Dautzenberg, JH

Dijck, JAB  van

Wolf, ACH  van der

Dautzenberg, J.H.

Dijck, van, J.A.B.

van der Wolf, A.C.H.

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The anomalous tool wear behaviour in cutting steel SAE-1045

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 The anomalous tool wear behaviour in cutting steel SAE-1045Citation for published version (APA):Dautzenberg, J. H., Dijck, van, J. A. B., & van der Wolf, A. C. H. (1981). The anomalous tool wear behaviour incutting steel SAE-1045. (TH Eindhoven. Afd. Werktuigbouwkunde, Laboratorium voor mechanische technologieen werkplaatstechniek : WT rapporten; Vol. WT0497). Technische Hogeschool Eindhoven.Document status and date:Published: 01/01/1981Document Version:Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the version of the article upon submission and before peer-review. There can beimportant differences between the submitted version and the official published version of record. Peopleinterested in the research are advised to contact the author for the final version of the publication, or visit theDOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and pagenumbers.Link to publicationGeneral rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            • Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            • You may not further distribute the material or use it for any profit-making activity or commercial gain            • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, pleasefollow below link for the End User Agreement:www.tue.nl/taverneTake down policyIf you believe that this document breaches copyright please contact us at:openaccess@tue.nlproviding details and we will investigate your claim.Download date: 08. Jul. 2024THE ANOMALOUS TOOL WEAR BEHAVIOUR IN CUTTING STEEL SAE-1045 by: J.H. Dautzenberg, J.A.B. van Dijck and A.C.H. van der Wolf. "Eindhoven University Press" WPT-report nr. 0497. Note for STC "c" subgroup Fundamentals Paris, January 1981. -1-THE ANOMALOUS TOOL WEAR BEHAVIOUR IN CUTTING STEEL SAE-1045. by: J.H. Dautzenberg, J.A.B. van Dijck and A.C.H. van der Wolf. Division of Production Technology, Eindhoven University of Technology, Netherlands. 1. Introduction. When cutting steel which contains iron carbides it is observed [lJ that the wear of the tool as a function of the cutting speed for a constant cutting path has a minimum (Figure I). In this figure the wear is related to flank wear, but it holds also for other kinds of wear. Starting from the idea that friction in the case of large displacements parallel to the contact surfaces is caused by plastic deformation, this minimum has to be explained. In the next section it is made , that the minimum can be caused by the solution of iron carbides in the aus.tenite of the workpiece material in the contact zone of workpiece and tool. The contact zone of the workpiece material is made visible in the electron microscope by making thin foils. For normal cutting conditions the workpiece material in the contact zone oxidizes immediately. i'.60 I I I I iJ.SiJ I I 'I / II.J(J tl.70 ~ , .... ~ t" ... ~ .... ... I) I "" / ~ ./ U/J II I t .. . (! If) .i1 .10 'III S{I 6,1 711 . E/{J gil lOU J f(I 14" lJII 1~11 - cutting speed em/min] Figure 1. Flank wear of the cutting tool P30 for a constant cutting path of steel as a function of the cutting speed according to Vieregge [1J. -2-This oxide layer prevents to make good foils for transmission in the electron microscope. For this reason we made an experimental set-up to prevent this oxidation process (section 3). With this set-up we did our cutting tests for a cutting speed corresponding to the minimum of tool wear. From the chip contact zone with the tool we made several electronmicrographs (section 4). These electronmicrographs neither contradict nor confirm our idea. They show only that the structure in the contact zone is very different from the bulk of the chip. Also it was clear that we need a better thinning technique for making thin foils of this two phase material. Having a better thinning technique we hope to confirm our idea in the near future. -3-2 Tool We assume that continuous wear of the tool in cutting is caused by plastic deformation of the tool material. That is in contrary with discontinuous wear (fracture of the tool). Plastic deformation of the tool material is only possible if the flow stress of the tool material is equal or lower than the flow stress of the workpiece material. For normal conditions one would expect that it is impossible. But regarding the contact surface of workpiece and tool material, it is obvious that there is diffusion of one or more components of the workpiece into the tool material or vice versa. This diffusion process is not caused by lowering the enthalpy but by an increase of the entropy. If we regard a carbide tool, it means that one of the components of the carbides or the bounder diffuse into the workpiece material or .a component of the workpiece into the toolmaterial. Thus the chemical composition of the carbide changes