Experimental evaluation on the effect of electrostatic minimum quantity lubrication (EMQL) in end milling of stainless steels

The machining of stainless steels is very challenging owing to their high toughness and low thermal conductivity, causing high cutting temperatures and rapid tool wear. Conventionally, metalworking fluids in flood form are used during the process to improve surface quality and tool life; however, their use raises issues including environmental pollution and economic concerns. Therefore, an electrostatic minimal quantity lubrication (EMQL) technology was developed to reduce the consumption of metalworking fluids. EMQL is a near-dry machining technology utilizing the synergetic effects between electrostatic spraying and minimum quantity lubrication (MQL), wherein the lubricant is to apply in a form of fine, uniform and highly penetrable and wettable mist droplets directly to the cutting zone. This study investigates the effect of EMQL in end milling of AISI 304 stainless steel in comparison with dry, wet and MQL machining. The results suggest that EMQL reduces tool wear and cutting force, prolongs tool life considerably and enhances surface finish compared with conventional wet and MQL machining. scanning electron microscopy and Energy-dispersive X-ray spectroscopy analyses show that EMQL considerably reduces adhesive and abrasive wear on the flank face because of the lower friction and heat generation resulting from more efficient entry of the lubricant into the cutting interfaces.     

Cryogenic minimum quantity lubrication machining: from mechanism to application

Cutting fluid plays a cooling–lubrication role in the cutting of metal materials. However, the substantial usage of cutting fluid in traditional flood machining seriously pollutes the environment and threatens the health of workers. Environmental machining technologies, such as dry cutting, minimum quantity lubrication (MQL), and cryogenic cooling technology, have been used as substitute for flood machining. However, the insufficient cooling capacity of MQL with normal-temperature compressed gas and the lack of lubricating performance of cryogenic cooling technology limit their industrial application. The technical bottleneck of mechanical–thermal damage of difficult-to-cut materials in aerospace and other fields can be solved by combining cryogenic medium and MQL. The latest progress of cryogenic minimum quantity lubrication (CMQL) technology is reviewed in this paper, and the key scientific issues in the research achievements of CMQL are clarified. First, the application forms and process characteristics of CMQL devices in turning, milling, and grinding are systematically summarized from traditional settings to innovative design. Second, the cooling–lubrication mechanism of CMQL and its influence mechanism on material hardness, cutting force, tool wear, and workpiece surface quality in cutting are extensively revealed. The effects of CMQL are systematically analyzed based on its mechanism and application form. Results show that the application effect of CMQL is better than that of cryogenic technology or MQL alone. Finally, the prospect, which provides basis and support for engineering application and development of CMQL technology, is introduced considering the limitations of CMQL.     

Influence of minimum quantity lubrication parameters on tool wear and surface roughness in milling of forged steel

The minimum quantity of lubrication (MQL) technique is becoming increasingly more popular due to the safety of environment.Moreover,MQL technique not only leads to economical benefits by way of saving ...     

Tribological mechanism of carbon group nanofluids on grinding interface under minimum quantity lubrication based on molecular dynamic simulation

Carbon group nanofluids can further improve the friction-reducing and anti-wear properties of minimum quantity lubrication (MQL). However, the formation mechanism of lubrication films generated by carbon group nanofluids on MQL grinding interfaces is not fully revealed due to lack of sufficient evidence. Here, molecular dynamic simulations for the abrasive grain/workpiece interface were conducted under nanofluid MQL, MQL, and dry grinding conditions. Three kinds of carbon group nanoparticles, i.e., nanodiamond (ND), carbon nanotube (CNT), and graphene nanosheet (GN), were taken as representative specimens. The [BMIM]BF₄ ionic liquid was used as base fluid. The materials used as workpiece and abrasive grain were the single-crystal Ni–Fe–Cr series of Ni-based alloy and single-crystal cubic boron nitride (CBN), respectively. Tangential grinding force was used to evaluate the lubrication performance under the grinding conditions. The abrasive grain/workpiece contact states under the different grinding conditions were compared to reveal the formation mechanism of the lubrication film. Investigations showed the formation of a boundary lubrication film on the abrasive grain/workpiece interface under the MQL condition, with the ionic liquid molecules absorbing in the groove-like fractures on the grain wear’s flat face. The boundary lubrication film underwent a friction-reducing effect by reducing the abrasive grain/workpiece contact area. Under the nanofluid MQL condition, the carbon group nanoparticles further enhanced the tribological performance of the MQL technique that had benefited from their corresponding tribological behaviors on the abrasive grain/workpiece interface. The behaviors involved the rolling effect of ND, the rolling and sliding effects of CNT, and the interlayer shear effect of GN. Compared with the findings under the MQL condition, the tangential grinding forces could be further reduced by 8.5%, 12.0%, and 14.1% under the diamond, CNT, and graphene nanofluid MQL conditions, respectively.     

