Leidel, Dieter S. Harry M. McKinley, M. April Shah, D. Trombly, J. Twarog, D. Metal Casting and Heat Treating Industry. September May Cornett, Michael J. Good information about the Isocycle process.
Discusses cold box sand casting briefly. Douglas, John. This article discusses electric options to replace coal-fired processes. This article discusses the sources of solid waste from foundries. Discusses changes in EPA methods for determining toxicity characteristics of industrial waste. Discussion of air pollution sources from foundries. Ham, R. February, , pp. Discusses the toxicity of liquid foundry wastes. Jacobs Engineering.
Discussion of waste streams associated with foundries. Mosher, Gary E. Discussion of the Hazardous and Solid Waste Amendments of as they apply to foundries. National Renewable Energy Laboratories. Washington, DC: Department of Energy. April, Brief discussion of the industry and the processes. Smith, Virginia D. This article provides a general description of how the Clean Air Act of will potentially affect the foundry industry.
This article discusses waste sources associated with foundries. Trombly, Jeanne. Discussion of foundry air emissions and the Clean Air Act of Northern Precision Castings, Geneva, Wisconsin, is an investment casting operation employing people and casting more than , pounds of metal per month.
The operation uses ceramic molds and wax patterns. The wax patterns must be cleaned thoroughly for proper ceramic adhesion. The cleaner used was the solvent 1,1,1-Trichloroethane TCA which evapoarted to leave the surface clean. The evaporation produced 18, pounds of emissions. They requested alternatives from their solvent supplier.
The supplier's first recommendation was a switch to freon until a better alternative could be identified. The freon produced fewer emission than the than TCP and was used for six to nine months. After that period, freon was replaced with a citrus-based, non-hazardous solvent. The new solvent has been effectively cleaning the wax assemblies with minimal emissions. Product quality was a concern prior to the cleaning chemical switch. However, the change produced no change in mold quality.
Initally, the citrus-based solvent produced an odor the workers found offensive, but the problem has been resolved. The switch from organic solvent cleaners to a citrus-based cleaner has required no capital cost and no signifacant changes in operations and maintenance costs.
The fugitive air emissions prior to the shift were 18, pounds After the move to the citrus-based cleaner, emissions constituted water-soluble liquid waste which can be discharged to the Publicly-Owned Treatment Works POTW. Wolverine Bronze or Roseville, Michigan installed a thermal sand recycling system in an attempt to cut costs of sand purchases. The system produced sand quailty adequate to meet the molding needs; however, the system was not economically beneficial.
As the sand needs at the facilty varied greatly, use of the machine varied. However, the thermal apparatus required constant heat to provide quick start up without damage to the system.
With the heat requirements, the thermal sand recycling operation did not save signficant amounts of money over the purchase of new sand. In , low energy sand recycling sytems were evaluated to replace the thermal system. An attition sand recovery system was installed. In the attition system, sand grains rub together at high speeds to remove residual binders and inorganic contamiants. The system has produced signifant cost savings over the use of new sand. The primary savings stems from reduced energy and maintenance requirements over the thermal recovery system.
Quinn Machine and Foundry of Boone, Iowa produces concrete pipe forms our of iron. Slag from the cupola furnace was being produced at a rate of approximately 8, pounds per day. Quinn sought to reduce the slag production and, in turn, reduce thier volume of waste. They first attempted to locate a metal recovery operation for the slag. However, metal recovery did not prove economical for the facility. After further evaluation, it was determined that a smaller charge in the furnace would increase the yield and reduce slag formation.
The change has resulted in the predicted reductions. The pattern is removed after the mold or impression has been formed and then the metal is introduced through a runner system to fill the cavity.
The sand and the metal is then separated and the casting cleaned and finished for shipment to the customer. The majority of castings produced in the United States are specifically engineered parts, custom designed for unique applications. Castings in general are not commodities like, for instance, bearings or fasteners, where one style might be used in many applications.
Generally speaking, most castings are made to order with close tolerance levels required to meet a customer's strict requirements. Copious washing with water will help to avoid the problem. Cold-setting no-bake hardening systems presently in use include: acid-catalyzed urea- and phenol-formaldehyde resins with and without furfuryl alcohol; alkyd and phenolic isocyanates; Fascold; self-set silicates; Inoset; cement sand and fluid or castable sand.