and that means a sharp decrease of the hardness of the carbide tool. If the chemical decomposition has reached the stage that the flow tress of the tool material is equal to the flow stress of the workpiece material, the decomposited layer is removed and the same mechanism starts again. If the bounder of the carbide material diffuses the carbide grains get loose and can easily be removed. The question is how to explain the minimum of wear for a constant cutting path of steel as a function of the cutting speed. For this explanation we have to consider two effects. The first effect gives an increase of tool wear. An increase of the cutting gives a higher temperature [2J. This means that the diffusion rate and also tool wear is increased. The second effect gives a sharp decrease of the tool wear. This sharp decrease occurs if the cutting speed is increased safar that the temperature in the chipcontactzone is high enough to give a transfor-mation from ferrite to austenite and to dissolve the iron carbides in the austenite. This transformed workpiece material needs (no iron carbides) a considerable longer cutting path to get the same flow stress as the decomposited tool material. Combination of the two effects explains the minimum. Also one can conclude that the location of the minimum in the wear-cutting speed relation depends upon all the quantities, which have an influence on the temperature of the chip contactzone. -4-3. Experimental set-up. In order to avoid the formation of an oxide layer on the contact surface of the chip immediately after the cutting process we carried out the cutting tests in a chamber filled with argon. Figure 2 shows schematically this experimental set-up. The workpiece material was C-45 or SAE 1045. The cutting speed was 2.5 m/ s wi th a feed of 0.05 mm/ rev. and a width of cut of 3 mm. These conditions were necessary in order to make thin foils by electrochemi-cal polishing (0 3 mm, thickness less than 0.3 rom). These dimensions were also necessary for the specimen holder of the electron microscope. The thinning process was started from one side of the chip in order to get a thin foil of the real contact surface of chip and tool [3J. The structure of the thin foils was made visible in a Philips EM 200 electron microscope. The electronmicrographs are a little unsharp. This unsharpness is caused by the magnetic properties of steel SAE 1045. , spindle --+-~~ -t-t---t-t ..........---- . -"~~tt 2: Experimental set-up for avoiding oxidation of the chip. -5-4. Results. Figure 3 shows the pearlite structure on some distance from the contact zone in the chip. It gives the plate structure of the iron carbide in ferrite. Figure 4 shows the diffraction pattern of the same material. The diameter of the diffracted area was l~m. Table 1 shows the camera constant (= Al) for the known ferrite circles and the measured and computed spacings of iron carbide. It holds [4J. d (hkl) with d(hkl) (hkl) R Al R spacing of two adjacent planes (hkl) [4J [5J ; Miller indices [4J Radius of the diffraction circle. Figure 5 shows the electronmicrograph of the contact area of the chip. This figure does not show the shape and the distribution of the iron carbides. Figure 6 gives the electron diffraction pattern of the same area as figure 5. The diameter of the diffraction wasl ~m. Table 2 shows the same information for the contact surface of the chip as table 1 does for the bulk material. Comparison of figure 3 and 5 shows that the plate shape of the iron carbide in figure 3 is fully disappeared in figure 5. It may be possible that the dark spots in figure 5 are iron carbides. -6-Figure 3: Electromicrograph of the pearlite structure of the bulk .material of the chip (x = 30.000). ,Figure 4: Electron diffraction pattern of figure 3. Diameter of the diffracted area 1 ~m. -7-Figure 5: Electronmicrograph of the chip contact area between chip and tool material (x = 100 .000). ' Figure 6: Electron diffraction pattern of figure 5. Diameter of the diffracted area 1 ~m. -8-TABLE 1. The computed and measured spacings of ferrite and iron carbide from the bulk of the chip material. Computation of the camera constant (AI) with the ferrite diffraction circles R [mm] 0 0 (hkl) d (hkl) [A] H [A mm] 29.8 110 2.027 60.4 42.0 200 1.433 60.2 51.8 211 1.170 60.6 59.7 220 1.013 60.5 67.0 310 0.906 60.7 72.9 222 0.827 60.3 AL = 6.05 -9-Measured (= d (hkl» and computed spacing of two iron carbides (= dT (hkl)Fe3c and dT (hkl)Fec) from figure 4. [4,5J. R [romJ d(hkl) dT (hkl)Fe3c dT(hkl)Fec 1. 78 3.399 3.40 2.38 2.542 2.545 2.43 2.490 2.50 2.53 2.391 2.387 2.80 2.161 2.16 2.92 2.072 2.067 2.06 3.00 2.016 2.013 3.23 1.873 1.872 3.58 1.690 1.690 1. 70 3.68 1.644 1.640 1.65 3.82 1.584 1.588 3.99 1. 516 1.511 4.05 1.494 1.50 4.30 1.407 1.405 4.50 1.344 1.342 4.65 1. 301 1.306 4.75 1. 274 1. 274 4.83 1.253 1. 