3 Fundamentals of press design

Materials, billet production and surface treatment
content, for example from 0.45 to 1.0%, can be easily formed, i.e.
without costly intermediate heat treatment. Inductive hardening steels
such as Cf 53, Cf 60 and the ball bearing steels 100 Cr 6 are classical
examples of application for warm forming. For practice-oriented calculation
of force and energy requirements, a good approximation for the
flow stress curve for hot forging can be obtained by multiplying the cold
forging flow curve values with a factor of 0.3 to 0.5.Figure 6.3.1indicates
the temperature-dependent variation of the flow stress curves for Ck 15
and Cf 53.
Table 6.3.1 provides a summary of the most important steel material
groups. It lists not only the DIN and Eurostandard designations but also
the abbreviations for similar materials in accordance with the American
AISI and A.S.T.M standards as well as with the Japanese JIS standard.
The last column provides information on whether the steel is suitable
for hot forming (H), warm forming (W) or cold forming (C). For more
information on workpiece materials, please refer to DIN worksheets
17006, 17100, 17200, 17210, 17240, 17440. Flow stress curves for cold
forming are given in the VDI Guidelines 3134, 3200 sheet 2 (ferrous
metals) and sheet 3 (non-ferrous metals).
flow stress k [N mm ]
f
6
material k material f 3
= s - = s -
0,2 0,4 0,6 0,8 1,0 0,2 0,4 0,6 0,8 1,0
truestrain [-]
Fig. 6.3.1 Temperature-dependent flow curves Ck15 and Cf 53
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998
°
°
6 °
7 °
°
6 °
7 °
°
°
°
451