Tubular Operations can produce approximately 840,000 net tons of seamless tubular products every year. the process begins with solid steel rounds, or billets, being cut to a specified length and sent through a walking-beam reheat furnace, where temperatures reach nearly 2,300°F. the yellow rounds are turned into a tube shell in mere seconds in the rotary piercing mill as the preheated billets are cross-rolled between two barrel-shaped rolls at a high speed. the seamless shells enter mandrel mill, where they are rolled over a retained mandrel to provide the needed OD size and wall thickness for the next process. the process is carefully monitored using a state-of-the-art hot-wall measuring system. the shells are then reheated for final forming in a 24-stand stretch-reducing mill, where outside diameters are formed to customers’ exacting specifications. Wall thickness is again verified using a hot-wall measuring system.
after being rotated and advanced on the walking-beam cooling bed, the pipes are batch cut and transferred to an in-process storage area, where they are handled by computer-controlled gantry cranes.

Reference:

http://www.ussteel.com/uss/wcm/connect/ed30bc37-41a9-4293-a1c7-e7f31b06f1bb/Standard+%26+Line+Pipe+Catalog+FINAL.pdf?MOD=AJPERES&CACHEID=ed30bc37-41a9-4293-a1c7-e7f31b06f1bb