I found some material to clarify degasing versus fluxing.
All gases are insoluable in Aluminum except hydrogen. Any gas pumped into the melt will "collects the hydrogen but also removes particulate matter, that is, inclusions, by flotation".
Not sure if this was mentioned but the chlorine Anon is talking about is produced from the decomposition of the solid hexachloroethane tablets.
Aluminum Foundry Degassing
Degassing of aluminum alloy melts is a critical melt treatment technology necessary to provide readiness of the melt for casting into many applications (Ref 1, Ref 2, Ref 3, Ref 4, Ref 5, Ref 6, Ref 7, Ref 8). Hydrogen is the only gas that is soluble in aluminum, as monatomic hydrogen. Figure 1 exhibits the hydrogen solubility of typical aluminum-silicon foundry alloys. Clearly, a substantial amount of hydrogen can be present in the liquid state, but as the melt solidifies, there is a substantial reduction in the amount of hydrogen that can exist in the solid state. How this change takes place will determine whether porosity will form. If not removed or reduced to an acceptable level determined by prior process and quality studies, the gas dissolved in molten aluminum, if not treated, can result in detrimental properties to castings.
]Fig. 1 Hydrogen solubility in aluminum casting alloys. Source: Ref 2[/h]
Figure 2 is a classic example of gas porosity developed during solidification in an aluminum alloy casting. Loss in mechanical properties, such as tensile strength, elongation, fatigue strength, and fracture toughness, are common results. In addition, interconnected porosity can result in “leakers” during pressure-tightness testing and blistering upon subsequent heat treatment as the pores grow and open up; this is especially a problem on the surface when surface finish/cosmetic properties are required.
Fig. 2 Typical porosity configurations in aluminum-silicon casting alloys. (a) Shrinkage pore found within a casting. (b) Gas pore in an Al-8% Si alloy. (c) Microporosity (gas plus shrinkage). (d) Microporosity (gas plus shrinkage). Source: Ref 2
However, gas can arise not only from entrapped hydrogen dissolved during the melting process and evolving as gas during the liquid-solid transition, but also gas can result from aspirated air or gas evolution from molding materials (i.e., cores, binders, etc.). Thus, it is not totally clear in Fig. 2(a) that the porosity is due to evolution of hydrogen gas. Observable porosity may also very well be caused by lack of feeding, that is, shrinkage, during solidification. In fact, Fig. 2 depicts porosity that follows very well the interdendritic structure and hence is very likely shrinkage, not gas.
In Fig. 2(b), the rounded porosity would suggest gas evolution during final stages of solidification and hence could very well be caused by hydrogen, However, further microscopic investigation may be necessary, since this porosity may also be caused by entrapped air or lubricant decomposition. In actual practice, it is therefore best to degas the melt to an acceptable level before casting. A typical target value, below which hydrogen-caused porosity is not normally a problem in the final casting, is that the degassing process should achieve a level of 0.15 mL H2/100 g Al, the usual standard of measurement n a quantified test such as Alscan (Alcan Aluminum Ltd.). If one is instead using the reduced-pressure test as a measure of minimal porosity potential, it is not possible to accurately predict lack of hydrogen-caused porosity by this means alone. However, reaching a high percentage value in the reduced-pressure test related to the specific alloy theoretical density is a good measure, for instance, 2.62 in A356, whose theoretical density is 2.68 g/cm3.
Given the propensity of aluminum to readily absorb hydrogen, there are many ways that hydrogen can and will always be present in a melt to a certain degree. Fuel-fired furnaces (natural gas, oil) have hydrogen available from fossil fuel decomposition. Water vapor is almost always present in the atmosphere, even at high temperatures directly in contact with the melting furnace. Indeed, high humidity conditions exacerbate not only hydrogen dissolution in the melt but also can retard the ability of any melt treatment to remove hydrogen, because a degassed melt can then readily redissolve additional hydrogen. Ingot, additives, and fluxes are other common sources of hydrogen. In the case of fluxes, fluxing compounds are usually mixtures of various salts, including halides, and become very hygroscopic when exposed to air. In addition, the tools used to add and work in fluxes—rakes, spoons, and so on—will often retain flux and oxide debris after use, which will then adsorb moisture from the air as they cool down. Reuse of these tools, without intermediate cleaning, not only poses a potential safety hazard but also can reintroduce hydrogen. Scrap castings, machine turnings and borings, die cast trim press scrap, gates and risers, and sand and other nonmetallic molding material debris are additional sources of hydrogen.
