CWC Textron invests in the promise of advanced vacuum casting.
process; * spectrographic metal
analysis developed in
collaboration with the Univ
of Michigan; * the first Ford V-8 and Lincoln
Zephyr V-12 motor
blocks castings were
poured at CWC Textron; * the first camshafts for
Roland E. Oldsmobile's
automobile were cast at
Today, CWC Textron is the source of another foundry first that has emerged after a decade of what can be described as the worst 10 years in the foundry industry's history. Advanced vacuum casting is the result of the company's determination and vision. Accomplishment in a Time of Distress
The 1980s were hardly the years most foundries chose to begin investing heavily in research and development. By 1982, total U.S. castings shipments had declined to a 40-year low of 11 million tons. Nearly 1000 domestic casting plants ceased operating from 1982-1988.
Although CWC Textron was not an exception to the troubles facing the industry, company president John L. Kelly also was faced with another challenge. The largest producer of camshafts in the world, CWC Textron was a foundry devoted to gray iron, the predominant material of choice for North American car manufacturers.
But CWC Textron executives had heard about Detroit's plan to shift to "roller lifters," a valve train system that would apply a new level of stress to camshafts. Roller lifters could mean that camshafts would now generally be manufactured in steel as opposed to the traditional gray iron around which CWC Textron's business was built.
Kelly responded to this challenge by developing a "steel strategy" for the company and began working on several new technologies. "We were committed to making CWC Textron a center of valve train expertise - a commitment that's as strong as ever today," Kelly said.
CWC's energies were focused on four technologies. The first was chilled iron that was widely used in camshafts throughout most of Europe and the Pacific Rim. The second was ductile iron, which had found a niche in Europe and was being used by Chrysler and some Japanese carmakers. The third technology was selectively austempered ductile iron, (SADI) which was tinder scrutiny by numerous companies.
As CWC enters the '90s, it is supplying chilled iron camshafts to major European automakers and is expanding its ductile iron capabilities.
The fourth technology Kelly pursued was advanced vacuum casting This casting method uses conventional, chemically bonded sand cores and molds. But unlike traditional gravity fill methods, the assembled mold is partially immersed, in the casting furnace and the molten alloy is ingested (by creation of a vacuum) into the mold through gates in the bottom of the drag.
This new process seemed to offer several advantages, including: * near net shape configurations; * thin wall sections (to 1.75 mm); * a group of steel alloys that had
been difficult or impossible to cast
conventionally; * a cost-effective finished casting with
a quality metallurgical structure.
The process appeared to be ideal for castings where weight reduction, high performance and cost-accountability were critical. But before extensive work in advanced vacuum casting began, the potenfor widespread use of "roller lifters" that initiated Kelly's aggresgive push for new technologies had diminished. Kelly found himself with a "process in search of a problem" and a decision to be made that would have an impact on the company's future.
Kelly's options were straightforward, On one hand, he could write off the entire experience and be content with continuing successes in the camshaft business. On the other hand, he could move ahead with this largely unexplored area of advanced vacuum casting by upping the ante. Kelly's decision came down to long-term survival. He began a $6 million investment in advanced vacuum casting without a market or a customer.
Enough work had been completed to show Kelly and his people the enormous potential vacuum casting offered. Initial work concentrated on successfully building advanced vacuum cast camshafts for Ford racing cars. Largescale production was not cost-effective at that time. Breakthrough Opportunity
As research and development continued, a unique opportunity presented itself in 1987. Mercury Marine/ Fond du lac, Wi, was experiencing corrosion failure problems with a water-cooled exhaust elbow in its stern drive motors. The iron casting being used was not effecfive in a hostile saltwater environment. Dr. Raymond J. Donahue, Mercury Marine's director of advanced materials engineering, believed that a duplex stainless steel, combined with the advanced vacuum casting process, could solve the problem.
For CWC Textron's research group, the elbow-a multi-cored, complex shape-offered an exceptional challenge.
"Mercury Marine provided an opportUnity for us to look at advanced vacuum casting from a non-automotive, non-camshaft point of view," recalls John C. Wallfred, CWC Textron's vice president of engineering. "It also forced us to develop a completely different mental discipline. Despite the fact that our group had several centuries of combined experience in the foundry business, in many respects it was like starting all over."
CWC Textron's team made many changes to accommodate the new thinking required of advanced vacuum casting. A separate production facility was established. Discussions with the union representing the company's employees resulted in new job classifications and new relationships. People with diverse experience were hired in the research and development area while a new product development team was established.
In November 1989, CWC Textron received a three-year, 200,000 part order commitment and began to supply advanced vacuum cast exhaust elbows to Mercury Marine. The new part is 65% lighter than the cast iron component it replaces and offers reduced machining requirements and extended part life. Future Programs
With numerous prototype projects under way at varying stages, the future for CWC Textron and advanced vacuum casting is very bright. Some of the programs now entering production include a turbocharger and automotive bracket assembly.
