The Many Advantages of Gray Cast Iron

Posted on Jul 14, 2020

Gray Cast Iron

Gray cast iron (or gray iron) has its name because of its gray-colored fracture. It is the innate graphite content that creates this typical gray fracture. It is the most used type of material for die/mold manufacturing. In this article, we want to talk about the many advantages of this material.

How is Gray Iron Made?

Gray iron is a product made by casting pig iron. Pig iron is an intermediate product in the production of steel. Gray iron contains steel, a small quantity of carbon, arsenic, manganese, and sulfur. If you use a microscope to observe gray iron, you will probably see the microstructure of graphite (which is easy to identify). You may also see black graphite scales in it.

The gray graphite structure is created by the carbon during the hardening process. The properties of gray iron can be altered based on the materials mixed in the casting process. The excellent physical properties make it one of the most commonly used materials today. Let's take a closer look at some advantages and applications of gray cast iron.

Advantages of Gray Cast Iron

Below are the advantages of gray iron:

Low Cost

One of the many advantages is that gray cast iron has the ability to create complex structures at a relatively low cost. Gray iron castings are common because of the low price. It has sufficient ductility, tensile strength, yield strength, and impact resistance for most applications.

Good Vibration/Damping Capability

Gray iron also has outstanding vibration/damping capabilities, which makes it suitable for mechanical and other housing applications. The high level of thermal conductivity makes it efficient to transfer heat through metals.

Excellent Compressive Strength

While the tensile strength and impact resistance is weaker than that of most other castings, the compressive strength is equivalent to low-carbon and medium-carbon steel. Such a property is determined by the graphite flakes in its microstructure. We will talk more about compressive strength in the next section.

Ability to Withstand Thermal Cycling

Gray iron castings are able to withstand thermal cycling. The thermal cycle refers to the components switching back and forth between higher and lower temperatures. Although thermal cycling may cause stress and premature failure in certain types of metal castings, gray iron has proven to withstand thermal cycling well and not easily stressed.

Why is High Compressive Strength Important?

Compressive strength is characterized as the toughness of a metal (or alloy) to withstand a compressive force. The high compressive strength is the major reason why gray iron castings are frequently used to form columns, housings, and structural parts of a machine. High compressive strength usually comes along with some other properties listed as follows:

Tensile Strength

The tensile strength of gray iron castings varies based on the content of other components. That said, they usually have an average tensile strength of seven tons per square inch. The strength can be higher with more vanadium added.

Deformation Resistance

Gray iron provides very high structural rigidity and anti-deformation quality. However, it is worth noting that the deformation resistance is subject to the structural design of the part. If the part is not well-constructed, it will deform when too much force is applied.

Low Melting Point

The melting point is around 1,100 to 1,200 degrees Celsius, which is relatively low.

Oxidation Resistance

Gray cast iron is very resistant to oxidation. You don't have to worry about corrosion that much.

:: Read More: Gray Iron Properties and Grades Explained

Applications of Gray Cast Iron

Gray iron castings are heavier than other castings. They are used for many applications. For example, most manhole covers are made of gray iron because of their oxidation resistance. The disc brakes on the vehicles are also likely to be gray iron since it has excellent thermal conductivity. It is commonly used to make cooking utensils too. All in all, gray iron is ideal for making products that require a certain level of strength, corrosion resistance, and heat resistance.

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