İmal Usulleri Casting ( ingilizce ) CASTING CASTING Chapters 10, 11, 12 Chapters 10, 11, 12 Group 7 Group 7 Members William Waller James Ball William Ramos Christmas Trieu Perry Barrow 2/22/06 What is Casting? What is Casting? Casting is a process where molten metal is poured into a patterned mold. The metal is allowed to solidify into a part and is removed from the mold to be manufactured. Three Important considerations: 1. How the metal cools and solidifies in the mold 2. How the molten metal flows into the mold cavity 3. How the mold influences the metal Solidification Of Metals Solidification Of Metals Pure Metals Vs Alloys Pure Metals Pure Metals have very defined melting/freezing points and solidifies at a specific temperature. Pure Metals Pure Metals have a more uniform “columnar grain” growth. Solidification of Metals Solidification of Metals (cont.) (cont.) a. a. Columnar grains of a Columnar grains of a pure metal pure metal b. b. cast structure of solid cast structure of solid- - solution alloy solution alloy c. c. Non Non- -columnar structure columnar structure Solidification Of Metals Solidification Of Metals (Cont.) (Cont.) Alloy solidification Alloy solidification begins at some temperature TL and is not completed until it reaches a temperature TS. In between TL and TS, coined the “Mushy Zone,” both liquid and solid exists. Here is where columnar columnar dendrites dendrites may form which contributes to detrimental factors. Effects of cooling rates Effects of cooling rates on Alloys varies. The faster the alloy cools the more columnar dendrites may form. The slower the rate, the less columnar dendrites. Solidification of Metals Solidification of Metals (Cont.) (Cont.) Illustration of alloy solidification and temperature Illustration of alloy solidification and temperature distribution. distribution. Fluid Flow Fluid Flow Fluid flow of molten metal is extremely important in Fluid flow of molten metal is extremely important in casting. Note how the liquid metal has to flow through casting. Note how the liquid metal has to flow through the system. the system. Fluid Flow ( Fluid Flow (continued) continued) Bernoulli’s Theorem Bernoulli’s Theorem Explains how the fluid behaves by relating pressure, velocity and elevation of the fluid at any location within the system. Mass Continuity Mass Continuity Explains that for an incompressible liquid in a mold with impermeable walls the volume rate of flow is the same at one location as it is at another location. Fluid Flow Fluid Flow (continued) (continued) Sprue Design Sprue Design A tapered design or a choke is used to insure that the fluid flow is sufficiently slowed to prevent aspiration. Flow Characteristics Flow Characteristics An important consideration of flow through a grate is how much turbulence the fluid experiences. Turbulence creates the formation of dross. The more that turbulence is eliminated and laminar flow increases the less dross is created. Fluid Flow Fluid Flow (continued) (continued) Turbulent flow Turbulent flow Laminar flow Laminar flow Fluidity of Molten Metal Fluidity of Molten Metal ? ?Viscosity: Viscosity: The higher the value of viscosity the lower the fluidity ? ?Surface Tension: Surface Tension: The higher the value of surface tension of the liquid metal reduces the fluidity. ? ?Inclusions: Inclusions: has adverse affects on fluidity. An analogy is like oil with sand particles in it. This would reduce the liquids fluidity. ? ?Solidification Pattern of the alloy: Solidification Pattern of the alloy: The manner in which solidification takes place influences fluidity. ? ?Mold Design: Mold Design: influences how the fluid travels through the mold. ? ?Mold Material and Its Surface Mold Material and Its Surface Characteristics: Characteristics: How the mold conducts heat and how rough its surface is influences fluidity. ? ?Degree of Superheat: Degree of Superheat: defined as the increment of temperature of an ally above its melting point, Superheat improves fluidity by delaying solidification. ? ?Rate of Pouring: Rate of Pouring: The slower the rate of pouring the lower the fluidity due to higher cooling rates when pouring is slow. Heat Transfer Heat Transfer Solidification Time Solidification Time explains how much time is explains how much time is required for an object to