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
  • C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
  • C22B9/10—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals with refining or fluxing agents; Use of materials therefor, e.g. slagging or scorifying agents
• • 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
• • 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
  • C22B21/062—Obtaining aluminium refining using salt or fluxing agents

Definitions

• the invention relates to the use of a binary salt flux comprising NaCI and MgCI 2 for the purification of a metal selected from the group consisting of aluminum and aluminum alloys, more particularly for the removal of alkali and alkaline-earth metals.
• the invention also relates to a method for the purification of said metal with said binary salt flux.
• Fluxes can be used to form a protecting layer at the surface of an alloy to prevent oxidation.
• fluxes contain chemical active agents, they can be used to clean furnace walls by softening accumulated layers of corundum. Some exothermic fluxes are also used for cleaning dross and removing aluminum trapped in oxide layers.
• Fluxes that are based on alkali chlorides and alkaline-earth chlorides are also used for the refining of alloys. Those skilled in the art generally define refining as the removal of alkali and alkaline-earth metals, non metallic inclusions and hydrogen from the alloys.
• Sodium and calcium are always present as impurities in aluminum obtained from the Hall-Heroult process. Lithium fluoride is often added to the electrolytic bath to improve the efficiency of cells. However, a small amount in the metallic state is found dissolved in the aluminum. These impurities entail quality issues. For example, in an alloy containing magnesium, the presence of sodium may interfere during the hot rolling processes. The presence of sodium in aluminum and silicon alloys neutralize the effect of phosphorus used for the refining of grains. For the above- mentioned reasons, the use of fluxes containing sodium is not recommended for aluminum and its alloys, more particularly for aluminum alloys comprising a magnesium content higher than 3 % by weight or a silicon content higher than 10 % by weight.
• the presence of hydrogen in too high concentration may lead to a too high porosity of the aluminum during its solidification.
• the presence of non metallic inclusions is important.
• MgCI 2 is one of the chemical active agents used for the withdrawal of impurities in alloys. Its concentration has a direct effect on the kinetic of withdrawal of calcium and sodium. Its melting point is 714°C, but in common fluxes, it is mixed with other salts to obtain a melting point between 400 and 550 0 C. However, MgCI 2 is hygroscopic and can not be exposed for a long period of time to the surrounding air. Fluxes obtained by fusion of salts comprising magnesium chloride have hygroscopic properties. Consequently, the packaging is an important factor in limiting the absorption of humidity during the manufacturing of such fluxes.
• US patent no. 1 ,377,374 relates to the use of a flux having an equimolar composition of sodium chloride and magnesium chloride for the production of manganese or magnesium alloys.
• US patent no. 1 ,754,788 relates to the use of this same flux in a process for the cleaning of magnesium.
• US patent no. 1 ,519,128 relates to the addition of calcium chloride to this composition and
• US patent no. 2,262,105 relates to the addition of potassium chloride and magnesium oxide in addition to the calcium chloride.
• US patent no. 5,405,427 mentions a flux based on sodium chloride, magnesium chloride, potassium chloride and carbon for the treatment of metal.
• the refining fluxes are usually composed of alkali chlorides or alkaline-earth chlorides, which are mixed to obtain melting points that are lower than the operating temperature of alloys - the melting point of pure compounds being usually quite high.
• US patent no. 4,099,965 relates to a method where a flux of KCI and MgCI 2 is added in solid form in the bottom of a preheated container before the addition of aluminum. More currently, fluxes are added by an inert gas in a pipe under the surface of the metal (lance fluxing). Recently, a method was developed where a hollow shaft brings the salt flux in the alloy with a gas carrier, and the salt flux is dispersed by an agitator (rotary flux injection). This method reduces the amount of salt flux required for carrying out the purification while increasing the dispersion of this salt flux in the alloy. Following the addition of a salt flux to the metal, impurities and salts float on the surface of the liquid metal and can be easily removed.
