İmal Usulleri Döküm için Sıcaklık ve Yoğunluk Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 T emperature & Density for Castings Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 FIGURE 5.1 (a) T emperature as a function of time for the solidi?cation of pure metals. Note that freezing takes place at a constant temperature. (b) Density as a function of time. Temperature Time Cooling of liquid Cooling of solid B A Liquid Liquid + solid Solid Freezing begins Freezing ends Freezing temperature Specific density Time Shrinkage of liquid Shrinkage of solid Solidification shrinkage (a) (b)Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 T wo-Phased Alloys FIGURE 5.2 (a) Schematic illustration of grains, grain boundaries, and particles dispersed throughout the structure of a two-phase system, such as lead-copper alloy. The grains represent lead in solid solution of copper, and the particles are lead as a second phase. (b) Schematic illustration of a two-phase system, consisting of two sets of grains: dark and light. Dark and light grains have their own compositions and properties. (b) (a)Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Phase Diagram for Nickel-Copper FIGURE 5.3 Phase diagram for nickel-copper alloy system obtained by a low rate of solidi?cation. Note that pure nickel and pure copper each have one freezing or melting temperature. The top circle on the right depicts the nucleation of crystals; the second circle shows the formation of dendrites; and the bottom circle shows the solidi?ed alloy with grain boundaries. Solid (42% Cu-58% Ni) Liquid (50% Cu-50% Ni) First solid (36% Cu-64% Ni) Liquid (58% Cu-42% Ni) 0 36 42 50 58 67 100 Solid solution Alloy composition Liquid solution Fraction liquid 0 1 Solidus Liquidus L + S Solid solution (50% Cu-50% Ni) 1981 C S C O C L 1082 1980 2280 2350 2395 2651 1455 1249 1288 1313 Temperature (°F) °C Composition (% by weight) Copper (Cu) 100 64 58 50 42 33 0 Nickel (Ni)Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Irn-Iron Carbide Phase Diagram FIGURE 5.4 (a) The iron-iron carbide phase diagram. (b) Detailed view of the microstructures above and below the eutectoid temperature of 727°C (1341°F). Because of the importance of steel as an engineering material, this diagram is one of the most important phase diagrams. 400 500 600 700 800 900 1000 1100 0 0.5 1.0 1.5 2.0 2.5 1000 1500 2000 727°C °F Temperature (°C) Carbon (% by weight) ! + Fe 3 C " " + Fe 3 C Fe 3 C Ferrite ! ! ! ! ! " + ! Temperature (°C) Carbon (% by weight) 1000 1200 1400 800 600 400 1600 0 1 2 3 4 5 6 6.67 1000 1500 2500 2000 Cementite (Fe 3 C) Liquid 727°C 1495°C 1538°C 1394°C 912°C °F 0.77% 0.022% 4.30% 2.11% 1148°C " (ferrite) " + cementite ! + cementite ! + liquid # (Ferrite) Detail view (a) (b) ! (austenite) "+!Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 T exture in Castings FIGURE 5.5 Schematic illustration of three cast structures of metals solidi?ed in a square mold: (a) pure metals, with preferred texture at the cool mold wall. Note in the middle of the ?gure that only favorable oriented grains grow away from the mold surface; (b) solid-solution alloys; and (c) structure obtained by heterogeneous nucleation of grains. (a) Chill zone Equiaxed structure Equiaxed zone (b) (c) Columnar zoneManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Alloy Solidi?cation & T emperature FIGURE 5.6 Schematic illustration of alloy solidi?cation and temperature distribution in the solidifying metal. Note the formation of dendrites in the semi-solid (mushy) zone. L + S T S T L Liquid Solid Solid Solid Mushy zone Dendrites Mold wall Liquid Liquid Temperature Alloying element (%) S L Liquidus Solidus Pure metalManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Solidi?cation Patterns for Gray Cast Iron FIGURE 5.7 Schematic illustration of