Surface Hardening — Fuel Source in Flame Hardening In conventional flame hardening of steel surfaces, is an oxy-acetylene flame commonly employed as the heat source before quenching?

Introduction / Context:Flame hardening is a surface-hardening method in which a high-temperature flame rapidly heats the surface of a steel component followed by immediate quenching. It produces a hard martensitic case while preserving a tougher core, similar in goal to induction hardening but with a different heating method.

Given Data / Assumptions:

• Workpiece is a hardenable steel (adequate carbon content).
• Heat input is localised and rapid.
• Quench follows shortly after the surface reaches the austenitising temperature.

Concept / Approach:An oxy-acetylene flame is widely used because it provides a concentrated, controllable heat source with high flame temperature, enabling quick austenitisation of the surface layer. After sufficient heating depth is achieved, water or polymer quench transforms the surface to martensite, yielding a hardened case while limiting distortion.

Step-by-Step Solution:Select heating method: oxy-acetylene torch with appropriate nozzle/travel speed.Heat to austenitising temperature for the steel grade.Immediately quench the heated zone to form martensite and achieve surface hardness.

Verification / Alternative check:Industrial practice and manuals list oxy-acetylene as the standard flame for flame hardening; induction hardening is a separate method using electromagnetic heating.

Why Other Options Are Wrong:“No” contradicts common practice; torches are typical in flame hardening.Stainless-only or cast-iron-only restrictions are incorrect; various steels can be flame hardened if carbon content allows.Carburising is not required; flame hardening relies on transforming existing carbon steel, not adding carbon.

Common Pitfalls:Confusing flame hardening with flame carburising; the latter adds carbon, while the former transforms by heating and quenching.

Final Answer:Yes