Solidification influence in the control of inoculation effects in ductile cast irons by thermal analysis
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Slightly hypoeutectic ductile irons (4.10–4.2%CE) have a specific response to inoculation, which slightly decreased the temperature of the start of austenite formation (TAL), quickened up the start of eutectic freezing (nucleation) and increased the lowest and the highest (recalescence) eutectic temperatures. Temperature of the end of solidification increasing, with more negative level of the minimum value of the first derivative of cooling curve on the end of solidification, illustrates the efficiency of the applied inoculation to control the latter part of solidification. Increased graphitization factor, illustrating the graphite formation in the second part of eutectic reaction, sustains also the positive effect of inoculation. Inoculated irons show lower cooling rate for all of specific intervals than un-inoculated irons, with increasing tendency from beginning to the end of solidification, as specific values and also as difference between un- and inoculated irons. Inoculation potential, as ratio between the level of one specific parameter in inoculated and un-inoculated irons, has specific position, for each thermal analysis parameter, increasing from the beginning to the end of solidification. This treatment is useful not only to improve some metallurgical events at the beginning of solidification (carbide to graphite transition, graphite morphology control, eutectic cells count) but also it must be capitalized to control the last part of solidification, when the integrity of castings is decided.
KeywordsDuctile cast iron Solidification Thermal analysis Cooling curve analysis Inoculation Eutectic under-cooling Graphitization factor Inoculation potential
Funding was provided by Unitatea Executiva pentru Finantarea Invatamantului Superior, a Cercetarii, Dezvoltarii si Inovarii (Grant No. 115PED; PN-III-P2-2.1-PED-2016-1793).
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