Optimization of Forging Process Parameters and Anvil Design for Railway Axle During High-Speed Forging

Abstract

Forging is an effective method for railway axle in order to ensure the inner quality, good microstructure and properties. Based on the disadvantage of current processing techniques for railway axle forging such as large machining allowance, low dimension accuracy, materials and energy consumption, a new precision high-speed forging forming process is proposed. The whole forging process of axle is divided into three steps, including chamfering, rounding and forming. Forming qualities of railway axle mainly depend on anvil structure and operational parameters during high-speed forging. Simulation model is established using finite element method by DEFORM. Focusing on the forging stage of the railway axles, the influences of anvil design have been numerically analyzed. By analyzing the stress-strain distribution and the forming precision with different anvil structures (flat anvil and arc anvil), a new arc anvil for axle forging is proposed. Arc anvil which we put forward is better than flat anvil both forming quality and properties. As for anvil edge shape design, it is effective to select a Per-form zone to obtain high strain at the center. Structure and main parameters are designed. Effect of anvil relative length, transition radius between Per-form zone and relative length, arc radius of arc anvil on forming quality is analyzed in term of surface defects and inner stress-strain distribution. While the radius of arc is 150mm and the central angle of the arc is 90°, the equivalent strain is greater which will be benefit for inner defects cogging. Transition radius between Per-form zone and relative length is 50mm, concave defects on the surface of forging is the smaller. With the increase of relative length, forging force increases. Taking the productivity and inner strain distribution into account, relative length is 240mm. The independent influence of each chosen major operational parameter, i.e, the rotation angle, the feed and the reduction on internal quality and dimensional precision, has been studied. Suitable operational parameters for ensuring internal quality and dimensional precision have been specified. As a result, the optimum combination of rotational angle and relative feed is clarified. Compared with stress-strain distribution and inner strain distribution under different reduction, 20% is taken to ensure better strain status and efficiency, rotation angle is 90°during chamfering. While the relative feed is 0.6, rotation angle is 45° during rounding, rounding precision will be higher. Ellipticity will be best and variance of radius will be small. Experiment research is performed in 10MN high-speed hydraulic press. Compared with the forming size precision, the experimental results verified the feasibility of the structure of arc anvil and the operational parameters.