Based on the structure analysis of alternator poles, two closed die forging steps in one heat forming process of alternator poles were put forward, as well as the forming die system. Firstly, a thicker bottom base of alternator poles was per-formed by radial forging, then the middle boss and pole claw were forming on the bottom base by backward extrusion. A 3-D coupled thermo-mechanical finite element model was created. The billet deformation, metal flow and forming load were obtained. The results showed that a filling well forging without overlap defects could be obtained by this process, and that the forming load at the first step increased slowly, but the load increased sharply at the second step when the middle boss was filling completely by the former process. An improved process was put forward, which changed the flow mode in the second forging step, it can considerably reduce the final forging load.
 E. Korner and R. Knodler, “Possibilities in Warm Extrusion in Combination with Cold Extrusion,” Journal of Materials Processing Technology, Vol. 35, 1992, pp. 451- 465. http://dx.doi.org/10.1016/0924-0136(92)90334-O
 E. Doege and R. Bohnsack, Journal of Materials Processing Technology, Vol. 98, 2000, pp. 165-170. http://dx.doi.org/10.1016/S0924-0136(99)00194-6