304不锈钢电火花线切割加工表面性能研究

Research on 304 Stainless Steel Surface Properties by Wire Electrical Discharge Machining

目的研究电火花线切割工艺对金属材料加工表面质量的影响规律,分析加工表面的机械性能。方法利用电火花线切割加工技术,对304不锈钢工件进行表面切割试验,应用马尔轮廓测量仪、扫描电镜、超景深电子显微镜及纳米压痕仪观察电火花加工表面的粗糙度变化规律和表面微形貌特征,获取横截面纳米硬度变化曲线。设计正交试验,获得最优加工参数。结果脉冲宽度和峰值电流对奥氏体不锈钢加工表面形貌的形成机制有显著影响,加工表面粗糙度受电参数的影响较大,加工表面的表层及次表层组织主要由塑性变形层与回火多相组织层共同构成,厚度与纳米硬度的变化受电参数的影响较大。结论电参数对表面质量的影响程度顺序为脉冲宽度、峰值电流、放电间隔,为得到较优加工表面层,应优先选择脉冲宽度为16μs,放电间隔为96μs,峰值电流为1.5 A的工艺参数组合。单个脉冲能量对加工层的厚度以及表层的纳米硬度呈现出近似线性规律。

Objective To investigate the influences of W-EDM process on the surface quality of materials,analyze the mechani-cal properties of the machined surface. Methods The wire electrical discharge machining was used to conduct the surface cutting test of 304 stainless steel. The profilometer, scanning electron microscope （ SEM） , electron microscope and nanoindentation were used to examine the variation pattern of surface roughness and surface micro-morphology and obtain the micro and nano-hardness curve of electric discharge machining （ EDM） . The orthogonal experiment was designed to obtain the optimal parameters. Results The machining pulse width length and the peak current of austenitic stainless steel processing had a significant effect on the forma-tion mechanism of surface morphology. The surface roughness was greatly influenced by electrical parameters. The surface and the subsurface tissues were mainly composed of the layer of plastic deformation and the layers of tempered multiphase. Changes were great in the thickness and the nano-hardness due to the influence of the electrical parameters. Conclusion Electrical parameters bytheir effects on the surface quality in order were pulse width, peak current, and discharge interval. In order to obtain the optimum machining surface layer, priority should be given to select pulse width 16 μs, discharge interval 96 μs, peak current of 1. 5 A as the processing parameters. Single pulse energy exhibited a nearly linear association with thickness and nano-hardness of the pro-cessed layer.