solidify depending on its required for an object to solidify depending on its volume and surface area. Depending on the volume and surface area. Depending on the solidification time, the cavities of the mold begin to solidification time, the cavities of the mold begin to form solidified metallic skin on it interior walls. Thus, form solidified metallic skin on it interior walls. Thus, the interior of the mold becomes smaller. the interior of the mold becomes smaller. Solidified skin on a steel casting. Heat Transfer Heat Transfer (continued) (continued) Shrinkage Shrinkage Due to thermal expansion, when a metal cools it tend to Due to thermal expansion, when a metal cools it tend to shrink in size. Three events of this phenomena can shrink in size. Three events of this phenomena can cause dimensional problems as well as cracking. cause dimensional problems as well as cracking. 1. 1. Contraction of the molten metal as it cools prior ro its Contraction of the molten metal as it cools prior ro its solidification. solidification. 2. 2. Contraction of the metal during phase change from liquid Contraction of the metal during phase change from liquid to solid. to solid. 3. 3. Contraction of the solidified metal as its temperature drops Contraction of the solidified metal as its temperature drops to ambient temperature. to ambient temperature. 10.6 10.6 Defects Defects A A- - Metallic Projections Metallic Projections: : fins, flash, or fins, flash, or projections projections B B- - Cavities Cavities- - consist of rounded/ rough consist of rounded/ rough internal/ external cavities including blowholes, internal/ external cavities including blowholes, pinholes, and porosity pinholes, and porosity C C- - Discontinuities Discontinuities- - cracks, cold or hot cracks, cold or hot tearing and cold shuts. tearing and cold shuts. D D- - Defective surface Defective surface- - surface folds, laps, surface folds, laps, and adhering sand layers and adhering sand layers. . 10.6 Defects 10.6 Defects E E- - Incomplete casting: Incomplete casting: premature solidification, insufficient premature solidification, insufficient volume of metal poured, pouring metal too slowly or molten volume of metal poured, pouring metal too slowly or molten being at too low a temperature. being at too low a temperature. F F- - Incorrect dimensions/shapes: Incorrect dimensions/shapes: improper shrinkage improper shrinkage allowance, pattern mounting error, deformed pattern or warping allowance, pattern mounting error, deformed pattern or warping G G- - Inclusions Inclusions- - generally nonmetallic. generally nonmetallic. Occurs during Occurs during melting, solidification, and molding. Regarded harmful b/c they melting, solidification, and molding. Regarded harmful b/c they act as stress raisers which reduces the strength in casting. act as stress raisers which reduces the strength in casting. Inclusions form during melting when molten metal reacts with Inclusions form during melting when molten metal reacts with oxygen or mold material. Chemical reactions in molten metal oxygen or mold material. Chemical reactions in molten metal may also produce inclusions. may also produce inclusions. 10.6.1 Porosity 10.6.1 Porosity - -Caused by shrinkage or gas or both. Caused by shrinkage or gas or both. - -Thin sections in casting solidify quicker than thicker regions Thin sections in casting solidify quicker than thicker regions RESULT: RESULT: Molten metal flows into thicker regions before proper Molten metal flows into thicker regions before proper solidification. Porous regions may develop at center b/c of solidification. Porous regions may develop at center b/c of contraction as the surfaces of thicker regions begin to solidify first. contraction as the surfaces of thicker regions begin to solidify first. (Think of a funnel in the middle of casting) (cavities) (Think of a funnel in the middle of casting) (cavities) Micro Porosity Micro Porosity- - when liquid solidifies and shrinks between dendrites and when liquid solidifies and shrinks between dendrites and dendrite branches. dendrite branches. Chapter 11 Chapter 11 Metal Casting Processes Metal Casting Processes ? ? Expendable & Permanent mold Expendable & Permanent mold processes processes ? ? Applications, advantages, and Applications, advantages, and