T2纯铜高速铣削刀具磨损对表面形貌的影响

The Influence of Tool Wear on Surface Morphology in T2 Pure Copper High Speed Milling

目的满足T2纯铜与日俱增的加工需求,改善T2纯铜的加工质量,探究不同铣削速度下刀具损伤和已加工表面形貌之间的内在联系。方法根据单因素试验结果,研究铣削速度对于刀具磨损的影响。在磨损刀具铣削力模型和已加工表面应力模型的基础上,从铣削力、刀具损伤形式以及磨损机理出发,分析刀具磨损对于已加工表面质量的影响,解析表面缺陷产生的原因,并通过光学和电子显微镜对磨损后的刀具表面形貌及已加工表面缺陷进行分类表征。结果当铣削速度较低时,刀具严重的崩刃现象引起了系统铣削力急剧增加,这极大的破坏了铣削系统的稳定性和已加工表面的应力状态,并导致表面粗糙度增大,形成颤振波纹、表面撕裂等加工缺陷。而当铣削速度较高时,由于刀具的损伤较轻,铣削系统相对稳定,已加工表面仍然保持较好的加工质量,特别是铣削速度为600 m/min时,表面粗糙度Sa和Sq的值达到了1.80μm和2.25μm,在刀具磨损后仍然分别保持在2.20μm和3.10μm左右。结论在T2纯铜的铣削加工中,提高铣削速度对延长刀具寿命,改善已加工表面质量有积极作用。

The increase of machining distance is inevitably accompanied by the increase of tool wear,which also leads to the deterioration of the machined surface quality.In order to satisfy the increasing processing needs of T2 pure copper and improve the processing quality of T2 pure copper,the work aims to study the internal relationship between tool wear and machined surface morphology at different milling speeds.The experiment takes milling speed as independent variable.According to the single factor test results,the influence of milling speed on tool wear is studied.On the basis of wear tool milling force model and machined surface stress model,the influence of tool wear on machined surface quality and the reason of surface defects are analyzed from milling force,tool damage form and wear mechanism.The tool wear morphology and the machined surface defects are classified and characterized by optical microscope and scanning electron microscope.When the milling speed is low,there is intense extrusion friction between the rake face and the chip due to the relatively large milling force Fx in the feed direction,resulting in scratches and grooves on the rake face.Lower milling speed means longer machining time at the same milling distance,it results that the cutting tool in processing not only should take more cycle load,but also bear more impact times.It is easy to cause the stress concentration at tool tip,so as to make the cutting edge break and tear.Severe tool wear often results in the change of tool geometry and the further deterioration of tool stress state,which destroys the stability of milling system,leads to flutter ripple on workpiece surface,and greatly increases the roughness of machined surface.Tool wear will change the actual friction form between cutter and workpiece and affect the machining surface stress state,so that the tearing stress on the workpiece surface exceeds the yield strength of the material,and then form the surface tearing.However,when the milling speed is higher,the milling system is relatively stable due to the lighter damage of the tool,and the machined surface still maintains good machining quality.Especially when milling speed is 600 m/min,the surface roughness Sa and Sq reaches 1.80μm and 2.25μm.It remains around 2.20μm and 3.10μm when the tool is worn.In the milling of T2 pure copper,increasing the milling speed has a positive effect on prolonging the tool life and improving the quality of the machined surface.