Effect of magneto rheological minimum quantity lubrication on machinability,wettability and tribological behavior in turning of Monel K500 alloy

Abstract

The proposed work deals with the investigation of magnetorheological based minimum quantity lubrication of graphene oxide (GO) based jojoba oil as bio-lubricant on machinability and tool wear mechanism of turning Monel K500 alloy. Experiments were carried out for dry, flooded, minimum quantity lubrication (MQL) and magnetorheological (MR–MQL) conditions using medium duty lathe. The process parameters include the cutting speed 95, 110, 125?m/min, feed rate 0.050, 0.075, 0.1?mm/rev and depth of cut 0.25, 0.50, 0.75?mm for the output responses such as surface roughness, cutting temperature and tool flank wear. The results indicated that GO-based bio-lubricant MR–MQL reduced coefficient of friction (COF) of 0.051 and wetting angle of 6°, as well as improved machining performance such as cutting temperature of 145?°C, the surface roughness of 0.614?µm, flank wear of 0.18?mm with enhanced lubrication regime under extreme wear conditions.     

静电喷雾润滑液滴的粒径分布特性研究

为掌握静电喷雾润滑液滴的粒径分布特性,将图像识别检测技术应用到荷电润滑液滴的粒径测量中.开展了采集图像中液滴区域的特征抽取和识别分析,建立了液滴的平面二维直径和空间三维直径的转换关系,提出了一种实用的气雾液滴粒径分布特性的检测方法.在建立液滴采集装置的基础上,进行了气雾不同截面液滴的采集和识别试验.实验结果表明,随着静电电压升高,喷雾索特平均直径减小,雾滴颗粒趋于均匀,雾化质量明显改善;在距喷嘴60 mm～140 mm的3个截面上,随着距离的增加,雾滴索特平均直径增大,雾滴趋于发散.     

高合金不锈钢的干车削和近干车削研究

高合金不锈钢具有强度高、韧性好、耐腐蚀等优良性能而得到日益广泛的应用,但是其难加工性同时也对切削技术提出了更高的要求.干切削因具有对环境和人体无害、经济性好等优点成为金属加工技术的主要发展方向之一.文中对高合金不锈钢Y12Cr17和16Cr17Ni3的干车削和近干车削中,切削参数和切削材料对刀具磨损和工件表面质量的影响进行了深入研究.结果表明,通过选择适当的切削参数、刀具材料以及刀具涂层,可以很好地实现高合金不锈钢的干车削加工,并能获得比传统乳化剂加工更小的磨损值和更好的工件表面质量.     

Investigation of roughness,topography, microhardness,white layer and surface chemical composition in high speed milling of Ti-6Al-4V using minimum quantity lubrication

Abstract

In this research, the effects of high speed milling on the main surface integrity characteristics, including surface roughness and topography, microhardness, white layer thickness, and surface chemical composition of Ti-6Al-4V were empirically studied. Totally, 18 experiments were carried out using a full factorial design of experiments method in the presence of minimum quantity lubricant. The results showed that by using high speed milling, it is possible to reach the surfaces with a higher quality and surface roughness of approximately 0.2?μm. Also, it was discovered that the microhardness variation with cutting speed has a dual nature. The maximum microhardness was obtained at the cutting speed of 375?m/min and the feed rate of 0.08?mm/tooth, which showed a 57% increase compared with the bulk material. In addition, by using the cutting speed of 450?m/min, the depth of heat-affected layer and work hardening effects declined up to 75% in comparison with the cutting speed of 300?m/min.     

42CrMo合金结构钢的干切削和近干切削研究

合金结构钢以其生产规模大、易于加工、性能多样、价格低廉、使用方便和便于回收等特征成为重要的钢铁材料。干切削和微量润滑加工技术是目前金属加工技术的主要发展方向之一,也是实现绿色制造的关键技术。文中对合金结构钢42CrMo在干切削和近干切削加工条件下,切削参数和切削材料对刀具磨损和工件表面质量的影响进行了比较深入的研究。结果表明,通过选择适当的切削参数,刀具材料和刀具涂层,可以很好地实现这种材料的干切削加工,甚至可以获得比传统乳化剂加工更低的刀具磨损和更好的表面质量。     

Specific energy and surface roughness of minimum quantity lubrication grinding Ni-based alloy with mixed vegetable oil-based nanofluids