• the use of solid compounds obtained by melting of salts controls the granulometry.
• Particles may be used in batch processes or in continuous processes.
• salt fluxes such as binary mixtures of magnesium chloride and potassium chloride
• costs related to salt fluxes are high.
• the use of salt fluxes having a substantial content in sodium chloride is not recommended by those skilled in the art due to perceived negative effects of sodium content in the resulting aluminum or aluminum alloys.
• sodium chloride when sodium chloride is present in fluxes for the purification of aluminum or aluminum alloys, those skilled in the art currently will avoid or limit the use of sodium chloride. More particularly, in the case of certain kinds of alloys such as, for example, aluminum alloys having silicon content higher than 10% by weight and more particularly aluminum alloys having magnesium content higher than 3% by weight, those skilled in the art currently recommend not using sodium chloride in salt flux.
• Embodiments of the present invention show the following advantages:
• a first preferred aspect of the invention relates to the use of a salt flux for the purification of a metal selected from the group consisting of aluminum and aluminum alloys, said metal being in liquid phase and said salt flux being a binary mixture of NaCI and MgCI 2 .
• a second preferred aspect of the invention relates to a method for the purification of a metal selected from the group consisting of aluminum and aluminum alloys, wherein said method comprises:
• Another embodiment of the invention relates to a use or a method as defined hereinabove, wherein more than 22 % by weight of said binary mixture consists of NaCI.
• Another embodiment of the invention relates to a use or a method as defined hereinabove, wherein the salt flux:
• • is a binary mixture of particles of NaCI and particles of MgCI 2 ;
• Another embodiment of the invention relates to a use or a method as defined in any one of the above-mentioned embodiments, wherein the binary mixture comprises: a) from 40 to 50% by weight of NaCI; and b) from 50 to 60% by weight of MgCI 2 . More particularly, this binary mixture comprises 45% by weight of NaCI and 55% by weight of MgCI 2 to form an eutectic mixture having a melting point of about 439°C.
• Another embodiment of the invention relates to a use or a method as defined in any one of the above-mentioned embodiments, wherein when the salt flux is in the form of particles, those particles have an average particle size between 100 ⁇ m and 3.35 mm.
• said particles may have a particle size between 0.85 mm and 3.15 mm or between 100 ⁇ m and 1 mm.
• Another embodiment of the invention relates to a use or a method as defined in any one of the above-mentioned embodiments, wherein the particles are contacted with the liquid metal by injection with a gas injection equipment.
• a gas injection equipment may consist of a rotary injector known under the tradename SNIF PHD-50 commercialized by the Applicant.
• Another embodiment of the invention relates to a use or a method as defined in any one of the above-mentioned embodiments, wherein the metal is an aluminum alloy having a magnesium content higher than 3% by weight.
• Another embodiment of the invention relates to a use or a method as defined in any one of the above-mentioned embodiments, wherein the metal is an aluminum alloy having a silicon content higher than 10% by weight.
• Figure 1 a phase diagram of a fused salt KCI/NaCI/MgCI 2 ;
• Figure 4 a comparative graphic concerning examples 5 to 8.
• Formulations based on NaCI and MgCI 2 proposed according to the present invention show melting points that are lower than those of salt flux compositions sold by the Applicant under the trademark Promag (40 wt % KCI, 60 wt % MgCI 2 ), for equivalent amounts of MgCI 2 which is the chemically active agent for the withdrawal of impurities.
• the lowering of melting points represents a lowering of energy costs when melting the solid salt flux.
• example 1 illustrates an unexpected effect with regard to the sodium concentration in an aluminum alloy when NaCI is added in a liquid aluminum alloy, that is, no increase of the sodium content in the alloy obtained.
• each salt flux was made by mixing the salts in an anhydrous solid phase in an appropriate oven. Then, by increasing the temperature of the oven, a fused compound in liquid form was obtained. The liquid was then cooled down quickly, grinded and sifted to obtain a granulometry that was appropriate for the selected method.
• the salt flux was made only by mixing the salts in an anhydrous solid phase.
• Salt fluxes have shown an optimal efficiency for the withdrawal of Ca, Na and Li when used with a rotary injector such as a SNIF PHD-50 (tradename) commercialized by the Applicant (Pyrotek).
