Malleable cast iron is made of white cast iron. And white cast iron is made of hot liquid iron with certain chemical composition. White cast iron needs to be carburized, such as graphitization or oxidation and decarburization, and then its metallographic structure or chemical composition will change. Thus it can become malleable cast iron.
Compared with gray cast iron, malleable cast iron has better strength and ductility. It has better impact resistance especially at low temperatures.
Malleable cast iron has better wear resistance and shock absorption, compared with cast steel
Compared with ductile cast iron, both have good strength and ductility. However, malleable cast iron has better impact resistance. Meanwhile, the ductile iron has better wear resistance.
There are several types of malleable cast iron.
Black core malleable cast iron
Black core malleable cast iron is mainly used to produce cast iron parts with impact, shaking or torsion functions. The main application of this material is producing rear axle housing castings, spring brackets, low pressure valve bodies, pipe fittings, tools and wrenches. We can also call black core malleable cast iron as ferritic malleable cast iron.
Pearlitic malleable cast iron
Pearlitic malleable cast iron has higher strength, hardness and wear resistance. Therefore, it is mainly used to produce wear-resistant parts for power machinery and agricultural machinery.
White core ductile cast iron
White core ductile cast iron is rarely used due to its long elongation process.
The good physical properties of malleable cast iron are due to its microstructure. The graphite inside is in the form of agglomerated flocs, so the graphite has a low tearing function to the ferrite. The following is a metallographic photo of the graphite microstructure in malleable cast iron.
In the past, many foundries produced malleable iron parts. However, with the development of ductile iron, most malleable iron parts can be replaced by ductile iron. Therefore, only a handful of steel foundries in China are still producing this material.
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