What is a Cast Iron and its Uses?

What is Cast Iron?

Cast iron is an iron alloy that contains more than 2% carbon. Although it can contain any percentage of carbon between 2% and 6.67%, in practice it is only between 2% to 4%. And also have varying amounts of silicon and manganese and traces of impurities such as sulfur and phosphorus.

It is made by reducing iron ore in the blast furnace. Liquid iron is cast or cast into raw piglets in the form of pigs and hardened, and the pigs are then re-molten in cupola furnaces with scraps and alloying elements and to manufacture a wide variety of products. Its can convert into molds.

Cast iron is a brittle and less ductile material with high corrosive strength. Due to its high compressive strength, it is used to make the base or body of most machines. Cast iron also has a low melting point of about 1200 degrees centigrade which makes it suitable for casting. It is named cast iron due to its casting properties. It has low manufacturing costs and has excellent machining properties.

What is the Difference Between Cast Iron & Steel?

There is a fundamental difference between cast iron and steel. Cast Iron contains more than 2% carbon and Steel contains less than 1% carbon.

Cast iron is cheaper than most steels. Also, the cast iron melting temperature is lower than that of steel, but it has high compressive strength, high hardness, and high wear resistance. Therefore, the important difference between steel and cast iron is that steel is ductile and malleable, whereas cast iron is hardened and has high compressive strength.

As another important difference between steel and cast iron, we can say that carbon in steel is in the form of iron carbide while cast iron has carbon as graphite or iron carbide or both. In addition, cast iron has excellent fluidity, with no steel.

Properties of Cast iron and its Composite

Cast iron also contains a small number of impurities such as silicon, sulfur, manganese and phosphorus, copper, nickel, chromium, which affect its properties on a small or large scale. The effect of these properties as follows.

Properties of Cast Iron

Silicon: In cast iron, silicon particles have up to 4 percent presence. It promotes graphite formation which makes it soft and easily machinable and Increases hardenability and electrical resistivity.

Sulfur:  It is present up to 0.1 present. It makes cast iron hard and brittle.

Manganese: It promotes carbide formation of cast iron which makes it elite, hard and increases resistance to wear and abrasions. It is present up to 0.75 percent.

Chromium: It also promotes carbide formation which Increases hardenability, wears resistance, corrosion, and oxidation resistance.

Nickle: Increases tensile strength.

Tungsten: It increases hot hardness and hot strength.

Molybdenum: Increases hardenability.

Vanadium: Increases hardenability and hot hardness.

Aluminum: Works as deoxidizer in steel.

Titanium: Works as deoxidizer in steel.

Niobium: It reduces hardenability and increases ductility, which results in increased impact strength.

Cobalt: It reduces hardenability and resists softening at elevated temperatures.

Types of Cast Iron

There Are Four types of main cast Iron as explain below:

  1. Gray Cast iron
  2. White Cast iron
  3. Malleable Cast Iron
  4. Ductile Cast iron

Gray Cast Iron

Gray iron, or grey cast iron, is a type of cast iron that has a graphitic microstructure. It is named after the gray color of the fracture it forms, which is due to the presence of graphite. It is the most common cast iron and the most widely used cast material based on weight.

The First Type of Cast iron contains carbon in free form. It is also known as commercial cast iron due to mostly used for commercial purposes.

It contains 3 to 3.5 percentile carbon and rests iron. This cast iron has low tensile strength, high compressive strength, and no ductility. It has excellent machining property. This metal is designate by FG followed by the digit show maximum tensile stress.

Types Of Cast Iron

White Cast Iron

White cast iron is a type of carbon-iron alloy that contains carbon content greater than 2% in the form of cementite.

The name white cast is derived from its white surface, which is caused by carbide impurities that allow cracks throughout the metal. When fractured it exhibits a silver-like (white) fracture.

Cast iron in which carbon is present in a combined form or in carbide form known as white cast iron. The white color is due to carbide formation. It is hard and not suitable for machining. This iron has high tensile strength and low compressive strength.

Malleable Cast Iron

Malleable cast irons are produced from white cast iron by heating it and holding it at 1,500–1,750°F (816–954°C) and then slowly cooling through a temperature range of 1,300–1,400°F (704–760°C).

