Experimental and numerical analysis of effect of cooling rate on thermal–microstructural response of spheroidal graphite cast iron solidification

Paper deals with influence of cooling rate and alloying elements on kinetics of eutectoid transformation in spheroidal graphite cast iron (SGI). Transformation of austenite can proceed into ferrite and graphite (FeFeG) and/or in pearlite (Fe  FeFe3C). Examination of eutectoid transformation was made by evaluating the “in-situ” dilatation curves together with metallographic examinations, DTA, and dilatation analyses in solid state. ThermoCalc software was applied for thermodynamic calculations of phase equilibria. Based on numerous quantitative relations, such as relation between fractions of ferrite and pearlite in the as-cast SGI that was determined by analysis of dilatometric curves and taking into account also composition of melt, ferrite/pearlite ratio in the microstructure could be determined in a very short time. Thus the melt composition could be corrected by adding Cu and/or Mn or Si, respectively, using the "in situ" dilatation analyses. Characteristic temperatures of eutectoid transformation have been established from the kinetics of austenite transformation and from temperature dependence of ferrite and/or pearlite growth. Kinetics curves that enable to determine fractions of single microstructure constituents in the microstructure as function of transformation time, mainly used for ferrite and pearlite SGI, can be well determined with physical sigmoidal Boltzmann model.

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Influences of Silicon and Phosphorus Contents and Cooling Rate on JIC Fracture Toughness of Ferritic Spheroidal Graphite Cast Iron

MRS Proceedings ◽

10.1557/proc-34-517 ◽

1984 ◽

Vol 34 ◽

Cited By ~ 1

Author(s):

Shinichiro Komatsu ◽

Toshio Shiota

Keyword(s):

Fracture Toughness ◽

Cast Iron ◽

Cooling Rate ◽

Compact Tension ◽

Graphite Nodule ◽

Spheroidal Graphite ◽

Test Pieces ◽

Spheroidal Graphite Cast Iron ◽

Graphite Cast Iron ◽

Curve Method

ABSTRACTThe influences of silicon and phosphorus contents and cooling rate on JIC fracture toughness of ferritic spheroidal graphite cast iron were investigated by 15mm thick compact tension test-pieces. The JIC values were measured by means of the R-curve method for most cases at 20°C, and by means of the maximum J value method for the cases at -100° C. The results obtained are summarized as follows. At 20WC, the specimens with silicon contents less than 3.2% showed the ductile Load-COD relations, but a specimen with 3.5%Si showed a brittle Load-COD relation and the JIC decreased greatly. Increasing phosphorus content between 0.006% and 0.26% made the JIC value decrease gradually and made the slope of the R-curve decrease greatly. Difference in cooling rate produced differences in graphite nodule diameters and ferrite grain sizes. At 20°C, the larger the specimen's average graphite nodule diameter was, the larger the JIC value was. At -100° C, the Jic values of all the specimens tested decreased largely, and the influences of these factors became very different from those at 20° C.

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Influence of Melting Conditions on Graphite Morphology in Spheroidal Graphite Cast Iron Using Ni-C Alloys

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.457.37 ◽

2010 ◽

Vol 457 ◽

pp. 37-42 ◽

Cited By ~ 1

Author(s):

Yuji Kato ◽

Ying Zou ◽

Hideo Nakae

Keyword(s):

Cast Iron ◽

Cooling Rate ◽

High Purity ◽

Holding Time ◽

Spheroidal Graphite ◽

Graphite Morphology ◽

Spheroidal Graphite Cast Iron ◽

Graphite Cast Iron ◽

Group 2 ◽

Group 1

The effects of the cooling rate, atmosphere and holding time on the graphite morphology of spheroidal graphite cast iron were studied using Ni-C alloys. Two groups of parent alloys were prepared using high purity materials, i.e., Group 1 containing the spheroidizing element of Ce, Mg or Ca, while in Group 2, S was added as an anti-spheroidizing element. For discussing the influence of the cooling rate on the graphite morphology, 0.5g of the Group 1 samples were melted and held for 15 minutes at 1673K in an Ar atmosphere, then cooled at 1000K/min or 20K/min. The results showed that perfect spheroidal graphite could not be confirmed, while irregular graphite appeared. The atmosphere was changed to Ar+3%H2 for preventing the oxidation, and the holding time was reduced to 10 minutes to prevent fading of the spheroidizing element. These results showed that the formation of spheroidal graphite was confirmed at the cooling rate of 1000K/min in both groups. Nevertheless, at the cooling rate of 20K/min, graphite morphology was only chunky or flake in both groups. In order to investigate which parameter is more important for the formation of spheroidal graphite, the atmosphere and the holding time were independently changed at the cooling rate of 1000K/min. It was found that the addition of the 3%H2 did not significantly affect the spheroidal graphite formation. Moreover, the holding times of 1min and 20min also did not significantly affect the spheroidal graphite area fraction in the Ni-C alloy, while they affected the ones containing the spheroidizing elements like Mg.

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Solidification simulation of thick-walled spheroidal graphite cast iron with controlling cooling rate

The Proceedings of the Fluids engineering conference ◽

10.1299/jsmefed.2018.gs1-6 ◽

2018 ◽

Vol 2018 (0) ◽

pp. GS1-6

Author(s):

Naoto MATSUNAGA ◽

Kazumichi SHIMIZU ◽

Kenta KUSUMOTO

Keyword(s):

Cast Iron ◽

Cooling Rate ◽

Spheroidal Graphite ◽

Solidification Simulation ◽

Spheroidal Graphite Cast Iron ◽

Graphite Cast Iron

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Color Etching for Characterization the Grain Orientation in Spheroidal Graphite Cast Iron

Materials Science Forum ◽

10.4028/www.scientific.net/msf.537-538.389 ◽

2007 ◽

Vol 537-538 ◽

pp. 389-396 ◽

Cited By ~ 2

Author(s):

Ibolya Kardos ◽

Zoltán Gácsi ◽

Péter János Szabó

Keyword(s):

Cast Iron ◽

Crystallographic Orientation ◽

Grain Orientation ◽

Test Material ◽

Spheroidal Graphite ◽

Metallic Materials ◽

Additional Information ◽

Spheroidal Graphite Cast Iron ◽

Graphite Cast Iron ◽

Back Scattering

Color etching is a widely used technique for visualizing different phases in metallic materials. Its advantage to the traditional etching techniques is that it gives additional information within one phase, namely, the color shade of a given phase can change in a certain range. This paper demonstrates that, due to the physics of the color etching, the shade of a phase also depends on the crystallographic orientation of the investigated grain. As a test material, spheroidal graphite cast iron was used, and individual grain orientation was identified by automated electron back scattering diffraction (EBSD). Results showed that there is a strong correlation between grain orientation and the shades obtained by color etching.

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