TYPES of MATERIALS: understand the physical and working properties of:
PLASTICS -
Plastic is defined as a material that contains an essential ingredient an organic substance of large molecular weight. It is also defined as polymers of long carbon chains. Carbon atoms are linked in chains and are produced in long-chain molecules.
Compared to metal, plastic has a low melting point, is highly malleable, and can be molded easily into basic or complex forms. That malleability also increases the fabrication and production of parts and pieces.
Properties of Plastic
They are light in weight and are chemically stable.
Easily moulded into different shapes and sizes.
Good insulation and low thermal conductivity.
Good impact resistance and they do not rust.
Good transparency and wear resistance.
Poor dimensional stability and can be easily deformed.
WOODS -
Wood is a structural tissue found in the stems and roots of trees and other woody plants. It is an organic material – a natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin that resists compression.
The mechanical properties of wood include strength in tension and compression (as measured in axial and transverse directions), shear, cleavage, hardness, static bending, and shock (impact bending and toughness).
METALS -
A solid material which is typically hard, shiny, malleable, fusible, and ductile, with good electrical and thermal conductivity (e.g. iron, gold, silver, and aluminium, and alloys such as steel).
Properties of metals
high melting points.
good conductors of electricity.
good conductors of heat.
high density.
malleable.
ductile.
APPLICATIONS -
METALS
construction.
electronic devices.
transportation.
food processing.
biomedical applications.
APPLICATIONS -
PLASTICS
Plastic is used across almost every sector, including to produce packaging, in building and construction, in textiles, consumer products, transportation, electrical and electronics and industrial machinery.
APPLICATIONS -
WOOD
In addition to well-known products such as lumber, furniture, and plywood, wood is the raw material for wood-based panels, pulp and paper, and many chemical products. Finally, wood is still an important fuel in much of the world.
SMART and MODERN MATERIALS: develop an awareness and understanding of ‘smart’ and modern materials, including:
THERMOCHROMIC MATERIALS -
Thermochromic materials are mainly used as temperature indicators in many industrial sectors, to determine the temperature variation and reaction heat in chemical reactions, to measure temperature distribution of chemical heating apparatus such as heat exchangers and reactors, and to indicate the temperature variation.
PLOYMORPH -
Polymorph is a thermoplastic material that can be shaped and reshaped any number of times. It is normally supplied as granules that look like small plastic beads. It can be heated in hot water and when it reaches 62 degrees centigrade the granules form a mass of 'clear' material.
SHAPE MEMORY ALLOYS (SMA) -
Shape memory alloys (SMAs) possess both sensing and actuating functions due to their shape memory effect, pseudo-elasticity, high damping capability and other remarkable properties. Combining the SMAs with other materials can create intelligent or smart composites by utilizing the unique properties of SMAs.
SHAPE MEMORY POLYMER (ACRYLIC) -
Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape when induced by an external stimulus (trigger), such as temperature change. Note: Crystalline trans-polyisoprene is an example of a shape-memory polymer.
PLASTICS - show a working knowledge of the following:
THERMOPLASTICS: Thermoplastics are defined as polymers that can be melted and recast almost indefinitely. They are molten when heated and harden upon cooling. When frozen, however, a thermoplastic becomes glass-like and subject to fracture.
NYLON -
Nylon is a tough thermoplastic with outstanding wear properties. Nylon is easy to machine and has high abrasion and impact resistance. It has excellent tensile and compressive strength and is an excellent electrical insulator.
LOW DENSITY POLYETHYLENE [LDPE] -
Low Density Polyethylene (LDPE) is a flexible, odorless, transparent, 100% recyclable thermoplastic polymer popular in products like grocery/garbage bags, juice containers, and cling wrap. Its flexibility, toughness, and corrosion resistance combined with its low-cost, high-efficiency production process make it an appealing choice for engineering applications, fueling demand for the production of millions of tons of LDPE each year.
HIGH DENSITY POLYETHYLENE [HDPE] -
High Density Polyethylene is a polyethylene thermoplastic made from petroleum. HDPE is commonly recycled and made into composite wood or plastic lumber. HDPE is a Type 2 plastic commonly used in making containers for milk, motor oil, shampoos and conditioners, soap bottles, detergents, and bleaches.
