Thixoforming : Semi-solid Metal Processing

Table 9.2 Temperature determination with and without correction of the emission coefficient.
Unit
Before determination of e After determination of e
Emission
Min.
( C)
Max.
( C)
Av.
( C) Emission
9.3 Thixocasting of Steel Alloysj333
Min.
( C)
Max.
( C)
Av.
( C)
1.2343 1 84.2 160.8 114.1 0.506 127.5 243.5 173.1
TZM Al2O3 IOT 1 152 185.2 162.6 0.711 187.2 227.9 200.2
TZM Al 2O 3 MCh 1 95.1 147.7 132.7 0.729 115.4 179.1 161
TZM Al2O3 IOT 1 97 113.7 108 0.678 123 144.3 137.1
1.2343 Al 2O 3IOT 1 102.1 189.8 169.3 0.506 155 287 256.2
1.2999 Al2O3 IOT 1 135 171.2 153.8 0.742 162.1 205.3 184.5
1.2999 Al 2O 3 IOT 1 100.3 160 137.9 0.762 118.4 188.9 162.8
1.2999 Al2O3 IOT 1 104.8 134.8 123.7 0.725 127.7 164.1 150.6
1.2343 1 66.5 107.6 75 0.506 100 163.3 113.3
CuCoBe 1 40.8 64.5 48.3 0.389 67.3 113.5 82.4
TZM multilayer MCh 1 62.3 144.9 129.5 0.788 71.5 167.6 149.8
Si3N4 massive 1 94.3 121.7 111.2 0.691 118.2 152.6 139.5
1.2343 1 86.7 195.5 167.9 0.506 131.4 295.6 254.1
Si3N4 soldered 1 165.2 259.1 228.4 0.977 167.6 262.8 231.6
HSS 1 45.5 120 63.9 0.469 68.9 190.6 100.1
1.2343 1 66.3 118.8 94.6 0.506 99.6 180.3 143.5
Figure 9.22 shows a thermograph of a component approximately 5 s after the
conclusion of the filling of the form. The biscuit itself is no longer very hot at 520 C
because it is only a few millimetres thick, which considerably increases the process
reliability. The area of the oxide restrainer belongs, at over 730 C, to the hottest zones.
The part does not show any rips which could be recognized as fine, bright lines. It
becomes visible that the different component thicknesses of 10 mm (in step 1)
and 5 mm cause a difference in temperature on the surface of over 250 C.
The temperature seems to rise within 5 mm of the plate end. This can be explained
by a transport of ceramic mould release agents by the flowing front and the
consequent increase in the emission coefficient.
The thermography of the tool surfaces directly after the removal of the component
shows clear differences for the single tool areas and materials. The centrally
inrushing material leads to strong heating of the runner and particularly the exposed
corners (315 C). The redirection of the vertically flowing SSM makes a strong energy
contribution to the surfaces above and below the gating.
The influence of the different tool materials can be clearly recognized. The silicon
nitride ceramic shows the highest temperature, over 300 C.
Against this, the copper insert on the other side is at only 80 C because of its
extremely high heat conductivity. The tests showed that the strength of the lowmelting
copper-based material is great enough for that process because the heat
conductivity is improved by around a factor of 10 compared with steels of the same
specific heat capacity.