What are properties of steel?

Answer 1

Iron, like most metals, is found in the Earth's crust only in the form of an ore, ie. combined with other elements such as oxygen or sulfur.[2] Typical iron-containing minerals include Fe2O3-the form of iron oxide found as the mineral hematite, and FeS2-pyrite (fool's gold).[3] Iron is extracted from ore by removing oxygen and combining the ore with a preferred chemical partner such as carbon. This process, known as smelting, was first applied to metals with lower melting points, such as tin, which melts at approximately 250 °C (482 °F) and copper, which melts at approximately 1,000 °C (1,830 °F). In comparison, cast iron melts at approximately 1,370 °C (2,500 °F). All of these temperatures could be reached with ancient methods that have been used since the Bronze Age. Since the oxidation rate itself increases rapidly beyond 800 °C, it is important that smelting take place in a low-oxygen environment. Unlike copper and tin, liquid iron dissolves carbon quite readily. Smelting results in an alloy (pig iron) containing too much carbon to be called steel.[4] The excess carbon and other impurities are removed in a subsequent step.

Other materials are often added to the iron/carbon mixture to produce steel with desired properties. Nickel and manganese in steel add to its tensile strength and make austenite more chemically stable, chromium increases hardness and melting temperature, and vanadium also increases hardness while reducing the effects of metal fatigue. To prevent corrosion, at least 11% chromium is added to steel so that a hard oxide forms on the metal surface; this is known as stainless steel. Tungsten interferes with the formation of cementite, allowing martensite to form with slower quench rates, resulting in high speed steel. On the other hand, sulfur, nitrogen, and phosphorus make steel more brittle, so these commonly found elements must be removed from the ore during processing.[5]

The density of steel varies based on the alloying constituents, but usually ranges between 7.75 and 8.05 g/cm3 (0.280-0.291 lb/in3).[6]

Even in the narrow range of concentrations which make up steel, mixtures of carbon and iron can form a number of different structures, with very different properties. Understanding such properties is essential to making quality steel. At room temperature, the most stable form of iron is the body-centered cubic (BCC) structure α-ferrite. It is a fairly soft metallic material that can dissolve only a small concentration of carbon, no more than 0.021 wt% at 723 °C (1,333 °F), and only 0.005% at 0 °C (32 °F). If the steel contains more than 0.021% carbon then it transforms into a face-centered cubic (FCC) structure, called austenite or γ-iron. It is also soft and metallic but can dissolve considerably more carbon, as much as 2.1%[7] carbon at 1,148 °C (2,098 °F)), which reflects the upper carbon content of steel.[8]

When steels with less than 0.8% carbon, known as a hypoeutectoid steel, are cooled from an austenitic phase the mixture attempts to revert to the ferrite phase, resulting in an excess of carbon. One way for carbon to leave the austenite is for cementite to precipitate out of the mix, leaving behind iron that is pure enough to take the form of ferrite, resulting in a cementite-ferrite mixture. Cementite is a hard and brittle intermetallic compound with the chemical formula of Fe3C. At the eutectoid, 0.8% carbon, the cooled structure takes the form of pearlite, named after its resemblance to mother of pearl. For steels that have more than 0.8% carbon the cooled structure takes the form of pearlite and cementite.[9]

Perhaps the most important polymorphic form is martensite, a metastable phase which is significantly stronger than other steel phases. When the steel is in an austenitic phase and then quenched it forms into martensite, because the atoms "freeze" in place when the cell structure changes from FCC to BCC. Depending on the carbon content the martensitic phase takes different forms. Below approximately 0.2% carbon it takes an α ferrite BCC crystal form, but higher carbon contents take a body-centered tetragonal (BCT) structure. There is no thermal activation energy for the transformation from austenite to martensite. Moreover, there is no compositional change so the atoms generally retain their same neighbors.[10]

Martensite has a lower density than austenite does, so that transformation between them results in a change of volume. In this case, expansion occurs. Internal stresses from this expansion generally take the form of compression on the crystals of martensite and tension on the remaining ferrite, with a fair amount of shear on both constituents. If quenching is done improperly, the internal stresses can cause a part to shatter as it cools. At the very least, they cause internal work hardening and other microscopic imperfections. It is common for quench cracks to form when water quenched, although they may not always be visible.

Answer 2

There are a number of physical properties of steel. It is often used due for its good tensile strength (strenght under tension). It also has good compressional strenght. In fact it is strong under all types of stress. The more carbon you put in steel the harder it gets and the more brittle it gets. Steel if maluable so you can manipulate it into shape easily. It can be flexible (depending on how much carbon is in it. The more there is the less flexible it gets).

Answer 3

Steel has the following properties:LustreIt is a shiny metal with a very attractive finish (architecture, cutlery, appliances). ConductivityIt transfers heat and electricity (saucepans). MalleabilityIt can be rolled into thin sheets, rod, bar or beams (roofing, structural) or forged into different shapes (gears, tools). DuctilityIt can be stretched and drawn out into thin wires (wire fences) or pressed into different shapes (auto body panels). StrengthIt is very strong and resistant to fracture (building frames, security doors, trains, ships). DurabilityIt is a long lasting material (buildings, rail lines, bridges) and resistant to wear (machines and equipment). AlloyingAdding other chemicals can change steel's properties. Stainless steel contains the elements chromium, nickel and molybdenum to make it rust resistant for use in kitchens. Manganese is added to increase toughness, while steel for rods has tungsten and cobalt to keep it hard, even when it gets hot.

Answer 4

The propeties are:

1. One of the major property of steel is the ability to cool down rapidly from an extremely hot temperature after being subjected to water or oil.

2. Steel, as we all know, offers great strength though it is light in weight. In fact, the ratio of strength to weight for steel is the lowest than any other building material as of now.

3. Steel can easily be molded to form any desired shape.

4. Steel does not corrode easily, on being exposed to moisture and water. The dimensional stability of steel is a desired property, as the dimension of steel remains unchanged even after many years or being subjected to extreme environmental conditions.

5. Steel is a good conductor of electricity, i.e. electricity can pass through steel.

Answer 5

Steel is a metal alloy composed primarily of iron and carbon, with other elements such as manganese, chromium, or nickel added for different properties. It is strong, durable, and can be easily shaped through various processes such as forging, welding, and machining. Steel can also be heat treated to modify its hardness, strength, and other mechanical properties.

Answer 6

Steel cools down rapidly after being heated if put in water or oil

Answer 7

it is great wear resistance but ie is Brittle