Gray Iron Castings

Introduction To Grey Iron Castings

Grey iron castings are typically made by smelting pig iron. They are an alloy of iron and carbon. Grey iron castings also have traces of phosphorous, sulfur, silicon, and manganese in them. The reasons of grey iron castings are popular are their cost efficiency and capability to be made into complex frameworks.

Grey Iron (or gray iron) is the most common type of ferrous cast material in the world. It is named after the gray color of the fracture surfaces created by it. It is caused by the presence of graphite.

Gray Iron is commonly used in static castings where the rigidity or stiffness of the part is more important than the tensile strength or elongation. Such as engine blocks, various housings, valve bodies, mold castings.

Common Grey Iron Grades and Chemical Content

Gray IronWall thickness/mmCSiMnP≤S≤
  • Class 25
  • Class 30
  • Class 35
  • Class 40

Best Use For Gray Iron Castings

There are numerous uses for grey iron castings and they are usually classified into categories based on their Grade.

Class 300 Grey Iron is mostly used in the production of beds, gears, cylinder blocks, heavy-duty machine tools, high-pressure hydraulic components, cylinder heads, bushings, piston rings etc.

Class 200 and Class 250 are mostly suitable for manufacturing cylinder bases and liners, brake wheel, gearboxes, coupling plate, flywheel and pressure valves.

Class 100 and Class 150 category are typically utilized for creating hammers, pipes, pulleys, protective covers, hand wheels, bearings and pumps. Grey iron castings are the optimal choice for the construction of highly durable and strong products.

Gray iron castings are manufactured easily and have good machinability. They are typically used in applications where strength is important, but not the main required property:

  • PumpsBrackets
  • HousingsSteering Knuckles
  • Weights & Counter
  • Compressors
  • Powertrain PartsSuspension ComponentsEnd PlatesValves and FittingsPulleysLinkagesBuilding facadesTable legs and bases

Advantages of Gray Iron Castings

  • Gray iron casting is durable, low-cost solution, with heat dissipation, and high density. 
  • Gray iron has good fluidity and is easily machined.

Different tensile strengths.

Such as 6 tons or even 18 tons/ The average tensile strength is around 7 tons/

It is possible to increase their strength easily by adding vanadium if has specific applications.

Withstand large amounts of compressive forces.

Its high compressive strength is about three times more than its tensile strength. This is the foremost reason as to why they are a premier choice for huge posts and columns in big buildings.

Grey iron castings have high damping capacity and excellent machining capabilities. This makes them perfectly suitable for all types of machine bases, cylinder blocks, brake parts. Since its damping capacity is about 20-25 times higher than steel and also other iron types. It reduces vibration, inaccuracies as well as excessive wear and tears on machinery and bearings.

Grey iron castings are highly resistant to oxidation. prevent rust. Grey iron castings are the ideal solution to overcome problems of corrosion.

There are numerous uses for grey iron castings. They are usually classified into categories based on their Grade.

Gray Iron Castings Microstructure

Gray iron derives its properties from flake graphite in its microstructure. Its unique attributes include excellent machinability. When the composition of the molten iron and its cooling rate are suitable, the carbon in the iron separates during solidification and forms interconnected graphite flakes. The graphite grows edgewise into the liquid and forms the characteristic flake shape.  The properties of gray iron also are influenced by the relative hardness of the metal matrix, which is the iron that surrounds the graphite. Microstructural properties are primarily controlled by the carbon and silicon content of the metal and the cooling rate of the casting.

Grey Iron Casting Process

Sand casting is the Common process for grey iron castings in the market

As the mold media, sand has a similar effect on the rate of solidification of the casting. But the permanent mold process has a distinct effect on structure and properties.

In JC Casting foundry, we can make grey iron castings in two types:

Resin Sand Casting

The resin sand casting process is mainly for small and medium castings.

Compare with other sand casting processes, resin sand casting is more precise. It is close to investment casting. As good rigidity of resin sand and high strength of sand mold when early casting. Then we could effectively eliminate the defects of the gray iron casting of the shrinkage cavity, shrinkage.

Lost Foam Casting

The only investment casting process for cast iron components. It has lots of advantages to produce small gray iron investment castings. Such as saving mold cost, shortening the production cycle and improving production efficiency.

Grey Cast Iron Supplier

Whether you’ve designed the part in-house or you need a partner to assist with casting design, JC Casting is able to produce your cast iron part on time and on budget. We are capable of handling all aspects of gray iron castings, from casting and machining to coating and assembly.

Grey iron casting is used in many market segments, including automotive, agricultural, machinery building, electronics, irrigation, ventilation, architecture, construction and transportation industries. we can make custom grey iron casting for any industries. Pls contact us if you have any demand of such products.

What we can do


Our gray iron castings are available in several material grades. Including ASTM A48, ASTM A159 and SAE J431. We also supply other specialty grades including ASTM A436 (ni-resist) and customer specific chemistries.


We work with a wide range of foundries to insure we can provide you the exact size casting your project needs. Our gray iron castings weight range stretches from a few ounces up to 10,000 pounds, and our max envelope size is approximately 70” x 70”.


We offer gray iron castings in a range of volumes. From prototype castings using 3D printed sand molds, up to production casting running in the hundreds of thousands. We likely work with a gray iron foundry that can meet your exact needs.

JC provides high quality gray iron castings to customers all around the word.

Heat Treatment

Most of the time, grey iron castings are supplied to our customers in the as-cast condition directly. But For some purposes, gray iron castings can also be heat treated.
such as to relieve residual stresses, improve machinability, increase the hardness of the surface either through induction or flame hardening, or harden the entire section through an oil quench and draw treatment. Such heat treatment will not change the graphite structure. Although the graphite may increase in volume if a pearlitic iron is completely ferritized, in which case, the graphite is usually deposited on the flakes originally present. The matrix however is quite responsive to heat treatment just as in the case of steel.

Machining Capability

Grey iron supply a hardness level that is machinable. With machining facilities in house, we can do machining also after casting. Once our customers have machining requirement on grey iron castings, it will be best to supply us both casting and finished drawings. Our engineering team will strictly machine products referring to the machining drawings. Our machining capability can greatly reduce additional cost for our customers.