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JFE Steel Corporation and ThyssenKrupp Steel AG of Germany have jointly developed a new multiphase steel for automotive applications. It has a minimum strength of 780 megapascals (MPa), similar to that of the advanced ultrahigh-strength steels CP-W 800 from ThyssenKrupp Steel and NANO 780 from JFE Steel. But with up to 40 percent higher elongation compared to conventional 780MPa HSS steel, it possesses significantly improved forming properties.
The high strength and good formability of the newly developed 780MPa HSS are attributable to a bainitic-ferritic microstructure with embedded retained austenite in combination with nanometer-sized precipitations. During forming, the austenite content is transformed into hard martensite, which means that the steel reaches its ultimate strength during fabrication into the finished part. To achieve these specific properties, the materials developers at JFE Steel and ThyssenKrupp Steel developed a new alloying concept and also employed new temperature control methods during hot rolling and cooling.
The newly developed 780MPa HSS is available as hot-rolled coil and, by request, galvanized coil. Typical applications include crash-relevant automotive body structural parts.
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