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Topic 1.2.3 (Metal Classification)
Metals are made up of crystals that contain atoms and molecules.
Metals have been used for thousands of years in the form of Copper, Bronze and Iron.
Metal Facts:
Metal Facts:
Metals have good strength in both compression and tension, due to the very strong metallic bonds holding the atoms together.
These metallic bonds also allow free electrons to be shared amongst molecules making metals good conductors of heat and electricity.
All metals are extracted from Ores which are found in the earth.
As a result, they are considered a finite material (one day they will run out).
Ores need to be processed in order to extract the metal from the other minerals, rocks and soil.
25% of the Earth’s crust is made up of metal ores with Aluminium (Bauxite) being the most common followed by Iron.
Gold is the only metal that can be found in a usable form while the rest have to be processed.
The metals produced do not always reflect the name of the ore:
Metal materials such as Aluminum and Steel are considered more modern developments.
Steel:
Steel:
Steel is obtained from iron ore through a process involving a blast furnace. In this method, iron ore, known for its ease of separation, is melted, leaving behind the waste, or slag, which rises to the top during the process. This separation is a fundamental step in the production of steel, where the extracted iron ore transforms into a versatile and robust material that is integral to various industries.
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As we've come to understand, metals are broadly classified into two categories:
Ferrous metals, which contain Iron (Fe).
Non-ferrous metals, which do not contain Iron.
While technically, iron is the sole ferrous metal, it can be alloyed with other elements to create various metals. When iron is extracted from its ore, it is referred to as Pig Iron. This form of iron has a high carbon content (3.5-4.5%), making it extremely brittle and unsuitable as a construction material. Typically, pig iron is swiftly transferred within a foundry while molten to undergo the transformation into steel. Alternatively, it may be cast into ingots for transportation to other facilities for further processing.
Iron is a naturally occurring element.
Steel is an alloy of Iron and carbon which does not occur naturally.
Steel has better tensile strength and is significantly tougher than Iron
Ingot.
Ferrous Metals
Ferrous Metals
Ferrous metals, characterized by their iron and carbon content, exhibit magnetic properties and are prone to rusting over time when exposed to oxygen and water.
Cast Iron
Cast Iron is essentially liquefied Pig Iron poured into a mold, containing up to 3.5% carbon and silica. In its natural state, it tends to be brittle, unless subjected to heat treatment, rendering it malleable. This versatile material finds applications in crafting anvils and casting engine casings.
Mild Steel
Mild Steel, often referred to as Bright Drawn Mild Steel (BDMS), finds widespread application in metal construction, serving purposes ranging from building girders and refrigerator casings to car bodies and table legs. It is essentially composed of iron with a carbon content ranging from 0.15% to 0.3%.
Medium Carbon Steel
Medium Carbon Steel is also known as 'Tool Steel'. When 0.3-0.7% Carbon is incorporated, Medium Carbon Steel is formed, finding applications in springs, general gardening tools
High Carbon Steel
High Carbon Steel, containing 0.7-1.7% carbon, is commonly known as High-Speed Steel (HSS), and it finds applications in crafting tools, cutting tools, drilling bits, blades, and more. These high-carbon steel variations, often utilized in toolmaking, can also be classified as alloys.
Cast Iron:
With the addition of small amounts of carbon, iron is made stronger and classed as Steel.
As the carbon amount is increased so too are the hardness properties of the Steel.
Larger amounts of carbon (over 2%) render the iron brittle like Pug and Cast Iron.
One major disadvantage of using Iron is the fact that it oxidises. While all metals are prone to oxidization, in Iron it can be very destructive to the metal. Iron Oxide is better known as rust.
Unless treated, Iron and Steel will oxidise quickly forming a layer of Iron Oxide which can easily be brushed away and prevented by coating in a layer of oil.
If left untreated the oxide will begin to erode the surface of the metal and, although it can still be removed, it will leave noticeable marks in the metal. Eventually the oxide, or rust, will erode the metal away completely to an orange/brown powder.
Applications for Ferrous Metals:
True to their name, these metals lack iron, rendering them immune to rust. However, they boast distinct properties that make them well-suited for various applications. Precious metals like Gold, Silver, and Platinum are among the non-ferrous metal category.
Despite being the most abundant ore on Earth, the transformation of Bauxite into Aluminium poses challenges, demanding a substantial amount of energy. This difficulty in processing contributes to the higher cost of aluminium, often being 3-4 times more expensive than steel. Nevertheless, aluminium offers an excellent strength-to-weight ratio, making it robust despite its relatively lightweight nature.
Non-Ferrous Metals
Non-Ferrous Metals
Non-ferrous metals, which do not contain iron, are also found in the Earth as chemical compounds.
Aluminium
Aluminium, weighing one-third of steel, exhibits roughly half the strength with a melting point of 660 degrees C, showcasing a notable 'strength to weight ratio.' While sacrificing some strength, you gain the advantage of a material two-thirds lighter for a comparable size. This characteristic makes aluminium a favoured choice, especially in outdoor applications where corrosion resistance is crucial. Its lightweight nature also makes it popular for sports and camping gear, emphasizing portability.
Additionally, aluminium's excellent heat conductivity renders it suitable for diverse applications. It is widely used in cooking utensils and serves as a material for heat sinks and electrical casings, such as those in iPods, iPads, MacBooks, etc., aiding in the efficient dissipation of heat.
Copper
Producing copper is challenging and costly, contributing to its increasing market price. Similar to aluminium, the manufacturing process for copper involves electrolysis, a method shared with tin and zinc production.
Copper's exceptional conductivity for both heat and electricity makes it a preferred material for applications in electrical circuits, plumbing, and the production of electric and data cables. Even in areas without fibre optic broadband, copper continues to play a vital role in bringing the internet into homes.
Remarkably, copper undergoes melting at a high temperature of 1083 degrees C.
Tin
Pure tin is seldom employed in its unaltered form; instead, it has found applications in various forms. Historically used in food wrapping or foil (now largely replaced by aluminium), tin is commonly used as a coating for steel plates in the manufacturing of food cans. Additionally, it is blended with lead to create solder used in electrical circuits. Tin has a melting point of 232 degrees C.
Lead
Lead, known for its softness and significant weight, exhibits exceptional resistance to chemicals and acts as an effective barrier for various wavelengths, including X-rays. Common applications include lining containers for radioactive materials and serving as flashing in building structures where the roof meets the wall. It has a relatively low melting point melts at 330 degrees C.
Zinc
Zinc is primarily employed for the process of galvanizing, which involves coating steel. This protective layer is commonly applied to steel support beams, outdoor equipment like buckets and wheelbarrows, and storage bins. Additionally, zinc is utilized in die-casting processes to create intricate products such as lock mechanisms and small gears, showcasing its versatility in manufacturing. It melts at 419 degrees C.
Titanium
Titanium is categorized as a contemporary material due to its exceptional characteristics. With the highest strength-to-weight ratio among metals, it stands out for its cleanliness, making it well-suited for medical and surgical applications. Additionally, titanium is a popular choice in crafting performance sports equipment and spectacle frames. It melts at a temperature of 1675 degrees C.
Precious Metals:
Precious Metals:
Applications for Non-ferrous metals:
Activities
Make a list of all the metal items you encounter during the day from when you wake up until you go to bed. Find out the classification for each metal and name another product made from the same metal.
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