682 Manufacturing Engineering and Automation I Experiment Equipments and Materials. As shown in Fig.1, cutting experiments were carriedout using a center lathe CA6140, powered by a 7.5kw electric motor giving a speed range of10~1400 rev/min and a feed range of 0.014~3.16 mm/rev. The cutting tools applied were YG6(WC +6%Co, K10 in ISO) uncoated tools and new tool was used for each experiment. A number ofangles for tool geometry were γo=14º, αo=αo=6º, κr=75º, κr=15º, λs=-6º. The workpiece used wasφ100×500 titanium alloy Ti-6Al-4V (TC4) as given in Table 1. The cutting experiments of YT15cutting C45 steel were employed as thecomparison of machinability. Waterline Workpiece Cutting forces were obtained by 9257A Pipeline TankKistler piezocrystal force sensor and 5007 chargeamplifier. Cutting temperature was measured bythermoelectric method with X-Y functionrecorder. Chip thickness was measured by usinga tool microscope. The machined surface Indicator lights Buttonsroughness was taken by a TR200 roughness Pressure gauge PID controllertester made by TIME Company, and the error is0.001µm. Water steam generator Cutting Experiments. The cutting forces Kistler force sensorand temperature, deformation coefficient, Fig. 1 Water vapor generator and experimental systemmachined surface finish and chip appearanceinvestigated. The used cutting speed was 100m/min and the feed was 0.15mm/rev with the applieddepths of cutting were 1, 1.5, 2, 2.5 and 3mm; and the depth of cutting was 2mm with the feed were0.1, 0.15, 0.2 and 0.3 mm/rev. Cooling and Lubricating Conditions. All thecutting experiments were completed at the Table1. Workpiece materials and charactersconditions of dry cutting, water-based emulsion Materials Ti-6Al-4Vand water vapor. The cooling distance was 20mm Chemical Al V O Fe C Nfor the cutting fluid and water vapor. For the composition 6.1 4.1 0.15 0.06 0.01 0.01water-based emulsion, the concentration was 5%, Mechanical σb [MPa] δ5 [%] ψ [%] characters 980 14 40the temperature was 19°C, the flux was 1L/min,the pressure was 0.12MPa and the diameter of pipe was 5mm,. For the water team, the diameter ofnozzle was 2mm, the temperature was 125°C, the flux was 45L/min, and the pressure was 0.25MPa.Results and DiscussionCutting Forces. The main cutting forces of dry and wet cutting and water vapor application wereillustrated in Fig.2. and Fig.3. The results of radial cutting forces were presented in Fig.4. and Fig.5.Among the machining characters of titanium alloys, a special one is that the main cutting force islower but the radial cutting force is higher than those in cutting of C45 steel. 1200 1400 C45 Dry C45 Dry 1000 Dry 1200 Dry Wet 1000 Wet 800 WV WV Fc (N) 800 Fc (N) 600 600 400 400 vc =100m/min 200 f =0.15mm/r 200 vc =100m/min ap=2mm 0 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0.0 0.1 0.2 0.3 ap (mm) f (mm/r) Fig. 2 The Fc-ap curve in cutting experiments Fig. 3 The Fc- f curve in cutting experiments
Advanced Materials Research Vols. 139-141 683 Compared with dry and wet cutting, the main cutting force reduced about 30% and 15%, and theradial cutting forces reduced about 35% and 20%, as water vapor cooling and lubricating. All theemulsion and water vapor present the action of cooling and lubricating in cutting of Ti-6Al-4V. In theexperiments, water vapor produced the lowest cutting force. There are several reasons for thefavorable cooling and lubricating performance of water vapor . The molecule or molecule group inwater vapor has a smaller radius than that in cutting fluids. And the velocity of water vapor jet flow ismuch higher than that of cutting fluids. As a result, water vapor penetrates the tool-chip interfaceeasily and rapidly. 500 400 C45 Dry C45 Dry 350 Dry Dry 400 Wet Wet 300 WV Fp (N) WV 300 250 Fp (N) 200 200 150 100 100 vc =100m/min vc =100m/min ap=2mm 50 f =0.15mm/r 0 0 0.0 0.1 0.2 0.3 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 f (mm/r) ap (mm) Fig. 4 The Fp -ap curve in cutting experiments Fig. 5 The Fp - f curve in cutting experiments Cutting Temperature. The experiment results of cutting temperatures were shown in Fig.6. Thecutting temperature of titanium alloys is much higherthan that of C45 steel, which is another machining 900character of titanium alloys. Water vapor application 800decreased the cutting temperature about 15% and 10%, 700compared to dry and wet cutting. Water vapor gives a 600 θ (°C)better cooling action than the emulsion. In cutting, the 500adhesive of titanium alloy chip on the tool face leads to 400 C45 Dryan acutely friction and generates a great lot of heat. The 300 Dry 200 Wet ap=2mmcutting heat centralizes in a small region because of the WV f =0.15mm/r 100short tool–chip contact length . After water vapor 0enters into the tool-chip interface, lubricating film 120 130 140 150 160 170 180 190forms immediately under the adsorption function. The vc(m/min) Fig. 6 The θ-υc curve in cutting experimentslubricating action of water vapor reduced the tool-chipfriction