Title of Invention	A PROCESS FOR THE MANUFACTURE OF GRANULAR FLUX FOR ADDITION TO MOLTEN ALUMINIUM AND ITS ALLOYS
Abstract	This invention relates to a process for the manufacture of granular flux for addition to molten aluminium and its alloys. The salts used are particle resources of commercial grade purity; sodium chloride (NaCI 70.00 to 80.00 Wt %,), potassium cWoride (KCII0.00 -15.00 wt %,), sodium carbonate (N~ CO35.00-15.00 wt %) and sodium fluoride (NaF 5.00-15.00 wt%). Appropriate quantities of the salt powders are dried thoroughly and are melted in a particular sequence in a suitable melting furnace. The molten salt mixture is held at 730 to 750 degree Celsius and are held in the molten state for 15 minutes. After alloying of the salt mixture takes place, the material is poured from thermal furnace and allowed to cool to room temperature. Subsequent to cooling, the solid solution of salts is weighed. The solid is further processed by grinding and sieving, to obtain particles of different sizes, selected grades are weighed, thoroughly mixed and stored in plastic bags or plastic containers for addition to molten aluminium and its alloys.

Title of Invention

A PROCESS FOR THE MANUFACTURE OF GRANULAR FLUX FOR ADDITION TO MOLTEN ALUMINIUM AND ITS ALLOYS

Abstract

This invention relates to a process for the manufacture of granular flux for addition to molten aluminium and its alloys. The salts used are particle resources of commercial grade purity; sodium chloride (NaCI 70.00 to 80.00 Wt %,), potassium cWoride (KCII0.00 -15.00 wt %,), sodium carbonate (N~ CO35.00-15.00 wt %) and sodium fluoride (NaF 5.00-15.00 wt%). Appropriate quantities of the salt powders are dried thoroughly and are melted in a particular sequence in a suitable melting furnace. The molten salt mixture is held at 730 to 750 degree Celsius and are held in the molten state for 15 minutes. After alloying of the salt mixture takes place, the material is poured from thermal furnace and allowed to cool to room temperature. Subsequent to cooling, the solid solution of salts is weighed. The solid is further processed by grinding and sieving, to obtain particles of different sizes, selected grades are weighed, thoroughly mixed and stored in plastic bags or plastic containers for addition to molten aluminium and its alloys.

