Thixoforming : Semi-solid Metal Processing

Figure 6.44 Simulation grid of cooling channel process.
the container. This is due to the convection eddies (Figure 6.46f) and the low
temperature gradient inside the container. The temperature and correspondingly
the liquid fraction are slightly high at the upper middle of container because of the
dual insulation at the metal surface due to the air and the isolating cover of the
container.
The temperature, solid fraction and grain density were monitored during fluid
flow over the channel and recorded as shown in Figure 6.47. At the middle of the
channel (CP1 in Figure 6.44), the temperature of the metal is slightly higher, and
the corresponding solid fraction is considerably lower, compared with those at the
channel outlet (CP2), where the metal cut a longer distance on the cooled channel.
The average temperature difference between CP1 and CP2 after 1.5 s was about
16 C, whereas this difference decreased to about 2 C as the inlet velocity increased to
0.2 m s 1 . The overall temperature rise for both points after 4.5 s was about 3 C due
to heating of the channel inside wall. The impact of this temperature increase on the
solid fraction is also obvious in Figure 6.47a. The grain density in Figure 6.47b has a
Figure 6.45 Liquid fraction in cooling channel process 3.7 s after metal pouring.
6.3 Simulation of Cooling Channelj211