Failure Analysis of TU2 Copper Joint of 390 MW Stator Coil in Preheating Process
TU2 copper joint of 390MW turbo generator stator coil generates surface blistering in the preheating process before welding.The analysis results show that a certain amount of oxygen being in the TU2 copper joint material of 390 MW stator coil and using water-gas(H2+ CO) in the hot forging process are the main reasons for surface blistering after preheating in medium frequency induction furnace.To eliminate the blistering caused by "sickening hydrogen",the oxygen-free copper with lower oxygen should be used in the TU2 copper joint of 390MW stator coil,or the hot forging heating approach of copper joint should be changed into resistance furnace heating.