Essay: Material engineering

 
ASK 1 MATERIAL SELECTION
MATERIALS SECLECTED
 POLYMER— Interior designing materials like dash board, etc.
 MEATALS— materials used for making of an engine.
 COMPOSITEs—materials used for making axel.
 CERAMIC— materials used for making electrical components and safety equipment’s in car.
POLYMER
Plastics and polymer composites have been essential to a wide range of safety and performance breakthroughs in today’s cars, minivans, pickups and SUVs. Today’s plastics and polymer composites typically make up 50% of the volume of a new light vehicle but less than 10% of its weight, which helps make cars lighter and more fuel efficient, resulting in lower greenhouse gas emissions. Tough, modern plastics and polymer composites also help improve passenger safety and automotive designers rely on the versatility of plastics and polymer composites when designing today’s vehicles. In addition, many plastic resins are recyclable.
Properties.
1. Light in weight.
2. Cheaply available.
3. Can be casted and moulded into desirable shape.
4. High toughness.
5. High heat resistance.
Why plastic polymer is used extensively in automobile manufacturing?
Automotive Body Exterior – Plastics and composites have revolutionized the design of body exteriors. From bumpers to door panels, light weight plastic provides vehicles with better gas mileage and allows designers and engineers the freedom to create innovative concepts.
Automotive Interior – The elements of automotive interior design — comfort, noise level, aesthetic appeal, ergonomic layout, and durability — have a great effect on a consumer\’s purchasing decision. Plastic automotive interior parts address all of these aspects, and more, in a remarkably effective and efficient manner.
Automotive Safety – The versatility of plastics allows design options that reduce vehicle weight while producing safer vehicles.
Automotive Chassis – A chassis is the supporting frame of a light vehicle. It gives the vehicle strength and rigidity, and helps increase crash-resistance through energy absorption.
Plastics used in producing car interior.
METALS
Grey cast iron alloy have been the dominant metal that was used to manufacture conventional gas-powered engine blocks widely used in diesel-fuelled blocks, where the internal stresses are much higher.
Properties.
1. It contains 2.5-4 wt.% carbon and 1-3 wt.% silicon, 0.2-1.0 wt.% manganese, 0.02-0.25 wt.% sulphur+, and 0.02-1.0 wt.% phosphorus.
2. It has excellent damping capacity.
3. Good temperature resistance.
4. It is easily Machin able.
5. It is used to make engine block.
BMW’s S54 inline-6 engine, which uses a grey, cast iron engine block.
Why grey cast iron is used for manufacturing engine block?
The S54 block was made from grey cast iron was the need for a stronger material that could tolerate the higher performance levels (the S54 produces333 brake horsepower and has a maximum engine speed of 8000 rpm, whereas the M54produces 184-225 brake horsepower with a maximum engine speed of 6500 rpm).
COMPOSITES
Carbon fibre (alternatively CF graphite fibre or graphite fibre) is a material consisting of fibres about 5-10 micrometres in diameter and composed mostly of carbon atoms.
Properties—
• High stiffness.
• High tensile strength.
• Low weight.
• High chemical resistance.
• High temperature tolerance.
• Low thermal expansion.
Why and where is carbon fibre used?
It is used in making of drive shafts in automobile manufacturing
It is used because it has—-
1. Lower NHV (noise, vibration, & harmonics) levels.
2. Higher RPM capability.
3. Lighter weight.
4. Torsional damper.
5. Greater life cycle.
6. Greater torsional strength.
CERAMICS
Ceramic based electrical components for automotive application have become exponentially more sophisticated while their size continues to decrease.
Properties—
• Very high hardness and strength.
• High melting points.
• Good electrical insulator.
• Thermal insulator.
Why are they used in automobile?
It reduces the cost but offers similar and improved characteristics when compared to other materials
Their properties and characteristics is paving the way for next generations of vehicles, hybrids and other eco-friendly cars and features.