limitations of common casting limitations of common casting ? ? Casting of single crystals Casting of single crystals ? ? Inspection techniques Inspection techniques ? ? Foundries and their Automation Foundries and their Automation 11.1 Introduction 11.1 Introduction Two trends on casting industry: Two trends on casting industry: - -Mechanization & Automation: led to significant changes in Mechanization & Automation: led to significant changes in equipment and labor. Advanced machine & automated equipment and labor. Advanced machine & automated process process- -control systems replace traditional casting methods. control systems replace traditional casting methods. - -Increasing demand for HIGH QUALITY CASTINGS Increasing demand for HIGH QUALITY CASTINGS with close dimensional tolerances. with close dimensional tolerances. 11.1 Introduction 11.1 Introduction Major Categories of Casting Practices: Major Categories of Casting Practices: 1. 1. Expendable Molds: Expendable Molds: After casting solidifies, After casting solidifies, mold broken up to remove casting mold broken up to remove casting 2. 2. Permanent Molds: Permanent Molds: Used repeatedly and Used repeatedly and designed so casting can be removed easily and designed so casting can be removed easily and mold used for next casting. mold used for next casting. 3. 3. Composite molds: Composite molds: Have expendable & Have expendable & permanent portions. Used in various casting permanent portions. Used in various casting processes: improve strength, cooling, and processes: improve strength, cooling, and economics of casting process economics of casting process 11.2 Expendable 11.2 Expendable- -Mold Casting Processes Mold Casting Processes 11.2.1 Sand Casting 11.2.1 Sand Casting Casting consists of: Casting consists of: A) Placing a pattern in sand to make imprint A) Placing a pattern in sand to make imprint B) Incorporate gating system B) Incorporate gating system C) Removing pattern and filling mold cavity with C) Removing pattern and filling mold cavity with molten metal molten metal D) Allow metal to solidify D) Allow metal to solidify E) Break away sand mold E) Break away sand mold F) Remove casting F) Remove casting Types of Sand Molds Types of Sand Molds 1) Green 1) Green- -Sand Molding Sand Molding- - mix of sand, clay & water. “Green” refers to moistness mix of sand, clay & water. “Green” refers to moistness and dampness of mold while metal is being poured. LEAST EXPENSIVE and sand and dampness of mold while metal is being poured. LEAST EXPENSIVE and sand easily recycled easily recycled Cold Setting Processes Cold Setting Processes- - bonding of mold w/o heat bonding of mold w/o heat 2) Cold 2) Cold- -Box Mold Box Mold- - Binders blended into sand to chemically strengthen grains. More Binders blended into sand to chemically strengthen grains. More Accurate but more Expensive than Green Accurate but more Expensive than Green- -Mold. Mold. 3) No Bake Mold 3) No Bake Mold- - liquid resin mixed w/ sand and mixture hardens. liquid resin mixed w/ sand and mixture hardens. Patterns Patterns - -used to mold sand mixture into shape of casting used to mold sand mixture into shape of casting - -b/c patterns are used repeatedly, strength & durability of b/c patterns are used repeatedly, strength & durability of materials must reflect # of castings that mold will materials must reflect # of castings that mold will produce. produce. Types of patterns: Types of patterns: - -One One- -piece: simpler shapes and low piece: simpler shapes and low quantity production; inexpensive quantity production; inexpensive - -Split: Split: two piece, complicated shapes two piece, complicated shapes - -Match Match- -plate: picture plate: picture Patterns Patterns Rapid Prototyping Machine Rapid Prototyping Machine- - can fabricate a pattern at a fraction of time can fabricate a pattern at a fraction of time and cost of machining a pattern. and cost of machining a pattern. *Pattern design is a critical aspect *Pattern design is a critical aspect of the total casting operation. of the total casting operation. Design must provide for Shrinkage, Design must provide for Shrinkage, Ease of Removal from mold by Ease of Removal from mold by taper or draft, & proper metal flow taper or draft, & proper metal flow into mold