1 Duplex SS 42CrMo4 Ca-treated 316L Workpiece materials 1/82
Workpiece material 2 Carbon steel - Free cutting steel Machinability Carbon steel Alloy steel Austenitic SS Titanium Alloys Nickel based alloys Cobalt based alloys Special high temp alloys General construction steel Chemical, petrochemical, medical, gas and paper industry Energy production, aviation and space travel 2/82
Workpiece material 3 Chemical composition Thermal conductivity Mechanical properties Inclusions P M Non-alloy steel and cast steel Low-alloy steel and cast steel High-alloy steeland cast steel SS and cast steel (fer/mar) Stainless steel (austenitic) Workpiece origination Self-hardening K Grey cast iron Ductile cast iron Nodular cast iron (ferritic/perlitic) Material structure N Non-ferrous metals Aluminium and aluminium alloys S H Super alloys Titanium and titanium based alloys Hard cast iron Hardened steel 3/82
Machinability 4 Environment Surface integrity 800 800 600 600 400 400 200 200 0 0-200 -200-400 -400-600 -600-800 -800 0 50 100 150 200 250 3120 3100 3080 3060 3040 3020 3000 2980 Cutting forces F y F x F z 0 2 4 6 8 10 Chip formation f Tool wear v c 4/82
Machinability 5 Machining method Cutting conditions v c f Cutting material Cutting geometry Workpiece material Mechanical properties Chemical composition Thermal conductivity Inclusions Machinability Toolholders Workpiece raw material Work hardening Material structure Human factor Machine Clamping Cooling 5/82
Machinability 6 Material to be machined steel SS GCI etc. The process roughing - 1/2 rough - finishing Cutting speed V c Cutting depth a p Feed f Carbide grade Geometry The correct insert 6/82
The cutting process 7 7/82
The cutting process 8 Cutting forces The cutting force can be divided into: Axial force component Radial force component Tangential force component The tangential force determines the cutting force. Radial force Axial force The combination of tangential and radial force is the main cause of any vibration and workpiece deformation. Tangential force 8/82
The cutting process 9 Hard materials Superalloys Non-ferrous materials Fc = Kc11 * b * h 1-mc Kc11 = specific cutting force b = chip width h = chip thickness Cast iron Stainless steel Steel 0 1 000 2 000 3 000 4 000 5 000 6 000 7 000 (Typical example ) kc11 (N/mm²) 9/82
Workpiece materials 10 Materials with high ductility D O L O D 1 L 1 Materials with low ductility Low carbon steel and aluminium, Group 16. Soft Continuous chips, difficult to machine. Decrease ductility to increase machinability. D O Gray cast iron, Gr.12. Hard L O Discontinuous chips. Increase ductility to increase machinability. 10/82
Workpiece materials 11 High hardness materials Tool steel, Group 6 Hardened Steel, Group 7 Superalloys, Group 21 Cast iron, Group 15 Low hardness materials Aluminum, Group 16 Low carbon steel, Group 1 Materials that work harden diameter (proportional to penetration) Stainless steel, Groups 8, 9, 10 & 11 Superalloys, Groups 20, 21 11/82
Workpiece materials Easy to machine Difficult to machine Long chips (Ductility (%)) 12/82 alloy superalloy superalloy Ni alloy High High alloy alloy steel steel Stainless Stainless steel Unalloyed Unalloyed steel Aluminium Hardened steel Ti alloy Cast Cast iron iron Cast alu alloy Ductile Ductile iron Large cutting forces (Tensile strength)
The cutting process 13 Temperature Heat conductivity of tool material and workpiece material. Cutting speed. Geometry of cutting edge. This temperature (gradient) Largely determines the wear factor and tool life. 13/82
Thermal conductivity 14 Materials with high thermal conductivity Copper, Group 18 Aluminium, Group 16 Low carbon steel, Group 1 Materials with low thermal conductivity Titanium, Group 22 Superalloys, Groups 20, 21 14/82
Surface integrity 15 Surface integrity is the general term used to describe the properties and the condition of a machined workpiece with regard to the surface and subsurface. Residual tension MPa 800 800 600 600 400 Tension 400 200 200 0 0-200 Compression -200-400 -400-600 -600-800 -800 0 50 100 150 200 250 Depth under the surface (µm) (Typical example ) - Surface finish: Rt,Ra - Residual tension: Pressure or tensile forces - Self-hardening: Retention of austenite/hard martensite - Heat affected zone (HAZ): Lower hardness 15/82
