Rotary piercing is a hot working metalworking process for forming thick-walled seamless tubing. There are two types: the Mannesmann process and the Stiefel process.

What is Mannesmann milling process?

[′män·əs‚män ‚präs·əs] (metallurgy) A process for making seamless tubing by forcing a billet between the rolls of a Mannesmann mill so as to pierce the center, and then forcing the metal over a mandrel to form the central bore.

What is the meaning of Mannesmann?

: a process of making seamless tubes from metal billets by piercing.