Hello,

I have what I think is a pretty simple question but I can't seem to find the answers online so I thought I'd try here.

What are the main differences/advantages steel has over iron? And also higher carbon steel compared to lower carbon steel. I'm curious in regards to both weapons and armor and in the context of performance and not production.

I gather that steel is harder than iron, but is that it? Does it get heavier or lighter, more durable because it's tougher, more resistant to the elements? Is steel armor needed to defend against steel weapons?

Thanks

In general, the more carbon content steel or iron has, the harder it becomes. The harder something becomes, the more brittle it can become. So, something like cast iron, which tends to have a lot of carbon, is quite brittle and is therefore a poor choice for manufacturing arms.

Iron and low carbon steel tend to be soft due to the fact that they have a low-carbon content. However, it also makes them ductile rather than brittle and they will tend to bend rather than break. Being soft does not lend those weapons to being good at edge retention, though you can potentially carburize them in the heat-treatment process to give them a hard outer layer.

You need an appropriate carbon content to be able to heat-treat steel with normal or traditional means. This is why we tend to view low-carbon steel and iron as non-hardenable while steel is regarded as a material which can be properly adapted for tough weapons and tools.

How hard you want the steel depends on the alloy and the application. You may not want armor to be too hard or it might shatter. In fact, a lot of early plate armor was not terribly hard or spring tempered. If you have a very hard edge, like in a Japanese sword, you may want a soft body. This is partially why tachi / katana have a very hard steel edge and a rather thick low-carbon / iron blade body, which supports the hard edge and absorbs the shock of impact. A monosteel blade, common in European arms, may not be as sharp due to having a lower carbon content in the edge, but gains the spring temper that lets it bend and return to true. In contrast, the example of the Japanese blade will get its stiffness due to the thickness of the blade (more material) rather than the springiness of the material, and if it does bend, it will stay bent.

Questions of weight will depend on the alloy, but given the example above, you should count on a weapon made of hardenable steel to be able to be manufactured at a lighter weight than iron for comparable performance in terms of durability. Again, with iron (and steel as well) you will need thickness in the dimension you want to resist bending. You may need a rather thick, and therefore heavy, profile to resist bending if hardening is not possible.

That is a very basic view on the subject, but it should start to give you a picture. There is a lot more to the subject matter, of course. Note that true iron weapons started to come about in the bronze age. Pure iron is apparently not that hard and is quite ductile. Despite the challenges in refining it, it's much more plentiful in the environment than the copper and tin needed to produce bronze, which is why the world moved to iron and steel in the first place. A high quality bronze weapon should outperform a pure iron weapon in terms of sharpness. I cannot say with certainty what other mechanical expectations you should have to compare the two, other than the fact that bronze is a denser (heavier) material than iron and it is also more corrosion resistant (which is why some bronze weapons could still be functional today, while iron ones are mostly just rust).

Nicely put! Also note that other elements can be found in iron weapons, especially, such as nickel, sulfur, phosphorous, etc. Some are just impurities, or already present in the ore, some were added to try to harden the iron. Sulfur and phosphorous *will* harden the iron, but make it more brittle, so eventually carbon won out as the best additive overall.

Note that early iron weapons didn't *have* to be harder or better than bronze overall, they just had to cleave flesh and bone, which they did just fine.

Matthew

Some things to keep in mind.
1. No sword can cut through armour and any blade at all can cut flesh with little effort.
2. Edge retention is largely irrelevant because a blade only has to maintain functionality till the end of a single encounter. It can be resharpened afterwards.
3. The only practical benefit of a good quality steel sword is that it is less likely to bend or break in the middle of a fight.

I don't think you need steel armor to defend against steel weapons, because harming someone in iron armor would be no easier with a steel weapon than with the same weapon made of iron. The only differences would be that a steel weapon might be less damaged in the attempt (depending on what kind of a weapon it is and what exactly happened)... and if I understand it, plate armor is more durable if made of heat-treated steel than iron since steel can spring back from blows a number of times before the resulting metal fatigue gets bad. Don't know what difference it would make if the armor is mail or scale.

