In this article we will discuss about:- 1. Introduction to Cast Irons 2. Composition and Cooling Rate of Cast Irons 3. Comparison of Properties 4. Science of Development of Microstructures. Introduction to Cast Irons: Cast irons are iron-carbon (and silicon) alloys having carbon or carbon equivalent value, more than 2% (actually it is 2.1 1%), i.e., more than the maximum [...]
Malleable irons, both pearlitic and ferritic are obtained after malleablizing-annealing of white cast iron of controlled compositions. As this annealing heat treatment takes long time, moreover there are difficulties in cooling thick sections rapidly enough to get the original white cast iron, S.G. iron has replaced the malleable iron in many applications. However, thin-section components that require maximum machinability and [...]
Grey irons have graphite flakes dispersed in the steel-matrix, usually, of pearlite or ferrite (the amount of Mn could be as high as 1.2% for pearlitic, or as low as 0.1% for ferritic matrix). The heat -treatment has little or no effect on the size and shape of the graphite as obtained after casting. However, the carbon-diffusion-paths being shorter in [...]
These cast irons have high abrasion-resistance, and can be readily cast in shapes required in machinery used for crushing and grinding, etc. Abrasion-resistance increases with the increase of hardness due to the increase of the volume of the eutectic carbides (alloy eutectic carbides are much harder than iron carbide). The must element chromium prevents the formation of graphite during solidification [...]
S.G. irons have nodules of graphite embedded in the matrix usually of ferrite, or pearlite, or both, depending on the thickness of the casting and/or alloy composition. As the nodule of graphite is not that serious stress-raiser, and that the ends are not that sharp (as flakes) to act as crack, the mechanical properties such as tensile strength, hardness, ductility, [...]