Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B21/00—Obtaining aluminium
  • C22B21/06—Obtaining aluminium refining

Definitions

• the present invention relates to a process for obtaining very high purity aluminum in eutectic elements by segregation.
• eutectic elements such as copper, iron, magnesium, silicon, zinc in aluminum of current purity when these are in hypoeutectic concentration.
• eutectic elements such as copper, iron, magnesium, silicon, zinc in aluminum of current purity when these are in hypoeutectic concentration.
• These crystals collect by gravity at the bottom of the container as they are formed and, by compacting them, a more or less compact purified solid is obtained, the purity of which tends to decrease as a function of the crystallized mass.
• the operation is generally continued until only a small fraction of the mother liquor remains.
• the purified mass can be separated from the remaining mother liquor or even the purified basket can be separated into. several fractions of different purity.
• the efficiency of the purification generally results in the value of the purification coefficient C / C, where C is the concentration of a given impurity in the pure product obtained, and C O is the concentration of the same impurity in the metal put in artwork.
• C is the concentration of a given impurity in the pure product obtained
• C O is the concentration of the same impurity in the metal put in artwork. The higher this coefficient, the better the effectiveness of the treatment.
• This process for obtaining very high purity aluminum in eutectic elements consists in subjecting an already very pure aluminum to a segregation operation, but characterized in that the molten metal is added, before the segregation operation, and in order to make it more effective, at least one eutectic element in hypoeutectic quantity which either is eliminated very completely during this operation, or remains in the purified product at a non-annoying content for the intended use.
• the process of the invention uses an aluminum already very pure, for example which has already undergone a first purification which has made it possible to bring its content of total impurities to 200, and even up to 100 ppm or less.
• This aluminum may for example have a content of each of the iron and silicon elements close to 50 ppm, but contents higher or lower than this value in any of the impurities are also possible.
• This first purification can be obtained for example by a segregation operation identical to that described in the French patent cited above.
• the starting metal may also have been subjected to a treatment to remove peritectic impurities such as titanium and vanadium for example.
• Such a metal is then melted and at least one eutectic element is added to the liquid, in the absence of any crystallization.
• This element is preferably chosen from the group consisting of iron and copper, but the simultaneous addition of these two elements can also be envisaged. What is important is that this element should not have an embarrassing concentration after the final operation of segregation.
• iron can be added whose coefficient is close to 30.
• copper can be used whose coefficient is close to 7 but which, up to contents of 50 ppm, is not not annoying in certain applications and can even be beneficial in the case where aluminum is intended for the manufacture of electrolytic capacitors of medium and high voltage. We can obviously add these two elements simultaneously.
• the amount added must obviously be such that the concentration of the liquid in this element before crystallization is lower than that of the eutectic, otherwise, as indicated by the liquid-solid equilibrium diagrams, the crystals obtained will first be more unclean as the initial mother liquid, then there will be a deposit of crystals of eutectic composition and there will therefore be no possible purification.
• additions should also not be too small, otherwise the effect of the addition will not meet the objective sought, namely to avoid mass crystallization which does not allow proper operation.
• additions will depend on the element added and the intended application for the purified metal. For example, in the case of iron, additions of about 100 to 200 ppm, or even 500 ppm, are suitable. However, in the case of copper, they can go beyond 100 ppm and reach 2000 ppm if the aluminum is intended, for example, for the manufacture of capacitors.
• the addition of the eutectic element can be done either in the solid state or in the liquid state and in any suitable form such as pure element, alloy of the elements or master alloy based on aluminum.
• the homogeneity of the liquid after addition is achieved by any suitable stirring or stirring means.
• an aluminum is used containing approximately 20 ppm of silicon and 15 ppm of iron obtained by a first purification operation by segregation. If we add 200 ppm of iron to it and subject it to a new segregation operation, we see that we can bring the silicon to around 5 ppm. As, moreover, the purification coefficient of iron is significantly higher than that of silicon, the fact that iron has been added does not degrade the quality of the final product but, on the contrary, leads to a content close to that silicon and this, with a yield of the order of 70%.
• the present invention finds its application in particular in obtaining aluminum of very high purity in eutectic elements and containing in particular less than 10 ppm of iron and silicon and intended in particular for the manufacture of high and medium voltage capacitors.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Manufacturing & Machinery (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Semiconductor Integrated Circuits (AREA)
• Analysing Materials By The Use Of Radiation (AREA)
• Powder Metallurgy (AREA)
• Superconductors And Manufacturing Methods Therefor (AREA)
• Light Receiving Elements (AREA)
• Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

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Cited By (1)

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Citations (10)

Family Cites Families (5)

• 1982
  • 1982-03-31 FR FR8205895A patent/FR2524490B1/fr not_active Expired
• 1983
  • 1983-03-23 CA CA000424280A patent/CA1185436A/fr not_active Expired
  • 1983-03-23 GR GR70880A patent/GR77984B/el unknown
  • 1983-03-24 IN IN355/CAL/83A patent/IN158047B/en unknown
  • 1983-03-24 NZ NZ203683A patent/NZ203683A/en unknown
  • 1983-03-24 DE DE8383420054T patent/DE3365393D1/de not_active Expired
  • 1983-03-24 EP EP83420054A patent/EP0090750B1/de not_active Expired
  • 1983-03-24 IS IS2793A patent/IS1353B6/is unknown
  • 1983-03-24 AT AT83420054T patent/ATE21529T1/de not_active IP Right Cessation
  • 1983-03-25 US US06/478,785 patent/US4444585A/en not_active Expired - Lifetime
  • 1983-03-25 ES ES521015A patent/ES521015A0/es active Granted
  • 1983-03-28 BR BR8301579A patent/BR8301579A/pt not_active IP Right Cessation
  • 1983-03-29 JP JP58053461A patent/JPS58181835A/ja active Granted
  • 1983-03-30 ZA ZA832267A patent/ZA832267B/xx unknown
  • 1983-03-30 NO NO831192A patent/NO160793C/no unknown
  • 1983-03-30 AU AU12998/83A patent/AU551209B2/en not_active Ceased
  • 1983-03-31 KR KR1019830001326A patent/KR860001306B1/ko not_active Expired

Patent Citations (10)

Non-Patent Citations (1)

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