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Stainless Steel Woodstove ?

Post in 'Classic Wood Stove Forums (prior to approx. 1993)' started by jeepin1121, Jan 28, 2012.

  1. StihlHead

    StihlHead Guest

    Someone posted about building a copper wood burning stove on another metallurgy forum, and the consensus was that copper is just way too expensive and it gets too soft at the required temps for secondaries to burn (it becomes plastic). Also from a design perspective, copper is just too good a heat conductor to allow temps to reach the needed temps for secondary combustion to occur and the plastic/deformity issue would not really be an issue. So in the case of designing EPA type wood stoves, copper seems to not be the choice in materials with the added requirement for a firebox material with a lower heat transfer rate to allow temperatures to get high enough to burn wood cleaner.

    Reverse-intuition strikes again when it comes to EPA stoves. Lower heat transfer metal allows for higher temps in the firebox to burn cleaner and more efficiently. Doh!

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  2. Hass

    Hass Minister of Fire

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    How about Aluminum?
    Easily welded. Great conductivity, 95% of people in the world would believe it's stainless on first look. (and probably many looks thereafter)

    Kidding...
    They use regular carbon/mild steel for a reason ;)
  3. StihlHead

    StihlHead Guest

    No good... Al has a really low melting point @ 1200 F. One overfire and you would have a raging inferno. But it would be nice to be able to make a stove out of beer and coke cans!
  4. MasterMech

    MasterMech Guest

    I occasionally do some TIG work on copper sheeting at work. Argon is the universal gas of choice for TIG. Does anyone still use Helium? That's old school and how TIG welding was orginally know as Heli-Arc welding. You definetley need some serious current. Like 200+ amps while working with 1/8" material. That means a liquid cooled TIG torch too. Usually need to pre-heat all but the smallest pieces and it helps to have a graphite plate or something else that is a thermal insulator (but will tolerate extreme heat) to place under the work. It is not a fun process. The torch angle and arc length are very critical. Too much heat will boil and oxidize the copper and too little will never get a stable pool to work with. Your filler rods should be super clean. With TIG gloves, the heat is so intense that even gripping the back of the torch as far away from the arc as possible, I have to stop every minute or so to cool down my hands. That's a bummer cause once you get the process rolling, the last thing you want to do is interupt it and start again.

    It's such a nasty metal to weld I would exhaust every alternative means before setting on welding a joint.
  5. Dune

    Dune Minister of Fire

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    Helium is not old school at all for certain applications.
    Aluminum always welds better/easier with helium.
    Copper and high copper content alloys benefit even more from the use of helium.
    Using helium to tig is essentialy the same as having 30% more amperage at your power source, without having the torch have to carry the extra current.
    200 amps for 1/8" copper is so marginal that it does explain a lot of your issues, especialy with copper. Is it a transformer power source as well (such as a synchrowave), adding to the agony?
    My main welder is a 425 amp inverter, which is equivelent to 550 amp transformer.
    Even my little 200 amp gas cooled inverter puts a 250 amp synchrowave to shame, and easily welds 1/2 inch or thicker, with pre-heat.
  6. Crane Stoves

    Crane Stoves Burning Hunk

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    this member answered this perfectly, the main reason stainless is not used is because it does conduct heat well and would need to be thin sheet metal stainless like used on the old Petit Godin's, stainless is also very expensive to buy and even more expensive to work with (requires heliarc / tig welding, cant be drilled effectively, etc). even if you had free stainless available its not wise to use it to build a heating stove (a cooking stove maybe were you dont want to conduct heat to the outer parts of the stove to burn your hands when frying an egg might be OK to do) LOL hope that explains it.... GL
  7. Dune

    Dune Minister of Fire

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    I agree with your post for the most part, but for clarity; yes stainless is harder to drill, but is certainly doable.
    As for welding, I chose stick, MIG or TIG depending upon the size of the job (MIG for large jobs) thickness of the metal (stick stainless is easy and produces beautiful welds on thicker metal) or the perceived quality, thin metal, or out of position weld ( TIG is best for out of position or thin metal).
  8. Crane Stoves

