花键轴振动挤压成形试验研究
Experimental Research on Oscillating Extrusion of Splined Shaft

针对花键轴挤压成形制造效率低、模具所受载荷大的问题,采用了一种新的振动辅助挤压成形工艺,并进行了花键轴成形试验、微观组织分析和硬度测试,揭示了成形载荷的主要影响因素及金属流动规律。试验设备为振动挤压机床,采用模数为1.75、齿数为10的花键轴挤压模具对直径为17.9 mm、材料为AISI1045A的棒料进行了振动挤压成形试验,模具每进给1 mm便回程0.5 mm,振动频率分别取10、15和20 Hz。结果表明:相比于直接挤压,振动挤压成形过程的成形力可降低将近25％,原因是在模具回程过程中润滑油得以流入模具与坯料的接触面,重新生成油膜,从而减小了摩擦力;在试验频率范围内,成形载荷随振动频率的提高而增大;振动挤压成形花键轴具有表面质量高、成形速度快、材料流动均匀的优点,且沿轴向齿顶圆直径变化小,成形精度高;与传统的直接挤压成形相比,振动挤压成形花键轴齿型部位的硬度降低了近10％,有利于成形。
In response to the problem that the conventional splined shaft extrusion method is short of efficiency and the forming force is large, this study adopted a new forming process, i.e., oscillating cold extrusion. The forming experiments of splined shaft were performed and the microstructure and hardness were examined. An extrusion die whose module of gear is 1.75 and the number of teeth is 10 was used to form the workpiece. The workpiece is an AISI 1045A bar stock with a diameter of 17.9 mm. Each time when the die moves ahead 1 mm, it would moves back 0.5 mm. Different oscillating frequencies at 10, 15, and 20 Hz were compared. The results showed that the forming force of oscillating extrusion decreased by nearly 25％ compared with conventional extrusion. The cause of friction reduction is that the lubricant film is rebuilt between the workpiece and the die during the back stroke. Comparison of the splined shafts made by oscillating extrusion and conventional extrusion shows that oscillating extrusion provides a better surface quality of the splined shaft and the material piling is reduced. The material flow in oscillating extrusion is better than that in conventional extrusion. So the change of the diameter of the addendum circle is little and the forming accuracy is high in oscillating extrusion. Hardness test showed that oscillating extrusion can decrease the hardness of splined shaft by 10％, which facilitates the formation of the spline