Vehicle manufacturers are increasing their use of high- and ultra-high strength steels, and so steel manufacturers are increasing their portfolio of products in this arena. One of the latest is a multiphase steel developed by Thyssen Krupp Steel of Germany (http://www.thyssenkrupp-steel.com/en) and JFE Steel of Japan (http://www.jfe-steel.co.jp/en). This steel has a minimum strength of 780 MPa, which is similar to steels offered by both of the companies, but which is said to have 40% higher elongation compared with most 780-MPa materials. This means improved formability.
The strength and formability of the new material, designated TP-N 68/78, are based on a bainitic-ferritic microstructure with embedded retained austenite in combination with nanometer-sized precipitations. During the forming operation, the austenitie content is transformed into a hard martensite. In other words, it reaches its final strength as a result of the forming operation.
The two companies have been working together since 2002. In addition to co-developing this new steel, ThyssenKrupp and JFE have cross-licensed the production of high-strength automotive steels.