Introduction Of Engine Block

Introduction Of Engine stemUntil recently, cast urge on and aluminium vitiates comport been successfully use of wide-cuts and servicesd to reconcile near diesel and conventional gasoline-powered railway locomotive engluts.However, with a greater emphasis on increasing the efficiency of the locomotive via cant over reduction, there is a search for selection adulterates that be shadowyer than cast urge on and aluminium alloys, while retaining the necessary effectuality to withstand the forces of an engine. In the late 1990s engine leaveages made from tractile and former(a) experimental substantials were being used in prototype cars with the hope of developing more lightweight, efficient vehicles .Also lately newfound manufacturing do byes have been create that have brought to light two new alloys able for use in an engine block, magnesium alloy AMC-SC1 and compacted graphite cast iron (CGI). Thus this stand out entrust cover, the functional requirements o f the engine block, the processes used to manufacture the part, and the mechanical properties of the alloys.INTRODUCTIONTodays engines atomic number 18 an integral component of an automobile that are built in a number of configurations and are carry onably more interlacing than early automotive engines.The use of lighter and plastereder engineering sensibles to manufacture various components of the engine has also had an advert al diminisheding engineers to increment the power-to-weight of the engine, and thus the automobile. Since the engine block is also a relatively large component, it constitutes 20-25% of the total weight of an engine. Thus there is much interest in reducing the blocks weight.Keay, Sue Diet of Australian metal lightens cars and pollution, Media release, 14 October2002.Many early engine blocks were manufactured from cast iron alloys primarily due to its spicy-pitched school might and low cost. But, as engine designs became more complicated, the weigh t of the engine (and thus the vehicle) had increased. Thus the need to come up with lighter alloys that were as whole as cast irons arose. One much(prenominal) material that was being used as a substitute was aluminum alloys. Together, these two metals were used solo to fabricate engine blocks.Lately , however, a new material process has made a magnesium alloy suitable for use in engines. The alloy, called AMC-SC1, weighs less(prenominal) than both cast iron and aluminum alloys and represents new possibilities in engine manufacturing. A new manufacturing process have made compacted graphite cast iron (CGI) a viable alternative to grey-headed cast iron for the manufacture of diesel engine blocks. Like magnesium alloys, this material offers a higher(prenominal) enduringness and lower weight than gray cast iron.Thus this section will cover materials used to manufacture engine blocks , component discussion, its functional requirements, and the materials used to manufacture the part . The mechanical properties of the person alloys will be incorporated, along with the manufacturing processes used to fabricate the component.DESCRIPTION OF THE PRODUCTWHAT IS AN ENGINE BLOCK? The engine block is vital building complex body part of vehicles which run on congenital combustion, providing the powerhouse for the vehicle. The engine block is termed a block because it is usually a solid cast, housing the piston chambers and their components inside a cooled and be crankcase .Common components found in an engine include pistons, camshafts, timing chains,rocker arms, and other various parts. When fully stripped of all components, the core of the engine can be seen the cylinder block. The cylinder block (popularly known as the engine block) is the fuddledest component of an engine that provides much of the housing for the hundreds of parts found in a modern engine. The block is representatively arranged in a V, inline, orhorizontally-opposed (also referred to as flat) c onfiguration and the number of cylinders range from either 3 to as much as 16. depict 1 shows engine blocks with V configuation.opposed configurations.Functional Requirements of a Cylinder BlockBecause engine blocks are a unfavourable component of an engine, it must(prenominal) revenge a number of functional requirements. These requirements include withstanding high cycle fatigue stresses, thermal strains, and aggressive wear conditions over the full life of the engine, housing internal moving parts and fluids, ease of service and main(prenominal)tenance.REQUIRED MATERIAL PROPERTIESThe one-dimensional era of engine design is finished. The current approach considers the loads acting at each point of the engine block. (Vollrath, 2003)In target for an engine block to meet the above functional requirements, the engineering material(s) used to manufacture the the cylinder block material should have adequate strength and rigidity in compression, bending, and torsion. This is necessa ry to disapprove the gas oblige loads and also for the components, which convert the reciprocating motion of individual piston into a single rotary motion.The cylinder-block material should(a) be relatively cheap,(b) readily produce rolls with expert impressions,(c) be easily machined,(d) be rigid and strong enough in both bending and torsion,(e) have cheeseparing abrasion resistance,(f) have good corrosion resistance,(h) have a high thermal conductivity,(to frustrate failure under high temperatures).