There are many means available to minimize hydrogen pickup or to degas a melt. Noting the increased solubility with temperature, as depicted in Fig. 1, merely minimizing the melting or holding times and temperatures will lessen the hydrogen absorption. Reducing the temperature will result in natural outgassing, given time, which is not always available. Therefore, additional degassing measures are often needed.
The basic principle of practical foundry degassing is that any gaseous component has the ability of collecting hydrogen gas, since all gases are insoluble in aluminum, with the exception of hydrogen, which exists as a single atom. Thus, a purge or process gas can function as in Fig. 3, depicting gas fluxing, which not only collects the hydrogen but also removes particulate matter, that is, inclusions, by flotation.
Fig. 3 Schematic of gas fluxing in molten aluminum
The first application of this principle was mainly through the decomposition of a solid product that reacted in molten aluminum. Historically, the degassing material commonly employed was a hexachloroethane tablet (C2Cl6). When submerged and plunged into the melt, the hexachloroethane decomposed into its respective components. The chlorine component immediately forms a metastable aluminum chloride gaseous compound, which is insoluble in the melt and served as the purge gas. With any purge gas, the monatomic hydrogen diffuses into the purge gas bubble, combines with another hydrogen atom to form molecular hydrogen, and the bubble rises to the surface, where both gaseous species are released. The fluxing components in the hexachloroethane tablet, which are often halide salts, served not only to bind the tablet, but these salt components do aid in wetting of the gas bubble in the aluminum, reducing the interfacial energy and allowing easier transmittal of the hydrogen atoms into the collector aluminum chloride gas bubble. This use of hexachloroethane tablets has given way to other degas methodologies, in most instances because of environmental concerns and more efficient technologies. However, some foundries still employ this technique, especially on small crucible furnaces.
The second most popular degassing technique in historical use—and still used today (200—is a simple flux wand or static lance. This can be a steel pipe or, more commonly, a graphite lance. A purge gas such as nitrogen or argon is injected under low pressure (less than 207 kPa, or 30 psi) into the melt. The insoluble nitrogen or argon gas bubble then rises within the melt, and the hydrogen atoms diffuse to this process gas bubble and form a hydrogen molecule. When the bubble reaches the surface of the melt, the hydrogen is released. If the relative humidity in the atmosphere is particularly high, this will be a dynamic process, because new hydrogen may become absorbed into the melt.
Fundamentally, the lance degassing technique is relatively inefficient, as is seen later in this section, in relation to newer technologies. The reason for this is the relatively large gas bubble that emanates from the bottom of the lance and then agglomerates and rises quickly to the surface. The rate of rise increases with bubble size, and the bubble accelerates as it climbs toward the surface. Fig. 4(a) depicts a water model showing that a static lance only influences a small volume of fluid surrounding the lance, unless it is manually moved about. While this is possible in relatively small-diameter melting and holding vessels, it is impractical in larger ones.
Selecting a Process Gas. Since all gases except hydrogen are insoluble in molten aluminum, there are theoretically many choices of which gas to use.
Nitrogen is the most commonly employed and is the least expensive. Nitrogen creates a wet dross; that is, the dross that is formed is high in metallic aluminum content. Furthermore, since the density of nitrogen is comparable to air overall, there is a tendency to pick up moisture in nitrogen lines as fittings deteriorate and humid air is aspirated into the delivery lines. For this reason, all nitrogen sources should include an in-line dryer. Nitrogen purity should be at least 99.99% for any critical casting applications.
Argon, while significantly more expensive than nitrogen, produces a less metal-rich dross. Argon is more inert, and, being heavier, provides a protective cover over the melt during degassing, precluding not only hydrogen absorption but further oxidation as well. It is also easier to keep the argon supply drier and cleaner as hoses and fittings deteriorate. While argon is the preferred process gas for in-line degassing treatment in the production of wrought alloys, it is not extensively used in foundry casting because of the higher cost.
Active Halogens. Historically, a small percentage of chlorine (5 to 10%) was used with an inert gas when degassing with a static lance. The chlorine enhanced the reaction between the melt and the hydrogen atoms because it lowered the interfacial tension at the purge gas bubble surface (through the formation of aluminum chloride, a metastable gaseous phase) and facilitated the diffusion of the hydrogen atom into the purge gas bubble. Several commercial mixtures of halogen gases—Freon (CCl2F2) (Dupont) being the most popular—were employed in the past. With the growing concern and difficulties with the environmental impact of chlorine use, sulfur hexafluoride (SF6) gained prominence 20 years ago as a replacement for chlorine. However, subsequent experience showed that SF6 also posed environmental problems with ozone depletion, and the gas is very corrosive, even in small amounts, to foundry metal structures.
