A few Q's

[Wildernessmedic]

Can't remember or find what threads they were but somewhere on here, a few people told me some info I was wrong about. I'm reading about it elsewhere and want to make sure I have the right info.

 

One subject was the matter of case hardening. Example was from "A birth of a sword" where they say mechanical fullering of a blade removed a hardened layer from the blacksmith hammering on it. This is why mechanical fullering was garbage and not authentic. A few people on here said BS, but i'm reading and experience it a bit. I'm looking at this

http://ethesis.nitrkl.ac.in/1138/1/Heat_Treatment_of_Low_Carbon_Steel.pdf

 

When you work with mild steel/copper it hardens as you work it (work hardening?) So is this something that doesn't apply to hammering high carbon steel?

 

Another subject was something an old school knife making neighbor told me. That using coal or other combustibles are better than gas forges because it adds carbon to the piece being worked. Someone told me this was an old wives tale and BS. But reading that pdf it mentions carbuerizing and adding carbon somehow?

 

I believe someone also said low carbon steel can not be heat treated? If so why do I keep having to anneal some mild steel to be able to work it after work hardening? I see videos of people heat treating and quenching mild steel, is this pointless and achieving nothing?

[Steve Sells]

it does not work harden when forged hot.    We use heat to remove the work hardening when cold forming.  But I will re-read the paper again later, hope I can get past his typos, stating low carbon steel is 1.5 to 4.5%   .  we know that  > 2% is cast iron,.  I know he meant .15 to .45% carbon but still he needs a proof reader. .  

 

Addding carbon is not a fast operation. carborizing take a long time at high temps, what we do have to wory about is carbon burning off with the air around the blade, rather than staying in the steel where we want it.  and I noticed form his testing his highest result was tested around high 40's RhC.

[ThomasPowers]

Generally you scale off steel faster than carbon migrates in.  

 

A *lot* of urban legends out there in bladesmithing-----like the folding and welding *increases* the carbon content in a japanese blade---actually they start with dang near cast iron apx 2% carbon and after all the folding and welding end up with edge material around 0.5%.  

 

Any hot work above dislocation climb temperature totally gets rid of any work hardening---so heat treat will remove it!  The outer layer is more likely to be decarburized, especially for new people who take much longer to forge

 

Edge packing does not make a denser edge.  It can decrease grain size but for modern alloys thermal cycling does a much superior job without the risk of causing cracks from working too cold.

 

Now quenching a blade in the urine of a goat fed ferns for three days works---but just using a brine quench works better and is SO MUCH EASIER and less smelly...

[Wildernessmedic]

it does not work harden when forged hot.    We use heat to remove the work hardening when cold forming.  But I will re-read the paper again later, hope I can get past his typos, stating low carbon steel is 1.5 to 4.5%   .  we know that  > 2% is cast iron,.  I know he meant .15 to .45% carbon but still he needs a proof reader. .  
 
Addding carbon is not a fast operation. carborizing take a long time at high temps, what we do have to wory about is carbon burning off with the air around the blade, rather than staying in the steel where we want it.  and I noticed form his testing his highest result was tested around high 40's RhC.

 

Being the new dummy I am, even I was kind of irritated with this containing typos. So carborizing is above and beyond most blade making, but we have to worry about burning carbon atoms off. So we just make sure we don't let it sit in the forge forever right? Simple is that or is there something else needed to keep them from burning off?

[Wildernessmedic]

Generally you scale off steel faster than carbon migrates in.  

 

A *lot* of urban legends out there in bladesmithing-----like the folding and welding *increases* the carbon content in a japanese blade---actually they start with dang near cast iron apx 2% carbon and after all the folding and welding end up with edge material around 0.5%.  

 

Any hot work above dislocation climb temperature totally gets rid of any work hardening---so heat treat will remove it!  The outer layer is more likely to be decarburized, especially for new people who take much longer to forge

 

Edge packing does not make a denser edge.  It can decrease grain size but for modern alloys thermal cycling does a much superior job without the risk of causing cracks from working too cold.

 

Now quenching a blade in the urine of a goat fed ferns for three days works---but just using a brine quench works better and is SO MUCH EASIER and less smelly...

When you say we scale off steel faster than carbon migrates in....sorry you lost me. Are you saying attempts at carborizing normally makes us lose steel more than gain carbon? If so then that would put the ratio of carbon up still right?

 

Ok so I was combining two different things. Cold working and hot working. While i'm cold working wire it stiffens up. So I heat and cool to get it back to soft. If I was working it hot I would not be work hardening it at all. 

[ThomasPowers]

In normal forging scale forms both in the fire if you have excess oxygen and when the piece is out of the fire being worked on---unless you live in a hard vacuum or in an inert gas habitat...

 

The rate that scale removes the outer layer of your piece is usually faster than carbon moves in from the outside when you are in a carburizing atmosphere in the forge.

 

To make the tortoise win over the hare you need to keep the piece away from Oxygen while being exposed to carbon monoxide at high temps for much longer periods than it's exposed to air during the working of it.

 

For a much more in depth description of the processes involved may I commend to your attention " The Cementation of Iron and Steel" Giolitti, Richards, Rouiller  which will make you full of such interesting tidbits as that you can use diamonds for carburization, you don't have to have CO; but it's a faster method than most.  

 

I have done experiments carburizing real wrought iron at differing temps and lengths of time getting both too little carbon uptake at low temps and too much carbon uptake at high temps and long times  Since modern high carbon steels are so easy and cheap to find; the only reason to get into carburization is to be a crazy historical nut trying to reproduce methods and materials used prior to the Bessemer process,  (BTW "Steelmaking before Bessemer: vol 1 Blister Steel" has a lot on how this was done in what is now the UK)  

 

Now if someone has made the mistake of forging a blade from mild steel  (that cuts off at 30 points carbon not 45) it is FAR better to just start over with a good alloy for blademaking than trying to "gild fewmets." 

 

Now if you are a budding crazy historical nut---whoopee!  We can dig into this in detail until they start getting the pitchforks and torches ready...(I have the books mentioned to hand, as well as Theophilus, Moxon, Biringuccio, Pleiner, Williams,... and have been doing stuff for over 30 years now...)

[basher]

Thomas,

 do you have a book list somewhere?.

 I love looking through your posts to find the affordable books among the rare ones and my shelves sit a little heavier for it.

[ThomasPowers]

Nope but I should create one if nothing else for insurance purposes.  It will be a chore with books down here; books up there, books on short term and long term loan, etc.  When last I was in the UK I managed to add "Foreign Armour in England" pub 1898 while I was in Hay on Wye; probably would have done more but I was playing sherpa to my wife and acted as a book scout for her interests while we were there.