Cast iron composition: approximately what carbon content range characterizes cast iron in foundry and structural applications? Choose the correct range.

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:

  • We classify by total carbon (combined + graphite) in equilibrium terms.
  • Cast irons solidify with eutectic/ledeburitic structures at higher carbon contents.


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:

1) Recall the eutectic region and graphite formation favor higher carbon.2) Compare options: 1.5–5.5% includes the usual 2–4% window.3) Therefore, select 1.5% to 5.5% carbon.


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

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