EP0726114A2 - Verfahren und Vorrichtung zum Verhindern von Feuchtigkeits- und Wasserstoffaufnahme von hygroscopische Salzschmelzen beim Blockguss von Al-Li Legierungen - Google Patents

Verfahren und Vorrichtung zum Verhindern von Feuchtigkeits- und Wasserstoffaufnahme von hygroscopische Salzschmelzen beim Blockguss von Al-Li Legierungen Download PDF

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Publication number
EP0726114A2
EP0726114A2 EP96101738A EP96101738A EP0726114A2 EP 0726114 A2 EP0726114 A2 EP 0726114A2 EP 96101738 A EP96101738 A EP 96101738A EP 96101738 A EP96101738 A EP 96101738A EP 0726114 A2 EP0726114 A2 EP 0726114A2
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EP
European Patent Office
Prior art keywords
casting
aluminum
molten salt
salt bath
cover
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Withdrawn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
EP96101738A
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English (en)
French (fr)
Other versions
EP0726114A3 (de
Inventor
Leslie Kirby J.
Richard O. Kendrick
Steven M. Kroml
George W. Steele
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.)
Reynolds Metals Co
Original Assignee
Reynolds Metals Co
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 Reynolds Metals Co filed Critical Reynolds Metals Co
Publication of EP0726114A2 publication Critical patent/EP0726114A2/de
Publication of EP0726114A3 publication Critical patent/EP0726114A3/de
Withdrawn legal-status Critical Current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
    • B22D11/10—Supplying or treating molten metal
    • B22D11/11—Treating the molten metal

