Steel

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Steel is the most common iron-carbon alloy, widely used in construction and other common applications due of its high tensile strength and low cost.

For the amateur chemist, steel is the cheapest available form of iron.

Composition

Steel consists of iron with a carbon content of 0.002% and 2.1% by weight. This type of steel is commonly referred to as carbon steel, or more common plain steel. The addition of other elements gives steel interesting properties.

Types

There are 4 main types of steel, all which depend on composition and elements present.

  • Carbon steel: The most common type of steel, it consists of iron with a carbon content between 0.002% and 2.1%. It is a silvery-gray malleable tough solid, which can be hardened via heat treatment. It shows good resistance to air oxidation, but presence of moisture, acids and or salts will cause steel to oxidize, and the apparition of rust. Iron-carbon alloys with a carbon content higher than 2.1% are no longer called steel, but rather cast iron. Cast iron tends to be more brittle than plain steel, but has better resistance to corrosion.
  • Stainless steel: Contains between 10.5-26 % chromium by weight. This alloy is widely used in common appliances and construction due to its superior resistance to most reagents, and is resistant to rusting due to the formation of a very thin passivating layer or chromium oxide on its surface. Its mechanical properties are inferior to that of carbon steel, making stainless steel not suitable for most applications where high strength materials are required. It is also somewhat harder to properly weld than plain steel.
  • Alloy steel: Alloy steels are carbon steels which contain other metals in their composition in significant percentage, such as aluminium, chromium, cobalt, copper, manganese, nickel or titanium. Other non-metals, such as silicon can also be present. Alloy steels have better mechanical properties than carbon steel, though the exact properties differ from one steel to another, depending on the composition and elements present in the steel. While some alloy steels are used in some tools, they are not true tool steels.
  • Tool steel: Carbon steel alloys containing refractory metals, such as vanadium, chromium, molybdenum or tungsten. As the name suggests, this type of steel is commonly used in the manufacture of tools and parts used in applications where high stress and wear are encountered. The most common encountered is the chromium-vanadium alloy, and most tools made of this alloy will tend to have the designation "chromium-vanadium" or "Cr-V". Molybdenum-chromium steels are also used for special tools due to their superior mechanical properties and stress resistance, although tend to be less common than the Cr-V steels, as they're more expensive. Despite their chromium content, tool steels have lower corrosion resistance than stainless steel and rust much easier. These types of steels can be a good source of V, Cr, Mo and W for the amateur chemist.

Properties

Carbon steel is a silvery-gray tough solid material, which melts between 1370-1510 °C, melting point depends on the percentage of carbon. Steel will begin to soften above 500-600 °C. The density of mild steel is approximately 7850 kg/m3.

Availability

Steel can be found in a variety of every day objects, such as frames, screws, nails, needles, tools, pipes, wires, cables, rebars, supports, coat hangers, boxes, beams (I/H, T), various car and machine parts, etc. Some steel objects tend to be zinc-plated to increase resistance to corrosion, which normally would not be a problem, but if you need to weld galvanized steel, you will need to remove the zinc plating from the welding points.

Specific steel alloys can be purchased from metal companies, though some may only sell in bulk and not in small pieces.

Preparation

Steel is too cheap and common to make it yourself. If however, you need to make a specific alloy or simply experiment with new and unheard of steel alloys, you will first need to have basic metallurgy knowledge before doing anything.

Projects

  • Storage containers
  • Construction material for lab furniture and fittings
  • Make frames for holding glassware setups
  • Make retort
  • Make lab tools
  • Make chemical reactor
  • Cast steel objects
  • Make iron(III) oxide and other oxides
  • Make pyrophoric iron

Handling

Safety

Steel is harmless to touch, though inhaling iron dust (like when using an angle grinder) may be harmful. Injury from sharp rusted iron may lead to infection, as iron and iron compounds do not have antibacterial properties and the rough surface of rust allows a bacteria to develop. Contrary to popular belief, rusted nails do not normally cause tetanus, unless they've been previously contaminated with tetani bacteria, which normally lives in dirt. Since most people come in contact with rusted objects which entered in contact with dirt, this leads to the false conclusion that it's the rusted nails alone that cause tetanus.

Storage

Steel should be kept away from corrosive vapors and moisture, in dry areas. If rust begins to appear, you will need to remove it, otherwise the corrosion will spread.

Disposal

Steel is best taken to metal recycling centers, though small amounts can be dumped in trash.

References

Relevant Sciencemadness threads