METHOD OF MANUFACTURE OF STEAM SUPERHEATING TUBES FROM ALLOYED STEELS Russian patent published in 2003 - IPC

FIELD: manufacture of steel tubes by hot deformation method for steam boilers. SUBSTANCE: proposed method includes multi-stage hot deformation, fast cooling at subsequent preheating to temperature below temperature of beginning of phase transformation by 10-30 C (point A₁) before last deformation stage and final deformation at this temperature; cooling is performed at rate more than 75 C/min but lesser than critical speed ensuring martensite transformation and higher than temperature corresponding to point A₁-350 C for this Grade of steel; holding at heat at this stage is no less than 30 s; after preheating holding at heat continues for no less than 10 min, after which final tempering is performed. EFFECT: reduction of heat treatment period; improved quality parameters (mechanical properties, linearity) of metal. 2 tbl