Full Text	This invention relates to a process for the manufacture of granular flux for addition to molten aluminium and its alloys. The processing of aluminium is divided into primary and secondary industries. For energy savings and economy, much aluminium ingot is alloyed and cast at smelting plants using primary metal (which is produced by direct-current electrolysis of molten Alumina dissolved in molten sodium fluoride-aluminium fluoride bath at 940-980 °C; Hall-Heroult Process) while still molten. Secondary aluminium is recovered from scrap, is on of the important contributors to the tota metal supply. New scrap is defined as that generated by plants making end products, where as old scrap is that recovered metal which has been previously used by consumers which is being recycled. The furnace charge may be made up of any one or combination of the retuned gates, risers, pre-alloyed ingots, prmary metal together with, alloying elements or molten metal. Molten aluminium/ its alloys are extremely reactive and combine readily with other metals, with gases and some times with refractories. Aluminium is readily oxidized metal and the reaction proceeds as per the equation-1 given below: The oxide formed is both adherent and relatively impermeable so that the initial film formed is of the order of 0.01 \im on first formation and may grow up to 0.4 \im on metal which has been given a normal muffle anneal at say 400°C. Surface tension of molten aluminium is very high, and when augmented by the formation of a film of oxide, surface tension is so great that it causes difficulty in casting thin sections. However, the surface tension of molten aluminium is great enough to keep a charge of fines floating on top of the molten bath. In aluminium melting, especially in re-melting of foundry returns or other scrap, oxide formation and non-metallic impurities are common. Impurities appear in the form of liquid and solid inclusions, persist through melt solidification into the casting. Inclusions can originate from dirty tools, sand and other molding debris, sludge (iron-chromium-nickel intermetallic compounds commonly found in the die casting alloys), metal working lubricants, and the oxidation of alloying elements and /or the base metal. For the purpose of clarity and to avoid ambiguity, a few of the technical terms used in the specification are defined here to mean as under. DROSSING is the formation of aluminium oxide and other oxides, which accumulate on the melt surface. COMMERCIAL GRADE CHEMICALS: Salts that are available, which have higher impurities than those of laboratory grade salts. Alloying of the salt mixture: Mixtures of alkaline and alkaline earth metal salts more particularly chlorides, fluorides, carbonates, such as sodium chloride, potassium chloride, magnesium chloride, potassium fluoride, sodium fluoride, sodium carbonate, and which are melted to form a homogeneous solution, which is then cooled to room temperature. YIELD: Ratio of the weight (W2) of the cooled solid solution of the salts (namely mixtures of alkaline and alkaline earth metal salts more particularly chlorides, fluorides, carbonates, such as sodium chloride, potassium chloride, potassium fluoride, sodium fluoride, sodium carbonate, calcium caibonate, and alkaline alumino-fluorides) to the weight (Wi) of the powder salt mixture (before melting) multiplied by 100 Aluminium: LMO Aluminium Alloys LMS,LM6, LM9, LM13,LM 20,LM2S Complete separation of dross and metal would be favored by large differences in their specific gravities. However, the specific gravities of the oxides and molten metal i.e. aluminium are of similar magnitude as given in table (1). Oxides of aluminium and magnesium form quickly on the surface of the molten metal bath, making a thin tenacious skin that prevents further oxidation as long as the surface is not disturbed. Molten aluminium also reacts with moisture to form aluminium oxide realizing hydrogen. Moisture on charge materials, tools, fluxes and refractories causes rapid oxidation of the metal. Agitation of the molten bath results in suspension of the surface oxide skin in the molten metal. The densities of the oxides are nearly same as that of the molten metal and thus the oxides are likely to be carried into the castings. Fluxing of the melt facilitates the agglomeration and separation of such undesirable constituents from the melt. Certain flux compositions have been used for years, not because they have special merits, but rather because of tradition. The intelligent use of a flux requires detailed knowledge of the chemical and physical relationships between (1) metal and flux (2) foreign matter and flux and (3) metal and foreign matter. The dissolution of aluminium oxide, dirt or other coating on the globules of liquid metal is a necessary attribute of a flux. Coalescence of globules cannot take place unless the coating is ruptured. It would appear that the oxide coating might more easily and thoroughly be removed by chemical rather than mechanical means. An important attribute of a flux is the power to reduce the surface tension of the globules there by promoting the coalescence of metal globules that is increasing the fluidity. Fluxes, which dissolve aluminium oxide by chemical action, contain fluoride salts, which dissolve aluminium oxide, in particular fluorides and double fluorides of alkali and alkaline earth metals. Use of salt fluxes in the furnace helps to strip away and suspend the oxide film so that coalescence of the droplet increases and dross formation decreases. The salt flux wets the oxide film and initiates disintegration of the film, stripping it from the surface of the molten aluminium droplets. Fragments of the oxide film stripped from the aluminium remain suspended in the flux. The aluminium droplets, which have a grater density than the flux, then form a continuous molten metal surface beneath the flux layer. The flux also protects the metal surface from further oxidation. Salt fluxes are primarily mixtures of sodium chloride and potassium chloride, magnesium chloride, and/or mixtures of other inorganic salts such as carbonates and fluorides of alkali and alkaline earth metals, double salts and sodium or potassium alumino (hexa/tetra) fluorides (sodium cryolite/potassium cryolite), volatile compounds such as sodium silicofluoride and alkalies such as sodium hydroxide and potassium hydroxide. Presently most of the secondary aluminium processing industries employ powdered cover flux for treatment of molten metal, which yields high quantity of metal rich dross in which large quantities of molten aluminium gets entrapped, necessitating further melting of the dross to recover the entrapped metal. In the prior art, a number of attempts and/or methods have been adopted to improve the quality of the secondary aluminium by treatment with salt fluxes and published in US patent documents. A brief summary of is given hereunder. Langston et al in his US patent 4,261,746 discusses the use of double salts of sodium chloride in combination with excess aluminium chloride; sodium chloride and/or alkali metal fluoride and aluminium chloride, as flux in the recovery operations for secondary aluminium. (Preferred mixture of salts being 2 moles of aluminium chloride (Al CI sub 3) and one mole of sodium chloride NaCl) and heating the mixture to approximately to 100 degree C). He reports 92 to 98 %. metal recovery. Bauer et al in their US patent 4,451,287 describes the use of a salt