Cast irons — Annealing white cast iron produces which product?

Introduction:
White cast iron contains carbon primarily as iron carbides (cementite), giving a hard and brittle structure. Heat treatment can transform its microstructure for improved ductility and toughness. Knowing the product of annealing is a classic materials question.

Given Data / Assumptions:

• White cast iron has a carbide network and ledeburite; very hard, brittle.
• Annealing is performed for prolonged times at elevated temperatures.
• Goal is to increase ductility for applications requiring some toughness.

Concept / Approach:

Annealing white iron decomposes cementite and promotes precipitation of temper carbon in the form of irregular nodules or clusters within a ferritic (or pearlitic) matrix, creating 'malleable iron'. This process improves machinability and ductility while reducing brittleness, making the material suitable for castings that must withstand some deformation.

Step-by-Step Solution:

Verification / Alternative check:

Metallurgical practice distinguishes white → malleable via anneal; grey iron and ductile (nodular/spheroidal) irons are produced by different solidification/chemistry methods rather than by annealing white iron.

Why Other Options Are Wrong:

A: Grey iron forms graphite flakes during solidification—not by annealing white iron. B/D: Nodular/spheroidal graphite irons require magnesium treatment of melt, not post-anneal of white iron. E: ADI is obtained by austempering ductile iron, a different route.

Common Pitfalls:

Confusing malleable iron's temper carbon with nodular graphite in ductile iron; their morphology and processing differ significantly.

Final Answer:

malleable iron