EXPANDING METHOD OF SEAMLESS STEEL TUBE

摘要

PURPOSE:To product the material yield and large tubes efficiently and reduce the cost by inserting a seamless steel material into a sticky mantrel with a head tube diameter and reducing a thickness of the tube diameter while heating the spot subsequently in the vicinity of a taper part. CONSTITUTION:A seamless steel material 1 is inserted into a mandrel 1, where a taper part 22 and a parallel plug part 22 are provided with slopes on their edge, and a mandrel edge part 2 is fixed and supported by a chack 4. A material 1 is pushed by a pusher head 5 and a high frequency heating coil 3 around and in the vicinity of the taper 22 and the material 1 are heated by a ring-like gas burner, and tube diameter reducing thickness is discharged from a plug part 21 to reduce the deforming resistance and facilitate tube diameter reducing with less resistance. If a peripheral steel of the plug 21 is pressed, a tube diameter becomes more homogeneous and better. A smaller edge of the plug part 21 prevents the resistance by cooling shrink of the steel.