    Crane Stoves Burning Hunk

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    make no mistake.... welding stainless is an art and requires some degree of skill (trying to stick or mig a stainless stove would most likely buckle the material) and ive never heard of a machine for homeowners that could effectively weld stainless, you can stick cast iron too but that does not mean it can be done for safe long term use in a stove that heats your home. drilling stainless can be done if you have a Bridgeport in your backyard.... if not, you will just loose all your hair and enter a sych ward at the local hospital LOL. no sir...stainless steel should not be used as a project stove to heat your home! any Stove Company or Stove Manufacturer like myself will say the same thing...
  9. Dune

    Dune Minister of Fire

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    Like I said, I agree with most of your post.
    Not saying to make stoves out of stainless.
    As to the welding lessons though, you are barking up the wrong tree. I make everything and anything out of stainless steel
    I MIG, TIG or stick, depending, as I said.
    The welding process chosen does not determine warpage, total heat input versus metal thickness does, but there are ways to aleviate that, such as heat sinks. Contrary to your opinion though, TIG inputs MORE heat than either MIG or stick.
    I don't keep my Bridgeport outside, it would get too rusty, but regardless, stainless steel drills perfectly well with a sharp bit, and correct speed and feed rate. No, it is not easy for beginers or the inexperienced.
    As to the cast iron, I have been repairing cast iron for over 30 years and have burned many a box of sticks doing so, and repaired uncounted stove parts. Stick is the prefered method of welding cast iron whether you realise it or not.
    MasterMech likes this.
  10. Crane Stoves

    Crane Stoves Burning Hunk

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    agree with you dune... but ill stand by thoughts that your a pro metal fabricator (and most people are not). Stick is preferred for welding cast iron but unless your very good folks will whined up with a puddle of ugly spatter and cast iron that has been compromised around the area of the joint (10 times more brittle then cast iron already is).... i damb sure wouldn't want to overfire a welded cast iron home heating stove (at least on any structurally important parts like the combustion chamber) YIIIKES! but it is good that pro's like you exist to help the rest of do things that simply shouldn't be done by a novice <333
  11. kettensäge

    kettensäge Feeling the Heat

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    Interesting thread.
    I suppose you could build a plate steel stove and have it copper or nickel plated.
    Not that I would do it, but I guess that way you can have the look and thermal performance without all the headaches?
  12. MasterMech

    MasterMech Guest

    Funny, I've got quite a few items around work that were glued together with a Millermatic 140 (110V). I imagine any small 140amp MIG would do equally well. Machine is good up to 1/8" stainless.
  13. Crane Stoves

    Crane Stoves Burning Hunk

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    Yea i do like the new 110 machines from Lincoln and Miller, ive never tryed stainless with them but i guess id attempt it if i had reason since i had to sell my trailblazer.... Im not sure i would trust any welds on stainless that were not tig welded though but thats just me (im sure someone skilled could use several methods) just in my day Tig was always the proper way to weld stainless.
  14. MasterMech

    MasterMech Guest

    Tig is fantastic on stainless (especially thin stainless) because you have zero spatter and much more control over the heat. You can make some very pretty welds with the Tig torch. Thin stainless also requires tricks like back-purging from time to time to prevent the weld from oxidizing and that usually goes along with the TIG process. But where looks/spatter don't matter and/or access is tough, I rock the MIG all the time. Helluva lot faster and if it's set right, the welds are every bit as strong.
  15. Dune

    Dune Minister of Fire

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    Spatter can be eliminated when MIG welding stainless by using one of several tri-mix gases. Argon-CO2 mix is going to cause excessive splatter (and other problems) when MIGing stainless steel. Most manufactured S.S. items are robot MIG welded.

    TIG can do miracles to stainless, but stick actualy works very well too, for thicker metal. Stick stainless' main limitation is out of position.
    It doesn't want to go up hill at all. Some people have developed a method of welding vertical with stick, but I don't trust it for structure.
    It seems more like a series of large overlapping tacks than a true 100% fusion weld. I will often whip out a TIG torch just to weld the verticle portion of an assembly which can''t be rotated into the flat position.

    The use of aluminum or copper heats sinks in contact with the metal to be welded can reduce distortion greatly, some shops going as far as having thick aluminum bench tops. Patience is your best friend when dealing with very thin stainless.

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