Thixoforming : Semi-solid Metal Processing

Temerature (ºC)
1550
1500
1450
1400
1350
1300
1250
1000
titanium was produced to compare rolled and cast primary material, which does not
exhibit carbide bands. In addition, melts with 100 and 250 ppm of Ti were produced
to examine the influence of TiN particles on the structural development. Because the
laboratory melt with 250 ppm Ti showed the same results as the melt with 100 ppm,
in the following only the states rolled , cast and cast þ 100 ppm Ti will be discussed.
The chemical compositions are given in Table 3.5 and the primary structures
are shown in Figure 3.33. The element distribution images in Figure 3.34 show the Ti
(C, N) particles that were formed, which exhibit enrichment with carbon and
nitrogen. In the following, these will be called TiN particles for simplification.
The experimental setup and the temperature–time curve of the quenching
experiments are displayed in Figure 3.35. The temperature of the samples heated
in aluminium oxide pans was measured during the whole experiments by means of a
thermal element in the sample centre. They reached the target temperature after
about 10 min and were held isothermally for 20 min and subsequently quenched with
water and examined metallographically.
The structural images of the quenched samples in Figure 3.36 show an ASTM
grain size of 2 for the rolled material at 1250 C vertical to the rolling direction,
whereas the cast states exhibited considerably smaller ASTM grain sizes of 2 and 4.
500
200
100
1200
0 0.5 1.0 1.5 2.0
C (mass%)
Figure 3.32 Solubility limit of titanium nitride with addition of 50,
100, 200, 500 and 1000 ppm to steel 100Cr6.
Table 3.5 Chemical compositions of the as rolled and as cast state
(all data in mass%, except Ti and N in ppm).
State C Si Mn Cr Mo Ni Al Cu Ti N
Roll 1.08 0.33 0.28 1.47 0.02 0.05 0.03 0.06