Dual phase steel
|
DIN EN 10346 |
|---|---|
| Area | Materials |
| title | Continuously hot-dip refined and electrolytically refined strip and sheet made of multiphase steels for cold forming |
| Brief description: | Technical delivery conditions |
| Latest edition | 2009-07 |
| ISO | - |
DP steel ( dual-phase steel ) refers to all steels whose structure consists of a ferritic (soft) matrix in which a predominantly martensitic (strength-increasing) second phase is embedded in the form of islands at the grain boundaries. The proportion of martensite is between 10 and 40%. With a higher proportion of martensite, a greater tensile strength can be achieved, but the elongation at break is reduced. This structure has a relatively low and therefore favorable yield point for the forming process as well as high tensile strength , elongation and n-value . These properties are advantageous for complex deep-drawn parts. In addition, DP steel has a pronounced bake hardening effect . Typical application examples for these steels are flat, stretched profiles in car doors, strength-relevant support structures and energy-absorbing components as well as steel rims.
The idea of manufacturing dual-phase steels goes back to the 1970s. The industrial production of DP steels began in the 1990s.
To produce DP steel, the two-phase area must first be heated or cooled. Then you wait until the desired proportions of austenite and ferrite have set. It is then cooled down quickly, as a result of which the austenite component is converted into martensite. The process can take place from the rolling heat by cooling from the γ region (marked with a blue point in the figure) into the two-phase region or by heating from room temperature to the α + γ region (marked with a red star in the figure).
Hot-rolled dual-phase steels are particularly suitable for the lightweight construction of rims, chassis parts, profiles, body reinforcements, etc. Cold-rolled dual-phase steels are suitable for difficult structural parts such as longitudinal and cross members as well as for stretch-drawn external parts with special requirements for dent resistance (doors, Roofs, trunk lids). The selection of the type of steel to be used for a certain strength level must also be made with particular attention to the deformation stress that is actually to be expected. In this way, the advantages can be used and the steels can also be used for difficult drawn parts.
The dual-phase steels are standardized in the European standard EN 10346 (formerly EN 10336). They are not to be confused with duplex steels , which are made up of equal parts of ferrite and austenite.
Web links
- [1] Table of contents of DIN EN 10346: 2009-07 at Beuth-Verlag
Individual evidence
- ↑ Dual-phase steel: product range - thyssenkrupp. Retrieved December 12, 2017 .