The forming process of ring forging can be divided into ring material biting stage, stable forming stage and forming end stage. In the steady forming stage of ring material, the feed speed and rotational speed are little, and the speed change is small, and it is in the approximate static equilibrium state.

　　輾環類似軋鋼的穿孔輾壓成形，環形鍛件連續咬人孔型是使環料轉動并實現穩定輾壓成形的必要條件。環料咬人孔型的力學模型如圖6—3—1所示。圖中，P1和T1分別為驅動輥對環料的正壓力和摩擦力，P2為芯輥對環料的正壓力(芯輥為空轉輥，它隨環料一起轉動，沒有摩擦力矩作用，所以芯輥對環料摩擦力的合力為零，而僅有正壓力)。

　　Ring piercing rolling is similar to steel rolling, and the continuous bite pass of ring forging is the necessary condition for the rotation of the ring and stable roll forming. The mechanical models of the ring pass are shown in figures 6 - 3 - 1. In the figure, P1 and T1 respectively to drive positive pressure and friction roller of ring material, P2 as the core and positive pressure on the ring material (core roller for idle roll, it rotates with the ring material, no friction torque, so the core roller ring material friction force is zero, and only positive pressure).

　　令a1和a2分別為驅動輥和芯輥與環料的接觸角，R1和R2分別為驅動輥和芯輥的工作半徑，h0和h1分別為環料在孔型人口處和出口處的壁厚，Ah=h0一h為環形鍛件在孔型中每轉壁厚減小量，n1為驅動輥轉速，L為接觸弧長在進給方向的投影長度。

　　A1 and A2 were the driving roller and the core roller and ring material contact angle, R1 and R2 respectively the working radius of driving roller and roller, H0 and H1 respectively in the ring material entrance and exit hole wall thickness, Ah=h0 h ring forgings in the pass thickness reduction per turn a small amount of N1, the drive roller speed, L projection length in the feed direction of the contact arc.

　　為使環形鍛件咬入孔型，則環料的拽入力必須大于或等于它的推出力，而進給方向環料的受力狀態是平衡的。

　　In order to make the circular forging bite into the groove, the pulling force of the ring material must be greater than or equal to its pushing force, and the force state of the feed direction ring material is balanced.