Effects of mandrel shape on deformation behavior for hot mandrel bending of elbows


  • H. Naoi
  • H Takagi
  • N. Tsugawa
  • A. Hozumi
  • S. Kawanishi
  • S-T. Jang
  • M. Wada
  • T. Yamakawa
  • T. Kurita
  • H. Sakai
  • T. Maruyama


Elbows of steel pipe joints are used in the industrial plants and are mainly manufactured by the hot mandrel
bending from raw material of straight steel pipe. Elbows are generally manufactured at elevated
temperature by means of pushing, expanding and bending of pipes simultaneously, using the inner
tool of mandrel. Characteristics of mandrel bending strongly depend on the integrated shape and
dimensions of the mandrel. We investigate the effects of shape and dimension of mandrel on deformation
behaviors for hot mandrel bending of elbows, conducting experimental test and numerical analysis. We
clarify the effects of bending radius ratio Rout/Dout, expansion ratio Dout/Din, mandrel length ratio L/Dout
and other items of mandrel shape. And optimum conditions of mandrel are estimated as conclusion.