【作者】 宋文龙；

【导师】 邓建新；

【作者基本信息】 山东大学 ， 机械制造及其自动化， 2010， 博士

【摘要】 本文根据干切削刀具的摩擦磨损特性、微孔表面结构以及固体润滑材料的优异摩擦性能,基于微池润滑的技术思想,结合干切削刀具技术、刀具结构设计、固体润滑技术和摩擦学知识,提出微池自润滑刀具的设计理论和制备方法,研制开发具有减摩润滑作用的新型微池自润滑干切削刀具,并探索其减摩润滑机理。通过对固体润滑技术及切削加工润滑机理的分析,提出了微池自润滑刀具的概念,即：在刀具表面的刀具-切屑、刀具-工件接触部位设计加工一定形状和尺寸的微孔,并在其中填充固体润滑剂,在切削过程中微孔中的固体润滑剂受热膨胀以及切屑的摩擦挤压作用在刀具表面拖覆形成固体润滑膜,使摩擦发生在润滑膜内部,产生“微池润滑”效应,从而实现刀具的自润滑。根据干切削刀具的摩擦磨损特点,提出了微池自润滑刀具的设计思路。建立了微池自润滑自润滑刀具的切削力和切削温度模型,研究了微池自润滑刀具的切削力和切削温度理论。分析表明：切削力和切削温度与刀具前刀面摩擦副平均剪切强度τc和刀屑接触长度lf变化趋势相同。降低刀具前刀面平均剪切强度τc或刀屑接触长度lf,均可有效降低切削过程中的切削力和切削温度。进行了微池自润滑刀具的结构设计。确定了不同切削状态下的微孔分布位置,结合微孔结构参数对微池自润滑刀具应力分布状态的影响及作用规律,得出了最佳的微孔形状及结构尺寸：孔形为圆孔,孔数N为4,孔径为Φ0.15±0.02 mm,孔中心距主、副切削刃的距离L1、L2以及孔间距L3都约为0.3 mm,孔深H为0.30mm,孔偏心距L4取为0.05 mm。通过对微池自润滑刀具的制备方法进行分析,选择微细电火花加工方法进行微池自润滑刀具的微孔加工。微细电火花加工试验表明,在加工电压为125 V、电容为4.45 nF时,能够加工出满足微池自润滑刀具要求的微孔,同时分析了微细电火花加工参数(电压和电容)对微孔加工质量的影响及作用规律。为考察微池自润滑刀具的摩擦磨损特性,对制备的具有相同结构的微池自润滑刀具试样进行了摩擦磨损试验,分析了微孔结构参数、固体润滑剂等因素对微池自润滑刀具试样摩擦磨损特性的影响及作用规律。结果表明：微池自润滑刀具试样MP-MS的摩擦系数和磨损率比YT14普通试样的显著降低,其中摩擦系数降低了55%-65%,磨损率降低了约40%-50%。孔径／孔间距之比为0.4-0.5时微池自润滑刀具试样MP-MS具有最佳的减摩润滑特性。分析了刀具试样以及对磨球的磨损形貌、表面成分,并结合刀具试样的摩擦摩擦特点,认为在相对摩擦过程中,存储于微孔中的固体润滑剂受到相对摩擦和挤压作用而粘着、拖覆在摩擦副表面,并在摩擦副表面形成一层转移膜,使摩擦发生在转移膜之间进行,从而降低了摩擦副之间的摩擦系数,改善了试样的摩擦磨损特性。对制备的不同型号的微池自润滑刀具以及YT14传统刀具进行了切削45号钢的对比试验。试验表明,与传统YT14刀具相比,MPR-4MS刀具和MPR-4MH微池自润滑刀具的切削力、切削温度以及前刀面平均摩擦系数显著降低,MPR-4MS刀具的前刀面耐磨性最好,MPF-4MS刀具的后刀面耐磨性最好。试验同时表明,微孔结构对刀具的切削性能有影响。靠近刀尖及主切削刃的孔对微池自润滑刀具切削性能的影响较大,离刀尖较远的孔对自润滑刀具切削性能影响较小。填充不同固体润滑剂的微池自润滑刀具的切削性能明显不同,且所适用的切削速度范围存在差异：切削速度小于100 m／min时,刀具MPR-4MS的切削性能最好；切削速度高于100 m／min时,MPR-4CF刀具的切削力显著降低；刀具MPR-4C受切削速度的影响最小,显示了较稳定的切削性能。在切削速度高于220m／min时,切屑易堵塞微孔,微池刀具将无法实现自润滑,因此微池自润滑刀具适合的切削速度范围低于200 m／min。分析了微池自润滑刀具的减摩润滑机理,在切削过程中,微池自润滑刀具微孔中的固体润滑剂受热膨胀以及切屑的摩擦挤压作用,拖覆在刀具表面,形成固体润滑膜,固体润滑膜具有较低的剪切强度,能够减小前刀面平均剪切强度τc,从而降低前刀面的平均摩擦系数,降低切削力和切削温度；其次微池自润滑刀具前刀面微孔的存在能够减小刀-屑接触长度lf,同样减小切削力和切削温度。其中前者起主要作用。更多还原

