Cast iron is a material that has been around for thousands of years. It’s been used for cooking, architecture, and even weapons. But what exactly is cast iron?
What is Cast Iron?
Cast iron is a type of iron alloy that is composed mostly of iron but contains carbon in the form of graphite. The carbon content in cast iron varies from 2% up to 4%, which affects its properties.
Cast iron is relatively brittle and soft, which makes it more susceptible to cracking than other types of steel. It also tends to rust easily, especially when exposed to water or air.
As a result, cast iron products must be handled carefully.
Cast iron has been used for thousands of years as a building material and for making everything from pots and pans to cookware and engine parts.
It’s also used in some types of machinery because it can withstand high temperatures without breaking down or losing its strength as other materials might do.
Types of Cast Iron
Grey Cast Iron: Grey cast iron is a particular variety of cast iron that has undergone processing to allow the metal to include free carbon (graphite) molecules.
By adjusting the iron’s cooling rate and stabilizing the graphite with silicon, the size and structure of the graphite may be altered.
When Grey Cast Iron fractures, it does so along the graphite flakes, leaving the fracture site looking grey.
Even though grey cast iron is less ductile than other cast irons, it has the finest damping properties of all cast irons and good heat conductivity. It is a well-liked material to work with since it is durable.
Grey cast iron is perfect for engine blocks, flywheels, manifolds, and cookware due to its great wear resistance, high heat conductivity, and outstanding damping capacity.
White Cast Iron:The name “White Cast Iron” refers to how the cracks appear.
All of the carbon in the iron may be used in the production of iron carbide by strictly regulating the carbon concentration, lowering the silicon percentage, and managing the pace of cooling.
As a result, an iron that is hard, brittle, exceedingly wear-resistant, and has high compressive strength is produced, ensuring that there are no loose graphite molecules.
Any fracture site appears white because there are no free graphite molecules, giving White Cast Iron its name.
White cast iron is typically utilized in pump housings, mill linings and rods, crushers, and brake shoes due to its wear resistance.
Ductile Cast Iron: A little quantity of magnesium, around 0.2%, is added to cast iron to generate ductile cast iron, which results from the graphite forming spherical inclusions.
In comparison to other cast iron goods, it can also endure heat cycling better.
Due to its relative ductility, ductile cast iron is primarily employed and is widely used in water and sewer infrastructure.
It is a common choice for crankshafts, gears, heavy-duty suspensions, and brakes due to its resistance to heat cycling.
Malleable Cast Iron: A form of cast iron called malleable cast iron is created by heating white cast iron to a high temperature, which causes the iron carbide to dissolve back into free graphite.
As a result, a ductile and malleable product is created, one with good fracture toughness at low temperatures.
Electrical fittings, mining equipment, and machine parts are all made of malleable cast iron.
Casting Process of Cast Iron
The casting process begins by heating the molten metal to a temperature of around 2,000 degrees Fahrenheit in order to remove any impurities from it (known as de-gasification).
The molten metal is then poured into molds made from sand which is known as sand casting so that it has a shape when it hardens.
Molten metal can also be poured directly into a mold made from clay, ceramic or plastic if no other form of mold is available.
After pouring, air bubbles that may have formed during cooling are removed from inside the mold by tapping it gently with a hammer or chisel until they pop out on their own accord.
Then, the excess metal around the edges of the mold is removed by filing it down with a metal file. After the metal has cooled, it can be removed from its mold.
This is done by tapping gently on the mold with a hammer until it breaks off into pieces small enough to remove by hand. The surface of the object is then smoothed down and polished with a metal polisher.
Advantages of Cast Iron
Cast iron is one of the most widely used materials for casting parts. It has many advantages over other materials such as steel and aluminum:
Low cost: Cast iron is cheaper than steel and aluminum because it requires less energy to make it into a useful shape. This makes it an ideal material for castings that have complex shapes or require multiple molds. This also makes it ideal for mass production purposes since it allows you to produce more items at a lower cost per unit.
Good strength: Cast iron has good tensile strength, making it suitable for heavy-duty applications. It also has good compressive strength, making it suitable for applications where high pressure needs to be applied to an object.
High melting point: The melting point for cast iron is about 2,200° F (1,204° C), making it possible to melt down scrap without changing its composition significantly from what was originally cast into the mold.
Good casting properties: The good casting properties of cast iron allow foundries to make large parts with minimal porosity and shrinkage porosity. This makes it ideal for making large components that require little post-processing before assembly into finished products, such as engine blocks for automobiles or cylinder heads for marine engines.
Disadvantages of Cast Iron
Poor Tensile Strength: The tensile strength (or breaking strength) of cast iron is lower than that of steel.
This means that you need to make sure that your castings have adequate reinforcement if they are going to be subjected to heavy loads or impacts.
This also means that it cannot be used for structural parts because they will break under stress.
Rust-Prone: Cast iron is susceptible to rust and corrosion, especially in humid environments. When left untreated, cast iron will eventually rust away.
The only way to prevent this is through regular maintenance with paint or other protective coatings.
High Brittleness: Cast iron is a brittle alloy, meaning it has low ductility. This can cause problems in casting foundries that are not set up to accommodate brittle alloys.
This is especially true when it comes to sand casting. When the molten metal is poured into the mold cavity, it cools very quickly and solidifies.
As this happens, the sand will often crack or break as it tries to fill in the voids left by the now-cooled cast iron object.
For some applications, this may not be a problem, but for most foundries, this will result in costly repairs or even total replacement of molds and machine parts that have been damaged due to brittleness caused by casting with cast iron alloys.
High Weight-To-Strength Ratio: Cast iron has a high weight-to-strength ratio compared to other metals.
This means that it is very heavy and dense but has less strength than other materials like aluminum or steel.
This makes it difficult to work with when creating large projects because you will need a lot of material to achieve the desired result with your project.
Applications and Uses of Cast Iron
Cast Iron Cookware
Cast iron cookware is one of the most common uses for this material. Cast iron skillets and pans are known for their durability and heat retention abilities.
They’re also relatively cheap compared to other types of pans. The downside is that they’re heavy and take longer to heat up.
Cast Iron Stoves and Fireplaces
Cast iron stoves were once a popular way to heat homes because they were cheap to manufacture, distribute and install in homes.
These days, most homes have gas or electric appliances instead of wood- or coal-burning stoves.
The only remaining place where you’ll see cast iron stoves is in historic buildings where they’ve been preserved from earlier eras.
Cast iron fireplaces are another common application for this material because they retain heat well while burning fuel efficiently — even more efficiently than modern fireplaces!
Cast Iron Pipes
Cast iron pipes are used in many industrial settings because they’re durable enough to withstand harsh conditions like extreme temperatures or pressure changes over time without degenerating.
The pipes are also easy to weld and repair if they’re damaged, so they last a long time even when they’re exposed to harsh environments.
Cast iron pipes are also used in residential applications — for example, many older homes have cast iron piping that delivers water throughout the house.
