Effect of Heat Balance at Interface on Friction Welding of Equi-Diameter Bar Joints

Abstract

The authors have been studying the friction welding phenomena of same diameter bars and of different diameter bars of SUS304 austenitic stainless steel by brake type friction welding equipment. In any case, friction torque, burn-off rate and temperature of friction surface are close to the constant value, while constant axial pressure and friction speed are maintained. This may mean that equsai steady state arises at the friction surface. And, these three constant values might signify the thermal balance.
In this study, following relationship of thermal balance were assumed.
Q₁=Q₃+Q₄+ΔQ
Q₁ means the friction heat, that is a function of friction torque. Q₃ is the removed heat by thermal conduction, so it is in proportion to temperature gradient. Q₄ means the heat removed with upset collar, this factor depends on burn-off rate and temperature at friction surface. And, dQ includes generated heat by defomation and relesed heat to the airs.
Relation between Q₁ and Q₄ was examined by studying the mutual relationship among three constant values of steady state in the same diameter bar friction welding of 1020 mm. And Q₃ was examined by the extrapolation of Q₁ and Q₄ relation. This value of Q₃ was nearly the same value of Q₃ from the calculation of thermal conduction.
Assumed relationship was sufficiently adapted for experimental data.