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This paper will describe an investigation of the formability of high strength steel (HSS) laser welded blanks (LWBs). Anticipated combinations of thickness and steel grades, including high strength low alloy (HSLA) and dual phase (DP) steels were selected. The blanks were characterized through chemical analysis and mechanical testing, as well as microstructural analysis of the weld. Samples were strained in a limiting dome height tester. Weld line movement, dome height and strain at failure were then measured. Data from these tests resulted in development of forming limit diagrams, and allowed correlation of weld line movement to forming conditions. In part, the results showed that the presence of the weld has a negative influence on formability, and that balancing the load carrying capacity of each side of the blank results in minimum weld line movement in the blanks.

Continuing pressure to reduce mass and cost of vehicles is driving the development of new high strength steel products with improved combinations of strength and formability. Galvanized, cold rolled dual phase steel products are new alternatives to conventional high strength low alloy (HSLA) steel for strength limited applications in vehicles. These steels have higher tensile strengths than HSLA products with nearly equivalent formability. This paper compares the performance of HSLA and dual phase sheet steel products in a series of drop tower tests. Samples were prepared by stamping the steel sheets into typical rail-type parts using a production-intent die process. The parts were sectioned, and subsequently fabricated into hat-shaped assemblies that were then dynamically crushed by a drop weight. The experiments were designed such that the entire energy input by the drop weight was absorbed by the samples.

Continuing pressure to meet fuel economy and safety requirements, improve quality and minimize cost has resulted in new challenges for auto industry engineers. New sheet metals for auto body stampings have helped the transportation industry meet these challenges. The steel industry has developed a number of new products for these purposes, including dent resistant steels for outer body panels, high strength steels for structural applications and interstitial free (IF) steels for difficult forming challenges. The aluminum industry is also aggressively pursuing new applications. New aluminum products have been applied to closure panels, resulting in significant mass reductions in several high volume vehicles. Stamped aluminum for structures have also been developed and commercialized, albeit for lower volume production. This paper will discuss these new materials and the benefits and challenges they present.