flux in recovery of aluminium in a reverberatory furnace. The salt flux is a suitable mechanical mixture of sodium chloride (40-60 percent) and potassium chloride (60-40 percent). After mechanical mixing, the mixture is preheated to the molten state, which is then poured from the furnace; allowed to cool to room temperature. Upon cooling the solid solution salts are processed in a hammer mill or grinding mill to particles no larger than 3A inch. He also mentions about a small addition (about 3 weight percent) of cryolite. He suggests a preferred concentration ratio of 0.3-0.4 flux to inert ingredient. In his US patent 4,564,393, Murray describes the introduction of one or more metals (commercial pure aluminium powder, a powder of one or more metals or alloys comprising the metal or metals to be introduced, for example manganese, chromium, tungsten, molybdenum, titanium, vanadium, iron, cobalt, copper, niobium, tantalum, zirconium, hafnium and silver) into a melt comprising aluminium along with a salt flux (for example one or more of potassium aluminum fluoride or potassium cryolite, potassium chloride, potassium fluoride, sodium chloride, sodium fluoride, and sodium carbonate.) He concludes that the preferred proportion of the additives namely metal powder: metal/alloys: salt flux is 5%: 75%:20% respectively. He introduced the metals in the form of pellets containing respective metals namely manganese, chromium and iron powders, along with powdered aluminium and salt flux containing (a) potassium cryolite (b) Sodium chloride (4 %), potassium chloride (12.5 % and potassium cryolite (3.5%). The additions were carried out both on commercial as well as in a laboratory scale. Vire in his US patent 4,568,430 discloses a highly efficient and economical process for the recovery of high purity aluminium (>99.99 % pure) from highly contaminated scrap (dross, finely granular aluminium/ dross containing salt/dross containing aluminium) and molten salt flux. The salt flux used by him comprises of sodium chloride (45 %), potassium chloride (45 % ) cryolite/aluminium fluoride/sodium fluoride (10%) held at 750 deg C to which preheated aluminium scrap is added and held for one hour and further processed to get high purity aluminium. However, the detailed description of the process is out of scope of the present invention. US patent 4,983,216 discloses a process of continuous melting of aluminium scrap (comprising of shredded used beverage container bodies made of AA 3004 and ends AA 5182) along with the addition of halides or mixtures of alkali and alkaline earth metals of Li, Na, K Mg and Ca. A high level of recovery of aluminium has been reported by using a salt flux (either in molten or in dry condition) comprising NaCl (45-65 wt %) KC1 (35-55 wt %) and up to 5 wt % of KF, CaF sub 2or NaAlF sub2. Typical salt concentration disclosed was 3 % of the feed. Detailed description of the process, however, is not the scope of the present invention. US patent 5,405,427 discloses a salt flux composition comprising of alkali metal chlorides like sodium chloride (32-61 wt %), potassium chloride (32-61 wt %) , magnesium chloride (2-15 wt %) and carbon (2-12 wt %). The melting point of the flux is in the range of 1450 degree to 1525 degree F and a typical amount of flux used being 8 to 14 oz for 8001bs of aluminium Zhang in his US patent 5,762,722 discloses a flux for smelting aluminium. The salt used by him comprises of potassium chloride (20-65 parts by weight), sodium chloride (20-65 parts by weight), lithium chloride (1-20 parts by weight) potassium fluoride (0.3-5 parts by weight), sodium hydrosulfate (0.2-3 parts by weight). In the examples he describes a particular sequence to obtain either dry loose powder or wet powder, of the covering flux . The sequence is drying the alkali chloride salts, ball milling and sieving, adding either powder or solution (saturated) of potassium fluoride or sodium hydrosulfate to the homogeneous chloride salt mixture. He further discloses the yield of aluminium obtained by using the cover flux to be 92-98 %, that in the comparative example to be 32 %. He further suggests use of the prepared cover flux immediately or to store in plastic bags. Ireland discloses a method and composition for aluminium recycling using salt flux in the US patent 6,053,959. He mentions that the presence of sulphate impurities, especially in alkali metal chlorides, increases metal losses by the formation of dross comprising of oxides and sulphides By using high purity sodium chloride and potassium chloride (having 0.2 wt % sulphate impurity), an additive comprising of soda ash (an alkaline agent) and sodium aluminium tetra fluoride SATF (a fluoride source), as salt flux, along with shredded Used Beverage Cans (UBCs, aluminium alloys of 3003, 3004 and 5182) Ireland in his US patent 6,206,950 discloses an improvement in the aluminium recovery when compared to the metal recovered by using standard purity salts alone. He uses a salt flux to metal weight ratio as 20:1. He further discloses that a reduced atmosphere was maintained to reduce oxidation of aluminium-to-aluminium oxide during the treatments. He also states that salt flux can be recycled at least six times. Ireland in one of his US patents 6,379,418 (a product/utility), disclosed a high purity salt flux, the details are more or less as described in his previous US patents 6,053,959 and US patent 6,206,950 both being process patents. The present invention differs from the above-cited specifications in that the novel features are as under: In all these patents, however, the following aspects have not been covered. (I) Use of commercial purity salts more particularly sodium chloride, potassium chloride, magnesium chloride potassium fluoride, sodium fluoride, sodium carbonate, sodium carbonate, calcium carbonate, sodium silicofluoride, aluminium fluoride, in a process for the manufacture of granular flux for addition to molten aluminium and its alloys (II) The manner of carrying out melting and pouring the salt mixtures OBJECTS: (1) The primary object of the present invention is to utilize commercially available salts more particularly, sodium chloride, potassium chloride, magnesium chloride potassium fluoride, sodium fluoride, sodium carbonate, calcium carbonate,, sodium silicofluoride, aluminium fluoride, in a process for the manufacture of granular flux for addition to molten aluminium and its alloys. (2) Another object of the invention is to provide a process for manufacturing of granular flux for addition to molten aluminium and its alloys on a commercial scale. (3) Yet another object of the invention is to provide the sequence of adding the components of the mixture to improve the yield. (4) Another object of the invention to provide the effect of adding the proper sized fraction of the granular flux for addition to molten aluminium and its alloys melted in direct flame heating type crucible furnaces of capacity of 100 kg to 200 kilo grams of molten metal. (5) Another object of the invention to provide the effect of adding the proper sized fraction of the granular flux for addition to molten aluminium and its alloys melted in induction furnace and held in a holding furnace of about 140 to 160 kilograms of molten metal. Further objects and advantages of the invention will be found by reference to the following specification. The present invention relates to a process for manufacture of granular flux for addition to molten aluminium