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Green Sand Metalcasting Foundry News

"F" - Glossary of Foundry Additives (including Plumbago Facings)

Posted by Hill and Griffith Company on Feb 6, 2018 3:16:20 PM

F - Foundry Additives Glossary

These are coating materials generally applied to the surface of cores or molds to protect the core or molding sand from the heat, the oxide and the chemical actions of the molten metal. Seacoal, black­ings, carbons, pitch, gilsonite and others are commonly called, "fac­ings." However, these carbons are additives to molding sand mixtures, which in a way, act only like a "facing." (Also See: BLACKING­MOLD COATINGS-PLUMBAGO FACINGS.)

A sand mixture that is used as the interface refractory plane between the metal and the molding sand. It is the closest sand to the pattern and is often especially prepared for specific casting properties.

This is the chemical name given to "iron oxide" or "hematite ore." Its chemical composition is [Fe2O3]. It is abundantly found in nature. Certain of the iron ores are used by the foundry industry as an iron oxide addition. From 0.5% to 6.0% iron oxide is added to sand mixtures. Iron oxides of different trade names generally function completely different in core and melding sand mixtures. The specific gravity of chemical grade ferric oxide varies from 4.0 to 5.2, but the mosi: popular foundry grades have a lower specific gravity and are between 3.0 to 4.5. These oxides contain mineralizers. When iron oxide is used for only its pigment value, it is often called "rouge." Iron oxides vary in color from a brown-red, to a purple-red, to a reddish-black, or even to a black texture. One of the better com­mercial ferric oxides is known as "Klean Surf." Iron oxide (Fe2O3) is non-magnetic and difficult to reclaim from a sand system or heap. Build-up of Wilstite (FeO), ferrous oxide, in the sand system or heap after casting may become a problem, if no new sand additions are made regularly.

1. The quality of the iron oxide is judged by its source, availability, chemistry, pH value, color, screen analysis, bulk density, and its economical value. Specifications should be established on all these properties when ordering.
2. Finely ground iron oxide is a useful inorganic mineral additive giving unique properties to sand mixtures when casting at higher temperatures than 600°F. (316°C.). Iron oxide increases the hot plasticity or hot deformation of the molding or core sand mixtures at higher temperatures. In some cases, it compensates for the high sand expansion created by other materials in the sand mixture. Klean Surf oxide neutralizes sudden volume changes in a sand mixture when heated.
3. The addition of iron oxide to a sand mixture decreases veining, metal penetration or burn-on. Thus, it reduces cleaning costs of the casting.
4. Iron oxide or ferric oxide is not a "cure-all" for poor foundry sand practice. It is a useful mineral when used correctly in 0.5 % to 6.0% additions.


Ferrosilicon is a high silicon alloy of iron made in an electric furnace from charges of silica, iron turnings or borings and carbon. Ferrosilicon is commercially produced in many grades. The silicon (Si) content usually varies from 12% to 75%. 30% ferrosilicon con­tains approximately 68 % iron. Finely ground ferrosilicon is used in certain foundry sand mixtures, with particularly some of the "cold-set," "self-curing," or "fluidized sand" processes. Such mixtures containing ground ferrosilicon offer exothermic action. The more ferrosilicon, the finer it is ground, plus the proper metallic oxides, . the higher the exothermic reaction temperatures in the mixture. The quicker the set­ting time, the faster these self-curing binders must be worked.

A consolidated sedimentary clay of low flux content which is usually associated with coal deposits. It is used as a foundry molding sand bond and as a bonding clay for refractories. Fireclay is essen­tially composed of the mineral, "Kaolinite."

Fish oil is prepared by boiling a variety of marine life such as cod, herring, sardine, salmon, and others. It is obtained by skimming the boiling oil from the hot liquid surface. The specific gravity is about 0.93 and it is often called a "non-drying oil" in the foundry. In the past, it was widely used in the commercial core oil industry as one ingredient. Due to its initial offensive odor, and poorer drying characteristics than certain vegetable oils, other oils have gradually replaced it. Japanese fish oil was a highly desired oil in early core oil formulation. 

Five Star Wood Flour is recommended for use in all types of foundries for improving molding sand and core sand practice. Five Star works well in steel foundries for partial replacement of cereal. It is the best known cellulose to reduce volume changes in foundry sand mixtures at elevated temperatures. In addition, it improves collapsibility of molds or cores, and tends to eliminate certain casting surface defects that may be caused by sand expansion.

Description-Five Star Wood Flour is a specially prepared wood flour. It is not a sawdust which has been ground finer, but is a wood fiber product which has been completely disintegrated and sized to the correct fineness for the foundry.


