EP0161051A1 - Alimentation continue ou semi-continue à une tuyère ou un moule de coulée, d'alliage de magnésium liquide traité pour avoir un effet de raffinage du grain - Google Patents

Alimentation continue ou semi-continue à une tuyère ou un moule de coulée, d'alliage de magnésium liquide traité pour avoir un effet de raffinage du grain Download PDF

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Publication number
EP0161051A1
EP0161051A1 EP85302089A EP85302089A EP0161051A1 EP 0161051 A1 EP0161051 A1 EP 0161051A1 EP 85302089 A EP85302089 A EP 85302089A EP 85302089 A EP85302089 A EP 85302089A EP 0161051 A1 EP0161051 A1 EP 0161051A1
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EP
European Patent Office
Prior art keywords
conduit
alloy
melting pot
continuously
molten
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Withdrawn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
EP85302089A
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German (de)
English (en)
Inventor
Nils Christian Tommeraas
Noel Christopher Spare
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.)
Kongsberg Gruppen ASA
Original Assignee
Kongsberg Vapenfabrikk AS
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 Kongsberg Vapenfabrikk AS filed Critical Kongsberg Vapenfabrikk AS
Publication of EP0161051A1 publication Critical patent/EP0161051A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
    • B22D21/002—Castings of light metals
    • B22D21/007—Castings of light metals with low melting point, e.g. Al 659 degrees C, Mg 650 degrees C

