This process is also known as the rotary forge process, and – in Germany – after the name of its inventor, as the Ehrhardt process. It is employed for the manufacture of tube in the diameter range from approx. 50 to 170 mm with wall thicknesses from 3 to 18 mm and lengths up to 18 m. Modern push bench plants usually only produce one (large) hollow bloom size, leaving a downstream stretch- reducing mill to convert this into all the usual tube dimensions down to a smallest outside diameter of approx. 20 mm.

The starting material used may be square, octagonal or round blooms or billets, either rolled or of continuously cast material. Following  heating to forming temperature in a rotary hearth furnace, these are placed in the cylindrical die of a piercing press. A piercing mandrel then forms them into a thick walled hollow shell with a closed bottom. The hollow shell passes to an elongator, usually equipped with three rolls, where it is forged over a mandrel bar to approx. 1.8 times its original length.

This reduction process also produces greater wall thickness evenness. The hollow bloom is then elongated on the push bench, without reheating, to between 10 and 15 times its incoming length, using a mandrel bar as the internal tool.