Scrap consists of recyclable materials left over from product manufacturing and consumption, such as parts of vehicles, building supplies, and surplus materials. Unlike waste, scrap has monetary value, especially recovered metals, and non-metallic materials are also recovered for recycling.Scrap consists of recyclable materials left over from product manufacturing and consumption, such as parts of vehicles, building supplies, and surplus materials. Unlike waste, scrap has monetary value, especially recovered metals, and non-metallic materials are also recovered for recycling.Scrap consists of recyclable materials left over from product manufacturing and consumption, such as parts of vehicles, building supplies, and surplus materials. Unlike waste, scrap has monetary value, especially recovered metals, and non-metallic materials are also recovered for recycling. Scrap metal originates both in business and residential environments. Typically a scrapper will advertise their services to conveniently remove scrap metal for people who dont need it. Scrap is often taken to a wrecking yard (also known as a scrapyard, junkyard, or breakers yard), where it is processed for later melting into new products. A wrecking yard, depending on its location, may allow customers to browse their lot and purchase items before they are sent to the smelters, although many scrap yards that deal in large quantities of scrap usually do not, often selling entire units such as engines or machinery by weight with no regard to their functional status. Customers are typically required to supply all of their own tools and labor to extract parts, and some scrapyards may first require waiving liability for personal injury before entering. Many scrapyards also sell bulk metals (stainless steel, etc.) by weight, often at prices substantially below the retail purchasing costs of similar pieces. In contrast to wrecking yards, scrapyards typically sell everything by weight, rather than by item. To the scrapyard, the primary value of the scrap is what the smelter will give them for it, rather than the value of whatever shape the metal may be in. An auto wrecker, on the other hand, would price exactly the same scrap based on what the item does, regardless of what it weighs. Typically, if a wrecker cannot sell something above the value of the metal in it, they would then take it to the scrapyard and sell it by weight. Equipment containing parts of various metals can often be purchased at a price below that of either of the metals, due to saving the scrapyard the labor of separating the metals before shipping them to be recycled.
Scrap can be divided into three categories depending on origin:
- Internal scrap is scrap that falls to the floor within the plants during steel production and that is directly recovered for the production process.
- **This scrap has the advantage that its precise content is known.
- Engineering workshop scrap is the scrap that arises during the working of steel in workshops, within the construction industry, on bridge building etc.
- Scrap metal collection is the scrap collected from end-of-life products e.g. on demolition of structures and installations and from households.
- The scrap may include everything from bridge beams to household utensils
Great potential exists in the scrap metal industry for accidents in which a hazardous material present in scrap causes death, injury, or environmental damage. A classic example is radioactivity in scrap; the Goiânia accident and the Mayapuri radiological accident were incidents involving radioactive materials. Toxic materials such as asbestos or metals such as beryllium, cadmium, or mercury may pose dangers to personnel, as well as contaminating materials intended for metal smelters.
Many specialized tools used in scrapyards are hazardous, such as the alligator shear which cuts metal using hydraulic force, compactors, and heavy-duty shredder machines.
An ingot is a piece of relatively pure material, usually metal, that is cast into a shape suitable for further processing. In steelmaking, it is the first step among semi-finished casting products. Ingots usually require a second procedure of shaping, such as cold/hot working, cutting, or milling to produce a useful final product. Non-metallic and semiconductor materials prepared in bulk form may also be referred to as ingots, particularly when cast by mold based methods. Ingots are manufactured by the freezing of a molten liquid (known as the melt) in a mold. The manufacture of ingots has several aims. Firstly, the mold is designed to completely solidify and form an appropriate grain structure required for later processing, as the structure formed by the freezing melt controls the physical properties of the material. Secondly, the shape and size of the mold is designed to allow for ease of ingot handling and downstream processing. Finally the mold is designed to minimize melt wastage and aid ejection of the ingot, as losing either melt or ingot increases manufacturing costs of finished products. A variety of designs exist for the mold, which may be selected to suit the physical properties of the liquid melt and the solidification process. Molds may exist in top, horizontal or bottom-up pouring and may be fluted or flat walled. The fluted design increases heat transfer owing to a larger contact area. Molds may be either solid massive design, sand cast (e.g. for pig iron) or water-cooled shells, depending upon heat transfer requirements. Ingot molds are tapered to prevent the formation of cracks due to uneven cooling. Crack or void formation occurs as the liquid to solid transition has an associated volume change for a constant mass of material. Formation of these ingot defects may render the cast ingot useless, and may need to be re-melted, recycled or discarded.