three basic types of cast structures: (a) columnar dendritic; (b) equiaxed dendritic; and (c) equiaxed nondendritic. Source: After D. Apelian. (a) (b) 0.05–0.10% C Steel 0.25–0.30% C Steel Minutes after pouring Minutes after pouring 0.55–0.60% C Steel 8 11 40 60 90 102 5 2 15 2 16 2 Sand mold Chill mold Sand mold Chill mold Sand mold Chill moldManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Cast Structures FIGURE 5.9 Schematic illustration of cast structures in (a) plane front, single phase, and (b) plane front, two phase. Source: After D. Apelian. (a) (b) (c) Solid Solid Solid Liquid Liquid Liquid Mold wall (a) Solid Liquid Mold wall Liquid (b) FIGURE 5.8 Schematic illustration of three basic types of cast structures: (a) columnar dendritic; (b) equiaxed dendritic; and (c) equiaxed nondendritic. Source: After D. Apelian. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Mold Features FIGURE 5.10 Schematic illustration of a typical sand mold showing various features. Open riser Vent Pouring basin (cup) Drag Cope Sand Sprue Sand Flask Parting line Mold cavity Well Gate Core (sand) Blind riser RunnerManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 T emperature Distribution FIGURE 5.11 T emperature distribution at the mold wall and liquid-metal interface during solidi?cation of metals in casting. Room temperature Distance at mold–air interface at metal–mold interface Melting point Temperature Air Solid Liquid !T !T MoldManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Skin on Casting FIGURE 5.12 Solidi?ed skin on a steel casting; the remaining molten metal is poured out at the times indicated in the ?gure. Hollow ornamental and decorative objects are made by a process called slush casting, which is based on this principle. Source: After H.F . Taylor, J. Wulff, and M.C. Flemings. 5 s 1 min 2 min 6 min A B Chvorinov’s Rule: Solidi?cationtime=C ! Volume Surfacearea " nManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Shrinkage Contraction (%) Expansion (%) Aluminum 7.1 Bismuth 3.3 Zinc 6.5 Silicon 2.9 Al - 4.5% Cu 6.3 Gray iron 2.5 Gold 5.5 White iron 4-5.5 Copper 4.9 Brass (70-30) 4.5 Magnesium 4.2 90% Cu - 10% Al 4 Carbon steels 2.5-4 Al - 12% Si 3.8 Lead 3.2 TABLE 5.1 Volumetric solidi?cation contraction or expansion for various cast metals. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Cast Material Properties FIGURE 5.13 Mechanical properties for various groups of cast alloys. Compare with various tables of properties in Chapter 3. Source: Courtesy of Steel Founders' Society of America. Steel Nodular iron Gray iron Malleable iron Aluminum based Copper based Magnesium based Nickel based Zinc based Ultimate tensile strength (psi x 10 3 ) 300 280 260 240 220 200 180 160 140 120 100 80 60 40 20 0 2000 1800 2000 1800 1600 1400 1200 1000 800 600 400 200 MPa (a) 300 280 260 240 220 200 180 160 140 120 100 80 60 40 20 0 1600 1400 1200 1000 800 600 400 200 Steel Nodular iron Gray iron Malleable iron Aluminum based Copper based Magnesium based Nickel based Zinc based Yield strength (psi x 10 3 ) MPa (b) Nodular iron Gray iron Malleable iron Aluminum based Copper based Magnesium based Nickel based Zinc based Titanium metal Titanium alloys Cast steel 0 5 10 20 25 30 15 0 50 100 200 150 GPa Modulus of elasticity (psi x 10 6 ) 0 10 12 8 6 4 2 Wrought Cast Steel Nodular iron Gray iron Malleable iron Aluminum based Magnesium based Titanium metal Titanium alloy Tensile strength/density ratio (in x 10 5 ) (d) (c) Nodular iron Gray iron Aluminum based Copper based Magnesium based Nickel based Zinc based Steel Malleable iron 800 700 600 500 400 300 200 100 0 Brinell harbness (HB) (e) Malleable iron 70 60 50 40 30 20 10 0 90 80 70 60 50 40 30 20 10 0 Steel Nodular iron Gray iron J Impact energy (ft-lb, Charpy V-notch) (f) 70 60 50 40 30 20 10 0 Nodular iron Malleable