AFAIK plain steel is no more weather-resistant than iron regardless of the carbon content. In fact, I recall seeing claims that wrought iron is actually more corrosion-resistant than steel, though I'd have to go casting about for a source on that. In any case, for serious rust resistance, you need to add chrome (making stainless steel) or certain other elements.

Ed.: This site claims that the fibrous slag inclusions of wrought iron add a measure of rust-resistance that true steel lacks.

Thanks for the responses everyone.

I was pretty sure that a steel sword wasn't going to pierce an iron breastplate, but I wasn't sure if the hardness would be sufficient to increase the amount of force an attack would need in a noticeable/practical way. I was thinking perhaps iron mail rings might be easier to break or attacks at the ventilation holes.

Or, I thought maybe it was more a matter of long-term maintenance and durability.

Dan D'Silva, part of my confusion did arise when I discovered (assuming it's true) that wrought iron is more corrosion resistant than steel. I would've thought for military equipment that corrosion would be an issue.

Corrosion isn't *necessarily* a big issue. For aristocrats, it's no concern at all: "Boy! Clean this!" See? Easy! Grunt soldiers have to take care of their own stuff, of course, but as far as their officers are concerned, that's still a *benefit*--you can always keep a soldier busy by having him clean his armor, and a busy soldier is a good thing. Granted, a lot of medieval helmets and armor were painted, and by the 16th century a lot of munition armor was being left black from the forge. But the latter was also much cheaper to produce, since the final finishing and polishing was not needed, so it may have been more about economics than maintenance.

Matthew

Protecting and maintaining equipment is part of keeping it ready and operational. Just consider swords in museums - high value arms have been maintained over a very long course of time, and may very well still be functional. Poorly maintained weapons may be nothing more than oxidation and rust. I despise the folks on Antiques Roadshow that like the "patina" on a Civil War sabre. It's not attractive in many cases - if it's bad, it really just means that someone stopped taking care of it. Unfortunately, if it is really bad, there is not much more that you can do to it other than keeping the oxidation from advancing.

Rusty and corroded edges, furthermore, may not be very sharp or keen. So, before I dwaddle on further, well-maintained kit is very important to the professional soldier or for anyone that must maintain arms. As a further extension, having a corroded barrel in a gun is a problem - maintaining it should keep that from happening.

...If the weapon or armor is painted or intentionally oxidized (or perhaps seasoned), that's just less maintenance that needs to be performed, and should also be somewhat of a guarantee that it will resist corrosion and hold out against the elements in general.

Regarding sharpness, a weapon that stays sharper longer should need less maintenance overall. If combat is protracted, the weapon that stays sharp definitely has an advantage. So, I'd also counter some previous points with the statement that better weapons are, well, better! It's not to say poor weapons don't work - they do - but they're obviously not as good overall.

Corrosion of wrought iron vs. steel is interesting - I'd not heard of this before...

Hardened armor vs. soft iron armor becomes an issue when penetrating weapons like lances or missiles are involved. In fact, percussion weapons like hammers and maces are also a concern to softer armors. At shorter ranges, soft armor is more likely to be compromised by missiles, and it can also be more readily penetrated by lances or hardened points. Or, it can also potentially be deformed, thus potentially reducing the mobility of the user or injuring the user directly.

Tensile strength is certainly a concern for something like chainmail. Again, this is a concern against penetration rather than slashing or cutting attacks. Actually cutting the chain (or bursting the links) is not impossible, but it's definitely difficult. Part of the difficulty in damaging mail is probably keeping everything stationary - moving or reacting to the impact will reduce the force which can be imparted to the rings.

Concerning edged weapons, even textile armor can be effective, especially against a dull edge. So, yes, the edge vs. the appropriate target is a big deal. And when against the inappropriate target, such as an edge vs. any metal armor, it is almost entirely ineffective.

