An innovation-driven solution for high surface requirements
In the automotive industry, increased energy costs and tightened environmental requirements, lead to a strong market push towards lightweight materials for producing automotive components.
In this context, Constellium has developed a comprehensive automotive body sheet portfolio aiming at answering a key trend of the automotive industry: no compromise between design, environmental and safety benefits.
A key product of this portfolio, SurfalexTM ,is based on a 6016A composition and specifically developed for the most demanding skin application as it provides the best tradeoff between strength, forming, hemming and roping. The product guarantees excellent surface appearance after deep drawing and sharp tornado- lines can be formed without orange peel, despite of the low thickness. 6xxx alloys are often affected by the roping phenomenon and this surface defect translates into the appearance of lines after a certain level of deformation. Roping can be suppressed by controlling all the process parameters including homogenizing treatments, rolling parameters and treatments like solutionizing and or intermediate annealing. Usually, roping is evaluated through typical pictures such as the ones shown on figure below. In addition, a specific software has been developed by Constellium to quantify the roping level, thanks to which the ranking of the samples becomes more accurate. To ensure a very good formability, the isotropy of the material is a key point. Our product exhibits a stable r value in all direction (longitudinal, cross to rolling and 45°), r (r=1/2(r0°+r90°)-r45°)) is DR in all direction is less than 0.1. Last but not least, surface appearance as well as formability are driven by an excellent grain control. Precise fine tuning on process parameters has been carried out to reach a very fine grain size.
SurfalexTM: free of roping line after stretching 15%
6016 : usual products with many roping line after stretching 15%
This very good surface appearance combined with high mechanical resistance level (yield strength after paint baking at 200 MPa) and optimized formability makes it an alloy of choice for premium OEM’s like Audi and Daimler. The picture below present the Audi A3 hood exposed at the Aluminium 2012 fair in Düsseldorf.
Hood Audi A3
Hood Daimler C class
More info:
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