the production of seamless metal pipe and tubing by rolling on special mills, called tube-rolling units. Seamless pipe and tubing—by which is meant products without longitudinal or spiral welded seams—is widely used in the manufacture of automobiles, tractors, aircraft, and boilers. It is also used in various other branches of the machine-building industry, in petroleum extraction, in the chemical industry, and in public works. Tube rolling includes the production of both hot-rolled pipe and cold-rolled pipe, which is first hot-rolled and then cold-rolled.
The tube-rolling process uses a wide range of rolling mills, which differ in the method of rolling and the size and type of pipes produced. Hot-rolled pipe with an outside diameter of 25–700 mm and a wall thickness of 2.5–75 mm and cold-rolled pipe with an outside diameter of 8–450 mm and a wall thickness of 0.08–20 mm are available. The type of tube-rolling equipment and its location in the shop depend on the method of production, the operating conditions, and the required pipe specifications.
Tube rolling usually consists of two main operations and several auxiliary operations. The first operation, piercing, consists in the formation of a longitudinal opening in a round bar or billet, forming a thick-walled pipe called a shell. In the second operation, plug rolling, the pierced bar or billet is elongated and its wall thickness is decreased to the approximate dimensions required for the finished pipe. Both operations are performed in one heating. The first operation is performed on piercing mills by rotary rolling between barrel-shaped or mushroom-shaped rolls on a short mandrel. The second operation is performed on continuous, short-mandrel, Pilger, or three-high thread-rolling mills. After plug rolling, the pipe is sized in special sizing mills and is then cooled, straightened, and inspected. Pipe and tubing less than 70 mm in diameter undergo additional hot-rolling on a reducing mill (seeREDUCING).
After hot-rolling, the pipe is cold-rolled on special longitudinal intermittent-acting mills and is also cold-drawn. These operations are intended to decrease its diameter and wall thickness, to improve its mechanical properties, and to obtain a smooth surface and exact dimensions.
Contemporary tube rolling is characterized by high labor productivity, by automation and mechanization of most basic and auxiliary technical operations, and by the availability of a wide range of high-quality rolled pipe and tubing. Since 1968 the USSR has been the leader in world production of seamless pipe and tubing; in 1975, its production was 16 million tons.
REFERENCESProkatnoeproizvodstvo: Spravochnik, vols. 1–2. Moscow, 1962.
Danilov, F. A., A. A. Gleiberg, and V. G. Balakin. Goriachaiapro-katka ipressovanie trub, 3rd ed. Moscow, 1972.
A. I. TSELIKOV