Definitions

  • Magnesium alloys are known to be grain refined by the techniques of either superheating above the liquidus or by the addition of carbon in the form of carbon containing compounds or of other grain refining agents such as zirconium. This phenomenon is important because of the improvement in mechanical properties observed with a reduction in grain size. Both the technique of superheating and the technique involving an addition of grain refining agents are in commercial use, but the established methods have limitations giving rise to production problems. Part of the difficulty is that the mechanisms of the techniques, whilst being known to depend on a modification of the normal nucleation process, are not fully understood. Therefore, all commercial practice is based on empirical data.
  • the metal has to be grain refined on a batch basis in open crucible type pots which are prevented from burning by the addition of a flux to the surface of the metal.
  • a flux to the surface of the metal.
  • the use of such flux which may contain any or all of the compounds MgC1 2 , NaCl, CaCl 2 , CaF 2 and MgO, is undesirable in that great care must be taken in order to avoid any of these materials contaminating the metal used to produce castings. Failure to ensure inclusion-free metal may lead to the production of castings with impaired mechanical properties and poor corrosion resistance.
  • the use of fluxes in the foundry also creates environmental problems because of their hygroscopic and corrosive nature.
  • the liquid metal has to be raised and lowered a distance of approximately 80 cm in a riser tube between the metal level in a holding pot and the level of the feed point of the die. This not only takes time in the injection cycle, but also leads to the creation of turbulence in the metal particularly when the metal falls back to the level in the holding pot. Such turbulence is undesirable in the production of high quality castings since air may aspirate into the metal leading to the formation of oxides in readily oxidisable alloys such as magnesium.
  • One object of the invention is to overcome the problems and disadvantages discussed above and provide a method of continuously or semi-continuously supplying grain refined magnesium alloy to a casting die or mould, as well as an apparatus for carrying out the method.
  • the invention resides in a method and an apparatus as defined in claim 1 and claim 8, respectively.
  • superheating and cooling of the alloy are carried out continuously or semi-continuously in successive sections of a closed conduit through which the molten alloy is passed without contact with the atmosphere, said conduit supplying the alloy at the level of the inlet to the casting die or mould by control of the pressure of the molten alloy in the conduit.
  • the method eliminates some disadvantages of the presently employed superheating processes, it is not restricted to non-use of grain refining compounds. Also other compounds improving the properties of the material such as the general corrosion behaviour may be added in the grain refining process.
  • the molten alloy may be supplied from a melting pot in which ingots are melted under protective atmosphere. However, it is also possible to supply the molten alloy to the conduit direct from a refining furnace omitting the ingot melting step.
  • any suitable method of melting, superheating and cooling the alloy in the melting pot and the conduit, respectively, can be used. However, it is convenient to make use of the high thermal transfer properties of fluidized beds. In such a case the melting pot and said successive sections of the closed conduit are each immersed in closely adjacent separately controlled fluidized beds. Additional heat may be supplied to the melting pot and/or said first section of the conduit by heating elements associated with the pot and the conduit, respectively, or provided in the fluidized bed.
  • the conduit preferably follows a winding path, each of said successive sections of the conduit preferably forming a helix to provide a sufficiently large surface for transferring the necessary heat to or from the alloy in a minimum volume of the bed, thus facilitating rapid heat-up and cool-down periods.
  • a melting pot 1 is immersed in a fluidized bed 2.
  • This part of the apparatus constitutes a melting zone M.
  • Metal may be added to the melting pot 1 in the form of ingots through an air lock 3 which minimizes the loss of oxidation preventing atmosphere in the melting pot 1.
  • oxidation preventing atmosphere may consist of air with an addition of 0.1X SF 6'
  • a filter 4 is installed at the position where the lock 3 opens into the melting pot. Thus, all metal must pass the filter 4 before entering the melting pot 1.
  • the filter may consist of a perforated steel screen which may either be cleaned and replaced periodically or may be in the form of a continuous sheet which is removed from the metal automatically exposing fresh screen to the incoming metal.
  • a conduit 5 is connected to the interior of the melting pot 1 at a level approximately 1/3 of the height of the metal below the surface 15 thereof where any contaminants remaining in the melt will be at a minimum.
  • the conduit 5 passes into a superheating zone I in which a first section 6 of the conduit follows a helical path before continuing into a second helical section 7 positioned in a cooling zone II.
  • Each of the helical sections 6 and 7 are submerged in a fluidized bed 8 and 9, respectively.
  • the fluidized beds 2, 8 and 9 are separated by partitions 10 and 11 and are separately controlled to provide a desired temperature of the molten alloy in the pot 1 and the sections 6 and 7.
  • the fluidized beds may consist of alumina grit fluidized by compressed air which may be pre-heated.
  • the upper levels of the fluidized beds 2, 8 and 9 have been indicated to be the same in Fig 1, but it is obviously possible to use different upper levels of the fluidized beds.
  • the compressed air is supplied in a conventional manner at the lower end of the beds through tuyeres. However, to simplify the drawing such supply is not illustrated. Additional heat may be supplied to the melting pot 1 and/or the section 6 of the conduit 5 by heating elements (not shown) associated with the pot 1 and the conduitns, respectively, or provided in fluidized beds.
  • the temperature provided in zone M may be about 660°C.
  • the metal In the superheating zone I the metal may be heated to approximately 900°C, and in the cooling zone II the metal may be cooled down to a temperature of about 690°C, at which temperature the metal is presented at a level near to the feed point 12 of a casting die 13.
  • the level 14 (Fig 2) of the metal near the feed point 12 is the same as the level 15 of the metal in the melting pot 1.
  • the rate at which ingots are added through the lock 3 corresponds to the rate at which metal is required at the feed point 12.
  • the level of the metal in the melting pot 1 may be adjustable to control the metal level 15 and thereby the level 14 at which molten alloy is supplied at the feed point 12 of the casting die or mould 13.
  • a pneumatic lifting means 16 is diagrammatically shown.
  • the means 16, as illustrated in Fig 2 includes a pneumatically operated valve 17 and an inlet 18 for pressurized gas which may be air containing a small percentage of SF 6 . It should be evident that the introduction of pressurized gas through the opening 18 will make the metal in a riser tube 20 rise provided the valve 17 is closed.
  • a gas inlet 19 serves to provide a protective gas such as air containing a small percentage of SF 6 to the mould or die 13 between each casting cycle, thereby protecting the surface of the metal in the riser tube from oxidation.
  • a skirt 21 providing a gas cushion between the skirt and the riser tube 20.
  • lifting may be achieved by the application of a vacuum to the die.
  • the fludizing gas which is heated in the fluidized beds may be subsequently used for preheating incoming ingots and/or for heating the melting pot. Also recycling of the fludizing air is obviously possible.
  • Zirconium may be used as a grain refining agent for magneisum based alloys not containing aluminium, manganese or silicon.
  • the zirconium in the form of a hardener or compound may be added to the system either at the melting pot or directly into the conduit by means of injection into the metal stream, the required amount being metered at a rate dependent on the metal flow.
  • a static mixing device may be provided in the conduit to agitate the molten alloy flow.
  • heat exchanger systems in the form of fluidized beds are preferred, other heat exchanger systems like salt solutions may be used.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Continuous Casting (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
EP85302089A 1984-03-28 1985-03-26 Alimentation continue ou semi-continue à une tuyère ou un moule de coulée, d'alliage de magnésium liquide traité pour avoir un effet de raffinage du grain Withdrawn EP0161051A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NO841240A NO841240L (no) 1984-03-28 1984-03-28 Fremgangsmaate og apparat til kontinuerlig eller halvkontinuerlig mating av en kokille eller stoepeform med smeltet magnesiumlegering som er behandlet for aa gi en kornforfiningsvirkning
NO841240 1984-03-28

