How hot is too hot?

Disco Stu

Disco Stu

Joined
Nov 9, 1999
Messages
1,137
OK guys, just got my forge a couple weeks ago and am now rounding up stuff to use for an anvil and tongs. My question is; When I actually begin forging, how hot can I get the steel before I start burning out carbon? Is it inevitable?
 
Some carbon loss is probably inevitable but in normal forging operations it's not a problem. Many people leave their forgings thick and grind away the decarbed "skin". Others, like the Neo-Tribal guy's
forge to a nearly finished edge with no problems (they mainly use charcoal forges though).

The main thing is you don't want to overheat your steel but it is crucial to only work high carbon steel at temps above critical. Overheating, however, causes excessive grain growth and eventually burning and ruining the blade. Working the steel too cold will cause cracking and crumbling of the blade often during the final quench. The one exception to only working the steel above critical is on finishing heats many bladesmiths "pack" the edge with gradually lighter hammer blows at lower temps as the heat fades away.

One thing will help immensely and that is to normalize your blades after forging operations, several times at that.

Hope this helps!

Guy Thomas
 
I wanted to mention one other thing and that is your choice of steel for you first forging projects. It's hard to go wrong with 5160, it forges easily and is more forgiving to inadvertant overheating and when heat treated properly makes an incredibly tough serviceable blade.

Guy
 
Burn some! Get a chunk of the same steel you will be using and heat it up until it burns. Once you see what it does at what color you'll know for sure what it looks like. As soon as you see sparks from the steel sparkle off it you are burning some carbon. Scale that flakes off the surface isnt neccessarily a loss of carbon. Mild steel does the same thing when forged. Actually losing carbon by it precipitating out takes welding heats and higher. Its good to see first hand what it looks like under a watchful eye. Wear a face sheild for sure. Listen to it too. The sound changes.
 
If it comes out of the forge and looks like a Fourth of July Sparkler IT IS TO HOT :D and you will need a new piece of steel.
Bruce
 
Bruce is right!!!

but my smith friends say that If you don't over heat one every now and then you are not working hot enough.

basicly the hotter it is the easier the steel moves, to hot and it sparks and the steel is ruined.

have fun
 
L6,Just stick that perfectly forged blade back into the coals and turn on the blower real high to heat the steel quick,Then have a friend stop by and you forget about the blade for a couple of seconds and then when you remember it pull it out of the fire and it should be about half gone and throwing sparks everywhere.:D
Just ask me how I know this and I will tell you that I have been there and done that and I have more than one T-Shirt to prove it:eek:
Bruce
 
Hehe, I'd also like to see that Bruce. Maybe I'll do as suggested and burn one. Thanks for the info and entertainment guys. I've been doing the best I can with long vise grips and a POS Harbor Freight anvil and it seems I've been working the steel too cold. I was afraid to bring it near critical because I figured some bad shit would go down if I started hiting a piece of steel in a state of flux like that.

Also, about that anvil- I know it's a cast iron piece of crap but what if I welded a hardened steel plate on top? Or would I be better off getting a chunck of railroad track?
 
I've read a lot of sources that say that when the metal is sparking it's ruined and you should start over. I just watched a video of a japanese smith making a kitchen knife, and when he did the welding his metal was seriously sparking. Literally like a 4th of July sparkler (way more than I've ever had). He didn't seem concerned and in fact kind of leisurely brushed it off with a little broom and then started hammering on it.
This isn't so much a problem for me since I built my propane forge but when I was forging with coal I could hardly get a weld to take unless the metal was sparking or very close to it.
Some clarification would be helpful.
There are some oddities about this video also. Like the narrarator says that his flux is borric acid (ok) and iron oxide powder (!). I've always been under the impression that the oxide is bad for the weld so I see no reason to introduce it.

Thanks,
Rick
 
Stu, if the anvil works dont mess with it. the first thing you need is a good set of tongs. do some resurch figure out what you want then watch for it on ebay. I got some very interesting things there.

be careful don't buy any tool if it's cracked(that usualy means it been through a house or barn fire)

next,
flux is a corrosive They add Iron or rust to boric asid or borax in hope that it will deposit some iron on both pieces, getting the weld started, or slow down the the corrosion process saving some matal.

 
Stu, I'm really the last person to answer this because I can't make good damascus.....but...the good welds I have had seem to be in a very narrow window between what I used to consider proper welding temp and flame on time. I see some sparking when it's right. I have to watch though to make sure it doesn't start spewing like a roman candle. I think this is where a lot of the decarb issues come up. I really don't think much carbon gets burned untill you start sparking. If you work the steeel that hot you need to keep a grinding skin on the steel, if not I think you can work it close to a finished edge.

Anyway....my very unqualified 0.02.
 
You must log in or register to reply here.
Back
Top