Vegetable oil is a low toxic, excellent biodegradable and renewable energy source used as an ideal lubricating base oil in machining. Castor oil exhibits good lubrication performance but poor mobility, which limits its application especially in precision grinding. The main objective of the work presented to obtain optimal mixed vegetable based-oil and optimal nanoparticles adding concentration in grinding Ni-based alloy with minimum quantity lubrication. An experimental investigation is carried out first to study the different vegetable oils with excellent mobility mixed with castor oil. The lubrication property of the oil was evaluated in terms of grinding force, force ratio, specific grinding energy, and surface roughness. Based on the test conditions, it is found that soybean/castor mixed oil obtained the optimal results (μ= 0.379, U = 83.27 J/mm³ and Ra = 0.325 μm) and lubricating effect compared with castor oil and other mixed base oils. To further explore the lubricating capability of soybean/castor mixed oil, MoS₂ nanoparticles which have excellent lubricating property were added into the soybean/castor mixed oil to prepare different concentrations nanofluids. From the present study, it can be concluded that 8% mass fraction of the oil mixture should be added to obtain the optimal machining results, with the lowest force ratio (0.329), specific energy (58.60 J/mm³), and average grinding temperature (182.6 °C). Meanwhile, better surface microtopography of ground parts and grinding debris morphologies were also observed for the machining conditions.     

球墨铸铁纳米粒子射流微量润滑磨削性能的实验研究

主要对纳米粒子射流微量润滑磨削性能进行实验评价.采用K-P36数控平面磨床,选取干磨削、浇注式磨削、微量润滑磨削和纳米粒子射流微量润滑磨削4种工况条件,分别从磨削力、磨削G比率、磨削温度和表面粗糙度方面进行磨削性能评价,结果表明:纳米粒子射流微量润滑磨削改善了换热能力,与干磨削相比降低了将近150℃,干磨削得到的工件表面粗糙度Ra值为1.2μm,纳米粒子射流微量润滑磨削Ra值为0.58 μm,工件表面质量显著提高;在纳米粒子的润滑作用下,得到的磨削力较稳定,且比干磨削和微量润滑磨削得到的磨削力减小15％以上;纳米粒子射流微量润滑磨削G比率在4种工况中最高,值为33,干磨削仅为12,比其他工况增大约一倍,砂轮的磨损明显减小,延长砂轮使用寿命.     

Hard turning using HiPIMS-coated carbide tools: Wear behavior under dry and minimum quantity lubrication (MQL)

In the present work, experimental investigations carried out to assess the applicability of HiPIMS (High Power Impulse Magnetron Sputtering)-coated carbide tools to hard turning (55 HRC) and to address the widely debated topic about the use of coolants in hard turning are presented. Tool wear progressions and hence, tool life, different tool wear forms and wear mechanisms observed for tools coated with HiPIMS coating technique, namely, nanocomposite AlTiN, nanocomposite multi-layer TiAlN/TiSiN and nanocrystalline AlTiCrN are presented along with the images captured by digital and electron microscope. Characterization results of all the coated tools in terms of their average coating thickness (measured using Calotest and Fractographs), adhesion strength of the coating(s) (determined using Scratch test), composition and microhardness (using EDAX and Vickers microhardness test, respectively) are presented. Experimental observations indicate higher tool life with nanocrystalline AlTiCrN coated carbide tools which shows encouraging potential of these tools to hard turning. Improvement in tool life of almost 20–25% has been observed under minimum quantity lubrication (MQL) due to better cooling and lubricating effects. However, this effect was more prominent at higher cutting speed of 150 m/min.     

Effects and mechanisms in minimal quantity lubrication machining of an aluminum alloy

Effects and mechanisms in minimal quantity lubrication are investigated by use of an intermittent turning process. Especially a difference between minimal quantity lubrication (MQL) and MQL with water is inspected in detail to elucidate boundary film behaviour on the rake face. In order to obtain a good cutting performance by MQL it is considered that two things are needed: (1) an appropriate lubricant, such as a synthetic ester, to form a strong boundary film and (2) a chilling effect to sustain strength of the boundary film.     

静电雾化微量润滑研究进展与应用

微量润滑作为替代浇注式供液冷却的可行性方案之一,得到了数十年的发展。然而,气动雾化微量润滑雾滴的表面能逐渐降低;射流的穿透力、吸附力和浸润性能不足,雾滴的漂移和飞溅丧失严重,加大了对环境的污染。静电雾化微量润滑是解决工业生产应用面临技术瓶颈和环保压力的有效方式。首先,系统综述了静电雾化微量润滑关键装置、赋能原理与绿色雾化介质(纳米生物润滑剂)。其次,揭示了微液滴的雾化性能对切削区浸润性能的影响机制,并从荷电液滴静力学的角度阐述了静电雾化微量润滑优异的雾化性能,通过表征雾化介质的荷电性能分析了不同参数对雾化能力的影响机制。进一步地,基于纳米生物润滑剂的脂肪酸分子结构、黏度等理化性质,以及荷电液滴表面状态、空间多能场等,揭示了静电雾化微量润滑改善液滴浸润、渗透以及成膜性能的作用机制,并综述了其在车削、铣削、磨削等工况下对降低刀具磨损、提高加工表面质量的优异性能。在此基础上分析得到：静电雾化优异的雾化特性以及纳米生物润滑剂独特的润滑传热机制,不仅降低了加工环境油雾浓度,还提升了微量润滑的加工性能,具体表现在,与传统微量润滑相比PM2.5/PM10降低约6.2%～68.3%,刀具寿命增加约48...     