Reasons for Using
1. To reduce volume changes - this property of Five Star Wood Flour tends to eliminate such defects as scabs, buckles, rat-tails, and veining, which are caused by sand expansion or unequal volume changes in molds or cores. Molding sands which contain wood flour are usually unaffected by rapid thermal shock.
2. To obtain better mold or core collapsibility, so as to avoid hot tears and cracks in castings.
3. To rapidly produce a reducing atmosphere in the mold cavity which tends to improve peeling of the sand from the casting.
4. As an extender for seacoal, cereal, pitch or gilsonite.
5. To reduce lumpy mold or core shake-out conditions and to save sand losses due to these baked lumps of sand.
6. To provide broader temper water limits for synthetic (com­pounded) sand mixtures.
7. To reduce hot compression strength of foundry sand mixtures.
8. To decrease density and increase flowability of sand mixtures, which offers better molding properties.
9. To improve casting finish.
10. To obtain economy by partially replacing cereal, when it is used.
11. Five Star Wood Flour attaches a carbon coating to the sand grains on burning which allows the metal to flow freely over the grains. Metal will not stick to carbon. Carbon is also highly resistant to mineralizers that affect burning-on, thus it reduces casting cleaning costs.

Foundry Applications
A. In Core Sand Mixtures: The addition of 0.5% (by weight) Five Star Wood Flour to a core mixture increases the flow­ability slightly and reduces the baked tensile strength, hot compression strength and lessens volume change of the cores.
B. In Green Sand Mixtures: The addition of 1 % (by weight) of Five Star Wood Flour to a synthetic (compounded) facing mixture produces a slight decrease in green compression strength and which has less density. Such mixtures develop less volume change and improve shake-out properties.
C. In Naturally Bonded Sands: 1 % of Five Star Wood Flour when added to naturally bonded sands tends to overcome sand expansion. It is recommended for use on thin, flat cast­ings which are subject to rat-tails and buckles. For thin sectioned castings, Five Star Wood Flour generates enough gas to improve the sand peeling from the casting without the use of seacoal.
D. As an Extender for Seacoal, Cereal and Pitch: When it is used with seacoal, or partially replaces seacoal, Five Star Wood Flour decreases the dry compression strength. The hot compression strength is greatly reduced. Five Star tends to speed the action of seacoal, since its flash point is lowered. It furnishes a reducing atmosphere almost immediately as the metal enters the mold cavity, and oxidation defects are re­duced to the minimum.
E. When Five Star Wood Flour is used with cereal in a steel foundry's green sand mixture, the ratio is about 0.5% cereal and 0.5% Five Star by weight. Excellent casting results are obtained. In gray iron foundries, if cereal is being used in the facing sand mixture, Five Star Wood Flour may be substituted for part of the cereal. This substitution improves the flow­ability of the mixture and tends to reduce defects caused from excessive sand expansion. Using a combination of wood flour and cereal provides the advantages of each. 
F. When it is used with pitch, the ratio is about ½ lb. of pitch blended with½ lb. of Five Star Wood Flour in a 100 pound sand-clay-water mixture.
G. To improve casting shake-out properties in green, half-topped cores, approximately 1 % Five Star Wood Flour by weight proves beneficial. In steel foundries, up to 2 % Five Star is used in the core backing sand. A lesser amount of Five Star is required in the facing sand, as stated in E

General Information
1. Wood Flour which is ground too finely reduces permeability excessively, while wood flour that is too coarse contributes to the casting's rougher finish. Coarse wood flour absorbs too much water. Coarse wood flours, such as sawdust and others, promote brittle mold edges and cause friable molds. Five Star Wood Flour is ground to foundry proven specifications.
2. The moisture content of green sand mixtures should be in­creased when wood flour is used. It requires an increase of approximately one pint of water for each one pound of Five Star added to the mixture.
3. Excessive additions of wood flour may contribute to a casting cutting and washing.
4. Best results are obtained if wood flour is added to cool sand, not hot molding sand.
5. To obtain the best results, wood flour should contain prac­tically no ash, and should have a low ignition point. Both of these properties are outstanding with Five Star Wood Flour. The wood flour must not be strongly acid (have a low pH value).

Flint is synonymous for silica flour as used in the foundry; how­ever, "Flint" derived its name from usage in the ceramic industry. Ground silica is actually a "silica flour" when used in foundry sand mixtures for cores and mold fine additions.




This is a finely divided product of coal combustion which is col­lected and used in certain core sand mixtures. Fly ash aids flow­ability of the sand mixture, permits castings to peel easier from sand cores. Cores which have deep fins designed in the core box have used fly ash in increments of up to 10% of the mixture. Fly ash is used more widely in aluminum core sand mixtures than for casting ferrous alloys. Fly ash contains fine silica, oxides, and carbon. It is screened for foundry use.

This is a poisonous gas with the chemical composition [HCOH]. It is soluble in water and when combined with phenol and cresol it forms a synthetic resin for use in the foundry industry.


A nomenclature used widely in the foundry which indicates the material is usually carbonaceous and is applied on the surface cf a sand mold or core to prevent the molten metal from attacking the sand. Seacoal has often been referred to as a "foundry facing," but a "foundry facing" should refer only to a coating material and not to "Seacoal." "Foundry Facing Sand" is that sand mixture which is at the mold-metal interface.