Definitions

  • the present invention is directed to a method and apparatus for reducing moisture pick up of hygroscopic molten salts which are used during aluminum-lithium alloy casting and, in particular, to the use of an inert gas to control humidity levels of the atmosphere in the casting environment.
  • Aluminum-lithium alloys are selected in these applications for reasons of their material properties such as low density, high strength, high fracture toughness and high modulus of elasticity. Using these alloys in aircraft applications effectively reduces the overall weight of the aircraft without any loss in mechanical or other physical properties.
  • a flux cover over the molten metal surface.
  • a flux is maintained over the exposed molten metal surface and over the inert gas-shielded peripheral region.
  • the flux can be a halide-type flux such as lithium chloride.
  • the present invention provides a method and apparatus for reducing the moisture pick up of a hygroscopic molten salt bath used in aluminum-lithium alloy ingot casting. By reducing the moisture pick up by the hygroscopic molten salts, the aluminum-lithium alloy ingot cast quality is improved through reduction in residual hydrogen levels.
  • Another object of the present invention is to control the moisture pick up of hygroscopic molten salt baths used during aluminum-lithium alloy casting.
  • a still further object of the present invention is to provide an apparatus for casting aluminum-lithium alloy ingots which permits control of moisture in the atmospheric air present in the casting environment.
  • the present invention is an improvement over methods using molten salt baths during the casting of aluminum-lithium alloy ingots or slabs.
  • an effective amount of an inert gas is supplied to a moisture-containing atmospheric gas in contact with the molten salt bath to reduce salt bath moisture pick up.
  • the molten salt bath is utilized during at least one of melting and/or alloying of the aluminum-lithium alloy in a furnace, transferring of the molten aluminum-lithium alloy from a furnace to a casting station, and casting of the aluminum-lithium alloy.
  • argon is used as the inert gas and is supplied after initiation of the casting step.
  • Argon gas is supplied in amounts which reduce the relative humidity of the atmospheric air in contact with the molten salt bath, preferably reducing the relative humidity by at least 5% and more preferably by 10 to 20%.
  • the present invention also provides improvements in known apparatus used for melting and/or casting of aluminum-lithium alloys.
  • means are provided for supplying an effective amount of an inert gas to moisture-containing atmospheric gas in contact with the molten salt bath covering a molten aluminum-lithium bath.
  • the means for supplying the inert gas reduces moisture pick up by the molten salt bath by reducing the moisture content of the atmospheric gas.
  • the means for supplying further comprises a cover over at least one of the melting furnace, the transfer arrangement between the furnace and the casting station and the casting station.
  • the inert gas is supplied to the covers via piping to mix with the atmospheric gas thereunder.
  • the covers are vented to permit purging of the atmospheric gas to reduce the moisture content of the atmospheric gas - inert gas mixture.
  • the inventive method also provides an improved cast ingot which exhibits reduced levels of hydrogen as compared to ingots cast during hot and humid weather conditions.
  • the inventive method and apparatus are generally designated by the reference numeral 10 and seen to include a melt and alloying furnace 1 having a cover 3 thereover, a transfer station 20 and a casting station 30.
  • the transfer station 20 includes trough 5, filter 7 and pour trough 9.
  • the pour trough 9 includes a cover 11 and a downspout 13.
  • the downspout 13 channels molten metal into the casting mold 15.
  • the casting station 30 also includes a casting cover 17 which covers the ingot head 19.
  • the starter bar 22 moves downwardly by the hydraulic drive 21 for casting initiation.
  • an aluminum-lithium alloy 23 is provided in the furnace 1.
  • the aluminum-lithium alloy can be derived from scrap or alloyed by the proper combination of alloying components.
  • the melt 23 then travels through the trough 5, filter 7, pour trough 9 and downspout 13 to the casting mold 15. Once the metal in the casting mold 15 is at the proper level, ingot formation is initiated by downward movement of the starter bar 22.
  • the molten bath 23 has a molten salt bath cover 25 thereover.
  • the salt bath cover 25 can be initiated in the melt and alloying furnace 1 so that it flows with the molten metal into the pour trough 9.
  • the baffle 8 in the filter forces the aluminum-lithium alloy to be submerged, leaving the molten salt cover intact on the metal surface.
  • only the molten metal 23 flows through trough 5 and filter 7 to the pour trough 9. In this mode the salt bath 25 is either not used or reinitiated in the pour trough 9.
  • Another molten salt bath 27 can be maintained on the ingot head 19 during casting.
  • any molten salt bath can be used as a cover during the casting sequence, with a lithium chloride containing salt composition being preferred. More preferably, the salt bath is a mixture of lithium chloride and another salt selected from the group of potassium chloride, lithium fluoride and sodium chloride as disclosed in United States Patent Application Serial No. 08/034,329, filed March 22, 1993, which is incorporated herein by reference.
  • the molten salt bath 25 as described above can be initiated in one or more of the alloying furnace 1, the pour trough 9 or the casting station 30.
  • the inventive method and apparatus include the provision for injection or supply of an inert gas to at least one of the molten alloying furnace 1, pour trough 9 or casting station 30.
  • the inert gas is supplied during these steps or in these apparatus as a means to reduce the moisture content of atmospheric air in these casting environment zones to reduce moisture pick up by the hygroscopic molten salt baths 25 or 27.
