Page 269 - Fiber Fracture

252 K. Yoshida

The inclusion IS in the die. Di/DO = 0
0.9 -e-
Die,exit
D,ID, = 0.4
0. 8 +
.- 2 0. 7 DiDO = 0.6
3 -+-
E
Q
0. 6 D;/D, = 0.8
-m-
0.5

0. 4

0.3 t- I

2.0 4. 0 6. 0 8.0 10. 0 12.0
Drawing length (mm)

0.i5 0.b 0.?5 1.b
Non-dimensional drawing length
Fig. 11. Drawing stress changes as the inclusion passes through the die.

Size of Inclusions at the Time of Occurrence of Wire Breaks

One report shows the relationship between the occurrence of wire breaks and DilD,
(the ratio of mean diameter of inclusion to wire diameter) of samples (see Fig. 12)
(Arashida et al., 1994). The results show that in the drawing of wires with a diameter of
50 pm or larger, the frequency of wire breakage increases when inclusions with Di/ Do
of 0.6 or higher are included. However, in the drawing of fine wires with a diameter
of 20 pm or less, wire breakage easily occurs even when DilD, is as small as 0.4. In
addition, there seems to be no relationship between the inclusion material and the ease
with which wire breakage occurs.
During the drawing of wires with inclusions, wire breaks occur as a result of a rapid
increase in the drawing stress. The larger the inclusion, the higher the drawing stress,
leading to a higher possibility of wire breakage. These FEA results qualitatively agree
with operational data. However, it is not sufficient to discuss the effects of the wire
diameter on the frequency of occurrence of wire breakage based only on FEA.
Based on the above-mentioned results, the key to preventing wire breaks is the
prevention of the incorporation of large inclusions during both the production of wire
rods and drawing process. The analytical 'data and operational data show that in order to
reduce the frequency of wire breaks, it is important to prevent inclusions with DilD, of
0.4 or greater.