3 Fundamentals of press design

6 Solid forming (Forging)
6.3 Materials, billet production and surface treatment
Materials used in solid forming are mainly unalloyed, low-alloy and
high-alloy carbon steels, non-ferrous light and heavy alloys such as aluminium,
magnesium, titanium and copper and their alloys (cf. Sect.
4.2.2). Significant factors in the selection of materials are formability
(flow stress), the path of the flow curve (cf. Fig. 6.1.5), the permissible
fluctuations in material composition and issues related to billet preparation
including preliminary (heat treatment, coating) and intermediate
treatment.
6.3.1 Materials
Steels
Low-carbon and low-alloy steels are particularly suited for cold forming.
With a carbon content of up to 0.2%, the conditions for forming are very
favorable, up to 0.3% favorable and up to 0.45% difficult, which results in
low formability, true strain and higher press forces. Phosphorus and sulphur
content should remain below 0.035%, as these components tend to
reduce formability. The content of nitrogen is restricted to less than 0.01%
for reasons of susceptibility to ageing. Pre-heat-treated steels can be used for
parts which are sensitive to warping (valve tappet rods) and whose high
strength (upto1,100N/mm 2 ) permit only minimal deformation. In some
cases, micro-alloyed steels containing boron, which permit penetration
hardening, are replacing alloyed steels with the prescribed full heat treatment.
All steels which can be cold formed, can also be warm formed. However,
it should be emphasized that even steels containing a higher carbon
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998