cavity. into mold cavity. Sand Molding Machines Sand Molding Machines Vertical Flaskless Vertical Flaskless Molding Molding- - Sandslingers Sandslingers- - Fill under high pressure steam. Used to fill large Fill under high pressure steam. Used to fill large flasks & operated by machine. High speeds cause sand to be flasks & operated by machine. High speeds cause sand to be placed & rammed appropriately placed & rammed appropriately Impact Molding Impact Molding- - compacted by controlled explosion or compacted by controlled explosion or instantaneous release of compressed gas. Molds contain uniform instantaneous release of compressed gas. Molds contain uniform strength and good permeability strength and good permeability Vaccum Molding Vaccum Molding Sand Casting Operation Sand Casting Operation Removal of Casting: Removal of Casting: 1)castings cleaned by blasting w/ steel shot 1)castings cleaned by blasting w/ steel shot 2)risers & gates cut off 2)risers & gates cut off 3)Castings cleaned electrochemically to remove surface oxides, 3)Castings cleaned electrochemically to remove surface oxides, may even be heat treated may even be heat treated Finishing Operations: Finishing Operations: involve machining, straightening, involve machining, straightening, forging with dies to obtain final dimensions forging with dies to obtain final dimensions Final Step: Final Step: Inspection to meet all design & quality control Inspection to meet all design & quality control requirements requirements 11.2.2 Shell Molding 11.2.2 Shell Molding - -Produces many types of castings w/ close dimensional Produces many types of castings w/ close dimensional tolerances & good surface finish @ low cost. tolerances & good surface finish @ low cost. - -Unless molds are properly vented, Unless molds are properly vented, trapped air & gas can cause serious trapped air & gas can cause serious problems in ferrous castings. problems in ferrous castings. *High Quality of finished casting *High Quality of finished casting reduces cleaning, machining, and reduces cleaning, machining, and other finishing costs significantly. other finishing costs significantly. Complex shapes Complex shapes - - produced with produced with less labor, and easily automated less labor, and easily automated Precision Casting Precision Casting 11.2.3 Plaster 11.2.3 Plaster- -mold casting mold casting 11.2.4 Ceramic 11.2.4 Ceramic- - mold casting mold casting 11.2.6 Investment Casting 11.2.6 Investment Casting High Dimensional Accuracy & Good Surface Finish 11.2.3 Plaster-Molding process 1) Made of Plaster of Paris (gypsum or calcium), talc, & silica flour 2) Mix w/ water: Mixture poured over pattern. 3) Plaster sets and is removed, the mold dried at high temps to remove moisture. 4) Mold halves assembled, preheated and molten metal is poured. *Gases evolved during solidification cannot escape, so molten metal is poured under a vacuum or under pressure. Low Thermal Conductivity allows casting to cool slowly, allowing a more uniform grain structure is obtained w/ less warpage 11.2.4 Ceramic Mold casting 11.2.4 Ceramic Mold casting - -Similar to plaster mold process EXCEPT it uses refractory Similar to plaster mold process EXCEPT it uses refractory metal materials suitable for HIGH TEMPS. metal materials suitable for HIGH TEMPS. High High- -temperature resistance of refractory molding materials temperature resistance of refractory molding materials allows for casting of high temp alloys, stainless steel, and allows for casting of high temp alloys, stainless steel, and tool steels. tool steels. *Expensive Process but castings have good dimensional *Expensive Process but castings have good dimensional accuracy and surface finish accuracy and surface finish 11.2.5 Evaporative Pattern Casting (lost 11.2.5 Evaporative Pattern Casting (lost- -foam) foam) - -Mold produced for every casting Mold produced for every casting (polystyrene pattern evaporates upon contact with molten metal) (polystyrene pattern evaporates upon contact with molten metal) *Polymers require considerable energy to degrade, so large thermal *Polymers require considerable energy to degrade, so large thermal gradients are present. The degradation products are vented into gradients are present. The degradation products are vented into the surrounding