Thread manufacturing — thread rolling as a process is primarily restricted to which class of materials due to required plastic flow at room temperature?

Introduction / Context:
Thread rolling is a chipless cold-forming process that displaces material to create threads. Unlike thread cutting, which removes material, rolling requires plastic deformation under significant compressive stresses, demanding adequate ductility in the workpiece.

Given Data / Assumptions:

• Cold forming by hardened dies imposes high contact pressure.
• No material is removed; material flows to form crests and roots.
• Process efficiency and surface integrity depend on material ductility.

Concept / Approach:

Materials suitable for thread rolling must exhibit sufficient ductility to plastically flow without cracking, typically low to medium carbon steels, aluminium alloys, copper alloys, and certain stainless steels in workable conditions. Very hard or brittle materials lack the plasticity to deform and are prone to surface cracking or die damage under rolling pressures.

Step-by-Step Solution:

Verification / Alternative check:

Industry practice specifies minimum ductility metrics for rollability, and suppliers often heat treat or select grades to ensure formability before rolling.

Why Other Options Are Wrong:

“Ferrous materials” is too narrow; many non-ferrous ductile alloys are rollable. “Hard materials” lack required plastic flow. “None of these” is incorrect because there is a clear correct class: ductile materials.

Common Pitfalls:

Assuming only steels can be rolled; overlooking that strength can be high yet ductility sufficient when properly processed.

Final Answer:

ductile materials