静压力对超声滚压表层特性的影响

Effect of Static Pressure on Surface Characteristics of Ultrasonic Rolling

目的研究不同静压力对试样表面形貌、粗糙度、晶粒细化程度、随表层深度变化的显微硬度和残余应力的影响。方法运用超声滚压加工技术,采用HEU-Ⅱ系列的超声滚压设备和卧式车床对AISI304不锈钢进行处理,改变静压力,其余参数不变。利用综合扫描电子显微镜、触针式粗糙度仪、金相显微镜、显微硬度仪和X射线衍射分析仪等进行检测分析。结果静压力在300~800 N时能获取较好表面质量,超过800 N后会对表面产生损伤,出现细纹。通过XRD分析,静压力越大,晶粒细化程度越高,X衍射峰的宽化程度也越小。试样表层硬化层深度和硬度随静压力增大而增加,600 N时的硬化层比200 N时增加150μm,硬度增加35%,残余应力在表面表现为压应力,随着静压力增加而增加。当静压力增大到600 N时,最大残余应力由表面转移至材料内部。结论静压力参数在一定的范围内会产生很好的加工效果,超过一定的范围则会带来不良影响,这为运用超声滚压技术加工精密工件奠定了理论基础。

The work aims to study the effects of different static pressures on surface topography, roughness, grain refinement degree, micro-hardness and residual stress variation with the surface depth. With static pressure changed and other parameters unchanged, AISI304 stainless steel was treated with HEU-II series ultrasonic rolling equipment and horizontal lathe by taking advantage of ultrasonic rolling processing technology. The above-mentioned purpose was investigated with a comprehensive scanning electron microscopy, contact pin type roughness meter, metallographic microscope, micro-hardness tester and X ray diffraction analyzer. Better surface quality could be obtained at the static pressure ranging from 300 N to 800 N, but damage and microgroove were produced at the static pressure of over 800 N. According to XRD analysis, the higher the static pressure was, the higher the grain refinement degree was, the narrower the X diffraction peak was. Depth and hardness of the surface hardening layer increased with the increase of static pressure, the hardening layer at 600 N increased by 150 μm and hardness by 35% compared with that at 200 N. The surface residual stress was presented as compressive stress, and increased as the static pressure increased. When the static pressure increased to 600 N, the maximum residual stress transferred from the surface to interior of the materials. The static pressure parameters will produce excellent processing effects in a certain range and bad influence beyond a certain range, which lays theoretical basis for processing precision workpieces by taking advantage of ultrasonic rolling technology.