sand. the surrounding sand. Advantages: 1) Simple process: Design flexibility 2) Inexpensive flasks are satisfactory 3) Plastic is inexpensive; easily processed into complex shapes, sizes, and fine surface detail 4) Casting requires minimal finshing and cleaning 11.2.6 Investment Casting (lost 11.2.6 Investment Casting (lost- -wax process) wax process) - -Pattern made of wax then dipped repeatedly into a slurry of Pattern made of wax then dipped repeatedly into a slurry of refractory material and allowed to dry. refractory material and allowed to dry. - -Mold heated and held UPSIDE Mold heated and held UPSIDE- -DOWN to allow melt out of DOWN to allow melt out of wax. wax. *the wax can be recovered and reused *the wax can be recovered and reused Molten metal then is then poured. Molten metal then is then poured. TREE TREE- - A number of patterns joined to make one A number of patterns joined to make one mold mold 11.2.6 Investment Casting (lost 11.2.6 Investment Casting (lost- -wax process) wax process) - -Mold materials and labor costly Mold materials and labor costly - -Suitable for high Suitable for high- -melting point alloys with good surface finishes and close melting point alloys with good surface finishes and close dimensional tolerances; few or no finishing operations cut costs of casting dimensional tolerances; few or no finishing operations cut costs of casting Ceramic Ceramic- -Shell Investment Casting Shell Investment Casting - -Uses same type of wax pattern. The pattern is dipped into coarser Uses same type of wax pattern. The pattern is dipped into coarser- - grained silica to build up coatings and develop proper thickness so grained silica to build up coatings and develop proper thickness so pattern can withstand the thermal shock due to pouring pattern can withstand the thermal shock due to pouring - -rest of process similar to investment casting rest of process similar to investment casting - -Used for precision casting of steels and high Used for precision casting of steels and high- -temperature alloys. temperature alloys. Investment casting of an integrally cast rotor for a gas turbine. (a) Wax pattern assembly. (b) Ceramic shell around wax pattern. (c) Wax is melted out and the mold is filled, under a vacuum, with molten superalloy. (d) The cast rotor, produced to net or near-net shape. Permanent-Mold Casting ?Two halves of a mold are made from materials with high resistance to erosion and thermal fatigue (ex iron, steel, graphite) ?Part weight can range from .1 kg to 300 kg but typically weigh less than 25 kg ?Medium quality surface finish, porosity, shape complexity ?High dimensional accuracy ?Good to average cost for equipment and labor ?Can produce 5-50 parts/mold hour ?Typically requires 1000 parts before being used Permanent-Mold Casting Bronze mold dated about 1400 B.C. Permanent-Mold Casting Vacuum Casting ? ? Used for thin walled (0.75 mm) complex shapes with uniform Used for thin walled (0.75 mm) complex shapes with uniform properties ex gas properties ex gas- -turbine components from superalloys. Process turbine components from superalloys. Process uses slight vacuum (2/3 atm) also reduces porosity. Metal only uses slight vacuum (2/3 atm) also reduces porosity. Metal only about 55C above liquidus temperature. Automated, and about 55C above liquidus temperature. Automated, and production costs similar to green production costs similar to green- -sand casting. sand casting. ? ? CLA CLA – – metal melted in air, parts are made at a high volume metal melted in air, parts are made at a high volume and low cost and low cost ? ? CLV CLV - - Metal melted in vacuum, involve reactive metals such Metal melted in vacuum, involve reactive metals such as aluminum, titanium, zirconium, and hafnium as aluminum, titanium, zirconium, and hafnium Permanent-Mold Casting ? ? Slush casting Slush casting – – used for small production runs for used for small production runs for ornamental and decorative items and toys from low melting ornamental and decorative items and toys from low melting point metals (lead, zinc, and tin alloys) Similar operation used point metals (lead, zinc, and tin alloys) Similar operation used in making hollow chocolate shapes. in making hollow chocolate shapes. ? ? Pressure casting Pressure casting - - uses pressurized gas