According to Dr. Robert Blackburn, CWC Textron's manager/material development, the turbocharger application is especially consistent with the performance characteristics of the process.
"The tremendous heat generated and the 'can't fail' performance required have previously required the use of alloys with high nickel content D2 through D5S," Blackburn said. Advanced vacuum casting makes it possible to use materials once considered difficult, if not impossible, to cast. And by eliminating or reducing the nickel content, we can reduce costs while improving metallurgical integrity, weight reduction and performance."
The second application involves an automotive bracket that replaces a stamped sheet metal and weldment assembly. "This particular bracket demonstrates the expanded design envelope and the near-net-shape capabilities of this process," Blackburn said.
Other potential parts include automotive control arms, steering links and brackets, as well as valve, offshore drilling equipment and pulp and paper industry machine components.
"We're just beginning to fully understand the potential advanced vacuum casting offers," said Paul 0. Warren, CWC Textron's advanced vacuum casting process manager. New Processes, New Approaches
Progress on the advanced vacuum casting process has been significant, according to Warren. Until now, casting research and development called for improvements to existing operations and materials,' he said. The advanced vacuum casting process requires a completely different approach-emphasizing new materials such as duplex stainless steel and more applied research and new product development.'
As a result, this old-line castings company finds itself with an exciting new technology generated largely by an emphasis on research and development. "Sufficient technological advances exist at the present time to maintain and increase our competitiveness as an industry," Warren said. 'Our challenge lies in our ability to adapt our organization structurally and culturally, to the rapidly changing, customer-driven environment.'
Today, Kelly sees a CWC Textron that is different in many ways. Much of this difference can be attributed to significant investments in research and development, new technologies and facilities. "Casting is actually a growth industry again," Kelly said.
As the company's advanced vacuum casting facility approaches capacity next year, this technology has proved to be commercially successful.
"The advanced vacuum casting market is infinite and so are the businesses, the industries and the materials with which we're working," Kelly explained. "It's an exciting time to be in the foundry business." Advanced Vacuum Casting
Molds are made using conventional chemically bonded cope and drag machines. The flaskless 26 x 26 x 8 in. mold must be sufficiently rigid to be self supporting. Coring is done using traditional methods with increased dimensional demands resulting from the newly attainable complex, thin-walled geometries.
The vacuum is applied across the entire top surface of the cope, about one-third of an atmosphere, drawing uniformly through the porosity of the mold. Two objectives are accomplished: first, the mold is rapidly and completely filled and the gasses are evacuated from the cavity. Each cavity is individually fed by ingesting metal through gates in the bottom of the drag, eliminating sprues, runners and the unpredictability of interdependent feeding.
Individual gating and risering permits consistent and appropriate feeding of the entire casting with minimum turbulence. Additionally, the yield is moderately increased over conventional gravity fed methods. Furnace
Casting occurs in a uniquely designed (approximately 4 x 1 ft., 1800 kg [4000 lb]) induction heated casting furnace. This furnace is supplied continuously by two 2700 kg (6000 lb) inert gas shrouded induction melt furnaces. Since casting takes place in the furnace, the alloy need not be excessively heated to compensate for the ladle transfer process. Ingestion temperatures are about 10C (50F) above liquidus and are controlled at [+ or -]2C (10F).
CWC Textron developed the refractory materials and lining practice to hold molten metal about 1600C (2912F) for long periods in an induction furnace. This technology permits continuous, efficient casting. Relatively low casting temperatures and minimum turbulence contribute to metallurgical integrity, improved surface finish and dimensional stability. Process
The advanced vacuum casting process at CWC Textron uses microprocessors and internally developed software. Without these, it would not be commercially possible to direct, control and monitor the entire manufacturing process from raw materials to completion.
Assembled molds move at a rate of 85/hr from the assembly area to the vacuum head. The combination robot arm vacuum head rotates 180 degrees after picking up a mold from the assembled mold line to the casting furnace and back.
As the mold is lowered into the metal, numerous events are computer actuated including: activating the depth of immersion based upon transducer feedback, varying the electromotive field in the casting furnace and timing the dwell. The entire cycle takes about 45 seconds.
Inherent in the real-time controls and sensors of advanced vacuum casting is the statistical process control of manufacturing. Variables such as temperature, alloying elements and gas chemistry, ingestion rate and fluid dynamics are known, monitored and controlled.
The result is castings that expand the design envelope, possess quality metallurgical integrity, are highly consistent in measurable attributes and cost-effectiveness.
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|Title Annotation:||includes related article about vacuum casting|
|Author:||Thomas, Susan P.|
|Article Type:||Cover Story|
|Date:||Dec 1, 1990|
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