and its alloys comprising of commercially available, salts particularly, sodium chloride, potassium chloride, magnesium chloride, sodium fluoride, sodium carbonate, calcium carbonate, sodium silicofluoride, aluminium fluoride which are weighed in certain proportion; the mixture of salts is thoroughly mixed, then melted by adding the ingredients in a preferred sequence, in a suitable furnace and molten liquid is poured into ingots which, upon cooling to room temperature, are ground and sieved into various sizes/fractions; proper graded fractions are weighed and thoroughly mixed for using as granular flux. In order that the invention may be more fully understood, the proportion of the ingredients used is described in the following examples. Of the description given in the examples and claims the percentages taken are by weight. Example 1 Appropriate quantities of mixtures of commercial grade powders of sodium chloride preferably 70.00 wt %, potassium chloride preferably 10.00 wt %, and calcium carbonate preferably 10.00 wt % and sodium fluoride preferably 10.00 wt % are thoroughly mixed. This mixture is added in to a previously heated clay bonded graphite crucible of appropriate size and melted. The molten salt mixture is held at 50 to 60 degrees centigrade above the melting point of the salts mixture and is held in the molten state for about 4 to 5 minutes preferably 5 minutes. After alloying of the salt mixture taken place, the material is poured from thermal furnace and allowed to cool to room temperature. Subsequent to cooling, the solid solution of salts is weighed and is ground and sieved to obtain particles of different sizes. Selected grades are weighed and thoroughly mixed and stored in plastic bags or plastic containers for addition to molten aluminium and its alloys. Process details of this test are given in the following tables. Example 2 Appropriate quantities of commercial grade powders of sodium chloride preferably 70.00 wt %, magnesium chloride preferably 10.00 wt %, sodium carbonate preferably 10.00 wt % and sodium fluoride preferably 10.00 wt % and are thoroughly mixed. This mixture is processed as detailed in example in 1 and the process details are given in table 2 Example 3 Appropriate quantities of mixtures of commercial grade powders of sodium chloride preferably 70.00 wt %, potassium chloride preferably 10.00 wt %, calcium carbonate preferably 10.00 wt % sodium fluoride preferably 10.00 wt % and are thoroughly mixed. This mixture is processed as detailed in example in 1 and the process details are given in table3. Example 4 Appropriate quantities of mixtures of commercial grade powders of sodium chloride preferably 80.00 wt %, potassium chloride preferably 5.00 wt %, calcium carbonate preferably lO.OOwt % sodium fluoride preferably 5.00 wt % and are thoroughly mixed. This mixture is processed as detailed in example in 1 and the process details are given in table 4. Example 5 An appropriate quantity of mixtures of commercial grade powders of sodium chloride preferably 75.00wt %, potassium chloride preferably 5.00wt %, magnesium chloride preferably 5.00wt %, calcium carbonate preferably lO.OOwt % sodium fluoride preferably 5.00 wt % and are thoroughly mixed. This mixture is processed as detailed in example in 1 and the process details are given in table 5. Example 6 An appropriate quantity of mixtures of commercial grade powders of sodium chloride [rock salt form having an average particle size of 4-5mm] preferably 62.50 wt %, potassium chloride preferably 20.80 wt %, calcium carbonate preferably 10.41 wt % sodium fluoride preferably 6.25 wt % and are thoroughly mixed. This mixture is processed as detailed in example in 1 and the process details are given in table 6. Example 7. Various types of gradings/size fractions tested in the present invention are given in table 7. Table 7 Particle sizes tested in the present invention: Preferred embodiment: I The preferred salt composition is Commercial grade sodium chloride 75.00wt%, commercial grade potassium chloride 10.00 wt %, commercial grade sodium carbonate 5.00.00 wt % and commercial grade sodium fluoride 10.00 wt % IT The preferred sequence of addition of the components of the salt mixtures is To first melt requisite quantity of sodium chloride and potassium chloride and/or magnesium chloride mixture, then addition of sodium carbonate to the molten salt solution of sodium chloride and potassium chloride, then addition of requisite quantity of sodium fluoride to the above molten salt mixture. By adhering to above process parameters during melting we obtained an average yield of 85 to 90 %. Ill The preferred graded fraction of the granular flux is By employing the graded fraction of type II grade, we obtained low quantity, powder rich dross, in which aluminium coalesces. The present invention is described in details with reference to examples. However, these examples are intended to explain the present invention., and not to restrict it in any way. The scope of the invention is defined by the foiiowing claims. Many modifications and variations of the invention will be apparent to those skilled in the art in light of the foregoing disclosure. Therefore, it is to be understood that, within the scope of the claims, the invention can be practiced otherwise than as specifically described. I claim (1) A process for manufacture of granular flux for addition to molten aluminium and its alloys comprising of commercially available, salts particularly, sodium chloride, potassium chloride, magnesium chloride, sodium fluoride, sodium carbonate, calcium carbonate, sodium silicofluoride, aluminium fluoride which are weighed in certain proportion; the mixture of salts is thoroughly mixed, then melted by adding the ingredients in a preferred sequence, in a suitable furnace and molten liquid is poured into ingots which, upon cooling to room temperature, are ground and sieved into various sizes/fractions; proper graded fractions are weighed and thoroughly mixed for using as granular flux. (2) A process for the manufacture of granular flux as claimed in claim 1 wherein sodium chloride, potassium chloride, magnesium chloride, calcium carbonate, sodium carbonate and sodium fluoride, all chemicals used are of commercial purity. (3) A process for the manufacture of granular flux for addition to molten aluminium and its alloys according to claim 1 the flux can contain sodium chloride 70 to 85wt %, potassium chloride 10-15 wt % magnesium chloride 10 to 15 wt %, calcium chloride 5-15 wt % and/or sodium carbonate 5-15 % and sodium fluoride 5 to 15 wt% (4) A process according claim 1 wherein chloride salts are melted first at a temperature of 650 to 700 degree C. (5) A process for the manufacture of granular flux, as claimed in claim land claim 4 the salt mixture is heated to about 50-60 degree C above the melting point thereof. (6) A process according to claim 5 where in carbonates and alkaline fluoride(s) and/or sodium silico fluoride is added and held for 5 to 10 minutes at the molten state at a temperature of 650 to 700 degree C. (7) A process according to claim 6where in the molten alloy mixture of salts is held for about 5-10minutes before pouring from thermal furnace. (8) A process according to claim 7 wherein the cooled ingots are processed by grinding and sieving to required sizes. (9) A process according to claim 8, sieved fractions is weighed in a preferred weight percentage and is mixed thoroughly for use as granular flux.

