easily rolled to the thickness, typically around 1mm, required by the aircraft industry. Also, precise positioning of the metal feed tip in relation to the rolls is required, and this is more easily achieved with small rolls than with large ones.
  • twin-roll casting is not possible because stable transfer of heat from the metal to the rolls cannot be achieved.
  • This maximum speed depends on the thickness of the cast slab and also on the alloy composition. For example, when casting 3mm slab of Al-2.5% Li alloy, speeds up to 200 cm/min can be achieved. For Al-2.5% Mg alloys the highest speed obtainable is 120cm/min, and a similar relationship also holds true for Al-Cu alloys. Both Al-2.5% Li and Al-2.5% Mg have a freezing range of about 30°C.
  • centreline segregation is likely to be further reduced by the centreline segregation problem noted above.
  • the extent to which centreline segregation can be tolerated depends in part on the thickness of the final rolled metal sheet. It is surprisingly found that, for a given casting speed and slab thickness, centreline segregation is less pronounced with Al-Li alloys then with Al-Mg alloys of similar composition and freezing range.
  • twin-roll cast strips of conventional thickness from 7-15 mm from long freezing range alloys, partly as a result of the narrow operating window (because the maximum casting speed is low), and partly because of the centreline segregation problem.
  • This invention solves this problem for Al-Li alloys, by casting thinner strips, from 2-7 mm and preferably 2-4 mm guage. Smaller rolls of diameter 20-50 cm may be used for operational convenience.
  • the weight of metal cast in unit time is essentially the same as if a thicker strip had been cast. And the thinner strip is in a better state for subsequent processing.
  • the heat flow is essentially one-dimensional, i.e. towards the rolls.
  • heat also flows in the direction of the strip, and may cause metal to freeze in the feed tip. This will occur if the speed is reduced much below 50cm/min.
  • the casting speed is thus preferably higher than 50cm/min. In cases where it is less than about 50cm/min, casting is not possible by the twin-roll technique. In the light of the prior work on Al-Mg alloys, it was not apparent that casting of Al-Li alloys would be possible by the twin-­roll technique.
  • the method is effective to twin-roll cast Al-Li alloys, which are long freezing range alloys, it is not effective to cast other long freezing range Al alloys, even when an inert gas atmosphere is used. It is currently believed that the method works with Al-­Li alloys because this system can be supercooled. That is, the alloys can be cooled to a temperature below the liquidus temperature and held there in the liquid state while the heat of fusion is removed. Al-­Mg alloys cannot be significantly supercooled.
  • the method of the invention has the following advantages over conventional DC casting processes: - - There is no free water associated with the process, which is therefore safe from an explosive point of view. - A cooling rate of 2000-3000°C/s for 3 mm strip is higher than is achieved in DC casting or in other continuous techniques such as twin-belt casting or block casting, and produces a fine uniform cell structure over the surface of the strip. - Because the method involves solidification of a strip over a short sump length, with very rapid solidification, conventional hot cracking is not a problem. - Provided there is no oxide film formation at the nose tip oxide film behaviour does not influence the casting process. - Twin roll cast slab has a starting gauge typically of less than 10 mm. As a result, the amount of cold rolling required is much less than with a DC cast ingot, and it is possible that the anisotropy of the rolled sheet may be reduced.
  • the machine comprises two intensively cooled rolls 10, 12 and a metal feed tip 14 located precisely in relation to them.
  • a stable flow of molten metal emerges from the feed tip and occupies a zone 16. Heat is transferred from the metal to the rolls, as a result of which the metal freezes and is eventually recovered as strip 18.
  • the region between the feed tip and the nip of the rolls may be considered in two zones, a casting zone 20 in which the metal is solidified, and a rolling zone 22 in which the solid metal is deformed.
  • zone 24 represents molten metal
  • zone 26 represents solid Al
  • zone 28 represents a mixture of the two.
  • the vertical line 30 represents the composition Al-3% Li.
  • the line 32 between zones 24 and 28 represents the liquidus
  • line 34 between zones 26 and 28 represents the solidus.
  • Line 30 intersects lines 32 and 34 at temperatures of 650°C and 620°C, indicating a freezing range of 30°C for this alloy under equilibrium conditions. However, if molten metal of this composition is rapidly cooled it can be supercooled, that is to say, it does not start to freeze until it reaches a temperature below 650°C. This is indicated by the arbitrary line 36 which represents the liquidus under conditions of rapid cooling.
  • Al-Li alloys shown in Table 1 were cast on a 305 mm diameter roll caster.
  • the as-cast slabs were 3 mm thick and 100 mm wide.
  • the alloys were melted in a graphite crucible without Li. A a melt temperature of 760°C, the melt was transferred to a ladle and the weighed Li metal was introduced into the melt by using a phosphorizer. The alloyed melt was fluxed with a 90% Ar + 10% Cl2 mixed gas for about 10 minutes.
  • the metal feed tip (nozzle) was made of a conventional rigidized Kaowool. The rolls were coated with a fine dry graphite powder.
  • the alloys could be case at a stable speed in the range of 0.9-1.5 m/min.
  • the slab surface was completely free of thick oxide powder layers.
  • the cast structure of alloys 1 and 2 were very fine and uniform (2-5 microns cell size) throughout the thickness.
  • the structure of alloy 4 was also very fine but had some centre segregates at certain locations.
  • the structure of alloy 3 was slightly coarse (a cell size of 5-10 microns) and had some centre segregates.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Continuous Casting (AREA)
EP88300635A 1987-02-09 1988-01-26 Procédé pour couler des alliages Al-Li Withdrawn EP0281238A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB878702837A GB8702837D0 (en) 1987-02-09 1987-02-09 Casting al-li alloys
GB8702837 1987-02-09

