EP0198290B1 - Procédé pour la coulée d'alliages d'aluminium - Google Patents

Procédé pour la coulée d'alliages d'aluminium Download PDF

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Publication number
EP0198290B1
EP0198290B1 EP86104247A EP86104247A EP0198290B1 EP 0198290 B1 EP0198290 B1 EP 0198290B1 EP 86104247 A EP86104247 A EP 86104247A EP 86104247 A EP86104247 A EP 86104247A EP 0198290 B1 EP0198290 B1 EP 0198290B1
Authority
EP
European Patent Office
Prior art keywords
salt mixture
wall
casting
mould
alkali
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
EP86104247A
Other languages
German (de)
English (en)
Other versions
EP0198290A2 (fr
EP0198290A3 (en
Inventor
Friedrich Dr.-Ing. Behr
Heinrich Dipl.-Ing. Ballewski
Wolfgang Grossmann
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.)
ThyssenKrupp Technologies AG
Original Assignee
Thyssen Industrie AG
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 Thyssen Industrie AG filed Critical Thyssen Industrie AG
Publication of EP0198290A2 publication Critical patent/EP0198290A2/fr
Publication of EP0198290A3 publication Critical patent/EP0198290A3/de
Application granted granted Critical
Publication of EP0198290B1 publication Critical patent/EP0198290B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D21/00Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
    • B22D21/002Castings of light metals
    • B22D21/007Castings of light metals with low melting point, e.g. Al 659 degrees C, Mg 650 degrees C
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22CFOUNDRY MOULDING
    • B22C3/00Selection of compositions for coating the surfaces of moulds, cores, or patterns
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D27/00Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
    • B22D27/20Measures not previously mentioned for influencing the grain structure or texture; Selection of compositions therefor