Cold-setting hardeners do not require external heating to set. The isocyanates employed in binders are normally based on methylene diphenyl isocyanate MDI , which, if inhaled, can act as a respiratory irritant or sensitizer, causing asthma.
Gloves and protective goggles are advisable when handling or using these compounds. Most general housekeeping principles should be strictly applied to resin moulding processes, but the greatest caution of all should be exercised when handling the catalysts used as setting agents. The catalysts for the phenol and oil isocyanate resins are usually aromatic amines based on pyridine compounds, which are liquids with a pungent smell. They can cause severe skin irritation and renal and hepatic damage and can also affect the central nervous system.
These compounds are supplied either as separate additives three-part binder or are ready mixed with the oil materials, and LEV should be provided at the mixing, moulding, casting and knockout stages. For certain other no-bake processes the catalysts used are phosphoric or various sulphonic acids, which are also toxic; accidents during transport or use should be adequately guarded against.
Many variations of the CO 2 -silicate process have been developed since the s. This process has generally been used for the production of medium to large moulds and cores. The core sand is a mixture of sodium silicate and silica sand, usually modified by adding such substances as molasses as breakdown agents. After the core box is filled, the core is cured by passing carbon dioxide through the core mixture. This forms sodium carbonate and silica gel, which acts as a binder. Sodium silicate is an alkaline substance, and can be harmful if it comes into contact with the skin or eyes or is ingested.
It is advisable to provide an emergency shower close to areas where large quantities of sodium silicate are handled and gloves should always be worn. A readily available eye-wash fountain should be located in any foundry area where sodium silicate is used.
The CO 2 can be supplied as a solid, liquid or gas. Where it is supplied in cylinders or pressure tanks, a great many housekeeping precautions should be taken, such as cylinder storage, valve maintenance, handling and so on. There is also the risk from the gas itself, since it can lower the oxygen concentration in the air in enclosed spaces.
The Isocure process is used for cores and moulds. This is a gas-setting system in which a resin, frequently phenol-formaldehyde, is mixed with a di-isocyanate e. This is injected into the core box and then gassed with an amine, usually either triethylamine or dimethylethylamine, to cause the crosslinking, setting reaction.
The amines, often sold in drums, are highly volatile liquids with a strong smell of ammonia. There is a very real risk of fire or explosion, and extreme care should be taken, especially where the material is stored in bulk. The characteristic effect of these amines is to cause halo vision and corneal swelling, although they also affect the central nervous system, where they can cause convulsions, paralysis and, occasionally, death. Should some of the amine come into contact with the eyes or skin, first-aid measures should include washing with copious quantities of water for at least 15 minutes and immediate medical attention.
In the Isocure process, the amine is applied as a vapour in a nitrogen carrier, with excess amine scrubbed through an acid tower. Leakage from the corebox is the principle cause of high exposure, although offgassing of amine from manufactured cores is also significant. Great care should be taken at all times when handling this material, and suitable exhaust ventilation equipment should be installed to remove vapours from the working areas.
After the molten metal has cooled, the rough casting must be removed from the mould. This is a noisy process, typically exposing operators well above 90 dBA over an 8 hour working day. Hearing protectors should be provided if it is not practicable to reduce the noise output.
The main bulk of the mould is separated from the casting usually by jarring impact. Frequently the moulding box, mould and casting are dropped onto a vibrating grid to dislodge the sand shakeout. The sand then drops through the grid into a hopper or onto a conveyor where it can be subjected to magnetic separators and recycled for milling, treatment and re-use, or merely dumped.
Sometimes hydroblasting can be used instead of a grid, creating less dust. The core is removed here, also sometimes using high-pressure water streams.
The casting is then removed and transferred to the next stage of the knockout operation. The sand gives rise to hazardous silica dust levels because it has been in contact with molten metal and is therefore very dry. The metal and sand remain very hot. Eye protection is needed. Walking and working surfaces must be kept free of scrap, which is a tripping hazard, and of dust, which can be resuspended to pose an inhalation hazard.
