Technical sessions break through.

Notable Technical Reports

* Aluminum could be the prominent metal choice in future diesel cylinder heads.

* Residual aluminum improves ductile iron without causing pinhole defects.

* In-mold ductile iron treatment offers primarily gray iron metalcasters versatility.

* Copper alloys kill illness-causing bacteria.

* Cellulose in place of seacoal can reduce defects without harmful emissions.

* Renewable energy applications will be the next great boom in metalcasting sales.

* Businesses employing illegal immigrants are at greater risk for prosecution after new legislation.

The Technical Sessions of the 2007 Metalcasting Congress offered numerous breakthroughs in metalcasting research, as well as comprehensive reviews of the state of the industry. Presented below are some of the practical findings of the 56 sessions offered to conference attendees.

Can Aluminum Go Diesel?

A new study by researchers at Alcan, Voreppe, France, has shown that improved properties can be achieved in aluminum engine cylinder heads with a modified alloy, bringing them one step closer to becoming a viable component in diesel engines.

Because of their large displacement and high levels of torque, diesel engines have remained the last stronghold of iron engine castings. But the introduction of aluminum into the cylinder heads of diesel engines would significantly reduce their weight and resulting fuel economy. For this reason, researchers have for some years been searching for ways to achieve the appropriate properties from aluminum. The Alcan study, titled "Improved Aluminum Alloys for Common Rail Diesel Cylinder Heads" (07-022) and presented Wednesday by M. Garat and G. Laslaz for the AFS Aluminum Div., represents the latest step in that search.

"The new [alloy] seems to yield a far more important gain in elevated temperature properties, especially at 300C, combined with good ductility and high RT fatigue strength," the researchers said. "This set of properties seems to be promising for the resistance to both thermal and mechanical fatigue in common rail diesel heads."

While the experiments on the alloy have been performed only in a controlled setting, the researchers believe that the next step will be to test the metal in actual diesel cylinder heads.

Residual Aluminum Takes Effect

Residual aluminum can improve the characteristics of ductile iron without inducing pinhole defects, said I. Riposan, M. Chisamera and S. Stan, Politechnica Univ. of Buckarest, Romania, and D. White, Elkam Metals Inc., Pittsburgh.

In "The Role of Residual Aluminum in Ductile Iron Solidification" (07-008), the researchers described how residual aluminum can "decrease free carbide occurrence, increase nodule count and improve casting compactness without affecting graphite morphology."

The researchers also said that adding aluminum with an inoculant produces the best results, followed by including it in the base iron.

Engineering a Semi-Solid Solution

One of the most significant road-blocks to the success of semi-solid casting, particularly with magnesium, has been the development of accurate simulation software that takes into account non-Newtonian principles, but a new study has developed a program that accurately predicts the filling pattern of semi-solid magnesium.

"The simulation results showed that the semi-solid magnesium alloy filled smoothly at the beginning but began to assume a divergent, fork-like flow front when the slurry started to fill the circular front of the casting [Fig. 1]," said R. Weng, J. Kuo and W. Hwang, National Cheng Kung Univ., Tainan, Taiwan, and C. Loong and C. Jen, Industrial Materials Institute National Research Council, Canada, during a session of the Engineering Div.

[FIGURE 1 OMITTED]

Experimental results, discussed in the paper, "Mold Filling Simulation of Semi-Solid AZ 91D Magnesium Alloy" (07-122), showed that those findings accurately described reality.

Not Expansion, Contraction

Several researchers found a new source for veining defects in metal castings produced in sand molds, saying that imperfections occur not when silica sand reaches peak thermal expansion, but when it subsequently contracts.

Typical belief has been that veining defects, fins of metal protruding from a casting surface, occur when core or mold surfaces develop a crack from thermal forces or mechanical handling. However, in a presentation for the Molding Methods and Materials Div., J. Thiel, Univ. of Northern Iowa, Cedar Falls, Iowa, M. Ziegler, Unimim Corp., Rockford, Ill., P. Dziekonski, Fairmount Minerals Inc., Wedron, Ill., and S. Joyce, Badger Mining Corp., Berlin, Wis., said on Wednesday that new measurement equipment enabled discovery of the new source. Previously available testing equipment led researchers to believe that veining defects in sand castings resulted from a spike in thermal expansion at 1,063F (573C). Fig. 2 shows the standard thermal expansion curve for common metalcasting sands.

[FIGURE 2 OMITTED]

"No matter how low the peak expansion was, we still would [find] veining defects in test castings," the researchers said in their paper, "Investigation Into the Technical Limitations of Silica Sand Due to Thermal Expansion" (07-145). "Sands that showed a reduced contraction and/or a secondary expansion [rather than a contraction] yielded fewer veins when used in test castings."

In-Mold Treatment, Miniaturized

Three speakers in the Cast Iron Div. announced Wednesday that they have developed a modified in-mold treatment technology for the production of small ductile iron castings. According to F.R. Juretzko, Univ. of

Alabama, Tuscaloosa, Ala., J. Hitchings, Comanche Technologies, Downington, Pa., and D.M. Stefanescu, Ohio State Univ., Columbus, Ohio, a new riser-type insert, which includes a pouring basin, reaction chamber, choke area and filter, can be placed in a pattern for the production of ductile iron castings with a total casting weight of about 45 lbs. (20.4 kg). Prior approaches to ductile iron production primarily had been performed only in large batches of several hundreds to thousands of pounds. When in-mold treatments were applied, a controlled and sophisticated alloy chamber and gating system had to be designed for each application.

