Abstract: This paper introduces the manufacturing device and forming process for U-shaped medium-frequency induction hot bending of Cr25Ni35Nb+MA centrifugally cast steel pipe. By analyzing the material properties of centrifugally cast steel pipe, the reasonable heat treatment process before bending, propulsion rate, heating temperature and cooling mode are selected. Meanwhile, the paper analyzes the change rule of wall thickness reduction rate, ovality and flatness after the forming of U-shaped pipe. The quality of the formed product is checked by penetration test, microstructure observation, pigging test and hydraulic test. The test results indicate that the heat treatment before bending can reduce the bending cracks; qualified bent pipe can be obtained by selecting the process with propulsion rate of 30~50 mm/s, heating temperature of 850~950 ℃ and strong air cooling.

Key words: Cr25Ni35Nb+MA, centrifugally cast steel pipe, U-shaped, medium-frequency induction