When comparing steel and iron, it is necessary to consider the specific composition of each material. A fundamental manufacturing method, casting involves hot-forming a metal material by pouring it into a mold that produces the desired shape and physical characteristics. This article examines different steel and iron cast metal alloys, their mechanical properties, and their chemical composition. This will help you gain insight into the metal industry.
Different Types of Cast Irons
Iron and steel are often used interchangeably, but they are quite different. Iron is the base element and steel is the combination of iron, carbon and other compounds. Cast iron is regarded as a type of steel, with iron, manganese and carbon in the mix (carbon content is between than 2-4%.) When compared to steel, Irons are more likely to become brittle and have low stability, even though it is resistant to corrosion. However, due to its lower melting point and manageable cost, iron has also gained its popularity for various industrial applications. The four most common types of Cast Irons are:
- White Iron
This type of iron is characterized by very low carbon content. Typically, white cast iron is tough and durable, with high wear resistance. These alloys retain their hardness for only a limited time. A cast made of white iron may have a gray structure elsewhere.
This material has excellent compression strength. It is an ideal choice for parts that require a high level of hardness. However, it is unsuitable for applications requiring high temperatures and wears resistance.
- Gray Iron
Besides being an excellent machinability material, gray-iron is also resistant to wear. Nevertheless, it’s dimensional and machinability properties can be compromised by improper machining. Due to its elasticity, gray iron can be used in high-temperature applications.
Its mechanical properties are highly dependent on the cooling rate and the thickness of each section. A bead along the outer edges of flanges can prevent these from breaking. A gray iron cast has a high damping capacity and can be easily machinable. But this metal is not suitable for casting abrasive parts.
- Ductile Iron
Ductile iron is the most commonly used material for casting for its durability and low cost. It has high hardness and strength and is widely used for structural applications. This metal has a carbon equivalent of 0.8 and is usually a good choice for casting in hot-working conditions.
Its high density makes it ideal for welding and forging. However, ductile iron is also available in high-alloy and austempered versions. The production of ductile iron is complex and expensive. It is a mixture of several metals and alloys.
The base iron is a high carbon equivalent, and magnesium is added to it during the casting process. In a blast furnace, the liquid iron contains high amounts of magnesium, which causes a violent reaction. The resulting product is a mixture of sulfur and magnesium oxides.
- Malleable Iron
The main characteristic of Malleable Iron is its ability to withstand a high temperature. The process is characterized by a rapid solidification rate and a temperature range between 1650 and 9000 degrees Fahrenheit.
Unlike other materials, Malleable Iron is highly resistant to abrasion. It is easy to machinate, has good shock resistance, and can be painted. It also loses its volume when it cools. This characteristic makes it the ideal material for small, intricate castings. If you're looking for a new, durable material for a project, it might be a good idea to consider a Malleable Iron cast.
Different Types of Steel Cast
Steel is stronger than iron. The properties found in steel are quite different from cast irons. Steel only has carbon content ranges up to 2 percent, with a higher carbon content, the material is defined as cast iron. Other elements commonly found in steel are manganese, silicon, phosphorus, and sulfur. Steel is the most widely used material for any industry because it can be adapted and used in a variety of ways. Below are the two common types of steel casts:
- Carbon Cast Steel
This material is especially good at creating intricate shapes. It is highly suitable for bending, welding, and forming tasks and is the most flexible of all materials. Nonetheless, it requires more care and maintenance than most other metals.
Carbon cast steels, like wrought steels, can be classed based on their carbon content. Low carbon cast steel (0.2 percent carbon) is brittle and difficult to heat treat. Medium carbon cast steel (0.2–0.5 percent carbon) is slightly tougher and more heat treatable than low carbon cast steel. High carbon cast steel (0.5 percent carbon) is employed when maximum hardness and wear resistance are required.
- Alloyed Cast Steel
These materials offer unique properties, including corrosion, heat resistance, and scale resistance. The wide variety of alloying elements allows you to choose the most appropriate material for your specific application. Alloyed castings are versatile and offer virtually unlimited design freedom. Their properties are enhanced by various heat-treating and quenching processes. Some types of ‘alloy steel’ may also have additions of nickel, chromium and vanadium.
High-alloyed steels contain over 10% chromium, forming a passivation layer when exposed to air or oxygen. Similarly, high-alloyed cast steels have a high manganese content, which provides excellent strength and abrasion resistance when hard-working.
Standards organizations have created various grades of steel based on the desired properties of these alloys. Alloyed cast steels are highly resistant to elevated temperatures. However, as the operating temperature increases, the mechanical properties of these materials degrade.
This often leads to early failure due to hydrogen damage, sulphite scaling, or carbide instability. When temperatures fall below 100°C, the toughness of the alloy steel cast is severely diminished. Nevertheless, adding alloying elements can make the steel more suitable for a specific application.
When deciding between steel and iron, it's essential to understand their differences. Both steel and iron have similar appearances but have different benefits and drawbacks. Knowing the differences can make a difference in the durability and appearance of your finished product. Using suitable materials for your project can help you create a strong, durable product.