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Malleable Iron

Malleable Iron, with its full name "malleable cast iron" (English: Malleable Iron), is a type of cast iron material processed through specific techniques. Its core feature is that it combines the rigidity of cast iron with toughness close to that of steel. Contrary to the literal meaning of "forgable steel", it is actually an improved variety of cast iron, widely used in fields such as pipe fittings and mechanical parts.

I. Core Definition and Nature of Malleable Iron

The base material of malleable iron is white cast iron (a type of hard and brittle cast iron), which needs to undergo "annealing treatment" (long-term low-temperature heating followed by slow cooling) to change its internal structure. This process converts the brittle and hard iron carbide in white cast iron into ductile ferrite and graphite, eventually forming "malleable cast iron".

Despite the name "malleable", it cannot actually be forged and shaped like steel. However, compared with ordinary cast iron (such as gray cast iron), it has better impact toughness, tensile strength, and deformation resistance, and is not prone to brittle fracture.

II. Key Characteristics of Malleable Iron (Distinguished from Ordinary Cast Iron)

Excellent Toughness: Ordinary gray cast iron is prone to fracture when impacted. After annealing, the impact toughness of malleable iron can reach 15-30 J/cm² (gray cast iron usually only has 2-5 J/cm²). It can withstand a certain degree of vibration or external impact, making it suitable for scenarios requiring impact resistance, such as pipe connections and auto parts.
Good Machinability: Malleable iron has a smooth surface and uniform texture, allowing for easy cutting, drilling, and thread processing (e.g., manufacturing threaded pipe fittings). In contrast, ordinary cast iron is prone to chipping during processing due to its brittleness.
Moderate Cost: Compared with metals like stainless steel and copper, malleable iron has lower raw material (cast iron) and processing costs. Although it requires an additional annealing process compared to ordinary cast iron, it offers higher overall cost-effectiveness, making it suitable for mass production of small and medium-sized parts.

III. Typical Application Scenarios of Malleable Iron

Thanks to its balanced advantages of toughness, machinability, and cost-effectiveness, the most common application of malleable iron is in pipe fittings (i.e., "malleable iron pipe fittings"), such as:

Elbows, tees, pipe clamps, and union joints for water supply/heating pipelines;
Sealing pipe fittings for gas and fire-fighting pipelines;
In addition, it is also used in the automotive industry (e.g., brake shoe brackets) and the machinery industry (e.g., small gears, bearing blocks) — fields that require a balance between toughness and cost.

IV. Brief Distinction Between Malleable Iron and "Ductile Iron" (to Avoid Confusion)

Many people confuse malleable iron with ductile iron. The core differences between the two lie in "graphite morphology" and manufacturing process:

Malleable Iron: Graphite is in the form of "floccules". It is made by annealing white cast iron, has moderate toughness, and is suitable for small and medium-sized parts.
Ductile Iron: Graphite is in the form of "spheres". It is produced by adding spheroidizing agents (such as magnesium) to molten iron, has much higher toughness than malleable iron (close to that of steel), and is suitable for large load-bearing parts (e.g., water pipes, manhole covers, engine crankshafts).