Full Text

This invention relates to a process for the manufacture of granular flux for addition to molten aluminium and its alloys.
The processing of aluminium is divided into primary and secondary industries. For energy savings and economy, much aluminium ingot is alloyed and cast at smelting plants using primary metal (which is produced by direct-current electrolysis of molten Alumina dissolved in molten sodium fluoride-aluminium fluoride bath at 940-980 °C; Hall-Heroult Process) while still molten. Secondary aluminium is recovered from scrap, is on of the important contributors to the tota metal supply. New scrap is defined as that generated by plants making end products, where as old scrap is that recovered metal which has been previously used by consumers which is being recycled. The furnace charge may be made up of any one or combination of the retuned gates, risers, pre-alloyed ingots, prmary metal together with, alloying elements or molten metal. Molten aluminium/ its alloys are extremely reactive and combine readily with other metals, with gases and some times with refractories. Aluminium is readily oxidized metal and the reaction proceeds as per the equation-1 given below:

The oxide formed is both adherent and relatively impermeable so that the initial film formed is of the order of 0.01 \im on first formation and may grow up to 0.4 \im on metal which has been given a normal muffle anneal at say 400°C. Surface tension of molten aluminium is very high, and when augmented by the formation of a film of oxide, surface tension is so great that it causes difficulty in casting thin sections. However, the surface tension of molten aluminium is great enough to keep a charge of fines floating on top of the molten bath.
In aluminium melting, especially in re-melting of foundry returns or other scrap, oxide formation and non-metallic impurities are common. Impurities appear in the form of liquid and solid inclusions, persist through melt solidification into the casting. Inclusions can originate from dirty tools, sand and other molding debris, sludge (iron-chromium-nickel intermetallic compounds commonly found in the die casting alloys), metal working lubricants, and the oxidation of alloying elements and /or the base metal.

For the purpose of clarity and to avoid ambiguity, a few of the technical terms used in the specification are defined here to mean as under. DROSSING is the formation of aluminium oxide and other oxides, which accumulate on the melt surface.
COMMERCIAL GRADE CHEMICALS: Salts that are available, which have higher impurities than those of laboratory grade salts.
Alloying of the salt mixture: Mixtures of alkaline and alkaline earth metal salts more particularly chlorides, fluorides, carbonates, such as sodium chloride, potassium chloride, magnesium chloride, potassium fluoride, sodium fluoride, sodium carbonate, and which are melted to form a homogeneous solution, which is then cooled to room temperature.
YIELD: Ratio of the weight (W2) of the cooled solid solution of the salts (namely mixtures of alkaline and alkaline earth metal salts more particularly chlorides, fluorides, carbonates, such as sodium chloride, potassium chloride, potassium fluoride, sodium fluoride, sodium carbonate, calcium caibonate, and alkaline alumino-fluorides) to the weight (Wi) of the powder salt mixture (before melting)
multiplied by 100 Aluminium: LMO
Aluminium Alloys LMS,LM6, LM9, LM13,LM 20,LM2S
Complete separation of dross and metal would be favored by large differences in
their specific gravities. However, the specific gravities of the oxides and molten
metal i.e. aluminium are of similar magnitude as given in table (1). Oxides of
aluminium and magnesium form quickly on the surface of the molten metal bath,
making a thin tenacious skin that prevents further oxidation as long as the surface
is not disturbed. Molten aluminium also reacts with moisture to form aluminium
oxide realizing hydrogen. Moisture on charge materials, tools, fluxes and
refractories causes rapid oxidation of the metal. Agitation of the molten bath
results in suspension of the surface oxide skin in the molten metal. The densities of
the oxides are nearly same as that of the molten metal and thus the oxides are
likely to be carried into the castings.

Fluxing of the melt facilitates the agglomeration and separation of such undesirable constituents from the melt. Certain flux compositions have been used for years, not because they have special merits, but rather because of tradition.
The intelligent use of a flux requires detailed knowledge of the chemical and physical relationships between (1) metal and flux (2) foreign matter and flux and (3) metal and foreign matter.
The dissolution of aluminium oxide, dirt or other coating on the globules of liquid metal is a necessary attribute of a flux. Coalescence of globules cannot take place unless the coating is ruptured. It would appear that the oxide coating might more easily and thoroughly be removed by chemical rather than mechanical means. An important attribute of a flux is the power to reduce the surface tension of the globules there by promoting the coalescence of metal globules that is increasing the fluidity. Fluxes, which dissolve aluminium oxide by chemical action, contain fluoride salts, which dissolve aluminium oxide, in particular fluorides and double fluorides of alkali and alkaline earth metals.
Use of salt fluxes in the furnace helps to strip away and suspend the oxide film so that coalescence of the droplet increases and dross formation decreases. The salt flux wets the oxide film and initiates disintegration of the film, stripping it from the surface of the molten aluminium droplets. Fragments of the oxide film stripped from the aluminium remain suspended in the flux. The aluminium droplets, which have a grater density than the flux, then form a continuous molten metal surface beneath the flux layer. The flux also protects the metal surface from further oxidation. Salt fluxes are primarily mixtures of sodium chloride and potassium chloride, magnesium chloride, and/or mixtures of other inorganic salts such as carbonates and fluorides of alkali and alkaline earth metals, double salts and sodium or potassium alumino (hexa/tetra) fluorides (sodium cryolite/potassium cryolite), volatile compounds such as sodium silicofluoride and alkalies such as sodium hydroxide and potassium hydroxide.
Presently most of the secondary aluminium processing industries employ powdered cover flux for treatment of molten metal, which yields high quantity of metal rich dross in which large quantities of molten aluminium gets entrapped, necessitating further melting of the dross to recover the entrapped metal.

