Materials Science for Cosplay 1: Steel
Many cosplayers struggle with finding the right material to build their beautiful creations. In this series, I’m going to talk about different aspects of materials science from an engineering perspective, as it relates to Cosplay. First topic: Steel.
Steel is much more complicated material than our limited linguistic treatment would imply. Colloquially, there are two kinds of steel: normal steel and stainless steel. In reality there are dozens of commonly available kinds and thousands of others. I’m going to talk about the most common and the most useful for crafting and costuming.
Steel is an iron alloy where the primary alloying material is carbon. That means it is elemental iron with carbon mixed in. The ammount of carbon and the presence of other alloying elements can change the properties of the metal dramatically. An iron alloy is considered steel if it has between 0.008% and 2% carbon by mass. More than that and it is called cast iron, less and it is just called iron.
THe properties of steel can vary widely and the alloy used to make scalpels are hardly recognizeable as the same base material as is used to create archetectural skeletons or turbine blades. When crafting with steel, it is easy to accidentally end up with a material that will shatter, ruin your tools, refuse to weld, or cost three times what you need to spend.
Mild steel is probably the stuff you are most likely to work with. It is usually sold as cold-rolled steel.
“cold-rolled” does not refer to the alloy, rather to the process used to shape it. However, given that it can be cold-rolled, it is guaranteed to be relatively easy to work with. Steel alloys have codes used to describe them and most cold-rolled, mild steel is 1008 or 1018. the “10″ means that it is carbon steel with no other significant alloying elements and the 08 or 18 refers the the carbon content, in this case 0.08% or 0.18% respectively.
Mild steel is great stuff. You don’t need particularly special tools to work with it. You can weld it, cold-work it, and forge it. The big drawback to it is that it will rust. Without a protective coating, wearing it and sweating on it will turn it orange and stain everything around it really well. However there are a variety of coatings and surface treatments that will keep it looking good for a long time.
1008 cold-rolled 20-gauge sheet steel is what I used to make this pauldron.
For those of you that want something a little shinier and more resistant to the damp, you want stainless steel. The downside to stainless is that it is more expensive than mild steel and harder to work with in every way: It doesn’t heat treat as well, it’s harder to machine, and it is harder to weld.
There are, again, dozens of kinds of stainless steel. The kind used to make your kitchen sink is not at all the same as what is used to make a doctor’s scalpel.
The kind you probably want for costumes and props is called 304 or A2 Stainless. This is the kitchen sink variety. It can be welded, although it’s a bit more challenging than with mild steel. It can be cold worked and machined. Also it is common as muck. This is Austenitic stainless steel. It has a different crystal structure to most steel at room temperature due to the high chromium, nickel and manganese content which has the effect of making it highly resistant to rusting and also, non magnetic.
Othe stainless steels vary in properties and price. Some will shatter like glass and some will happily sit in an acid bath for weeks without corroding. Most of these you can tell apart from 304 stainless by sticking a magnet to them or looking at the price tag.
There are several kinds of tool steel and I include it here mostly to warn of its existance. There is little need in costuming or hobbies to use this stuff. It is, as the name implies, used for making tools. It is tough and hard and versatile. It usually has small ammounts of Tungsten or Vanadium added to it to give it its ability to cut through other steels without dulling. Most tool steel is machinable until heat treated, but even then it will wear out your bits and blades more quickly than other steels.
Like cold-rolled steel, damascus steel is not an alloy, it is a description of a process. I include it here because there is something of a modern romance with it. Damascus steel, or more correctly, pattern-welded steel is what traditional Japanese katanas were made with as were many other swords throughout history. It is not a magic lost technology, rather a solution to a problem that we don’t so much have anymore.
Ancient foundaries didn’t have fine control over the quality of the steel they produced; there was as much luck and superstition in steel production as there was science and process control. The steel that could be produced was usually too soft to make a good blade, or so hard and brittle that it would shatter. The solution was to combine them. If you make layers of soft and hard metal and then forge them together, fold and flatten, fold and flatten. Then you get an effective blend of the properties. You can make a sword that can be sharpened and keep a razor edge, while being tough enough to not shatter on impact. The Katanas of lore folded their blades so many times that the layers were microsopically thin and can barely be considered pattern-welded by the end.
We have since found better alloys and processes for blade making and most damascus steel is now done for aesthetic purposes like the knife below, which was acid etched to show the different layers of steel. It is beatiful, but not specifically better than modern alloys and heat treatments can produce with much less labor.
Photo Credit: Sean Stoughton
Obviously I can’t put everything there is to know, or even everything I know about steel here, so feel free to ask questions. I’ll do my best to answer them.