Ive always wondered what allowed a breastplate to have the amazing properties of protection it gives. the science behind it, what allows it to go were the same thickness sheet steel will fail. how it even seems to negate impacts as much as cutting edges. how did it evolve these features? how did they work? all help is appreciated! -thanks!

Both armor plate and sword blades were hardened and tempered for their purposes. A properly hardened sword blade will tend to go through softer things such as sheet steel, but be turned aside by harder steel armor. Also most armor tends to have rounded and curved surfaces rather than large flat areas. This is so any strike by the point of a weapon will tend to hit at a glancing angle and be deflected instead of at a right angle that would maximize piercing potential.

I am no expert but I would have to say one of the biggest contributing factors would be shape. For example... The rolled edges, creases in the surface will all add rigidity. Think of a potato chip with ridges... makes for a stronger scooper of dips. In addition to the contours on the surface of plate mails, they had also been designed to distribute the force of an impact, much the opposite as many of the weapons that are more effective against plate that tend to concentrate force. Think of the spike side of a typical warhammer, one of those weapons effective against plate. Shape of plate mail was also designed to make it hard to get a square hit. Instead the curved surfaces would turn a typically good square hit in to a glancing blow. I am simply applying my understanding of physics here. I am not at all educated on the technology of plate mail.
I am sure that there are other factors which would contribute to plate mails durability which might include treatment to the metal itself, which I know nothing about... I am sure someone will chime in with some actual knowledge on the subject.

Curvature contributes the best against most attacks. Much of your force of impact will bleed off if you don't strike at 90 or near 90 degrees.

M.

There is a good book out there on the subject although hard to find: The Royal Armoury at Greenwich 1515-1649: A History of Its Technology (Royal Armouries Monograph)

It was a metallurgical analysis of period armour and the conclusion was that even when the quality of the steel was poor attempts were still made at hardening. The hardening process shows up under the microscope and they can tell when iron was quenched hot. Another interesting tid bit from that book was that a single sheet of steel could range from wrought iron to high carbon steel. The carbon was "streaky" through the piece as they didn't have the modern homogeneous steels we have today.

Even a wrought iron breastplate is going to protect you from a cutting edge however, it's just not the right tool for that job.

Cheers,
Matt

Go read "The Knight and the Blast Furnace" by Allan Williams. University libraries near you may have a copy--buying it is rather expensive.

I need to get to work, but I'll post some general stuff later.

-Will

I think it is interesting that they attempted to harden low-carbon or wrought iron, these materials would generally be harder and springier if cold-worked to some degree and left in that state, than they would be after heating and quenching.
I wonder if perhaps these pieces which were quenched but do not contain enough carbon to harden effectively, may be pieces which they attempted to carburize, but unsuccessfully?

To look at it from another angle, though, hardness does not directly equal toughness or resilience, so in considering just the hardness we are perhaps barking up the wrong tree, their criteria in period may have been quite different from ours. Interesting stuff.

The old irons and steels don't like work hardening. It makes them much more brittle than it does modern steels.

Thanks, I added "The Knight and the Blast Furnace" to my amazon wishlist which continues to grow unlike my bank account. It does sound like it mirrors the Greenwich findings.

Justin, It's been a few years since I've read that, but I don't believe they found evidence of any case hardening. I also found it curious that they attempted hardening low carbon steels, but really without hitting it with a grinding wheel and observing the sparks I don't think I could tell the difference between annealed high carbon and low carbon steel especially when it was mixed in the same piece of metal. There's probably other people here with more experience with that though, I'm used to modern steels. Finding wrought iron and non industrial-era steel now days is tough and if I did find it I'd save it for a special project.

Cheers!
Matt

I would like to add the question:

What does it need to make plate armour shot-proof beside making it simply thicker?

Was there any armour which really could withstand a point blank shot of a heavy musket?

DUPLEX: It consists of a plate of softer iron riveted or welded to a plate of harder steel.

There are also recipes for different heat treatments for shot proof plate but it would have been difficult to do these accurately enough with the technoloogy available.

Read the RA's journal Arms and Armor, Vol. 2, No. 1 "Duplex Armour: an unrecognised mode of construction." pp.5-26

At the Battle of Roundway Down Sir Arthur Hasselrigg was unharmed after bing hit by three point blank shots, but it isn't clear what the weapons were.

King Charles quipped "had he been vitualled as well as fortified he might have endured a siege of seven years"

Thanks Daniel. I hadn't read Atkyns.