Stronger, Tougher Steel Variety Developed

(Library of Congress)

Engineers at Wayne State University in Detroit developed a new type of steel that they say is stronger and more resistant to fracture, and can also resist the fatigue encountered with similar materials. The work of engineering professor Susil Putatunda, leading this research group, is supported by National Science Foundation, Michigan Initiative for Innovation and Entrepreneurship, and the heat-treatment metals company Applied Process Inc. in Livonia, Michigan.

Putatunda’s work involves a type of heat treatment of metals called austempering that produces a structure in iron and steel considered stronger and tougher than comparable structures produced with conventional heat treatments. Putatunda says this third generation advanced high strength steel has several advantages over steels currently being used in industry today.

“Our steel has twice the yield strength, has a very high tensile strength, and is close to three times the fracture toughness over advanced steels currently on the market,” notes Putatunda. “In addition, it has improved strength for fatigue and impact, improved durability, lower weight, and the austempering process reduces energy consumption and eliminates the post-treatment process.”

Putatunda’s research group devised what is called a bainitic steel, with a grain refinements and hardening to meet higher impact and fatique performance. The group’s new material has a finer microstructure with ferrite and carbon-stabilized austenite, a non-magnetic combination of ferrite and carbon, as well as silicon.

When put through an austempering process, say the engineers, it produces a a structure that is stronger and tougher than other types of steel. Austempering offers a more energy efficient heat treatment process that does not require post-heat treatment, thus the potential as well for energy savings.

One application for this new type of steel is armored vehicles. The metal has already been through independent ballistic tests in Canada, with reportedly good results. “The steel has been found to have the strength and durability necessary for armored vehicles to resist improvised explosive devices because of its extremely high fracture toughness,” says Putatunda. “Our steel could potentially save human lives against explosive attacks.”

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