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Thread: Help needed with heat treat forge

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    Senior Member Sentry's Avatar
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    Help needed with heat treat forge

    Aside from being hung up on this being a forge or a furnace;

    I'm in the middle of my heat treat forge (for argument sake) build and need some advice. I'm reaching 1050 degrees Celsius max but need to acheive 1080 degrees Celsius to heat treat 12c27. You can see from the photo below, the burner is vertically mounted through a 50mm hole and there is no opening on the back of the chamber.





    Keep in mind it's still a work in progress so I'm aware it looks like hammered crap. I'm using the brick in front of the door to restrict the amount of heat going out, and turned the airflow restrictor all the way OPEN to get the temp up (closing it produces dragons breath but the temp drops significantly). I can turn the regulator up a few knotches but my main question relates to the orientation of the burner and the lack of ventilation on the back. Is there a better way to set up the burner? Do I need a rear vent?
    Going off Corins post in another thread, maybe laying the burner horizontal might do better?

    Quote Originally Posted by Corin Urquhart View Post

    Anyhow. If you are going to use 1 burner, placement will be everything.

    I would think the best way would be to mount the burner horizontal towards the front and directed to the back, so the flame heads down the forge, above the blade and the heat comes back and out the door.
    On a side note (and this may help) the flame pops every now and then, and the heat is not consistent through the chamber (fairly big variations).

    1050 degrees Celsius is so close yet so far. Thoughts?
    Last edited by Sentry; 05-05-2018 at 18:46.
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    Knifemaker Tarrabah's Avatar
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    My original forge/furnace/kiln, was very similar in design, I used to have the burner at the front facing in, it worked fine for a couple of years, no idea what temps I was getting, I used a magnet to tell me when the blade was ready

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    Knifemaker Substance's Avatar
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    What regulator are you using
    Just Turn up the gas pressure and open the air and it should get hotter
    Also try using a pipe or similar in the forge so you don't have direct flame hot spot on your item being heat treated
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    Senior Member Sentry's Avatar
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    I couldn't tell you what regulator I have, aside from it being the Gameco BKIT5 burner.

    https://www.artisansupplies.com.au/p...onomy-burners/

    I'll definitely turn the gas up but the question in my head relates to the construction of the chamber. I'm getting the feeling it's one of those cases where if it works, it works and if it doesn't, try something new. A little bit of math and a whole lot of art.
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    A lot of forges have a refractory paint (FTZ or Zircoat) on the inside. This reflects the infra red back into the forge. It might help.
    I got my last lot of Zircoat from the Potters Market in O'Connor.
    Also for a naturally aspirated forge, there needs to be 7 times the exhaust area than entry. If the exhaust is restricted then it creates a back pressure that slows down the gas torch.
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    Knifemaker Tarrabah's Avatar
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    Just after I got to Tas, I stumbled on a shop selling a deceased estates library, most of it was metallurgical/engineering type stuff, I bought everything relevant to a knifemaker/machinist wannabe, one of the books was on Furnace/forge/kiln building, I was going to build an Underfired Reducing furnace to HT my blades, the furnace would've had a table in the centre to put the work on, and the burners would've been underneath the table, and directed up on an angle, that would've circulated the heat better(underfired),and I've forgotten what the reducing part exactly was, but basically the design would stop the scale from forming by using up or eliminating any spare oxygen????, it was a great design, and fantastic book, I wonder if I've still got it?.

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    Senior Member Sentry's Avatar
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    Quote Originally Posted by Jez View Post
    A lot of forges have a refractory paint (FTZ or Zircoat) on the inside. This reflects the infra red back into the forge. It might help.
    I got my last lot of Zircoat from the Potters Market in O'Connor.
    Also for a naturally aspirated forge, there needs to be 7 times the exhaust area than entry. If the exhaust is restricted then it creates a back pressure that slows down the gas torch.
    Thanks Jez. I'm using refractory bricks (3 off. I have one more to cut down) so I think I have that covered. The bricks are tiled in such a way they should prevent any heat going through the white fire bricks. Will certainly keep it in mind. The info about the exhaust area is good to know. In terms of area, it means pipe inside diameter and not the diameter of the flare?

    Quote Originally Posted by Tarrabah View Post
    Just after I got to Tas, I stumbled on a shop selling a deceased estates library, most of it was metallurgical/engineering type stuff, I bought everything relevant to a knifemaker/machinist wannabe, one of the books was on Furnace/forge/kiln building, I was going to build an Underfired Reducing furnace to HT my blades, the furnace would've had a table in the centre to put the work on, and the burners would've been underneath the table, and directed up on an angle, that would've circulated the heat better(underfired),and I've forgotten what the reducing part exactly was, but basically the design would stop the scale from forming by using up or eliminating any spare oxygen????, it was a great design, and fantastic book, I wonder if I've still got it?.
    Sounds interesting. If you find it, let me know the book title and author!
    ● Always outnumbered, never outgunned ●

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