  • Injection or supply of the inert gas effectively dilutes the atmospheric air or reduces its relative humidity level to a point where the moisture pick up by the hygroscopic molten salt is vastly reduced or eliminated.
  • the salt bath cover provides the protection of the aluminum-lithium alloy from surface oxidation, hydrogen pickup, losses, etc; while the inert cover protects the molten salts from typically non-controllable ambient weather conditions.
  • argon gas is preferred. Even more preferred is argon gas with less than 5 ppm moisture.
  • argon gas is supplied to the melt and alloying furnace cover 3 via piping 29. With this supply of argon gas, the relative humidity level of the atmospheric gas 31 under the cover 3 is reduced to a level which does not adversely affect the quality of the molten aluminum-lithium alloy 23.
  • argon gas can be supplied via piping 33 to the pour trough cover 11. With this supply of argon gas, the moisture in the atmospheric air 35 under the cover 11 is reduced for more effective ingot casting.
  • a similar piping arrangement 37 provides argon gas to the casting station cover 17 to effectively reduce the humidity levels in the atmospheric air thereunder.
  • Each of the covers 3, 11 and 17 are configured over their respective molten aluminum-lithium alloy containers to allow venting of moisture-laden gas. Venting of this gas is represented by the letter A for each of the covers 3, 11 and 17.
  • the argon gas can be supplied during melting and/or alloying of the bath 23, it is preferably initiated at the onset of casting or downward movement of the starter bar 22.
  • the argon gas can be supplied by any conventional source and controlled using conventional sensing and controller arrangements.
  • Tonnage-based experiments have demonstrated that supply of argon gas under the various covers wherein a 10 to 20% reduction in relative humidity is achieved resulted in improved ingot quality as measured by lower hydrogen content in the ingot.
  • the reduction in humidity equates to a specific and effective amount of argon to be supplied under a given cover.
  • the effective amount is considered to be that amount which when supplied in a given cover will reduce the moisture content of the atmospheric air thereunder to a level of moisture which does not adversely affect the molten salt bath or aluminum-lithium alloy. It is within the skill of the artisan given the knowledge of existing weather conditions such as temperature and relative humidity and the volume of atmospheric air enclosed by a given cover to calculate the necessary amount of argon to achieve a desired level of relative humidity reduction. For a particular set of weather conditions, it may be necessary only to lower the relative humidity by 5%, whereas other weather conditions may dictate higher reductions, e.g. in excess of 20%.
  • the effective amount of argon also can be based upon a target dew point temperature rather than a reduction in relative humidity levels. Again, this is well within the skill of the artisan knowledgeable in psychometrics, various cover configurations, and venting passages associated therewith.
  • the molten salt bath may be replenished by adding salt through one or more of the doors 41 in the covers 3, 11 and 17, see the sole figure.
  • the doors 41 are closed when the argon is supplied into the respective covers.
  • the argon gas can be supplied intermittently or continuously to achieve the desired reduction in moisture content of the atmospheric air under a given cover.
  • the argon flow rates can be set to preselected values as described above or can be controlled using humidity sensors in the various covers. In the latter mode, values of humidity levels in the environments under the various covers are sensed by the humidity sensors and the sensed values are relayed to a control scheme for controlling the argon gas flow rate. If humidity levels were to unexpectedly increase during a casting operation, the argon flow rate would be increased accordingly.
  • the furnace 1, transfer station 20 and casting station 30 are representative of known casting components in the field of aluminum-lithium ingot alloy casting. As such, a further description thereof is not deemed necessary for understanding of the invention.
  • the use of the inert gas-atmospheric air mixture and salt bath in the melting furnace eliminates or reduces excessive furnace wall thermitting after the casting has been completed.
  • salt is added to the furnace during melting of aluminum-lithium scrap to keep the lithium in the bath. After fluxing and skimming of the melt prior to casting, some hydrogen regassing would occur during hot and/or humid days. In addition, since the salt bath became depleted during the casting operation, excessive furnace wall thermitting occurred after the cast when the furnace lid was opened. Upon opening the furnace lid, the furnace interior is exposed to ambient conditions which causes excessive oxidation of the furnace lining which can result in premature furnace lining failure.
  • the molten salt bath is preferably maintained over the molten metal in the melting furnace during the casting operation.
  • the inert gas is supplied to the atmosphere in the furnace as described above.
  • the flow rates of argon gas in the ingot head are set at 80 to 90 SCFM.
  • the argon flow in the melting furnace is around 30 SCFM during start up, i.e. about 5 minutes, and then reduced to about 15 to 20 SCFM.
  • the argon flow in the pour trough cover is also around 15 to 20 SCFM.
  • the argon flow rates can vary depending on the humidity levels present during casting as well as the configuration of the various covers.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Continuous Casting (AREA)
EP96101738A 1995-02-10 1996-02-07 Verfahren und Vorrichtung zum Verhindern von Feuchtigkeits- und Wasserstoffaufnahme von hygroscopische Salzschmelzen beim Blockguss von Al-Li Legierungen Withdrawn EP0726114A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US38684095A 1995-02-10 1995-02-10
US386840 1995-02-10