【Abstract】 Micro-pool self-lubricating tools were designed and developed based on micro-pool lubricating idea, excellent tribological properties of solid lubricating materials, the tribological behaviors and wear mechanisms of dry cutting tools. The lubricating mechanism of micro-pool lubricating tools were detailed studied as well as its preparation methods and design theory.The concept and design ideas of the micro-pool self-lubricating tool was proposed based on the analysis of solid lubricanting technology and cutting lubricanting mechanism. Micro-holes were made on the rake face or the flank face of tool inserts. Solid lubricants were embedded into the micro-holes to form micro-pool self-lubricating cutting tool. During cutting processes, the chip slides against the tool rake face at a high speed, and induces high cutting temperature. Under high cutting temperature and chip friction, the solid lubricants may be released from the micro-holes, smeared on the tool face. Then a thin lubricating film may create on the tool face which achieve the micro-pool lubricating and reduce the tool wear. The designed models of micro-pool self-lubricating cutting tool were established under the analysis of tribological behaviors and wear mechanisms of dry cutting tools.The Finite Element Analysis (FEA) modeling for analysis of cutting temperature and cutting forces distribution of micro-pool self-lubricating tool were established and used to analyze the theory of cutting temperature and cutting forces of micro-pool self-lubricating cutting tool. Analysis results indicated that three cutting force components and cutting temperature are both proportional to the average shear strengthτc and the tool-chip contact length If. A reduction of average shear strengthτc or the tool-chip contact length If will both result in the reduced cutting forces and cutting temperature during cutting processes. The micro-holes structure of the micro-pool self-lubricating tools were studied. The effect of micro-holes on stress distribution of the cutting tools were analyzed and the appropriate micro-holes structural parameters were put forward:the micro-holes are circular; the number of micro-holes is 4; the diameter of micro-holes is 0.15±0.02 mm; the distance L1 is about 0.3mm; the distance L2 is about 0.3mm; the distance L36 is about 00.3 mm; the depth H is 0.30 mm; the axis distance L4 is 0.05 mm.Micro-EDM method was choosed to prepare micro-holes of the micro-pool self-lubricating tools after analysis of micro-holes preparing methods. The appropriate process parameters of EDM was determined:the machining voltage is 125 V, the processing capacitance is 4.45 nF. The influence of processing paremeters on processing quality was analyzed.In order to investigate tribological behaviors of the micro-pool self-lubricating tool, friction and wear tests were conducted on the micro-pool self-lubricating tool samples with the same micro-holes structures as the micro-pool self-lubricating tool. The influence of micro-holes structure and the solid lubricants embedded in the micro-holes on the wear behaviors were studied. Results indicated that friction coefficient and wear rate of the micro-pool self-lubricating tools sample MP-MS are both lower than those of the traditinal sample YT14, the friction coefficient can be decreased about 55%-65% and the wear rate can be reduced about 40%-50%. The best antifriction lubricating properties appeared when the ratio of pool depth and pool spacing was 0.4 to 0.5 and the pools were filled with solid lubricant MoS2. The tribological mechanism of micro-pool self-lubricating tool filled with solid lubricant was put forward:the solid lubricant was squeezed out or smeared on the interface during sliding process, a lubricating film is formed to lead to reduce the friction coefficient between the contact interface, and the friction and wear behaviors of micro-pool self-lubricating tool samples were improved.Cutting tests on 45# steel were carried out with cutting tool MPR-4MS, cutting tool MPR-4MH, MPF-4MS, cutting tool MPF-4MH and traditional tool YT14. The results showed that, compared with the traditional cutting tool YT14, cutting with cutting tool MPR-4MS and cutting tool MPR-4MH could result in obviously reduced cutting forces, cutting temperature and average friction coefficient on the rake face. The cutting tool MPR-4MS had the best rake wear resistance and the cutting tool MPF-4MS had the best flank wear resistance.Micro-hole structure of micro-pool self-lubricating tool affects the cutting performance. Based on cutting tests with micro-pool self-lubricating cutting tool MPR-4MS, the micro-holes filled with MoS2 near the tool tip and the main cutting edge have larger effect on cutting performance than other holes for the MPR-4MS tools. The cutting performance of micro-pool self-lubricating cutting tool vary with the different solid lubricant additives, and are affected by cutting speed obviously. when the cutting speed is less than 100 m/min, the cutting performance of the MPR-4MS cutting tool is best; the cutting performance of the MPR-4CF cutting tool significantly slows down when the cutting speed is higher than 100 m/min; the MPR-4C cutting tool has steady cutting performance, which is affected lightly by the cutting speed. Micro-pool self-lubricating cutting tools will not be able to achieve self-lubricating when the cutting speed is higher than 220 m/min, for severe chip adhesives on the micro-holes. Therefore, the micro-pool self-lubricating cutting tools are fit to cutting whthin cutting speed of 200 m/min.The self-lubricating mechanism of micro-pool self-lubricating cutting tool is put forward. on the one hand, during cutting processes, the chip slides against the tool rake face at a high speed, and induces high cutting temperature. Under high cutting temperature and chip friction, the solid lubricants may be released from the micro-holes, smeared on the tool face. Then a thin lubricating film may create on the tool face, which results in reduced average shear stressτc and coefficient of friction on the rake face, increasd shear angle, reduced cutting forces, the cutting heat and the cutting temperature; on the other hand, the reduced contact length lf at the tool-chip interface results in a reduction in cutting forces and cutting temperature, which is contributed to the decrease of tool wear. The former factor is primary.更多还原