In mechanical manufacturing, how are seamless pipes produced? Select the method that correctly describes true seamless pipe manufacture, as used for pressure service and high-integrity applications.

Introduction / Context:
Seamless pipe is specified where weld integrity and isotropic properties are critical, such as high pressure, cyclic service, or corrosive duty. Understanding how seamless pipe is truly manufactured helps designers choose correct materials and interpret data sheets and code requirements.

Given Data / Assumptions:

• Seamless pipe implies no longitudinal weld seam.
• Conventional industrial methods include rotary piercing (Mannesmann process), extrusion, rolling, and drawing.
• Welded pipe (from plate or strip) is not seamless, even if heat treated.

Concept / Approach:
In the most common route, a solid billet is heated, then pierced using a rotating piercer over a mandrel. The hollow shell is elongated and sized by rotary rolling and/or plug-mandrel mills. Final dimensions and properties are achieved by hot or cold drawing. This produces a pipe with no weld seam and the microstructure of a wrought product.

Step-by-Step Solution:
Identify which choices yield a pipe with no weld seam and a wrought microstructure.Rolled strip + seam welding creates a longitudinal weld → not seamless.Casting (static or centrifugal) produces cast tubes, not wrought seamless pipe for pressure service.Rotary piercing + rolling/drawing yields true seamless pipe.

Verification / Alternative check:
Standards (e.g., ASTM A106/A53 Type S) describe seamless manufacture by hot working a steel billet, usually with piercing and rolling, optionally followed by cold finishing.

Why Other Options Are Wrong:
(a) is welded; (b) produces cast tubes lacking wrought properties; (d) includes an incorrect method; (e) unnecessary because a correct method exists.

Common Pitfalls:
Confusing centrifugal cast pipe (used for some services) with seamless; assuming post-weld heat treatment makes welded pipe “seamless.”

Final Answer:
By forging a solid round, piercing it while rotating over a mandrel, then reducing by rolling and drawing