Experimental Evidence for Metallurgical Modification Associated to Chunky Graphite in Heavy-Section Ductile Iron Castings

Parameters that affect chunky graphite formation in heavy-section castings have been studied in previous works which showed that inoculation and cerium addition both increase the tendency for this degenerate graphite. This suggested that laboratory study on chunky graphite formation could be performed on small castings by over-treating the melt. Though the role of silicon was not ascertained, it appeared of potential interest to also investigate its effect in relation with the carbon equivalent of the iron and the nucleation potential of the melt. Keel-blocks were thus cast using Ce or Ce-Mg treated melts, with increased silicon content (up to 4.0 wt.%) and inoculation rate as compared to usual practice. It was observed that chunky graphite systematically appeared in more or less extended areas centred on the upper part of the keel-blocks. The as-cast microstructure (graphite shape and distribution) has then been studied in relation to melt composition and additions (Ce treatment and inoculation) in both affected and non-affected areas. Finally, microanalysis of oxides and other minor phases showed them to be similar to those appearing in heavy-section castings. It may then be concluded that chunky graphite appears in light-section castings in the same way than in heavy-section castings when using over-treated melts.

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Effect of inoculant containing rare earth metals and bismuth on microstructure and mechanical properties of heavy-section near-eutectic ductile iron castings

Journal of Materials Processing Technology ◽

10.1016/j.jmatprotec.2013.03.012 ◽

2013 ◽

Vol 213 (9) ◽

pp. 1601-1608 ◽

Cited By ~ 29

Author(s):

P. Ferro ◽

A. Fabrizi ◽

R. Cervo ◽

C. Carollo

Keyword(s):

Mechanical Properties ◽

Rare Earth ◽

Ductile Iron ◽

Rare Earth Metals ◽

Iron Castings ◽

Heavy Section ◽

Microstructure And Mechanical Properties

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On the solidification sequence of ductile iron castings containing chunky graphite

Materials Science and Engineering A ◽

10.1016/j.msea.2005.08.210 ◽

2005 ◽

Vol 413-414 ◽

pp. 346-351 ◽

Cited By ~ 42

Author(s):

Rikard Källbom ◽

K. Hamberg ◽

M. Wessén ◽

L.-E. Björkegren

Keyword(s):

Ductile Iron ◽

Iron Castings ◽

Solidification Sequence ◽

Chunky Graphite

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Effect of Yttrium and Magnesium Segregation on Microstructure and Mechanical Properties of Heavy Section Ductile Iron Castings

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.295-297.1010 ◽

2011 ◽

Vol 295-297 ◽

pp. 1010-1016 ◽

Cited By ~ 1

Author(s):

Wei Ping Chen ◽

Zhe Liu ◽

Yu Deng ◽

Jie Luo ◽

Yong Cheng Chen

Keyword(s):

Mechanical Properties ◽

Ductile Iron ◽

Magnesium Content ◽

Solidification Mode ◽

Iron Casting ◽

Iron Castings ◽

Microstructure And Mechanical Properties ◽

Chunky Graphite ◽

Main Factor ◽

Ductile Iron Casting

Ductile iron specimen with dimensions of Φ590mm×800mm were prepared by treating the melt with an yttrium-containing nodulizer. Cooling curves at four locations____the center location, the location 85mm distant from the center, the location 170mm distant from the center and the location 255mm distant from the center of the heavy ductile iron casting Φ590mm×800mm was obtained. The effect of yttrium and magnesium on microstructure and mechanical properties was investigated, and the factors on the distribution of chunky graphite in the specimen were discussed as well. The results show that the largest amount of chunky graphite and the lowest mechanical properties appear at the location 170mm distant from the center. Excessive yttrium and magnesium content at the location 170mm distant from the center is the main factor for the large amount of chunky graphite. The characteristics of the solidification mode____pasty solidification and the considerably long solidification of the casting are the basic reasons for the distribution of chunky graphite of the heavy ductile iron casting Φ590mm×800mm.

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Microstructure and mechanical properties of heavy section ductile iron castings: experimental and numerical evaluation of effects of cooling rates

International Journal of Cast Metals Research ◽

10.1179/1743133615y.0000000022 ◽

2015 ◽

Vol 28 (6) ◽

pp. 365-374 ◽

Cited By ~ 14

Author(s):

L. Ceschini ◽

Al. Morri ◽

An. Morri ◽

E. Salsi ◽

R. Squatrito ◽

...

Keyword(s):

Mechanical Properties ◽

Ductile Iron ◽

Numerical Evaluation ◽

Cooling Rates ◽

Iron Castings ◽

Heavy Section ◽

Microstructure And Mechanical Properties

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Effect of Yttrium-Containing Nodulizer on the Microstructure Formation and Mechanical Properties of Heavy Section Ductile Iron Castings

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.457.73 ◽

2010 ◽

Vol 457 ◽

pp. 73-78 ◽

Cited By ~ 2

Author(s):

Qin Xin Ren ◽

Ming You ◽

Yun Bang Yao ◽

Guang Min Wen ◽

Qi Zhou Cai

Keyword(s):

Mechanical Properties ◽

Ductile Iron ◽

Graphite Nodule ◽

High Melting ◽

Microstructure Formation ◽

High Melting Point ◽

Iron Castings ◽

Heavy Section ◽

Long Time ◽

Pearlite Content

Ductile iron specimens with dimensions of 400mm×400mm ×450mm were prepared by treating the melt with an yttrium-containing nodulizer. The effect of yttrium on microstructure and mechanical properties was investigated, and the formation of degenerate graphite was discussed as well. The results show that the yttrium-containing nodulizer has good nodulization fading resistance for heavy section ductile iron, since the high melting point hexagonal oxide Y2O3 particles were formed from the nodulizer in the melt and those could act as heterogeneous nuclei for graphite nodule for a long time. Segregation of Ti and MgO at grain boundaries broke the austenite shell, resulting in graphite degeneration. When heavy section ductile iron castings with pearlite matrix were cast, graphite nodule size became finer and the nodularity of graphite nodules improved due to the addition of 0.01wt% Sb to the melt, and pearlite content in specimens increased due to alloying with Cu, Cr, Mo. The heavy section ductile iron tool bed was fabricated by treating the melt with the yttrium-containing nodulizer and Ni. The nodularity of the attached block was 85%~90%, tensile strength, elongation and impact toughness were 440MPa, 23.3% and 5.0J/cm2 respectively.

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