• a rotary injector such as a SNIF PHD-50 (tradename) commercialized by the Applicant (Pyrotek).
• concentrations of salt fluxes required to carry out the purification may vary depending on the selected method.
• a salt flux consisting of a binary mixture of 45 wt % NaCI and 55 wt % MgCI 2 were agitated in 1.5 kg of a liquid AA1100 aluminum alloy (sold under the trademark Alcan) in which 5 wt % of magnesium were added.
• the crucible was maintained at 72O 0 C during 90 minutes and samples were taken every 30 minutes.
• the sodium level in the crucible was maintained at a minimal level of 3 ppm during the whole experiment, showing that an addition of a flux comprising NaCI does not involve an absorption of sodium in an aluminum alloy with high magnesium content.
• the salt flux was prepared from NaCI in powder form and sold under the trademark SIFTO INDUSTRIAL and MgCI 2 in flake form and sold under the trademark SKYLINE.
• a salt flux consisting of a ternary mixture of 20 wt % NaCI, 20 wt % KCI and 60 wt % MgCI 2 were agitated and added in 1.5 kg of a liquid AA1100 aluminum alloy (sold under the trademark Alcan) in which 5 wt % of magnesium were added.
• the crucible was maintained at 720 0 C during 90 minutes and samples were taken every 30 minutes.
• the sodium level in the crucible was maintained at a minimal level of 3 ppm during the whole experiment, showing that an addition of a ternary flux comprising a small amount of NaCI does not involve an absorption of sodium in an aluminum alloy with high magnesium content.
• the salt flux was prepared from NaCI in powder form and sold under the trademark SIFTO INDUSTRIAL, KCI in powder form and sold under the trademark IMC KALIUM and MgCI 2 in flake form and sold under the trademark SKYLINE.
• Example 4 Example 4:
• salt flux made of 45 wt % NaCI and 55 wt % MgCI 2 were added to the resulting alloy while agitating it in order to further purify it.
• the salt flux was prepared from NaCI in powder form and sold under the trademark SIFTO INDUSTRIAL and MgCI 2 in flake form and sold under the trademark SKYLINE.
• the liquid mixture obtained was then poured into an enamelled-coated bowl for quick solidification.
• the salt flux obtained was then grinded with in a mortar and sifted.
• a salt flux Fifty grams of a salt flux were prepared in a small alumina crucible by mixing 10 grams of NaCI in powder form and sold under the trademark SIFTO INDUSTRIAL, 10 grams of KCI in powder form and sold under the trademark IMC KALIUM, and 30 grams of MgCI 2 in flake form and sold under the trademark SKYLINE. The mixture was subjected to a temperature of 55O 0 C during 45 minutes. The liquid mixture obtained was then poured into an enamelled-coated bowl for quick solidification. The salt flux obtained was then grinded in a mortar and sifted. The fraction having a particle size lower than 3150 microns and higher than 105 microns was recovered.
• Fifty grams of a salt flux were prepared only by mixing 22.5 grams of NaCI in powder form and sold under the trademark SIFTO INDUSTRIAL with a granulometry 95% lower than 840 microns and 95 % higher than 300 microns, and 27.5 grams of MgCI 2 in flake form and sold under the trademark SKYLINE with a granulometry 90 % lower than 4.7 mm and 85 % higher to 1 mm.
• PROMAG SI (trademark) formed of 40 wt % KCI and 60 wt % MgCI 2 , with a granulometry 99% lower than 3150 microns and 95 % higher than 850 microns, were added to the alloy doped with calcium while agitating for 2 minutes. The agitation was stopped and samples were later taken immediately after the end of the agitation as well as 30, 60 and 90 minutes later.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Manufacture Of Metal Powder And Suspensions Thereof (AREA)

Priority Applications (7)

Applications Claiming Priority (2)

Publications (1)

Family

ID=43308339

Family Applications (1)

Country Status (9)

Cited By (4)

Families Citing this family (7)

Citations (10)

Family Cites Families (8)

• 2009
  • 2009-06-08 CA CA2668473A patent/CA2668473C/en active Active
• 2010
  • 2010-06-08 JP JP2012514304A patent/JP2012529565A/ja active Pending
  • 2010-06-08 AU AU2010258042A patent/AU2010258042B2/en active Active
  • 2010-06-08 CN CN201080025076XA patent/CN102459663A/zh active Pending
  • 2010-06-08 BR BRPI1015440A patent/BRPI1015440A2/pt not_active IP Right Cessation
  • 2010-06-08 EP EP10785623.9A patent/EP2446065B2/en active Active
  • 2010-06-08 ES ES10785623T patent/ES2862528T5/es active Active
  • 2010-06-08 RU RU2011147513/02A patent/RU2011147513A/ru not_active Application Discontinuation
  • 2010-06-08 WO PCT/CA2010/000866 patent/WO2010142025A1/en not_active Ceased

Patent Citations (10)

Non-Patent Citations (3)

Also Published As

Similar Documents

Legal Events