Metallurgical and Mechanical Properties

Cast irons are iron-carbon alloys generally containing between 2.8% and 4% carbon. They are distinguished from other alloys by their excellent castability (this term covers the thermal inertia and fluidity of the molten alloy).

These alloys are obtained by solidification, and their characteristics depend on the different phases that make them up (phases similar to those found in steels, in which graphite is inserted). The appearance of these phases is explained by the physical phenomena associated with solidification: germination and growth.

Lamellar graphite castings are produced using the most common casting technologies for high-melting alloys. Green sand casting, combined with various coremaking processes, is the most commonly used to obtain gray cast iron parts. This process, with its dimensional accuracy, enables rapid transition to the finished product, while limiting machining operations. This low-cost processing technology makes it possible to combine several functions of a complex system in a single part, by adapting shapes and dimensions. These functional considerations are also combined with optimized aesthetics.

All these aspects give lamellar graphite cast iron products an economic advantage due to :

• the low cost of the materials used to produce liquid cast iron,

• the many melting processes available for these liquid melts (blast furnaces, cupola furnaces, induction furnaces, etc.),

• the complexity of the functional shapes that can be obtained with this alloy,

• the special properties induced by the presence of graphite in the material.

This article presents the metallurgical and mechanical properties of this material, so that designers of new, ever more complex mechanisms can use lamellar graphite cast iron with optimum cost-effectiveness. Knowledge of the quantities associated with these properties enables us to model the behavior of the parts that will make up the systems of the years to come. A better understanding of the properties of these cast irons means that production can be increased in virtually all industrial sectors: automotive, aeronautics, railways, energy, public works, construction, etc.