"In order to increase the versatility of a [metalcasting] product line, in-mold treatments present a practical way to offer ductile iron products, even though the main product line might be gray iron," the researchers said.

With some redesigning of the initial insert, as described in "A New Modified In-Mold Treatment of Ductile Iron Production Using a Direct-Pour Container Technique" (07-046), the researchers say they also were able to develop the technology for use with thin wall ductile iron castings.

Copper's Antimicrobial Characteristics

Copper alloys recently have been discovered to kill illness-causing bacteri, according to a presentation for the Copper Div. by H. Michels, vice president of technical and information services at the Copper Development Association (CDA), New York.

In his presentation "Antimicrobial Testing of Cu Alloys Required by U.S. EPA," Michels said recent studies have shown that copper-base alloys can eliminate 99% of infectious bacteria on its surface, and the CDA currently is working with the U.S. Environmental Protection Agency (EPA) to register copper alloys as having antimicrobial properties. This registration would mark the first time the EPA has recognized a material, rather than a solution or gas, as having these properties.

To make the health claim to the EPA, five types of bacteria were tested on five alloys in 3,000 samples. The results of the tests revealed that the copper alloys wipe out at least 99% of disease-causing bacteria over the course of 90 minutes. The EPA has until Sept. 4 to respond to the claims.

Developing a Coating for Magnesium Permanent Mold

V. Lafay and S. Robison presented previously unpublished information on the success of magnesium casting in low-pressure permanent mold on Tuesday, distilling the nature of the coating used to two main points--any commercially viable coating for magnesium permanent mold casting must use a fluoride rich filler/refractory, and a two coating approach is preferred.

Magnesium has offered metalcasters the unique capabilities of a lightweight metal with good fluidity. While it has been used in diecasting and sand casting, its broad use in permanent mold and low-pressure casting has been limited due to difficulties in finding successful mold coating materials and practices.

However, the search for a production-capable permanent mold coating for use with magnesium has developed considerably in the past two years, stemming from the successful casting of a structural magnesium engine cradle in 2004. In "Selection and Application of Permanent Mold Coatings for Magnesium Casting" (07-022), presented in the sessions for the Magnesium Div., Lafay and Robison described the necessity of fluorspar at 2% or less of the final application coating, as well as the nature of the bottom and top coatings that were needed for the casting of the cradle. The bottom coating, which functions something like an undershirt, was formulated traditionally, with a silicate binder, water as a carrier, traditional filler/refractory materials and the optional addition of red iron oxide. The top coating--representing the tailored button down the outside world encounters--"was formulated without a silicate binder, with fluorspar, water as the carrier liquid and organic additives."

"This resulting coating used in the magnesium low-pressure casting trials met or exceeded the expectations of the project team," the researchers said.

Basin May Reduce Steel Defects

A new pouring basin design may reduce surface defects in steel metal castings, according to a study for the Steel Div. presented Thursday by S. Kuyucak and based on his paper, "Clean Steel Casting Production--Evaluation of Laboratory Castings" (07-102).

In ongoing work funded under the U.S. Department of Energy's Energy SMARRT Program, Kuyucak found that the problem was that bottom pouring steel ladles produced entrained air that ended up on the surface of finished castings. The solution was to fit the ladles with a specially-designed basin to increase the steel's exposed surface area over time during pouring. The basin was used to accommodate a submerged ladle nozzle extension that had previously been designed to fit into an existing side riser.

"If the premise that turbulence in the mold cavity caused by the entrained air is the major contributing factor to casting surface defects, then the new pouring basins should result in significant improvements," Kuyucak said.

The one drawback to the basin is that its cooling effects require castings to be poured at a higher superheat than traditional bottom poured castings. However, this would not present a problem in large industrial castings, Kuyucak said.

Cellulose Offsets Lack of Seacol

The addition of cellulose to green sand mixtures can offset the appearance of expansion defects when seacoal is removed to reduce hazardous air pollutants (HAPs), said V. Lafay, Hill and Griffith Co., Cincinnati, Ohio, and G. Crandell, Technikon LLC, Sacramento, Calif., at a session of the Environmental, Health and Safety Div. on Wednesday.

Seacoal has been determined to be a prime suspect in the production of HAPs by green sand metalcasters, and with environmental regulations becoming ever stricter, the additive must be reduced to become environmentally friendly. But seacoal has long been known to be beneficial in reducing casting defects. Metalcasters must come up with some substitute to offset the loss.

"Since the addition of cellulose does not negatively impact the emission characteristics, as shown in a recent Casting Emission Reduction Program report, it is an ideal additive to prevent and/or reduce expansion defects," the researchers said in their paper, "The Addition of Cellulose to Molding Sand When Reducing Seacoal for Emission Reduction During Pouring, Cooling and Shakeout" (07-021).