Surface integrity 16 Workpiece material Tool Selfhardening Workpiece material Tool Selfhardening 16/82
Surface integrity 17 17/82
Surface stresses 18 Tension Crack Compression Crack Influencing factors are the cutting speed, cutting edge wear, cutting edge angle and cutting method (radial turning or classical), the cutting depth, the feed and the nose radius. Great influence on fatigue properties 18/82
Surface stresses 19 (Typical example ) Depth from surface 19/82
Machinability rating 20 Material Machinability Rating 9S20 cold rolled steel 100 Ductile cast iron 35 Stainless steel 440 50 Aluminium 2024-T 150 9S20 is assigned a rating of 100 and other materials are compared to this standard. 20/82
Machinability rating 21 P Non-alloy steeland cast steel. < 600 N/mm2 Low-alloy steel and cast steel < 900 N/mm2 High-alloy steeland cast steel > 900 N/mm2 Stainless steel and cast steel (fer/mar) < 750 N/mm2 M K Stainless steel (austenitic) Grey cast iron Ductile cast iron Nodular cast iron (ferritic/perlitic) > 750 N/mm2 N S Non-Ferrous metals Aluminium and aluminium based alloys Superalloys Titanium and titanium based alloys H Hard cast iron Hardened steel > 60 Shore > 45 HRC 21/82
Machinability rating 22 Aluminium & alloys Grey cast iron Steel Stainless steel Machinability Super alloys and titanium 22/82
Machinability rating Workpiece materials applications cutting materials 23 Class colour Subgroups P01 Material to be machined Steel, steel castings Application Finish turning and boring; high cutting speeds, small chip section, accuracy of dimensions and fine finish vibration-free operation. Cuttting conditions Change in properties Cutting material P Steel P10 P20 P30 P40 Steel, steel castings Steel, steel castings Malleable cast iron with long chips Steel, steel castings Malleable cast iron with long chips Steel, steel castings with sand inclusion and cavities Turning, copying, threading and milling, high cutting speeds, small or medium chip sections. Turning, copying, milling, medium cutting speeds and chip sections Turning, milling, planing, medium or low cutting speeds, medium or large chip sections, and machining in unfavorable conditions. Turning, planing, slotting, low cutting speeds, large chip section with the possibility of large cutting angles for machining in unfavorable conditions. Increasing cutting speed Increasing feed Resistance to wear Toughness P50 Steel, steel castings of medium or low tensile strength, with sand inclusion and cavities For operations demanding very tough carbide; turning, planing, slotting, low cutting speeds, large chip sections with the possibility of large cutting angles for machining in unfavorable conditions. Areas of application for the various cutting materials 1. Influence on cutting conditions. 2. Influence on properties of cutting materials. 23/82
Machinability rating 24 (Typical example ) MN 2006 Turning page 31 24/82
Machinability rating 25 Group Number 1 to 6 Family Name Mild and alloy steels 7 8 to 11 11 to 15 16 to 19 20 to 21 22 Hardened Steel Stainless steels Cast irons Non-ferrous alloys Superalloys /High temperature alloys Titanium alloys Rule of thumb: Within a family of workpiece material groups, machining difficulty increases as the group number increases. 25/82
Mild and Alloy Steels 26 Groups 1 through 7 0.028 to 2.0% carbon Small amounts of other metals Nickel Chromium Manganese 26/82
Group 1: Mild and Alloy Steels 27 Properties Carbon content < 0.28% Tough, cheap, and impact resistant Easily worked Soft and gummy Machining 50 to 100% machinability rating Stringy, continuous chips Watch for BUE Easy to machine at high cutting speeds High speed: MTCVD (AL2O3) Med. speed: CVD (TiC, TiN) Low speed: PVD (TiCN) Uses Hub caps, stampings, wheels 27/82
Group 3: Ordinary Carbon Steels 28 Properties Carbon content: 0.28 to 0.50% Harder and stronger Tough, cheap, and impact resistant Easily worked, soft and gummy Machining 45 to 65% machinability rating Stringy, continuous chips Watch for BUE Moderately difficult to machine High speed: MTCVD (AL2O3) Med. speed: CVD (TiC, TiN) Low speed: PVD (TiCN) Uses I-beams, auto frames, axle housings 28/82