This cast iron is obtained from white cast iron by the heat treatment process. It is mostly obtained by annealing of white cast iron.

It has improved strength and ductility like steel but can be easily cast. It is often used for small tensile, with good tensile strength and the ability to flex without breaking (ductility). Uses include electrical fittings, hand tools, pipe fittings, washers, brackets, fence fittings, etc.

Ductile cast iron

It is also known as Nodular or high strength cast iron. It has a high strength. It is obtained from Gray cast iron by adding a small amount of magnesium to the molten stage.

It is designated by SG followed by the numbers which indicate tensile strength and percentage elongation.

Mottled Cast Iron

Cast iron which has an equal amount of free carbon and carbide known as mottled cast iron. It has intermediate property and color of Gray cast iron and white cast iron.

Chilled Cast Iron

If the white cast iron quickly cooled from the molten stage, the iron produced is known as chilled cast iron.

Alloy Cast Iron

Alloy cast iron produced by adding some alloying elements in cast iron like nickel, chromium, copper, etc. It has increase properties according to the alloying element. This cast iron is produced to get the desire properties of cast iron.

Use of Cast Iron

Cast iron can be use for many types of materials and making different tools etc.

  • Grey cast iron: Engine cylinder blocks, flywheels, gearbox cases, machine-tool bases.
  • White cast iron: Bearing surfaces.
  • Ductile cast iron: Gears, camshafts, crankshafts, piston ring.
  • Many types of sanitary fittings like sewer pipes, manholes, water pipes, cisterns are manufacturing using cast iron.
  • Column base and metal columns can be made using cast iron
  • Casting mold used for making lamp posts, metal staircases, gates,s, etc.
  • Carriage wheels and rail chairs are made from cast iron.
  • Various types of agriculture equipment and implements can be made from it.
  • Various machinery parts can be made from cast iron
  • It is used in making automotive parts
  • It is used in making pots pans and utensils
  • It is used in making anchors for ships

Advantages and Disadvantages of Cast Iron.

Advantages of cast iron

  • It has Good casting properties
  • It has good Sensibility
  • It has excellent resistance to wear
  • It has good machinability.
  • It has very low notch sensitivity
  • It has a Low-stress concentration
  • It bears Low cost
  • It has Durability
  • It has Resistance to deformation
  • It has three to five times higher compression strength than steel.
  • It has excellent anti-vibration (or damping) properties so it is used to make machine frames.
  • It has constant mechanical properties between 20 and 350 ° C.
  • It is available in large quantities, hence produced on a mass scale. Tools required for the casting process are relatively cheap and inexpensive. This results in a low cost of its products.
  • It can be given any complex shape and size without using costly machining operations

Disadvantages of cast iron

  • It is Prone to rust
  • It has a poor tensile strength
  • It has a high weight to strength ratio
  • It has High brittleness
  • It has poor impact resistance
  • Compared to steel it has poor machinability
  • Its parts are section sensitive; this is due to the slow cooling of thick sections.
  • The failure of its parts is sudden and in total, it does not reflect the yield point.
  • It is Nonmachinable (white cast iron).

In this article, you learn about what is cast iron and types of cast iron. If you have any queries regarding this article ask by comment below. If you like this article, don’t forget to share it on social networks. Thanks for giving your valuable time for this article.

Frequently Ask Question

What is Cast Iron?

Cast iron, an alloy of iron that contains 2 to 4 percent carbon, along with varying amounts of silicon and manganese and traces of impurities such as sulfur and phosphorus. It is made by reducing iron ore in a blast furnace.

What is cast iron used for?

With its relatively low melting point, good fluidity, castability, excellent machinability, resistance to deformation, and wear resistance, cast irons have become an engineering material with a wide range of applications and are used in pipes, machines, and automotive industry parts, such as cylinder heads, cylinder.

What is cast iron made of?

Cast iron, an alloy of iron that contains 2 to 4 percent carbon, along with varying amounts of silicon and manganese and traces of impurities such as sulfur and phosphorus. It is made by reducing iron ore in a blast furnace.

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