PLOYETHYLENE TEREPHALATE [PET] -
PET (also abbreviated PETE) is short for polyethylene terephthalate, the chemical name for polyester. PET is a clear, strong, and lightweight plastic that is widely used for packaging foods and beverages, especially convenience-sized soft drinks, juices and water.
POLYVINYL CHLORIDE [PVC] -
Polyvinyl chloride (PVC) is a synthetic resin made from the polymerization of vinyl chloride. PVC is a commonly used polymer that finds applications in a variety of products due to its excellent properties and low cost.
ACRLYIC [PMMA] -
PMMA or acrylic is a widely used transparent plastic material known for its applications in various markets from car windows, smartphone screens to aquariums. It is a tough plastic, easy to shape and a great alternative to the high cost and less resilient glass.
POLYSTYRENE [PS] -
Polystyrene is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a poor barrier to oxygen and water vapour and has a relatively low melting point.
POLYPROPYLENE [PP] -
Polypropylene (PP) is one of the most commonly used thermoplastics in the world. Polypropylene uses range from plastic packaging, plastic parts for machinery and equipment and even fibres and textiles.
ACRYLONITRILE-BUTADIENE-STYRENE [ABS] -
Acrylonitrile butadiene styrene, or ABS, is a common thermoplastic used to make light, rigid, molded products such as pipe, automotive body parts, wheel covers, enclosures, and protective head gear.
THERMOSETTING PLASTICS: Thermosetting plastics are made up from long chains of molecules that are cross-linked. They have a very rigid structure. Once heated, thermosetting plastics can be moulded, shaped and pressed into shapes. Once set they cannot be reheated since they are permanently set.
PLOYESTER RESIN -
Polyester resin (more loosely referred to as ‘laminating resin’ or ‘fibreglass resin’) is a polymer. Simple to use and economical, it is a major component in many industries, from construction to aerospace. Offering incredible physical and chemical properties, it’s also comparatively cheap compared to other resins like epoxies and urethanes, yet it offers similar – if not superior – performance in many cases.
The term ‘polyester resin’ largely refers to ‘unsaturated polyester resin’ unless otherwise specified.
GLASS REINFORCED POLYESTER [GRP] -
It is also called fibreglass, composite plastic or FRP. It is strong, extremely light and highly versatile. GRP behaves differently to the conventional thermoplastics that are used in everyday items.
MELAMINE FORMALDEYDE [MF] -
Is a hard, very durable, and versatile thermosetting aminoplastic with good fire and heat resistance. It is made from melamine and formaldehyde by condensation of the two monomers.
UREA FORMALDEHYDE [UF] -
Urea-formaldehyde, also known as urea-methanal, so named for its common synthesis pathway and overall structure, is a nontransparent thermosetting resin or polymer. It is produced from urea and formaldehyde. These resins are used in adhesives, plywood, particle board, medium-density fibreboard, and molded objects.
PHENOL FORMALDEHYDE [PE] -
Phenol-formaldehyde resins make excellent wood adhesives for plywood and particleboard because they form chemical bonds with the phenol-like lignin component of wood. They are especially desirable for exterior plywood, owing to their good moisture resistance.
EPOXY RESIN -
Epoxy resins are a class of thermosetting polymers made from monomers that contain at least two epoxide groups. They provide strong adhesion, chemical resistance and other specialized properties. Due to these qualities, epoxy resins are used in a variety of consumer and industrial products.
DEMONSTRATE A WORKING KNOWLEDGE OF:
NATURAL TIMBERS -
Natural timber is categorised into two groups - hardwoods and softwoods. Hardwoods come from deciduous trees that have broad leaves that generally fall in autumn. Hardwoods are generally harder, more expensive, more durable and take longer to grow than softwoods.
CLASSIFICATIONS -
Natural timber is categorised into two groups - hardwoods and softwoods.