The advanced ceramic components, with their low cost, small size, improved reliability and ability to meet the stringent demands of the automotive environment are making important strides in market.
TASK 2 MICROSTRUCTURE AND MACROSCOPIC BEHAVIOR
Explain the particular characteristics related to the microstructure and macroscopic behaviour of the following four categories of materials.1) Metal 2) Polymer. 3) Composite. 4) Ceramic.
MICROSTRUCTURE
Microstructure is the small scale structure of a material, defined as the structure of a prepared surface of material as revealed by a microscope above 25× magnification.
The microstructure of a material (such as metals, polymers, ceramics or composites) can strongly influence physical properties such as strength, toughness, ductility, hardness, corrosion resistance, high/low temperature behaviour or wear resistance.
Showing microstructure of a sample material
Application of microstructure
Microstructures are often used in finding defects in materials. The 20 X magnification shows the defects in a material which would be sorted out by analysing the defects which would help out in successfully manufacturing a final product.
A micrograph of bronze revealing a cast dendritic structure
MACROSTRUCTURE
Macrostructure is the appearance of a material in the scale millimetres to meters it is the structure of the material as seen with the naked eye.
Metals
Microstructure of metal
Microstructure of aluminium.
Macroscopic behaviour of aluminium.
aerospace alloy having a low amount of Mg (1.2% wt.) has been characterised in terms of its microstructure and localised corrosion properties in order to provide both qualitative and quantitative input data for microscale and macroscale corrosion numerical models and simulations. Microstructural characterisation of the studied Al 2024 indicate a significant presence of nanoscale dispersoid and nanoscale and microscale AlCuFeMnSi (second phase) intermetallic particles, but a smaller population of microscale θ phase (Al2Cu) and microscale S phase (Al2CuMg) precipitate particles. The more common Al 2024 alloy which has a higher amount of Mg (1.5% wt.) shows a much greater presence of S phase precipitates and little or no θ phase precipitates. The results from localised corrosion studies of the Al 2024 with low Mg show that pitting potential (PP) values measured for second phase, S phase, or matrix have a large variation, but that the differences between the PP and open-circuit potential (OCP) values [(PP–OCP)] have a more consistent trend which correlates with the microstructural phase. The corrosion behaviour of the Al 2024 alloy with low Mg is significantly different from that already reported for an Al 2024 (AA2024-T3) alloy with more common composition having a greater amount of Mg.
Microstructure of polymer
The microstructure of a polymer (sometimes called configuration) relates to the physical arrangement of monomer residues along the backbone of the chain. These are the elements of polymer structure that require the breaking of a covalent bond in order to change. Structure has a strong influence on the other properties of a polymer. For example, two samples of natural rubber may exhibit different durability, even though their molecules comprise the same monomers.
Macroscopic behaviour of polymer
1) The plastic behaviour of fcc metals (Al, Au, Cu, Ni) was investigated over a wide range of strain and testing temperature. The experimental stress strain data were described by both macroscopic relationships and major microscopic mechanisms.
2) 2) Quantitative correlations are presented to demonstrate the primary features of the microscopic processes determining the parameters describing the macroscopic evolution of the stress strain relationships during plastic.
Microstructure of ceramic
Microstructure, which is too small to be seen with the naked eye, plays an important factor in the final property of a material. For ceramics, the microstructure is made up of small crystals called grains. In general, the smaller the grain size, the stronger and denser is the ceramic material. In the case of a glass material, the microstructure is non-crystalline. When these two materials are combined (glass-ceramics), the glassy phase usually surrounds small crystals, bonding them together.
MACROSCOPIC BEHAVIOUR OF CERAMICS
The effect of matrix micro cracking within a SiC-SiC composite on its macroscopic behaviour. Experimentally, ultrasonic evaluation under load is used. Ultrasonic velocities are measured for varying propagation directions as a function of applied stress. The anisotropic stiffness degradation due to the applied stress is determined from ultrasonic velocity measurements. This anisotropic stiffness degradation is a function of micro crack evolution and accumulation in the damaged composite. The theoretical approach is developed in the framework of continuum damage mechanics.
