Technology and tools for extruding large-diameter steel pipe

The USSR is presently preparing to begin producing several special large-size items: mono- and bimetallic steel pipes with outside diameters ranging from 630 to 1400 mm, wall thicknesses from 22 to 100 mm, and lengths up to 12 m; and disk-type forgings up to 2000 mm in diameter made of heat-resistant steels and alloys. The pipe-manufacturing technology is hot extrusion, which in the last decade has become much more popular for producing large-diameter steel pipes, in addition to the traditional methods of drawing out on hydraulic presses, rolling, forging, and centrifugal casting. The advantages of hot extrusion over other methods are lower production costs and higher product quality in such areas as dimensional and shape accuracy, surface conditions, mechanical properties, and metal structure. The technico-economic advantages of extrusion result from the large relative deformation (up to 90%) per forming operation, the ease of process control, and the ease of changeover from one size to another. In addition, extrusion has practically no limitations with regard to the grade of steels. The pipe extrusion process is described.