iron Copper based Nickel based Steel Gray iron Copper based Nickel based Reduction of area (%) (h) Nodular iron Gray iron Aluminum based Copper based Magnesium based Nickel based Zinc based Steel Malleable iron 70 60 50 40 30 20 10 0 Elongation (%) (g)Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 General Characteristics of Casting TABLE 5.2 General characteristics of casting processes. Evaporative Permanent Sand Shell pattern Plaster Investment mold Die Centrifugal Typical materials cast All All All Nonferrous All All Nonferrous All (Al, Mg, (Al, Mg, Zn, Cu) Zn, Cu) Weight (kg): minimum 0.01 0.01 0.01 0.01 0.001 0.1 < 0.01 0.01 maximum No limit 100+ 100+ 50+ 100+ 300 50 5000+ Typ. surface ?nish (µm R a ) 5-25 1-3 5-25 1-2 0.3-2 2-6 1-2 2-10 Porosity 1 3-5 4-5 3-5 4-5 5 2-3 1-3 1-2 Shape complexity 1 1-2 2-3 1-2 1-2 1 2-3 3-4 3-4 Dimensional accuracy 1 3 2 3 2 1 1 1 3 Section thickness (mm): minimum: 3 2 2 1 1 2 0.5 2 maximum: No limit — — — 75 50 12 100 Typ. dimensional tolerance 1.6-4 ±0.003 ±0.005- ±0.005 ±0.015 ±0.001- ±0.015 (0.25 for 0.010 0.005 small) Cost 1,2 Equipment 3-5 3 2-3 3-5 3-5 2 1 1 Pattern/die 3-5 2-3 2-3 3-5 2-3 2 1 1 Labor 1-3 3 3 1-2 1-2 3 5 5 Typical lead time 2,3 Days Weeks weeks Days Weeks Weeks Weeks- Months months Typical production rate 2,3 1-20 5-50 1-20 1-10 1-1000 5-50 2-200 1-1000 Minimum quantity 2,3 1 100 500 10 10 1000 10,000 10-10,000 Notes: 1. Relative rating, 1 best, 5 worst. For example, die casting has relatively low porosity, mid- to low shape complexity, high dimensional accuracy, high equipment and die costs and low labor costs. These ratings are only general; signi?cant variations can occur depending on the manufacturing methods used. 2. Data taken from Schey, J.A., Introduction to Manufacturing Processes, 3rd ed, 2000. 3. Approximate values without the use of rapid prototyping technologies.Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Typical Applications & Characteristics TABLE 5.3 Typical applications for castings and casting characteristics. Type of Alloy Application Castability * Weldability * Machinability * Aluminum Pistons, clutch housings, intake mani- folds, engine blocks, heads, cross mem- bers, valve bodies, oil pans, suspension components G-E F* G-E Copper Pumps, valves, gear blanks, marine pro- pellers F-G F G-E Gray Iron Engine blocks, gears, brake disks and drums, machine bases E D G Magnesium Crankcase, transmission housings, portable computer housings, toys G-E G E Malleable iron Farm and construction machinery, heavy- duty bearings, railroad rolling stock G D G Nickel Gas turbine blades, pump and valve com- ponents for chemical plants F F F Nodular iron Crankshafts, heavy-duty gears G D G Steel (carbon and low alloy) Die blocks, heavy-duty gear blanks, air- craft undercarriage members, railroad wheels F E F-G Steel (high al- loy) Gas turbine housings, pump and valve components, rock crusher jaws F E F White iron (Fe 3 C) Mill liners, shot blasting nozzles, railroad brake shoes, crushers and pulverizers G VP VP Zinc Door handles, radiator grills E D E * E, excellent; G, good; F, fair; VP, very poor; D, di?cult.Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Properties & Applications of Cast Iron TABLE 5.4 Properties and typical applications of cast irons. Ultimate Tensile Yield Elonga- Cast Strength Strength tion in Iron Type (MPa) (MPa) 50 mm (%) Typical Applications Gray Ferritic 170 140 0.4 Pipe, sanitary ware Pearlitic 275 240 0.4 Engine blocks, machine tools Martensitic 550 550 0 Wear surfaces Ductile Ferritic 415 275 18 Pipe, general service (Nodular) Pearlitic 550 380 6 Crankshafts, highly stressed parts Tempered 825 620 2 High-strength machine parts, wear Martensite resistance Malleable Ferritic 365 240 18 Hardware, pipe ?ttings, general engineering service Pearlitic 450 310 10 Couplings