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GT ME 4210 - LECTURE NOTES

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MhiiC tti T lMachining -Cutting Toolsver. 1ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 20091OverviewOverview• Cutting tools• Tool materialsME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 20092Cutting ToolsCutting Tools•19thCentury19Century– Plain carbon steels (HB ≈ 700 kg/mm2)–Poor cutting propertiesPoor cutting properties• begin to lose strength 200-300oC• used in taps, cheap drillsp, p• 1850’s–Discovery of Fe3C (cementite)–Discovery of Fe3C (cementite)– Hardening of steelME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 20093Cutting ToolsCutting Tools• 1890’s: Moisson–Used electrical arc furnaceUsed electrical arc furnace– Tried to make diamonds–Made lots ofcarbidesMade lots of carbidesME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 20094Cutting ToolsCutting Tools• 1900: Development of high-speed steel by Taylor, et al.yy,– add W, Mo, Cr, V to steel ⇒ FexMyC–not much harder (HB≈800 kg/mm2)not much harder (HB ≈800 kg/mm)– stable at high temperatures–20-30% by volume carbides2030% by volume carbides– can be used at twice the speed of tool steelsME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 20095steelsCutting ToolsCutting Tools• Tungsten carbide (WC)–HB≈2,000 kg/mm2HB 2,000 kg/mm– Too brittle for cuttingME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 20096Cutting Tools• 1923: SchroterWC + CoWC–WC + Co• Co wets WC and binds together•Cemented carbide structureWC1-3 μmCemented carbide structure– Twice the speed of WC–Not as tough as HSS–Not as tough as HSS• fine grain structure helps–Machine vibration is problemMachine vibration is problem• rigid machines help–Solubility of WC in Fe≈5%Co in betweenME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 20097Solubility of WC in Fe ≈5%Cutting ToolsCutting Tools• 1931: Complex carbides developed–TiCadded to increase chemical stabilityTiCadded to increase chemical stability– 2x the cutting speed of WC + Co–lower strengthlower strength– increased wear resistanceME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 20098Cutting Toolsg• 1960’s: Increased cutting speeds• Powder metallurgy–production of carbide insertsp– disposable inserts, no resharpening–coatings feasible:TiC, TiN, Al2O3coatings feasible: TiC, TiN, Al2O3• ≈ 5 μm layer to minimize strain•very wear resistanty• 50-70% of tool life expended before coating penetratedME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 20099Tool CoatingsTool CoatingsME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200910Cutting ToolsCutting Tools•Optimization of bonding between•Optimization of bonding between coating and substrateTiCAlOWC+CoTiCTiNAl2O3TiNME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200911Cutting ToolsCutting Tools• Aluminum oxide (Al2O3)–wear resistant, but low strengthwear resistant, but low strength•Al2O3+ 30% TiC: hot-pressedincreased strength 1530%–increased strength 15-30%– higher speeds - 3-5x of carbidesME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200912Cutting ToolsCutting Tools•Si3N4Si3N4– high toughness in bulk formlow thermal expansion–low thermal expansion– not for steel, dissolves - fast wear•Al2O3+ Si3N4 (SiAlON)cuts Ni superalloys and steels–cuts Ni superalloys and steelsME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200913Cutting ToolsCutting ToolsDi d (C)•Diamond (C)–HB ≈10,000 kg/mm2WCdiamonds1 mm–soluble in steel– good for aluminumWC– good for Si-Al alloys– 10-40 μm particles are sintered onto a WC substrate ⇒polycrystalline toolME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200914Cutting Toolsg• Cubic Boron Nitride (CBN)()– more stable with respect to steel and Ni–HB ≈ 4,500 kg/mm2–cuts very hard steels (10x carbide)y()– cuts Ni-based super alloys (10x carbide)– wears quickly at low speeds, only good at high speedsME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200915ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200916ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200917ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200918SummarySummary• Cutting tools•Tool materialsTool materialsME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200919ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT


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GT ME 4210 - LECTURE NOTES

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