253 5.38 1.125 1.124 1.12 5.45 1.110 1.111 5.52 1.096 1.097 -10-TABLE 2. The computed and measured spacings of ferrite and iron carbide from the contact zone of the chip material. computation of the camera constant (Al) with the ferrite diffraction circles [4]. R [mm] 0 0 (hkl) d(hkl)[A] >.l[A mm] 20.83 110 2.027 42.21 36.15 211 1.170 42.30 46.65 310 0.906 42.26 51.40 222 0.827 42.51 55.65 321 0.766 42.63 63.15 330 0.676 42.63 AI = 42.43 -11-Measured (= d (hkl» and computed spacings of iron carbide (= dT (hkl)pe3c) from figure 6. R [mm] 0 0 d (hkl) [A] d (hkl) [A] T Pe3C 16.65 2.548 2.545 17.7 2.397 2.387 18.9 2.245 2.262 20.0 2.122 2.107 22.6 1. 877 1.878 26.45 1.604 1.588 29.4 1.443 1.446 31. 75 1. 336 1.330 34.9 1. 216 1.216 38.1 1.114 1. 111 42.15 1.007 1.007 -12-Comparison of the diffraction pattern of figure 4 and 6 shows that the diameter of the ferrite grains of the contact zone are much smaller (number of paints on the diffraction circles) in comparison with the bulk material of the chip. The quantity of carbides in the contact zone seems less than in the bulk (weaker carbide circles). The reason for these weak carbide lines may be the thickness of the grains; these are too thick for the electron beam. From the tables 1 and 2 we can derive that the material in both is the same: ferrite and iron carbide and no martensite. -13-5. Discussion. If the material in the contact zone was on an austenite stable temperature and the iron carbides were solved in the austenite, martensite could be expected in the contact zone after the cutting test. However, the temperature rise (= ~T) of the chip of SAE 1045 by passing the primary shear zone is: T -n c£ P.s.w = with C 1400 N ~2 (specific stress) n 0.22 (strainhardening exponent) -1 0 -1 S.w = 0.45 J g C (specific heat) -3 -3 P 7.86 .10 g mm (specific mass) 1 £ = 73 {cotan ~ + tan (~-y)} o ~ 27.7 (shear angle) o y 6 (rake angle) It means that the chip temperature is always above 3300C; the martensite start temperature [6J. This holds even when one accounts for a heat loss by radiation or conduction to the workpiece or the tool. So,we can expect an annealed structure, as can be obsurved in Figure 5. But it may be possible to get the same structure without the transformation from ferrite to austenite. It is also possible to explain the spherical shape of the iron carbide in figure 5 without a transformation. The deformation process in the contact zone breaks the iron carbide plates. These pieces are shaped into a spherical form at the test temperature because of the decrease of their free enthalpy. So, it is not possible to confirm or reject our idea. In order to solve this problem we have two possibilities. The first is to cool down the chip immediately after the cutting process to room temperature. If the iron carbide was fully solved into the austenite and the cooling rate was high enough, we had to find martensite in the chip contact zone. An additional problem here is to cool the chip (for instance with liquid nitrogen) in an argon atmosphere in order to prevent oxidation of the chip. -14-The second possibility is to cut at a low cutting speed (0.2 m/s) and to compare the material structure of high and low cutting speed. The transformation of ferrite into austenite at low cutting speed is impossible because of the low temperature. However, this cutting speed gives a very rough chip contact layer caused by the built up edge. So it was impossible to get thin foils of the contact layer with the electropolishing technique. We have to use another thinning technique: ion beam thinning. -15-6. - The structure in the contact layer of SAE 1045 cut at high cutting speeds is very fine in contrary with the bulk of the chip. - It is not proven that at high cutting speeds the iron carbide in the contact layer of the chip is solved in the austenite and responsible for the minimum in the tool wear - cutting speed relation. It means that we could neither confirm nor reject our tool wear model. - For the verification of our model we have to use another thinning technique: ion beam thinning. - For making thin foils of the chip contact surface we ~ave to do our cutting experiments in an argon atmosphere. -16-References. 1. G. Vieregge: Zerspannung der Eisenwerkstoffe. Stahleisen M.B.H. DUsseldorf 1970. Seite 87. 2. P.C. Veenstra, Chr. Bus, A.G. Strous and A.P.A.J. Hulst: Cutting tool temperature an analysis of experimental results. PT-Report nr. 0164. Division of Production Technology. Eindhoven University of Technology, 1966. 3. J.H. Dautzenberg and J.A.B. van Dijck: The structure of copper rubbed on emery paper at different temperatures. (Will be published) . 4. B.D. Cullity: Elements of x-ray diffraction. Addison - Wesley Series in Metallurgy and Materials, 1978 pg. 340. 5. Powder Diffraction File. Alphabetical Index Inorganic Materials 1979. International Centre for Diffraction Data, 1601 Park Lane, Swarthmore, Pennsylvania 19081, U.S.A. 6. United States Steel: Atlas of isothermal transformation diagrams. United States Steel Corporation, Pittsburgh. U.S.A., 1961, pg. 34-35. 

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The anomalous tool wear behaviour in cutting steel SAE-1045

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