Deleted
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scale
Jul 30, 2008 20:31:53 GMT
Post by Deleted on Jul 30, 2008 20:31:53 GMT
I'm having a big problem with the scale that builds up when forging and heat treating. when forging its easy enough to brush off but after i finish shaping with the files and grinders and go to normalize the scale pits the blade and ruins the nice surface. is there anyway to control this?
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scale
Jul 30, 2008 20:50:23 GMT
Post by swordboy bringer of chaos on Jul 30, 2008 20:50:23 GMT
the ones you should ask are Sam Salvati or Brenno
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Deleted
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scale
Jul 31, 2008 2:54:34 GMT
Post by Deleted on Jul 31, 2008 2:54:34 GMT
well this way i get an answer from everyone not just 1 person.
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scale
Jul 31, 2008 16:22:10 GMT
Post by Matt993f.o.d on Jul 31, 2008 16:22:10 GMT
When you put the blade in the forge, you are putting it too close to the tuyere (your air inlet).
A forge fire has three layers. A carburising layer, furthest away from the tuyere, where their isnt much free oxygen, and the fire is at its coolest. Here the steel will tend to oxidise (grow scale) least, and may gain some carbon in its surface.
The next is the neutral layer. This is between the carburising and decarburising layers, and is where you really want your steel to go. The blade will not form too much scale, and will hopefully neither gain nor lose carbon.
The final layer, and the one that is causing you trouble, is the decarburising layer, closest to the tuyere. The fire is at its hottest, and is also full of lots of free oxygen due to the air blast, which will quickly cause lots of scale to form on your steel. Also, you are seriously in danger of decarburising your steel to an unnacceptable degree.
To avoid these problems, try using less of an air blast when heating for heat treatment and forging. You should also avoid putting your steel close to the tuyere. Try to have an inch or two of fuel between your tuyere and your steel.
That should solve your scale issues.
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Deleted
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scale
Jul 31, 2008 20:20:56 GMT
Post by Deleted on Jul 31, 2008 20:20:56 GMT
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scale
Jul 31, 2008 21:06:25 GMT
Post by Matt993f.o.d on Jul 31, 2008 21:06:25 GMT
Anti scale powder?
Thats clever, but quite defunct when you really should just put the blade away from the air blast. Its easier and cheaper! Seriously, when forging or hardening, I put all of my blades and other forged items around two inches above the tuyere, with fuel separating them, and I have NEVER had excessive pitting or scale problems. Indeed, most of the scale on my workpieces forms AFTER I have removed them from the fire!
By the way, if you can't get enough heat without putting the steel close to the air blast, then either your air blast isnt strong enough, or your fuel is inappropriate. If you are using hardwood lump charcoal, good bituminous or anthracite coal, or coke breeze you shouldnt have a fuel problem, though. Just a thought.
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scale
Aug 1, 2008 18:20:40 GMT
Post by Matt993f.o.d on Aug 1, 2008 18:20:40 GMT
Another thing that might be causing you trouble is if you are working outside in daylight, the color you see on the metal is duller than when viewed in lower light conditions (such as those found in the dimly lit smithy; it is dimly lit for a reason!).
This means that your metal is actually a lot hotter than it appears to be, and will thus form scale more readily. I have seen iron that looks cherry red outside on a sunny day that is actually at WELDING heat! You may think your steel is at a normal temperature, but is actually much hotter. That could be why you are getting excessive scaling.
Just a thought. I'm sure you've thought of this already.
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Deleted
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scale
Aug 1, 2008 18:28:39 GMT
Post by Deleted on Aug 1, 2008 18:28:39 GMT
i try to cast a shadow over the forge when im working on a sunny day. i wish i could work at night but the neighbors would be pissed!
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scale
Aug 1, 2008 19:58:49 GMT
Post by Matt993f.o.d on Aug 1, 2008 19:58:49 GMT
You could set up a canvas awning over your working space. It only needs a little bit of a shadow. The sort of shade a wall or a tree offers is usually enough. I suspect that if you arent putting the metal too close to the tuyere, as you probably arent, then it is probably the daylight making you underestimate the temperatures that is contributing to the scaling problem. Bear in mind that scale doesnt usually form at HTing temperatures, so the formation of scale, particularly scale serious enough to cause difficult-to-remove pitting is a strong indication of overheating.
Can you possibly post a pic of the sort of scale damage you are getting?
Good luck!
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