Tempered 700 550 2 Gears, connecting rods White Pearlitic 275 275 0 Wear resistance, mill rollsManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Nonferrous Alloys TABLE 5.5 Typical properties of nonferrous casting alloys. Casting UTS Yield Strength Elongation Hardness Alloy Condition Method * (MPa) (MPa) in 50 mm (%) (HB) Aluminum 357 T6 S 345 296 2.0 90 380 F D 331 165 3.0 80 390 F D 279 241 1.0 120 Magnesium AZ63A T4 S, P 275 95 12 — AZ91A F D 230 150 3 — QE22A T6 S 275 205 4 — Copper Brass C83600 — S 255 177 30 60 Bronze C86500 — S 490 193 30 98 Bronze C93700 — P 240 124 20 60 Zinc No. 3 — D 283 — 10 82 No. 5 — D 331 — 7 91 ZA27 — P 425 365 1 115 * S, sand; D, die; P, permanent mold.Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Microstructure for Cast Irons FIGURE 5.14 Microstructure for cast irons. (a) ferritic gray iron with graphite ?akes; (b) ferritic nodular iron, (ductile iron) with graphite in nodular form; and (c) ferritic malleable iron. This cast iron solidi?ed as white cast iron, with the carbon present as cementite (Fe 3 C), and was heat treated to graphitize the carbon. (a) (b) (c)Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Continuous-Casting FIGURE 5.15 (a) The continuous-casting process for steel. Note that the platform is about 20 m (65 ft) above ground level. Source: American Foundrymen's Society. (b) Continuous strip casting of nonferrous metal strip. Source: Courtesy of Hazelett Strip-Casting Corp. Electric furnace Tundish Argon X-ray receiver (controls pouring rate) X-ray transmitter Molten metal Solidified metal Oil Cooling water Platform; 20 m (701 ft) above ground level Air gap Catch basin Pinch rolls Oxygen lance (for cutting) Starting dummy Tundish Top belt (carbon steel) High-velocity cooling water jets Back-up rolls Bottom belt Water gutters Nip pulley Synchronized pinch rolls Tension pulley Edge dam blocks Water nozzle (a) (b)Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Sand Casting FIGURE 5.16 Schematic illustration of the sequence of operations in sand casting. (a) A mechanical drawing of the part, used to create patterns. (b-c) Patterns mounted on plates equipped with pins for alignment. Note the presence of core prints designed to hold the core in place. (d-e) Core boxes produce core halves, which are pasted together. The cores will be used to produce the hollow area of the part shown in (a). (f) The cope half of the mold is assembled by securing the cope pattern plate to the ?ask with aligning pins, and attaching inserts to form the sprue and risers. (g) The ?ask is rammed with sand and the plate and inserts are removed. (h) The drag half is produced in a similar manner. (j) The core is set in place within the drag cavity. (k) The mold is closed by placing the cope on top of the drag and securing the assembly with pins. (l) After the metal solidi?es, the casting is removed from the mold. (m) The sprue and risers are cut off and recycled, and the casting is cleaned, inspected, and heat treated (when necessary). Source: Courtesy of Steel Founders' Society of America. Cope ready for sand Cope after ramming with sand and removing pattern, sprue, and risers Drag ready for sand Drag after removing pattern Core halves pasted together (e) (f) (g) (h) (i) Sprue Risers Flask Drag with core set in place (j) Cope and drag assembled and ready for pouring (k) Cope Drag Closing pins Casting as removed from mold; heat treated (l) Casting ready for shipment (m) (a) Mechanical drawing of part Core boxes Cope pattern plate Drag pattern plate (d) (b) (c) Core prints Gate Core printsManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Shell-Molding Process FIGURE 5.17 Schematic illustration of the shell-molding process, also called the dump-box technique. Pattern Coated sand Dump box 1. Pattern rotated and clamped to dump box