Fortunately, with the advent of rotor degassing and the resultant better kinetics of reaction and mixing, it has been found that chlorine does not enhance the degassing rate or efficiency when the purge/process gas bubbles are sufficiently small, as they are with rotor impeller degassing. Rather, when chlorine is used, there is better wetting of the nonmetallic inclusions during the degassing process, so that metal cleanliness is improved, and the burden on any subsequent particulate removal process is lessened, which in turn creates a better-quality cast product.
Other Considerations for the Degassing Process. There are other issues that must be taken into account during the degassing process.
Temperature. It is well understood that hydrogen absorption in the melt increases with increasing temperature. Conversely, hydrogen solubility and partial pressure of hydrogen gas in the melt decrease rapidly as the melt temperature is decreased. It follows that minimizing the temperature will result in lower hydrogen value.
Given sufficient time, allowing the temperature to drop will result in natural outgassing. However, the injection of a purge gas at normal standard temperature and pressure creates an endothermic reaction, and heat will therefore be lost at an accelerated rate. A general rule-of-thumb is that degassing a metal volume of 455 kg (1000 lb) in an unheated refractory vessel for 5 to 10 min will result in a temperature drop of nearly 28 °C (50 °F). Whatever the actual magnitude of the temperature drop due to gas injection/treatment time, this reduction must be accommodated in relation to the necessary temperature that must be maintained as the treated melt is transferred into the mold or into the casting station(s). A degassing process should nevertheless be carried out at the lowest practical temperature possible.
Grain Refining. Most aluminum melts in sand, permanent mold, and low-pressure foundry production require grain refinement to achieve the best mechanical properties in the finished casting. In most instances, grain refiner is added during the degassing process, because the increased mixing and agitation facilitates the dissolution and reaction of the grain refiner itself and provides more uniform dispersion throughout the melt or treated volume.
Modification. Historically, the element sodium was used to provide modification of the eutectic silicon component in aluminum casting alloys—a necessary practice, together with grain refining, to produce desired mechanical properties. In current practice, sodium has given way to a strontium addition for many reasons, including safety in handling and in the environment, better consistency, and reduced fade, which is the loss of modification with time. Because both sodium and strontium are prone to oxidation (although strontium vapor pressure is substantially lower than sodium), and the degassing mixing creates more convection during treatment, degassing should take place before modification, so as not to lose the benefits of the dissolved modifier due to oxidation. If chlorine is used, even in small quantities, in the degassing process, both sodium and strontium will react chemically to form solid chloride reaction products.
Dross Formation and Skimming. The action of the purge gas injection process by whatever means—lance, rotor, or porous plug/disperser—will result in flotation of debris and some degree of particulate inclusion content within the melt. Naturally, the degassing process creates dross. This must be thoroughly skimmed off the surface to the greatest practical extent possible to avoid transfer into the casting mold or casting station.
Determining Hydrogen Content. To control hydrogen content, one must be able to measure the hydrogen content in the melt and the subsequent result of any hydrogen-removal treatment. Laboratory evaluations are possible using vacuum fusion (Leco technique) and subvacuum fusion on previously solidified test specimens. Obviously, laboratory measurements cannot be used to make real-time decisions but rather are useful in process development. Real-time determinations are limited to the simple reduced-pressure test (RPT) and its variants, and in situ techniques, such as Alscan, continuous hydrogen analysis by pressure evaluation, and others. The RPTs are the simplest, but these tests are a measure of molten metal cleanliness and not absolute hydrogen content per se. The presence of inclusions in the melt during an RPT evaluation will create exaggerated porosity nucleated during solidification and a resultant lower density value. The Alscan test and others of this type do generate a real-time result through the principles of recirculating gas of a known standard hydrogen content and the thermal conductivity of dilute solutions.