Definitions

  • the invention relates to a method for casting aluminum alloys which contain more aluminum than the eutectic with the alloy partners corresponds to in order to achieve improved strength values by reducing the distances between the dendrite arm distances formed by solidification.
  • the technological properties of the aluminum alloys in particular the strength, the yield strength and the elongation, can be improved by fine-grain of the casting.
  • the strength properties of aluminum alloys are directly dependent on the number and fineness of the smallest possible dendrite arm spacing - the secondary dendrite arm spacing. According to Foundry, June 1963, pp. 78-82, the fine-grained nature of aluminum and aluminum-based alloys is improved by adding a pre-alloy to the aluminum alloy before casting, which is used as heterogeneous nuclei e.g. Contains titanium diboride.
  • the refractory material for dipping is added in the same way as the step just mentioned as germs, noble metals or reducible metal oxides.
  • the US-PS 3 157 926 works in the same way and names nickel-III-oxide, cobalt-II-oxide and -III-oxide and nickel-cobalt oxyhydrate as seeds.
  • the seeds of the above-mentioned US patents are not effective for reducing the secondary dendrite arm spacings and thus for improving the strength properties of hypoeutectic aluminum alloys and are not proposed by the US patents. No suitable seeds have yet been found for aluminum base melts, which are suitable for embedding in the mold wall to produce a fine-grained casting.
  • DE-PS 963 642 teaches to influence the surface of castings by adding additives to the molding material and alloys the surface with lead released by chemical reaction with the casting metal.
  • protective materials which reduce the molding material are added according to DE-AS 12 71 909, the melting point of which lies between the casting temperature and the firing temperature of the casting mold.
  • DE-AS 12 65 356 discloses to add a hydrogen-releasing metal hydride to the casting mold in its mold cavity.
  • the hydrogen is said to be the oxide skin of e.g. Reduce incoming iron as a casting material and thus increase the flowability.
  • the aluminum oxide of the cast skin of aluminum cannot be reduced with hydrogen.
  • the presence of hydrogen when aluminum alloys are cast is also highly undesirable because gas bubbles form.
  • German cited documents only disclose that the surface of the casting can be influenced by means of substances introduced into the mold.
  • the object is achieved in a method of the type mentioned in that the inner wall of the mold is produced with numerous roughness in the micro range, that the inner wall is provided with a thin layer of a salt mixture, the cations of the salt mixture predominantly from those of the alkali and / or alkaline earth metals and their anions consist predominantly of those of the halogens, and that the liquidus temperature of the salt mixture is set lower than the casting temperature of the aluminum alloy.
  • the transport of broken dendrite arms through the melt into central areas of the casting in addition to the growth of the fine dendritic solidification front, further improves the fine-grained interior or also the area of the inner mold wall, which is not very effective, with a sufficient number of species Germs supplied.
  • the ceramic shape the roughness and pores after drying and firing are provided with the thin salt layer, the liquidus temperature of which is lower than the casting temperature of the alloy, the salt mixture as a thin, film-like layer, which liquefies when the alloy is poured, evenly into the depressions of the alloy Spread roughness and does not prevent the cast aluminum from penetrating into the pores due to the thin layer.
  • the salts whose cations predominantly consist of alkali and / or alkaline earth and whose anions consist predominantly of halogens reliably bring about a reduction in the dendrite arm distances.
  • the invention can be advantageously configured as follows.
  • the invention recommends producing as many, but more than 10 5 roughnesses per cm 2 of the mold inner wall, the ratio of depth to diameter or depth to gap width of cracks of which is greater than 1 to 3. Roughness in the form of pores, fracture edges, cracks and crevices and, preferably, funnel-shaped depressions formed by sequences of microcrystalline fracture edges, which face the casting with the enlarging opening, are recommended.
  • Geometrically particularly favorable roughnesses are e.g. obtained by arranging a ceramic material which tends to break the shell in particularly finely ground grains with a diameter of predominantly less than 10 ⁇ m on the inner wall of the mold. This happens e.g. by "dipping", i.e. Dipping the wax model in a slip on an aqueous or alcoholic basis, which also contains a binder, e.g. based on silicon dioxide. It is also possible to use other ceramic powders which have suitable pore sizes and / or a suitable fine grain because of the way in which they are produced.
  • the salt mixture additionally contains one or more alkali and / or alkaline earth pseudohalogen compounds or also organic salts of the alkali and / or alkaline earth metals, an improved removal of oxygen residues, in particular in the pores of the mold, can be achieved.
  • Suitable alkali or alkaline earth pseudohalogen compounds are cyanate, cyanide, rhodanite, hexa- or tetracyano compounds, amines or amides or the like, the atkaticyanides, cyanates and rhodanides chemically related compounds.
  • the removal of oxygen radicals is effective not only in casting in air, but also for casting in a vacuum at about 10 -2 Torr.
  • this additional salt in about 2-40% by weight of the total salt mixture.
  • the amount of salt added is expediently limited in such a way that the gas released during casting does not form bubbles on the surface of the casting, the released gas does not contain any molecular hydrogen and, furthermore, the salt is not stable under the pressure and temperature conditions of the preheating of the mold shell Has hydrates.
  • the inner wall and its pore entrances can be provided with different salts simultaneously and in an even, finest distribution and also apply finely ground, slurried salts that are insoluble or insufficiently soluble to the inner wall.
  • the intimate mixture of the various salts leads to rapid liquefaction.
  • the preheating of the mold which takes place before the casting, in order to improve the flow of the casting, serves at the same time to dry the applied salts. Water and / or alcohol are suitable as solvents.
  • salt mixture consisting predominantly of sodium-lithium chloride fluoride is used to coat the inner wall of the ceramic mold, the melting point of which is below 650 ° C., enables the salt mixture to be liquefied very quickly.
  • these salt mixtures there are deep-melting mixtures of reciprocal salt pairs with low hydrostability of the individual salts, especially when compared to the salts of potassium.
  • An aqueous and / or alcoholic solution of LiCl, NaF, NaCl and Na 4 Fe (CN) e is particularly suitable. No premelting and grinding of the salt mixture is necessary.
  • Sodium fluoride is water soluble. Due to ion exchange with the lithium chloride, fine-grained lithium fluoride precipitates after a few hours.
  • the solution and / or slurry of the salt mixture contains a dispersing agent, fine-grained insoluble salts which separate out from the solution after some time, such as lithium fluoride, can be kept in suspension and a uniform distribution of the salt mixture on the inner wall of the mold can be promoted.
  • Suitable dispersants are e.g. Methyl cellulose.
  • the wax grapes were given a first coating by dipping into a slurry consisting of an aqueous binder, finely ground ( ⁇ 30 11 m) zirconium silicate and silicon dioxide as filler and sanded with coarse zirconium silicate powder. After drying, a further six layers were used up by dipping, sanding and drying in the usual way, so that ceramic molds with wall thicknesses of approximately 8 mm were formed. The molds were waxed under pressure in an autoclave and then fired at approx. 800 ° C.
  • the solution was poured into the ceramic molds one after the other, immediately poured out again and filtered in order to remove any ceramic granules that had been rinsed out.
  • the ceramic molds were then heated to about 470 ° C, used in the warm state in the vacuum casting, and at about 250 ° C mold temperature with the aluminum alloy GAISi7Mg0.6 at a melt temperature of 700 ° C at 10- 2 Torr filled.
  • the aluminum melt was premelted in air, then degassed with a flushing gas mixture and then degassed in vacuo.
  • the wax models of an aircraft structural part with an average wall thickness of 5 mm and at the nodes with a wall thickness of 15 mm were assembled into wax grapes according to the method described in exemplary embodiment 1, covered with the ceramic shell, waxed under pressure in the autoclave and then at approx. Fired at 800 ° C.
  • the solution was poured into the ceramic molds one after the other, immediately poured out again and filtered in order to remove any ceramic granules that had been rinsed out.
  • the ceramic molds were then heated to approx. 470 ° C, inserted into the vacuum casting machine when hot and at approx. 250 ° C mold temperature with the aluminum alloy GAISi7MgO, 6 at a melt temperature of 700 ° C, at 10- 2 Torr filled.
  • the aluminum melt was premelted in air, then degassed with a purging gas mixture and subsequently degassed in vacuo.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Mold Materials And Core Materials (AREA)

