Hot Working of Metals — Choose the Correct Temperature Range In manufacturing metallurgy, “hot working” refers to plastic deformation performed relative to the material’s recrystallisation temperature. At which temperature range is hot working correctly carried out for metals?

Introduction / Context:
Hot working is a fundamental concept in metal forming used in rolling mills, forging shops, and extrusion plants. Understanding the correct temperature window ensures desired grain refinement, eliminates work hardening, and reduces forming loads. This question checks whether you can correctly identify the operational temperature range for hot working relative to the metal’s recrystallisation temperature.

Given Data / Assumptions:

• Recrystallisation temperature is the temperature at which new, strain-free grains nucleate and grow during or after deformation.
• During hot working, deformation and recrystallisation overlap (concurrent softening).
• Metals considered are typical engineering alloys like steel, aluminum, and copper alloys.

Concept / Approach:
When deformation is performed above the recrystallisation temperature, the metal continuously recrystallises as it is worked. This ongoing nucleation and growth of new grains counteracts work hardening, keeping flow stress relatively low and allowing large shape changes without cracking. This also improves ductility and refines microstructure if parameters are controlled.

Step-by-Step Solution:
Define target window: hot working must be done above the recrystallisation temperature of the alloy.Relate to forming load: above this temperature, flow stress is reduced, enabling large reductions.Relate to microstructure: continuous dynamic recrystallisation limits work hardening and can refine grains.Therefore, the correct selection is “above the recrystallisation temperature”.

Verification / Alternative check:
Practical evidence: hot rolling of steel typically occurs at temperatures well above the steel’s recrystallisation temperature, producing manageable loads and favorable microstructures.

Why Other Options Are Wrong:
At/below recrystallisation temperature: this is warm or cold working, where work hardening dominates and loads are higher.At any temperature: too imprecise; metallurgical behavior is temperature-dependent.Not applicable: contradicts standard definitions.

Common Pitfalls:
Confusing recrystallisation temperature with melting point; these are distinct and material-specific.Assuming “hot” simply means “high”—it must be high relative to recrystallisation, not an arbitrary number.

Final Answer:
above the recrystallisation temperature