Hardness of Roman Armour

[Eleatic Guest]

There has been done a bit of testing the hardness (HV) of medieval steel armour. Do we have any idea about the hardness of different types of ancient body armour, bronze or iron?

[Flavivs Aetivs]

I've heard that LS was actually face hardened steel and then the underside was soft iron, but I'm not sure if that's true.

[XorX]

have a look in : "Roman Imperial Armour; the production of early >Imperial military armour" by D. Sim and J. Kaminski, Oxbow Books

[PhilusEstilius]

There was an old friend of mine the late John Anstee who used to smelt Roman iron in the true Roman fashion with charcoal and when this was done the charcoal had to be hammered out of the bloom.
I myself have made so many lorica segmentata in the past that I have lost count of how many, however I found that I can make a segmentata from 0.6 mm that is as strong if not stronger than 20 gauge by hammering out the plates which makes them much stronger than just curving them.
Therefore I would think that Roman iron got its hardness from just such treatment with a lot of this hammering, I would also think that many Roman iron helmets might also have been made by drop forging which also gave them some of the strength they needed.

[Dan Howard]

Yep. Work-hardening helps a lot. Work-hardened tin-bronze armour can be as hard as medium carbon steel.

[Thomas V.]

Therefore I would think that Roman iron got its hardness from just such treatment with a lot of this hammering, [...].

In this video about medieval armour Jeffrey D. Wasson states that according to surviving examples of armour the curving of sheet metal was always achieved by hammering:
http://www.youtube.com/watch?v=IgzQiO9liNw
So your assumption regarding work-hardening might be true.

[Caius Artorius Castus]

Yep ones the the best things one can do is to basically hammer ever inch of a bit of armour. Also gives you much better shape control. I am making a full late 14th century arm harness and over simply rolling the rerebrace I hammer the entire piece. You can tell it is much more spring and strength to it over one that is just rolled. I have actually had greaves work harden to the point they barely budge under my 3lb shaping hammer.

I know brass and bronze can be work hardened bot sure about the medium carbon thing if this is heat treated. Best graph I know of is the one in Knight and the Blast Furnace.

CAC

[Eleatic Guest]

Yep ones the the best things one can do is to basically hammer ever inch of a bit of armour...Best graph I know of is the one in Knight and the Blast Furnace.

I saw this graph, too. But the author, A. Williams, rather makes in this book and other articles the point that quenching above all can increase hardness, but that its real value seemed to be little understood until the late MA. Were the Celts and Romans aware of the advantages of quenching and tempering?

[Dan Howard]

Quenching only has an effect if the carbon content is above a certain level. Every alloy has a different recipe for quench-hardening and it is difficult to get it right even today with modern technology.

I know brass and bronze can be work hardened bot sure about the medium carbon thing if this is heat treated. Best graph I know of is the one in Knight and the Blast Furnace.

I should have said "Bronze can be as hard as medium carbon steel BEFORE heat treating." After heat treatment, medium carbon steel becomes harder than bronze. Tylecote has the best data.

Were the Celts and Romans aware of the advantages of quenching and tempering?

Some of their surviving swords certainly seem to indicate that they were well aware of quenching and tempering. But knowing about it and applying the techniques correctly are two different things. Only the very best smiths would have been able to do it reliably.

[PhilusEstilius]

I did enjoy the video and that is exactly what I have done in the past when doing not only the girdle plates of a segmentata but all of the curves, in fact what is interesting is that I have found the girdle plates expand in length by about 1/16 of an inch from the hammering.
This is not a great problem for with a segmentata I always make it around an inch greater than the wearers chest measurement, for when one goes on the march the chest does expand with the increase in breathing.

[Flavivs Aetivs]

Many late Roman swords were pattern-welded and show evidence of quenching and tempering. Many were still made of mild steel with the "Streifendamast" technique though (this is folding the steel into "piled" steel, and as they added more folds over time it developed into pattern-welding if I am correct. I could be wrong ofc.)

[Caius Artorius Castus]

Eleatic,

I think general heat treatments is more what he is talking about. Quenching can indeed make something far harder but as brittle as glass.

Dan,

In that case you are totally right. Once you throw out heat treatments copper alloys of brass and bronze can get very hard from simply working it. It is interesting to see how quick brass hardens as well when working it. I made a small bowl and had to keep annealing it. Far more than something in iron/steel.

Magister FA,

Coulson and Bishop have a quick illustration with some sword make ups as well.
CAC

[Eleatic Guest]

There is an article on myarmoury about Sword Blade Hardness.

[Urselius]

There have been a number of metallurgical investigations on late Medieval helmets - sallets and armets mostly. These, of course, have had the advantage of having been above ground since manufacture, not something that Roman armour benefits from. Some of these helmets showed interesting variations in hardness, the outer surfaces of the helmets were of considerably harder metal than the central and inner regions of the plate.

To quote one study on a German sallet:

"the hardness was recorded with Shore's Standard Scleroscope. The bowl at the rim registers 28-30; in front, 45; inside, 22; the visor registers 60-65. These measurements indicate that the interior is cold worked wrought iron; the bowl is cold worked steel (1 per cent carbon); the visor is equivalent in hardness to cold worked high speed steel. The steel on the outside of a medieval helmet was sufficiently hard to resist penetration in most cases; the tough iron inner layer yielded, preventing the steel from shattering and thus usually producing a dent rather than a hole."

From an Italian armet studied:

"The sample from the ventail shows ferrite with only a little pearlite. The sample from the left jugular has a microstructure containing several constituents. As well as very fine pearlite, partly spheroidized in places, there is ferrite in a spiny form, and there are areas of martensite with brown-etching areas of bainite, or perhaps nodular pearlite, on their frontiers. The sample from the right jugular is similar, except that less martensite is visible. Without sectioning the entire helmet, it is not possible to suggest whether these mixtures of different microconstituents are due to some sort of differential cooling, for example, spraying one surface of a hot plate with cold water to quench only a thin layer. Another possibility is that a steel of variable carbon content has been heat-treated. Both jugular samples show similar microstructures, presumably for the same reason. Both are made of steels that were heat-treated after fabrication, to harden them. The precise mode of treatment must remain conjectural, but it might have involved a slow cooling, to allow some pearlite to form, followed by a rapid quench to transform other parts to martensite."

See:
A Late Medieval Helmet (Sallet)
Stephen V. Grancsay, The Journal of the Walters Art Gallery, Vol. 13/14 (1950/1951), pp. 20-29

And:
On the Manufacture of Armor in Fifteenth-Century Italy, Illustrated by Six Helmets in the
Metropolitan Museum of Art.
A. R. Williams, Metropolitan Museum Journal, Vol. 13 (1978), pp. 131-142

[PhilusEstilius]

I not only harden armour plates by hammering but also work harden brass as shown with the pin of this brooch and others that I make.
This is a method used by Roman craftsmen shown here with an original brooch in my collection.
[attachment=8581]102_1496.JPG[/attachment]

[attachment=8582]102_1499.JPG[/attachment]

[attachment=8583]easyshare2160Medium.jpg[/attachment]

[attachment=8584]easyshare2161Medium.jpg[/attachment]