Lamellar cast iron is a very important technical alloy and the most used material in the casting production especially in the automotive industry which is the major customer. There are many factors such as chemical composition, metallurgical condition and melt treatment that are effecting on the size, morphology and distribution of microstructure features of the lamella graphite iron which in turn this features effecting the material’s mechanical properties and tensile behaviour under static load.

In the past few years many researchers have been done different investigation within improvement of mechanical behaviour in the lamellar graphite iron. Controlling the solidification rate, changing the chemical composition and using different carbon content in the melt are some of the research that have been carried out in last years. Swerea/ Swecast in Jönköping has been involved in many of previous researches. The present work is part of the previous investigation that have been carried out in the Swecast/Swerea.

The aim of this work was to investigate the effect of different cooling rate on the microstructure parameters and furthermore how this parameters influence the ultimate tensile strength (UTS) in the lamellar graphite iron. To increase the understanding of cooling rates effect on the material properties, in this work the chemical composition and carbon content was equal in the all of the samples.

The collected data that are based on the morphological data of the solidification structure (dendritic network, eutectic cells) and the eutectoid transformation structure (pearlite) have been correlated to the measured tensile strength. The final purpose of this work was to develop a generic model for the prediction of the tensile strength in lamellar graphite iron which has been presented in the result chapters.

The question that have been answered in this work based on the following points.

 How the cooling rate influences the development of primary austenite phase and those effect on the UTS?

 How the pearlite interlamellar spacing develops during the different cooling rate and influencing the UTS?

 How the different cooling rates influence the size and amount of the eutectic cell and according to this how the UTS varies?

The work has been carried out according to the time plane (see appendix 6) and the result of this work showed that cooling rate has an essential effect on the microstructure features. By controlling the cooling rate, the material strength improves significantly.