What to Expect from The Gray Cast?

Posted on Dec 9, 2020

Grey Iron Casting

Gray cast is one type of iron castings that is made of graphite. The advantages of gray cast include cheap price and great strength, and so on.

What is gray cast?

Gray cast is one type of iron castings that is made of the flakes in the graphite fractures. The name gray cast can be derived from looking into the microstructure of the graphite casting, since the appearance of the flakes are gray, thus resulting in the name of gray cast.

Gray cast is the alloy of carbon, silicon, manganese, sulfur, and phosphorus. Since it is easily casted, the gray cast is widely used in the making of the accessories and components of cars, trucks, and tractors, etc.

The gray cast is made when the melting materials are poured into the molds, and then cooled until they are solidified. The properties of the gray cast, as well as other types of iron castings, vary from the proportion of each material that is cooled and solidified.

In addition, the properties of gray cast can also be influenced by the shape and size of the graphite flakes, which results in the variation of the products that are made of gray cast. Furthermore, there are other features that make the gray iron suitable for some specific applications, which are going to be discussed in the following paragraphs.

:: Read more : Introduction to Cast Iron Castings

What are the features of gray cast?

● cheap

When it comes to large-scale machining works, the cost and the versatility of the materials that are used during the process are definitely what the manufacturers would take into consideration.

The gray cast is the cheapest among all the iron castings, and the versatile applications and easily obtainable features make the gray cast popular in the iron castings for the manufacturers.

● tensile strength

The gray cast has less tensile strength than most other castings. While in some cases, the gray cast has the capability of strong deformation resistance, which makes it withstand a great amount of stress while being stretched or pulled before failing or breaking.

● yield strength

The yield strength of the gray iron, which is the stress that the gray iron can tolerate before permanent deformation or at the point when it can no longer return to its original dimensions, is usually less than other castings as well.

● brittleness

The gray cast is one of the brittle materials, which means that it is easily broken under less tensile strength. In other words, before the gray cast breaks, it absorbs little energy than other materials that have greater ductility.

● vibration dampening

The gray cast is good at damping vibrations that are caused when the products that are made of it operate, which makes it perfect for making the accessories and components of the automotive industries.

● thermal conductivity

The great thermal conductivity is one of the practical features of the gray cast, as it makes the gray cast transfer or conduct heat easily through the metal, which results in the wide range of application of gray cast in the industrial fields.

● withstand thermal cycling

Thermal cycling is the process when a material gets warm and cold repeatedly, and some of the materials can hardly withstand the stress of the thermal cycling, which leads to premature failure during the machining works.

However, the gray cast is capable of withstanding the stress that is given from the thermal cycling well, and makes the machining works of the workpieces that are made of gray cast go smoothly without easily failing.

● oxidation resistance

The gray iron also performs well in the oxidation resistance, which is caused during the interaction of oxygen and iron. The interaction between oxygen and iron may occur rusting on the surfaces of an accessory or component, and damage or destroy the machines or other products that are made of iron.

While applying the gray cast in the making of products can prevent corrosion from easily happening, since it has a high anti-rust capability, which is another attractive feature of the gray cast.

:: Read more : Gray Iron Properties and Grades Explained

Where can gray cast be applied for?

Since the gray cast is the cheapest in the price, it is able to withstand vibration and thermal cycling when the products that are made of it are operated. What’s more, the thermal conductivity in the gray cast is also greater than other iron castings, the gray cast is widely applied for a wide range of applications.

For the vibration dampening ability of the gray cast, it can be used in the automotive suspension components, steering knuckles, tractor parts, truck suspension components, other truck parts, or machinery bases.

For the great thermal conductivity and the capability in withstanding thermal cycling, the gray cast is also suitable for stove parts and wind turbine housings.

In addition, the gray cast has a high anti-rust capability, which makes corrosion less possible to be caused when the oxygen and iron come in contact with each other, such as in the water. Therefore, the gray cast is also applied for the production of hydraulic components, pumps, valves, weights and counterweights, and piston rings.

Gray cast vs. nodular cast

Among all the types of iron casting, in addition to the gray cast, the nodular cast is also widely used in the machining works or the making of other products nowadays. 

These two types are both made of the alloy of graphite, while there are some variations between them, which makes them suitable for different applications in the industrial fields, including the structure, the tensile strength, and the yield strength.

● structure

As the above introduction has mentioned, the gray cast is made of the alloy of the flakes of graphite, which makes the gray appearance and other physical properties of the gray cast.

The nodular cast is also the alloy of graphite, while the structure of the nodular cast is in the form of balls instead of flakes. This makes the biggest difference in the appearance of the gray cast and the nodular cast. 

Due to the difference in the structure between the gray cast and the nodular cast, the features such as the tensile strength and the yield strength would be different accordingly, as in several perspectives, an object that is made as the shape of a ball would be more flexible than the object that is presented as a flake.

● tensile strength

The tensile strength means the maximum amount of tensile stress that the material can take in the process of shaping before failure, such as cracking or fracturing.

The nodular cast surpasses the gray cast in this feature, as it owns better tensile strength than the gray cast. The nodular iron's maximum tensile strength is 90000 psi, and gray iron's maximum tensile strength is just 35000 psi. Therefore, the time that the nodular cast undergo machining works can last longer than the gray cast accordingly.

● yield strength

The yield strength, which is the stress that the nodular cast can withstand before permanent deformation or keeping the ability to return to the original dimensions, is up to 40000 psi and thus better than the gray cast, too. 

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