They can be further divided into two types : (a) Soft wood – Chir, Deodar, fir, koil, pine, spruce, etc. (b) Hard Wood – Babul, Mahogany, oak, sat, teak, etc.
PROPERTIES of SOFTWOOD -
Softwood comes from gymnosperms, which are seed-bearing evergreen trees such as pine, spruce, fir, cedar, juniper, redwood, and yew. As most evergreen trees tend to be less dense than deciduous trees, it is easier to cut them down. They also grow tall and straight, making it easier to cut long straight planks of wood.
A wood will be classified as a softwood if the seeds don't have any type of coating and are instead dropped to the ground and left to the elements.
Durability - Softwoods generally have a shorter service life than hardwoods in external applications as even after treatment they are often less durable and require more care and maintenance over their lifespan.
Strength - The lower density of softwood timber means it's weaker and less durable than hardwood, however there are some 'hard' softwood options with a higher density like Juniper and Yew.
Permeability - Permeability is a function of porosity. Softwoods, which do not have pores are known as non-porous woods. Since soft- woods have no pores, the difference between the earlywood and latewood zones in the growth ring occurs due to effects that the growing season has on the longitudinal tracheids (the dominant cell type in softwoods).
Hardness - Softwoods do not have vessels and therefore have a softer, less pronounced grain than hardwoods.
Toughness - Density: The lower density of softwood timber means it's weaker and less durable, however there are some 'hard' softwood options with a higher density like Juniper and Yew. Longevity: Softwood is less suitable for high traffic areas as it does not wear as well as hardwood over time.
Elasticity - They are flexible, lighter in weight and less dense than most hardwoods.
Workability - Softwood is easier to work with and can be used across a broad range of applications.
Weight - Softwoods are lighter than hardwoods, making them easier to transport.
PROPERTIES of HARDWOOD -
Hardwood comes from Angiosperms such as maple, oak, and walnut. These trees lose their leaves annually (deciduous or broad-leafed trees). As they grow slowly, hardwood has denser wood fibers (fiber tracheids and libriform fibers).
An interesting fact about hardwood is that some types of hardwood can’t float in water. For example, Black ironwood is perhaps the hardest and heaviest wood that sinks in water.
A wood will be classified as a hardwood if the seeds that the tree produces have a coating. These coatings can either take the shape of a fruit or a shell.
Durability - Hardwoods are naturally more durable as they come from slow-growing, broad-leaved trees. This means the timber has a higher density than softwoods, which gives them enhanced durability and strength.
Strength - Because of their condensed and more complex structure, hardwoods generally offer a superior level of strength and durability. The most common types of hardwoods include Oak, Teak, Sapele, Iroko and Meranti.
Permeability - Permeability is a function of porosity. Flow through hardwoods is much less dependent on pits interconnecting the cells and so drying has less effect on hardwood permeability than on softwoods.
Hardness - Because of their condensed and more complex structure, hardwoods generally offer a superior level of strength and durability. The term hard wood (as opposed to hardwood) is referring to a physical property of the wood itself: hardness. Hardness refers to the ability of the wood to resist indentation.
Toughness - Toughness in wood. Toughness is the resistance of a material to the propagation of cracks or crack-like defects which can ultimately lead to failure. Cracks cause local stress concentrations, the magnitudes of which are dependent on the size and shape of the crack. Toughness is the mechanical property that determines the wood strength when a force acts in a short time interval. Its value is determined in the bending impact test.
Elasticity - Hardwoods are more dense and less elastic.
Workability - Due to its density, hardwood tends to be a lot harder to work with during construction.
Weight - Hardwood is heavier and more durable than softwood, which is usually reserved for windows and framing. The weight difference between hardwood and softwood is noticeable. For example, oak weighs between 37 and 56 pounds per cubic foot while a cubic foot of pine weighs between 22 and 35 pounds.
USES -
Fuel - In the case of burning wood, stored potential energy (in the form of chemical energy) in the log is released due to heating by other excited atoms. Wood pellets and other agglomerated energy products are made from dried sawdust, shavings or wood powder, with the raw material being compressed under high pressure.
