Development of 6xxx Alloy Aluminum Sheet for Autobody Outer Panels: Bake Hardening, Formability and Trimming Performance

In response to requirements of car manufacturers for high volume light weight solutions, Pechiney has developed a range of 6016 variants for outer autobody panels:

• HF100 and HF120, with optimized formability for complex stampings
• DR100 and DR120, with optimized processing for increased bake-hardening response.

Processing of these variants was optimized to minimize surface roughening during forming, necessary for high quality paint finish. Laboratory formability tests (Forming Limits Diagrams, Limiting Dome Height test) showed improved properties for the new 6016 products compared with previous 6016A-T4, particularly in the case of the HF variants. These results were confirmed by full scale stamping validations on a complex part. Excellent hem flanging performance was also demonstrated.

Sliver formation during trimming of stampings was studied in detail. Fine slivers generated by the trimming can accumulate in the stamping tools, resulting in surface defects requiring costly manual rework. Guidelines for trimming tool parameters were established. In addition to the tool variables, metallurgical parameters influence trimming behavior to some extent. The HF and DR variants of Pechiney 6016 improve the robustness of trimming process and consequently the productivity of the stamping lines of high volume aluminum outer autobody panels.