Publications (1)

Publication Number Publication Date
EP0281238A1 true EP0281238A1 (fr) 1988-09-07

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Family Applications (1)

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EP88300635A Withdrawn EP0281238A1 (fr) 1987-02-09 1988-01-26 Procédé pour couler des alliages Al-Li

Country Status (4)

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EP (1) EP0281238A1 (fr)
JP (1) JPS63286246A (fr)
GB (1) GB8702837D0 (fr)
NO (1) NO880546L (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0653497A1 (fr) * 1993-11-15 1995-05-17 Fuji Photo Film Co., Ltd. Méthode pour fabriquer un support d'une plaque d'impression à plat
US8025093B2 (en) * 2006-03-08 2011-09-27 Kobe Steel, Ltd. Process for manufacturing cast aluminum alloy plate
US8365808B1 (en) 2012-05-17 2013-02-05 Almex USA, Inc. Process and apparatus for minimizing the potential for explosions in the direct chill casting of aluminum lithium alloys
US8479802B1 (en) 2012-05-17 2013-07-09 Almex USA, Inc. Apparatus for casting aluminum lithium alloys
ITMI20121688A1 (it) * 2012-10-09 2014-04-10 Bruno Presezzi Spa Dispositivo di iniezione, particolarmente per procedimenti di estrusione di alluminio.
US9616493B2 (en) 2013-02-04 2017-04-11 Almex USA, Inc. Process and apparatus for minimizing the potential for explosions in the direct chill casting of aluminum lithium alloys
US9936541B2 (en) 2013-11-23 2018-04-03 Almex USA, Inc. Alloy melting and holding furnace

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU2002951075A0 (en) * 2002-08-29 2002-09-12 Commonwealth Scientific And Industrial Research Organisation Twin roll casting of magnesium and magnesium alloys

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE427270A (fr) *

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5858963A (ja) * 1981-10-05 1983-04-07 Mitsubishi Keikinzoku Kogyo Kk 連続鋳造板の製造方法
JPS60227950A (ja) * 1984-04-27 1985-11-13 Pioneer Electronic Corp Ａｌ−Ｌｉ合金薄板の製造方法
JPS62270253A (ja) * 1986-05-17 1987-11-24 Sky Alum Co Ltd Ｌｉを含むアルミニウム基合金板材の製造方法

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE427270A (fr) *

Non-Patent Citations (5)

