Volumes upon volumes have been written about steel chemistry and properties, and which steel is best for a particular job. The kobolds prefer if I keep it to around 500 words (kobolds have short attention spans), so I’ll quickly cover simple carbon steels and low alloy tool steels. Although stainless and high alloy steels have their uses, they cannot be used effectively for high impact weapons such as swords and axes, so perhaps we’ll deal with them at another time.
There are literally hundreds of types of steel, so we’ll only be scratching the surface and focusing on the most common types used in common cutting tools.
Simple Carbon Steels; or the Power of 10’s
Simple carbon steels, also sometimes referred to as 10 series steels, or spring steels, have the simplest chemistry of any of the hardenable steels. Although they can contain small amounts of alloying elements, for the most part they are iron and carbon. They are called 10 series steels because they are described by a 10 followed by a second two digit number. The ten simply means that it is iron and carbon without any significant alloying elements added. The second number tells how much carbon is in the steel. For example, 1075 contains approximately 0.75% carbon.
Some commonly used 10 series steels are 1045, 1050, 1060, 1065, 1070, 1074, 1075, 1080, 1084, and 1095. The steels in red are known as nearly perfect eutectoid, which really means that they form carbides easily with little “soak time” at temp and are relatively easy to heat treat. Of these, 1084 is one of my favorite steels because it’s really hard to mess up the heat treatment, and it forges like butter.
The steels with lower carbon content are not capable of as much hardness but are tougher than the steels with higher carbon content.
Low Alloy Tool Steels
There are lots of types of low alloy tool steels, but these are some of the types most commonly used in cutting tools: 5160, 52100, W1, W2, and O1. Some might argue that at least some of these steels belong with the 10 series steels, but they are different enough that I want to talk about them separately.
Let’s start with 5160 and 52100 because they are related. The 51 in 5160 indicates that this steel is low chromium and the 60 indicates a carbon content of 0.6%. It makes very tough blades and is good for swords and axes. In industry it is commonly used for automotive springs and is sometimes called spring steel along with its cousins in the 10 series.
52100 is commonly used in bearing races and ball bearings because it is capable of high hardness and is very wear resistant. The 52 indicates medium chromium content and the 100 tells us it contains 1% carbon. This steel is difficult to forge, is easily screwed up by inattention to temperature, and hard to heat treat properly . . . but it makes a very hard and durable blade up to the size of a large knife. It’s too brittle for swords, but I know a smith or two who successfully make small hatchets from it.
W1 is a water hardening steel that is essentially a cleaner version of 1095. The W means it’s water hardening and the 1 stands for “type 1” or “formula 1.” W2 is the same formula as W1, but has vanadium added, which increases wear resistance. These are both great all around steels for small and large blades. W2 is especially well known for forming excellent hamon. Although they are water hardening steels, small cross sections (such as blades) are safer to harden in oil to avoid cracking in the quench.
The “O” series has a few members, but nowadays O1 is the only one readily available. The O indicates an oil hardening steel, and I guarantee it will crack if hardened in water. Again, the “1” is the formula number. O1 contains 1% carbon, so is capable of making a very hard blade, but as with other very high carbon steels it is too brittle for swords and other very large blades.
I think that’s about all the kobolds will let me get away with . . . (712 words) :-)
19 thoughts on “Real Steel: Steel Types and Properties”
That is an awesome rundown and I am always happy to see someone talk about a technical topic in a way that is accessible to the interested amateur. Well done.
Questions: When you say lower carbon steels are “tougher” but not as hard, what does that mean? What is toughness for steel? Flexibility? Not shattering?
Also, you *gotta* link terms like “water hardening” or “hamon” to Wikipedia or something. They’re not everyday words for most of us!
Excellent feedback, Wolf. I’ll do that here in a moment. :-)
@Wolfgang – sorry about the lack of links. There were time issues on this one (worse than my usual time issues). There are enough “Real Steel” that I usually link back to older ones now.
For hardening go here: http://www.koboldquarterly.com/k/front-page6917.php
For hamon go here: http://www.koboldquarterly.com/k/front-page7203.php
You nailed it on “tougher”. In steel talk tougher means softer. It won’t hold an edge as well and will bend easier, but it is less likely to break. For example steel that is heat treated to be a spring can be bent many times and go back to it’s original shape, but it’s not as hard as a knife that’s heat treated harder to hold an edge longer, but will break if bent as far as the spring.
Use of the word ‘eutectoid’ makes me happy as a materials scientist. Don’t usually expect to come across it in Kobold though :)
Getting back to basics: aren’t the steels you mention 1084, 52100 etc. the ones you buy off a shelf? If you wanted to, could you create your own steels from scratch -> using iron ore and carbon (charcoal?)? With the result being equivalent to one the numbered steels?
@Micah – I never thought that we’d be talking about eutectoid here, either, but it’s become clear to me that the kobolds are are hungry for knowledge – without any limits. That makes me happy. :)
@Darkjoy – Yes, all those steels can be bought off the shelf (although not at your local big box store). Absolutely you can smelt your own steels! I don’t run smelts myself, but I’ve been to a couple. If I have an opportunity to go to one again I plan to write it up here. Depending on how the smelt is set up you can end up with anything from wrought iron (almost no carbon) through the equivalent of the entire 10 series and up to cast iron (2% carbon). Different parts of the “bloom” that’s produced can have different carbon contents – or it can be somewhat more homogenous.
So basically there is a recipe for every steel, which is probably painstakenly learned from previous failures and successes?
The riddle of steel – it continues….
@Darkjoy – Exactly. At a backyard smelt you’re more or less limited to carbon content, but industry is capable of adding alloying elements to make a product harder, tougher, wear resistent, stainless, shock resistent, the ability to remain hard at high heat, etc, etc.
Why can’t you add a little chromium or the like at a backyard smelt? What makes it easier to add carbon than to alloy steel with … anything else?
@KQ – everybody likes Carbon, chromium is not a party favorite. Or, in science speak: chemically carbon is a better fit / reacting agent with most other elements than chromium.
The periodic table and the ubiquitous nature of carbon probably has something to do with it. That is what I remember of high school grade chemistry.
@Kobold Quarterly – Many alloying elements require very specific temperatures, atmospheres (or vacuum), amounts, and timing to be properly alloyed into the recipe. This isn’t practical (or even possible) at a backyard smelt.
Also, some elements release incredibly toxic gases at smelting temperatures. Chromium is one of them. Zinc, although used as a coating, not an alloying element, has killed quite a number of smiths who put galvanized steel in the forge.
Specifically on chromium (because you mentioned it) in amounts starting at about 12% is used to make stainless. Most of us (smiths) don’t use stainless very often.
@Darkjoy – Yes, carbon and iron like each other. Not so with iron and some other elements.
Todd, you’ve just given me a great idea for a toxic haunt :-)
Happy to help! Looking forward to reading about it!
@Pia Sweezer – Really? Spamming KQ? How about I show up at your site with a hammer and some tongs and get $#*%* medieval on your dumb a#s?
See what you’ve done Todd? You’ve gone and activated Darkjoy’s diabolical trait. He’s descended into the dim shadows of his unregulated workshop. He won’t emerge now until he’s constructed another twisted trap. I hope you’re proud of yourself!
Spam removed! But yeah, annoying.
@James Thomas – Very proud. Can’t wait to see what emerges… :)
Done already, unregulated workshops don’t abide by the clock!
PC complaints will be handled by Todd and his medieval tongs and (I suspect) blowtorches.
@Darkjoy – Awesomeness! When will Miranda let it crawl into the daylight?
Sorry about my little outburst, spam is starting to get on my last nerve. It’s especially irritating here.