Equivalent Grades of Grey Cast Iron from Different Countries

No. China Japan U.S.A. ISO Germany France Russia U.K.
1 HT100 FC100 GG10 0.6010 EN-GJL-100 гч10 Grade 100
2 HT150 FC150 150/~No.20 F11401 ISO 185/JL/200 GG15 0.6015 EN-GJL-150 гч15 Grade 150
3 HT200 FC200 200/~No.30 F12101 ISO 185/JL/0 GG20 0.6020 EN-GJL-200 гч18 гч20 гч21 Grade 180 Grade 220
4 HT250 FC250 250/~No.35 F12401 ISO 185/JL/150 GG25 0.6025 EN-GJL-250 гч24 гч25 Grade 260
5 HT300 FC300 300/~No.45 F13101 ISO 185/JL/150 GG30 0.6030 EN-GJL-300 гч30 Grade 300
6 HT350 FC350 350/~No.50 F13501 ISO 185/JL/150 GG35 0.6035 EN-GJL-350 гч35 Grade 350

Gray iron is cheaper than ductile iron, but it has much lower tensile strength and ductility than ductile iron. Gray iron can not replace the carbon steel, while the ductile iron could replace the carbon steel in some situation due the high tensile strength, yield strength and elongation of ductile iron.

gray cast iron chemical composition

Gray Iron Chemical Composition

mechanial properties of gray cast iron

Mechanical Properties of Gray Cast Iron

Gray iron, or grey cast iron, is a type of cast iron that has a graphite microstructure. It is named after the gray color of the fracture it forms. The gray cast iron is used for housings where the stiffness of the component is more important than its tensile strength, such as internal combustion engine cylinder blocks, pump housings, valve bodies, electrical boxes, counter weights and decorative castings. Grey cast iron's high thermal conductivity and specific head capacity are often exploited to make cast iron cookware and disc brake rotors.

A typical chemical composition to obtain a graphitic microstructure is 2.5 to 4.0% carbon and 1 to 3% silicon by weight. Graphite may occupy 6 to 10% of the volume of grey iron. Silicon is important to making grey iron as opposed to white cast iron, because silicon is a graphite stabilizing element in cast iron, which means it helps the alloy produce graphite instead of iron carbides; at 3% silicon almost no carbon is held in chemical combination with the iron.

The graphite takes on the shape of a three-dimensional flake. In two dimensions, as a polished surface will appear under a microscope, the graphite flakes appear as fine lines. The tips of the flakes act as preexisting notches; therefore, it is brittle. The presence of graphite flakes makes the Grey Iron easily machinable as they tend to crack easily across the graphite flakes. Grey iron also has very good damping capacity and hence it is mostly used as the base for machine tool mountings.