(i) retain its strength at high operating temperatures, and(J) have a relatively high thermal involution, low density.(to resist expanding under high operating temperatures)High strength is a particular concern in diesel engines, since compression ratios are normally 17.01 or higher compared to about 10.01 for conventional engines. , and thermal conductivity . Good machinability and castability of the metal alloy are also important factors in selecting the proper material, as the harder it is to machine the product, the higher the costs of manufacturing. In addition to the previously mentioned properties, the alloys must possess good vibration damping to absorb the vibrations of the moving parts.METALS USED IN THE concoct OF THE CYLINDER BLOCKSBased on the functional requirements of the cylinder block and the material properties required to meet the functional requirements, industries have used cast iron and aluminum alloys to manufacture the blocks.EXISTING MATERIALS1)Cast iron alloys are used because of the combination of good mechanical properties, low cost, and availability.2)Certain aluminum alloys combine the characteristics of iron alloys with low weight, thereby qualification the material more attractive to manufacturers who are seeking a competitive edge.NEW MATERIALS3)Compacted graphite cast iron is lighter and stronger than gray cast iron, fashioning the alloy a more attractive alternative to the latter in the production of cylinder blocks, pa rticularly in diesel engines.4)Magnesium alloys, which were previously unsuited for use as an engine block material, have the favour of being the lightest of all the mentioned metals, yet still retains the required strength demanded by a block.1)GRAY CAST campaign ALLOYSGray cast iron alloy have been the dominant metal that was used to manufacture conventional gas-powered engine blocks. Though extensive use of aluminum alloys has minimized the popularity of this material, it still finds wide use in diesel-fueled blocks, where the internal stresses are much higher. The use of cast iron blocks has been wide spread due to its low cost and good formability. Generally types of gray cast iron of pearlite microstructure is used in the manufacturing of engine block.Gray cast iron alloys typically compositionA typical cast iron is a gray cast iron, which contains 2.5-4 wt.% carbon, 1-3 wt.% silicon, 0.2-1.0 wt.% manganese, 0.02-0.25 wt.% sulfur, and 0.02-1.0 wt.% phosphorus Anyalebechi, P. N. Essentials of Materials Science Engineering, January 2005, p. 94.. and the balance (93.6%) iron. The carbon improves lubrication property of graphite, the silicon controls the formation of a laminated structure, called pearlite, which has good wearresistance, and the manganese strengthens and toughens the iron structure. A common aluminium alloy composition is 11.5% silicon, 0.5% manganese, and 0.4% magnesium, with the balance (87.6%) aluminium. The high silicon content in this alloy reduces involution only when improves cast-ability, strength, and abrasion resistance, while the other two elements strengthen the aluminium structure. While this alloy provides a good corrosion resistance, it can absorb solo moderate shock loads.Types of cast iron used in engine blockSAE grade G2500- used for small engine blocks.SAE grade G3500-used for heavy and larger diesel engine blocks.Also some flexible iron are also used in manufacturing engine blocks.SAE AMS 5313Cmechanical properties a lloying understanding the basics , by joseph R devis.Grade or class hardship HB(a)Tensile strength min(b) MPaYield strength min(b)MPaElongtion in 50 mm(2in),%(b)Class A190 grievous bodily harm41431015Gray cast iron has excellent damping capacity, good wear and temperature resistance, is easily machinable, and is inexpensive to produce. However, gray cast irons are relatively weakened and are prone to fracture and deformation.Although cast iron meets most of these requirements, it has a low thermal conductivity and is comparatively heavier. Due to these limitations, light aluminium alloys have been used as alternative cylinder-block materials for petrol engines. Cylinder