Publications (2)

Publication Number Publication Date
EP0726114A2 true EP0726114A2 (de) 1996-08-14
EP0726114A3 EP0726114A3 (de) 1997-09-10

Family

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EP96101738A Withdrawn EP0726114A3 (de) 1995-02-10 1996-02-07 Verfahren und Vorrichtung zum Verhindern von Feuchtigkeits- und Wasserstoffaufnahme von hygroscopische Salzschmelzen beim Blockguss von Al-Li Legierungen

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0965403A1 (de) * 1998-06-17 1999-12-22 FEMUK Betriebsberatung GmbH Zerlegung, Anstauung und Beseitigung verbleibender Restsubstanzen von Aluminiumoxid bei flüssigen Aluminium-Legierungen in Giessrinnen, Giesskanälen o.dgl. vor Einlauf in Kokillen oder Kokillenaggregaten
US7267158B2 (en) 2003-07-02 2007-09-11 Alcoa Inc. Control of oxide growth on molten aluminum during casting using a high moisture atmosphere
CN102294465A (zh) * 2011-09-28 2011-12-28 西南铝业（集团）有限责任公司 一种熔体保护装置及方法
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
US9764380B2 (en) 2013-02-04 2017-09-19 Almex USA, Inc. Process and apparatus for direct chill casting
US9936541B2 (en) 2013-11-23 2018-04-03 Almex USA, Inc. Alloy melting and holding furnace
CN110923465A (zh) * 2019-10-15 2020-03-27 北京理工大学 铝锂合金铸造中减少氢含量的方法
US11272584B2 (en) 2015-02-18 2022-03-08 Inductotherm Corp. Electric induction melting and holding furnaces for reactive metals and alloys

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1181518A (en) * 1966-08-15 1970-02-18 Ass Elect Ind Improvements relating to Production of Cast Metal.
US4556535A (en) * 1984-07-23 1985-12-03 Aluminum Company Of America Production of aluminum-lithium alloy by continuous addition of lithium to molten aluminum stream
US4770697A (en) * 1986-10-30 1988-09-13 Air Products And Chemicals, Inc. Blanketing atmosphere for molten aluminum-lithium alloys or pure lithium
RU2003710C1 (ru) * 1992-01-03 1993-11-30 Сергей Борисович Комаров Способ отливки слитков из высокоактивных сплавов
RU2048568C1 (ru) * 1993-02-05 1995-11-20 Комаров Сергей Борисович Способ получения алюминиево-литиевых сплавов

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0965403A1 (de) * 1998-06-17 1999-12-22 FEMUK Betriebsberatung GmbH Zerlegung, Anstauung und Beseitigung verbleibender Restsubstanzen von Aluminiumoxid bei flüssigen Aluminium-Legierungen in Giessrinnen, Giesskanälen o.dgl. vor Einlauf in Kokillen oder Kokillenaggregaten
US7267158B2 (en) 2003-07-02 2007-09-11 Alcoa Inc. Control of oxide growth on molten aluminum during casting using a high moisture atmosphere
CN102294465A (zh) * 2011-09-28 2011-12-28 西南铝业（集团）有限责任公司 一种熔体保护装置及方法
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
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
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
US9764380B2 (en) 2013-02-04 2017-09-19 Almex USA, Inc. Process and apparatus for direct chill casting
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
US11272584B2 (en) 2015-02-18 2022-03-08 Inductotherm Corp. Electric induction melting and holding furnaces for reactive metals and alloys
CN110923465A (zh) * 2019-10-15 2020-03-27 北京理工大学 铝锂合金铸造中减少氢含量的方法

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