Green Sand Metalcasting Foundry News

Now is the time to be look at newer sand reclamation technologies, to reduce cost and environmental impacts, and to enhance casting quality.

Most everyone realizes that sand reclamation is necessary for cost reducing and environmental requirements. While the popularity of sand reclamation certainly resulted from increasing sand prices (caused primarily by the demand for fracking), there are few processes that provide as many immediate benefits as sand reclamation.

Reducing the cost of sand is by far the most attractive consideration for sand reclamation, though lowering disposal and transportation costs are equally attractive. Couple these with reducing your environmental footprint and you realize that reclaiming sand is just good business.

One of the most overlooked benefits from sand reclamation is quality assurance. Controlling your materials through an in-house system will enhance the quality of your castings; because better sand makes better castings.

Excerpt from the January 2013 Foundry Management & Technology article.

"Core cost averaging" and allowing foundries to do what they do best

Many foundries believe that they can produce cores merely for the price of sand and resin. That would be an ideal way for any business to operate, but the truth is that coremaking expertise carries a cost. At Humtown Products we have spent hundreds of hours calculating costs and striving to become the most efficient core room in the country, which now allows us to deliver quality cores across the country, on time, every time.

To foundries that believe buying cores from expert suppliers is too expensive we reply, "core cost averaging." If your foundry is falling behind on coremaking efficiency and you fear losing a customer, try this: Build us a box. Let us run some of the cores, and your core room can run as many as possible. This will allow you to ship the order and lower the average cost of cores. Foundries are in the business to pour metal, and no molding lines should be idled because there are no 'affordable' cores ready to set.

Excerpt from the September 2019 Foundry Management & Technology article.

Top and bottom sand-blowing system extends the Hunter expertise with a new option for foundries' mold-filling needs.

The science of sand molding has not changed for centuries, but the process technologies involved in mold production are another matter. In that case, the changes are demand-driven. Molding machinery is developed to suit the production requirements of foundries, and foundries know where to turn for molding technology expertise.

Hunter Foundry Machinery Corp. has been innovating and refining molding machinery for more than half a century, famously with the Hunter HMP machine that introduced the "matchplate" concept that made green-sand molding faster, more reliable, and more cost-effective, and allowed foundries of all types to be competitive in terms of volume and product quality. It is a rugged, gravity-driven system that’s easy to operate and easy to understand; it is scalable to foundries’ available space; and it adapts easily to different foundries’ molding operations.

Excerpt from February 2009 Foundry Management & Technology article by Nobuyoshi Sasaki.

A novel concept uses sodium and silica to increase the heat resistance of organically bonded molds and cores, which increases hot strength and allows the production of thin-wall castings.

Historically, foundries worldwide have been forced to rely on organic-based core and mold binders, and the use of refractory coatings, along with sand additives, when the hot strengths of the binders are insufficient to produce salable castings.

In 1995, Cadic Corp., and its subsidiary CTI Inc., introduced the Cadic Convert Process, which uses a liquid mixture of silicon oxide and sodium in alcohol to treat resin-bonded molds and cores. In practice, cores and molds produced using organic heat- and amine-cured resins were dipped or immersed in the ethanol solution, dried, and subsequently fired in a kiln to convert the organic-bonded article to an inorganic bonded mold or core.

This post-production treatment of organic-bonded aggregates resulted in the formation of organo-silicates that were converted to ceramics when fired at elevated temperatures, and poured hot to produce thin-wall (2 mm or less) stainless steel castings.

Laboratory evidence, supported by foundry trials, confirmed that the silica compound formed a crystal lacuna surrounding the sodium (Na) at room temperatures and allowed the Na ion to retain its high degree of reactivity.

The subsequent high-temperature treatment resulted in the conversion of quartz to tridymite, thereby increasing the high-temperature properties of the core or mold.

Because of the high degree of reactivity, the Na ion is utilized in this process as the alkali oxide Na₂O. In this new process, the nano silica composition allows the Na ion to maintain its reactivity from room temperature to the boiling point of the compound.

With the elimination of a post-production treatment for the core or mold using ethanol as a carrier, the resulting new development makes the Cadic Convert Process considerably simpler, because the nano silica compounds can be added to the sand mix prior to the production of the core or mold in any organic resin-bonded processes, such as phenolic urethanes and shell sand mixtures.

A new water-based reclamation process offers foundries a method for recovering bentonite and carbon from foundry dust.

Excerpt from the March 2020 Foundry Management & Technology article.

Despite numerous challenges to its long-term viability — some serious and credible, others just imagined or mistaken — green sand casting is thriving, both in practical terms and in its technological progress. But one constant dilemma for producers of green sand castings is what to do with the byproducts.

For background, green-sand casting involves molds formed with silica (or chromite, or zircon) sand mixed with water and bonding compounds, notably bentonite (clay) and carbon. Finished castings ultimately leave their molds but the bonded sand remains, and what to do with that sand is one of those challenges that green-sand casters routinely discuss. Reportedly, the U.S. foundry industry consumed approximately 700,000 tons of bentonite and carbon during 2018.

Today's foundries cannot afford to sacrifice the efficiency and profits that are the consequences of poorly controlled hot molding sand.

Excerpt from the June 2004 Foundry Management & Technology article by FM&T Staff

Metalcasting researchers say hot sand is the leading sand-related problem for today’s foundries. Most metalcasters recognize a relationship between reduced casting quality, increased process variation, and other molding inefficiencies that result from using hot molding sands. Studies show that hot sand affects virtually every operation in the production line.

System sand returned to the muller for reconditioning with a temperature of 160°F (approximately 70°C) or greater is considered to be excessively hot. Return sand ranging from 120° to 160°F (approx. 49°-70°C) is hot enough to demonstrate inconsistent properties during mixing and to be very difficult to control.

A global consortium of metalcasting companies, resin and coating suppliers, additive and sand suppliers, and researchers, aims to spread the word for CPR casting porosity reduction.

Abstract from the June 2007 Foundry Management & Technology article by Charles E. Bates and Robert Burch

According to a recent survey of 121 product engineers, design engineers, metallurgists, laboratory personnel, and others associated with the design, production, and use of castings, the metalcasting industry's greatest need for improvement lies in eliminating porosity in castings. By consensus, this applies to aluminum, gray iron, and ductile iron, and to all types of steel castings. The distribution of quality issues based on this broad survey is illustrated in Figure 1. Concerns over porosity rated twice as high as any other issue in the survey.

A consortium of companies around the world is being formed to address this concern, led by AlchemCast L.L.C. The consortium is known as the Foundry Casting Porosity Reduction (CPR) Consortium, and to assure the future success of castings as structural components in engineered products, a kick-off meeting for foundries and suppliers was held in Birmingham, AL, April 12-13, 2007.