scholarly journals Carbide to Graphite Transition Control by Thermal Analysis in Grey Cast Irons

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 993
Author(s):  
Elena Loredana Neacsu ◽  
Iulian Riposan ◽  
Ana Maria Cojocaru ◽  
Stelian Stan ◽  
Iuliana Stan
Keyword(s):  
Thermal Analysis ◽  
Eutectic Reaction ◽  
General Rule ◽  
Thin Wall ◽  
Cast Irons ◽  
Experimental Conditions ◽  
Good Relationship ◽  
Transition Control ◽  
Grey Cast ◽  
Undercooling Degree

The present work compared the solidification pattern of un-inoculated and inoculated hypoeutectic grey cast irons (3.7–3.8% CE), focused on carbide to graphite formation transition, by the use of an adequate experimental technique, able to measure real stable (Tst) and metastable (Tmst) eutectic temperatures. Have been used three ceramic cups for investigating thermal analysis: (i) for normal solidification; (ii) with addition of Te for Tmst measurement; (iii) with more inoculant addition for Tst measurement. As a general rule, measured values appear to be lower compared with calculated values (as chemical composition effects), with an average difference at 14.4 °C for Tst and 8.3 °C for Tmst. It is found a good relationship between the undercooling degree at the lowest eutectic temperature (ΔT1) and at the end of solidification (ΔT3), reported to measured Tmst. The free carbides formation (chill tendency) is in good relationship with the undercooling degree during the eutectic reaction, reported to measured Tmst, especially for thin and medium wall thickness castings. The real measured Tmst instead of calculated Tmst is compulsory for the thin wall castings production, very sensitive to carbides to graphite transition. In the present experimental conditions, no visible relationship appears to be between chill tendency and undercooling at the end of solidification (ΔT3).

scholarly journals Ce-Bearing FeSi Alloy Inoculation of Electrically Melted, Low Sulphur Grey Cast Irons for Thin Wall Castings

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1122
Author(s):  
Irina Varvara Balkan ◽  
Iulian Riposan
Keyword(s):  
Wall Thickness ◽  
Structural Characteristics ◽  
Cooling Curve ◽  
Thin Wall ◽  
Cast Irons ◽  
Iron Castings ◽  
Grey Cast ◽  
The Difference ◽  
Thermal Cooling ◽  
Fesi Alloy

Electrically melted and over-heated (>1500 °C) grey cast iron at less than 0.04%S, as commonly used, solidifies large amounts of carbides and/or undercooled graphite, especially in thin wall castings; this is necessary to achieve a stronger inoculation. The efficiency of Ce-bearing FeSi alloy is tested for lower ladle addition rates (0.15 and 0.25 wt.%), compared to the base and conventional inoculated iron (Ba,Ca-bearing FeSi alloy). The present work explores chill and associated structures in hypoeutectic grey iron (3.6–3.8%CE, 0.02%S, (%Mn) × (%S) = 0.013–0.016, Alres < 0.002%), in wedge castings W1, W2 and W3 (ASTM A 367, furan resin sand mould), at a lower cooling modulus (1.1–3.5 mm) that is typically used to control the quality of thin wall iron castings. Relatively clear and total chill well correlated with the standard thermal (cooling curve) analysis parameters and structural characteristics in wedge castings, at different wall thickness, displayed as the carbides/graphite ratio and presence of undercooled graphite morphologies. The difference in effects of the two inoculants addition is seen as the ability to decrease the amount of carbides and undercooled graphite, with Ce-bearing FeSi alloy outperforming the conventional inoculant, especially as the wall thickness decreased. It appears that Ce-bearing FeSi alloy could be a solution for low sulphur, electric melt, thin wall iron castings production.

scholarly journals Chill sensitiveness and thermal analysis parameters relationship in hypo-eutectic, Ca and Ca-La inoculated commercial grey cast irons

2020 ◽  
pp. 20-20 ◽  
Author(s):  
E. Stefan ◽  
M. Chisamera ◽  
I. Riposan
Keyword(s):  
Thin Wall ◽  
Cooling Curves ◽  
Cast Irons ◽  
First Derivative ◽  
Specific Distribution ◽  
Nucleation Sites ◽  
Wedge Shape ◽  
Grey Cast ◽  
Sand Mould ◽  
Thermal Cooling

