University of Pittsburgh produces lead-free steel

Researchers at the University of Pittsburgh's School of Engineering have developed a lead-free alternative to 12L14, a commonly used free machining steel, which could not only eliminate an environmental hazard, but may also offer cost savings. The research was largely supported by an international consortium of steel producers and users.

The university created an international consortium of steel producers and manufacturers to commercialize the technology and has also signed a technology licensing agreement with the consortium. The consortium is a limited liability company (LLC) known as the Nonleaded Free Machining Steel Consortium LLC. The producer members of the LLC will produce the lead-free steel commercially and sublicense it to others. Members include the University of Pittsburgh; United Alloys and Steel Corporation; MacSteel, a division of Quanex Corporation; Curtis Screw Company; Saarstahl Steel AG; and Laurel Steel, a division of Harris Steel Ltd. USS/KOBE Steel Company, which has the option of joining the consortium by July 31, has also provided financial support.

The new steel, termed "green" steel, resulted from researchby Anthony J. DeArdo and C. Isaac Garcia, professors of materials science and engineering at the university. Tin was used as a replacement for the highly toxic lead, which is added to steel to make it easier to machine.

The researchers studied leaded steel using an atom-probe field ion microscope to examine the ferrite grain boundaries in order to determine what the lead did on an atomic level that made the steel more machinable. After selecting tin as the most suitable replacement, the researchers experimented with different ratios of tin in the steel before coming up with the new steel. They found that too much tin made the steel too brittle; too little tin made it harder to machine. The final tin content not only makes the steel more machinable, but also could permit a substantial reduction in the machining cost of the final components.

A test of the final product, completed recently at USS/KOBE Steel Company, found that a 200 tonne heat of the new steel performed well. The new steel is being tested and Milton Harris, chair and chief executive officer of Harris Steel, said the company is encouraged by the test results.

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 competitively available.