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Etienne Hamel




Location: Acton Vale (QC) canada
Joined: 09 Sep 2006

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PostPosted: Sun 03 Jun, 2007 6:33 am    Post subject: Iron vs high carbon steel         Reply with quote

I would like to know what are the bad things and the good things about the iron and the best high carbon steel (the toughness is also in this).

thanks in advance.
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Jared Smith




Location: Tennessee
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PostPosted: Sun 03 Jun, 2007 7:05 am    Post subject:         Reply with quote

Try getting more specific.

There are many grades of iron, and some can be quite good for applications such as engines, etc. They are not commonly capable of taking a spring temper, and generally are not malleable or easily cold worked into shapes such as armour pieces.

Many armorers utilize "mild" carbon steel which has less than 0.5% carbon. This is due to the fact that it is malleable and can be formed.

The higher carbon contents that make good spring temper steels for swords (usually closer to 1% carbon) might be considered undesirable for armour due to difficulty of forming it as well as its higher stiffness (giving some during an impact as mild steel does when it dents might be beneficial in reducing severity of shock to the armour wearer.)

"Tool steel" might be around 2% carbon. This is very hard to work with, and is very stiff.

Absence of evidence is not necessarily evidence of absence!


Last edited by Jared Smith on Sun 03 Jun, 2007 12:27 pm; edited 1 time in total
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Etienne Hamel




Location: Acton Vale (QC) canada
Joined: 09 Sep 2006

Posts: 427

PostPosted: Sun 03 Jun, 2007 7:09 am    Post subject:         Reply with quote

I wanted to do a comparison between iron that we can find easily and the toughest high carbon steel (the metal is in its sword shape)
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Jared Smith




Location: Tennessee
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PostPosted: Sun 03 Jun, 2007 10:05 am    Post subject:         Reply with quote

There was regional variation between iron that was "historically easy to find."
Dark ages to early Medieval age Viking/ Scandinavian peoples are considered to have had good knowledge of and access to "bog" iron, and knew how to smelt and reforge it to deal with impurities. At the same time, some Southern European and Baltic regions had access to some mines that yielded fairly pure iron ores.

You may do best by defining what type of iron (today's most pure wrought iron), or historically impure iron ores.... From there, some of the forum experts on forging and metallurgy can probably give you an accurate general comparison of properties of modern "sword steel" versus which ever type of iron you are interested in.

A generic wikipedia search should yield some general properties for pure or wrought iron.
http://en.wikipedia.org/wiki/Wrought_iron

Spring steel as used in today's premium swords is very tricky to discuss. You have to get somewhat specific and understand that many mechanical properties can be traded or altered according to the heat treat. Discussing it requires a graph and understanding of the tempering effect. Here is one for a plain spring steel (1095.)
http://www.panix.com/~alvinj/graph1095.jpg

A good general discussion of some generic steels also is here; https://www.asm-intl.org/pdf/spotlights/tempering.pdf

Absence of evidence is not necessarily evidence of absence!
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Jim Mearkle




Location: Colonie, NY
Joined: 20 Mar 2004
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PostPosted: Sun 01 Jul, 2007 5:44 am    Post subject:         Reply with quote

Jared, how are you defining stiffness? Your use of the term seems to differ from the engineering sense of the term, which is how much a material flexes for a given application of force. This doesn't really vary from one steel alloy to another.

High carbon steels tend to be stronger, and will require more force and/or heat to shape them. They are usually also more brittle, meaning they tend to break rather then bend when cold-worked. Then again, heat treatment affects this too.

Now, I'm getting out of my field of expertise, and will turn it over to the mechanical engineers and metallurgists.

Jim
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Jared Smith




Location: Tennessee
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PostPosted: Sun 01 Jul, 2007 8:40 am    Post subject:         Reply with quote

You are correct about the engineering definition of stiffness not varying significantly from one steel alloy to another steel alloy, especially if they are all annealed. You can influence it a lot with cold working or mechanical deformation, but it is often just assumed to be relatively constant. The real objective to heat treat is to change the stress-strain characteristic of the material. Meaning, that if we are going to bend a sword or strip of metal over a curved form, we want it to be capable of higher strength/ stress so that it does not stretch and break. http://www.key-to-steel.com/default.aspx?ID=C...&NM=43

At least 3 engineering terms are needed to understand this; hardness, (Young's) modulus of elasticity and ultimate strength. Most here are enthusiasts of hardness and already understand it. Elasticity represents stiffness against bending forces. Ultimate strength being the amount of stress at which the material stretches (ductility) and fails if subjected to it long enough (as a phenomenon it generally accelerates if the stress or load is maintained.) Graphs on the 3rd page of this article really help illustrate effects of heat treat for general steels. https://www.asm-intl.org/pdf/spotlights/tempering.pdf


Normally (materials that accept spring tempering) both hardness and strength will go up when imparting spring tempers compared to fully softened or annealed condition. High purity iron tends to just bend once sufficiently strained and be lower in ultimate strength than an alloy. A couple of percent alloying impurities can really change it though. You can heat treat some "malleable iron". http://www.key-to-steel.com/Articles/Art121.htm It still will not behave much like a spring though.

Ultimate strength and modulus of elasticity of most "steels" tends to to be higher than materials called "iron" today. http://www.engineersedge.com/manufacturing_sp...rength.htm

"Impact toughness" and "fatigue life" are some additional factors worth worrying about. Cold working is really tough to predict and best left to empiracle data for the actual material and process. I really hesitate to discuss any of it without data and curves for heat treat of a specific material. I have had to do this a couple of times for flight hardware, and the final result for the actual process was always somewhat different (maybe as much as 20% compared to initial expectations) than what I expected in the beginning based on excellent general data (and consultation with experts who focus on this subject full time) prior to tests. If you can read and retain the information in the following article you will be much more of an expert on it than I am! http://www.collectionscanada.ca/obj/s4/f2/dsk...Q45601.pdf

Absence of evidence is not necessarily evidence of absence!
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