References cited in this section
- R. Monroe, Porosity in Castings, Trans. AFS, Vol 113, 2005, p 519–546
- J.E. Gruzleski and B.M. Closset, The Treatment of Liquid Aluminum-Silicon Alloys, AFS, 1990
- D. Apelian, Clean Metal Processing of Aluminum, Proceedings, Materials Solutions Conference '98 on Aluminum Casting Technology, ASM International, 1998
- G. Sigworth and T. Engh, Chemical and Kinetic Factors Related to Hydrogen Removal from Aluminum, Metall. Trans., Vol 138, 1982, p 447
- G. Sigworth, A Scientific Basis for Degassing Aluminum, Trans. AFS, Vol 95, 1987, p 73
- D.V. Neff, Understanding Aluminum Degassing, Mod. Cast., May 2002
- D. Apelian and M.M. Makhlouf, Ed., High Integrity Aluminum Die Casting, NADCA, April 2004
- M.M. Makhlouf, L. Wang, and D. Apelian, Measurement and Removal of Hydrogen in Aluminum Alloys, AFS Special Report, 1998
Aluminum Fluxes and Fluxing Practice
Rafael Gallo, Foseco Metallurgical David Neff, Pyrotek
IT IS WELL KNOWN that molten aluminum casting alloys have two inherent characteristics: the tendency to absorb hydrogen gas, and the ability to readily oxidize. Hydrogen is made available at the surface of molten aluminum alloys through the reaction of the molten bath with the water vapor present in the melting environment (Ref 1, Ref 2, Ref 3, Ref 4). The reaction between water vapor and molten aluminum yields not only hydrogen gas but also the formation (within milliseconds) of an amorphous aluminum oxide (Al2O3) film on the surface bath, which acts as a protective oxidation barrier for the molten metal underneath the film. The amorphous films have been referred to as young films (Ref 5).
The two oxidation reactions that occur when molten aluminum contacts air proceed according to the following:
Any of these melting practices causes the thin aluminum oxide films to break and reoxidize, causing rapid aluminum oxide film thickening (oxide buildup).
The constant metal movement and breaking of the aluminum oxide films cause the films to crumble, thicken, and encapsulate unoxidized molten aluminum, generating what is known as wet dross. A typical representation of this phenomenon is well observed during the filling process of transfer ladles, such as the one shown in Fig. 1. As soon as the molten metal is tapped from the melting furnace into the transfer ladle, not only does the molten stream become disturbed (from the very beginning to the end), but also a significant amount of splashing between the molten stream and the rising metal surface promotes aluminum oxidation, causing the surface of the bath to thicken with wet dross. The aluminum content of wet drosses is typically reported to be on the order of 60 to 85%, while the remaining 40 to 15% is aluminum. The amount of trapped liquid metal in the dross varies according to the melting and/or handling molten practice. The aluminum oxide is a very stable compound that cannot be reduced to aluminum under ordinary melting conditions. However, the amount of suspended liquid metal could be reduced from the 60 to 85% range to 30% by proper fluxing and drossing techniques.
Fig. 1 Metal being tapped from a holding furnace into a transfer ladle, causing aluminum oxide films to crumble, thicken, and encapsulate unoxidized molten aluminum, generating wet dross
Formation of dross is an intrinsic process when melting aluminum alloys. The dross is considered to be the main contributor in influencing the total metal loss during melting. Depending on the efficiency of the melting furnace, and melting practices, the amount of dross generated may be from 1 to 10% of the total metal melted.
In addition to the formation and elimination of dross, another problem that aluminum foundries face in the molten metal bath is the nonmetallic and the metallic impurities that are suspended and floating in the bath. Impurities and aluminum oxides will remain suspended and floating in the liquid bath because they are porous and contain some gas adhering to and trapped in the pores. In this case, the oxide density is similar to that of the aluminum alloy.
Nonmetallic and metallic impurities are introduced into the melt during the charging process, the molten metal treatment, and the handling operations. Even when melting primary ingot, nonmetallic impurities such as hydrogen and aluminum oxide are introduced. However, as would be expected, the majority of the nonmetallic and metallic impurities come from charging returns. The term returns means scrap castings, gates, trimmings, and so on. According to the type and origin of the return metal and the conditions of raw material storage, the metal can contain considerable amounts of both nonmetallic and metallic impurities.
Hydrogen absorption, formation of dross, generation of bifilms, metallic and nonmetallic inclusions, and oxide buildup are inherent characteristics when melting and handling molten aluminum, regardless of the melting and/or holding furnace design or the energy used (gas or electricity). Therefore, it is of vital importance to understand and control such inherent characteristics, because they will greatly affect the quality of the molten metal, which in turn impacts the final casting quality with respect to porosity, shrinkage, oxides, and inclusions.
