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.
Flat Hooks, 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.
OEM Service Custom grey iron - Valve Housing
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.
Equivalent Grades of Grey Cast Iron from Different Countries | ||||||||||
No. | China | Japan | U.S.A. | ISO | Germany | France | Russia | U.K. | ||
GB | JIS | ASTM | UNS | DIN | W-Nr. | NF EN | гоÑÑ | BS | ||
1 | HT100 | FC100 | GG10 | 0.6010 | EN-GJL-100 | гÑ10 | Grade 100 | |||
2 | HT150 | FC150 | 150/~No.20 | F11401 | ISO 185/JL/200 | GG15 | 0.6015 | EN-GJL-150 | гÑ15 | Grade 150 |
3 | HT200 | FC200 | 200/~No.30 | F12101 | ISO 185/JL/0 | GG20 | 0.6020 | EN-GJL-200 | гÑ18 гÑ20 гÑ21 | Grade 180 Grade 220 |
4 | HT250 | FC250 | 250/~No.35 | F12401 | ISO 185/JL/150 | GG25 | 0.6025 | EN-GJL-250 | гÑ24 гÑ25 | Grade 260 |
5 | HT300 | FC300 | 300/~No.45 | F13101 | ISO 185/JL/150 | GG30 | 0.6030 | EN-GJL-300 | гÑ30 | Grade 300 |
6 | HT350 | FC350 | 350/~No.50 | F13501 | ISO 185/JL/150 | GG35 | 0.6035 | EN-GJL-350 | гÑ35 | Grade 350 |