Group 6: Tool Steels 29 Properties Carbon content: 0.50 to 2.0% Small amounts of nickel, molybdenum, chromium, and/or vanadium. Very high hardness. Tougher and stronger. Machining 35 to 65% machinability rating. Difficult to machine. Watch insert flank wear. Reduce cutting speed. High speed: MTCVD (AL2O3) Medium speed: CVD (TiC, TiN) Low speed: PVD (TiCN) If RC > 45, use CBN Uses Tool steel, springs, bearings, dies, punches 29/82
Stainless Steels 30 Groups 8 through 11. At least 10.5% chromium. Less than 1.2% carbon. Properties which increase from Group 8 to 9 to 10 to 11. Corrosion resistance. Hardness. Temperature resistance. 30/82
Stainless Steels 31 Alloyed steel with maximum 1.2% carbon and at least 10.5% chromium. Cr 2 O 3 Chromium Oxygen 31/82
Stainless Steels 32 Stainless steel structures Ferritic Martensitic Austenitic Duplex The microstructure and alloy elements are the determining factors. They determine properties such as heat resistance, corrosion resistance, oxidation resistance. And also the machinability!! Ferritic stainess steel (400 series, e.g. 405, 430, 442) (low carbon steel + Cr). Martensitic stainless steel (400 series, e.g. 403, 416, 422) (ferritic stainless steel + C). Precipitation hardened stainless steel (PH-steel, e.g. 15-5PH, 17-4PH, PH13-8Mo)) (martensitic stainless steel + Cu, Al, Nb). Austenitic stainless steel (300 series, e.g. 301, 304, 316) (ferritic stainless steel + Ni). Duplex stainless steel (200 series) (austenitic stainless steel - Ni + Mn, N). 32/82
Stainless Steels 33 Influence of material structure 120 100 Machinability (%) 80 60 40 20 0 Ferritic SS Martensitic SS Austensitic SS Duplex SS PH SS (Typical example ) 33/82
Stainless Steels 34 Machinability Mo Cr N Ni C Ti Mn S Ca Pb Molybdenum Chromium Build up edge problems. Hard, very homogenous surfaces (scales). Poor surface finish. Burring. Poor chip formation and difficult chip removal. Nitrogen Nickel Carbon Titanium Manganese Sulphur/phosphor Calcium Lead 34/82
Stainless Steels The PRE factor is a criterion for the corrosion resistance 35 The resistance of the stainless steel to pitting is indicated by the PRE factor (Pitting Resistance Equivalent). PRE factor = % Cr + 3.3 x % Mo + 30 x % N PRE factor = % Cr + % Ni (when no Mo or N) The PRE factor determines heavily the machinability 35/82
Stainless Steels 36 Cutting speed V 30 (m/min) Reference cutting speed - 30 minutes tool life -b/h= 10 - flat insert - untreated cutting edge - uncoated P20 Martensitic Martensitic - austenitic Duplex Austenitic (Typical example ) PRE value 36/82
Stainless Steels 37 Low thermal conductivity The heat which needs to be removed in the chip and the workpiece is concentrated in the insert in stainless steel. (plastic deformation) 37/82
Stainless Steels 38 Self-hardening (surface hardening) Hardness If the tension in the stainless steel exceeds the elongation limit, stainless steel will show self-hardening. This is the case in the shearing zone. (Typical example ) This is made worse through formation of Cr 2 O 3 (quickly and always). Distance from the surface 38/82
Cutting speed zones 39 Technically optimum Total Friction Wear Diffusion Oxidation Cutting Build up edge Temperature / cutting speed 39/82
Cutting speed zones 40 Cutting build up edge 1 2 3 Tendance for build up edge ± 60 m/min ± 100 m/min Cutting speed 40/82
Cutting speed zones 41 Cutting speed zone 1 Low productivity zone 40-60 (m/min) Use TiN or TiCN coated (PVD) tough inserts or uncoated tough inserts (P25-P40, K20). Use cooling to keep the temperature down. Use small chip sections (sharp inserts). High tool life is possible. Long finishing times Low productivity and high costs. Reliability questionable. 41/82
Cutting speed zones 42 Cutting speed zone 2 Build up edge wear zone 60-100 (m/min) Chip Burs on workpiece Burs on chip Build up edge Great build up edge in this area. Avoid cutting speed zone 2. 42/82