While the existing types of inclusion material that would be present in melting and holding furnaces and/or transfer ladles will vary from foundry to foundry, their removal is essential for proper molten metal cleanliness. A number of commercially accepted melt treatment techniques are being used by aluminum foundries to remove and separate inclusions from the molten aluminum alloy prior to casting. These include various methods of fluxing, degassing, and filtration in the furnaces and the gating systems (Ref 3, Ref 6, Ref 7, Ref 8, Ref 9, Ref 10, Ref 11).
Any of these techniques will have an impact on the melt cleanliness of the molten aluminum alloy. However, the effectiveness of evaluating their removal would rely on the melt cleanliness measurement technique being used. The strengths and weaknesses of these methods with regard to equipment requirements, sampling, sensitivity, timing, and practical means of assessing inclusion levels on the foundry floor have been fully discussed and published in the literature (Ref 12, Ref 13, Ref 14, Ref 15, Ref 16, Ref 17, Ref 18, Ref 19, Ref 20, Ref 21, Ref 22, Ref 23, Ref 24, Ref 25, Ref 26, Ref 27, Ref 28, Ref 29). Technical articles, which specifically cover fluxing as a factor for ensuring metal cleanliness, have also been published (Ref 7, Ref 30, Ref 31, Ref 32, Ref 33, Ref 34, Ref 35).
In addition to aluminum, fluxing is also commonly done to some extent with virtually all nonferrous mill and foundry melting operations as the first step in obtaining a clean melt. Examples include:
- Fluxing of magnesium alloys using salt fluxes or inert gas as a cover (see the article “Magnesium and Magnesium Alloy Castings” in this Volume).
- Fluxing of copper alloys to remove gas or prevent its absorption into the melt, to reduce metal loss, and to remove specific impurities and nonmetallic inclusions (see the article “Copper and Copper Alloy Castings” in this Volume)
- Fluxing of zinc alloys with chloride-containing fluxes that form fluid slag covers, which can be used to minimize melt loss if they are carefully skimmed from the melt before pouring (see the article “Zinc and Zinc Alloy Castings” in this Volume)
References cited in this section
- R. Fuoco et al., Characterization of Some Types of Oxides Inclusions in Aluminum Alloy Castings, Trans. AFS, Vol 107, 1999 p 287–294
- P. Crepeau, Molten Aluminum Contamination: Gas, Inclusions and Dross, Aluminum Alloy Castings, AFS Fourth International Conference on Molten Aluminum Processing, 1995, p 1–13
- D. Apelian and S. Shivkumar, Molten Metal Filtration — Past, Present, and Future Trends, AFS Second International Conference on Molten Aluminum Processing, 1989, p 14–1 to 14–36
- C. E. Eckert, The Origin and Identification of Inclusions in Foundry Alloys, AFS Third International Conference on Molten Aluminum Processing, 1992, p 17–50
- J. Campbell, Castings, 2nd ed., Butterworth-Heinemann, Oxford, 1988, p 11–26
- D. Apelian, How Clean Is the Metal You Cast? The Issue of Assessment: A Status Report, AFS Third International Conference on Molten Aluminum Processing, 1992, p 1–15
- R. Gallo, Development, Evaluation, and Application of Granular and Powder Fluxes in Transfer Ladles, Crucible, and Reverberatory Furnaces, AFS Sixth International Conference on Molten Aluminum Processing, 2001, p 56–70
- L.C.B. Martins and G.K. Sigworth, Inclusion Removal by Flotation and Stirring, AFS Second al Conference on Molten Aluminum Processing, 1989, p 16.1–16.28
- D.V. Neff, Continuous, Re-Usable Filtration Systems for Aluminum Foundries, AFS Fourth International Conference on Molten Aluminum Processing, 1995, p 121–137
- J.R. Schmahl, L.S. Aubrey, and L.C.B. Martins, Recent Advancements in Molten Aluminum Filtration Technology, AFS Fourth International Conference on Molten Aluminum Processing, 1995, p 71–102
- L.C.B. Martins, Chemical Factors Affecting the Separation of Inclusion from Molten Aluminum, AFS Third International Conference on Molten Aluminum Processing, 1992, p 79–91
