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Steel Alloys

Steel alloys are steel with small amounts added of one or more other metals. Many different steel alloys exist for a wide range of uses. Like a cook flavoring a dish with a pinch of this spice and a pinch of that, a modern metallurgist will add bits of this and that metal to basic steel in order to get just the right properties.

All steel starts as iron. Iron itself changes a culture because it is much harder than the metals that were used before it (copper, lead, bronze). Yet, iron can still be worked with a hammer. Iron atoms will slip and slide around each other when subjected to force, unless a few atoms of carbon are introduced. The carbon jams up this motion; hence, steel.

Various metals can also be added to steel to change its properties. The properties of interest are usually hardness, strength, toughness, and corrosion resistance as well as durability in extreme environments such as intense heat. For example, a support beam will need strength, a bolt toughness, and a chisel hardness.

Some of the common alloying metals are as follows:

AlAluminum to give strong magnetism

BiBismuth improves machinability

CrChromium increases corrosion resistance

CuCopper increases corrosion resistance

MnManganese increases hardness and reduces brittleness

MoMolybdenum increases toughness

NiNickel increases corrosion resistance and toughness

WTungsten increases the melting point

VVanadium increases strength and toughness

For extreme-environment steels, see superalloys.

There is no perfect steel alloy. The design always involves tradeoffs, such as hardness vs. brittleness or toughness vs. ductility. Also, other solutions are at the designer's disposal. For example, a strong steel beam can be encased in a hard steel jacket to achieve both properties where they matter. For corrosion resistance, other choices include coating the steel with zinc or simply painting.

Once upon a time, steel was a concept, then a reality, and now steel is a large category of industrial metals.

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