Steels_ Metallurgy and Applications, Third Edition

34 Steels: Metallurgy and Applications

Center Pillar

A-Pillar Reinforcement

odyslde Frame

~ ~.,. Rear Door Inne

Floor Pan

Front Door ........ Inner

Flgure 1.33 Typical tailored blank automotive applications (After HSS Bulletin 56)

the different areas of the pressing. With this technique, it is possible to reduce

the weight and cost of a complete structure since each area of a pressing may be

designed specifically and economically in relation to the required performance

and the need for additional reinforcement or stiffening members is reduced. A

number of typical automotive applications are illustrated in Figure 1.33.

Hydro forming

This is a technique for producing elongated hollow components from a steel tube.
A tube, which may be either straight or bent, is first placed in a forming die.
The tube is then filled with a liquid (usually a water-based emulsion) and then
pressurized which causes the tube to expand and conform to the internal shape
of the die.
The technique may be used to produce complicated hollow shapes that could
not previously be made in one piece by a pressforming technique. Weld seams
are, therefore, reduced in number. The method provides high precision in shape
and may give reduced weight or higher torsional rigidity compared with a similar
component manufactured by welding several subcomponents together. 57
The method is starting to be used in the automotive industry for the manu-
facture of structural components that would previously have been made as box
sections welded together from pressformed components. Applications so far have
included engine cradles, lower and upper longitudinal body rails and various body
crossmembers. 5s
The use of the hydroforming technique is now being extended to cover the
forming of flat sheets as well as tubes.

Roll forming

Roll forming is a technique for continuously converting flat steel into a final

profile by passing it through a series of suitably designed and contoured rolls