University Times

Profs develop "green" steel

Engineering school researchers have developed a lead-free steel that they say has a potential $1 billion-plus worldwide market.

"The elimination of lead from free machining steel has been one of the Holy Grails of materials science and engineering," Anthony J. DeArdo said. His research with fellow materials science and engineering professor Isaac Garcia led to development of the new "green," or more environmentally friendly, steel.

Lead, a health hazard, is added to steel to make it easier to machine. Working at Pitt's Basic Metals Processing Research Institute, DeArdo and Garcia replaced the lead with tin — not only eliminating an environmental pollutant, the researchers said, but also offering savings on environmental and machining costs.

"The key was asking the right question," DeArdo said. "We started with the scientific approach, asking: 'What does the lead do, on an atomic level, that makes the steel more machinable?"

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," DeArdo said, "the answer was obvious to us." He and Garcia decided that tin was the most suitable replacement for lead, and 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 made it harder to machine.

Pitt has licensed the lead-free steel to an international consortium that includes United Alloys & Steel Corp. and Curtis Screw Co., both of Buffalo; MacSteel of Fort Smith, Ark.; Germany's Saarstahl Steel, AG; Laurel Steel of Ontario, and the University itself.

A patent for the new steel is expected to be issued to the University this month. Currently, the most common use of free machining steel is in automobile parts.

Pitt and the lead-free steel's inventors will share in profits from its sales. Arthur A. Boni, director of the University's Office of Technology Management, declined to estimate how much money Pitt stands to earn, but said: "Certainly, we expect this to be a significant revenue generator for the University."

–Bruce Steele