Döküm sunu kalpakjian kütle pşv (ingilizce ) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Bulk Deformation Processes Process General Characteristics Forging Production of discrete parts with a set of dies; some ?nishing operations usually necessary; similar parts can be made by casting and powder-metallurgy techniques; usually performed at elevated temperatures; dies and equipment costs are high; moderate to high labor costs; moderate to high operator skill. Rolling Flat Production of ?at plate, sheet, and foil at high speeds, and with good surface ?nish, especially in cold rolling; requires very high capital investment; low to moderate labor cost. Shape Production of various structural shapes, such as I-beams and rails, at high speeds; includes thread and ring rolling; requires shaped rolls and expensive equipment; low to moderate labor cost; moderate operator skill. Extrusion Production of long lengths of solid or hollow products with constant cross-sections, usually performed at elevated temperatures; product is then cut to desired lengths; can be competitive with roll forming; cold extrusion has similarities to forging and is used to make discrete products; moderate to high die and equipment cost; low to moderate labor cost; low to moderate operator skill. Drawing Production of long rod, wire, and tubing, with round or various cross-sections; smaller cross-sections than extrusions; good surface ?nish; low to moderate die, equipment and labor costs; low to moderate operator skill. Swaging Radial forging of discrete or long parts with various internal and external shapes; generally carried out at room temperature; low to moderate operator skill. TABLE 6.1 General characteristics of bulk deformation processes.Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Upsetting Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 FIGURE 6.1 (a) Ideal deformation of a solid cylindrical specimen compressed between ?at frictionless dies (platens), an operation known as upsetting. (b) Deformation in upsetting with friction at the die-workpiece interfaces. Note barrelling of the billet caused by friction. (a) d 2 (b) Workpiece Die Die Friction forces d 0 d 1 h o h 1 h 2 Barreling h 2 d 0 h o h 1Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Grain Flow FIGURE 6.3 Schematic illustration of grid deformation in upsetting: (a) original grid pattern; (b) after deformation, without friction; (c) after deformation, with friction. Such deformation patterns can be used to calculate the strains within a deforming body. (a) (b) (c) FIGURE 6.2 Grain ?ow lines in upsetting a solid, steel cylindrical specimen at elevated temperatures between two ?at cool dies. Note the highly inhomogeneous deformation and barreling, and the difference in shape of the bottom and top sections of the specimen. The latter results from the hot specimen resting on the lower die before deformation proceeds. The lower portion of the specimen began to cool, thus exhibiting higher strength and hence deforming less than the top surface. Source: After J.A. Schey.Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Slab Analysis of Forging dx x a (a) (b) ! y ! x + d! x ! z ! z = ! x + ! y 2 (c) h 1 ! y ! y ! y µ! y µ! y ! x ! x ! x FIGURE 6.1 Stresses on an element in plane-strain compression (forging) between flat dies with fric- tion. The horizontal stress x is assumed to be uniformly distributed along the height h of the ele- ment. Identifying the stresses on an element (slab) is the first step in the slab method of analysis of metalworking processes. (? x +d? x )h+2µ? y dx-? y h =0 ? x =? y -Y " =Y " ! e 2µ(a-x)/h -1 " From equilibrium: Resulting die pressure prediction:Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Die Pressure FIGURE 6.5 Distribution of die pressure, in dimensionless form of p/Y’, in plane-strain compression with sliding friction. Note that the pressure at the left and right boundaries is equal to the yield stress of the material in plane strain, Y’. Sliding friction means that the frictional stress is directly proportional to the normal stress. Workpiece a x h p/Y! e 2 a/h 1 0 FIGURE 6.6 Die pressure distribution in compressing a rectangular workpiece with sliding friction and under conditions of plane stress, using the distortion-energy criterion. Note that the stress at the corners is equal to the uniaxial yield