Metal Casting Technologies : Whos who September 2012
METAL casting Technologies september 2012 51 3. results and discussion Figure 3 is characteristics of the test data from the application of PoDFA technique. The figure shows the progression of filtration time versus filtrated weight of each melt sample. There are clear differences in filtration time between the two samples based on an equal filtered weight. The filtration time of sample ADC12 No.2 appears to increase at a higher rate than that of ADC12 No.1 after the filtrated weigh reached about 0.5 kg. Based on this characteristic curve, ADC12 No.02 is expected be less clean compared to ADC12 No.01. This is in good agreement with metallographic examination following the standard PoDFA technique as summarized in Table 2. The amount of oxides and other inclusions content are 32 and 40 counts/ kg, and 0.88 and 2.81 mm2/kg for ADC12 No.01 and ADC12 No.02, respectively. The nature and distribution of the oxides and inclusions as examined by optical microscopy are illustrated in Figure 4. In addition to the amount of oxides and inclusions content, the decrease in fluidity of the melt sample due to decreasing melt temperature during the test is another factor affecting the filtration time. Thus it is important to closely control the melt temperature when performing this test. Other factors such as vacuum pressure, variation in chemical composition, and so on, that may affect the characteristic test data, must also be considered. Fig 3. Filtration time versus filtrate weight curves of podFA technique Fig 4a. Sample number 01. Fig 4b. Sample number 02. Figs 4a & 4b. representative micrographs of the podFA samples showing oxide and inclusions in the cake area: (a) AdC12 No.01 and (b) AdC12 No.02.
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