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  • #61
    Just do your torching at night under a tree- trees give off oxygen at night, don't they? Sorry-
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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    • #62
      so in the end it seems i cannot judge the color of steel. after some tinkering one of my burners seems to be producing 1328°c and the color still looks between orange and yellow to me (color-blind?). im not convinced my s-type setup is super accurate but its a vast difference to the 900-100°c i estimated earlier. i have to look for a piece of o1 and see if i can melt it.

      edit: this flame is red for certain reasons but the color it the same in a blue flame. the camera is apparently smarter than i, it sees the probe as white.
      Attached Files
      Last edited by dian; 02-20-2021, 11:48 AM.

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      • #63
        Happened back here after many months absence!

        Just so happens I'm reworking my ceramic chip forge. It's a Flamefast DS130 that has an inbuilt air blower and uses Propane supplied by a high flow regulator at 37 mBar. It is rated at 22 kW which equates to 1.6 kg/H of propane.

        I have successfully hammer welded 1/2" mild steel with it

        Click image for larger version

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        • #64
          Not sure why but the very first ones I made just look hotter.
          no preheat
          no forced air
          plain propane through a .028 mig nozzle.
          Click image for larger version  Name:	IMG_20190424_212128.jpg Views:	0 Size:	2.12 MB ID:	1929755

          was testing new larger dia front nozzles b/c the previous one burnt up a bit
          did silly home home machinist stuff like use a brake hone to polish the
          inside of taper because... why not?

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          Last edited by Astronowanabe; 02-21-2021, 08:36 PM. Reason: words
          --
          Tom C
          ... nice weather eh?

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          • #65
            Originally posted by dian View Post
            not sure what your saying, but please go and measure the flame temp. of a "mapp" torch. nobody has ever seen the number your quoting. thats why you cant melt medium carbon steel with propane. these numbers floating around are a very weird phenomenon and marketing hype. they probably are true in some theoretical or other irrelevant way that i have yet to understand.
            Temperature is NOT the same thing as heat input....

            "X" amount of propane or whatever will ONLY PRODUCE so much heat input (energy). So you may be able to melt a very small piece of steel, but not be able to even get a larger piece hot.

            The "theory" that you dislike, provides the answer.

            First you have the heat capacity of the material, per kg, then you have the heat required to melt it, and finally the heat required to raise it sufficiently above melting. And all during the process you have losses, radiation, conduction, heat carried off in the exhaust gases, heating the furnace area (it has heat capacity also) etc. A small flame, even if hot, probably does not have the ability to supply all that heat in any but the smallest space.

            So your flame temperature is irrelevant unless you can supply the total energy input at the rate required to raise the thing to melting in your furnace.
            CNC machines only go through the motions

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            • #66
              Dian -- I forgot to mention, in my setup there is no regulator at all. Just a hose from the propane tank to the torch. It's an ordinary (cheap) plumber's torch you can get in any hardware store, but it'll go hot enough to braze. When I need real heat, I have oxy-acetylene, but that melts bricks.
              25 miles north of Buffalo NY, USA

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              • #67
                forge will not get hotter than flame. no idea why keep talking about heat input. as mentioned, my big burner must be around 100 kw. it took me several weeks to get the flame that hot.

                awe, what do you weld mild steel at? 1200°c?

                astro, what angle (included) is your expansion flare? how long is it (id1/id2)?

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                • #68
                  Originally posted by dian View Post
                  forge will not get hotter than flame.
                  Forge will not even get as hot as the flame. That's totally irrelevant.

                  How many joules are you putting in that volume how fast, and how many are leaking out how fast into the room where they do no good?

                  Throw that tiny ytong brick into the trash where it belongs. Buy some Kast-O-Lite if you can find it. I'm told "Arelcrete" is a similar product from the U.K., but I have no actual knowledge of it.

                  Half-liter is too small. That's not a forge, it's a night-light.

                  I push about 2kg propane per hour into about 4 liters of chamber, WELL INSULATED. I've got 50 mm thick ceramic blanket lined with zirconium oxide & binder. Front & back are K23 firebrick. (Apology, but I don't know the U.K. equivalent. It's NOT ytong brick, though!!)

                  Now here's what happens in my little (yes, I said "little") forge... The inside heats up to a bright yellow. Cheap non-contact thermometer says 1350 centigrade. Heat (a type of energy) is going INTO the forge lining faster than it comes out into my shop. I put a chunk of steel into the thing, and heat goes from both the flame and from the lining into the steel. Both. There's a dark spot on the forge floor when I pull out a larger bit of steel.

                  Your burners are fine. Your flame temperature is fine. Your "forges" won't hold heat. Make a better one. I know you can!
                  Last edited by Lee Cordochorea; 02-26-2021, 11:38 PM.

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                  • #69
                    Lee has it nailed! Pay attention.
                    CNC machines only go through the motions

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                    • #70
                      Adding to what Lee said, I remember the furnaces at my old job, where they made powder metal. They were lined with a more expensive grade of fire brick 1/2 meter thick on top of silica wool. They ran for an average of 5 years around the clock at 1100C. You could put your hands on them -- the outside was at comfortable room temperature.
                      25 miles north of Buffalo NY, USA

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