and the heat generation. In addition, water vapor has the capability of decalescence and heattransformation, though the water vapor temperature is up to 100°C. Contrarily, emulsion is not easilyto penetrate the tool-chip interface and their cooling action only occurs at the outside of cutting zone. Consequently, the water vapor cooling action is better than the emulsion in cutting of Ti-6Al-4V. Cutting Deformation Coefficient. The deformation coefficient Λh can be calculated by Λh=hch/hD,where the average chip thickness hch was measured by using the tool microscope, and the uncut chipthickness hD =f·sinκr. In cutting, the deformation coefficients of titanium alloy are usually close to 1and less than that of C45 steel. As shown in Fig.7, similarly, Λh decreased with rising feed under allthe lubricating conditions, and it is noted that the coolant and lubricant produced a tiny impact ondeformation coefficient. Accordingly, the force and heat from chip deformation were hardlyinfluenced. With the water vapor using, the decreases of cutting force and temperature resulted fromthe decreases of friction force and heat generation on the tool-chip interface at s large extent. And thisalso helps to slower the tool wear and prolong the tool life. Machined Surface Finish. The surface finish roughness values were presented in Fig.8. As thefeed increasing, the value Ra increased. The application of water vapor gave the lowest surface finishroughness value among the three cooling and lubricating conditions. These shown that the coolantsand lubricants can act not only on the rake face but also on the flank one. The high cutting temperature
684 Manufacturing Engineering and Automation Ileads to rapid wearing of cutting tool and then impact to surface finish. The action of cooling andlubricating reduce the cutting temperature and lower the tool wear speed. As a result, machinedsurface finish can be easier controlled in the ideal range. 2.4 2.1 6 Dry 1.8 5 Wet WV 1.5 4 Ra (µm) Λh 1.2 3 0.9 C45 Dry Dry 2 0.6 Wet vc =100m/min vc=100m/min 0.3 WV ap=2mm 1 ap=2mm 0.0 0 0.0 0.1 0.2 0.3 0.0 0.1 0.2 0.3 f (mm/r) f (mm/r) Fig.7 The Λh – f curve in cutting experiments Fig. 8 The Ra-f curve in cutting experimentsConclusionsTi-6Al-4V is one of the difficult-to-cut materials, and the cutting experiments as water vapor coolingand lubricating were carried out. Compared to dry cutting and emulsion applied, when water vaporused, the main cutting force is lower about 30%-35% and 15%-20%, the cutting temperature reducesbout 15%and 10%, while the deformation coefficient does not variety obviously. Water vaporenhances the machined surface appearance to some extent. Water vapor application improvesTi-6Al-4V machinability compared to dry and wet cutting. The excellent lubricating action of watervapor in cutting could be summarized that water molecule has polarity, small diameter and high speed,can be faster and easier to proceed adsorption in the cutting zone. The machining process of titaniumalloy receives available controlling. Otherwise, Water vapor has the advantages of cheap, clean forenvironment, harmless for health and unneeded disposal or recycling, which are the potential forgreen machining. Taking cooling and lubricating performance into account, water vapor may be abetter choice for green machining to titanium alloy.AcknowledgementsThis research reported in the paper is financially supported by National Natural Science Foundation ofChina (NSFC) (50675053), Research and Development Plan of the Education Apartment of LiaoningProvince (05L301). These supports are greatly acknowledged.References R.D. Han, Y. Zhang, Y.Wang: Key Engineering Materials, Vol.375-376 (2008), pp.172- 176. C.H. Zhang: Journal of Shenyang University of Technology, Vol.30 (2008) No.5, pp.525-529. S. Zhang:Journal of Shenyang University of Technology, Vol.30 (2008) No.4, pp.424-428. Y. Zhang, R.D. Han, T.L. Sun:Advanced Materials Research Vols. 97-101(2010), pp.2365-2368. C.H. Zhang: Journal of Shenyang University of Technology, Vol.30 (2008) No.6, pp.653-657. Y. Su, N. He, L. Li: China Mechanical Engineering (in Chinese), Vol.17(2006), pp.1183- 1187. P. Zheng: Journal of Shenyang University of Technology, Vol.31 (2009) No.5, pp.548-552 J.A. Williams, D. Tabor: Wear, (1977) No.3, pp.275-292. V. A Godlevski, A.V Volkov: Lubrication Science, (1997) No.9, pp.127-140. M. Cotterell, G. Byrne:CIRP Annals - Manufacturing Technology, v57(2008), pp.93-96.
Manufacturing Engineering and Automation I10.4028/www.scientific.net/AMR.139-141Machining Process of Titanium Alloy Based on Green Cooling and LubricatingTechnology10.4028/www.scientific.net/AMR.139-141.681DOI References R.D. Han, Y. Zhang, Y.Wang: Key Engineering Materials, Vol.375-376 (2008), pp.172-176.doi:10.4028/www.scientific.net/KEM.375-376.172 J.A. Williams, D. Tabor: Wear, (1977) No.3, pp.275-292.doi:10.1016/0043-1648(77)90125-9 V. A Godlevski, A.V Volkov: Lubrication Science, (1997) No.9, pp.127-140.doi:10.1002/ls.3010090203