Plain-carbon steel classification by carbon percentage A steel containing 0.8% to 1.5% carbon is classified as which category in standard engineering terminology?

Introduction / Context:
Carbon content is the primary factor used to classify plain-carbon steels because it controls achievable hardness, strength, and response to heat treatment. Correct classification is essential for selecting materials for springs, tools, and wear-resistant parts versus ductile, easily formed components.

Given Data / Assumptions:

• Carbon range under consideration: 0.8% to 1.5% C.
• No significant alloying additions are implied.
• Standard nomenclature bands are applied.

Concept / Approach:
Conventional ranges are: dead-mild (≤ 0.15% C), mild/low-carbon (≈ 0.15%–0.30% C), medium-carbon (≈ 0.30%–0.60% C), and high-carbon (≈ 0.60%–1.0%+ C). Steels in the 0.8%–1.5% range are squarely within the high-carbon category and can achieve high hardness after quenching and tempering, suitable for springs, knives, and wear parts. Above about 1.0% C, brittleness increases and special processing is often required.

Step-by-Step Solution:
Map the given carbon range to standard categories.0.8%–1.5% C corresponds to high-carbon steels.Therefore select “high carbon steel”.

Verification / Alternative check:
Handbooks and standards list typical uses (springs, high-strength wires, cutting tools) for steels within 0.6%–1.0%+ C, confirming the “high carbon” designation.

Why Other Options Are Wrong:
Mild/dead-mild and medium-carbon steels have substantially lower carbon; “low-alloy steel” refers to deliberately alloyed compositions and is not a carbon-percentage class by itself.

Common Pitfalls:
Assuming “mild steel” covers all non-alloy steels; in engineering practice “mild” is low carbon, not high carbon.

Final Answer:
high carbon steel