Steel is one of the most important construction materials with a long tradition, which has been continuously improved in its properties. More than half of the approximately 2,000 steel grades included in the steel iron list are less than 6 years old. Increasing lightweight construction requirements resulting from heightened environmental awareness, legal requirements and increasing customer demands are fuelling competition between materials.
Today, multiphase steels and manganese-containing steel grades are increasingly used.
In total, up to 64 per cent higher- and high-strength steels are used in current bodyshells. The fact that these also include numerous parts that are complex in terms of forming technology shows that the limits for the use of higher-strength steel materials in automotive production have been considerably expanded. The advantage of multiphase steels lies in their outstanding strengths with good forming properties. Compared to the use of conventional steels, they allow a reduction in the sheet thickness of the component while maintaining the same strength, which makes a considerable weight reduction achievable. If the designers’ main focus is on the realisation of complex components with high strengths, high-strength and higher-strength dual-phase and retained austenite steels are used thanks to their excellent forming properties. If the focus is primarily on crash resistance, ultra-high-strength complex-phase and martensite-phase steels offer maximum strength with good formability.
Areas of application for modern multiphase steels include:
- Dual-phase steels for difficult structural components; also for stretch-drawn exterior parts with special buckling resistance (e.g. doors, roofs).
- Retained austenite steels for structural components with particularly high energy absorption capacity (e.g. columns, longitudinal beams).
- Complex-phase steels for parts with pronounced crash relevance and simple geometric requirements (e.g. reinforcement of the A-pillar in a convertible).
- Martensitic phase steels for parts with pronounced crash relevance (e.g. side impact beams).
The high-manganese steels that are currently being used more and more are characterised by their high strength combined with high ductility and are thus far superior to conventional steels. Thus, strength values of over 1600 MPa are achieved with elongations at break of 70-20% (USIBOR).
More information, especially on the weldability of these new steel grades, is available as always from your Harms & Wende partner. Source: www.stahl-info.de