Continuing from the last post from Piping & Fabrication, and we now will talk about Mannesman Plug-Mill Process and Ugine Sejournet Type Extrusion Processes.

Mannesmann Plug-Mill Process.
In the Mannesmann plug-mill process (Fig. A5.5) the billet may be pierced in two hot rotary piercers because of the greater reduction needed for medium size pipe and tube. Following the piercing process, the pierced billet is placed in a plug-mill, which reduces the diameter by rotating the tube over a mandrel.

FIGURE A5.5 Mannesmann plug-mill process

Having some ovality, the tube is next inserted between the rolls of reelers which provide for dimensional correction and burnish the inside and outside diameters of the tube. Finally, after reheating, the tube reenters a reeler and sizing rollers to provide for greater dimensional uniformity.

The Mannesmann plug-mill process is a standard process for making large quantities of thin-wall stainless steel tube or pipe of uniform size and roundness throughout its entire length.

Ugine Sejournet Type Extrusion Processes. The Ugine Sejournet extrusion process (Fig. A5.6) is used for high-alloy steel tubes and pipe such as those of stainless steel and specially shaped pipe. A descaled billet, heated to approximately 2300_F (1260_C), is placed in the vertical press compartment with an extrusion die at its bottom. After applying a hydraulic ram to the billet, a piercing mandrel within the ram punches the billet, producing a cylinder from which the punch piece is ejected through the extrusion die opening. Following this, the ram is activated to apply pressure to the billet, and the billet is extruded through the annulus formed between the piercing mandrel and die cavity. In horizontal presses, piercing is done as a separate operation, or a hollow is used with amandrel and die. Themandrels and dies are made of high-alloy steels containing tungsten, molybdenum, and chromium having Rockwell C hardness values of approximately 46. Powdered glass is the lubricant used in this process. Heavy-wall pipe in sizes NPS 8–48 (DN 200–1200), having a wall thickness ranging from 1 in (25 mm) to 6 in (150 mm), is extruded vertically to 45 ft (14 m) lengths using procedural steps in the Ugine Sejournet process and a graphite lubricant. These large extrusions of carbon-, alloy-, and nickel-based materials include ASTM specifications A 106, Grades B & C; A 312; A 333; A 335; A 376; B 167; and B407. Heavy-wall pipe per ASTM A335, Grades P11, P22, and P91 is increasingly being used in power generation. In addition, heavywall pipe is utilized in offshore oil drilling and production.

FIGURE A5.6 Ugine Sejournet extrusion process