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28478Re: [hobbicast] unable to superheat melt

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  • edyn maniapoto
    Sep 1, 2003
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      > While I'm happy my
      > propane furnace was actually able to melt metal, I'm
      > a little
      > concerned with it's performance. From reading other
      > posts the 20
      > minutes it took for the aluminum to melt seems OK.

      >Snip----Hey Dean
      Don t know if this helps?
      From what I can tell your Burner is operating
      correctly, or it wouldnt melt ally in the 20 min
      timeframe from cold.My monster Burner melts a 3/4
      full Steel Crucible(10mm Thick)of ally in about that
      time frame. I had a burner prob when I first got mine
      together and it wouldnt heat half the area of a 2mm
      thick cookie tin in half an hour,when I put a small
      chunk of ally in it,it took 40 mins before the ally
      just started warping. The problem was low fuel supply.

      > 5 minutes before pouring however and the metal was
      > freezing as I was
      > pouring the third 1/2 pound ingot. I was pouring
      > pretty quick too!

      Snip---How Full was the crucible? more ally charged
      in the crucible usually means longer melt time?
      I find that Smaller melts cool and solify faster,
      Bigger melts usually give more working time.

      > I suspect either my furnace isn't insulated enough
      > to heat much
      > higher than melting temp or my burner isn't kicking
      > out the BTU's.
      Snip----If your burners working correctly yor furnace
      doesnt need to be super effeciant, I can run my
      furnace with the lid off it and the burner will have
      the 10mm thick steel crucible up to a red heat in
      minutes.
      >
      > I'm using a stainless steel stock pot with 2 inches
      > of commercial
      > 2800 degree refractory
      > -----Snip My walls are approx 4"thick,The Temp
      rating of the refractory is 1650 deg/c. Usually higher
      temp rated refractorys are poorer heat insulaters,They
      are used to line blasting faces and are backed up with
      lower temp rated refactorys for insulating heat. your
      2" walls should be ok though!..as far as im concerned
      a furnace is just somwhere to put a crucible to blast
      with heat....he he

      > burner is a modified Reil sidearm burner (naturally
      > aspirated). 12
      > psi seems to be the sweet spot as far as I can tell.
      > Oh ya, I'm
      > using a 4" diameter schedule 40 pipe crucible and on
      > my second
      > attempt I had most of the exhaust port covered with
      > a plinth - same

      ---------Snip ..Your Base plinth should raise the
      Crucible into a position so it can recieve heat from
      the burner 1/3 from the bottom of its base.
      >
      > I'm going to use the wifes hair dryer for a forced
      > air melt tomorrow
      > to eliminate the burner from the equation. For
      > those familiar with
      > the modified sidearm burner, I couldn't find a 1.25"
      > x 1.25" x 0.75"
      > reducing tee so I had to use a 1" x 1" x 0.75" one.
      > As a result I'm
      > getting less airflow than the design calls for.

      Snip-----The Burner is burning at the tip of the tube
      right??.....NOT INSIDE THE TUBE!!!!!!, by the way from
      what I hear Blown burners are unreliable and are hard
      to tune - I think Ron Reil actually said that
      somewhere on his site.
      > If it turns out my burner isn't the problem, would
      > coating the
      > refractory with ITC-100 be enough to save this
      > furnace?
      Snip-----I think if anything you may just have to wait
      a little longer until the entire melt is heated to a
      point where its fully liqufied .....but hey thats just
      my opinion!
      Edyn.
      >
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