MICROSTRUCTURE OF COMPOSITES
Hyperplastic composites undergoing finite deformation, microstructure evolution due to finite changes in geometry plays a key role in determining the effective behaviour.
TASK 4 INVESTIGATION OF SUITABLE DATA
) Investigate and assess the quality of suitable data obtained from three different sources and then decide which data is more suitable. Data for the particular product. Product is of learner’s choice.
Product selected
Motorcycle
From book
Book. (The History of Motorcycling.)
Ayton, Cyril, Bob Holliday, Cyril Posthumous and Mike Winfield. The History of Motorcycling. London: Orvis Publishing, 1979. Lear, George and Lynn S. Mosher, Motorcycle Mechanics. Englewood Cliffs, NJ: Prentice Hall, 1997.
Raw Materials
The primary raw materials used in the manufacture of the body of motorcycle are metal, plastic and rubber.
The motorcycle frame is composed almost completely of metal, as are the wheels. The frame may be overlaid with plastic. The tires are composed of rubber. The seat is made from a synthetic substance, such as polyurethane. The power system consists of a four-stroke engine, a carburettor to transform incoming fuel into vapour, a choke to control the air-fuel ratio, transmission, and drum brakes. The transmission system contains a clutch, consisting of steel ball flyweights and metal plates, a crankshaft, gears, pulleys, rubber belts or metal chains, and a sprocket.
The Motorcycle electrical system contains a battery, ignition wires and coils, diodes, spark plugs, head-lamps and taillights, turn signals and a horn.
A cylindrical piston, made of aluminium alloy (preferred because it is lightweight and conducts heat well), is an essential component of the engine. It is fitted with piston rings made of cast iron. The crankshaft and crankcase are made of aluminium. The engine also contains a cylinder barrel, typically made of cast iron or light alloy.
The Manufacturing Process
Raw materials as well as parts and components arrive at the manufacturing plant by truck or rail, typically on a daily basis. As part of the just-in-time delivery system on which many plants are scheduled, the materials and parts are delivered at the place where they are used or installed.
Manufacturing begins in the weld department with computer-controlled fabrication of the frame from high strength frame materials. Components are formed out of tubular metal and/or hollow metal shells fashioned from sheet metal. The various sections are welded together. This process involves manual, automatic, and robotic equipment.
In the plastics department, small plastic resin pellets are melted and injected into molds under high pressure to form various plastic body trim parts. This process is known as injection moulding.
Plastic and metal parts and components are painted in booths in the paint department using a process known as powder-coating (this is the same process by which automobiles are painted). A powder-coating apparatus works like a large spray-painter, dispersing paint through a pressurized system evenly across the metal frame.
Painted parts are sent via overhead conveyors or tow motor (similar to a ski lift tow rope) to the assembly department where they are installed on the frame of the motorcycle.
A motorcycle engine. The engine is mounted in the painted frame, and various other components are fitted as the motorcycle is sent down the assembly line.
Wheels, brakes, wiring cables, foot pegs, exhaust pipes, seats, saddlebags, lights, radios, and hundreds of other parts are installed on the motorcycle frame. A Honda Gold Wing motorcycle, for example, needs almost as many parts to complete it as a Honda Civic automobile.
Quality Control
At the end of the assembly line, quality control inspectors undertake a visual inspection of the motorcycle\’s painted finish and fit of parts. The quality control inspectors also feel the motorcycles with gloved hands to detect any bumps or defects in the finish. Each motorcycle is tested on a dynamometer. Inspectors accelerate the motorcycle from 0-60 mph. During the acceleration, the “dyno” tests for acceleration and braking, shifting, wheel alignment, headlight and taillight alignment and function, horn function, and exhaust emissions. The finished product must meet international standards for performance and safety. After the dyno test, a final inspection is made of the completed motorcycle. The motorcycles are boxed in crates and shipped to customers across North America and around the world.