stress, Y, of the material. Y Pressure distribution Workpiece FIGURE 6.7 Increase in die- workpiece contact area of an originally rectangular specimen (viewed from the top) compressed between ?at dies and with friction. Note that the length of the specimen (horizontal dimension) has increased proportionately less than its width (vertical dimension). Likewise, a specimen originally in the shape of a cube acquires the shape of a pancake after deformation with friction. Original contact area After first reduction After second reductionManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Slab Method for Cylindrical Workpiece FIGURE 6.8 Stresses on an element in forging of a solid cylindrical workpiece between ?at dies and with friction. Compare this ?gure and the stresses involved with Fig. 6.4. x r dx (a) (b) h ! r ! z µ! z ! z ! " ! " ! r 1 d! r d" d" 2 d" 2 Results: Average pressure: Forging force: p =Ye 2µ(r-x)/h . p av !Y ! 1+ 2µr 3h " . F = (p av ) ! ? r 2 "Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Die Pressure FIGURE 6.9 Ratio of average die pressure to yield stress as a function of friction and aspect ratio of the specimen: (a) plane- strain compression; and (b) compression of a solid cylindrical specimen. Note that the yield stress in (b) is Y, and not Y’ as it is in the plane-strain compression shown in (a). Source: After J.F .W. Bishop. Sticking = 0.2 0.1 0.05 0 12 10 8 6 4 2 0 Y! p av (a) 0 10 20 30 40 50 60 70 80 Y p av 2r h 2a h 0 10 20 30 40 50 60 70 80 12 10 8 6 4 2 0 (b) Sticking = 0.3 0.2 0.15 0.1 0.05 0.02 0Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Pressure with Sticking Condition FIGURE 6.10 Distribution of dimensionless die pressure, p/Y’, in compressing a rectangular specimen in plane strain and under sticking conditions. Sticking means that the frictional (shear) stress at the interface has reached the shear yield stress of the material. Note that the pressure at the edges is the uniaxial yield stress of the material in plane strain, Y’. Workpiece x p/Y! 1 0 h (1 + a/h) a Results for sticking friction in plane strain: Results for sticking friction with cylinder: p =Y ! ! 1+ a-x h " p =Y ! 1+ r-x h "Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Finite Element Analysis FIGURE 6.11 Deformation of a blank during forging as predicted by the software program DEFORM based on the ?nite-element method of analysis. Source: Courtesy Scienti?c Forming T echnologies Corporation. (a) (b) (c) (d) Upper die Lower die WorkpieceManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Die Pressure and Aspect Ratio FIGURE 6.12 Die pressure required in various metalworking operations and under frictionless plane-strain conditions, as obtained by the slip-line analysis. Note that the magnitude of the die-workpiece contact area is an important factor in determining pressures. Source: After W.A. Backofen. 0 1 3 2 4 5 6 7 8 9 10 0 1 2 3 h L = h/L p/Y! = 1 + /2 p Y! Sheet and strip rolling Wire and rod drawing Extrusion Breakdown rolling Heavy forging Piercing Hardness testingManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Plane Strain Examples FIGURE 6.13 Examples of plastic deformation processes in plane strain, showing the h/L ratio. (a) Indenting with ?at dies, an operation similar to the cogging process, as shown in Fig. 6.19. (b) Drawing or extrusion of a strip with a wedge-shaped die, as described in Sections 6.4 and 6.5. (c) Ironing; see also 7.53. (d) Rolling, described in Section 6.3. L h (a) D = L h d 0 or h o ! d 1 or h 1 h L ! h o h 1 (c) (d) L R h 1 h o (b) h D = L hManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Impression Die Forging FIGURE 6.14 Schematic illustrations of stages in impression- die forging. Note the formation of a ?ash, or excess material that subsequently has to be trimmed off. (a) (b) (c) Die Blank Die (d) Flash Simple shapes, without ?ash 3-5 Simple shapes, with ?ash 5-8 Complex shapes, with ?ash 8-12 TABLE 6.2 Range of K p values in Eq. (6.22) for impression-die forging. F=K p Y f A Forging force:Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Load-Stroke Curve FIGURE 6.15 Typical load-stroke curve for impression-die forging. Note the sharp increase in load when the ?ash begins to form. Source: After T. Altan. Die motion Workpiece C L Die (a) Upsetting Filling End Flash Cavity filled completely Dies closed Forging energy