Regarding rusty and corroded edges - are blunt weapons affected by superficial rust and corrosion or is this primarily an issue regarding blades?

Regarding painting or intentionally oxidizing your weapon or armor - is this something that was done to weapons in the middle ages? I'm assuming you can't/wouldn't paint a blade because I'm not familiar with painted blades, but I'm guessing there's another way?

When you talk about hard vs soft armors I'm presuming we're still talking exclusively about metal armor (and specifically iron/steel).

Thanks again. And for clarity, I did make this post with the assumption that the material of armor was going to have much less effect on swords as it was going to have on pole weapons, missile weapons, and blunt weapons, and in regards to swords it was primarily, if not exclusively, thrust/piercing attacks. But I know very little about metallurgy and what I do know about these sorts of things has been so influenced by popular media that I can't know what to trust haha.

Edit: The topic about rusty and corroded edges affecting the sharpness and therefore effectiveness of bladed weapons has me curious about the importance of edge sharpness on battle axes. Do battle axes rely on sharpness as much as swords do or can they get away with being duller due to the heavier design of their blades? Or are they supposed to be duller? I've had a friend warn me about over-sharpening my throwing axes because they might chip, but this could be a throwing axe thing or maybe rubbish, idk.

The finer the edge, the more easily it can be damaged. This is a question of the actual edge geometry of the weapon. The most durable edges may not be or seem sharp, yet the sharpest geometry may be so fine that it easily becomes damaged.

However, I would say chipping is more likely with a hard edge as opposed to a softer edge. The latter tends to deform rather than chip out. It is safe to assume that the ideal edge geometry for a weapon matches the performance of the material along with the requirements of the weapon.

I have no real experience with battle axes, though I do have experience with wood cutting axes. I use and swear by Fiskars axes. These are made of VERY hard steel that will chip if you strike something hard like stone. However, they hold a very sharp edge that makes cutting easy, and they employ a relatively fine edge which cuts as well or better than many knives I've encountered. I don't buy into the notion of "axe sharp," as sharp cuts while dull doesn't, or does poorly. It is not to say that there are not different edge geometries for different tasks, but when you need sharp, you'll know when you have it or when you don't.

In general, I have heard rust compared to cancer in steel. I agree with this sentiment. Rust will ultimately do nasty things to your arms if you don't keep it at bay, and with any ferrous-based material, work and maintenance will be required to prevent corrosion from taking its toll. I am potentially over-reacting to rust in my posts here, but I don't think it's unfounded.

Yes, you can over-sharpen things: Rick Furrer once dissected a wootz tulwar for metallurgical analysis. The blade was so oversharpened that an obvious "scallop" had been ground out of the entire length of the blade. Or rather, it used to be a good deal wider than what it ended up as. There is a video on that on YouTube if you search for it. So, the point that you can over-polish armor is a good one...

...However, rust can potentially cause divots that may be weak points, or may even help a weapon gain purchase (e.g. bite into the armor). So, polished armor is something in my opinion that's more likely to help an armored fighting man than it is to hurt him... unless that armor has been completely polished away!

Ultimately, weapons and armor are consumables, and they will wear out due to the elements or abuse. However, not maintaining arms due to fear of removing material is something you should be very specific about. If it's a historic piece, you probably shouldn't mess with it. If it's your charge and it's new, it's obvious that you should!

Regarding blunt weapons, rust probably effects performance less, but it could ultimately compromise the weapon's durability. Think about rust getting into a forge weld or opening up a joint at a critical point.

Did not cover all the points, but there are far better qualified opinions on these matters here than myself.

The steel of Weland experiment https://badenhausen.net/harz/svava/WelandsSteel.htm and the story https://books.google.com/books?id=3BZvJXJ4qRUC&pg=PA86&lpg#v=onepage&q&f=false