Grey Iron Castings
The most versatile of all foundry metals, Grey Iron Castings have a very high carbon content that allows for considerable ease of melting, casting and machining. These castings are commonly used to manufacture pump housings, cylinder blocks, internal combustion engines etc. To be more articulate, these are used to manufacture components that are to be used in places where stiffness is more paramount than tensile strength.
Gray iron castings are also the most commonly used of all cast materials. Another noteworthy thing about these is the fact that these have a graphitic micro structure, resulting in a grey colored fracture which it forms, this is also the reason why the castings are named as grey iron castings.
Properties of Grey Iron Castings
The castings have low degree of shrinkage and high fluidity, thus providing maximum freedom in design for an engineer. This is one of the reasons why grey iron castings are widely favored.
The tensile strength of these castings can vary( generally from 20000 to over 60000 psi by suitable adjustment in composition)
Along with tensile strength, hardness of grey iron castings can also be varied by suitable selection of casting method
Grey iron castings have good galling along with optimal wear resistance
These have the lowest pouring temperature of all the ferrous metals
Basics of Grey Iron Castings Design
Simply put, the casting of grey iron involves using a pattern for forming a mold cavity into which molten metal is poured and solidifies before finally becoming a component. The design process starts well before the patterns are made, with the engineers deciding on the best design for the components to be made. Some thumb rules for designing optimum quality grey iron castings are avoiding sharp angles and corners, minimizing the number of sections, employing uniform sections, correctly proportioning inner walls and avoiding abrupt section changes. Although grey iron is one of the most versatile metals, still a knowledge of it's distinct characteristics is desirable before designing the castings.
Factors Affecting the Strength of Grey Iron Castings
The strength of grey iron castings is determined by the combined effects of the following factors:
Processing technique in the foundry