to force metal up uses pressurized gas to force metal up into the mold, pressure is maintained until metal has solidified into the mold, pressure is maintained until metal has solidified Permanent-Mold Casting Die Casting ? ? Product weight <0.01 to 50 kg Product weight <0.01 to 50 kg ? ? Good surface finish, low porosity, capable of Good surface finish, low porosity, capable of high complexity parts high complexity parts ? ? Excellent dimensional accuracy +/ Excellent dimensional accuracy +/- - 0.001 0.001 tolerance tolerance ? ? Takes several weeks before first product output Takes several weeks before first product output ? ? Produces 2 Produces 2- -200 parts/mold hour 200 parts/mold hour ? ? Requires approximately 10,000 parts for use Requires approximately 10,000 parts for use Permanent-Mold Casting Die Casting ? ? Hot chamber process Hot chamber process - - Uses a piston to trap molten metal Uses a piston to trap molten metal and forces it into die cavity thru gooseneck and nozzle. Used and forces it into die cavity thru gooseneck and nozzle. Used for low melting point alloys (zinc, magnesium, tin, and lead) for low melting point alloys (zinc, magnesium, tin, and lead) ? ? Cold Cold- -chamber process chamber process – – Same as hot chamber, except Same as hot chamber, except chamber not heated, used for high melting point alloys. chamber not heated, used for high melting point alloys. (aluminum, magnesium, and copper) (aluminum, magnesium, and copper) ? ? Die to part weight is about 1000 to 1 … i.e. a 2 kg part Die to part weight is about 1000 to 1 … i.e. a 2 kg part requires a 2000 kg die requires a 2000 kg die Permanent-Mold Casting Die Casting Permanent-Mold Casting Centrifugal Casting ? ? Used for hollow cylindrical parts like pipes, gun barrels, posts Used for hollow cylindrical parts like pipes, gun barrels, posts ? ? Due to differences in density, lighter elements collect in Due to differences in density, lighter elements collect in center, therefore properties of casting vary through its center, therefore properties of casting vary through its thickness. thickness. ? ? Results in forces upward of 150 g for thick Results in forces upward of 150 g for thick - - walled parts walled parts ? ? Can produce parts over 5000 kg, but takes months for first Can produce parts over 5000 kg, but takes months for first part is produced. part is produced. Permanent-Mold Casting Squeeze Casting ? ? Results in parts made to near Results in parts made to near- -net shape and fine surface net shape and fine surface detail for both ferrous and non ferrous material. detail for both ferrous and non ferrous material. ? ? Particularly good for overcoming feeding difficulties that arise Particularly good for overcoming feeding difficulties that arise from casting metals with a long freezing range. from casting metals with a long freezing range. Permanent-Mold Casting Semi-solid Metal forming ? ? Working at extremely high temperatures can reduce die life. Working at extremely high temperatures can reduce die life. ? ? When the metal enters the die it is a combination of both When the metal enters the die it is a combination of both solid and liquid. As the metal is agitated, it’s viscosity is solid and liquid. As the metal is agitated, it’s viscosity is lowered, this process is called lowered, this process is called thixoforming. thixoforming. ? ? Advantages Advantages ? ? Parts are homogenous with high strength Parts are homogenous with high strength ? ? Thin and thick parts are produced Thin and thick parts are produced ? ? Parts can subsequently be heat treated Parts can subsequently be heat treated ? ? Disadvantage Disadvantage ? ? Higher costs than die casting Higher costs than die casting Quality Assurance Inspections ? ? Controlling each stage during casting is important in Controlling each stage during casting is important in maintaining good quality. maintaining good quality. ? ? Nondestructive testing Nondestructive testing – – visual and optical visual and optical inspection of outer surface for defects, can also inspection of outer surface for defects, can also involve radiographic testing for vital components. involve radiographic testing for vital components. ? ? Destructive testing Destructive testing - - various specimens are various specimens are