Reference from
From website www.madehow.com
Read more: http://www.madehow.com/Volume-4/Motorcycle.html#ixzz3zfhVj9V3
The Manufacturing Process
Raw materials as well as parts and components arrive at the manufacturing plant by truck or rail, typically on a daily basis. As part of the just-in-time delivery system on which many plants are scheduled, the materials and parts are delivered at the place where they are used or installed.
Manufacturing begins in the weld department with computer-controlled fabrication of the frame from high strength frame materials. Components are formed out of tubular metal and/or hollow metal shells fashioned from sheet metal. The various sections are welded together. This process involves manual, automatic, and robotic equipment.
In the plastics department, small plastic resin pellets are melted and injected into molds under high pressure to form various plastic body trim parts. This process is known as injection moulding.
Plastic and metal parts and components are painted in booths in the paint department using a process known as powder-coating (this is the same process by which automobiles are painted). A powder-coating apparatus works like a large spray-painter, dispersing paint through a pressurized system evenly across the metal frame.
Painted parts are sent via overhead conveyors or tow motor (similar to a ski lift tow rope) to the assembly department where they are installed on the frame of the motorcycle. A motorcycle engine.
A motorcycle engine.
The engine is mounted in the painted frame, and various other components are fitted as the motorcycle is sent down the assembly line.
Wheels, brakes, wiring cables, foot pegs, exhaust pipes, seats, saddlebags, lights, radios, and hundreds of other parts are installed on the motorcycle frame. A Honda Gold Wing motorcycle, for example, needs almost as many parts to complete it as a Honda Civic automobile.
From http://bikeadvice.in/bike-manufacturing/
Market Research
The safest way to launch any product in today’s competitive market is to have research: Research about who will be the customer, what customer likes, and what customer needs. These researches are carried out by marketing department of the companies or given to other surveying companies.
This market research also depends on type of vehicle that a company wants to introduce i.e. new segment, facelift version of previously launched vehicle, or DNA type vehicle. Market research becomes more vital when any company plans to launch a new segment. Customers are openly or circuitously got involved in this type of survey. New segment may be decided with respect to fuel economy, price tag, and top speed, type of engine or type of vehicle.
Sketching
Drawing or Sketching was the first language used by Homo sapiens and still used in all industries either on paper or on computer screens. It is the most productive and economical method to develop and predict any concept. Same is also applicable with automobile industry. Each and every vehicle running on the road today was a conceptualized sketch on the paper before few years.
Numbers of sketches are prepared by the designers on final concept which got selected by the authorities. Designers also have to include benchmarks of the company along with engineering aspects. Engineering aspects like dimensions, space, and feasibility of manufacturing of exterior components are considered in conjunction with aesthetics. First of all, one sketch is selected as a final product which contains overall look. After that, overall dimensions are selected according to vehicle’s segment and engineering terms. After deciding vehicle as a whole, designers start sketching each details of the vehicle like head lights, side indicators, ORVMs, tail lights, tank, seats, fairings, wheels, axles, muffler, foot rests, locking nuts etc. One more time vehicle is assembled on paper and final sketch is prepared for modelling.
Software Modelling
Modelling is done before starting any designing for vehicle. This provides idea about space available with engineers to design any component. It already has become very easy to prepare a model for any product with the help of software’s and robots. In the case of automobile, this process is very important and required precision. Modelling gives three dimensional judgement about vehicle.
Clay/ Wax Modelling
Besides soft modelling, many companies also prepare clay or wax models of vehicle. These models are used to judge the bulk and to predict aerodynamic characteristics of vehicle. Generally, clay models are prepared for expensive rides. It is just like a hard copy or printout of any softcopy from the computer.
Robots are used to create these types of model. Robots help to get precision and reduce process time. Before technical revolution in computers, this was only method used for modelling of any vehicle.