Flash begins to form Dies contact workpiece Forging completed Forging stroke Forging load (b) LandManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Orbital-Forging FIGURE 6.16 Schematic illustration of the orbital-forging process. Note that the die is in contact with only a portion of the workpiece surface at a time. Also called rotary forging, swing forging, and rocking-die forging, this process can be used for forming individual parts such as bevel gears, wheels, and bearing rings. (a) (b) 1 2 3 4 5 Orbital path Upper die Blank Orbital Planetary Straight line Spiral Forged workpiece EjectorManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Heading & Piercing FIGURE 6.18 Examples of piercing operations. Head formed in die Head formed in punch Kickout pin Die Blank Punch FIGURE 6.17 Forming the heads of fasteners, such as bolts and rivets, by the heading process. Workpiece (a) (b) Die PunchManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Open-Die Forging FIGURE 6.19 (a) Schematic illustration of a cogging operation on a rectangular bar. Blacksmiths use a similar procedure to reduce the thickness of parts in small increments by heating the workpiece and hammering it numerous times along the length of the part. (b) Reducing the diameter of a bar by open-die forging; note the movements of the die and the workpiece. (c) The thickness of a ring being reduced by open-die forging. (a) Workpiece Workpiece (b) (c) Workpiece Die Die Die Die Die Die Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Roll Forging FIGURE 6.21 T wo illustrations of roll forging (cross-rolling) operations. Tapered leaf springs and knives can be made by this process using specially designed rolls. Source: After J. Holub. Workpiece Shaped roll Workpiece (b) (a)Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Production of Ball Bearings FIGURE 6.21 (a) Production of steel balls for bearings by skew rolling. (b) Production of steel balls by upsetting of a short cylindrical blank; note the formation of ?ash. The balls are subsequently ground and polished to be used as ball bearings and similar components. Semi-finished ball Stock (b) (a) Die Ejector Blank BallManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Forging Defects FIGURE 6.22 Stages in lap formation in a part during forging, due to buckling of the web. Web thickness should be increased to avoid this problem. 1. Blocked forging Die Die 2. Begin finishing Rib Web 3. Web buckles Laps 4. Laps in finished forging FIGURE 6.23 Stages in internal defect formation in a forging because of an oversized billet. The die cavities are ?lled prematurely, and the material at the center of the part ?ows radially outward and past the ?lled regions as deformation continues. 2. Die cavities are being filled 1. Forging begins 3. Cracks develop in ribs 4. Cracks propagate through ribsManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Effect of Radius FIGURE 6.24 Effect of ?llet radius on defect formation in forging. Note that small ?llets (right side of the drawings) lead to defects. Source: Aluminum Company of America. Top die Large fillets Bottom die Forging stock Small fillets 1. Metal flow follows smooth curve Metal does not follow sharp corner 2. Flow into die fails to follow sharp corner 3. Metal reaches bottom of cavity before filling section Metal fills entire width of section 4. Voids where metal flow folds back on itself Cold shuts Smooth flow 6. 5.Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Forging Dies FIGURE 6.26 Standard terminology for various features of a typical forging die. External and internal draft angles Flash Parting line Land Rib Web Fillet Corner Trim line Parting line Gutter FIGURE 6.25 Stages in forging a connecting rod for an internal combustion engine. Note the amount of ?ash developed, which is important in properly ?lling die cavities. (a) Edging Trimming Blank (bar stock) Blocking Finishing 1. 2. 3. 4. 5.Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Forging T emperatures Metal ? C ? F Aluminum alloys 400-450 750-850 Copper alloys 625-950 1150-1750 Nickel alloys 870-1230 1600-2250 Alloy steels 925-1260 1700-2300 Titanium alloys 750-795 1400-1800 Refractory alloys 975-1650 1800-3000 TABLE 6.3 Forging temperature ranges for various metals. