Thixoforming : Semi-solid Metal Processing

Table 10.2 Definition of boundary conditions of the cooling process (ABAQUS).
Temperature of environment Tsurrounding ¼ 25 C
Temperature of tools Ttool ¼ 300 C
Convective heat transmission Hsurrounding ¼ 10 W m 2 K 1
Heat transfer a tool component ¼ 5000 W m 2 K 1
Radiation eX210CrW12 ¼ 0.82
(Table 10.2) for the component and the tools. The materials considered for the tools
were hot forming tool steel X38CrMoV5-1 and the molybdenum-based alloy TZM to
compare the influence of different heat conductivities on the cooling process.
Figure 10.33 and 10.34 show the results for the tool combination of TZM as die
material and 1.2343 as plunger material. After complete filling of the die and a
compression for 3 s, the main volume of the component is cooled very quickly below
the solidus temperature. Only the centre contains a small region of semi-solid
material. In the case of the tools, the surface temperatures reach values of about
600 C (TZM) and 760 C (1.2343). Because of the higher heat conductivity of TZM,
the heat flow is enhanced so that the heat-influenced zone reaches deeper into the
dies. Therefore, critical temperatures at the boundary areas can be minimized.
Figure 10.34 shows the temperature distribution of the component in different
stages after finishing the forming operation. When the die is completely filled, rapid
cooling starts in the flange and the bush while the centre is still in the semi-solid
interval at about 1270 C after 3 s of cooling under compression. After pulling out the
plunger and cooling for another period of 10 s, the component is completely
Figure 10.33 Temperature distribution in the component and the
tools after forming operation and a cooling time of 3 s (ABAQUS).
10.4 Simulation of the Thixoforming Processj403