Steel is a generic term for a range of metals predominately composed of an alloy of carbon and iron. The exact properties of the resulting mix depend on its constituents - but it must be mostly iron and between 0.002% and 2.1% carbon to fit the bracket - chromium, berrylium, manganese and other elements may also appear to some degree.
Historically, good steel was hard to achieve - too little carbon and the metal is soft (tending towards pure iron), too much and it becomes hard and brittle like cast iron … find the right mix and you have a strong, relatively light material idea for arms and armour (which were its main historical uses until very recently1). Properly made and used steel flexes under stress rather than bending or breaking, but can still take a lethal edge. Good steel should also remove the mineral impurities (slag bodies) from the metal to make it less brittle.
Methods of preparing steel were often closely guarded secrets in the pre-patent era and subject to a great deal of mysticism and misinformation2. In many pre-modern cases, the quality of steel was directly effected by the natural alloy composition of the orebeds from which it was mined - a fact sometimes recognised but rarely understood until very recently. Traditional steel making involves heating and working iron in a charcoal fire so that it can adsorb carbon, although more advanced techniques include melting raw iron in a sealed container with a carbon source and a flux to remove impurities. Charcoal was the normal carbon source, but some sources suspect that bone may have been used instead, possibly for mystical reasons. Where the metal could not be heated hot enough to separate out the slag bodies with a flux, they would need to be worked out by prolonged hammering - such bodies are the source of the sparks typically seen flying about in a forging montage … a high quality crucible steel will produce nothing of the kind. Iron produced in a blast furnace (cast iron) by contrast, is often relatively free of slag but will be too high in carbon and needs to be worked in a high oxygen environment to drive it off.
Another, related technique, used to produce a relatively high quality blade from indifferent steel was pattern welding. This effectively built a sword (and given the expense involved, it would almost have to be a sword) from two different types of metal - a core of softer, lower carbon metal for flexibility and strength and edges of higher carbon steel for a hard, sharp cutting edge. Similar effects are generated by various layering and folding techniques such as the Japanese tamahagane method.
Perhaps the most well known piece of mysticism related to the topic is the idea of the Riddle of Steel - a piece of spiritual wisdom related to the nature of steel that makes a Man better at wielding it.
That said, many of the mystical properties associated with iron - especially the cold iron meme - seem not to carry over to steel. Cold steel is frequently referenced, but usually as a contrast to (self heating) firearms as opposed to anything spiritual.
Game and Story Use
- Encourage significant variations in the quality of steel across your campaign world - this may be due to differences in technique or ore supply, or both.
- Steel weapons and armour should normally outperform iron equivalents (and pretty much any other metal as well), but many fRPG rules model this badly if at all.
- Cheap steel weapons may prove an extremely bad bargain if they shatter at the wrong moment - which might be reasonably expected of a blade that has been over carburized or is shot full of slag inclusions…
- The mystical dichotomy between iron and steel can be averted - or played up. Perhaps adding more than 0.002% carbon really does make a knife less use against fairies.
- For magic weapons, using bones in the forging process may be important. It may also matter what (or whom) the bones were derived from….