In the prior art, a number of attempts and/or methods have been adopted to improve the quality of the secondary aluminium by treatment with salt fluxes and published in US patent documents. A brief summary of is given hereunder.
Langston et al in his US patent 4,261,746 discusses the use of double salts of sodium chloride in combination with excess aluminium chloride; sodium chloride and/or alkali metal fluoride and aluminium chloride, as flux in the recovery operations for secondary aluminium. (Preferred mixture of salts being 2 moles of aluminium chloride (Al CI sub 3) and one mole of sodium chloride NaCl) and heating the mixture to approximately to 100 degree C). He reports 92 to 98 %. metal recovery.
Bauer et al in their US patent 4,451,287 describes the use of a salt flux in recovery of aluminium in a reverberatory furnace. The salt flux is a suitable mechanical mixture of sodium chloride (40-60 percent) and potassium chloride (60-40 percent). After mechanical mixing, the mixture is preheated to the molten state, which is then poured from the furnace; allowed to cool to room temperature. Upon cooling the solid solution salts are processed in a hammer mill or grinding mill to particles no larger than 3A inch. He also mentions about a small addition (about 3 weight percent) of cryolite. He suggests a preferred concentration ratio of 0.3-0.4 flux to inert ingredient.
In his US patent 4,564,393, Murray describes the introduction of one or more metals (commercial pure aluminium powder, a powder of one or more metals or alloys comprising the metal or metals to be introduced, for example manganese, chromium, tungsten, molybdenum, titanium, vanadium, iron, cobalt, copper, niobium, tantalum, zirconium, hafnium and silver) into a melt comprising aluminium along with a salt flux (for example one or more of potassium aluminum fluoride or potassium cryolite, potassium chloride, potassium fluoride, sodium chloride, sodium fluoride, and sodium carbonate.) He concludes that the preferred proportion of the additives namely metal powder: metal/alloys: salt flux is 5%: 75%:20% respectively. He introduced the metals in the form of pellets containing respective metals namely manganese, chromium and iron powders, along with powdered aluminium and salt flux containing (a) potassium cryolite (b) Sodium chloride (4 %), potassium chloride (12.5 % and potassium cryolite (3.5%). The additions were carried out both on commercial as well as in a laboratory scale.
Vire in his US patent 4,568,430 discloses a highly efficient and economical process for the recovery of high purity aluminium (>99.99 % pure) from highly contaminated scrap (dross, finely granular aluminium/ dross containing salt/dross containing aluminium) and molten salt flux. The salt flux used by him comprises of sodium chloride (45 %), potassium chloride (45 % ) cryolite/aluminium fluoride/sodium fluoride (10%) held at 750 deg C to which preheated aluminium scrap is added and held for one hour and further processed to get high purity aluminium. However, the detailed description of the process is out of scope of the present invention.

US patent 4,983,216 discloses a process of continuous melting of aluminium scrap (comprising of shredded used beverage container bodies made of AA 3004 and ends AA 5182) along with the addition of halides or mixtures of alkali and alkaline earth metals of Li, Na, K Mg and Ca. A high level of recovery of aluminium has been reported by using a salt flux (either in molten or in dry condition) comprising NaCl (45-65 wt %) KC1 (35-55 wt %) and up to 5 wt % of KF, CaF sub 2or NaAlF sub2. Typical salt concentration disclosed was 3 % of the feed. Detailed description of the process, however, is not the scope of the present invention.
US patent 5,405,427 discloses a salt flux composition comprising of alkali metal chlorides like sodium chloride (32-61 wt %), potassium chloride (32-61 wt %) , magnesium chloride (2-15 wt %) and carbon (2-12 wt %). The melting point of the flux is in the range of 1450 degree to 1525 degree F and a typical amount of flux used being 8 to 14 oz for 8001bs of aluminium
Zhang in his US patent 5,762,722 discloses a flux for smelting aluminium. The salt used by him comprises of potassium chloride (20-65 parts by weight), sodium chloride (20-65 parts by weight), lithium chloride (1-20 parts by weight) potassium fluoride (0.3-5 parts by weight), sodium hydrosulfate (0.2-3 parts by weight). In the examples he describes a particular sequence to obtain either dry loose powder or wet powder, of the covering flux . The sequence is drying the alkali chloride salts, ball milling and sieving, adding either powder or solution (saturated) of potassium fluoride or sodium hydrosulfate to the homogeneous chloride salt mixture. He further discloses the yield of aluminium obtained by using the cover flux to be 92-98 %, that in the comparative example to be 32 %. He further suggests use of the prepared cover flux immediately or to store in plastic bags.
Ireland discloses a method and composition for aluminium recycling using salt flux in the US patent 6,053,959. He mentions that the presence of sulphate impurities, especially in alkali metal chlorides, increases metal losses by the formation of dross comprising of oxides and sulphides
By using high purity sodium chloride and potassium chloride (having 0.2 wt % sulphate impurity), an additive comprising of soda ash (an alkaline agent) and sodium aluminium tetra fluoride SATF (a fluoride source), as salt flux, along with shredded Used Beverage Cans (UBCs, aluminium alloys of 3003, 3004 and 5182) Ireland in his US patent 6,206,950 discloses an improvement in the aluminium recovery when compared to the metal recovered by using standard purity salts alone. He uses a salt flux to metal weight ratio as 20:1. He further discloses that a reduced atmosphere was maintained to reduce oxidation of aluminium-to-aluminium oxide during the treatments. He also states that salt flux can be recycled at least six times.
Ireland in one of his US patents 6,379,418 (a product/utility), disclosed a high purity salt flux, the details are more or less as described in his previous US patents 6,053,959 and US patent 6,206,950 both being process patents.

