Announcement

Collapse
No announcement yet.

Annealing hard metal in a fireplace?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • x39
    replied
    Evan, while you make a valid point, the fact is that anyone annealing a chunk of steel in the fireplace probably doesn't really know its exact alloy to begin with.

    Leave a comment:


  • Evan
    replied
    While all of the usual alloys of iron can be annealed it isn't always just a matter of letting it cool slowly. Iron goes through phase changes as it cools and forms different allotropes depending on the cooling rate and the presence of other elements. Some alloys must be very carefully cooled at exact rates and held at certain temperatures before further cooling. Some alloys must be cooled no faster than a certain number of degrees per hour and can take days to reach a normal annealed state. Some alloys are partially quenched in molten lead to prevent the formation of iron carbides then cooled further.

    Leave a comment:


  • Ghop Shop
    replied
    I have annealed a lot of ball bearings in my Ashley wood burning fireplace by getting them red hot and dropping them in a coffee can full of ashes. I had no problem drilling and tapping them after that treatment.

    Gayle Hopson

    Leave a comment:


  • x39
    replied
    Originally posted by pcarpenter
    I think I would be tempted to make a little "tunnel" out of fire brick and sort of pack the thing in charcoal and light it up.
    I've used charcoal briquets many times with good results. I drilled a bunch of holes in an old steel bucket. I put a bed of briquets in the bottom, light them and let them start to ash over, put the part in, then cover with more briquets. When they're going pretty good I throw a piece of steel plate over the bucket and let sit until cool. This method has never failed me.

    Leave a comment:


  • pcarpenter
    replied
    I thought most (all?) steel alloys return to their annealed state, but the annealing temperature goes up according to the alloying elements. So carbon steel anneals at around 1300°F and tool steels anneal around 1600°F.
    Robert-- like I said, I am no metallurgist and the one thing I am thinking of may be a poor example, but I recall some experiments here with welding tool steel (cutting bits). It might have even been your experiment?? I think the premise was that they did loose hardness that might render them not so ideal as tool bits, but would not go back to a real soft pre-hardening state. It may be that some of the alloying elements (molybdenum, aluminum etc.) that are in higher than normal percentages in tool steel make it a rare bird that has nothing to do with old truck axles though

    Paul

    Leave a comment:


  • torker
    replied
    I've annealed a pile of steel in my woodstove. I have no idea how hot it gets.
    all I know...i leave it in all day.
    I keep lifting it to the top of the fire everytime I put wood in it.
    At the end of the day i pull it out and plop it into a bucket of cold water...LOL
    NO!!! Just kidding...I put it into a bucket of warm ashes that I scoop from the fire.
    Works every time.
    Russ

    Leave a comment:


  • lazlo
    replied
    Originally posted by pcarpenter
    I am no metallurgist, but I know some alloys do not return to their annealed state well. It sounds like this may just be a medium to high carbon steel.
    I thought most (all?) steel alloys return to their annealed state, but the annealing temperature goes up according to the alloying elements. So carbon steel anneals at around 1300°F and tool steels anneal around 1600°F.

    Leave a comment:


  • Nick1911
    replied
    I once shoveled ashes out of my woodstove after it had been out for a week. I could put my hand on top of the ashes and not feel any heat. I shoveled them into a plastic bucket, and melted it. The bottom of the stove was still quite warm. I've since switched to a galvanized steel bucket.
    My father caught the house on fire doing that once. Shoveled week old ashes into a metal bucket, then set it outside, next to the house.

    The fire was contained before significant structural damage occurred. New siding and a few new studs were needed.

    Leave a comment:


  • pcarpenter
    replied
    I am glad to see a couple of folks addressed the specific question of whether a presumably forged axle shaft would anneal. I am no metallurgist, but I know some alloys do not return to their annealed state well. It sounds like this may just be a medium to high carbon steel.

    I think I would be tempted to make a little "tunnel" out of fire brick and sort of pack the thing in charcoal and light it up. This scheme would allow you to heat it evenly and to use forced air (maybe a leaf blower at idle) at one end to generate the needed heat pretty quickly.

    The only concern I might have (and maybe someone could address) is whether the charcoal might tend to provide enough carbon on the exterior to case harden it if left in there. I think after it reached red heat I would pull it and bury it in dry sand to slow cooling. I have done that with smaller parts and it seemed to work well.

    Paul

    Leave a comment:


  • Mcgyver
    replied
    Originally posted by Circlip
    Sorry, the fireplace trick does work. Fuel and location may change but the fireplace was the standard annealing furnace for Muddle Ingineers in the UK before the "Central Heating" brigade took over.

    .
    I can accept the fireplace gets hot enough, like i say, haven't gone the route before, but the point is not will it work for any annealing, but will it work for a 2 1/2' length ......that's a very big fire! It takes a fair bit of heat to get big chucks to red all over...not sure how you'd make a fire to engulf all 2 1/2' at temp as well as have it buried in coals for a slow cool.

    Leave a comment:


  • mwechtal
    replied
    Can stay hot a LONG time

    Originally posted by Fasttrack
    I used a wood burning forge, but I think a fireplace would work too. Like you mentioned, with the damper open, the doors closed and the vent open, you can get things going real well. You'll just have to work a little more at it.

    Once I got my axle a nice cherry red, I dropped it in a bucket of kitty-litter. I came back 24 horus later and it was still warm! Anyway, it was soft as butter and easy to machine.
    I once shoveled ashes out of my woodstove after it had been out for a week. I could put my hand on top of the ashes and not feel any heat. I shoveled them into a plastic bucket, and melted it. The bottom of the stove was still quite warm. I've since switched to a galvanized steel bucket.

    Leave a comment:


  • Fasttrack
    replied
    I used a wood burning forge, but I think a fireplace would work too. Like you mentioned, with the damper open, the doors closed and the vent open, you can get things going real well. You'll just have to work a little more at it.

    Once I got my axle a nice cherry red, I dropped it in a bucket of kitty-litter. I came back 24 horus later and it was still warm! Anyway, it was soft as butter and easy to machine.

    Leave a comment:


  • lazlo
    replied
    Originally posted by GadgetBuilder
    The fire was much hotter than I expected - the axle actually turned dull red.
    Steel's annealing temperature (when the carbides go back into solution) is 1341؛ F, which is dull red

    Anything below that temperature won't do much.

    Leave a comment:


  • GadgetBuilder
    replied
    I've annealed a car axle in my fireplace and there wasn't much to doing it. I laid the axle on the grate (about 4" above the bricks), built a fire using relatively small wood (so it would burn fast and hot) and kept it going for a couple hours. The fire was much hotter than I expected - the axle actually turned dull red.

    I left it on the grate over night to cool slowly. The axle, which had been really difficult to cut before annealing, turned very nicely afterward and became several MT3's for my mill tooling. The axle spline is visible on the leftmost holder:




    John

    Leave a comment:


  • A.K. Boomer
    replied
    I think it all depends on this question --- "can you get it glowing cherry red"

    If so then your fireplace will work just fine, some things to consider

    hardwood creates hotter coals that last much longer -- something like pine will due for a piece thats not as thick but a fiery bed of hardwood coals will get some fairly large material cherry red hot.

    Leave a comment:

Working...
X