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Case Hardening
#1
I am attempting (key word there) to construct Lorica Segentata type B based strictly on finds. Yes I have read the articles by Matt Amt, yes I have access to materials and tools. My only question so far is about case hardening. I remember reading somewhere that the Romans used case hardening for numerous things including LS. Is this information accurate? If it is I have some more questions. One recipe I heard was charcoal and ground bone, has anybody tried it out? Anybody have any tips for case hardening? Thank you in advance.
Salvatore Caretti, Legio IX Hispana
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#2
Note: you are posting in the rules and announcement folder.

Please post in the appropriate area, such as Roman Reenactment or Beginner area.

Cheers!
Steve in WA

Pone hic aliqua ingeniosum.
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#3
I found the LS case hardening on Wikipedia I believe but not everything on there is inaccurate.
Salvatore Caretti, Legio IX Hispana
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#4
Ok the question I had about LS being case hardened seemed unpopular, but I have another question maybe some brave souls could answer. Was case hardening the only process that the Romans knew how to make steel from? For instance, were steel gladii case hardened? Is there another process they knew of to make steel?
Salvatore Caretti, Legio IX Hispana
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#5
Look up Carborising/Carborizing ;-)
Ivor

"And the four bare walls stand on the seashore. a wreck a skeleton a monument of that instability and vicissitude to which all things human are subject. Not a dwelling within sight, and the farm labourer, and curious traveller, are the only persons that ever visit the scene where once so many thousands were congregated." T.Lewin 1867
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#6
With the information you have given it seems that carburizing(Google said 'ur') and case hardening can be used interchangeably, is this incorrect?
Salvatore Caretti, Legio IX Hispana
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#7
Quote:With the information you have given it seems that carburizing(Google said 'ur') and case hardening can be used interchangeably, is this incorrect?

Normally I would refer to "case hardening" as a shallow hardened surface and that it implies a substantial soft core, and carburisation as a method of increasing the carbon content in iron or steel.....

"On Divers arts" Theophilis 1100ad, On the hardening of files: burn the horn of an ox in the fire and scrape it. Mix with it a third part of salt and grind it vigorously. then put the file in the fire and when it is red hot sprinkle this composition over it on every side.

I would guess this as a variation on case hardening....

http://store.doverpublications.com/0486237842.html
Ivor

"And the four bare walls stand on the seashore. a wreck a skeleton a monument of that instability and vicissitude to which all things human are subject. Not a dwelling within sight, and the farm labourer, and curious traveller, are the only persons that ever visit the scene where once so many thousands were congregated." T.Lewin 1867
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#8
There's a little more to it than that. Do a search on armour archive as a few of the guys there have done it. You need to do it in high heat with no oxygen to prevent the steel from burning. Usually covering the item in clay. More than a few nice pieces haved burned up from botched hardening attempts. Now, there are a few companies that sell a comercial product for case hardening, but its a completely modern method and doesn't penetrate as deep as medieval methods. You're much better off using 1050 or other spring steel and doing a heat treat.
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#9
Would agree entirely re carburising, though I believe Theophilis writes something on this as well in the next chapter....

However Herbert Maryon** talks of the use of Sodium Cyanide as a case hardening compound, basically its prussic acid and lye, its common in old metal working tech to find toxic substances being used, but I'm certainly no specialist in such things and tend to avoid it if I think it could be dangerous...

Theophilus's decription of a salt may be a similar mixture?

**Metalwork and Enamelling
Ivor

"And the four bare walls stand on the seashore. a wreck a skeleton a monument of that instability and vicissitude to which all things human are subject. Not a dwelling within sight, and the farm labourer, and curious traveller, are the only persons that ever visit the scene where once so many thousands were congregated." T.Lewin 1867
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#10
http://www.tf.uni-kiel.de/matwis/amat/de...ce_an.html

This may be of some help answering your question. Folding case hardened steel and then forgewelding it, casehardening it and repeating the proces will cause the carbon to be more evenly distributed in the steel. Leaving it to soak in a carbon saturated enviroment (smouldering coal fire in an enclosed environment with little oxigen) for a longer period should produce deeper penetration of the carbon. Perhaps they used a charcoal kiln, as that would produce a good environment for case hardening?
Salvete et Valete

Nil volentibus arduum


Robert P. Wimmers
Archeologie Beleven!
>http://www.ferrumantica.eu  (The NEW Fabrica of Vvlpivs!)
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#11
Quote:Perhaps they used a charcoal kiln, as that would produce a good environment for case hardening?
Case hardening apparently works best in an oxygen-free environment. You'd have to pack the iron item in a carbon-rich material, then cover it with clay to keep out the oxygen, then put it in the kiln. Under these circumstances it doesn't really matter whether the fuel is charcoal or not because the carbon in the charcoal will have no chance to interact with the iron. Though charcoal would be a good material in which to pack the iron before covering with clay.