Designing
Designing is a complex synthesis and analysing process of forces and stresses on any component. Each and every component of vehicle is analysed with the help of software’s. Designing software works with that model which is generated in modelling software. This is done with the help of Interface facilities. Engineer can check any component under static, dynamic, thermal, or cyclic loads and can predict component’s life.
Simulations
Particularly for automobiles, simulation software’s are computer logics for vehicle’s dynamic conditions. Simulation software’s can generate identical road and wind conditions which an original vehicle is going to face.
This helps engineers and designers to predict and modify any of the dynamic characteristic of vehicle before actual production. Just like analysis software’s, simulation software also reduces cost and time for testing a vehicle. Different road profiles like smooth road, bumps, pit holes etc. can be generated and vehicle model can be tested without original vehicle.
Testing
No one can remain dependable on software’s when safety comes into pictureThat’s why each and every company tests it’s each vehicle before starting its production.These vehicles are used for different road tests, rollover tests and crash tests. Experience test drivers are allowed to drive these vehicles up to extreme conditions on the testing tracks. This testing period is kept long enough to get exact idea about any failures. Many a times new failure arises which is not exposed by the analysis or simulation software’s.
Production
Finally production starts after completing all the required modifications in manufacturing facilities. These modifications includes testing rigs, testing tracks, material handling methods, material handling racks, manpower, production of subassemblies, assembly lines, quality testing, paint shop, vendor management etc. Company announces official launch of vehicle and starts distributing fix numbers of produced vehicle amongst each dealers.
Then sales department studies the market demand through dealers. New production schedule is introduced according to demand and supply chain. Each vehicle is tested according to minimum standards decided by country’s governing body (As ARAI in India). Vehicles are distributed in different numbers to different dealers according to their regional demand.
Reference from classes.bus.oregonstate.edu(book)
According to the above reference from website www.madehow.com is the best suitable data, because it perfectly explain the process from raw materials to the final product
TASK 7 TREATMENT PROCESS OF STEEL
Heat Treatment of Steel
Steels can be heat treated to produce a great variety of microstructures and properties. Generally, heat treatment uses phase transformation during heating and cooling to change a microstructure in a solid state. In heat treatment, the processing is most often entirely thermal and modifies only structure. Thermomechanical treatments, which modify component shape and structure, and thermochemical treatments which modify surface chemistry and structure, are also important processing approaches which fall into the domain of heat treatment
ANNEALING
Annealing occurs by the diffusion of atoms within a solid material, so that the material progresses towards its equilibrium state. Heat increases the rate of diffusion by providing the energy needed to break bonds. The movement of atoms has the effect of redistributing and eradicating the dislocations in metals and (to a lesser extent) in ceramics. This alteration to existing dislocations allows a metal object to deform more easily, increasing its ductility.
The amount of process-initiating Gibbs free energy in a deformed metal is also reduced by the annealing process. In practice and industry, this reduction of Gibbs free energy is termed stress relief.
The relief of internal stresses is a thermodynamically spontaneous process; however, at room temperatures, it is a very slow process. The high temperatures at which annealing occurs serve to accelerate this process.
The reaction that facilitates returning the cold-worked metal to its stress-free state has many reaction pathways, mostly involving the elimination of lattice vacancy gradients within the body of the metal. The creation of lattice vacancies is governed by the Arrhenius equation, and the migration/diffusion of lattice vacancies are governed by Fick’s laws of diffusion.
In steel, there is a carburation mechanism that can be described as three distinct events: the reaction at the steel surface, the interstitial diffusion of carbon atoms and the dissolution of carbides within the steel.
Stage
The three stages s of the annealing process that proceed as the temperature of the material is increased are: recovery, recrystallization, and grain growth. The first stage is recovery, and it results in softening of the metal through removal of primarily linear defects called dislocations and the internal stresses they cause. Recovery occurs at the lower temperature stage of all annealing processes and before the appearance of new strain-free grains. The grain size and shape do not change. The second stage is recrystallization, where new strain-free grains nucleate and grow to replace those deformed by internal stresses. If annealing is allowed to continue once recrystallization has completed, then grain growth (the third stage) occurs. In grain growth, the microstructure starts to coarsen and may cause the metal to lose a substantial part of its original strength. This can however be regained with hardening.