Publications (1)

Publication Number Publication Date
EP0161051A1 true EP0161051A1 (fr) 1985-11-13

Family

ID=19887567

Family Applications (1)

Application Number Title Priority Date Filing Date
EP85302089A Withdrawn EP0161051A1 (fr) 1984-03-28 1985-03-26 Alimentation continue ou semi-continue à une tuyère ou un moule de coulée, d'alliage de magnésium liquide traité pour avoir un effet de raffinage du grain

Country Status (3)

Country Link
EP (1) EP0161051A1 (fr)
JP (1) JPS60227960A (fr)
NO (1) NO841240L (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9592551B2 (en) 2012-03-22 2017-03-14 Rio Tinto Alcan International Limited Metal transfer trough

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2805751A1 (de) * 1978-02-10 1979-08-16 Protherm Ofenbau Gmbh Verfahren und vorrichtung zum schmelzen von gusswerkstoffen
DE2914347A1 (de) * 1978-04-26 1979-11-08 Alusuisse Verfahren und vorrichtung zum filtrieren und entgasen von geschmolzenem metall
DE3244079A1 (de) * 1982-11-29 1984-06-14 BBC Aktiengesellschaft Brown, Boveri & Cie., Baden, Aargau Sieb zur zurueckhaltung von oxydhaeuten beim vergiessen von aluminium und seinen legierungen

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2805751A1 (de) * 1978-02-10 1979-08-16 Protherm Ofenbau Gmbh Verfahren und vorrichtung zum schmelzen von gusswerkstoffen
DE2914347A1 (de) * 1978-04-26 1979-11-08 Alusuisse Verfahren und vorrichtung zum filtrieren und entgasen von geschmolzenem metall
DE3244079A1 (de) * 1982-11-29 1984-06-14 BBC Aktiengesellschaft Brown, Boveri & Cie., Baden, Aargau Sieb zur zurueckhaltung von oxydhaeuten beim vergiessen von aluminium und seinen legierungen

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9592551B2 (en) 2012-03-22 2017-03-14 Rio Tinto Alcan International Limited Metal transfer trough

Also Published As

Publication number Publication date
JPS60227960A (ja) 1985-11-13
NO841240L (no) 1985-09-30

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PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

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Effective date: 19850411

AK Designated contracting states

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STAA Information on the status of an ep patent application or granted ep patent

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18W Application withdrawn

Withdrawal date: 19860121

RIN1 Information on inventor provided before grant (corrected)

Inventor name: SPARE, NOEL CHRISTOPHER

Inventor name: TOMMERAAS, NILS CHRISTIAN