Annealing weirdness; Have a look.
Sept 30, 2008 18:26:10 GMT
Post by Matt993f.o.d on Sept 30, 2008 18:26:10 GMT
Just finished forging and cleaning up the profile of my latest project. As it is substantially larger than my other projects, I wasnt always able to get a perfectly even heat when forging. In addition to this, I found it quite tough to file. I decided therefore to anneal it to soften and stress relieve it.
To anneal the workpiece, I buried it in a small pile of charcoal, and set it alight. The charcoal burned for about 4 hours. At its hottest it heated the workpiece to near the temperature I would normally harden at (I am judging this by colour, which is near a cherry red in my workshops light conditions). It stayed this temperature for around half an hour, then cooled slowly for the remaining two and a half hours (for the first hour the fire was establishing itself).
After removing the work from the ashes though, I was suprised to find that a peculiar marble like runny pattern had emerged on the surface of the blade. This has got me confused as I don't know what it is. I have used this method of annealing on lots of my previous projects, and this hasnt happened.
What do you all think has caused this effect?
I would guess that it is either some form of oxidisation, surface carburisation, or decarburisation. I wouldnt think it was decarburisation, as the charcoal fire would surely give quite a reducing atmosphere with no air supply (it was burning on its own; no air draught, obviously). At no point did the blade get to the sort of temperature that fire scale could form, were it removed from the fire.
If it is some form of damage to the surface of the steel, I have yet to rough grind the blade so surely the layer of affected steel would be removed anyway?
To anneal the workpiece, I buried it in a small pile of charcoal, and set it alight. The charcoal burned for about 4 hours. At its hottest it heated the workpiece to near the temperature I would normally harden at (I am judging this by colour, which is near a cherry red in my workshops light conditions). It stayed this temperature for around half an hour, then cooled slowly for the remaining two and a half hours (for the first hour the fire was establishing itself).
After removing the work from the ashes though, I was suprised to find that a peculiar marble like runny pattern had emerged on the surface of the blade. This has got me confused as I don't know what it is. I have used this method of annealing on lots of my previous projects, and this hasnt happened.
What do you all think has caused this effect?
I would guess that it is either some form of oxidisation, surface carburisation, or decarburisation. I wouldnt think it was decarburisation, as the charcoal fire would surely give quite a reducing atmosphere with no air supply (it was burning on its own; no air draught, obviously). At no point did the blade get to the sort of temperature that fire scale could form, were it removed from the fire.
If it is some form of damage to the surface of the steel, I have yet to rough grind the blade so surely the layer of affected steel would be removed anyway?