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Metalworking Equipment FIGURE 6.27 Schematic illustration of various types of presses used in metalworking. The choice of a press is an important consideration in the overall operation and productivity. Ram Crank Ram Fluid Hydraulic Ram Knucklejoint Flywheel Friction drive Screw Ram Screw (a) (b) (c) (d)Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Rolling Operations FIGURE 6.28 Schematic outline of various ?at-rolling and shape-rolling operations. Source: American Iron and Steel Institute. Continuous casting or ingots Slab Billet Bloom Hot strip Pickling and oiling Cold strip Skelp Plate Welded pipe Steel plates Hot-rolled bars Cold-drawn bars Wire and wire products Rods Tube rounds Seamless pipe Rails Structural shapesManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Grain Structure in Hot Rolling FIGURE 6.29 Changes in the grain structure of metals during hot rolling. This is an effective method to reduce grain size and re?ne the microstructure in metals, resulting in improved strength and good ductility. In this process cast structures of ingots or continuous castings are converted to a wrought structure. (a) (b) Deformed elongated grains New grains forming Wrought product with small, uniform grains Recrystallization complete New grains growing Ingot with nonuniform grains Hot rolling Wrought product with large grains Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Mechanics of Rolling FIGURE 6.30 Schematic illustration of the ?at-rolling process. (Note that the top roll has been removed for clarity.) Workpiece V 0 V f V r h o R h f Roll L (Top roll removed) w o w f FIGURE 6.31 Relative velocity distribution between roll and strip surfaces. The arrows represent the frictional forces acting along the strip-roll interfaces. Note the difference in their direction in the left and right regions. V f V r ! Roll V 0 V 0 V r V f Workpiece Forward slip: Forwardslip= V f -V r V rManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Slab Method for Rolling FIGURE 6.32 Stresses acting on an element in rolling: (a) entry zone and (b) exit zone. h + dh h p p p p x + d x x (a) Entry zone p p p p x + d x x (b) Exit zone Entry zone pressure: Exit zone pressure: p =Y ! f h h 0 e µ(H 0 -H) p=Y ! f h h f e µH where H=2 ! R h f tan -1 "! R h f ? #Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Pressure Distribution in Rolling FIGURE 6.33 Pressure distribution in the roll gap as a function of the coef?cient of friction. Note that as friction increases, the neutral point shifts toward the entry. Without friction, the rolls will slip, and the neutral point shifts completely to the exit. (See also Table 4.1.) 0.15 0.1 0.075 Rolling direction Entry Exit 4 3 2 1 0 p Y! L =0.4 0.3 0.2 FIGURE 6.35 Pressure distribution as a function of front and back tension in rolling. Note the shifting of the neutral point and the reduction in the area under the curves (hence reduction in the roll force) as tensions increase. Rolling direction p Y 4 3 2 1 0 Entry Exit L 1 L 2 L 3 L Reduction = 50% 30 20 10 FIGURE 6.34 Pressure distribution in the roll gap as a function of reduction in thickness. Note the increase in the area under the curves with increasing reduction, thus increasing the roll force. p ! b ! b ! f ! f " # n 0 h o /2 h f /2 ! f ! bManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Roll Bending & Slab Spread FIGURE 6.36 (a) Bending of straight cylindrical rolls (exaggerated) because of the roll force. (b) Bending of rolls, ground with camber, that produce a sheet of uniform thickness during rolling. (b) Strip with uniform thickness Strip thicker at center Rolls (a) FIGURE 6.37 Increase in the width of a strip (spreading) during ?at rolling. Spreading can be similarly observed when dough is rolled on a ?at surface with a rolling pin. h f Side view Top view h o w o w f (b) (a) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Defects in Rolling FIGURE 6.38 Schematic illustration of some defects in ?at rolling: (a) wavy edges; (b) zipper cracks in the center of strip; (c) edge cracks; (d) alligatoring. Rolling direction (a) (b) (c) (d) FIGURE 6.39 The effect of roll radius on the type of residual stresses developed in ?at rolling: (a) small rolls and/or small reduction in thickness; and (b) large rolls and/ or large reduction in thickness. Sheet thickness Tension Compression Tension Compression (a) (b) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Roller