The Influence of Trace Elements on the Nature of the Nuclei of the Graphite in Ductile Iron

Gorka Alonso; Doru Michael Ştefănescu; Esther de La Fuente; Pello Larrañaga; Ramón Suárez

doi:10.4028/www.scientific.net/MSF.925.78

Paper Titles

Effect of the Cooling Rate on the Graphite Nodule Count and Size Distribution in Nodular Cast Iron
p.45

Crystallography of Growth Blocks in Spheroidal Graphite
p.54

Degenerated Graphite Growth in Ductile Iron
p.62

Effect of Si and Ni Addition on Graphite Morphology in Heavy-Section Spheroidal Graphite Iron Parts
p.70

The Influence of Trace Elements on the Nature of the Nuclei of the Graphite in Ductile Iron
p.78

The Structure of Cast Irons
p.86

On the Primary Solidification of Compacted Graphite Iron: Microstructure Evolution during Isothermal Coarsening
p.90

Stereological Analysis of the Statistical Distribution of the Size of Graphite Nodules in DI
p.98

X-Ray Imaging of Formation and Growth of Spheroidal Graphite in Ductile Cast Iron
p.104

HomeMaterials Science ForumMaterials Science Forum Vol. 925The Influence of Trace Elements on the Nature of...

The Influence of Trace Elements on the Nature of the Nuclei of the Graphite in Ductile Iron

Abstract:

Nucleation mechanisms and the effect of minor elements added with the inoculants are still a subject of extensive research in ductile iron. Oxides, sulfides, silicates and nitrides have been reported to be nuclei for graphite precipitation. Those compounds originate both from the nodulizing treatment and the inoculation process. Previous research works have shown that titanium nitrides or carbonitrides play an active role in graphite nucleation. In order to determine the efficiency and nature of nitrides that can act as nuclei for graphite, and the possible effect of the trace elements added with the inoculant, melts with titanium contents ranging from 0.007% to 0.036% were produced and poured into standard thermal analysis cups, with and without inoculation. Different inoculants rich in titanium, cerium, aluminum or zirconium were used. Two cups were produced with each inoculant, one cooled down to room temperature, and the other quenched in brine immediately after pouring. Nucleation sites were characterized through detector, spectrum, mapping and line scans of a FEG-SEM equipment. Most of the analyzed nuclei exhibited two or three different inclusions: magnesium sulfides or Mg-Ca oxy-sulfides, Mg or Al oxides, and Ti carbo-nitrides or Mg-Si-Al nitrides. The appearance of each type of nitrides is directly related to the titanium content in the base melt. When titanium was added in the inoculant, no titanium nitrides were noticeable. The zirconium added with the inoculant promoted more complex nitrides that appeared in higher amount. Cerium appears occasionally forming sulfides. Aluminum stimulates the formation of complex nitrides. No differences in the nature of the nuclei were observed between the samples quenched and the ones obtained at room temperature, which assures the methodology approach.

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