Construction - Wood is sustainable, renewable, and generally less energy-intensive to process compared to other construction materials, including concrete and steel. Wood is an available resource that is biodegradable and easy to dispose of.
Sawn Wood - Sawn timber is timber that is cut from logs into different shapes and sizes. Sawn timber is generally cut into varying rectangular widths and lengths, but may also be wedge shaped. Common sawn timber products include solid timber beams and more rectangular timber sections.
Plywood and Veneers - Plywood is a type of manufactured wood panel that's made by gluing veneers together. The layers are glued with the wood grain of the plies at right angles to each other. Veneers are the thin slices of wood that can be peeled off and they're usually less than ⅛ inch thick.
Fibreboards - Fibreboard is an engineered wood wallboard made of wood chips, plant fibres, softwood flakes, sawdust and other recycled materials such as cardboard or paper, all bonded with a synthetic resin under high pressure and heat and then compacted into rigid sheets.
Pulp & Paper - Pulp is made from breaking down the fibrous part of plants, primarily trees or recycled paper, and refers to the main ingredient in the papermaking process. Pulp made from trees (wood fiber) is the most common source of fiber for papermaking and the base for many paper and wood products.
Synthetic Textiles - In the fast-growing next-gen materials market, cellulose fibers extracted from wood, old textiles, and even bacteria are performing akin to cotton, silk, and polyester.
UNDERSTAND:
WHY TIMBER IS SEASONED -
Timber seasoning is the process of reducing moisture content from timber. This can be achieved in a few different ways, with kiln and air seasoning being the most common. If left unseasoned, timber can quickly warp, twist, and break as too much moisture wreaks havoc on the cellular structure.
HOW TO CARE FOR TIMBER DURING STORAGE AND CONSTRUCTION -
How can we protect timber in construction?
Pressure treatment is the most effective way of protecting timber used in external applications. The process involves placing the timber inside a high pressure vacuum cylinder where specialised chemicals are then forced deep into the wood.
Timber must be stored vertically, and on a flat surface to help it absorb air. The surface should be stable and evenly structured to prevent the timber from sinking in. Your timber is likely to warp if stored in an area that is not flat or solid. Instead of storing it on the floor, place it on pallets.
UNDERSTAND:
STEAMING TIMBER AND BENDING TIMBERS -
Steam bending is the process of soaking a piece of wood in hot water at boiling point for a certain period of time in a steam box, softening the fibres to make it pliable and stretchier. Once the timber cools down and the fibres dry once more, it will retain its new shape.
ADHESIVES' CURING TIMES AND STRENGTHS -
Curing refers to a chemical reaction that occurs during the application or use of the adhesive. It is the result of two-components reacting or cross-linking, resulting in a physical change from a liquid to a solid. This process is irreversible.
Cure time is the time that determines how long things take to fully cure. A series of chemical reactions occurs during cure time. These chemical reactions allow things to set, harden and develop traits. It may take weeks, months or years. Many factors have an impact on the curing time of a product.
Adhesive strength refers to the ability of an adhesive to stick to a surface and bond two surfaces together. It is measured by assessing the maximum tensile stress needed to detach or unstick the adhesive perpendicular to the substrate.
Polyvinyl Acetate Glue (PVA) - The most common type of wood glue is polyvinyl acetate (PVA). This is the modern wood glue that replaced hide glue.
There are several benefits to PVA wood glue.
One of the biggest benefits is that PVA wood glue is the most popular wood glue around and is easy to purchase at most every large retail store, from Home Depot to Walmart.
Some glues will change color with time, such as regular Elmer's glue, which is a PVA glue but not intended for wood and generally a weaker solution, but some will use it for small projects. But PVA wood glue won't yellow over time, and it will stay somewhat flexible, and this helps keep the sheer strength strong over time.
The fumes are not foul or harmful, and the glue is only toxic if you ingest it. I strongly suggest you make sure not to ingest PVA glue.
There has been little to no breakdown over the years with PVA wood glue, although if the glue-up is poor quality, it will still come apart.
Polyurethane Glue - Polyurethane glue has a very strong adhesion if used correctly.
