Drawing and ironing process

Claim 1

In the method of forming a seamless container body having a sidewall with a smooth outer surface and a bottom wall of a substantially greater thickness than the sidewall from a thin flat blank by progressively bending concentric annular planar segments of said blank into a cylindrical sidewall to form a cup shaped article in a drawing operation and by thinning and elongating the sidewall of said cup-shaped article in more than one ironing operation to form said seamless container body, the improvement which comprises: providing an uncoated low carbon steel blank; forming shallow depressions in at least one surface of said uncoated low carbon steel blank, which will form the outer surface of said cup-shaped article, prior to the drawing operation by sand blasting said one surface with finely divided particulate material, selected from the group consisting of aluminum oxide having a particle size within the range of 80 to 240 grit and sand having a particle size within the range of 50 to 100 mesh, which produces a roughness on said one surface within the range of approximately 70 microinch average RMS with a 320 microinch maximum to 30 microinch average RMS with a 250 microinch maximum; applying a lubricant to said one surface of said uncoated low carbon steel blank prior to the drawing operation for entrapping lubricant in said depressions; and maintaining said depressions at a reduced depth in said outer surface of said cup-shaped article while passing said cup through at least one ironing operation.