Difference Between Cast Iron and Cast Steel

Main Difference – Cast Iron vs Cast Steel

Casting is a form of a manufacturing process where liquidized material is poured into a mould and then allowed to cool down. To be specific, the process of solidification is called ‘casting’. The solidified material is broken out of the material upon completion. Metals commonly undergo casting in order to be put into various desired shapes. The main component of both cast Iron and cast Steel is the Iron element itself. What differs is the amount of Carbon present in both forms. The main difference between cast iron and cast steel is that Cast Iron generally has a Carbon content higher than 2%, and Cast Steel has a Carbon content lower than 2%.

What is Cast Iron

As mentioned above, the carbon content in cast iron is higher than 2%, which differentiates it from other forms of irons. It can be further divided into two types called ‘white cast iron’ and ‘grey cast iron’. The white cast irons contain carbide as an impurity and accommodate deeper cracks. In contrast, the grey cast irons contain graphite as an impurity and handle cracks at the surface level, initiating many new cracks.

Another term of interest would be ‘pig Iron’, which is the molten iron in a blast furnace. Usually, cast iron is produced by re-melting pig iron with a large quantity of iron and steel strips along with limestone and coke (for Carbon). Undesired products such as Sulphur and Phosphorous get heated/burnt in the process, and a significant amount of Carbon is lost here as well. However, Carbon is re-introduced into the melted metal to meet the desired content. Cast iron has very good casting properties and is well known for its wear resistivity. It also absorbs vibration well and has a good machinability. But, its response to tension is very low. Some of the most common applications of cast Iron are; oil pan, hammer, pitons, valves, motor blocks, cylinder blocks, knives, etc.

What is Cast Steel

Cast Steel has a higher flexibility in design, and its overall structural strength is higher making it more reliable. It typically has an amount of Carbon below 2% but contains other alloying elements. These allow Steels to be further categorized into two groups such as low-alloy Steel and high-alloy Steel. Low-alloy Steel has an alloying content less than 8%, and the same is higher than 8% for high-alloy Steel. Steel castings are generally used when the Iron casting cannot deliver the strength needed.

Further refining processes such as normalizing, quenching and tempering the metal are performed to perfect the properties and quality of Steel. The presence of additional alloying material including Chromium, Nickel, Zinc, Cobalt, etc. improves the appearance, makes it easy for fabrication and also prevents corrosion.