Benefits of Polyurethane Glue
Some of the benefits of polyurethane glue are that it doesn't have a high moisture content and doesn't make the joint swell like some water-based glues do. This is because polyurethane glue is not water-based, and wood pores don't draw this type of glue in as much.
An interesting aspect of polyurethane glue is that you can still glue together finished pieces instead of having to glue the piece together first and then finish it. This is because the bond doesn't require an uptake into the wood pores and adheres the pieces together differently than other types of glue.
Another unique feature of polyurethane glue is that the glue cures from a chemical reaction to moisture. This makes gluing wood with a high moisture content or oily wood easier to glue over a glue such as PVA, which would have difficulty bonding these types of surfaces at all.
Cyanoacrylate Glue - Cyanoacrylate (CA) glue is most popular as super glue, but this is not the extent of CA glue.
The holding properties are good, but the sheer strength is not the best.
These glues are great for gluing wedges to pieces and using them for clamping assistance, then, because the sheer strength is low, you can hit them with a mallet and pop them off when the adhesive has dried.
This type of glue can be used for general-purpose gluing, but it is more expensive than PVA and other glues.
This is a glue that is great for crown molding, trim, and furniture repair because it is clear and can cure quickly.
Animal or Hide Glue - Hide glue is the original glue. This is still widely used for bow making, instruments, and traditional woodworkers. Hide glue, animal glue, and rawhide glue are one and the same, but the term hide glue is more common. Hide glue is easiest enough to make as well, although there are synthetic hide glues on the market.
Epoxy Glue - Epoxy glue is another strong adhesive. This type of glue is a two-part mixture that has a chemical reaction when combined. Both of these parts are liquids.
Benefits of Epoxy
Epoxy is waterproof and makes a good filler as well.
The cure times for epoxy can vary a great deal, but a general rule of thumb is the longer it takes to cure, the stronger the bond is. This is an advantage that epoxy has over PVA glue.
Epoxy is a good choice if your joint is off and needs a little filling; you can mix sawdust into the mixture for the wood texture.
DEMONSTRATE A WORKING KNOWLEDGE OF THE FOLLOWING MANUFACTURED BOARDS:
PLYWOOD -
Plywood belongs to a class of materials referred to as composite wood materials or wood resin boards. The other wood products included in this category are particle board, fiber board, wafer board, and strand board. Phenolic resins serve as the bonding material in these products.
What is plywood used for?
The most prominent use of plywood is in structural applications. Plywood can naturally withstand a lot of stress and full weather exposure. Structural plywood is best used for beams and hoardings, but it is commonly used in crates, bins, internal structures, outdoor furniture, and boxes.
The 10 Biggest Benefits of Plywood:
Plywood is strong. ...
Plywood is durable. ...
Plywood is lightweight. ...
Plywood covers a much bigger area. ...
Plywood is more pliable and great for curved surfaces. ...
Plywood can also be treated for fire prevention or moisture problems. ...
Plywood is eco-friendly.
BLOCKBOARD -
Blockboard is a type of plywood that is engineered in a special way. It is pressured in such a way that the softwood strips are found between two layers of the wood veneers in the core of the sheet. This contributes to the dimensional stability of the board.
What is block board used for?
Blockboard is generally used for building long book shelves, tables and benches, single and double beds, settees, and lengthy wall panels. It is light in weight, and is used extensively for building interior and exterior doors.
Advantages of Blockboard
The stability of block boards are well enough stability, These can even show stability in humid environment those have moisture resistance. They are inexpensive. It can take varnish, paint, and laminate coat on the surface by using glue. Block boards are good for screwing and nailing.
CHIPBOARD -
Particle board, also known as chipboard, is an engineered wood product that is pressed and extruded from wood chips or jute-stick chips and a synthetic resin or another appropriate binder. Particle board is frequently confused with oriented strand board, a different type of fiberboard that is stronger and uses machined wood flakes.
Chipboard flooring
Chipboard flooring is a type of subflooring made of coarse sawdust mixed with resin. The sawdust-resin mixture is heated and pressed into large sheets. The small bits of sawdust that make up the flooring sheets are easily visible in chipboard, also known as particle board. Chipboard flooring is available in a variety of thicknesses, with each standard thickness color-coded for easy identification. Because it is inexpensive and durable, high-density chipboard is used for sub-flooring or as the foundation for carpet or other flooring surfaces.
