| 摘要 |
PURPOSE:To produce a seamless pipe without any limit in length by delivering a heated metallic bar material while reducing its diameter with three pieces of rolls, and hollowing the same with a mandrel on the roll outlet side then cooling the same and drawing the pipe with a drawing die. CONSTITUTION:A carbon steel bar material 1 is heated to 1,100-1,200 deg.C with a heater 2, and is inserted into three pieces of rolls 3. The rolls 3 are provided with tapered surfaces 4 for reducing the diameter of the material 1 and tapered surfaces 5 for wrapping the material around a mandrel 6 to be described later. These rolls are disposed by deviating the axial lines thereof in a constant direction with respect to the material 1. As the rolls 3 revolve, the material 1 among the rolls 3 is fed in an axial direction while revolving around the axial center of the material 1. On the outlet side of the rolls 3, the leading end of the spindle type mandrel 6 is disposed opposite to the center of the material 1, and the central part of the material 1 is hollowed by this mandrel, whereby a pipe blank material is made. Next, the pipe blank material is cooled to 600-800 deg.C with a cooler 7 to increase strength, after which it is drawn with a drawing die 8, whereby the seamless steel pipe having no limits in length is produced. |
