17-4PH steel has low thermal conductivity and large billet size (cross section). It needs to be heated for a long time to reach the forging temperature. In order to shorten the residence time of forging billet in the high temperature furnace, it is generally required to preheat it for about 2h at 990-1020 ℃. Then put the preheated blank into the high temperature furnace for heating. When the temperature reaches the forging temperature (1180~1230 ℃), it should be immediately taken out of the furnace for forging after holding for about 1.5h to prevent overheating, overburning of the workpiece and similar copper rich phase precipitation of the alloy when the heating temperature is too high.

Principle and design requirements of bellows rotary compensator
The main elastic element of the corrugated compensator is the stainless steel bellows, which is used to stop the axial, transverse and angular compensation of the pipeline relying on the expansion and bending of the bellows. Its function can:
1. Compensate the axial, transverse and angular thermal deformation of absorption pipe.
2. Absorb equipment vibration and reduce the impact of equipment vibration on pipeline.
3. Absorb the deformation of pipeline caused by earthquake and ground subsidence.