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Metal Casting Technologies : June 2007
www.metals.rala.com.au 48 TECHNICAL FEATURE Plunger speeds were set in 30, 50, and 70 cm/sec. Then the fill rate of shot sleeve was 30% unique. The setting of the injection conditions in the shot sleeve for the experiments and numerical simulations is shown in Table 1. RESULTS AND DISCUSSION Fig. 3 shows the 3D shot sleeve model and the 30% fill rate state of molten metal. In the first, we have done the verification test through the comparison with the theoretical plunger displacement and the numerical simulation result. The 3D grid system (210x40x40)wasusedinthis calculation. The molten metal is poured initially into the shot sleeve through the left side gate system in the Fig. 4. The right side one is a vent system. The molten metal pushed out by plunger is exhausted through this vent system. The plunger shape is not drawn in this figure while the molten metal flow pattern in the shot sleeve is expressed. When the plunger speed is 50 cm/sec, the plunger displacement has to be 20.5 cm after 0.41 seconds theoretically. As we can see in the Fig. 4, the numerical simulation result shows the plunger displacement exactly. Fig. 5 shows the flow patterns in the shot sleeve for the plunger speed of 30 cm/sec. The molten metal in the shot sleeve is strongly suppressed by the plunger as the plunger start to move. Then the molten metal is pulled up to the upper wall of sleeve. In this plunger speed, the pushing pressure of the plunger is not so high yet, so that the front of molten metal pulled up by the plunger does not touch the upper part wall of the sleeve. When the plunger moves further, the wave moves faster than the plunger and hits the end of the shot sleeve. After that, the end part of the shot sleeve is full up firstly with the molten metal remaining the empty part in front of the plunger. The void region in the shot sleeve is undesirable in the casting operation. And, as you can see Figure 3: Shot sleeve model and 30% fill rate state of molten metal. (a) Shot sleeve model (b) 30% fill rate state A Figure 4: Displacement verification of numerical simulation result: plunger speed is 50 cm/sec B Figure 5: Time history of flow pattern: plunger speed is 30 cm/sec and the fill rate is 30% (a) experimental results (b) numerical results Figure 6: Time history of flow pattern: plunger speed is 70 cm/sec and the fill rate is 30% (a) experimental results (b) numerical results A B A B A B A B A B A B