New cold-rolled deep-drawing grades

An unstabilised ultra low carbon steel (12 ppm of C) offers an attractive c ombination of formability properties like yield strength, elongation, mean r-value and BH-index. The major drawback is its large planar anisotropy. Th is is attributed to the large grain-size of the hot-rolled product. An incr ease in the cooling rate (using ultra fast cooling technology) or a decreas e in the coiling temperature do not refine the hot-band grain size. However , an optimisation of the cold-rolling and the annealing sequences result in a better balance of the drawing properties. Alloying elements like Cr, B, V, Al, Si or reduction of Mn content exert only a minor influence on the fi nal properties. An addition of Nb (mass contents of 0.01 %) improves the dr awability but decreases the BH-index when conventional continuous annealing temperatures are applied.