Controlled atmospheres
The high temperature of annealing may result in oxidation of the metal’s surface, resulting in scale. If scale must be avoided, annealing is carried out in a special atmosphere, such as with endothermic gas (a mixture of carbon monoxide, hydrogen gas, and nitrogen gas). Annealing is also done in forming gas, a mixture of hydrogen and nitrogen. The magnetic properties of mu-metal (Espy cores) are introduced by annealing the alloy in a hydrogen atmosphere.
Setup and equipment
Typically, large ovens are used for the annealing process. The inside of the oven is large enough to place the workpiece in a position to receive maximum exposure to the circulating heated air. For high volume process annealing, gas fired conveyor furnaces are often used. For large workpieces or high quantity parts, car-bottom furnaces are used so workers can easily move the parts in and out. Once the annealing process is successfully completed, workpieces are sometimes left in the oven so the parts cool in a controllable way. While some workpieces are left in the oven to cool in a controlled fashion, other materials and alloys are removed from the oven. Once removed from the oven, the workpieces are often quickly cooled off in a process known as quench hardening. Typical methods of quench hardening materials involve media such as air, water, oil, or salt. Salt is used as a medium for quenching usually in the form of brine (salt water). Brine provides faster cooling rates than water. This is because when an object is quenched in water air bubbles form on the surface of the object reducing the surface area the water is in contact with. The salt in the brine reduces the formation of air bubbles on the object\’s surface, meaning there is a larger surface area of the object in contact with the water, providing faster cooling rates. Quench hardening is generally applicable to some ferrous alloys, but not copper alloys.
The Hardening Processes
In this process steels which contain sufficient carbon, and perhaps other alloying elements, are cooled (quenched) sufficiently rapidly from above the transformation temperature to produce Martensitic, the hard phase already described, see Curve 1
There is a range of quenching media of varying severity, water or brine being the most severe, through oil and synthetic products to air which is the least severe.
Tempering
After quenching the steel is hard, brittle and internally stressed. Before use, it is usually necessary to reduce these stresses and increase toughness by \’tempering\’. There will also be a reduction in hardness and the selection of tempering temperature dictates the final properties. Tempering curves, which are plots of hardness against tempering temperature. Exist for all commercial steels and are used to select the correct tempering temperature. As a rule of thumb, within the tempering range for a particular steel, the higher the tempering temperature the lower the final hardness but the greater the toughness.
It should be noted that not all steels will respond to all heat treatment processes.
Thermochemical Processes
These involve the diffusion, to pre-determined depths into the steel surface, of carbon, nitrogen and, less commonly, boron. These elements may be added individually or in combination and the result is a surface with desirable properties and of radically different composition to the bulk.
Carburising
Carbon diffusion (carburising) produces a higher carbon steel composition on the part surface. It is usually necessary to harden both this layer and the substrate after carburising.
Nitrating
Nitrogen diffusion (nitrating) and boron diffusion (boronising or boriding) both produce hard intermetallic compounds at the surface. These layers are intrinsically hard and do not need heat treatment themselves. Nitrogen diffusion (nitrating) is often carried out at or below the tempering temperature of the steels used. Hence they can be hardened prior to nitrating and the nitrating can also be used as a temper.
Boronising
Boronised substrates will often require heat treatment to restore mechanical properties. As borides degrade in atmospheres which contain oxygen, even when combined as CO or C02, they must be heat treated in vacuum, nitrogen or nitrogen/hydrogen atmospheres.
Processing Methods
In the past the thermochemical processes were carried out by pack cementation or salt bath processes. These are now largely replaced, on product quality and environmental grounds, by gas and plasma techniques. The exception is boronising, for which a safe production scale gaseous route has yet to be developed and pack cementation is likely to remain the only viable route for the for some time to come.
