Malleable iron and non malleable iron

How to judge a cast iron is malleable iron, or it is not malleable iron? Or is there a clear definition between malleable and non malleable cast iron?

Actually, the answer is very simple, but the judgment will be difficult.

Firstly, if client required producing malleable iron, then they will advise the cast iron grades, such as DIN 1692, ASTM A47, A220, A197, A338. So, if the cast iron grades are in these standards, then they will be malleable iron.

Secondly, the production process of malleable cast iron is different with ductile iron and grey iron castings. Producing malleable iron needs a key heat treatment process, but most of gray iron and ductile iron castings will not need heat treatment.

Thirdly, their metallographic is very different, the graphite of malleable iron is cotton-like, but the ductile iron is ball-like, and gray iron is flaky.

As for their elongation, malleable iron could reach 2 to 12%, but gray iron is almost no elongation, ductile iron can reach from 2 to 22%. So, from elongation, you could judge malleable iron with gray iron, but can not judge it with ductile iron.

Actually, if client choose the malleable iron, most likely, they prefer some special properties of malleable iron, such as corrosion resistance, abrasive resistance, good machining capability and shock absorption.

However, malleable cast iron can not be forged. Malleable is only meaning this cast iron has good elongation under stress, but ductile iron is also meaning this point.

All in all, if client required to produce malleable iron, then you will have to produce the castings by malleable iron process, otherwise, it will not be malleable iron. However, if client just required the tensile strength and elongation, then you should consider to produce the castings by ductile iron because of lots of reasons. If you just export them, and need to assure if your casting parts are belong malleable iron to fill in the HS code, then ductile iron is also belong to malleable iron range. Only gray iron and cast steel are not belong to this range.

The followings are some typical casting parts made by malleable cast iron

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