3 Fundamentals of press design

470 Solid forming (Forging)
Table 6.5.1: Process limits of the most important extrusion methods taking into account
economical die life
NF-materials
steels
Process
material
aluminium (e.g. Al99,5),
lead, zinc
copper (E-Cu)
brass
(CuZn37-CuZn28)
easy to form
(e.g. QSt32-3, Cq15)
limiting
value
difficult to form
(e.g. Cq35, 15MnCr5)
more difficult to form
(e.g. Cq45, 42CrMo4)
Forward rod extrusion Forward tube extrusion Backward cup extrusion
(h 0 /d 0) (h /d )
max 0 0 max (h /d )
A max max
A max max
A min A max
0.98
0.85
0.75
0.75
0.67
0.60
h 0
4
1.9
1.4
1.4
1.1
0.9
d 1
d 0
10
6
4
0.98
0.85
0.75
0.75
0.67
0.60
2 1 max
dimensions are greater than these values, free or open die extrusion must
be used as a supplementary extrusion process. In addition, the ratio h 0/d 0
in the remaining (non-extruded) portion of the billet must be no smaller
than 0.5. Otherwise, the so-called “suck-in” defects may occur.
The maximum true strain achievable with the forward rod extrusion
of steel is around � = 1.6 depending on the material. In the case of
materials with low formability, this value is as low as 0.5 to 0.9. The die
opening angles 2 � [°] must be within a range of approx. 45 and 130°,
which results in tapers on the formed part with angles between 22.5
and 65°.
The part volume is calculated from the individual volumetric values
as illustrated in Fig. 6.5.1:
s 0
h 0
V0 = V1 + V2 + V1',
whereby V , V , V ' and V are
calculated by means of
0 1 1 2
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998
4
1.9
1.4
1.4
1.1
0.9
d 0
15
12
8
s 1
h 0
0.10
0.12
0.15
0.15
0.25
0.35
0.98
0.80
0.75
0.75
0.65
0.60
d 0
d 1
6
4
3
3
2
1.5
s 1
h 2