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I Forge Iron

Would love some info

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Hi guys, while i dont share your passion for blacksmithing just yet, i have some fairly pointed questions that i'd love the answers to, which i think most of you could answer fairly easily. I'm actually writing a book, and wanted to get my facts straight before proceeding, so, while i get that this isnt really the point of the forum, i hope you'll appreciate my effort to adhere to the reality of how blacksmithing is done.

To begin with i was wondering....

1. I understand that japanese katanas were tempered multiple times before they were finished. Am i correct in assuming that mediaval european swords were also tempered with water? And that this was part of the proscess of adjusting the carbon content of the steel?

2. were tools (axes, bridles, scythes etc) beaten and tempered also?

3. And this is the hard one for me at least - if the final 'temper' on an item needed to be performed in a specific location, could that be done? as in, the item was smithed in a shop, and then heated a final time and tempered somewhere else? *specifically* in a place where there was no shop? could a mobile billows/ furnace have been made in those times in order for the steel to heat sufficiently?

seems wierd i know but there's alot of context, and any answers you guys have would help me out alot. :) thanks

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First of all I think you are confusing tempering with heat treating. Tempering is making the steel softer and tougher after hardening. Heat treating usually includes several thermal processes of which tempering is the last (save when cryo processing is used and even then a follow up temper is highly suggested.)

For modern steels a blade is often annealed before grinding; then normalized (often repeatedly) and then hardened (usually once though some alloys profit from multiple hardening runs) and then it is tempered again often multiple times.

For old steels normalization and annealing may foster grain growth and so hardening after forging may make more sense. In Europe there was also a one step hardening and tempering process sometimes used called an interrupted quench.

Some japanese swords were not tempered at all after the hardening process using the soft spine to help the glass hard edge to not break as often.

As for medieval european blades: a wide number of quenchants were used for hardening. There are several dozen renaissance ones listed in "Sources for the History of the Science of Steel" C.S.Smith, I suggest you ILL it. (Basicly quenchants devolve into brine, water, oil, air)

Heat treat doesn't change the carbon content of the steel---if done right! Decarburization can happen if done wrong.

Cutting tools were heat treated, axes, chisels, shears, etc. Items like bridles were made from low carbon wrought iron and so heat treating them was useless---you take low carbon wrought iron and heat above critical and quench it and it's just as soft as before you did so---if it had been heavily work hardened it would be softer afterwards!

European scythes were a special case where they were often left fairly soft and then the edge was pounded down cold work hardening it and allowing it to resist chipping when hitting a rock and being able to fix it cold in the field with a small stump anvil.

You can heat treat anywhere you have the facilities to do so----a trench forge in a back yard and a puddle of water will work. HOWEVER the person heat treating had better really know their stuff!

Note that it's very important to temper as soon as possible after hardening as a blade can shatter just sitting on the bench from hardening stresses. The japanese that didn't temper their swords got around this by using a fairly low carbon bladesteel and hardening only the edge allowing the softer spine to help keep a piece from shattering.

Edited by ThomasPowers
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