Relatively few studies have been carried out to determine what effect, if any, the new core binders have on the health of the de-coring operator in particular.
The furanes, furfuryl alcohol and phosphoric acid, urea- and phenol-formaldehyde resins, sodium silicate and carbon dioxide, no-bakes, modified linseed oil and MDI, all undergo some type of thermal decomposition when exposed to the temperatures of the molten metals. No studies have yet been conducted on the effect of the resin-coated silica particle on the development of pneumoconiosis. It is not known whether these coatings will have an inhibiting or accelerating effect on lung-tissue lesions.
It is feared that the reaction products of phosphoric acid may liberate phosphine. Animal experiments and some selected studies have shown that the effect of the silica dust on lung tissue is greatly accelerated when silica has been treated with a mineral acid. Urea- and phenol-formaldehyde resins can release free phenols, aldehydes and carbon monoxide.
The sugars added to increase collapsibility produce significant amounts of carbon monoxide. No-bakes will release isocyanates e. Casting cleaning, or fettling, is carried out following shakeout and core knockout. The various processes involved are variously designated in different places but can be broadly classified as follows:.
Sprue removal is the first dressing operation. As much as half of the metal cast in the mould is not part of the final casting. The mould must include reservoirs, cavities, feeders and sprue in order that it be filled with metal to complete the cast object. The sprue usually can be removed during the knockout stage, but sometimes this must be carried out as a separate stage of the fettling or dressing operation. Sprue removal is done by hand, usually by knocking the casting with a hammer.
To reduce noise, the metal hammers can be replaced by rubber-covered ones and the conveyors lined with the same noise-damping rubber. Hot metal fragments are thrown off and pose an eye hazard. Eye protection must be used. Detached sprues should normally be returned to the charging region of the melting plant and should not be permitted to accumulate at the despruing section of the foundry.
After despruing but sometimes before most castings are shot blasted or tumbled to remove mould materials and perhaps to improve the surface finish. Tumbling barrels generate high noise levels. Enclosures may be necessary, which can also require LEV. Dressing methods in steel, iron and non-ferrous foundries are very similar, but special difficulties exist in the dressing and fettling of steel castings owing to greater amounts of burnt-on fused sand compared to iron and non-ferrous castings.
Fused sand on large steel castings may contain cristobalite, which is more toxic than the quartz found in virgin sand. Airless shot blasting or tumbling of castings before chipping and grinding is needed to prevent overexposure to silica dust. The casting must be free of visible dust, although a silica hazard may still be generated by grinding if silica is burnt into the apparently clean metal surface of the casting. The shot is centrifugally propelled at the casting, and no operator is required inside the unit.
The blast cabinet must be exhausted so no visible dust escapes. Water or water and sand or pressure shot blasting may be used to remove adherent sand by subjecting the casting to a high-pressure stream of either water or iron or steel shot.
Sand blasting has been banned in several countries e. The water or shot is discharged through a gun and can clearly present a risk to personnel if not handled correctly. Blasting should always be carried out in an isolated, enclosed space. All blasting enclosures should be inspected at regular intervals to ensure that the dust extraction system is functioning and that there are no leaks through which shot or water could escape into the foundry.
It is advisable to post a notice on the door to the booth, warning employees that blasting is under way and that unauthorized entry is prohibited. In certain circumstances delay bolts linked to the blast drive motor can be fitted to the doors, making it impossible to open the doors until blasting has ceased. A variety of grinding tools are used to smooth the rough casting.
Abrasive wheels may be mounted on floor-standing or pedestal machines or in portable or swing-frame grinders. Pedestal grinders are used for smaller castings that can be easily handled; portable grinders, surface disc wheels, cup wheels and cone wheels are used for a number of purposes, including smoothing of internal surfaces of castings; swing-frame grinders are used primarily on large castings that require a great deal of metal removal.
Production in the steel foundry as distinct from a basic steel mill is similar to that in the iron foundry; however, the metal temperatures are much higher.
This means that eye protection with coloured lenses is essential and that the silica in the mould is converted by heat to tridymite or crystobalite, two forms of crystalline silica which are particularly dangerous to the lungs.