liners are optional with cast-iron blocks but are more essential with the relatively soft light aluminum alloy blocks, as they cannot directly withstand wear resistance. Because of the lower strength of the aluminum alloys, the blocks are cast with thicker sections and additional support ribs, so that their weight becomes about half of the equivalent cast-iron blocks. Due to these problems, compacted graphite iron has recently begun to compete with gray cast iron as the choice material to produce diesel engine blocks.COMPACTED GRAPHITE CAST IRONCompacted graphite cast iron (CGI), which was accidentally discovered while trying toproduce ductile cast iron, possesses higher tensile strength and elastic modulus than gray castiron due to the compacted graphite found on the microstructure of CGI. fingers breadth 8 CGI typical microstructure 5% nodularity, 9% graphite, 265 particles/mm2.3. CGI a new combination of propertiesAs shown in Fig. 8, the compacted graphite iron graphite particles appear as individual worm- modeld or vermicular particles. The particles are elongated and randomly oriented as in gray iron however they are shorter and thicker, and have rounded edges. The compacted graphite syllable structure inhibits crack initiation and growth and is the source of theimproved mechanical pro perties, as compared to gray iron. Compacted graphite iron invariably includes some nodular (spheroidal) graphite particles. As the nodularity increases, the strength and stiffness also increase, but only at the expense of castability and thermal conductivity (Guesser et all, 2001). It is usual to set a limit of 20% nodularity for CGI specifications. give in 1 shows mechanical properties of CGI, with grades from 300 to 500 MPa.In the case of cylinder blocks and heads, where castability, machinability and light up transfer are all of paramount importance, it is necessary to impose a more narrow specification. A typical specification for a CGI cylinder block or head can besummarised as follows1) 0-20% nodularity, for optimal castability, machinabilityand heat transfer2) No free flake graphite, flake type graphite (as in greyiron) causes local weakness3) 90% pearlite, to provide high strength and unchangingproperties4) This general specification will result in a minimum-measured ten sile strength of 450 MPa in a 25 mm diameter test bar, andwill satisfy the ISO 16112 Compacted Graphite Iron touchstone for Grade GJV 450. The typical mechanical properties for thisCGI Grade, in comparison to conventional grey cast iron and aluminium are summarised in Table 1Mechanical and Physical Propertiesof CGI in comparison to conventional grey cast iron and aluminium at 20CPropertyUnitsGJV 450GJL 250GJL 300A 390.0Ultimate Tensile StrengthMPa450250300275Elastic ModulusGPa14510511580Elongation%1 to 2001Rotating-Bending Fatigue 20C)MPa210110125100Rotating-Bending Fatigue (225C)MPa20510012035Thermal conductionW/m-K364639130Thermal Expansionm-m-K12121218Densityg/cc7.17.17.12.7Brinnell HardnessBHN 10-3000215-255190-225215-225110-clThe results allow the comparison between CGI and gray iron. It can be seen the increase on tensile strength, moving from gray iron to CGI. CGI also shows a higher elastic modulus, when compared to gray iron.- Mechanical properties of gray iron and CGI gr ades 400-450. 195-230 HB. Samplestaken from the castings (Guesser, 2003).Figure 10 Elastic modulus of gray iron and CGI grade 400. 12.0L I6 cylinder block (Guesser,2003).The results in Figure 10 were obtained from two sources test bars and main bearings of a 12.0L cylinder block. The increase in elastic modulus, from 100 GPa for gray iron to 150 GPa for CGI, results in slighter cylinder bore distortion as reported by Tholl et all (1996), therefore reducing oil consumption and emissions. Results of fatigue strength tests can be seen on figure 11, comparing gray iron grade 250 and CGI grade 450, samples from an I6 5.9L diesel cylinder block. The fatigue limit for the gray iron is 62-79 MPa, depending on the carbon content, while for the CGI the fatigue limit is 175 MPa. The raise of fatigue strength allows the designer to reduce the cylinder block weight.As a result of mechanical properties improvements, a design study conducted by AVL Austria (Sorger Holland, 1999) has evaluated do wnsizing opportunities for a 1.8 L diesel engine cylinder block, converting from gray iron to CGI. The benefits of this change included1)9% reduction in overall weight of the finished engine2) 22% reduction in weight of machined cylinder block3) 15% reduction in overall length of the finished engine4) 5% reduction in both height and width of the finished engineLike gray cast iron, compacted graphite cast iron has good damping capacity and thermalconductivity, but its difficulty to machine has