微量润滑切削加工性能影响因素的研究

介绍了微量润滑（MQL）切削加工技术相对于传统湿式和干式切削的应用优势及应用现状,重点分析了MQL油雾供给与混合系统、润滑油、压缩空气、工件材料、刀具以及切削参数等因素对MQL切削加工性能的影响规律,发现在加工条件确定的情况下,润滑油用量、压缩空气压力和切削参数之间存在最优组合。因此,为了充分发挥MQL切削加工技术的应用优势,必须对MQL工艺系统进行全面而精确的优化。     

Friction and wear properties of bronze–graphite composite under water lubrication

Bronze–graphite composite was prepared using powder metallurgy. The friction and wear behaviors of the resulting composites in dry- and water-lubricated sliding against a stainless steel were comparatively investigated on an MM-200 friction and wear tester in a ring-on-block contact configuration. The wear mechanisms of the bronze–graphite composite were discussed based on examination of the worn surface morphologies of both the composite block and the stainless steel ring by means of scanning electron microscopy equipped with an energy dispersion spectrometry and on determination of some typical elements on the worn surfaces by means of X-ray photoelectron spectroscopy. It was found that the friction coefficient was higher under water lubrication than that under dry sliding and it showed margined change with increasing load under the both sliding conditions. A considerably decreased wear rate of the bronze–graphite composite was registered under water-lubricated sliding than under dry sliding, though it rose significantly at a relatively higher load. This was attributed to the hindered transfer of the composite onto the counterpart steel surface under water-lubricated sliding and the cooling effect of the water as a lubricant, while its stronger transfer onto the steel surface accounted for its higher wear rate under dry sliding. Thus, the bronze–graphite composite with much better wear-resistance under water-lubricated sliding than under dry sliding against the stainless steel could be a potential candidate as the tribo-material in aqueous environment.     

石墨的存在形态对铸铁性能的影响

介绍铸铁的发展及应用。主要对石墨的存在形态（形状、数量、大小及分布）及其对铸铁性能的影响进行了阐述。     

The effect of minimum quantity lubrication in the intermittent turning of magnesium based on vibration signals

The present work shows an experimental investigation on intermittent turning based on vibration signals. The dependence of vibrations on the feed rate, minimum quantity lubrication (MQL) flow rate and the type of the interruption of the workpiece is evaluated. The results indicate that a part of the vibrations depends on the flow rate of the MQL system and its interaction with the feed rate, finding no dependency on the type of interruption. The influence of the MQL system is greater when machining at the lower feed rate. In addition, a strong relation between surface roughness and vibrations is identified. However, this relation is quite different depending on the environment used. In general, under dry conditions, the higher the vibrations the higher the surface roughness, while the opposite occurs when the MQL system is used.     

织构化刀具切削性能测试及切削温度仿真分析

研究织构化硬质合金刀具对切削Ti6Al4V钛合金性能的影响。在干切削和低温微量润滑(CMQL)条件下,通过开展无织构和织构化刀具切削试验,分析不同刀具在不同润滑条件下切削力和摩擦因数变化规律。结果表明:微沟槽刀具在CMQL条件下的切削性能最好,在干切削条件下的切削性能最差,表明微沟槽在CMQL条件下能有效改善刀具的摩擦学性能,而在干切削条件下反而增大了刀具的摩擦磨损。通过仿真分析织构化刀具高速干切削条件下的切削温度,结果表明:织构化刀具干切削条件下的切削温度高于无织构刀具,这是因为表面织构增大了刀具表面的粗糙度,加剧了刀-屑界面摩擦。     

面向绿色制造的干式齿轮加工过程碳排放分析

为了研究干式切削齿轮加工过程碳排放特性,对齿轮加工过程的物料、能源消耗、废物处理及碳排放特性进行了分析,提出了齿轮加工过程碳排放边界条件,建立了齿轮加工过程碳排放计算模型;根据某制造企业提供的数据,将同批次齿轮的绿色干式切削和湿式切削加工过程的碳排放量进行计算与对比分析,结果显示,与湿式切削相比,干式切削齿轮加工过程碳排放总量约少55.69%,废弃物处理碳排放量少15.57%,表明面向绿色制造的干式齿轮加工的能源消耗、成本费用较低且环保,高速干式齿轮加工技术将成为未来齿轮制造业发展的主要趋势。