Leveling FIGURE 6.40 Schematic illustrations of roller leveling to (a) ?atten rolled sheets and (b) straighten round rods. Leveling rolls (a) (b) Rod Rollers Sheet Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Roll Arrangements FIGURE 6.41 Schematic illustration of various roll arrangements: (a) two-high mill; (b) three-high mill; (c) four- high mill; (d) tandem rolling, with three stands; (e) planetary mill, (f) cluster (Sendzimir) mill. (f) (d) Support roll Cage Planetary rolls (e) (c) Screw or hydraulic mechanism Work rolls Back-up rolls Chocks Back-up rolls Housing (a) (b) Backing bearing Driven roll Driven roll Driven roll Bearing shaft Work roll Strip First intermediate roll Second intermediate roll Driven roll HousingManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Shape Rolling FIGURE 6.42 Stages in shape rolling of an H-section. Several other structural sections, such as channels and rails, also are rolled by this process. Stage 1 Stage 2 Blooming rolls Stage 3 Stage 4 Stage 5 Stage 6 Edging rolls Roughing horizontal and vertical rolls Intermediate horizontal and vertical rolls Edging rolls Finishing horizontal and vertical rollsManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Ring Rolling FIGURE 6.43 (a) Schematic illustration of a ring-rolling operation. Reducing the ring thickness results in an increase in its diameter. (b)-(d) Three examples of cross-sections that can be produced by ring rolling. (c) (a) Main roll (driven) Rounding roll Idler roll Workpiece Edging roll (b) (d) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Thread Rolling FIGURE 6.44 Thread-rolling processes: (a) and (b) reciprocating ?at dies and (c) two-roller dies; (d) thread-rolled parts, made economically and at high production rates. Source: (d) Courtesy of T esker Manufacturing Corp. Moving die Threaded part Stationary die Blank (c) (b) (a) (d) Work rest Moving cylindrical die Force Workpiece Stationary cylindrical dieManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Thread Microstructure FIGURE 6.45 (a) Schematic illustration of thread features; (b) grain-?ow lines in machined and (c) rolled threads. Note that unlike machined threads, which are cut through the grains of the metal, rolled threads follow the grains and because of the cold working involved, they are stronger. Machined thread Rolled thread (b) (c) (a) Diameter of bar Machined or rolled thread Minor diameter Major diameterManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Mannesmann Process FIGURE 6.46 (a) Cracks developed in a solid round bar due to secondary tensile stresses; (b) simulation of the rotary-tube-piercing process; and (c) the Mannesmann process (mill) for seamless tube making. The mandrel is held in place by a long rod, although techniques also have been developed whereby the mandrel remains in place without using a rod. Tube Solid rod Rolls Void initiation Tensile stress Mandrel (a) (b) (c) CavityManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Types of Extrusion FIGURE 6.47 Types of extrusion: (a) direct; (b) indirect; (c) hydrostatic; (d) impact. (a) (c) (d) Punch Extruded tube Container liner Container Billet Pressing stem Dummy block Extrusion Die Die backer Billet Dummy block Backing disc Container Die Extrusion Tool stem Container liner Container Die Extrusion Die backer Fluid Pressing stem SealsManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Extruded Products FIGURE 6.48 (a)-(c) Examples of extrusions and products made by sectioning them. Source: Kaiser Aluminum. (d) Examples of extruded cross-sections. Source: (d) Courtesy of Plymouth Extruded Shapes. (d) (a) (b) (c)Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Metal Flow in Extrusion FIGURE 6.49 Schematic illustration of three different types of metal ?ow in direct extrusion. The die angle in these illustrations is 90°. (a) (b) (c) Dead zone Dead zone Slab method prediction for extrusion pressure: Extrusion pressure with 45° dead-metal zone: p =Y ! 1+ tan? µ " # R µcot? -1 $ p =Y ! 