Shell Excess coated sand 4. Pattern and shell removed from dump box Coated sand 3. Pattern and dump box in position for the investment Investment Pattern Coated sand 2. Pattern and dump box rotated Adhesive Clamps 5. Mold halves joined together Flask Sand or metal beads Shells 6. Mold placed in flask and metal pouredManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Caramic Mold Manufacture FIGURE 5.18 Sequence of operations in making a ceramic mold. 3. Burn-off 2. Stripping green mold 1. Pouring slurry Flask Green mold Pattern Plate Ceramic slurry Pattern Transfer bowl Flask Torch MoldManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Vacuum-Casting Process FIGURE 5.19 Schematic illustration of the vacuum-casting process. Note that the mold has a bottom gate. (a) before and (b) after immersion of the mold into the molten metal. Source: After R. Blackburn. Mold (a) (b) Induction furnace Vacuum Casting Molten metal GateManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Evaporative Pattern Casting FIGURE 5.20 Schematic illustration of the expendable-pattern casting process, also known as lost- foam or evaporative-pattern casting. 1. Pattern molding 4. Compacted in sand 5. Casting 6. Shakeout 2. Cluster assembly 3. Coating Cluster PartsManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Investment Casting FIGURE 5.21 Schematic illustration of investment casting (lost wax process). Castings by this method can be made with very ?ne detail and from a variety of metals. Source: Steel Founders' Society of America. 9. Shakeout 8. Pouring 7. Pattern meltout 6. Completed mold Casting 10. Pattern Molten metal Autoclaved Molten wax or plastic Heat Heat 1. Injection wax or plastic pattern 4. Slurry coating 2. Ejecting pattern 5. Stucco coating 3. Pattern assembly (tree) Wax pattern Mold to make patternManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Rotor Microstructure FIGURE 5.22 Microstructure of a rotor that has been investment cast (top) and conventionally cast (bottom). Source: Advanced Materials and Processes, October 1990, p. 25. ASM International. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Pressure & Hot-Chamber Die Casting FIGURE 5.23 The pressure casting process, utilizing graphite molds for the production of steel railroad wheels. Source: Grif?n Wheel Division of Amsted Industries Incorporated. Airtight chamber Ladle Refractory tube Molten metal Air pressure Railroad wheel Graphite mold FIGURE 5.24 Schematic illustration of the hot-chamber die-casting process. Gooseneck Nozzle Die cavity Hydraulic shot cylinder Plunger rod Plunger Molten metal Pot Ejector die Cover die FurnaceManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Cold-Chamber Die Casting FIGURE 5.25 Schematic illustration of the cold- chamber die-casting process. These machines are large compared to the size of the casting, because high forces are required to keep the two halves of the die closed under pressure. Shot cylinder Metal sleeve Cover disc Closing cylinder Ejector box Ejector platen (Moves) Ejector die half Hydraulic cylinder Shot sleeve Ejector box Ladle Stationary die half Plunger rod Stationary platen Cavity Pouring hole Plunger Plunger rodManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Properties of Die-Casting Alloys Ultimate Elonga- Tensile Yield tion Strength Strength in 50 mm Alloy (MPa) (MPa) (%) Applications Aluminum 380 320 160 2.5 Appliances, automotive (3.5 Cu-8.5 Si) components, electrical motor frames and housings, engine blocks. Aluminum 13 300 150 2.5 Complex shapes with thin (12 Si) walls, parts requiring strength at elevated temperatures Brass 858 (60 Cu) 380 200 15 Plumbing ?xtures, lock hard- ware, bushings, ornamental cast- ings Magnesium 230 160 3 Power tools, automotive AZ91B (9 Al - 0.7 Zn) parts, sporting goods Zinc No. 3 (4 Al) 280 — 10 Automotive parts, o?ce equip- ment, household utensils, build- ing hardware, toys Zinc No. 5 (4 Al - 1 Cu) 320 — 7 Appliances, automotive parts, building hardware, business equipment Source: The North American Die Casting Association TABLE 5.6 Properties and typical applications of common die-casting alloys.Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Centrifugal Casting FIGURE 5.26 Schematic illustration of the centrifugal casting process. Pipes, cylinder liners, and similarly shaped hollow parts can be cast by this process. Free roller Drive roller Mold (a) (b) Drive shaft Spout Rollers Ladle Molten metal MoldManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Semicentrifugal Casting FIGURE 5.27 (a) Schematic illustration of the semicentrifugal casting process. Wheels with spokes can be cast by this process. (b) Schematic illustration of casting by centrifuging. The molds are placed at the periphery of the machine, and the molten metal is forced into the molds by centrifugal forces. (a) (b) Mold Molten metal Casting Flasks Holding fixture Drag Revolving table Casting Pouring basin and gate CopeManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Squeeze-Casting FIGURE 5.28 Sequence of operations in the squeeze-casting process. This process combines the advantages of casting and forging. 1. Melt metal 2. Pour molten metal into die 3. Close die and apply pressure 4. Eject squeeze casting, charge melt stock, repeat cycle Die Ejector pin Finished casting CavityManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 T urbine Blade Casting FIGURE 5.29 Methods of casting turbine blades: (a) directional solidi?cation; (b) method to produce a single-crystal blade; and (c) a single-crystal blade with the constriction portion still attached. Source: (a) and (b) After B.H. Kear, (c) Courtesy of ASM International. (c) (a) (b) Radiant heat Columnar crystals Constriction Chill plate Columnar crystals Heat baffles Radiant heat Chill plateManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Crystal Growing FIGURE 5.30 T wo methods of crystal growing: (a) crystal pulling (Czochralski process) and (b) ?oating-zone method. Crystal growing is especially important in the semiconductor industry. (c) A single-crystal silicon ingot produced by the Czochralski process. Source: Courtesy of Intel Corp. (c) (a) (b) ~1 rev/s 10 µm/s Liquid Seed 20 µm/s Induction coil Single crystal Polycrystalline feedManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Melt-Spinning Process FIGURE 5.31 (a) Schematic illustration of the melt-spinning process to produce thin strips of amorphous metal. (b) Photograph of nickel-alloy production through melt-spinning. Source: Courtesy of Siemens AG. (b) (a) Crucible Induction coil Melt Strip Gas Copper diskManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Austenite-Pearlite Transformation FIGURE 5.32 (a) Austenite to pearlite transformation of iron-carbon alloys as a function of time and temperature. (b) Isothermal transformation diagram obtained from (a) for a transformation temperature of 675°C (1247°F). (c) Microstructures obtained for a eutectoid iron- carbon alloy as a function of cooling rate. Source: Courtest of ASM International. (a) 25 75 50 0 100 75 25 50 100 0 Austenite (%) Pearlite (%) Time (s) 600°C 650° 675° 1 10 10 2 10 3 (b) (c) 50 0 100 Percent of austenite transformed to pearlite Temperature (°C) Austenite (%) °F 50 100 0 600 400 500 700 800 1000 1200 1400 Time (s) 50% Completion curve Pearlite Completion curve (~100% pearlite) Eutectoid temperature Austenite (unstable) Begin curve (~0% pearlite) Transformation temperature 675°C Transformation begins 1 10 10 3 10 4 10 5 Transformation ends 1 10 10 2 10 3 10 4 10 5 Austenite (stable) 10 2 Time (s) Temperature (°C) 200 100 0 200 400 600 800 1000 1200 1400 300 400 500 35°C/s 