The present invention differs from the above-cited specifications in that the novel
features are as under:
In all these patents, however, the following aspects have not been covered.
(I) Use of commercial purity salts more particularly sodium chloride, potassium chloride, magnesium chloride potassium fluoride, sodium fluoride, sodium carbonate, sodium carbonate, calcium carbonate, sodium silicofluoride, aluminium fluoride, in a process for the manufacture of granular flux for addition to molten aluminium and its alloys
(II) The manner of carrying out melting and pouring the salt mixtures
OBJECTS:
(1) The primary object of the present invention is to utilize commercially available salts more particularly, sodium chloride, potassium chloride, magnesium chloride potassium fluoride, sodium fluoride, sodium carbonate, calcium carbonate,, sodium silicofluoride, aluminium fluoride, in a process for the manufacture of granular flux for addition to molten aluminium and its alloys.
(2) Another object of the invention is to provide a process for manufacturing of granular flux for addition to molten aluminium and its alloys on a commercial scale.
(3) Yet another object of the invention is to provide the sequence of adding the components of the mixture to improve the yield.
(4) Another object of the invention to provide the effect of adding the proper sized fraction of the granular flux for addition to molten aluminium and its alloys melted in direct flame heating type crucible furnaces of capacity of 100 kg to 200 kilo grams of molten metal.
(5) Another object of the invention to provide the effect of adding the proper sized fraction of the granular flux for addition to molten aluminium and its alloys melted in induction furnace and held in a holding furnace of about 140 to 160 kilograms of molten metal.
Further objects and advantages of the invention will be found by reference to the following specification.

The present invention relates to a process for manufacture of granular flux for addition to molten aluminium and its alloys comprising of commercially available, salts particularly, sodium chloride, potassium chloride, magnesium chloride, sodium fluoride, sodium carbonate, calcium carbonate, sodium silicofluoride, aluminium fluoride which are weighed in certain proportion; the mixture of salts is thoroughly mixed, then melted by adding the ingredients in a preferred sequence, in a suitable furnace and molten liquid is poured into ingots which, upon cooling to room temperature, are ground and sieved into various sizes/fractions; proper graded fractions are weighed and thoroughly mixed for using as granular flux.
In order that the invention may be more fully understood, the proportion of the ingredients used is described in the following examples. Of the description given in the examples and claims the percentages taken are by weight.
Example 1
Appropriate quantities of mixtures of commercial grade powders of sodium chloride preferably 70.00 wt %, potassium chloride preferably 10.00 wt %, and calcium carbonate preferably 10.00 wt % and sodium fluoride preferably 10.00 wt % are thoroughly mixed. This mixture is added in to a previously heated clay bonded graphite crucible of appropriate size and melted. The molten salt mixture is held at 50 to 60 degrees centigrade above the melting point of the salts mixture and is held in the molten state for about 4 to 5 minutes preferably 5 minutes. After alloying of the salt mixture taken place, the material is poured from thermal furnace and allowed to cool to room temperature. Subsequent to cooling, the solid solution of salts is weighed and is ground and sieved to obtain particles of different sizes. Selected grades are weighed and thoroughly mixed and stored in plastic bags or plastic containers for addition to molten aluminium and its alloys. Process details of this test are given in the following tables.

Example 2
Appropriate quantities of commercial grade powders of sodium chloride preferably 70.00 wt %, magnesium chloride preferably 10.00 wt %, sodium carbonate preferably 10.00 wt % and sodium fluoride preferably 10.00 wt % and are thoroughly mixed. This mixture is processed as detailed in example in 1 and the process details are given in table 2

Example 3
Appropriate quantities of mixtures of commercial grade powders of sodium chloride preferably 70.00 wt %, potassium chloride preferably 10.00 wt %, calcium carbonate preferably 10.00 wt % sodium fluoride preferably 10.00 wt % and are thoroughly mixed. This mixture is processed as detailed in example in 1 and the process details are given in table3.

Example 4
Appropriate quantities of mixtures of commercial grade powders of sodium chloride preferably 80.00 wt %, potassium chloride preferably 5.00 wt %, calcium carbonate preferably lO.OOwt % sodium fluoride preferably 5.00 wt % and are thoroughly mixed. This mixture is processed as detailed in example in 1 and the process details are given in table 4.

