Gray iron, or gray cast iron, is a material type of cast iron with graphitic microstructure. We call this kind of material gray iron because of the gray color of the fracture. For the graphite lubricating the cut and breaking up the chips, gray iron is a common cast alloy due to its relatively low cost and good machinability. Besides, because the graphite flakes self lubricate, it also has good galling and wear resistance.

Gray iron also has less solidification shrinkage than other cast irons because of the graphite microstructure. Whe casting, the silicon element can promote good corrosion resistance and increase fluidity when casting. Gray iron is generally considered easy to weld. Compared to other iron castings, gray iron has a low tensile strength and ductility; that is why the impact and shock resistance of this kind of material is almost non-existent.

Frequently Used Gray Iron Grades

Heat Treatment of Gray Iron Castings

Most of the time, gray 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 of Gray Iron Castings

Gray 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.

Gray iron casting is used in many market segments, including automotive, agricultural, machinery building, electronics, irrigation, ventilation, architecture, construction and transportation industries.