140°C/s 600 700 800 Eutectoid temperature M (start) Critical cooling rate Time (s) 1 10 10 2 10 -1 10 3 10 4 10 5 °F Pearlite Martensite Martensite + pearlite Austenite pearlite Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Phase Diagram for Aluminum-Copper FIGURE 5.33 (a) Phase diagram for the aluminum-copper alloy system. (b) Various microstructures obtained during the age-hardening process. X Temperature X—solid solution XA—quenched, solid solution retained AB—age-hardened, precipitation starts (submicroscopic) AC—over-aging, precipitate agglomerates 100 95 90 Aluminum (Al) 0 5 10 Copper (Cu) 70 400 900 1100 Liquid + liquid 20 200 500 600 700 (b) (a) 1300 Composition (% by weight) Temperature (°C) °F A B C Time + !Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Outline of Heat Treating TABLE 5.7 Outline of heat treatment processes for surface hardening. Element Metals added to General Typical Process hardened surface Procedure characteristics applications Carburizing Low-carbon steel (0.2% C), alloy steels (0.08-0.2% C) C Heat steel at 870-950 ? (1600-1750 ? F) in an at- mosphere of carboaceous gases (gas carburizing) or carbon-containing solids (pack carburizing). Then quench. A hard, high-carbon surface is produced. Hardness 55- 65 HRC. Case depth <0.5- 1.5 mm (<0.020 to 0.060 in.). Some distortion of part dur- ing heat treatment. Gears, cams, shafts, bearings, piston pins, sprockets, clutch plates Carbonitriding Low-carbon steel C and N Heat steel at 700-800 ? C (1300-1600 ? F) in an atmo- sphere of carbonaceous gas and ammonia. Then quench in oil. Surface hardness 55-62 HRC. Case depth 0.07-0.5 mm (0.003-0.020 in.). Less distor- tion than in carburizing. Bolts, nuts, gears. Cyaniding Low-carbon steel (0.2% C), alloy steels (0.08-0.2% C) C and N Heat steel at 760-845 ? C (1400-1550 ? F) in a molten bath of solutions of cyanide (e.g., 30% sodium cyanide) and other salts. Surface hardness up to 65 HRC. Case depth 0.025-0.25 mm (0.001-0.010 in.). Some distortion. Bolts, nuts, screws, small gears. Nitriding Steels (1% Al, 1.5% Cr, 0.3% Mo), alloy steels (Cr, Mo), stain- less steels, high- speed steels N Heat steel at 500-600 ? C (925- 1100 ? F) in an atmosphere of ammonia gas or mixtures of molten cyanide salts. No fur- ther treatment. Surface hardness up to 1100 HV. Case depth 0.1-0.6 mm (0.005-0.030 in.) and 0.02- 0.07 mm (0.001-0.003 in.) for high speed steel. Geards, shafts, sprockets, valves, cutters, boring bars Boronizing Steels B Part is heated using boron- containinggasorsolidincon- tact with part. Extremely hard and wear- resistance surface. Case depth 0.025-0.075 mm (0.001-0.003 in.). Tool and die steels. Flame hardening Medium-carbon steels, cast irons None Surface is heated with an oxyacetylene torch, then quenched with water spray or other quenching methods. Surface hardness 50-60 HRC. Case depth 0.7-6 mm (0.030- 0.25 in.). Little distortion. Axles, crankshafts, piston rods, lathe beds, and centers. Induction hardening Same as above None Metal part is placed in cop- per induction coils and is heatedbyhighfrequencycur- rent, then quenched Same as above Same as aboveManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Heat Treatment T emperature Ranges FIGURE 5.34 T emperature ranges for heat treating plain-carbon steels, as indicated on the iron-iron carbide phase diagram. 