Engineering Materials Lecture Notes PDF

Engineering Materials Manufacturing Methodologies, 1TE631 Agenda Type of materials Materials limit the manufacturing method to choose Material properties change during manufacturing All engineering materials at once Wood Plastics Ferrous alloys Non-ferrous alloys Ceramics...

Engineering Materials Manufacturing Methodologies, 1TE631 Agenda Type of materials Materials limit the manufacturing method to choose Material properties change during manufacturing All engineering materials at once Wood Plastics Ferrous alloys Non-ferrous alloys Ceramics Wood Hardwood (oak, maple, walnut, mahogany, ash, hickory, birch, teak) easy to cut in a lathe multiple passes needed thicker than 3 mm CNC cut thinner than 3 mm laser cut MDF with resin (it burns in laser cut) good surface properties engravement possible Softwood (pine, spruce, cedar, cypress, redwood, plywood, balsa) better to laser cut upcut and downcut choice for surface finish Upcut versus downcut All engineering materials at once Wood Plastics Ferrous alloys Non-ferrous alloys Ceramics Plastics Thermosetting polymers resin and a curing agent forms a chemical reaction during this “curing” process, material is hardened not possible to revert the process, not possible to recycle UV curing, electronic casing for chips (jetting) air curing, two components superglue (joining) examples: epoxy vinyl ester polyester matrix material in composites a) carbon reinforced composite b) aramid reinforced composite c) glass reinforced composite Composites Composites CNC milling of a composite sheet Carbon reinforced epoxy reduced feed rate usecase as covering with pre-pregs increased rotation speed low thermal conductivity, heat localizes resin may burn, reduce the feed rate water jet is an option, but no tight tolerances possible Plastics Thermoplastic polymers amorphous or semi-crystalline remelting and reforming possible recycling change the properties Examples: Polyamides PA 6 or 6.6 PA 11 (bio-based) Low Density PolyEthylene (LDPE) PA, Nylon PA 12 (petroleum or bio-based) Polyethylene LDPE, HDPE PET PLA (bio-based, 3D printing) ABS (hardness, rigidity, UTS 40 MPa) PC (PolyCarbonate, impact resistance, UTS 60 MPa) Elastomeric polymers very high stretchability Examples: TPU (Thermoplastic PolyUrethane) Volcanized rubber Rubber All engineering materials at once Wood Plastics Ferrous alloys Non-ferrous alloys Ceramics Ferrous alloys, Iron (Fe) + Carbon (C) = Steel Inter-metallic compound cementite (Fe3C) is hard and brittle low carbon steel, if C < 0.15% good weldability and ductility drawn tubes, thin sheets, and wire rods surface hardening for wear resistance mild steel, if C amount is between 0.15-0.3% structural work weldability upto 0.25% of C Forging forgings, stampings, sheet and plates, bars, rods, tubes Drawn tube medium carbon steel, if C between 0.3-0.7% stronger and better wearing properties railway axles, rotors and discs, wire ropes, marine shafts, agricultural tools high carbon steel, if C between 0.7-1.3% even more hardened by quenching used in cold conditions (less than 150 °C) cast iron, C > 1.7% (upto 4%) lower melting temperature, easy to cast cooling rate depending gray, white, malleable, ductile cast iron Quenching Above 2%, not steel but cast iron, cooling rate and other alloying elements are important Steel alloys Less than 2% carbon and other alloying elements Ferritic stainless steel, 0.15% carbon, 6-12% chromium and 0.5% nickel magnetic, no hardening possible food processing plants, dairy equipment low price Martensitic stainless steel, 0.15-1.25% carbon, 12-18% chromium hardening possible but reduces the corrosion resistance surgical knives, bolts, nuts, screws, blades Austenitic stainless steel, 0.08-0.2% carbon, more nickel 18/8 steel: 18% chromium, 8% nickel, 1.25% manganese, 075% (max) silicon high corrosion resistance chemical plants, household utensils high price Tool steels cut steel at high speeds At elevated T=600°C maintains hardness: red hardness High Speed Steel (HSS) with 18% tungsten (expensive, T-series) HSS with 6% tungsten and 6% molybdenum (M-series) Super HSS with 10% cobalt, 20% tungsten Steel alloys  Special steel alloys Manganese steels wear resistant used in railway points and crossings Nickel steels corrosion resistance non-magnetic, low thermal expansion coefficient used in turbine blades, internal combustion engine valves with chromium, increased UTS and IZOD strength Silicon steels around 3% silicon decreases magnetic hysteresis used in transformers, electric machines silico-manganese steels for springs Heat treatment of carbon steels Improving mechanical properties: temperature increase and waiting long enough to have homogeneous temperature specified cooling rate that is the most critical factor Types of heat treatment: annealing normalizing hardening tempering Normalizing Annealing Pieces in a furnace, bringing