Cutting speed zones 43 Cutting speed zone 3 Roughing High productivity zone 100-300 (m/min) Use tough coated inserts (P25C) or wear resistant uncoated inserts (P15) or cermet. Use inserts with big positive rake (approx. 20 0 ). Aim for large chip sections (f > 0.15 (mm/t), a p > 1 (mm)). Do not use cooling except if there could be problems with chip removal. 43/82
Cutting speed zones 44 Cutting speed zone 3 Finishing High productivity zone 120-350 [m/min] Cutting speeds approx. 25% higher than in roughing. Use cermet, P15 (uncoated), PVD coated micrograin grades. Feed f = 0.05-0.15 (mm/t) and a p > 0.5 (mm). If f < 0.05 (mm/t) en a p < 0.5 (mm) use uncoated K20. Use abundant coolant to keep the temperature low. In contour milling with small radial cutting depths, apply a cutting depth factor and do not use coolant. 44/82
Stainless Steels 45 Machining in stainless steel requires five times as many cutting edges as the same process in classical steel. Be careful with other problems such as interrupted cuts and casting scales. Also pay attention to: Austenitic structure Duplex structure Nitrogen reinforced structure Precipitation hardened SS Pre-processing Threading (following) number of workpieces Avoid false economies Turning (previous) Insert wear 45/82
Stainless steel turning Chip formation 46 Burring Sticky chipping Build up edge (wear) 46/82
Stainless steel turning Chip formation 47 AISI 304 Ck 45 AISI 304 Ca 47/82
Stainless steel turning Machine 48 Select maximum stability and capacity. Avoid worn machines for accurate work. 48/82
Stainless steel turning Toolholder 49 Select the largest possible shank section. Select a strong insert clamping system. Minimize the projection length. Select sound seating. 49/82
Stainless steel turning Working method 50 Select varying cutting depths for heavy and lengthy roughing processes. Roughing with entering angle of 75 or 45. Then finish with 90. 50/82
Stainless steel turning Working method 51 For heavy roughing, use variable cutting depths. 51/82
Stainless steel turning Rough workpiece 52 First chamfer if possible. In burnished pieces, always begin by removing burnished residue. 52/82
Stainless steel turning Inserts 53 Select strong inserts with sharp geometries (entering angle). Select large nose radius. Select internal positive single sided inserts and external double sided negative inserts. 53/82
Stainless steel turning 54 Cutting conditions Use large cutting depths. Use large feeds. Change inserts regularly (not too much wear). 54/82
Stainless steel milling 55 Some advice 1. Smooth cutting process is important (smooth cutting geometry, large rake angle, sharp yet reinforced cutting edges (small T phase/honing)). 2. Good chip removal. 3. Cutting under the hard surface layer. 4. Use down-milling. 5. Limit heat development 1. cooling (at the right place). 2. thick chip (0.08 mm min h m ) to gain sufficient mass for maximum heat removal. 6. Average chip thickness (very important) 1. cutter positioning (10% D on exit side of workpiece). 2. feed = > T - phase/honing. 7. Cutting depth at least 1 mm and no finishing passes (unless absolutely essential) (friction). 8. Maximum carbide mass (to remove heat). 55/82
Stainless steel milling 56 Some advice feed and cutting depth average chip thickness (hm) is very important and critical for tool life (verify with cutting edge geometry - M/ME). Inco / SS (+ feed / + tool life) (titanium, if short tool life, reduce feed). if inserts with T-phase are used, the feed must be greater than this phase. avoid feed = 0 (helical interpolation milling instead of drilling). small cutting depths shorten the tool life. minimum cutting depth 1 mm. the smaller the cutting depth, the higher the cutting speed required (correct cutting temperature) (cutting speed factor in contour milling). 56/82
Stainless steel milling Some advice cutting speed High cutting speed method 15 to 20 minutes tool life. Low cutting speed method 45 to 60 minutes tool life. High pressure cooling >50 bar Higher cutting speed. Low tool life - 45 to 100 minutes. 57 Use high cutting speed if possible. High cutting speed method Low cutting speed method Most stainless steels are easily machined, except PH-SS and cooling is not necessary most of the time. Good chip evacuation (removal of chips from the workpiece). 1. Low cutting speed (low temperature) V c = 30-60 m/min. 2. Build-up in cutting edge zone. 3. High cutting speed (high temperature) V c = 100-300 m/min. 57/82