MDF -
MDF is the abbreviation of Medium Density Fiberboard. 90% of MDF plates consist of wood. MDF, which is not readily available in nature, is a man-made wood material. It is obtained by compressing wood fibers through heat treatment.
MDF is always preferred in the production of bedroom furniture because chipboard is not a material that has the strength and quality to carry heavy loads. In addition, the appearance of a beautifully painted MDF is just like wood, it gives a very elegant appearance.
MDF has structural integrity, high ecological compatibility, so it has high machinability. It is versatile and has the advantage of being shaped. MDF sheets are available as MDF cut to size with various types and having different features.
UNDERSTAND:
THE ADVANTAGES OF WORKING WITH MANUFACTURED BOARDS COMPARED WITH SOLID WOOD -
Medium Density Fiberboard (MDF) and Plywood are the popular manufactured wood in furniture making. The aesthetic look, workability, screwing and nailing ability, smoothness of the surface, ease to paint, make a manufactured wood a better choice for furniture than any other wood type.
THE DISADVANTAGES OF WORKING WITH MANUFACTURED BOARDS COMPARED WITH SOLID WOOD -
Minimal resistance to moisture and humidity: Manufactured wood isn’t made to be resistant to moisture and humidity. There is a high risk of the material soaking up water.
Heavy and sturdy: Manufactured wood can be heavy and sturdy. While that’s not a bad thing, it makes it tricky to handle if you are just one person completing a project.
Veneers showing at the edges: The construction of manufactured wood may leave rough edges. These require more work to remove than natural wood.
Formaldehyde: Manufactured wood is often made with formaldehyde. When cut, the dust from manufactured wood can release carcinogens into the air. It can harm the user if proper precautions are not taken in the cutting process.
METALS - demonstrate a working knowledge of the following metals:
FERROUS METALS
CAST IRON -
Cast iron, an alloy of iron that contains 2 to 4 percent carbon, along with varying amounts of silicon and manganese and traces of impurities such as sulfur and phosphorus. It is made by reducing iron ore in a blast furnace.
MILD STEEL -
Mild steel is a type of carbon steel that contains a low level of carbon. Otherwise known as low carbon steel, mild steel contains roughly between 0.05% and 0.25% of carbon by weight. This is opposed to high carbon steel, which can be composed of up to 2.5% carbon by weight.
STAINLESS STEEL -
Like all other kinds of steel, stainless steel is made primarily from iron and carbon in a two-step process. What makes stainless steel different is the addition of chromium (Cr) and other alloying elements such as nickel (Ni) to create a corrosion-resistant product.
HIGH SPEED STEEL [HSS] -
An alloy tool steel which when heat-treated retains much of its hardness and toughness at red heat thus enabling tools made of it to cut at high speeds even though red-hot through friction.
CARBON STEELS -
Also called mild steel, it's commonly used structurally in buildings and bridges, axles, gears, shafts, rails, pipelines and couplings, cars, fridges and washing machines. High carbon steel has a much better tensile strength, used to make cutting tools, blades, punches, dies, springs and high-strength wire.
NON-FERROUS METALS
ALUMINIUM -
Aluminium is a silvery-white metal, the 13 element in the periodic table. One surprising fact about aluminium is that it's the most widespread metal on Earth, making up more than 8% of the Earth's core mass. It's also the third most common chemical element on our planet after oxygen and silicon.
DURALUMIN -
Duralumin is actually a metal, which is an alloy of aluminum, copper, magnesium, and manganese. Duralumin is a special kind of metal and is made strong by subjecting it to heat treatment. It may be well spun, tempered, riveted, welded, or machinated. The duralumin, which is effectively given heat treatment, can be effectively being resistant to corrosion. It can carry heavy loads and is ductile. It is especially suited for aircraft construction.
CASTING ALLOYS -
The most typical materials used for metal castings are aluminum, zinc, copper, ductile iron, gray iron, and steel.