The gas processes are usually carried out in the now almost universal seal quench furnace, and any subsequent heat treatment is readily carried out immediately without taking the work out of the furnace. This reduced handling is a cost and quality benefit
TASK 8 LIQUID PROCESSING METHOD OF CAST IRON
DIE CASTING
Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process. Casting materials are usually metals or various cold setting materials that cure after mixing two or more components together; examples are epoxy, concrete, plaster and clay. Casting is most often used for making complex shapes that would be otherwise difficult or uneconomical to make by other methods.
Metal casting is one of the most common casting processes. Metal patterns are more expensive but are more dimensionally stable and durable. Metallic patterns are used where repetitive production of castings is required in large quantities.
Plaster and other chemical curing materials such as concrete and plastic resin may be cast using single-use waste molds as noted above, multiple-use \’piece\’ molds, or molds made of small rigid pieces or of flexible material such as latex rubber (which is in turn supported by an exterior mold). When casting plaster or concrete, the material surface is flat and lacks transparency. Often topical treatments are applied to the surface. For example, painting and etching can be used in a way that give the appearance of metal or stone. Alternatively, the material is altered in its initial casting process and may contain colored sand so as to give an appearance of stone. By casting concrete, rather than plaster, it is possible to create sculptures, fountains, or seating for outdoor use. A simulation of high-quality marble may be made using certain chemically-set plastic resins (for example epoxy or polyester) with powdered stone added for coloration, often with multiple colors worked in. The latter is a common means of making washstands, washstand tops and shower stalls, with the skilled working of multiple colors resulting in simulated staining patterns as is often found in natural marble or travertine. Casting process simulation uses numerical methods to calculate cast component quality considering mold filling, solidification and cooling, and provides a quantitative prediction of casting mechanical properties, thermal stresses and distortion. Simulation accurately describes a cast component’s quality up-front before production starts. The casting rigging can be designed with respect to the required component properties. This has benefits beyond a reduction in pre-production sampling, as the precise layout of the complete casting system also leads to energy, material, and tooling savings.
MECHANICAL PROCESSING OF IRON
Extrusions a process used to create objects of a fixed cross-sectional profile. A material is pushed through a die (a certain manufacturing tool) of the desired cross-section. The two main advantages of this process over other manufacturing processes are its ability to create very complex cross-sections, and to work materials that are brittle, because the only encounters compressive and shear stresses. It also forms parts with an excellent surface finish. Drawing is a similar process, which uses the tensile strength of the material to pull it through the die. This limits the amount of change which can be performed in one step, so it is limited to simpler shapes, and multiple stages are usually needed. Drawing is the main way to produce wire. Metal bar and tube are also often drawn.
Extrusion may be continuous (theoretically producing indefinitely long material) or semi-continuous (producing many pieces). The extrusion process can be done with the material hot or cold. Commonly extruded materials include metals, polymers, ceramics, concrete, play dough, and foodstuffs. The products of extrusion are generally called “extrudates”.
Hollow cavities within extruded material cannot be produced using a simple flat extrusion die, because there would be no way to support the center barrier of the die. Instead, the die assumes the shape of a block with depth, beginning first with a shape profile that supports the center section. The die shape then internally changes along its length into the final shape, with the suspended center pieces supported from the back of the die.
The material flows around the supports and fuses together to create the desired closed shape. The extrusion process in metals may also increase the strength of the material.
POWDER TECHIQUES
In this process, metal powder is poured into the mould and pressed with a die into the required shape. The powder is heated and pressurised so that the particles fuse.
The structure produced is porous because granules do not melt completely but become sintered leaving gaps between them. The end product may a course sinter or a fine sinter. Bronze bearing bushes which retain lubricants in the porous structure are produced this way. Steel components such as shaft couplings are made this way. Very hard materials such as tungsten carbide may be formed into cutting tool tips by this method.