Example 5
An appropriate quantity of mixtures of commercial grade powders of sodium chloride preferably 75.00wt %, potassium chloride preferably 5.00wt %, magnesium chloride preferably 5.00wt %, calcium carbonate preferably lO.OOwt % sodium fluoride preferably 5.00 wt % and are thoroughly mixed. This mixture is processed as detailed in example in 1 and the process details are given in table 5.

Example 6
An appropriate quantity of mixtures of commercial grade powders of sodium chloride [rock salt form having an average particle size of 4-5mm] preferably 62.50 wt %, potassium chloride preferably 20.80 wt %, calcium carbonate preferably 10.41 wt % sodium fluoride preferably 6.25 wt % and are thoroughly mixed. This mixture is processed as detailed in example in 1 and the process details are given in table 6.

Example 7.
Various types of gradings/size fractions tested in the present invention are
given in table 7.
Table 7 Particle sizes tested in the present invention:

Preferred embodiment:
I The preferred salt composition is
Commercial grade sodium chloride 75.00wt%, commercial grade potassium chloride 10.00 wt %, commercial grade sodium carbonate 5.00.00 wt % and commercial grade sodium fluoride 10.00 wt %
IT The preferred sequence of addition of the components of the salt mixtures is
To first melt requisite quantity of sodium chloride and potassium chloride
and/or magnesium chloride mixture, then addition of sodium carbonate to
the molten salt solution of sodium chloride and potassium chloride, then
addition of requisite quantity of sodium fluoride to the above molten salt
mixture.
By adhering to above process parameters during melting we obtained
an average yield of 85 to 90 %.
Ill The preferred graded fraction of the granular flux is

By employing the graded fraction of type II grade, we obtained low quantity, powder rich dross, in which aluminium coalesces.
The present invention is described in details with reference to examples. However, these examples are intended to explain the present invention., and not to restrict it in any way. The scope of the invention is defined by the foiiowing claims. Many modifications and variations of the invention will be apparent to those skilled in the art in light of the foregoing disclosure. Therefore, it is to be understood that, within the scope of the claims, the invention can be practiced otherwise than as specifically described.

I claim
(1) A process for manufacture of granular flux for addition to molten
aluminium and its alloys comprising of commercially available,
salts particularly, sodium chloride, potassium chloride, magnesium
chloride, sodium fluoride, sodium carbonate, calcium carbonate,
sodium silicofluoride, aluminium fluoride which are weighed in
certain proportion; the mixture of salts is thoroughly mixed, then
melted by adding the ingredients in a preferred sequence, in a
suitable furnace and molten liquid is poured into ingots which, upon
cooling to room temperature, are ground and sieved into various
sizes/fractions; proper graded fractions are weighed and thoroughly
mixed for using as granular flux.
(2) A process for the manufacture of granular flux as claimed in claim 1
wherein sodium chloride, potassium chloride, magnesium chloride,
calcium carbonate, sodium carbonate and sodium fluoride, all
chemicals used are of commercial purity.
(3) A process for the manufacture of granular flux for addition to
molten aluminium and its alloys according to claim 1 the flux can
contain sodium chloride 70 to 85wt %, potassium chloride 10-15 wt
% magnesium chloride 10 to 15 wt %, calcium chloride 5-15 wt %
and/or sodium carbonate 5-15 % and sodium fluoride 5 to 15 wt%
(4) A process according claim 1 wherein chloride salts are melted first at a temperature of 650 to 700 degree C.
(5) A process for the manufacture of granular flux, as claimed in claim land claim 4 the salt mixture is heated to about 50-60 degree C above the melting point thereof.
(6) A process according to claim 5 where in carbonates and alkaline
fluoride(s) and/or sodium silico fluoride is added and held for 5 to
10 minutes at the molten state at a temperature of 650 to 700 degree
C.
(7) A process according to claim 6where in the molten alloy mixture of salts is held for about 5-10minutes before pouring from thermal furnace.
(8) A process according to claim 7 wherein the cooled ingots are processed by grinding and sieving to required sizes.
(9) A process according to claim 8, sieved fractions is weighed in a preferred weight percentage and is mixed thoroughly for use as granular flux.

Documents:

432-che-2004-abstract.pdf

432-che-2004-claims duplicate.pdf

432-che-2004-claims original.pdf

432-che-2004-correspondnece-others.pdf

432-che-2004-correspondnece-po.pdf

432-che-2004-description(complete) duplicate.pdf

432-che-2004-description(complete) original.pdf

432-che-2004-form 1.pdf

432-che-2004-form 19.pdf

432-che-2004-form 26.pdf

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Patent Number

205198

Indian Patent Application Number

432/CHE/2004

PG Journal Number

26/2007

Publication Date

29-Jun-2007

Grant Date

22-Mar-2007

Date of Filing

11-May-2004

Name of Patentee

SHRI. HUMCHA SUNDARA MURTHY

Applicant Address

NO.160, 36TH A CROSS, 7TH BLOCK , JAYANAGAR BANGALOR 560 082

Inventors:

#	Inventor's Name	Inventor's Address
1	HUMCHA SUNDARA MURTHY	NO.160,36TH A CROSS,7TH BLOCK , JAYANAGAR BANGALOR 560 082

PCT International Classification Number

B23K35/362

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA