The Forming of Vanadium Bearing HSLA Steels into Automotive Components 740180
The newest grades of hot rolled, high-strength low-alloy (HSLA) steels, characterized by an ultrafine grain size (ASTM 11-13), exhibit an excellent combination of strength (50,000-80,000 psi yield strength) and ductility. Various formability tests demonstrate that these steels are highly formable in spite of their high strength. Compared to mild steels, plane strain and stretch deformation characteristics of HSLA steels are reduced by only 25-40%. In the drawing mode deformation, HSLA steels perform similarly to mild hot rolled steels. Because of higher strength, the ductility of sheared work-hardened edges is low and sensitive to inclusion shape. When sheared edge deformation is necessary, the cracking tendency can be substantially reduced by converting stringer inclusions into globules.
HSLA steels have been formed into various components on dies originally designed for mild steels, indicating that with somewhat more generous contours the steels can be used effectively for mass production. Current failure limit diagrams are inaccurate for grid analysis of hot rolled steel parts; new diagrams are needed which will reflect strain gradients in the thickness direction.