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Cast Iron and Cast Steel Comparison

Oct. 29, 2021

Casting offers excellent capability for design details, often without additional fabrication and assembly. Steel in particular has excellent mechanical properties and is suitable for a wide range of applications. Although cast iron and steel may appear similar on the surface, they have distinct advantages and disadvantages from production to application. Understanding these and making the appropriate choice may help your production and reduce your losses. Malleable iron pipe supplier BONA shows you their differences.


Cast Iron and Cast Steel Comparison

BAKE GALVANIZED MALLEABLE IRON PIPE FITTINGS


Carbon content

Elemental iron is a substance found in nature, usually in oxidised form, and requires an intensive process known as smelting to extract it. Pure elemental iron is too soft to be used in most applications. When it is alloyed or mixed with carbon, it becomes harder and therefore more useful. The carbon content is the main difference between cast iron and steel. Cast iron usually contains more than 2% carbon, while cast steel usually contains 0.1-0.5% carbon.


Castability

There are significant differences between iron and steel in terms of fluidity and shrinkage. Cast iron is relatively easy to cast as it is easy to pour and does not shrink as much as steel. This means that it can easily fill complex voids in moulds and requires less molten material to do so. BONA has malleable cast iron fittings for sale and they have good properties.

Casting steel is much more difficult. It has a lower flow than iron and is more reactive to the mould material. Cast steel requires more attention and inspection throughout the casting process, making production more resource intensive.


Machinability

Depending on the end application, castings may need to be machined to achieve specific tolerances, or to achieve the required finish. At the very least, objects such as doors and runners will need to be cut out and ground flat.

Cast iron is usually easier to machine than steel. The graphite structure in cast iron comes off more easily and is more uniform. Harder iron rods, such as white iron, are more difficult to machine due to their brittleness.

Cutting steel at the same consistency is not as easy and leads to more tool wear, which results in higher production costs. Hardened steels or steels with a higher carbon content also increase tool wear.


Compressive strength

Compressive strength is the ability of a material to withstand a force that would reduce the size of an object. This is the opposite of a force designed to pull the material apart. Compressive strength is beneficial in mechanical applications where pressure and tightness are factors. Typically, cast iron has a better compressive strength than steel.


Cast Iron and Cast Steel Comparison

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Corrosion resistance

Iron has a better resistance to corrosion than steel. Both metals will oxidise in the presence of moisture, but iron will develop a patina to prevent deep corrosion of the metal's integrity. Any debris or cracks that expose the underlying metal will lead to corrosion, so regular maintenance is important for the coated metal. 


Cost

Cast iron is usually cheaper than cast steel because of the lower cost of materials, energy and labour required to produce the final product. Raw steel is more costly to purchase and casting requires more time and effort. However, in the long run, manufacturing parts that cost more may ultimately reduce costs.



Alloys or carbon can be added to iron and steel to engineer the desired properties. BONA also has carbon steel tubes for sale, and different carbon contents also differentiate between low carbon, standard and high carbon steels. Ultimately, the choice between cast iron and cast steel will depend on the type and application of the final installation. For more information on iron or steel or other fittings, or to request a quote for a bespoke project, please contact us.



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