1.7lnR+ 2L D o "Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Mechanics of Extrusion FIGURE 6.50 Schematic illustration of typical extrusion pressure as a function of ram travel: (a) direct extrusion and (b) indirect extrusion. The pressure in direct extrusion is higher because of frictional resistance at the container- billet interfaces, which decreases as the billet length decreases in the container. Ram travel Extrusion pressure a b FIGURE 6.52 Schematic illustration of the effect of temperature and ram speed on extrusion pressure. Note the similarity of this ?gure with Fig. 2.10. FIGURE 6.51 Schematic illustration of extrusion force as a function of die angle: (a) total force; (b) ideal force; (c) force required for redundant deformation; (d) force required to overcome friction. Note that there is a die angle where the total extrusion force is a minimum (optimum die angle). Extrusion pressure Extrusion speed (log) Increasing temperature a c d Die angle (!) Extrusion force bManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Extrusion Constant FIGURE 6.51 Extrusion constant, K e , for various materials as a function of temperature. Source: After P . Loewenstein. Temperature (°F) 1000 1500 2000 2500 0 20 40 60 80 400 600 800 1000 1200 1400 400 200 °C MPa Extrusion constant, k c (10 3 psi) Copper 70–30 Brass Molybdenum Chromium 1100 Aluminum Beryllium Cold-rolled steel p=K e lnRManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Cold Extrusion FIGURE 6.54 T wo examples of cold extrusion. Arrows indicate the direction of material ?ow. These parts may also be considered as forgings. Workpiece Die (a) (b) Punch PunchManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Impact Extrusion FIGURE 6.55 (a)-(b) Schematic illustration of the impact-extrusion process. The extruded parts are stripped using a stripper plate, as otherwise they may stick to the punch. (c) T wo examples of products made by impact extrusion. Collapsible tubes can be produced by impact extrusion, referred to as the Hooker process. (c) (a) (b) Stripper plate Die Blank Punch Die ClearanceManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Extrusion Pressure 2 4 7 12 16 12 8 4 0 900 600 300 0 0.7 1.5 2.0 2.5 Maximum extrusion pressure (psi x 10 4 ) MPa Extrusion ratio (R) True strain, ! a b c d FIGURE 6.56 Extrusion pressure as a function of the extrusion ratio for an alu- minum alloy. (a) Direct extrusion, =90°. (b) Hydrostatic extrusion, =45°. (c) Hydrostatic extrusion, =22.5°. (d) Ideal homogeneous deformation, calculated. Source: After H. Li, D. Pugh, and K. Ashcroft.Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Chevron Cracking Defect FIGURE 6.57 a) Chevron cracking in round steel bars during extrusion. Unless the part is inspected, such internal detects may remain undetected and possibly cause failure of the part in service. (b) Deformation zone in extrusion, showing rigid and plastic zones. Note that the plastic zones do not meet, leading to chevron cracking. The same observations are also made in drawing round bars through conical dies and drawing ?at sheet or plate through wedge-shaped dies. Source: After B. Avitzur. Die Rigid billet Central burst Rigid product V f V o Plastic deformation zone (a) (b)Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 T ube Extrusion FIGURE 6.58 Extrusion of a seamless tube. (a) Using an internal mandrel that moves independently of the ram. An alternative arrangement has the mandrel integral with the ram. (b) Using a spider die (see Fig. 6.59c) to produce seamless tubing. Tube Mandrel Container Ram Billet Billet Container Die Spider Mandrel Tube Ram Die Spider Mandrel (a) (b)Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Extrusion of Hollow Shapes FIGURE 6.59 (a) An extruded 6063-T6 aluminum ladder lock for aluminum extension ladders. This part is 8 mm (5/16 in.) thick and is sawed from the extrusion, as also shown in Fig. 6.48a. (b)-(d) Components of various types of dies for extruding intricate hollow shapes. Source: After K. Laue and H. Stenger (a) Welding chamber Spider Bridge Die Spider Porthole die Inlet ports Spider die Bridge die (b) (c) (d) DieManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Rod or Wire Drawing FIGURE 6.60 Variables in drawing round rod or wire. Die angle Die Wire or rod F A f A o Land ! Land Relief angle Workpiece !Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Slab Analysis for Drawing FIGURE 6.61 Stresses acting on an element in drawing of a solid cylindrical rod or wire through a converging conical die. p p µp µp ! x ! x + d! x (D + dD) D D 0 D f x " dx Drawing stress Inhomogeneity factor ? =1+0.12 ! h L " ? d =? ¯ Y ! 