For a top-poured ingot, as the liquid cools within the mold, differential volume effects cause the top of the liquid to recede leaving a curved surface at the mold top which may eventually be required to be machined from the ingot. The mold cooling effect creates an advancing solidification front, which has several associated zones, closer to the wall there is a solid zone which draws heat from the solidifying melt, for alloys there may exist a mushy zone, which is the result of solid-liquid equilibrium regions in the alloys phase diagram, and a liquid region. The rate of front advancement controls the time that dendrites or nuclei have to form in the solidification region. The width of the mushy zone in an alloy may be controlled by tuning the heat transfer properties of the mold, or adjusting the liquid melt alloy compositions. Continuous casting methods for ingot processing also exist, whereby a stationary front of solidification is formed by the continual take-off of cooled solid material, and the addition of molten liquid to the casting process. Approximately 70% of aluminium ingots in the U.S. are cast using the direct chill casting process, which reduces cracking. A total of 5 percent of ingots must be scrapped because of stress induced cracks and butt deformation.
Blade materials are those used to make the blade of a knife or other simple edged hand tool or weapon, such as a hatchet or sword. The blade of a knife can be made from a variety of materials, the most common being carbon steel, stainless steel, tool steel and alloy steel. Other less common materials used in knife blades include: cobalt and titanium alloys, ceramics, obsidian, and plastic. The hardness of steel is usually stated as a number on the Rockwell C scale (HRC). The Rockwell scale is a hardness scale based on the resistance to indentation of a material, as opposed to other scales such as the Mohs scale (scratch resistance) testing used in mineralogy. As hardness increases, the blade becomes capable of taking and holding a better edge, but is more difficult to sharpen and more brittle (commonly called less "tough"). Laminating a harder steel between a softer one is an expensive process that to some extent gives the benefits of both types.
Common blade alloying elements:
- Carbon (C)
Increases edge retention and raises tensile strength.
Increases hardness and improves resistance to wear and abrasion.
- Chromium (Cr) Increases hardness, tensile strength, and toughness. Provides and increases resistance to wear, heat and corrosion. More than 12% makes it stainless, by causing an oxide coating to form. Carbide inclusions reduce wear, but bulk material is softer.
- Cobalt (Co)
Increases strength and hardness, and permits quenching in higher temperatures.
Intensifies the individual effects of other elements in more complex steels.
Increases resistance to corrosion.
- Copper (Cu)
- Manganese (Mn) Increases hardenability, wear resistance, and tensile strength. Deoxidizes and degasifies to remove oxygen from molten metal. In larger quantities, increases hardness and brittleness. Increases or decreases corrosion resistance depending on type and grade of steel or stainless steel.
- Molybdenum (Mo) Increases strength, hardness, hardenability, and toughness. Improves machinability and resistance to corrosion.
- Nickel (Ni) Adds toughness. Improves corrosion and heat resistance. Reduces hardness. Too much prevents hardening by heat-treatment.
- Niobium (Nb) Restricts carbide grain growth. Increases machinability. Creates hardest carbide. Increases strength,corrosion resistance and toughness.
- Nitrogen. Used in place of carbon for the steel matrix. The Nitrogen atom will function in a similar manner to the carbon atom but offers unusual advantages in corrosion resistance.
- Phosphorus (P) Improves strength, machinability, and hardness. Creates brittleness in high concentrations.
- Silicon (Si) Increases strength, corrosion and heat resistance. Deoxidizes and degasifies to remove oxygen from molten metal.
- Sulfur (S) Improves machinability when added in minute quantities. Usually considered a contaminant.
- Tungsten (W) Adds strength, toughness, and improves hardenability. Retains hardness at elevated temperature. Improves corrosion and heat resistance.
- Vanadium (V) Increases strength, wear resistance, and increases toughness. Improves corrosion resistance by contributing to the oxide coating. Carbide inclusions are very hard. Expensive. Chips frequently.
End user steel:
Iron and steel are used widely in the construction of roads, railways, other infrastructure, appliances, and buildings. Most large modern structures, such as stadiums and skyscrapers, bridges, and airports, are supported by a steel skeleton. Even those with a concrete structure employ steel for reinforcing. In addition, it sees widespread use in major appliances and cars. Despite growth in usage of aluminium, it is still the main material for car bodies. Steel is used in a variety of other construction materials, such as bolts, nails, and screws and other household products and cooking utensils. Other common applications include shipbuilding, pipelines, mining, offshore construction, aerospace, white goods (e.g. washing machines), heavy equipment such as bulldozers, office furniture, steel wool, tools, and armour in the form of personal vests or vehicle armour (better known as rolled homogeneous armour in this role). With the advent of speedier and thriftier production methods, steel has become easier to obtain and much cheaper. It has replaced wrought iron for a multitude of purposes. However, the availability of plastics in the latter part of the 20th century allowed these materials to replace steel in some applications due to their lower fabrication cost and weight. Carbon fiber is replacing steel in some cost insensitive applications such as aircraft, sports equipment and high end automobiles.