Solidification Pattern of Si-Alloyed, Inoculated Ductile Cast Irons, Evaluated by Thermal Analysis

Abstract

The solidification cooling curve itself as well as its first derivative, and related temperatures, reported to the calculated equilibrium temperatures in stable and metastable solidification systems, are used to predict the solidification characteristics of the cast iron. Silicon, as the most representative cast iron element, and inoculation, as graphitizing metallurgical treatment, have a major influence on the transition from the liquid to the solid state. Six experimental programs are performed, with Si content typically for non-alloyed (<3.0% Si), low (3.0–3.5% Si) and medium alloyed (4.5–5.5% Si) ductile cast irons, as Si-content increasing, and inoculation simultaneous effects. Silicon is an important influencing factor, but the base and minor elements also affect the equilibrium eutectic temperatures, much more in the Fe-C-Si-Xi stable system (15–20 °C) than in the metastable system (5–10 °C), comparing with their calculation based only on a Si effect (Fe-C-Si system). The highest positive effect of inoculation is visible in non-Si alloyed cast irons (2.5% Si): 9–15 °C for the eutectic reaction and 3 to 4 times increased at the end of solidification (37–47 °C). Increased Si content decreases inoculation power to 7–9 °C for low alloying grade (up to 3.5% Si), with the lowest contribution at more than 4.5% Si (0.3–2.0 °C). 2.5–3.5% Si ductile cast irons are more sensitive to high solidification undercooling, especially at the end of solidification (but with a higher efficiency of inoculation), compared to 4.5–5.5% Si ductile cast irons, at a lower undercooling level, and at lower inoculation contribution, as well.

Recent Advances in Cast Irons

“…The book collects manuscripts from cutting-edge academic researchers and consists of one review paper regarding the research progress in improving the corrosion wear resistance of a novel hypereutectic high-chromium cast iron (HCCI) [1] and eight experimental research papers focused on methods for enhancing the corrosion, mechanical and microstructural features of cast irons in general, i.e., nodular, gray, vermicular, austempered ductile iron (ADI) and HCCI [2][3][4][5][6][7][8][9].…”

“…Concerning nodular cast irons, relevant contributions have been proposed [2,3,5]. The paper by Vicente et al [2] concerns the applicability of the Hollomon-Jaffe parameter, usually used to establish an equivalence between time and temperature in a tempering treatment, to predict the hardness of nodular cast iron after quenching and tempering treatments.…”

Influence of Si content on the machinability of ductile iron

“…According to Stan et al [8], silicon is the most representative element in the composition of cast iron, with an essential role in the solidification process and graphitizing effect. Silicon inoculation is vital in the transition from liquid to solid state in cast iron, contributing to achieving high ductility and toughness characteristics with better machinability conditions.…”

Regularities of Crystallization Heat Release During Solidification of Alloyed Cast Irons

“…One of the effective methods to study the crystallization process of metals and alloys is the differential thermal analysis (DTA) [6][7][8]. It allowed particularly to investigate the graphitization ability of spheroidal graphite cast iron processed by Al, Zr, Ca-FeSi [9], solidification influence in the control of inoculation effects in ductile cast irons [10], solidification pattern of Si-alloyed, inoculated ductile cast irons [11], the influence of final inoculation on the metallurgical quality of nodular cast iron [12] and an increasing precision and yield at casting production by simulation of the solidification process based on realistic material data evaluated from thermal analysis [13].…”