Heat treatment objectives — normalising of steel: Normalising is performed primarily to achieve which of the following outcomes?

Introduction / Context:
Normalising is a widely used heat treatment for steels that improves microstructural uniformity, removes internal stresses, and refines grains. Designers and manufacturing engineers rely on normalising to obtain predictable mechanical properties before machining or further heat treatment.

Given Data / Assumptions:

• Process: austenitise above the critical range followed by air cooling.
• Applicable to carbon and low-alloy steels.
• No surface enrichment (like carburising) is intended during normalising.

Concept / Approach:
Normalising dissolves non-uniform microconstituents into austenite and, upon air cooling, forms a fine pearlitic or bainitic structure with reduced segregation. It relieves stresses from cold or hot working and refines grains compared with slower furnace cooling (annealing). The combined benefits justify the selection of option covering all listed outcomes.

Step-by-Step Solution:
Heat the steel to a temperature above A3 or Acm (depending on composition) to obtain homogeneous austenite.Hold sufficiently to dissolve carbides and equalize temperature.Air cool to produce a fine, uniform microstructure with reduced internal stresses.Results include grain refinement, removal of cold-work strains, and mitigation of hot-working defects.

Verification / Alternative check:
Mechanical tests show improved toughness and machinability after normalising compared with as-forged or as-rolled conditions.

Why Other Options Are Wrong:
Choosing any single outcome underestimates the multifaceted benefits of normalising.

Increasing carbon content by diffusion is not a feature of normalising; that would be case hardening like carburising.

Common Pitfalls:
Equating normalising with annealing; the former generally produces finer grains and higher strength relative to full annealing.

Final Answer:
all of the above