JFE Steel Corporation and ThyssenKrupp Steel AG of Germany have 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. Initial components made of the new material confirm its advantages. The two companies have jointly filed a patent on the newly developed material.
JFE Steel and ThyssenKrupp Steel have been working together closely since 2002 under a cooperation agreement aimed at securing the global availability of high-performance steel materials for the automotive customers of both partners. Results to date include the definition of common specifications for high-strength automotive steels and the conclusion of a cross-licensing agreement for the steel grades NANO HITEN™ from JFE Steel and CP (complex phase) from ThyssenKrupp Steel. Under the agreement, both companies can produce the other partner’s products.
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.
Further joint developments for high strength steels are anticipated in future.