* Cited by examiner, † Cited by third party
Title
JOURNAL OF METALS, vol. 34, no. 6, June 1982, pages 70-75, Warrendale, US; I.JIN et al.: "Centerline segregation in twin-roll-cast aluminum alloy slab" *
PATENT ABSTRACTS OF JAPAN, vol. 10, no. 88 (M-467)[2145], 5th April 1986, page 94 M 467; & JP-A-60 227 950 (PIONEER K.K.) 13-11-1985 *
PATENT ABSTRACTS OF JAPAN, vol. 11, no. 184 (C-427)[2631], 12th June 1987; & JP-A-62 004 842 (FURUKAWA ELECTRIC CO., LTD.) 10-01-1987 (Cat. A) *
PATENT ABSTRACTS OF JAPAN, vol. 6, no. 71 (M-126)[949], 6th May 1982, page 129 M 126; & JP-A-57 011 752 (PIONEER K.K.) 21-01-1982 *
PATENT ABSTRACTS OF JAPAN, vol. 7, no. 149 (M-225)[1294], 30th June 1983, page 45 M 225; & JP-A-58 058 963 (MITSUBISHI KEIKINZOKU KOGYO K.K.) 07-04-1983 *

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5531840A (en) * 1993-11-15 1996-07-02 Fuji Photo Film Co., Ltd. Method of producing support for planographic printing plate
EP0653497A1 (fr) * 1993-11-15 1995-05-17 Fuji Photo Film Co., Ltd. Méthode pour fabriquer un support d'une plaque d'impression à plat
US8025093B2 (en) * 2006-03-08 2011-09-27 Kobe Steel, Ltd. Process for manufacturing cast aluminum alloy plate
US10646919B2 (en) 2012-05-17 2020-05-12 Almex USA, Inc. Process and apparatus for direct chill casting
US8365808B1 (en) 2012-05-17 2013-02-05 Almex USA, Inc. Process and apparatus for minimizing the potential for explosions in the direct chill casting of aluminum lithium alloys
US8479802B1 (en) 2012-05-17 2013-07-09 Almex USA, Inc. Apparatus for casting aluminum lithium alloys
US10946440B2 (en) 2012-05-17 2021-03-16 Almex USA, Inc. Process and apparatus for minimizing the potential for explosions in the direct chill casting aluminum alloys
US9849507B2 (en) 2012-05-17 2017-12-26 Almex USA, Inc. Process and apparatus for minimizing the potential for explosions in the direct chill casting of aluminum lithium alloys
US9895744B2 (en) 2012-05-17 2018-02-20 Almex USA, Inc. Process and apparatus for direct chill casting
ITMI20121688A1 (it) * 2012-10-09 2014-04-10 Bruno Presezzi Spa Dispositivo di iniezione, particolarmente per procedimenti di estrusione di alluminio.
WO2014056796A1 (fr) * 2012-10-09 2014-04-17 Bruno Presezzi S.P.A. Dispositif d'injection destiné en particulier à des procédés d'extrusion d'aluminium et procédé d'extrusion associé
US9764380B2 (en) 2013-02-04 2017-09-19 Almex USA, Inc. Process and apparatus for direct chill casting
US9950360B2 (en) 2013-02-04 2018-04-24 Almex USA, Inc. Process and apparatus for minimizing the potential for explosions in the direct chill casting of lithium alloys
US10864576B2 (en) 2013-02-04 2020-12-15 Almex USA, Inc. Process and apparatus for minimizing the potential for explosions in the direct chill casting of lithium alloys
US9616493B2 (en) 2013-02-04 2017-04-11 Almex USA, Inc. Process and apparatus for minimizing the potential for explosions in the direct chill casting of aluminum lithium alloys
US9936541B2 (en) 2013-11-23 2018-04-03 Almex USA, Inc. Alloy melting and holding furnace
US10932333B2 (en) 2013-11-23 2021-02-23 Almex USA, Inc. Alloy melting and holding furnace

Also Published As

Publication number Publication date
JPS63286246A (ja) 1988-11-22
NO880546D0 (no) 1988-02-08
NO880546L (no) 1988-08-10
GB8702837D0 (en) 1987-03-18

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