1+ µ ? " ln # A o A f $Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Drawing Stress FIGURE 6.63 The effect of reduction in cross-sectional area on the optimum die angle in drawing. Source: After J.G. Wistreich. Drawing stress Die pressure Entry Exit Without back tension With back tension (a) (b) FIGURE 6.62 Variation in the (a) drawing stress and (b) die contact pressure along the deformation zone. Note that as the drawing stress increases, the die pressure decreases (see also yield criteria, described in Section 2.11). Note the effect of back tension on the stress and pressure. Reduction (%) 45 40 35 30 25 20 15 10 5 Optimum die angle 0.8 0.6 0.4 0.2 0 d Y 0 4 8 12 16 Die angle, (deg)Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 T ube-Drawing Operations FIGURE 6.64 Examples of tube-drawing operations, with and without an internal mandrel. Note that a variety of diameters and wall thicknesses can be produced from the same tube stock (that has been produced by other processes, such as extrusion (a) (d) (c) (b) Die Stationary mandrel Die Floating mandrel Die Moving mandrel DieManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Residual Stresses in Drawing FIGURE 6.65 Residual stresses in cold-drawn 1045 carbon steel round rod: T = transverse direction, L = longitudinal direction and R = radial direction. Source: After E.S. Nachtman. Distance from center (in.) 0.75 0 0.75 60 40 20 0 220 240 260 280 Residual stress (psi x 10 3 ) Tension Compression 400 200 0 2200 2400 MPa Rod diameter mm 19 0 19 T L RManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Drawing Dies FIGURE 6.66 (a) T erminology for a typical die for drawing round rod or wire. (b) T ungsten-carbide die insert in a steel casing. Diamond dies, used in drawing thin wire, also are encased in a similar manner. (a) (b) Bell (angle or radius) Drawing direction Entering angle Approach angle Bearing surface (land) Back relief angle Tungsten-carbide insert (nib) Steel casing Drawing direction FIGURE 6.67 Schematic illustration of a typical wear pattern in a wire-drawing die. Diameter of incoming wire Unused Worn dieManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Rotary Swaging FIGURE 6.68 (a) Schematic illustration of the rotary-swaging process. (b) Forming internal pro?les in a tubular workpiece by swaging. (b) Cam Die Workpiece Mandrel (a) Planetary rollers Die Hammer Retainer DrivenManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Rotary Swaging FIGURE 6.70 (a) Typical cross-sections produced by swaging tubular blanks with a constant wall thickness on shaped mandrels. Ri?ing of small gun barrels also can be made by swaging. (b) Typical parts made by swaging. Source: Courtesy of J. Richard Industries. (a) Die Tube Mandrel (b) FIGURE 6.69 Reduction of outer and inner diameters of tubes by swaging. (a) Free sinking without a mandrel. The ends of solid bars and wire are tapered (pointing) by this process in order to feed the material into the conical die. (b) Sinking on a mandrel. Coaxial tubes of different materials can also be swaged in one operation. (b) (a)Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Forming Econimics FIGURE 6.71 Typical unit cost (cost per piece) in forging. Note how the setup and the tooling costs per piece decrease as the number of pieces forged increases, if all pieces use the same die. 100 10 1000 10,000 1 1000 100 10 Number of pieces Material cost Total cost per piece Tooling cost Setup cost Cost per piece (relative) FIGURE 6.72 Relative unit costs of a small connecting rod made by various forging and casting processes. Note that, for large quantities, forging is more economical. Sand casting is the more economical process for fewer than about 20,000 pieces. 100 0.1 1000 10 100,000 100 Number of pieces Sand casting Permanent- mold casting Forging Investment casting Die casting 16 mm Relative cost per piece 1 10,000 73 mmManufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Case Study: Automobile Suspension Uprights FIGURE 6.73 The Lotus Elise Series 2 Sportscar. Source: Courtesy of Fox Valley Motorcars. Identi?cation Description Mass (kg) Cost ($) Aluminum extrusion, steel bracket, bushing and housing 2.105 85 Benchmark Forged steel 2.685 (+28%) 27.7 (-67%) Phase I Forged steel 2.493 (+18%) 30.8 (-64%) Phase II TABLE 6.4 Vertical suspension uprights in the Lotus Elise Series 2 automobile.