Claims (9)

1. Procédé pour couler des alliages d'aluminium contenant plus d'aluminium que l'eutectique avec les composants alliés, en vue de parvenir à des valeurs améliorées de résistance mécanique par diminution des distances entre les branches de dendrites de formation secondaire par solidification, caractérisé par le fait qu'on pratique de nombreuses irrégularités de surface, d'ordre microscopique, sur la paroi intérieure du moule de coulée, on applique sur la paroi intérieure une couche mince d'un mélange de sels dont les cations consistent principalement en ceux des métaux alcalins et/ou alcalini-terreux et les anions consistent principalement en ceux des halogènes, et que la température de liquidus du mélange de sels est réglée plus bas que la température de coulée de l'alliage d'aluminium.
2. Procédé selon la revendication 1, caractérisé par le fait que la paroi intérieure du moule de coulée porte plus de 105 irrégularités de surface par cm2, dont le rapport, profondeur/diamètre ou profondeur/ largeur de fente, est supérieur à 1:3.
3. Procédé selon la revendication 2, caractérisé par le fait que la matière réfractaire constituant la paroi intérieure du moule de coulée est préparée, à partir de poudres d'oxyde en grains extrêmement fins obtenues par broyage, par immersion d'un modèle de cire dans une dispersion consistant en la poudre d'oyxde, une charge et un liant, séchage et calcination avec formation d'une liaison d'oxyde céramique par le liant.
4. Procédé selon l'une des revendications qui précèdent, caractérisé par le fait que le mélange de sels utilisés contient en outre un ou plusieurs composés de métaux alcalins et/ou alcalino-terreux et de pseudo- halogènes sous forme de cyanates, de cyanures, de thiocyanates, de composés hexa- et/ou tétra-cyanés, d'amines ou d'amidures et/ou de composés analogues, apparentés chimiquement aux cyanures, cyanates et thiocyanates de métaux alcalins, et/ou des sels organiques et/ou des composés organo-métalliques des métaux alcalins et/ou alcalino-terreux.
5. Procédé selon l'une des revendications qui précèdent, caractérisé par le fait que l'on utilise pour le revêtement de la paroi intérieure du moule céramique un mélange de sels consistant principalement en chlorurefluorure de sodium-lithium et dont le point de fusion est inférieur à 650°C.
6. Procédé selon la revendication 5, caractérisé par le fait que l'on utilise une solution aqueuse et/ou alcoolique de LiCI, NaF, NaCI et Na4Fe(CN)6.
7. Procédé selon l'une quelconque des revendications qui précèdent, caractérisé par le fait que le mélange de sels est appliqué à l'état de solution et/ou de fine suspension par coulée et évacuation dans le moule cuit, sur sa paroi intérieure, en faisant suivre d'un séchage.
8. Procédé selon la revendication 7, caractérisé par le fait que la solution et/ou suspension du mélange de sels contient un agent dispersant, par example de la méthylcellulose.
9. Procédé selon l'une des revendications qui précèdent, caractérisé par le fait que l'on ajoute à la solution et/ou suspension du mélange de sels un produit auxiliaire améliorant le mouillage de la paroi intérieure du moule céramique, par exemple un agent tension-actif.
EP86104247A 1985-04-03 1986-03-27 Procédé pour la coulée d'alliages d'aluminium Expired - Lifetime EP0198290B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19853512118 DE3512118A1 (de) 1985-04-03 1985-04-03 Verfahren zur erzeugung einer verbesserten feinkoernigkeit des primaergefueges und/oder des eutektikums von gussteilen
DE3512118 1985-04-03