Sand often becomes burnt on to the casting and has to be removed by mechanical means, which give rise to dangerous dust; consequently, effective dust exhaust systems and respiratory protection are essential.
The light-alloy foundry uses mainly aluminium and magnesium alloys. These often contain small amounts of metals which may give off toxic fumes under certain circumstances. The fumes should be analysed to determine their constituents where the alloy might contain such components. In aluminium and magnesium foundries, melting is commonly done in crucible furnaces. Exhaust vents around the top of the pot for removing fumes are advisable.
In oil-fired furnaces, incomplete combustion due to faulty burners may result in products such as carbon monoxide being released into the air. Furnace fumes may contain complex hydrocarbons, some of which may be carcinogenic. During furnace and flue cleaning there is the hazard of exposure to vanadium pentoxide concentrated in furnace soot from oil deposits. Fluorspar is commonly used as a flux in aluminium melting, and significant quantities of fluoride dust may be released to the environment.
In certain cases barium chloride has been used as a flux for magnesium alloys; this is a significantly toxic substance and, consequently, considerable care is required in its use.
Light alloys may occasionally be degassed by passing sulphur dioxide or chlorine or proprietary compounds that decompose to produce chlorine through the molten metal; exhaust ventilation and respiratory protective equipment are required for this operation.
In order to reduce the cooling rate of the hot metal in the mould, a mixture of substances usually aluminium and iron oxide which react highly exothermically is placed on the mould riser.
When the fumes are brown in colour, alarm may be caused due to suspicion of the presence of nitrogen oxides; however, this suspicion is unfounded.
The finely divided aluminium produced during the dressing of aluminium and magnesium castings constitutes a severe fire hazard, and wet methods should be used for dust collection. Magnesium casting entails considerable potential fire and explosion hazard. Molten magnesium will ignite unless a protective barrier is maintained between it and the atmosphere; molten sulphur is widely employed for this purpose.
Foundry workers applying the sulphur powder to the melting pot by hand may develop dermatitis and should be provided with gloves made of fireproof fabric. The sulphur in contact with the metal is constantly burning, so considerable quantities of sulphur dioxide are given off.
Exhaust ventilation should be installed. Workers should be informed of the danger of a pot or ladle of molten magnesium catching fire, which may give rise to a dense cloud of finely divided magnesium oxide. Protective clothing of fireproof materials should be worn by all magnesium foundry workers. Clothing coated with magnesium dust should not be stored in lockers without humidity control, since spontaneous combustion may occur. The magnesium dust should be removed from the clothing.
French chalk is used extensively in mould dressing in magnesium foundries; the dust should be controlled to prevent talcosis. Penetrating oils and dusting powders are employed in the inspection of light-alloy castings for the detection of cracks. Safety-conscious design and protective equipment help reduce the risk to workers and equipment, but the real key to safe casting operations is skilled foundry workers with excellent situational awareness, strength and endurance.
Castings are produced in foundries all over the world. Conditions vary from country to country and even from foundry to foundry, but the industry as a whole is experiencing trends. There are significant changes taking place in the foundry industry that affect quality and cost for the end user. Foundry technologies have developed over the years and the core foundry business has also evolved and diversified.
The most dominant general trends are scale, automation and in-house finishing. The new furnaces are larger, safer and more efficient than previous generations. This allowed for an increase in industrial production despite the steadily declining number of foundries in North America. MTS gathered worldwide Casting manufacturers into this online platform. Browse and search for your next supplier with us.
Quick Link to Suppliers. International Manufacturing Teletrading Sources IMTS is your key to unlock the door to the industry from anywhere around the world, at any time. Home Blog What is a Foundry? Casting Zone Find products best meets your needs. No more worries about the authenticity of suppliers. Find Suppliers. What is a Foundry? Posted on Aug 3, Foundries are plants engaged in the production of metal castings and services related to foundry The metal is tapped from the foundry furnace into the deluge ladle A foundry is a factory where metal is melted and cast into new shapes Foundries are responsible for our current standard of living and industrial development, but most of us know almost nothing about them.
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