I wonder whether a charcoal-maker's kiln could be used to perform two tasks at the same time. Charcoal is made by roasting wood in a low-oxygen environment and it takes several days to complete a burn. It might be possible to load an iron object into the kiln at the start of the burn and leave it there while the charcoal is being made. It is possible that some of the carbon will migrate into the iron during the multi-day roasting. The main problem I see is that these kilns may not burn hot enough to enable carbon migration. If it works you could make charcoal and case-hardened iron at the same time and save a ton of fuel.
Author: Bronze Age Military Equipment, Pen & Sword Books
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#12
As we are speaking about the Roman era, the prime obvious source for carbon to pack the iron in would be charcoal. The iron would need to be cherry red/ dull yellow (about 800 degrees C) to allow the migration of carbon, any higher and you run the chance of burning out the carbon. This is a real risk when forging medium to high carbon steel. A charcoal kiln may not reach that high a temperature, I admit not knowing, as the fire smoulders, burning of the volitile components of the wood, but it is an oxygen starved environment, or else the wood would just burn up. Encasing the object in clay I believe is tricky, as the clay would have a tendency to crack if gasses are released inside the casing during the burn. And the carbon would need to be at a molecular level (gas) to be able to diffuse into the molecular structure of the iron. An closed oven filled with charcoal would have the same effect of producing a carbon laden atmosphere during a controled slow burn and would allow a beter temperature control then an encased object, I would imagine.
Salvete et Valete

Nil volentibus arduum


Robert P. Wimmers
Archeologie Beleven!
>http://www.ferrumantica.eu  (The NEW Fabrica of Vvlpivs!)
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#13
Thank you all for your knowledgable responses on the process of case hardening but if anyone has any information on armour an/or weapons that used the process of case hardening, it would be greatly appreciated.
Salvatore Caretti, Legio IX Hispana
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#14
Decades ago I owned a Sharps rifle that had a case hardened receiver. Read a lot about how it was done. Just curious. I never attempted it.
Search on the net showed this forum string on color case hardening for a Marlin rifle.
Anyhow hope it gives you some ideas. 31 forum pages with some photos of before and after, the process, quenching etc etc-must be something there-metal work talk

http://marlin-collectors.com/forum/viewt...=21&t=3732
-Rod Dickson
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#15
On that note you may find this article interesting:

http://www.doublegunshop.com/doublegunjo...v7i4_9.htm

"Only samples prepared with percentages of bone charcoal greater than 50 percent produced measured hardness greater that the cold-rolled steel substrate. A sample produced by carburizing in 100 percent bone charcoal for two hours at 715 degrees C. and quenched at this temperature was cross-sectioned and examined under a metallurgical microscope. The surface-hardened layer was found to be only .002 inch thick and had undergone a true transformation to the Martensite phase of steel indicating that true hardening had occurred."

I cant help but connect this to the methods described by Theophilus....

Its interesting to note that 100% Bone charcoal produced a Martinsite case.... I think "steely" segmenta refered to by M:C:Bishop in "Lorica Segmentat" vol1 was a Perlite case with a ferrite core....

Another book worth mentioning is "The manufacture of steel" in the 1850s

Case Hardening is included with some mention of animal products being used such as horn, bone, hides.. see pg 67 on

A later book "Practical Blacksmithing" 1888 also includes methods of what the author calls "box hardening" basically case hardening in a box see pg 258, this uses bone dust,leather or hoof and salt, all the pieces to be case hardened could be placed in the box together...

Prussiate of Potash for case hardening (in the fire) is often mentioned by these old manuals....
Ivor

"And the four bare walls stand on the seashore. a wreck a skeleton a monument of that instability and vicissitude to which all things human are subject. Not a dwelling within sight, and the farm labourer, and curious traveller, are the only persons that ever visit the scene where once so many thousands were congregated." T.Lewin 1867
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