Group 8: Stainless Steels 58 Properties Little or no alloying elements other than carbon and chromium. Good corrosion and temperature resistance. Machining 40 to 65% machinability rating. Easy to machine. Soft, continuous chips. Watch for BUE (built-up edge). Use positive rake tools. Cobalt enriched zone. MTCVD coatings. Uses Cookware, surgical tools, pump components. 58/82
Group 9: Stainless Steels 59 Properties May contain nickel, molybdenum, sulphur, and vanadium. Increased hardness. Increased corrosion and temperature resistance. Machining 30 to 45% machinability rating. More difficult to machine. Stringy, brittle chips. Watch for notching at DOC line. Use positive rake tools Cobalt enriched zone. MTCVD coating. Uses Piping pumps, process equipment. 59/82
Group 10 and 11: Stainless Steels 60 Properties May contain nitrogen and titanium. Excellent corrosion and temperature resistance. Very high hardness. Machining 25 to 70% machinability rating. Very difficult to machine. Watch for surface work hardening. Flank wear and edge chipping are typical failure modes. Use positive rake tools. Cobalt enriched zone. MTCVD coatings. CBN and ceramics. Uses Piping, pumps, process equipment in demanding conditions. 60/82
Cast Irons 61 Groups 12 through 15 Greater than 2.0% carbon Tend to be abrasive to machine May also contain: Magnesium Silicon Sulphur Phosphorus Brake drums 61/82
Group 12: Cast Irons 62 Properties Carbon in form of flakes. Abrasive Low to medium hardness. Strong and cheap to produce. Machining 40 to 70% machinability rating. Moderately difficult to machine. Discontinuous chips. Machine at high cutting speeds. High speeds: AL2O3. Medium speeds: CVD (TiC, TiCN, AL2O3). Low speeds: PVD (TiAIN) and CVD (TiC). Uses Engine blocks, inexpensive castings. 62/82
Groups 13 & 14: Cast Irons 63 Properties Cerium and magnesium cause carbon to form spheroids. Harder and more abrasive. More ductile, less brittle. Machining Discontinuous chips. High speed: AL2O3; CBN; ceramic (SiN). Medium speed: CVD (TiC, TiCN, AL2O3). Low speed: PVD (TiAIN) and CVD (TiC). Uses Crankshafts, structural parts, pulleys, brakes. 63/82
Group 15: Cast Irons 64 Properties Silicon causes carbon to form spheroids. Called ductile cast iron. Excellent tensile strength. Good wear resistance. Cheaper and lighter than steel. Machining 35 to 60% machinability rating. High cutting forces. Analogous to interrupted-cut. Discontinuous chips. Negative rake for strength. High speed: AL2O3; CBN; ceramic (SiN). Medium speed: CVD (TiC, TiCN, AL2O3). Low speed: PVD (TiAIN) and CVD (TiC). Uses Gears, truck springs, turbo-compressor housings, crankshafts. 64/82
Non-Ferrous Alloys 65 Groups 16 through 19. Less than 50% iron. Most metals are soft (except for tungsten carbide). Machinability varies over a wide range. Aluminium piston 65/82
Aluminium 66 Low density. High strength. Good thermal conductivity. Good corrosion resistance. 1xxx 99% Al 2xxx + Cu 3xxx + Mn 4xxx + Si 5xxx + Mg 6xxx + Mg, Si 7xxx + Zn 8xxx + Other elements 66/82
Aluminium Some advice General Carbide grade or PCD. Polished rake surface. Positive rake angle. Coarse pitch cutter. Large chip evacuation grooves. 67 Cutting speed 600 to 2000 (max) m/min with carbide inserts. 1500-6000 m/min with PCD inserts. Feed 0.15 to 0.50 mm/rev. 67/82
Aluminium Some advice Build-up of cutting edge Adjust cutting speed / use coolant / very positive geometry. 68 Chip control and evacuation Open pitch cutter when milling. Wash chips away with coolant. Burring Use micro-sharp cutting edges. Abrasive wear Carbide grade or PCD. Finishing With coolant, not for roughing. Close pitch cutters For large table feed, but needs power. 68/82
Group 16: Aluminum (<16% Si) 69 Properties Properties enhanced by alloying with silicon, copper, and magnesium. High strength to weight ratio and corrosion resistance. Excellent tensile strength. Good wear resistance. Cheaper and lighter than steel. Group 16 includes silver, brass, and gold. Machining 90 to 270% machinability rating. Stringy, continuous chips. Watch for BUE. Free machining; run at high cutting speeds. Use positive rake tooling. Uses Auto body panels, wheels, aerospace applications. 69/82
