Difficulty: Easy
Correct Answer: 1.5% to 5.5% carbon
Explanation:
Introduction / Context:
Iron–carbon alloys are broadly divided into wrought/steel and cast iron by carbon percentage and microstructure. Recognizing the carbon range is essential to predict properties, processing, and typical products.
Given Data / Assumptions:
Concept / Approach:
Cast irons typically contain about 2–4% carbon, with practical ranges extending from roughly 1.7% to above 4.5% depending on type (white, grey, ductile, malleable). A generous exam-friendly span of 1.5% to 5.5% safely envelops standard cast-iron varieties, while steel grades rarely exceed ~1.5% C.
Step-by-Step Solution:
Verification / Alternative check:
Handbooks list cast iron families within ~2–4% C as typical; specialized compositions may deviate but stay within the broad 1.5–5.5% assessment range.
Why Other Options Are Wrong:
0.05–1.75%: that is wrought/steel territory. 0.250%: a single value, not a range, and within mild steel. “None” and 0.8–1.2% do not represent cast iron composition.
Common Pitfalls:
Confusing carbon ranges of steels and cast irons; ignoring graphite’s role in classification.
Final Answer:
1.5% to 5.5% carbon
Discussion & Comments