To contrive reduction of flaws on the outside surface to which a guide is related and prolongation of the life of the guide in rolling with an elongator.
In the case that a hollow tube stock after piercing with a piercer is elongation rolled with an elongator, by taking the ratio Lx/Lcmax of the contact length Lx in the axial direction of tube between a plug and a material to be rolled to the max. value Lcmax of the projected length Lc of the arc of contact in the peripheral direction as Lx/Lcmax≤6.4 and the max. value Rtmax of thickness draft Rt every a half turn as Rtmax≤30%, where, Rt=(ta-tb)/ta (tb is the clearance between the roll and the plug in the position in the axial direction of the tube where the thickness draft is calculated, ta is the clearance between the roll and the plug in the position in the axial direction of the tube before a half turn from the position in the axial direction of the tube.) and rolling is executed. In this way, the reduction of the flaws on the outside surface to which the guide is related and prolongation of the life of the guide is contrived.
TAKAKU KENICHI
SAKAMOTO TOSHIHARU
KOSHO KOICHI
WADA YASUHIRO