Previous experiments shown a specific distribution of Al, La and Ca on the section of complex (Mn,X)S compounds, found as major nucleation sites for graphite flakes in low-S cast irons (< 0.03%S), and a possible contribution of La to improve their capacity to nucleate graphite, avoiding carbides formation. In the present work, standard thermal [cooling curves] investigations are undertaken to explore Ca and La-Ca bearing FeSi alloys inoculation effects [10 measurements for each inoculant], in 3.7 - 3.8%CE and optimum S and Mn relationship [0.046 - 0.056%S, (%Mn) x (%S) = 0.024 - 0.029]. Representative temperatures on the cooling curves and under-cooling degrees referring to the meta-stable eutectic temperatures are determined and correlated with the chill [carbides/graphite formation sensitiveness], in different solidification conditions [cooling modulus, wedge shape castings, resin sand mould]. Supplementary addition of La to Ca-bearing inoculants has limited, but specific benefits in these cast irons: lower eutectic recalescence and of the maximum recalescence rate, higher GRF1 and lower GRF2 graphitizing factors and lower value of the first derivative at the end of solidification. Consequently, it results a premise for lower shrinkage sensitiveness and lower chill (carbides) sensitiveness, especially at the highest solidification cooling rate (thin wall castings).

Solidification Control by Thermal Analysis of La/Ba Inoculated Grey Cast Iron

2015 ◽  
Vol 1128 ◽  
pp. 35-43
Author(s):  
Eduard Marius Stefan ◽  
Mihai Chisamera
Keyword(s):  
Thermal Analysis ◽  
Cast Iron ◽  
Research Work ◽  
Structure And Properties ◽  
Analysis Method ◽  
Cast Irons ◽  
Analysis Technique ◽  
Grey Cast ◽  
Solidification Parameters ◽  
Solidification Control

Thermal analysis is worldwide used in foundry for control of structure and properties of cast irons. In this paper is presented the experimental study realized to control the inoculation effect by thermal analysis method of inoculated grey cast irons. For this purpose was conducted an in ladle inoculation process with 0.5wt. % inoculant from LaCaAlFeSi and BaCaAlFeSi alloy systems. The main goals of this experimental research work are: to determine the particular characteristics of the registered cooling curves, to notice the solidification parameters that present sensibility as against inoculant addition in treated cast iron and eventually to improve thermal analysis technique of cast irons.

scholarly journals Effect of Cooling Rate and Aluminium Addition on Graphite Growth during Solidification and Graphitization

2018 ◽  
Vol 925 ◽  
pp. 20-27 ◽  
Author(s):  
Jacques Bourdie ◽  
Fabien Bruneseaux ◽  
Philippe de Parseval ◽  
Sophie Gouy ◽  
Lydia Laffont ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Eutectic Reaction ◽  
Thin Wall ◽  
Cast Irons ◽  
Cooling Conditions ◽  
Graphite Degeneracy ◽  
Aluminium Addition ◽  
Graphite Structure ◽  
Graphite Growth ◽  
The Impact

Even using high inoculation levels, mottled structures are often obtained when casting Mg-treated cast irons in thin wall parts. For full graphitization of the cast components, this calls for a subsequent heat-treatment which is generally achieved in the austenite field. The aim of this work was investigating the impact of the process and the cooling rate on the graphite structure for two different casting conditions. The influence of the cooling rate on graphite degeneracy due to the presence of impurity was also investigated considering low-level additions of aluminium. Extensive metallographic investigation has been carried out from which it is concluded that the internal graphite structure is the same for the two studied cooling conditions. Accordingly, the growth mechanism of graphite should be the same when it precipitates from liquid, during eutectic reaction or else solid-state graphitization. Finally, microanalyses suggest magnesium and aluminium do not interact in the same way with graphite during its growth.

Effect of experimental conditions on the differential thermal-analysis of karnallite type hydrates

1984 ◽  
Vol 49 (12) ◽  
pp. 2770-2775
Author(s):  
Vladimir Z. Poilov ◽  
Jana Ederová ◽  
Antonín Blažek
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Experimental Conditions

Article in Russian

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

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 846
Author(s):  
Iuliana Stan ◽  
Denisa Anca ◽  
Stelian Stan ◽  
Iulian Riposan
Keyword(s):  
Cast Iron ◽  
Eutectic Reaction ◽  
Influencing Factor ◽  
Cooling Curve ◽  
Major Influence ◽  
Cast Irons ◽  
Minor Elements ◽  
Si Content ◽  
Si Effect ◽  
Positive Effect

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.

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