Metal casting methods
Permanent molds - Permanent mold casting is a metal casting process that employs reusable molds, usually made from metal. The most common process uses gravity to fill the mold, however gas pressure or a vacuum are also used. A variation on the typical gravity casting process, called slush casting, produces hollow castings.
Semi-permanent molds - Semi-permanent mold is a casting process - producing Aluminum alloy castings - using re-usable metal molds and sand cores to form internal passages within the casting. Molds are typically arranged in two halves - the sand cores being put into place before the two halves are placed together.
Slush casting - Slush casting is a variant of permanent molding casting to create a hollow casting or hollow cast. In the process the material is poured into the mold and allowed to cool until a shell of material forms in the mold. The remaining liquid is then poured out to leave a hollow shell.
Centrifugal casting - The centrifugal casting method is the method to produce pipes by pouring molten metal into a rapidly spinning cylindrical mold in which centrifugal force from the rotation exerts pressure on the molten metal.
Pressure casting - Pressure casting, also known in manufacturing industry as low pressure casting or pressure pouring, is another variation of permanent mold casting. Instead of pouring the molten metal into the casting and allowing gravity to be the force that distributes the liquid material through the mold, pressure casting uses air pressure to force the metal through the gating system and the metal casting's cavity. This process can be used to cast high quality manufactured parts. Often steel castings are cast in graphite molds using this process. For example, in industry, steel railroad car wheels are cast with this method.
Die casting - Die casting is a metal casting process that involves feeding molten nonferrous alloys into dies under high pressure and at high speed to rapidly create molded products. The main materials used in die casting are alloys of aluminum, magnesium and zinc.
COPPER -
Copper is a chemical element with the symbol Cu and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orange color.
As copper is ductile and a great conductor, its main use is in electric generators, household/car electrical wiring, and the wires in appliances, computers, lights, motors, telephone cables, radios and TVs.
ZINC -
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 of the periodic table.
Most zinc is used to galvanise other metals, such as iron, to prevent rusting. Galvanised steel is used for car bodies, street lamp posts, safety barriers and suspension bridges.
Large quantities of zinc are used to produce die-castings, which are important in the automobile, electrical and hardware industries. Zinc is also used in alloys such as brass, nickel silver and aluminium solder.
Zinc oxide is widely used in the manufacture of very many products such as paints, rubber, cosmetics, pharmaceuticals, plastics, inks, soaps, batteries, textiles and electrical equipment. Zinc sulfide is used in making luminous paints, fluorescent lights and x-ray screens.
LEAD -
Lead is a chemical element with the symbol Pb and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, lead is a shiny gray with a hint of blue. It tarnishes to a dull gray color when exposed to air.
Lead is still widely used for car batteries, pigments, ammunition, cable sheathing, weights for lifting, weight belts for diving, lead crystal glass, radiation protection and in some solders. It is often used to store corrosive liquids.
TIN -
Tin is a chemical element with the symbol Sn and atomic number 50. Tin is a silvery-coloured metal. Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort.
It is a soft, silvery white metal with a bluish tinge, known to the ancients in bronze, an alloy with copper. Tin is widely used for plating steel cans used as food containers, in metals used for bearings, and in solder.
UNDERSTAND HOW THE FOLLOWING PROCESSES CAN CHANGE THE MOLECULAR STRUCTURE OF A MATERIAL MAKING IT MORE OR LESS SUITABLE FOR THE TASK IT HAS TO PERFORM:
WORK HARDENING -
Work hardening, in metallurgy, increase in hardness of a metal induced, deliberately or accidentally, by hammering, rolling, drawing, or other physical processes. Although the first few deformations imposed on metal by such treatment weaken it, its strength is increased by continued deformations.
The Stages of Work Hardening after Diehl, stage I/Easy Glide, stage II/Athermal Work Hardening and stage III/Dynamic Recovery.
An example of desirable work hardening is that which occurs in metalworking processes that intentionally induce plastic deformation to exact a shape change. These processes are known as cold working or cold forming processes.
