furan resin moulds. As molten iron flowed into each of the reaction chambers, inoculation occurred and the inoculated iron then flowed into the test samples.
A new generation spectrometer with hybrid optic [photo- multiplier tubs (PMT) and charge coupled device (CCD) de- tectors simultaneously)] was used for high precision metal analysis. The instrument achieves detection limits below 1 mg/kg. The two experimental Heats (A, B), are differenti- ated by the level of the TRE present in the Mg-treatment al- loys, the level after ladle Mg-treatment and in-mould levels in castings (plate samples), respectively (Table 3, Fig. 2).
After Mg-treatment, the two heats included almost identi- cal residual magnesium levels (0.059 –0.062%Mgres
), but the
content of rare earth elements in the treated irons, such as Ce and La, was clearly influenced by their content in the Mg-Fe- Si treatment alloy. As a result, the content of these elements in ductile iron B is five times lower compared to ductile iron A (wt-%): 0.0056TRE versus 0.0266TRE, 0.0040Ce versus 0.020Ce and 0.0014La versus 0.0074La, respectively.
As expected, the content of these active elements in the graphite nodularization process is lower in the test castings compared to ladle Mg-treatment samples, despite the limited holding time up to mould pouring. Graphite nodularization was also dependent on the type of elements present, such as Mg versus TRE and Ce versus La, respectively.
(c)
In comparing the magnesium levels just after Mg-treatment of Heat A to Heat B, (0.062%Mgres
). The TRE levels varied in much the same way, except in a tighter range (0.022 - 0.024%TRE for Heat A and 0.0054 - 0.0062%TRE for Heat B).
castings from these heats were characterized by similar re- sidual magnesium ranges (0.042 - 0.052%Mgres
versus 0.059%Mgres - 0.057%Mgres
The recovery levels of Mg and TRE of the two nodularising alloys was markedly different. • Total rare earth elements recoveries were double those of Mg regardless of TRE level in the master alloy. • Cerium recoveries were double those of La.
), the versus 0.045 (b)
(a)
Figure 2. Nodulizing elements (Mg, TRE, Ce, La) in ladle Mg-treated iron and in – mould thin wall plate castings, as general range (a), average content (b) and recovery level (c).
Table 3. Final Chemical Composition of Selected Ductile Irons (Castings)
International Journal of Metalcasting/Volume 8, Issue 2, 2014
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