Fuel oil is a distillate of oil shale or petroleum. True fuel oil is often termed "Kerosene" and is a liquid hydrocarbon. In many cases, the lighter oils are called "fuel oils." Crude oil may be used in diesel engines with only simple filtration, as this use would be wasteful for the lighter fuel oils. Fuel oils of 28° to 32° Baume used in the foundry industry generally have a B.T.U. content of about 140,000 per gallon and are completely atomized at 90°F. (32.2°C.). Fuel oil is still used in many carbon compounds sold to the foundry industry. However, any oil used as fuel may be correctly designated as a "fuel oil." For many years various foundries have added fuel oil to their molding sand. The amount added per ton of sand mixture varies from one pint to several gallons. Generally, the reason for the addition of fuel oil to a molding sand is to (1) increase the amount of volatiles; (2) replace or re­duce the seacoal or carbons; (3) lubricates; (4) improves flowability of the sand mixture by the presence of the fuel oil which keeps the molding sand moist for a longer period of time; (5) prevents rapid surface and edge drying of the molds; (6) at elevated temperatures ­fuel oil produces an instantaneous reducing atmosphere in the mold cavity. Kerosene is probably used more extensively than reported. Many foundrymen have found that Numbers 1 and 2 fuel oils are better lubricants, as well as being better moisture retarders, in the molding sand. Heavier fuel oils such as Numbers 4, 5 and 6 are better seacoal replacements because, on decomposition they produce higher molecular-weight reducing gases. It is also true that heavier fuel oils provide desired results when a lesser volume is desired. If lack of proper control exists, difficulties can be encountered. The fuel oil content of the sand system can progressively build-up to the-point where the molding sand may ignite and burn-on too rapidly at the shakeout. Excessive use of fuel oil will result in excessive smoke and gas during pouring and at the shakeout. Excessive fuel oil can cause de­fects such as misruns and porosity from too much generated gas, which can be traced to excessive gas created in the mold cavity and not properly vented. When the percentage of fuel oil is maintained at the proper level, excellent castings with clean, smooth surfaces can be obtained. Foundries have used heavier Number 6 fuel oil in sand systems. The use of fuel oils in foundries could grow if the following, or a similar, analytical method is used to determine and subsequently con­trol the percentage of fuel oil present in the molding sand. 

1. Boil 10 grams of dried (moisture free) molding sand for several minutes in a flask with 50 cc of petroleum spirits.
2. Filter the liquid through filter paper and thoroughly wash the re­maining sand with additional petroleum spirits.
3. Collect the filtrate in a weighed beaker.
4. Evaporate the filtrate on a steam bath or hotplate to remove all of the petroleum spirits solvent. (Be careful not to overheat the sample.)
5. Weigh the residue and calculate it as the percentage of fuel oil in the molding sand.

When used in molding sands, fuel oils should be added after the temper water has been mulled into the sand mixture. It should be added at, or near, the end of the mulling cycle. Excessive mulling can destroy some of the advantages of the fuel oil addition, as fuel oil negates the bonding strength of the clay. When properly used, fuel oils improve sand peeling characteristics from the casting. It reduces sand sticking to the pattern and it provides better flowability to mold­ing sands for easier and more uniform ramming. It also prevents rapid sand dryout. 

This is a generic term denoting the basic structure of a family of chemical compounds. Furan is the parent of the compound used to describe this foundry binder. The chemical composition is [C4H3O • CHO (2) J. It is a colorless, odorless liquid which boils at 320 °F. (160 °C.). Furfuraldehyde is produced by a treatment of corn cobs, brans, residues, or other cellulose products with sulfuric acid. Formaldehyde is a disinfectant. Furfuraldehyde is used in the manu­facture of synthetic resins of furfuryl alcohol [C4H3O • CH2OH (2) or (OCH: CHCH: CH) J, as some chemists state. Furan resins are no-bake type resins designed for the production of molds or cores. These resins differ mainly in their nitrogen content. The catalyst used with these resins is usually an 85% phosphoric acid. The amount of acid used depends on the bench life and the speed of cure desired. Furan type accelerated binders contain no phenol.

A group of resins used in the hot box method of binding sand grains for making cores.

Furfural is also known as "furfuraldehyde." It is used as a syn­thetic resin for coring or molding purposes. Its chemical composition is [C4H3O•CHOJ. Its specific gravity is 1.16 and it boils at 320 °F. (160 ° C.). When it is heated it gradually decomposes and turns into a blackish residue, having the appearance of lacquer. It is made by acid treating corn cobs, straw husks, corn stalks, and other such carbo­hydrates. Furfural is used in core sand mixtures and its by-products are used in the manufacture of no-bake cores. There are many com­positions which exist and are used in foundry core rooms. 

Review of "Glossary of Foundry Additives" by Clyde A. Sanders, American Colloid Company

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Tags: Metal Casting, Green Sand Casting Products, Green Sand Foundry Supply, Foundry Supply, Metal Casting Supplies, Foundry Supplies, Green Sand Metal Casting, Green Sand System, Green Sand Metalcasting, Foundry Additives Glossary, Plumbago, Facings

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