Key Difference – Cast Steel vs Cast Iron
Cast iron and cast steel are two types of iron-carbon alloys. The main difference between these alloys is the carbon content in the composition. Cast iron is rich in carbon more than cast steel. Cast iron contains over 2% of carbon and cast steel contains less than 2% of carbon in weight. The purpose of this casting with carbon is to alter the properties of iron for advanced applications. Because, iron itself alone is a soft metal and it is not ideal for construction materials. There is not much difference in the chemical composition between these two alloys, but their physical properties differ significantly. Both of these types are equally important alloys in metallurgy in different ways.
What is Cast Steel?
Cast steel is a carbon iron alloy that contains less than 2% of carbon by weight. This material is produced by heating iron using a crucible container. In addition to carbon and iron, the cast steel contains one or more other metallic elements such as manganese, copper, aluminum, silicon, or chromium. These elements are added to improve physical and mechanic properties and corrosion resistance properties. Moreover, cobalt, columbium, molybdenum, nickel, titanium, tungsten, vanadium, zirconium, and any other element are added to obtain desired alloy properties.
What is Cast Iron?
Cast iron is a member of iron-carbon alloy family with the carbon content greater than 2%. It is one of the oldest ferrous alloys used in construction and outdoor ornaments. It is hard, brittle, nonmalleable and more fusible compared to steel. But properties slightly vary depending on the composition of the material. There are several categories of cast iron such as white cast iron, malleable cast iron, ferritic malleable cast iron, grey cast iron, and ductile iron. In addition to iron and carbon, these alloys contain silicon, manganese, sulfur and phosphorous.
What is the difference between Cast Steel and Cast Iron?
Composition:
Cast Steel:
Iron is the main element in cast steel; also it contains less than 2% of carbon by weight. It may also contain one or more of the following elements. Composition varies according to the application.
- Manganese – above 1.65%
- Silicon – above 0.60%
- Copper – above 0.60%
- Aluminum – up to 3.99%
- Chromium – up to 3.99%
Cast Iron:
The three main elements present in cast iron are carbon, iron and silicon. It mainly contains iron (95%) and over 2% of carbon by weight. In addition, it contains some other elements in smaller quantities, depending on the usage. Examples of those elements are manganese, phosphorous and sulfur.
Advantages:
Cast Steel:
Cast steel is flexible, therefore, it is very easy to design complex shapes and hollow cross section parts. This also has manufacturing variability; that enables to choose variable compositions and different heat treatment choices. It gives properties such as good weldability and workability.
Cast Iron:
Different varieties of cast irons have different advantages due to their unique properties; they are used based on the nature of the application. Some advantages are listed below.
- Grey cast iron: Possesses good casting properties, vibration damping, wear resistance, machinability and low notch sensitivity.
- Ductile iron and malleable iron: They are strong and have higher values for ductility, heat resistance, and toughness. In some applications, they are used as an alternative to carbon steel.
Disadvantages:
Cast Steel:
Cast steel is comparatively expensive than cast iron. It has disadvantages such as bad shake-suction, low wear resistance, mobility and casting resistance.
Cast Iron:
Grey cast iron: Its tensile strength and elongation are very low.
Ductile iron and malleable iron: The production cost of these materials is relatively high. The process is complex, and it requires advanced technology.
Image Courtesy:
1. Cast carbon steel gate valve By Heather Smith (The Alloy Valve Stockist’s photo gallery.) [CC BY 3.0], via Wikimedia Commons
2. Cast Iron Grills By P sakthy (Own work) [CC BY-SA 3.0], via Wikimedia Commons
