Iron–Carbon System — Hyper-Eutectoid Steel Definition State whether the following is correct: “A steel with carbon content above 0.8% (the eutectoid composition) is known as hyper-eutectoid steel.”

Introduction / Context:Steel classification by carbon content relative to the eutectoid composition (approximately 0.77–0.8% C) is foundational in heat treatment. Terms like hypo-eutectoid and hyper-eutectoid describe the phases that form during slow cooling from austenite.

Given Data / Assumptions:

• Eutectoid composition ~0.8% carbon where austenite transforms to pearlite at the eutectoid temperature.
• Equilibrium/near-equilibrium cooling considered for microstructural terminology.

Concept / Approach:Hypo-eutectoid steels have carbon below the eutectoid composition and form proeutectoid ferrite plus pearlite. Hyper-eutectoid steels have carbon above the eutectoid and form proeutectoid cementite plus pearlite on slow cooling. Therefore, the statement given is correct by definition.

Step-by-Step Solution:Identify eutectoid carbon: ~0.8% C.Define hyper-eutectoid: C > 0.8%.Therefore, a steel above 0.8% C is hyper-eutectoid.

Verification / Alternative check:Fe–C phase diagrams and heat-treatment texts consistently set the eutectoid near 0.77–0.80% C, with terminology based on this dividing line.

Why Other Options Are Wrong:

• Disagree: contradicts standard definitions.
• Alloy qualification or higher thresholds: unnecessary; the definition is composition-based, not process-based.

Common Pitfalls:Confusing eutectic (liquid-to-solid) with eutectoid (solid-to-solid). The eutectoid for steel produces pearlite from austenite.

Final Answer:Agree