Group 17: Aluminum (>16% Si) 70 Properties Alloyed to enhance strength. Good wear resistance. Increased hardness. Very abrasive. Group 17 includes aluminum-bronze, cupro-nickel, and magnesium-bronze. Machining 60 to 180% machinability rating. Non-free machining. Machine at slower cutting speeds. Uses Engine blocks. 70/82
Group 18: Difficult Non-Ferrous 71 Properties Group 18 includes difficult to machine alloys of copper, babbit, and bronze. Good strength. Good corrosion resistance. High ductility and toughness. Very abrasive. Machining 60 to 180% machinability rating. Watch for BUE. Tends to tear. Uses Bushings, bearings, valve seats. 71/82
Group 19: Super Hard Alloys 72 Properties Group 19 includes tungsten carbide. Very high hardness. Very high strength. Abrasive Machining 5 to 15% machinability rating. Machine at very slow cutting speeds. Uses Dies, punches, and wear parts. 72/82
Superalloys/High Temperature Alloys 73 Groups 20 through 21. Good corrosion resistance. High strength. Maintain properties at elevated temperatures. Very difficult to machine. 73/82
Superalloys/High Temperature Alloys 74 Nickel, iron and cobalt alloys, the most important properties being: Exceptional strength. Corrosion resistance at high temperatures. 74/82
. Superalloys/High Temperature Alloys Superalloys 75 Nickel based Cobalt based Iron based Inconel 600 Waspoloy René N4 MAR-M-247 Nickel-iron based MAR-M 509 X40 Inconel 718 Haynes 188 Inconel 706 FSX-414 Hastelloy X A-286 Discaloy Haynes 556 75/82
Titanium Alloys 76 Titanium Alpha alloy Alpha-Beta alloy Beta alloy HCP Mix BCC High strength/weight ratio. High strength/creep resistance up to 500 C. Excellent corrosion resistance. 76/82
Superalloys and Titanium Alloys 77 Machinability of superalloys More heat generation upon machining (structure) and low thermal conductivity. This means higher cutting temperatures. Increasing strength at higher temperatures (basic property) (cutting temperature). This means higher cutting forces. Difficult chip control (greater toughness). Carbide precipitates (due to heat treatment). Work-hardening (hard layer). Machinability of titanium alloys Low thermal conductivity. This means higher cutting temperatures. Small Young s modulus (workpiece deformation, tolerances, vibrations). Chemically very reactive (oxidation) (ignition and combustion during machining). 77/82
Superalloys and Titanium Alloys General recommendations 78 Machine in softest possible state. Positive rakes. Sharp cutting edges. Strong basic geometry (nose radius). Stable working conditions. Avoid workpiece deformation. Use small entering angles. Single-pass cutting or varying cutting depth. 78/82
Group 20: Superalloys 79 Properties Hardness < 35RC. Group 20 includes nickel, cobalt, and iron alloys. Very high hardness. Very abrasive. Machining 9 to 45% machinability rating. Machine at very slow cutting speeds. Work hardens rapidly. Notching at DOC line. High cutting forces and temperatures. Watch for BUE. Uses Prosthetics, heat exchangers, aviation, maritime, plumbing. 79/82
Group 21: Superalloys 80 Properties Hardness > 35RC. Group 21 includes nickel, cobalt, iron alloys, Inconel 600, Hastelloy X, Monel 400. Extremely high hardness. Very abrasive. Similar issues as Group 20 but to a greater degree. Machining 9 to 15% machinability rating. Machine at extremely slow cutting speeds. Work hardens rapidly. Notching at DOC line. High cutting forces and temperatures. Watch for BUE. Uses Jet engines. 80/82
Group 22: Refractory Metals 81 Properties Group 22 includes titanium, niobium, tantalum, molybdenum, and tungsten. High temperature resistance. Poor oxidation resistance in air. High thermal conductivity. Flex readily. Sometimes flammable. May react with tool materials. Low coefficient of thermal expansion. Machining 5 to 30% machinability rating. Machine at very low cutting speeds. Watch for BUE. Uses Aircraft frames, nuclear plants. 81/82
82 Questions? Questions? 82/82