Effect of the cooling rate on the tensile strength of pearlitic lamellar graphite cast iron

ABSTRACT

The effects of cooling rate and carbon equivalent on the tensile strength of pearlitic lamellar graphite cast irons were investigated. The cooling rate was varied from 6°C/s to 35°C/s for values of the carbon equivalent equal to 4.17% and 3.83%. The increase in the cooling rate promoted the refining of the eutectic cell size, primary dendrite modulus, interdendritic hydraulic diameter and pearlite interlamellar spacing. The increase in the cooling rate also refined their graphite flakes, changing the morphology from B to E type. The reduction in the carbon equivalent increased the proportion of primary dendrites from 25% to 40%. The maximum tensile strength increased from 274 to 524 MPa with the increase in the cooling rate and the reduction in the carbon equivalent. These results were used to test two tensile strength predictive models based on modified versions of the Griffith and Hall-Petch equations.

KEYWORDS:

• Lamellar graphite cast iron
• thin-wall casting
• microstructural parameters
• tensile strength
• interdendritic hydraulic diameter
• predictive models

Acknowledgements

The authors recognise the appreciated support of Dr Daniel L. Rodrigues Jr (EPUSP), MSc Raphael O. Ferreira (EPUSP), The Institute for the Technological Research of the State of São Paulo (IPT) and Tupy S.A. The authors thank the suggestions and criticisms made by Prof. R. Fuoco (SENAI), Prof. W. L. Guesser (Santa Catarina State University) and Dr E. Albertin (IPT). Additionally, Prof. Cesar R. F. Azevedo acknowledges the Brazilian National Council for Scientific and Technological Development (CNPq) for his research grant (Process: 302077/2016-2).

Disclosure statement

The submitted manuscript represents original work and has not been previously published or simultaneously submitted elsewhere for publication. The document has been read and approved by all authors. This research was partially sponsored by the Institute for the Technological Research of the State of São Paulo (IPT) and Tupy S.A. Finally, the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This work was supported by the Brazilian National Council for Scientific and Technological Development (CNPq) [302077/2016-2].