limited the wide-scale use of CGI. A newmanufacturing process, however, has undecided the way for larger applications of CGI. Thedevelopment of rotary insert tools has increased the life of the tools used to machine the metal,thus allowing manufacturers to use CGI without worrying about purchasing new tools Georgiou, George Iron engines may be in your future, Tooling Production, September2003, Vol. 69, issue 9, p. 26..MAGNESIUM ALLOYSMagnesium alloys have been used in engines before, but not for cylinder blocks. Rather. The main advantage of this alloy is that the material is much lighter than cast iron and aluminum alloys and has the same strength as cast iron and aluminum alloysLampman, Steven adjust Up the Metals in Auto Engines, Advanced Materials Processes, May 1991, p. 17.Anonymous, Magnesium alloy resists high temperature in engine blocks, AdvancedMaterials and Processes, August 2003, vol. 161, issue 8, p. 13.. Material scientists and engineers were unyielding to exploit these characteristics of magnesium alloy and use it to fabricate engine blocks. on that point were a number of magnesium alloys available that met or exceeded the requirements demanded by manufacturers for an engine block, but insufficient material stabilityat high temperatures hindered their actual use. Following are the two alloys which have been found suitable for luck production of engine blocks.AMC-SC1In 2003 material scientists and engineers from the Cooperative Research Center for Cas t Metals Manufacturing and theAustralian Magnesium Corporation presented their discovery of sand-cast AMC-SC1 magnesium alloy Anonymous, Magnesium alloy resists high temperature in engine blocks, AdvancedMaterials and Processes, August 2003, vol. 161, issue 8, p. 13.. This grade of magnesium alloy contains two rare earth elements, lanthanum and cerium, and was heat-treated with T6. This stabilizes the strength of the alloy at high engine operating temperatures, which is a necessary requirement for a cylinder blockmaterial 16. Bettles et al. had performed experiments to determine the yield and creep strengths of AMC-SC1 and their results are shown in Table 3 Bettles, C. et al., AMC-SC1 A New Magnesium Alloy Suitable for PowertrainApplications, Society of Automotive Engineers, 2003, p. 2.. From Table 3, the most significant point is that the yield strength of AMC-SC1 essentially stays the same at 177C as it does at manner temperature.Table 3 Yield and creep strengths of magnesium AMC -SC1 at room temperature, 150C, and177C 17.Room temperature24C150C177CYield strength, MPa120116117Creep strength, MPa12098This means that the material is able to tolerate a wide range of operating temperatures without a loss in strength. Other properties of the magnesium alloy 10 include good thermal conductivity, excellent machining and casting qualities, and excellent damping characteristics. To demonstrate the significant weight savings of magnesium alloy over cast iron andaluminum alloy, consider BMWs inline-6 R6 (shown in Figure 4), which re rigid the companys M54 aluminum engine. Its cylinder block is made of AMC-SC1 and is said to have decreased the weight of a comparably-built gray cast iron and aluminum alloy block by 57% and 24% Jost, Kevin BMW builds better inline six, Automotive Engineering International, January2005, pp. 20-32.. So far, BMW is the only company to have used magnesium alloy cylinder blocks in production vehicles. But, with a significant weight advantage o ver the current alloys used today and negligible increase in cost, other manufacturers will begin to consider the use of AMC-SC1 and possibly other grades of magnesium alloys for engine blocks.Figure 4 BMWs 6-cylinder R6 powerplant uses a magnesium alloy AMC-SC1-fabricatedcylinder block Jost, Kevin BMW builds better inline six, Automotive Engineering International, January2005, pp. 20-32..PRODUCTION PROCESS STANDARD CASTING WITH SOME MODIFICATIONSThis alloy can be cast using a standard production process, with some modifications.For a magnesium alloy engine to be economically viable, it is not merely the cost ofthe alloy that is important. The casting process must also be commercially viable.There are several modifications required if an existing casting line of cast iron or aluminum is to be converted toone producing magnesium parts.These can be summarised as follows A new inhibitor in the sand cores to prevent reaction between the melt and thesand. A redesign of the runner and gat ing system to ensure adequate filling(magnesium alloys have a low heat content). Preheating of the core megabucks to 150C. Modifications to the core package design to allow low pressure rather thangravity filling and feeding.AM-HP2AM-HP2 A High Pressure Diecasting Magnesium AlloyThe AM-HP2 magnesium alloy has convertible