removed from various sections to test for strength., removed from various sections to test for strength., durability, porosity, and any other defects. durability, porosity, and any other defects. ? ? Pressure testing Pressure testing - - usually performed on cast usually performed on cast components such as pumps, valves, and pipes to components such as pumps, valves, and pipes to test for seal leakage. test for seal leakage. The melting practice is important because it affects the quality of the castings. When melting your metal stock in a furnace, you would add flux and other slag-forming constituents to refine your metal. The type of furnace you use also affects the quality of castings as well. •Electric arc: found in many foundries for it’s high rate of melting, low pollution and ability to hold the metal for alloying purposes •Induction: (coreless induction): great for mixing characteristics for alloying and adding a new charge of metal or (core or channel furnace): great for superheating, holding and duplexing •Crucible: most commonly used furnace because it can be heated using various fuels such as commercial gases, fuel oil, fossil fuels or electricity. Can be stationary, tilting or movable. •Cupolas: Furnaces that can be operated continuously. They have high melting rates so produce large amounts of metal. They are currently starting to be replaced by induction furnaces because of the high costs involved. •Levitation melting: Involves magnetic suspension of the molten metal where an induction coil simultaneously heats, stirs and confines the melt eliminating the need for a crucible. This leaves the castings free of refractory inclusions and of gas porosity, and gives it a uniform fine grain. Melting Practice and Furnaces Electric Arc Furnace Induction Furnace Melting Practice and Furnaces Crucible Furnace Cupolas Furnace Levitation melting furnace Video clip of an electric arc furnace: http://www.matter.org.uk/steelmatte r/steelmaking/eaf.htm Multi-melt inductor furnace Foundries (from the Latin word fundere meaning melting and pouring) are where all casting operations are carried out. Foundries required a lot of manual labor in the past, but at present many of the operations are now automated. Automation varies from foundry to foundry depending on what and how much is needed to be produced. If a foundry requires production in the hundreds of thousands then most work is automated. But, if a foundry only has short production runs then less automation is required. http://www.grede.com/foundry_terms/foundry_t erms_frameset.shtml good site for terms about foundries Inside of a foundry This chapter describes general design considerations and guidelines for metal casting, ways of avoiding defects in metal casting, characteristics of alloys commonly cast together, and outlines the economics involved in casting operations. METAL CASTING (CH 12) METAL CASTING (CH 12) ? ? Design Considerations Design Considerations ? ? Guidelines for successful Guidelines for successful casting casting ? ? Characteristics and Characteristics and Applications of metals Applications of metals ? ? Economic considerations Economic considerations Design, Materials, and Economics Design Considerations Design Considerations ? ? Corners, angles and section thickness Corners, angles and section thickness ? ? Flat areas Flat areas ? ? Shrinkage Shrinkage Design Considerations Design Considerations ? ? Draft Draft ? ? Dimensional Tolerances Dimensional Tolerances ? ? Lettering and Markings Lettering and Markings ? ? Finishing Operations Finishing Operations Casting Alloys Casting Alloys ? ? Aluminum Aluminum ? ? Magnesium Magnesium ? ? Copper Copper ? ? Zinc Zinc ? ? Tin Tin ? ? Lead Lead Non Ferrous TABLE 12.2 Type of alloy Application Castability* Weldability* Machinability* Aluminum Pistons, clutch housings, intake manifolds E F G – E Copper Pumps, valves, gear blanks, marine propellers F – G F F – G Ductile iron Crankshafts, heavy-duty gears G D G Gray iron Engine blocks, gears, brake disks and drums, machine bases E D G Magnesium Crankcase, transmission housings 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 components for chemical plants F F F Steel (carbon and low alloy) Die blocks, heavy-duty gear blanks, aircraft undercarriage members, rail-road wheels F E F Steel (high