Publications (3)

Publication Number Publication Date
EP0198290A2 EP0198290A2 (fr) 1986-10-22
EP0198290A3 EP0198290A3 (en) 1987-06-24
EP0198290B1 true EP0198290B1 (fr) 1990-05-30

Family

ID=6267164

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86104247A Expired - Lifetime EP0198290B1 (fr) 1985-04-03 1986-03-27 Procédé pour la coulée d'alliages d'aluminium

Country Status (9)

Country Link
EP (1) EP0198290B1 (fr)
JP (1) JPS61293653A (fr)
BR (1) BR8601478A (fr)
CA (1) CA1288210C (fr)
DE (2) DE3512118A1 (fr)
ES (1) ES8703097A1 (fr)
IL (1) IL78279A0 (fr)
SU (1) SU1760973A3 (fr)
ZA (1) ZA862393B (fr)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3703416A1 (de) * 1987-02-05 1988-08-18 Thyssen Guss Ag Feingussschalenform fuer aluminium bzw. dessen legierungen
DE3821204A1 (de) * 1988-06-23 1989-12-28 Winkelstroeter Dentaurum Impfmittelmischung zur beschichtung von gussformen fuer die herstellung von dentalgussskeletten
DE4308614A1 (de) * 1993-03-18 1994-09-22 Fritz Winter Eisengieserei Ohg Verfahren zur Herstellung von Werkstücken aus Gußeisen und danach hergestellte hohle Gußstücke
GB9618216D0 (en) * 1996-08-30 1996-10-09 Triplex Lloyd Plc Method of making fine grained castings
FR2935275B1 (fr) * 2008-08-29 2011-11-04 Peugeot Citroen Automobiles Sa Procede de moulage a modele perdu, modele perdu pour ce procede
CN108778557B (zh) * 2015-12-18 2020-03-06 亚世科化学有限责任公司 用于非铁金属铸造的造型材料

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE963642C (de) * 1944-09-30 1957-05-09 Siemens Ag Verfahren zur Beeinflussung der Oberflaeche von Gusskoerpern
US3259948A (en) * 1962-04-09 1966-07-12 Howe Sound Co Making fine grained castings
GB1076179A (en) * 1963-11-19 1967-07-19 Erik Rune Albin Larsson A method for casting steel and steel alloys
US3157926A (en) * 1964-02-14 1964-11-24 Howe Sound Co Making fine grained castings
DE1265356B (de) * 1965-02-26 1968-04-04 Henry H Harris Giessform
NL126286C (fr) * 1965-07-29

Also Published As

Publication number Publication date
BR8601478A (pt) 1986-12-09
JPS61293653A (ja) 1986-12-24
ES8703097A1 (es) 1987-02-16
ZA862393B (en) 1986-11-26
DE3512118A1 (de) 1986-10-16
IL78279A0 (en) 1986-07-31
SU1760973A3 (ru) 1992-09-07
DE3671607D1 (de) 1990-07-05
ES553681A0 (es) 1987-02-16
EP0198290A2 (fr) 1986-10-22
EP0198290A3 (en) 1987-06-24
CA1288210C (fr) 1991-09-03

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