ANNEALING OF ALL METALS -
Annealing steel or any other metal involves heating it to a specific temperature and allowing it to cool at a specified rate. Doing so removes impurities in the grain, increasing the metal's ductility and reducing its hardness.
While steel and alloy steel annealing is common, other metals can also benefit from the process, such as aluminium, brass, and copper.
What are the 3 types of annealing? Included in the list are: Complete Annealing. Isothermal Annealing. Incomplete Annealing.
During the annealing process, the metal is heated to a specific temperature where recrystallization can occur. At this stage, any defects caused by deformation of the metal are repaired. The metal is held at that temperature for a fixed period, then cooled down to room temperature.
CASE HARDENING OF MILD STEEL -
Case-hardening involves packing the low-carbon iron within a substance high in carbon, then heating this pack to encourage carbon migration into the surface of the iron. This forms a thin surface layer of higher carbon steel, with the carbon content gradually decreasing deeper from the surface.
What is case hardening of steel?
Case hardening is a material processing method that is used to increase the hardness of the outer surface of a metal. Case hardening results in a very thin layer of metal that is notably harder than the larger volume of metal underneath of the hardened layer.
HARDENING AND TEMPERING TOOL STEEL [HCS] -
Hardening and tempering of engineering steels is performed to provide components with mechanical properties suitable for their intended service. Steels are heated to their appropriate hardening temperature {usually between 800-900°C), held at temperature, then "quenched" (rapidly cooled), often in oil or water.
What is the difference between hardening and tempering of tool steel?
The maximum hardness of a steel grade, which is obtained by hardening, gives the material a low toughness. Tempering reduces the hardness in the material and increases the toughness. Through tempering you can adapt materials properties (hardness/toughness ratio) to a specified application.
What is hardening and tempering?
A treatment in which a part is subjected to two complete hardening operations, or first an annealing process followed by a hardening process. Tempering. Tempering is a low temperature heat treatment process normally performed after a hardening process in order to reach a desired hardness/toughness ratio.
COMPOSITES - show an understanding of the term composite and be aware of the practical applications for each of the following composite materials:
KEVLAR -
Kevlar (para-aramid) is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora. Developed by Stephanie Kwolek at DuPont in 1965, the high-strength material was first used commercially in the early 1970s as a replacement for steel in racing tires.
Kevlar is the most commonly used material as armour for protection against bullets used in hand guns because of its impact resistance, high strength and low weight. These properties make Kevlar an ideal material to be used in bullet-proof vests as compared to other materials.
The chemical structure of Kevlar® is comprised of several repeating inter-chain bonds. These chains are cross-linked with hydrogen bonds, providing a tensile strength 10X greater than steel on an equal weight basis.
CARBON FIBRE REINFORCED PLASTIC (CFRP) -
Carbon fiber composite materials, also known as carbon fiber reinforced plastics (CFRP), are composite materials made of carbon fibers and resin (mainly epoxy resin).
As light, strong, and hard materials, they are used in wide range of applications such as sporting goods, industrial, aircraft and automobile components. By selecting suitable resin, it is possible to add features like heat resistance, impact resistance, and flame retardant, and thus provide superior characteristics not found in conventional metals and ceramics to enable a reduction in the weight of parts, give freer design.
GLASS REINFORCED PLASTIC (GRP) -
GRP stands for Glass Reinforced Plastic or Glass Reinforced Polymer. It is a very versatile material, which has a huge number of applications and uses. GRP is also often referred to as fibreglass (fiberglass in the US) or glass fibre composite. GRP also belongs to a larger family of products known as FRP, or Fibre Reinforced Plastics.
GRP is made up of a combination of glass fibre and polymer or plastic.
It has many desirable properties which include:
High strength to weight ratio
Excellent durability
Lightweight
Electrically non-conductive
Radar/radio wave transparent
Non-corroding
These properties make for a very versatile composite material with many different applications. Fibreglass can offer significant advantages over other materials like concrete, steel, other metals. It’s also a more adaptable material than non-reinforced thermoplastics such as nylon, polypropylene, or ABS (Acrylonitrile butadiene styrene).