- P. Crepeau et al., Characterization of Oxide Sludge, Dross and Inclusions in Aluminum Melting and Holding Furnaces, AFS Third International Conference on Molten Aluminum Processing, 1992, p 51–77
- T.L. Mansfield and C.L. Bradshaw, Ultrasonic Inspection of Molten Aluminum, Trans. AFS, 1985, p 317–322
- D. Doutre et al., Aluminium Cleanliness: Methods and Applications in Process Development and Quality Control, Light Met., 1985, p 1179–1195
- R.I. Guthrie and J.E. Gruzleski, Quantitative Measurement of Melt Cleanliness in Aluminum Silicon Casting Alloys, AFS Fourth International Conference on Molten Aluminum Processing, 1995, p 15–28
- A. Simard, F.H. Samuel, et al., Capability Study of the Improved PREFIL-Footprinter to Measure Liquid Aluminum Cleanliness and Comparison with Different Techniques, AFS Sixth International Conference on Molten Aluminum Processing, 2001, p 93–112
- J.L. Roberge and M. Richard, Qualiflash Apparatus for Testing the Inclusion Quality of Aluminum Alloy Baths, AFS Fourth International Conference on Molten Aluminum Processing, 1995, p 29–42
- E.L. Rooy and E.F. Fisher, Control of Aluminum Casting Quality by Vacuum Solidification Tests, Trans. AFS, Vol 76, 1968, p 237–240
- D. Dispinar and J. Campbell, Critical Assessment of Reduced Pressure Test, Part 1: Porosity Phenomena, Int. J. Cast Met. Res., Vol 17 (No. 5), 2004, p 280–286
- D.E. Groteke, Improve Your Vacuum Test, Mod. Cast. Mag., Aug 2007, p 28–31
- N.D.G. Mountford, I.D. Sommerville, et al., Sound Pulses Used for On-Line Visualization of Liquid Metal Quality, Trans. AFS, 1997, p 939–946
- N.D.G. Mountford, I.D. Sommerville, et al., Laboratory and Industrial Validation of an Ultrasonic Sensor for Cleanliness Measurements in Liquid Metals, Proceedings of International Conference on Cast Shop Technology, TMS-AIME, 2000, p 304–310
- R. Gallo et al., Ultrasound for On-Line Inclusion Detection in Molten Aluminum Alloys: Technology Assessment, AFS International Conference on Structural Casting of Aluminum, 2003, p 29–42
- R. Gallo, Measurement of Hydrogen Content in Molten Aluminum Alloys Using Crucibles and Reverberatory Furnaces for Sand and Permanent Mold Castings, AFS Fourth International Conference on Molten Aluminum Processing, 1995, p 209–225
- F. Painchaud and J.P. Martin, The New Alscan Analyzer: Easy to Use, Reliable, On-Line Measurement of Hydrogen in Liquid Aluminum Alloys, AFS Second International Conference on Molten Aluminum Processing, 1989, p 20.1–20.21
- C. Schwandt et al., A Novel Electrochemical Hydrogen Analyzer for Use in Molten Aluminum and Its Alloys, AFS Sixth International Conference on Molten Aluminum Processing, 2001, p 149–157
- D.E. Groteke et al., Foundry Methods for Assessing Melt Cleanliness, AFS Fourth International Conference on Molten Aluminum Processing, 1995, p 55–69
- D. Dispinar and J. Campbell, “A Comparison of Methods Used to Assess Aluminum Melt Quality,” Shape Casting: TMS, The Second International Symposium, 2007
- D. Apelian and S. Dasgupta, Interaction of Initial Melt Cleanliness, Casting Process and Product Quality: Cleanliness Requirements Fit for a Specific Use, AFS Fifth International Conference on Molten Aluminum Processing, 1998, p 234–258
- K. Strauss, Applied Science in the Casting of Metals, Pergamon, 1970, p 253–256
- M.H. Kogan, Design and Development of Fluxing Agents for the Aluminum Foundry Alloys, AFS Second International Conference on Molten Aluminum Processing, 1989, p 25–1 to 25–12
- T.A. Utigard et al., The Properties and Uses of Fluxes in Molten Aluminum Processing, J. Met., Nov 1998, p 38–43
- S.R. Sibley Granular Fluxes for Aluminum Alloys, Environmental and Technological Advances, AFS Fourth International Conference on Molten Aluminum Processing, 1995, p 417–430
- D. Neff, Ensuring Quality Prior to Pouring, Mod. Cast., June 2006, p 27–29
- R. Gallo, Cleaner Aluminum Melts in Foundries: A Critical Review and Update Transactions, 112th AFS Casting Congress, May 17–20, 2008 (Atlanta, GA)