Properties of Gray Cast Iron

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Published: 10th November 2010
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Gray cast iron can be regarded as carbon steel as matrix organization with graphite flakes added. Gray cast iron can be divided into three categories according to the different matrix organization: ferritic matrix of gray cast iron, pearlitic gray cast iron matrix, ferrite and pearlite matrix of gray cast iron.

The mechanical properties of gray cast iron are related with the matrix organization and the morphology of graphite.

Flake graphite in gray cast iron can form serious fragmentation, and graphite could easily lead to stress concentration at sharp corners, so that the tensile strength of gray cast iron, plastic and toughness will be much lower than cast steel, but it has the same compressive strength with cast steel. Therefore, the mechanical properties of gray cast iron is also taken as most normal or even the worst cast iron.

Meanwhile, the matrix organization of gray cast iron have an impact on its mechanical properties. The graphite sheets in ferrite matrix of gray cast iron are thick, which cause the lowest strength and hardness, it is seldom used. The graphite sheets in pearlitic matrix of gray cast iron are small, so have higher strength and hardness. Therefore, this kind of gray cast iron is mainly used to manufacture the more important iron castings. The graphite sheets in ferrite and pearlite matrix of gray cast iron are thicker than pearlitic gray cast iron, so its mechanical properties are worse. Therefore, the gray cast iron of pearlite matrix has wider application.

Although the gray cast iron has poor mechanical properties, it has good casting properties, good vibration damping, good wear resistance, good machinability and low notch sensitivity, and most important, lower production cost. Therefore, gray cast iron has wide range of uses in many areas.

For class 100 and class 150 gray iron, it can be used to produce protective cover, cover body, hand wheels, frame, floor, hammer, handle, frame, box, bed, bearing, bench, pulleys, pump body, valve, pipe, flywheel and so on.

For class 200 and class 250 gray iron, it can be used to produce cylinder, gear, base, flywheel, bed, cylinder block, cylinder liners, pistons, gear boxes, brake wheel, coupling plate, pressure valve and so on.

For class 300 gray iron, it can be used to produce heavy-duty machine tools, presses, bed, frame, high pressure hydraulic parts, piston rings, gears, cams, bushings, crankshaft, cylinder block, cylinder liner and cylinder head and so on.

For the gray iron material standards, please check normal material comparison table for grey iron between DIN, ISO, ASTM and GB.



This article was from Dandong Foundry Blog.

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