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Temperature (° C ) 600 700 800 900 1000 1200 1400 1600 1800 Normalizing Full annealing A cm Spheroidizing 738°C A 3 A 1 Composition (% C) °FManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Casting Processes Comparison TABLE 5.8 Casting Processes, and their Advantages and Limitations. Process Advantages Limitations Sand Almost any metal is cast; no limit to size, shape or weight; low tooling cost. Some ?nishing required; somewhat coarse ?nish; wide tolerances. Shell mold Good dimensional accuracy and sur- face ?nish; high production rate. Part size limited; expensive patterns and equipment required. Expendable pattern Most metals cast with no limit to size; complex shapes Patterns have low strength and can be costly for low quantities. Plaster mold Intricate shapes; good dimensional accuracy and ?nish; low porosity. Limited to nonferrous metals; limited size and volume of production; mold making time relatively long. Ceramic mold Intricate shapes; close tolerance parts; good surface ?nish. Limited size. Investment Intricate shapes; excellent surface ?n- ish and accuracy; almost any metal cast. Part size limited; expensive patterns, molds, and labor. Permanent mold Good surface ?nish and dimensional accuracy; low porosity; high produc- tion rate. High mold cost; limited shape and in- tricacy; not suitable for high-melting- point metals. Die Excellent dimensional accuracy and surface ?nish; high production rate. Die cost is high; part size limited; usu- ally limited to nonferrous metals; long lead time. Centrifugal Large cylindrical parts with good quality; high production rate. Equipment is expensive; part shape limited.Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Chills FIGURE 5.35 Various types of (a) internal and (b) external chills (dark areas at corners), used in castings to eliminate porosity caused by shrinkage. Chills are placed in regions where there is a larger volume of metal, as shown in (c). (a) (b) (c) Porosity Chill Casting Boss Chill Sand Casting Chill SandManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Hydrogen Solubility in Aluminum FIGURE 5.36 Solubility of hydrogen in aluminum. Note the sharp decrease in solubility as the molten metal begins to solidify. Hydrogen solubility Fusion Solid Liquid Melting pointManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Elimination of Porosity in Castings FIGURE 5.37 (a) Suggested design modi?cations to avoid defects in castings. Note that sharp corners are avoided to reduce stress concentrations; (b, c, d) examples of designs showing the importance of maintaining uniform cross-sections in castings to avoid hot spots and shrinkage cavities. (a) Poor Good (b) (c) (d) Shrinkage cavity Poor Poor Good GoodManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Design Modi?cations FIGURE 5.38 Suggested design modi?cations to avoid defects in castings. Source: Courtesy of The North American Die Casting Association. Use radii or fillets to avoid corners and provide uniform cross-section. Wall sections should be uniform. Sloping bosses can be designed for straight die parting to simplify die design. Ribs and/or fillets improve bosses. Side cores can be eliminated with this hole design. Deep cavities should be on one side of the casting where possible. Poor Good Poor Good Poor Good Poor Good Poor Good Poor Good Core in cover half Core in ejector halfManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Economics of Casting FIGURE 5.39 Economic comparison of making a part by two different casting processes. Note that because of the high cost of equipment, die casting is economical mainly for large production runs. Source: The North American Die Casting Association. Cost per piece (relative) 8 7 6 5 4 3 2 1 0 10 0 10 1 10 2 10 3 10 4 10 5 10 6 Number of pieces Die cast Sand cast Permanent-mold casting Plaster castManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Lost-Foam Casting of Engine Blocks FIGURE 5.40 (a) An engine block for a 60-hp 3-cylinder marine engine, produced by the lost-foam casting process; (b) a robot pouring molten aluminum into a ?ask containing a polystyrene pattern. In the pressurized lost-foam process, the ?ask is then pressurized to 150 psi (1000 kPa). Source: Courtesy of Mercury Marine (a) (b)