high-temperature strength to AM-SC1 and has been specially tailored for use in the high pressure diecasting process. Like AM-SC1, the light-weight alloy significantly increases fuel-efficiency, environmental sustainability and vehicle agility and is suitable for the powertrain components of vehicles, such as engines blocks etc.Need for New alloyAM-HP2AM-HP2 has been specifically developed as a diecasting alloy for high temperature automotive powertrain applications, such as engine blocks, structural sumps and automatic transmission housings. The alloy is based upon the successful sand casting alloy, AM-SC1, with a modified composition to make it suitable for the high pressure die casting process.Commercial Opportunities AM-HP2 Magnesium Alloy in the Auto industryHigh pressure diecasting is a highly productive process for mass production of light alloy components. While the casting integrity of sand casting and low pressure/gravity permanent mould castings is higher than high pressure diecasting, the latter technology is cheaper. Thus, this process is gaining popularity among auto manufacturers for casting of aluminium engine blocks. It is also the common process for powertrain components such as transmission housings. There is a strong demand in the automotive industry for a suitable high pressure diecasting magnesium alloy for high volume powertrain applications. AM-HP2 exhibits good diecastability and the required high temperature mechanical properties for engine components (including engine blocks) and automatic transmission housings. It has similar creep properties to alloy, AM-SC1.Advantages of AM-HP2 Magnesium over Other AlloysA key a dvantage of AM-HP2 is that the alloy is more diecastable than competitor high temperature creep resistant magnesium alloys.Thus, the alloy can be more readily cast into complex shapes with fewer rejects and a wider operating window. The alloy also has better high temperature creep strength than its competitors and thus offers considerable advantage to engine designers seeking to obtain uttermost performance for lowest weight and cost.current status of AM-HP2 magnesium developmentPilot scale diecasting trials and laboratory testing of mechanical properties have demonstrated the suitability of AM-HP2 for mass produced powertrain components.PRODUCTION PROCESSES3.2 Casting ProcessesThere are two methods used to cast engine blocks for all materials green sand molding or wooly scintillate casting. The latter, pioneered by General Motors for their Saturn vehicles, have11 become more popular due to its capability to produce near net shape components, provide tight tolerances for critica l components, and reduce machine maintenance and cost 19. super acid sand molding, however, is still widely used in industry as material costs are low and most metals canbe cast by this method Luther, Norris Metalcasting and Molding Processes, Online, 22 March 2005-last visited,Available http//www.castingsoruce.com/tech_art_metalcasting.asp..3.2.1 Green Sand MoldingGreen sand molding the common method to cast engine blocks. The term green denotes the presence of moisture in the molding sand .Figure demonstrates the ensample used in sand casting.The pattern mounted into the moulding box along with the runner and ingate system ready to produce a mould.http//www.dmdaustralia.com.au/block1.htmlFrom Figure 2, a combination of silica sand, clay, and water poured in one-half of the block pattern with a wood or metal frame. The mold is then compacted by squelch or jolting, and the process is repeated for the other half of the mold. A core consisting of hardened sand is used for support. Then, molten cast iron, aluminum, or magnesium alloy is poured into the combined molds and solidifies.Once the latter part has been completed, the molds are removed, and the cylinder block is cleaned and inspected. Heat treatment of the block is then undertaken to improve the mechanical properties of the alloy for suitable use.7.12LOST FOAM CASTINGTHE PROCESSFigure 6 Graphical description of the last 6 of 7 methods of the alienated foam casting method Anonymous, atomic number 13 Cylinder Block for General Motors Truck/SUV engines, A DesignStudy in Aluminum Casings, pp. 1-31.The lost foam casting process uses a expanded polystyrene replica of the part being cast.1)The coated replica/pattern is placed in a flask and loose sandis placed around the pattern and shaken into its voids.2)Molten metal is then poured through a foam sprue, orfunnel, into the sand where the hot metal melts anddisplaces the foam of the pattern.3)the metal cools in the shape of the part.The basic steps of the lostfoam casting process are1) drill Molding Bead Pre expansion and Conditioning, Tool Preheat, Pattern Molding, Pattern Aging2)Pattern/Cluster Assembly3)Pattern