alloy) Gas turbine housings, pump and valve components, rock crusher jaws F E F White iron 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, difficult.Casting Alloys Casting Alloys ? ? Cast Irons Cast Irons ? ? Largest quantity of metals Largest quantity of metals ? ? Wear resistance, hardness and good machinability Wear resistance, hardness and good machinability ? ? Cast Steels Cast Steels ? ? High cast temperature (1650 High cast temperature (1650° °C, 3000 C, 3000 ° °F) F) ? ? Applied to railroads, mining, chemical plants, oil Applied to railroads, mining, chemical plants, oil fields and heavy construction fields and heavy construction ? ? Stainless steels Stainless steels ? ? Casting similar to normal steels Casting similar to normal steels Ferrous Economics of Casting Economics of Casting ? ? Cost depends on several factors Cost depends on several factors ? ? Materials Materials- -materials with higher melting points require expensive dies and materials with higher melting points require expensive dies and machinery machinery ? ? Equipment Equipment- -the more sophisticated the equipment the more the cost the more sophisticated the equipment the more the cost ? ? Labor Labor- -single more costly factor in manufacturing single more costly factor in manufacturing TABLE 12.6 Cost* Process Die Equipment Labor Production rate (Pc/hr) Sand L L L – M <20 Shell-mold L – M M-H L – M <50 Plaster L – M M M–H <10 Investment M–H L-M H <1000 Permanent mold M M L – M <60 Die H H L – M <200 Centrifugal M H L – M <50 * L, low; M, medium; H, high.References References ? ? http://en.wikipedia.org/wiki/Image:Bronze_spearhead_mold.J http://en.wikipedia.org/wiki/Image:Bronze_spearhead_mold.J PG PG ? ? http://www.emachineshop.com/machines http://www.emachineshop.com/machines- -molding/images/die molding/images/die- - cast cast- -machine.jpg machine.jpg ? ? http://www.diecasting.org/faq/ http://www.diecasting.org/faq/ ? ? http://www.diecasting.org/design/case2/images/VacuumMetal http://www.diecasting.org/design/case2/images/VacuumMetal Pour.jpg Pour.jpg ? ? http://www.offshoresolutions.com/products/metal/images/casti http://www.offshoresolutions.com/products/metal/images/casti ngs/centrifugalCastingDiagram.jpg ngs/centrifugalCastingDiagram.jpg ? ? http://www.empirecastings.com/images/Proces7.gif http://www.empirecastings.com/images/Proces7.gif ? ? http://www.me.gatech.edu/jonathan.colton/me4210/ccdc3.gif http://www.me.gatech.edu/jonathan.colton/me4210/ccdc3.gif ? ? http://www.stahl http://www.stahl- -online.de/images/2 online.de/images/2- -1 1- -1_Bild5_30862.jpg 1_Bild5_30862.jpg ? ? http://www.inductothermindia.com/photos/furnace.jpg http://www.inductothermindia.com/photos/furnace.jpg ? ? http://www.nbm http://www.nbm- -houston.com/images/jpg/holding houston.com/images/jpg/holding- -furnace furnace- - SMALL.jpg SMALL.jpg ? ? http://www.dueker.de/ENG/bilder/kupol.jpg http://www.dueker.de/ENG/bilder/kupol.jpg References(cont) References(cont) ? ? http://www.bhrgroup.co.uk/graphics/pwteeturbulent.jpg http://www.bhrgroup.co.uk/graphics/pwteeturbulent.jpg ? ? http://i7.ebayimg.com/04/i/04/b4/60/35_1_b.JPG http://i7.ebayimg.com/04/i/04/b4/60/35_1_b.JPG ? ? http://www.me.gatech.edu/jonathan.colton/me4210/mfgvide http://www.me.gatech.edu/jonathan.colton/me4210/mfgvide os.html os.html ? ? http://www.nd.edu/~manufact/index3.htm http://www.nd.edu/~manufact/index3.htm ? ? http://www.norcanhydro.com/ images/nor_index2.jpg http://www.norcanhydro.com/ images/nor_index2.jpg ? ? http://www.kitchenkitchen.com/.../ images/scanpan http://www.kitchenkitchen.com/.../ images/scanpan- -fp.jpg fp.jpg ? ? http://www.greg http://www.greg- -j.com/ files/pipes.jpg j.com/ files/pipes.jpg ? ? http://www.cs.berkeley.edu/.../ IMGS/Crankshaft.jpg http://www.cs.berkeley.edu/.../ IMGS/Crankshaft.jpg ? ? http://www.mech.northwestern.edu http://www.mech.northwestern.edu ? http://www.thaimetalcasting.com/ Product/product.html ? http://www.eere.energy.gov/. ../profile.html References(cont) References(cont) http://www.ima-eu.org/ en/textfoundry.htm http://www.tth.com/ Metal%20casting.htm https://webmail.unm.edu/Redirect/ifcln1.ifc.org/ifcext/envi ro.nsf/AttachmentsByTitle/gui_foundries_WB/$FILE/fou ndries_PPAH.pdf https://webmail.unm.edu/Redirect/www.grede.com/foundr y_terms/foundry_terms_frameset.shtml