Ferrous metallurgy — wrought iron contains carbon up to approximately what percentage by mass?

Introduction / Context:
Classifying ferrous metals by carbon content is fundamental to understanding their properties and applications. Wrought iron is historically produced by repeated working of low-carbon iron with slag stringers, yielding excellent ductility and corrosion resistance but low hardenability and strength compared with steels and cast irons.

Given Data / Assumptions:

• The question seeks the upper limit of carbon content in wrought iron.
• Exam conventions often round values to simple percentages.
• Other constituents (slag, phosphorus) may be present in small amounts.

Concept / Approach:

Wrought iron is very low carbon, traditionally cited as containing up to about 0.08–0.15% C in many references; however, civil engineering question banks commonly accept an upper limit of “about 0.25%”. Values of 1.0%, 1.5%, or 2% carbon would place the material well into the steel or cast iron ranges, fundamentally changing microstructure and properties.

Step-by-Step Solution:

Verification / Alternative check:

Historic metallurgy texts and exam preparatory materials align wrought iron with a very low carbon content, typically cited below a quarter percent in rounded figures.

Why Other Options Are Wrong:

1.0% or 1.5% — firmly within high-carbon steels; 2% — cast iron territory; these would drastically reduce ductility and alter processing.

Common Pitfalls:

Confusing wrought iron with mild steel; ignoring slag inclusions that impart characteristic fibrous appearance without raising carbon content.

Final Answer:

0.25%