up to the temperature: heating rate is not decisive around 3 min for each millimeter thickness to get an even distribution Softening the material by a slow cooling, cooling with the furnace switched off: internal stresses are relieved increased ductility (grain growth) Annealing Material temperature in °C Dead mild steel (carbon < 0.15%) 870-930 Mild steel (carbon 0.15-0.3%) 840-870 Medium carbon steel (carbon 0.3-0.7%) 780-840 High carbon steel (carbon 0.7-1.5%) 760-780 Normalizing, hardening, tempering Normalizing: heating up just the same, but cooling happens in still air (quicker). No softening but internal stresses are relieved (the stress is normalized to zero) Hardening: cooling happens very fast, simply dropping in water/oil mixture, also called quenching. The carbon content has to be high (more than 0.25% but better more). Tempering: if carbon content is high enough, very hard but brittle piece will come out. Tempering is to bring up the temperature to 150-600°C and cool down slowly. Case hardening: if dead mild steel with too low content carbon needs to be hardened, it is put in charcoal and kept at a high temperature (as in annealing) for a few hours such that carbon enters from the surface 1-2 mm that is then used for hardening (cooled down quickly). A hard surface with a soft and tough interior is the result. All engineering materials at once Wood Plastics Ferrous alloys Non-ferrous alloys Ceramics Non-ferrous alloys Copper: corrosion resistance and the best conductor, wire drawn, sheet beaten, alloying with zinc to brass, tin to bronze, nickel to cupro-nickels. Aluminum: corrosion resistance and a fine conductor ductile and melleable, thin sheets, cable drawn, cans. Alloying with magnesium for better properties. Tin: resistance to acidic conditions, low melting point, used in solders. Zinc: high corrosion resistance, used as coating to steel (galvanized steel) Non-ferrous alloys Brass: Cartridge brass, 70% Cu (copper) + 30% Zn (zinc), deep drawing cartridge Admirability brass, 70% Cu + 29% Zn + 1% Sn (tin), ships fitting Muntz’s metal, Cu + 40-45% Zn, condenser tube, heat exchanger, preheater Naval brass, 60% Cu + 39% Zn + 1% Sn, ships fitting Tin bronze: Naval brass Upto 10% of tin is added increasing strength and hardness, too much tin creates brittle intermetallic compound Cu3Sn Phoshor bronze, added 0.5% phosphorous for better fluidity in fine casting Leaded bronze, less than 2% lead for a better machinability (self lubricating) Gun-metal, 88% Cu + 10% Sn + 2% Zn, bearing bushes, glands, pumps Bell-metal, 20-25% of tin is added used in cymbals Silicon bronze, 1-4% Si to copper, extreme corrosion resistance, boiler and marine fittings Manganese bronze, 55-60% Cu + 40% Zn + 3-5% Mn, ship’s propellers Different special alloys Cupro-nickels, copper and nickel mix well if they are melted together, extreme corrosion resistance, used in thermocouples, resistors Aluminum alloys: Mixed with magnesium for higher strength, L-M series, extrusion such as in profiles Duraluminum, Al + 4% Cu + 0.5% Mg (magnesium) + 0.5% Mn (manganese) Nickel alloys: German silver, cupro-nickel with zinc, 60% Cu + 30% Ni + 10% Zn, household devices Inconel, nickel-chromium-based superalloy, used in high temperature and corrosive applications (gas turbine blades, Formula One exhaust system) German silver Alloy 625: Inconel 625, Chronin 625, Altemp 625, Haynes 625, Nickelvac 625 Nicrofer 6020 and UNS designation N06625 Alloy 600: NA14, BS3076, 2.4816, NiCr15Fe (FR), NiCr15Fe (EU), NiCr15Fe8 (DE) and UNS designation N06600. Alloy 718: Nicrofer 5219, Superimphy 718, Haynes 718, Pyromet 718, Supermet 718, Udimet 718 and UNS designation N07718 All engineering materials at once Wood Plastics Ferrous alloys Non-ferrous alloys Ceramics Ceramics Hard, brittle, corrosion resistant, sometimes insulating material Machinable (soft) ceramics Macor, excellent electrical and thermal insulator, machinable via carbide tools Shapal, high thermal conductivity, and excellent mechanical strength Boron-Nitride, high heat capacity, thermal conductivity, low dielectric constant Harder ceramics (tougher and more difficult to cut) Zirconia, high hardness, wear, high fracture toughness Silicon carbide, extremely hard and has exceptional thermal shock and impact resistance Macor, characteristics How to Mill Macor Typical head speeds are 1000–1500 rpm with a chip load of 0.05mm per tooth. Depths of cut are as for turning. Climb milling prevents material being pulled off the edge of the MACOR®. Milling Macor Speeds and Feeds Cutting Speed: 23 to 35 sfpm (1 to 1.4 meters per minute) Feed rate:.002”/tooth (.05mm/tooth) Depth of cut:.15” to.2” (4 to 5 mm) Milling Tool Suggestions Carbide or equivalent Two or four flute and helix milling cutters work well Do not use roughing or chipbreaker mills Ceramics Zirconia in dental implants Boron nitride as nozzle Thanks a lot for the attention!