Effect of section thickness on microstructure and mechanical properties of compacted graphite iron for diesel engine applications

Mahmoud A Essam,Ahmed Y Shash,Hassan Megahed,Emad El-Kashif

doi:10.1016/j.heliyon.2021.e05930

Mahmoud A Essam, Ahmed Y Shash + Show 2 more

Open Access

https://doi.org/10.1016/j.heliyon.2021.e05930

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Abstract

Compacted (vermicular) graphite iron (CGI) is used in many substantial applications because its vermicular microstructure has superior mechanical properties at higher temperatures. Production of vermicular graphite cast iron diesel engine cylinder block with various sections’ thicknesses is a great challenge especially, if compacted graphite iron is made by controlling the pouring duration. Investigations on microstructure and hardness have been conducted on four different thicknesses (5, 10, 15, and 20 mm) of compacted graphite iron. Results demonstrated that pouring duration affects both cooling rate, and Mg/S content. These two parameters to decide the nodularity percentage and the matrix microstructure. Longer pouring duration lowers Mg/S content and decreases the cooling rate for the similar section thickness, however shorter pouring duration acts in the opposite direction. Microstructure and hardness are also affected by casting sections with the same pouring duration through different cooling rates. An increase in the cross-sectional thickness for the same pouring duration decreases the rate of cooling that encourages the formation of compacted graphite with pearlitic rather than martensitic a matrix in addition to lowers the nodular graphite count. Magnesium fading and compacted graphite ratio increased with longer pouring duration. Hardness decreased with larger section thickness and longer pouring duration due to the elimination of the martensite phase in the matrix.

Highlights

Casting is a basic production technique sand casting that is the most accommodating production method for large-size products
The aim of the current work is to check the effect of cooling rate on vermicular graphite cast iron through solidification of various casting section thickness with two different pouring duration (10.5 and 17.5 min respectively)
An induction furnace was used to melt Compacted (vermicular) graphite iron (CGI) manufacturing from tube of copper and a magnetic field with high frequency that created by current that passes through this coil that is cooled by using water

Summary

Introduction

Casting is a basic production technique sand casting that is the most accommodating production method for large-size products. Graphite in compacted graphite cast iron appears in an exceedingly worm-like form with curved ends while etched surface appears coral like that decreased stress concentration levels compared with gray (flakes) cast iron. This morphology of graphite ends up to higher cohesion in material and resistivity of crack propagation subsequently shock absorbing and toughness [7]. This morphology has great stability at an elevated temperature that persuades compacted cast iron of high shock applications at high temperatures [8]. During a comparison to lamellar graphite cast iron using compacted graphite cast iron can reduce a load of cylinder block by 25% as compacted cast iron has higher fatigue limits [9]

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