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 n what
could be one of the most important innovations in steel making
in the past 30 years, researchers at the University of Pittsburgh's
School of Engineering have developed a lead-free alternative
to 12L14, a free-machining steel commonly used throughout the
world. The new steel resulted from research by Anthony J. DeArdo
and C. Isaac Garcia, professors of materials science and engineering
at Pitt. According to DeArdo and Garcia, their new steel is not
only more environmentally friendly, but potentially can be machined
more easily than leaded steel.
 DeArdo and
Garcia used tin to replace the highly toxic lead, which is added
to steel to make it easier to machine. The new product, which
they term "green steel," not only eliminates an undesirable
environmental hazard, but it may also offer cost savings.
A patent for
the new lead-free steel was filed by the University of Pittsburgh
and is expected to issue this month. The University, through
the Office of Technology Management, created an international
consortium of steel producers and manufacturers to commercialize
the technology.
A test of
the final product, completed recently at USS/Kobe Steel Company,
found that a 220-ton heat of the new steel performed well. The
new steel is presently being tested, and Milton Harris, chairman
and CEO of Harris Steel, said the company is encouraged by the
test results to date. The market for 12L14 steel is between two
and three million tons per year, and at approximately $500 per
ton, the worldwide potential market is $1 billion-plus for the
lead-free steel.
Not only is
the lead environmentally undesirable, but it adds production
costs as companies need to implement environmental controls to
the manufacturing process. Arthur A. Boni, Pitt's director of
technology management, estimates that the "green" steel
has the potential to save on environmental and machining costs.
"Ever
since governments began asking steel manufacturers to reduce
their use of lead, researchers have been trying to come up with
alternatives," said DeArdo. And the major users of free
machining steel are also interested. The most common use for
the steel is in automobile parts, and Harris noted that major
automakers in the United States and Germany have indicated a
desire to use lead-free steel if it were competitively available.
While other
researchers have experimented with different steel alloys, DeArdo
and Garcia used another tack. "The key was asking the right
question. We started with the scientific approach, asking, 'What
does the lead do, on an atomic level, that makes the steel more
machinable?'," DeArdo said.
The researchers
studied leaded steel using an atom probe field ion microscope
to examine the ferrite grain boundaries. "Once we saw what
the lead did, the answer was obvious to us," DeArdo said.
The researchers
decided that tin would be the most suitable replacement for the
lead, then experimented with different ratios of tin in the steel
before coming up with their new product. They found that too
much tin made the steel too brittle; too little tin made it harder
to machine. The final tin content chosen not only makes the steel
more machinable than the existing leaded steel, but also could
permit a substantial reduction in the machining cost of final
components. 
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pitt.edu or John Fedele, (412) 624-4148; fedele