Solidification influence in the control of inoculation effects in ductile cast irons by thermal analysis

Anca

et al. 2021

Metals

Self Cite

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.

Section: Methodsmentioning

confidence: 99%

Section: Thermal (Cooling Curve) Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Anca

et al. 2021

Metals

Self Cite

“…This method determines the characteristic parameters of the solidification process (temperature), crystalli-zation (the first derivative of the solidification process) and nucleation (the second derivative of the solidification process). Thermal derivative analysis is carried out by pouring the tested metal into a cup made of a shell mass with a thermocouple for temperature measurement [13][14][15][16][17].…”

Section: Influence Of Charge Materials On the Metallurgical Quality O...mentioning

confidence: 99%

Evaluation of the Metallurgical Quality of Nodular Cast Iron in the Production Conditions of a Foundry

Dwulat¹,

Janerka

2023

JMMP

The aim of this research was to determine the factors affecting the metallurgical quality of cast iron during serial production of castings using a campaign cupola and a holding furnace. The problem to be solved, which was to obtain cast iron with the required mechanical properties while reducing the internal porosity, results from the foundry’s need to increase the metallurgical quality of the alloy. The increasing difficulty and complicated constructions of castings, for which it is not possible to introduce risers at the stage of technological design, make the stage of proper preparation of cast iron the only way to obtain castings without shrinkage defects. The article presents the results of the study of physicochemical and mechanical properties, microstructure and shrinkage tendency of ductile iron depending on the charge materials used, the amount of Mg used during spheroidization and the type of final inoculants. Step castings and wedge tests were produced on a vertical molding line. The spheroidization was carried out by injecting a core wire containing Mg alloy into the cast iron. The final inoculation of 0.2% was performed using a pneumatic dispenser equipped with a vision system to control the effectiveness of the inoculation. The ITACA Meltdeck thermal analysis system was used to study the physicochemical properties of the initial cast iron, and the ITACA X system to analyze the state of the final cast iron on the molding line. Mechanical tests were performed on samples cut from a stepped casting, and microstructure tests were carried out using a light microscope and a scanning electron microscope. The results of thermal analyses show that increasing the share of pig iron at the expense of steel increases the minimum solidification temperature of eutectic, and thus, increases the potential for graphite nucleation in cast iron. Increasing the nucleation potential can be obtained by adding anthracite, FeSi and SiC. A very important factor in obtaining cast iron of high metallurgical quality is the possible limitation during spheroidization of the length of the core wire containing Mg, which is a carbide-forming element. The lower the initial sulfur level, the greater the possibility of reducing the amount of cored wire. The inoculants containing Ce and Bi were the most advantageous final inoculants from the point of view of obtaining the best microstructure parameters and plastic properties of cast iron.

“…However, it is said that recalescence is a function of the composition, inoculation and nucleation of iron. According to Cojocaru et al, 21 inoculation increases speed of recalescence; however, that data values were scattered which needed further investigation. Xu et al 22 investigate speed of recalescence in different undercooled melts, and it was observed that SOR is affected by undercooling and with the increase in undercooling, SOR also increases.…”

Section: Introductionmentioning

confidence: 97%

Speed of Recalescence as a Measure of Graphite Nucleation in Spheroidal Graphite Cast Iron Castings

Bhat

Khan

Singh³

2020

Inter Metalcast

The solidification of spheroidal graphite cast iron (SGI) plays an important role in production of sound quality castings. However, owing to the complex solidification behaviour of SGI, prepouring melt quality evaluation technique such as thermal analysis is used to predict quality of liquid metal by analysing the cooling curve pattern. In this study, an attempt has been made to investigate the role of speed of recalescence (SOR) in nucleation of graphite during solidification of SGI. Cooling curve analysis of liquid samples was carried out at different inoculation degrees. Recalescence and SOR data were obtained from thermal analysis, whereas nodule counts were obtained from microstructural examination of respective sample. It was observed that recalescence and nodule counts (nucleation sites) have a statistically significant inverse linear relationship; with the increase in recalescence, the nodule count was found to get reduced. However, the multiple values of nodule count at same recalescence degree were to be understood, which was clearly justified by SOR studies. After analysing the SOR vs nodule count relation, almost each SOR value corresponds to different nodule counts and the relation was statistically more significant. This infers that for an in-depth nodule count estimation, SOR analysis will be more helpful as compared to DTr; hence, it is envisaged that speed of recalescence is true indicator of graphite nucleation as compared to recalescence in SGI.