As shown in Table 1, sand mixtures with cellulose in place of seacoal have been shown to reduce emissions of hazardous air pollutants (HAPs), VOCs and POMs.

By surveying several Midwest operations, the researchers found that metalcasters have removed up to 40% of their seacoal content without increasing scrap by offsetting the subtraction with a 1-3% addition of cellulose.

Cellulose also has shown improved water absorbing properties over seacoal.

Renewable Energy: The Next Great Casting Demand

Renewable energy applications will require a significant number of castings in the coming years, according to a presentation by M. Swartzlander and D. Hays, Ashland Performance Materials, Dublin, Ohio.

"Sustained high energy prices, driven by the global economy, have created a booming market for castings," the researchers said. "Castings for the oil field, gas wells and transmission infrastructure, rail cars for coal and mining are in great demand."

Working from a paper titled "The Coming Boom in North American Casting Demand From Renewable Energy Applications" (07-099), the speakers said that alternative energy markets, such as wind, solar, geothermal and bio power, have created additional need for castings and will result in the increase over normal levels of casting demand in the energy market. One megawatt of wind power requires an investment of $24,000 in cast metal components (Fig. 3); bio power uses $21,000 in cast metal parts per megawatt.

[FIGURE 3 OMITTED]

According to Swartzlander and Hays, the government could offer tax credits and portfolio standards to influence the growth of renewable energy sources, but lobbying on the part of the industry will be necessary.

Decriminalizing Your Workforce

The current legislative session on Capitol Hill will change the way in which law enforcement deals with illegal immigrant workers, and small businesses, including metalcasters, should do everything they can to avoid prosecution, according to Human Resources Div. presentations given by J. Lopez, attorney for Littler Global, Miami, Fla., and J. Shofi, U.S. Department of Homeland Security.

The newly created U.S. Immigration and Customs Enforcement (ICE) agency already has begun prosecuting businesses that are egregious employers of unregistered immigrants, Shofi said. However, a new program has been created to help existing employers identify and remove illegal members of their payroll. Businesses of all sizes are invited to join in a relationship with the agency to establish best practices for assuring a registered workforce.

Lopez, who presented his paper "Umm ... Papers! What Papers?: Immigration Compliance and Reform" (07-175) immediately following Shofi, warned metalcasters that "the ICEman cometh," and prosecutions against businesses harboring illegal workers will increase in the succeeding years.

Should You Put Aluminum in Your Cupola Charge?

Adding aluminum to a cupola charge at low levels could induce a reaction that would reduce the amount of coke and silicon that are needed, but more research is necessary before the treatment can be considered practical, according to a recent study.

In a presentation of the Melting Methods and Materials Div. on Tuesday, G. Case, Dalton Corp., Kendallville, Ind., and W. Nicola, Dalton Corp., Warsaw, Ind., expressed their hope that aluminum could reduce costs associated with cupola melting without inducing casting defects. The idea seems counterintuitive, as aluminum has been associated with the formation of casting porosity. However, at levels of 0.1-0.2%, the researchers believed the addition of the metal could produce an exothermic reaction that could improve alloy recovery, carbon pickup, tap temperature and metal chill. Increased carbon recovery would result in lower coke usage; increased alloy recovery would lower the need for silicon and manganese. And a reduced chill level would lessen inoculation usage.

However, like some vaccines in humans, the aluminum can produce ill effects before those benefits are realized.

"A higher third level (0.3%) aluminum addition rate was tested for one hour, and casting porosity resulted," Case and Nicola said. "Additional testing at this higher level was aborted due to the potential for producing significant quantities of casting scrap."

The research, which was documented by the authors in "The Effect of Aluminum in the Cupola Charge" (07-056), did not result in a definitive answer at this time, but the low level aluminum treatment showed "indications of the potential for lower coke and silicon additions." Therefore, the researchers believe that if more can be learned about the formation of aluminum induced porosity, the addition of aluminum to cupola charges could result in significant cost savings for operators.

Rapid Prototyping Brings in Revenue Fast

By introducing rapid prototyping and short run technology, metalcasters can reduce lead times and time to-market, thereby increasing their revenue stream, a panel of speakers for the Pattern and Foundry Tooling Div. said Tuesday.

C. Fischer, Wisconsin Precision Casting Co., East Troy, Wis., M. Grebe, Becker CAD-CAM-CAST, Southfield, Mich., T. Becker, AC Tech North America Inc., Ann Arbor, Mich., and L. Andre, Solidiform, Ft. Worth, Texas, offered slide show presentations on various methods of developing rapid tooling and prototypes to meet the demands of customers requiring fast response and short lead times.

Table 1. Effect of Cellulose on Sand Mixture Emissions

                   PCS-Test FK Sand System     PCS-Test GL Sand System
                   Average with Seacoal and     without eacoal (with
                    Release Agent (lb/ton      Cellulose) and Release
                        metal poured)         Agent Only (lb/ton metal
                                                       poured)

Emission Results
Sum of VOOs                  0.43                       0.09
Sum of HAPs                  0.34                       0.09
Sum of POMS                  0.02                       0.002