Coating and Drying4)Sand Fill and Compaction Metal Casting and Cooling5)Shakeout, Clean-up, and FinishingLost foam casting is a more reliable and efficient casting technique of the manufacture of engine blocks than green sand molding. The technique begins with the use of polystyrene string of beads placed in preexpanders for wet expansion to control bead size and density to produce four separate block moldings to be glued together to form the final mold 7, 19. Next, the metal tool is preheated to remove any moisture and then filled with the beads. The tool is then heated via steam and placed in an autoclave, where it is subjected to high pressures in order to create the molds 7. The tool is removed from the autoclave and immersed in water to finish the moldings. Precise control over the heating and cooling aspect ensures dimensionally accurate, smooth and strong molds Anonymous, Aluminum Cylinder Block for General Motors Truck/SUV engines, A DesignStudy in Aluminum Casings, pp. 1-31.. If the tool was not heated before the beads were injected, the results would be rough finishes in the molds with low-strength sections. If the tool and beads stay heated for an extended period of time, or is not cooled enough, the beads become overfused, which produces surface variations in the moldings. If the tool has beeninadequately cooled, the molds will contain variations in dimensions Anonymous, Aluminum Cylinder Block for General Motors Truck/SUV engines, A DesignStudy in Aluminum Casings, pp. 1-31.. Figure 3 shows thefinal half stages of the lost foam casting method. . From Figure 3, once the individual molds are glued together, the assembly is placed in a vat with water-based ceramic liquid to prevent molten metal from destroying the mold, stiffen the assembly, and provide a smooth finish Anonymous, Aluminum Cylinder Block for General Motors Truck/SUV engines, A DesignStudy in Aluminum Casings, pp. 1-31.. The assembly can also be sprayed with the ceramic liquid, but is a time-consuming process. Next, the coated foam engine block is filled with sand,13 compacted, and immersed in the molten metal alloy. Once cooled, sand is removed from the metal casting, cleaned, and undergoes heat treatment to increase the mechanical properties of the block. Finally, coolant and oil passages are machined into the block.Advantages over conventional sand castingUnlike conventional sand casting, the lost foam process allows more complex and detailed passages and other features to be cast directly into the part. The lost foam process1) Forms complex internal passages and features without cores.2) Reduces part mass with near net shape capability.3) Eliminates parting lines.4) Reduces machining operations and costs.5)Provides for tight tolerances in critical areas and features.Lost Foam Casting for Fine Feat uresThe lost foam casting process allows more complex and detailed passages and other features to be cast directly into the cylinder block.1) In the cylinder block, oil galleries, crank case ventilationchannels, oil drain choke off passages, and coolant passages are castinto the block.2) These features would otherwise require drilling or externalplumbing (with a potential for leaks).3)Lost Foam castings have tighter dimensional tolerances compared to sand castings, because variations caused bycore release and core variability are eliminated and there is much less tool wear over the production life. The direct result is a significant reduction in machining costs and infrastructure investment and fewer opportunities for errors in machining and assembly.A comparison of green sand casting to lost foam casting shows a number of distinct advantages for lost foamPropertyGreen Sand CastingLost Foam CastingComplex innerFeatures and PartConsolidationComplexity determined by sand corelimitat ions geometry, strength, andcost.Extensive and complex internal features (as small as0.20) available in lost foam, based on detail duplication and pattern assembly in foam.DimensionalTolerances+/- 0.030 is typical depending on partsize, complexity, and geometry+/- 0.005-0.010 is typical depending on part size, complexity, and geometry. uprise FinishCapabilities250-600 microinches typical. Dependson grain fineness of sand.60-250 microinches typical. Depends on bead size and ceramic coating grain fineness.Feature AccuracyCore movement and shift between moldhalves across the parting line limitfeature accuracy.No cores or mold halves to shift and degrade featureaccuracy leave of absence Line andDraft AnglesParting lines and draft angles arenecessary for molding.No parting lines in the mold and minimal draft on tools.Environmental beSand recovery requires binder removaland time consuming sand clean-upSand is binder free, so it can be easily and rapidly recovered a