The standard materials used for block housings are flake graphite cast iron, spheroidal graphite cast iron and cast carbon steel.
Flake graphite cast iron block housings
For block housings made from flake graphite cast iron, cast iron in accordance with DIN EN 1561 is generally used. In these cast materials with a iron/carbon/silicon base, the graphite inclusions are present in lamellar form. Under tensile load, these act as internal notches. The tensile strength of flake graphite cast iron is therefore limited and its ductility is comparatively low. The compressive strength of this alloy is, however, higher than the tensile strength by a factor of 4 and these alloys also have good inherent stability.
Flake graphite cast iron is therefore used in the case of housings with simple requirements. Furthermore, flake graphite cast iron represents the most economical variant of the cast materials available for use in housings.
Spheroidal graphite cast iron block housings
For block housings made from spheroidal graphite cast iron, cast iron in accordance with DIN EN 1563 is generally used. Due to an addition of magnesium or, more rarely cerium or calcium, the graphite inclusions adopt a spheroidal form during casting. As a result, the tensile strength and ductility are higher than those of the grades with a lamellar graphite form.
Spheroidal graphite cast iron is therefore used in the case of housings with an increased profile of requirements. The costs of spheroidal graphite cast iron are between those for flake graphite cast iron and cast steel.
Cast steel block housings
For block housings made from cast steel, steel in accordance with DIN EN 10293 is generally used. Both unalloyed and alloyed steels are suitable for casting. The unalloyed cast steel used for housings combines moderate to high strength values with high elongation at fracture.
Cast steel is therefore used in the case of housings with high requirements for mechanical properties as well as a requirement for high ductility.
The costs of cast steel are higher than the costs for flake graphite cast iron or spheroidal graphite cast iron. It is therefore recommended that it should be checked whether the material is really necessary in relation to the requirements of the specific application.
unsplit block housings
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