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Advanced High-Strength Steels (AHSS) have become an essential part of the lightweighting strategy for automotive body structures. The ability to fully realize the benefits of AHSS depends upon the ability to aggressively form, trim, and pierce these steels into challenging parts. Tooling wear has been a roadblock to stamping these materials. Traditional die materials and designs have shown significant problems with accelerated wear, galling and die pickup, and premature wear and breakage of pierce punches. [1] This paper identifies and discusses the tribological factors that contribute to the successful stamping of AHSS. This includes minimizing tool wear and galling/die pick-up; identifying the most effective pierce clearance (wear vs. burr height) when piercing AHSS; and determining optimal die material and coating performance for tooling stamping AHSS.

In an effort to improve the dent resistance of exterior body panels at reduced steel thicknesses, some automobile manufacturers have pursued the application of bake hardenable steels. Unfortunately, bake hardenable steels have only been available as cold rolled or with electro-zinc or electro zinc/iron coatings. This situation has been a deterrent for those automobile manufacturers that prefer the use of hot dip galvanneal coatings. Recently, the interest in hot dip galvanneal bake hardenable steels has led to the investigation and development of this more advanced steel grade. This paper presents the results of a stamping trial and dent testing on three exposed hot dip galvannealed materials; i) Regular Ultra Low Carbon (ULC), ii) Rephosphorized ULC, and iii) Rephosphorized Bake Hardenable ULC steel.