Propane ribbon burner hot enough to melt pig iron?

Discussion in 'Home Foundry & Casting Projects' started by Jack3M, Apr 5, 2019.

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  1. Apr 5, 2019 #1

    Jack3M

    Jack3M

    Jack3M

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    Been learning about the burners and they seem very efficient. But I cannot find temperatures produced and only one person who melted steel....and his crucible.

    Anyhow, my forge is fired with a Harbor Freight weed burner and I can cast bronze and brass. Tried to melt some scraps of cast iron I have and it just wouldn't quite get there. Really would like to be able to add cast iron to my repertoire, as there are times I want to use it for the finished product.

    I really do not want to mess with an oil fired burner even though they are basically the same, blown fire.
     
  2. Apr 6, 2019 #2

    Cogsy

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    The temperature of the burn isn't really the issue (propane goes up to almost 2000 C in air) but the amount of heat you can produce at once. Propane has a lot of stored energy (comparable to oil or gasoline per kg) but it is far easier to burn more oil at a a time than gas. For example, a match contains a bit less than half the stored energy per kg of propane and will burn in air at around 600 C, which is hot enough to melt lead. However, to get the same amount of energy from matches as burning 1kg of propane per hour, we would need to completely burn around 4 matches every second. Obviously it's far easier to supply the propane at that rate than matches.

    The same holds for oil as propane, it is far easier to supply 4 kgs of liquid oil/gasoline per hour than 4kgs of gas. If you don't supply the energy at a fast enough rate, even though the temperature of the flame is high enough, the iron will never absorb enough heat to melt as excess is lost to the environment. If your furnace is getting close then maybe you could add an additional burner to supply more energy but you might not be as close as you think. As a material reaches it's melting point, the amount of energy required to actually melt increases dramatically (called the latent heat). For iron, the energy required to raise a 1g peice by 1 degree C is 0.45 J, but once it reaches melting point, the energy required to melt 1g of iron without changing its temperature at all is nearly 14 J - over 25 times higher!
     
  3. Apr 6, 2019 #3

    goldstar31

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    Of course Cogsy is right but but you haven't really done your homework.

    Iron ore was smelted using charcoal but it was a lumpy business until Henry Bessemer introduced lots of hot air into coke ovens to rid impurities and into steel.

    Brought up in a family who earned their pennies in iron and steel making( until they got more sense!), I was visiting Llandudno in North Wales- look you Boyo and had a visit to the old copper mines on the Great Orme and asked the million dollar question of you the Romans( and their child miners) smelted the copper ore ( which has a higher melting point than iron ore)

    Basically that part of North Wales is pretty short of trees for charcoal and I got interested and curious.

    I found that the heat source was actually brush wood-- with lots of breeze from our side of the Atlantic Ocean.

    So as Cogsy rightly says-- Lots of heat and even more air.

    Playing with a weed burners is not really hot enough.

    I's settle for a chemistry approach and use a ferrite bomb of rusted iron filings and aluminium turnings. It was a damned close thing for London in 1940-- if you read your history book.

    My opinion- of course

    Norm
     
  4. Apr 6, 2019 #4

    Jack3M

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    Sir, I am by no means "playing" with a weed burner. I have scratch built 4 projects with my 'toy' burner which works quite well for what it is and it's current use along with a plethora of other items cast. My terminology may not always be correct, but I get the project done.
     
  5. Apr 6, 2019 #5

    goldstar31

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    Apologies.
    Perhaps my longevity is partly due not to take what I assess as unnecessary risks .
     
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  6. Apr 6, 2019 #6

    Jack3M

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    I never mentioned the forced air part, which is critical to the efficiency, and as Cogsy mentioned it is air that makes the difference and the ability to dump enough fuel. Soooo with what he and others have said, it is the blown in air with any burner type. Whereas, with the weed burner, the furnace is designed with a venturi effect that draws in air and increases the efficiency of this cheap burner. Distance on the burner in the venturi is critical for enough heat. But this is a passive, inexpensive, moveable, system that achieves temps high enough but not high enough for cast iron.
     
  7. Apr 16, 2019 #7

    Wizard69

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    With respect to forced air, back in my zinc foundry days just about every burner and furnace was operating with some sort of air supply. That could have been a fan based burner unit for the zinc pots or point torches for heating specific parts of the machine. Your weed burner is most certainly a toy in this context, in fact any normally aspirated burner will be at a significant disadvantage. Now zinc alloys melt at a much lower temp compared to iron but the point here is that you need efficiency to keep cost under control in industry.

    You may have options such as adding another burner but that might not work out as well as you would hope. Much depends upon the design of the furnace.

    Insulation is another thing that might help. A poorly insulated furnace can loose heat at a significant rate. On top of that an interior coating that reflects the heat energy can help. How much this would help with iron is not known but industry does look to minimize costs so insulation becomes a cheap avenue to success.

    In any event do be careful! As others have said there is a lot of heat in iron and that can lead to things going bad real fast compared to zinc or aluminum.
     
  8. Apr 16, 2019 #8

    goldstar31

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    Centuries ago, I had bought B. Terry Aspin's book- the Backyard Foundry.

    Possibly still worth a read as he dealt with proper iron melting in the classic way and described using tuyeres.

    Me??? No way. I recall a friend of mine being part of a huge steel casting process- and two blokes simply disappeared- when the mould broke.
     
  9. Apr 16, 2019 #9

    goldstar31

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    Foundrywork for Amateurs by Aspin is available as a pdf. Lots of information if you want it

    Norm
     
  10. Apr 17, 2019 #10

    Preston Engebretson

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    As a past foundry instructor and one that has cast castiron, you will very likely need coke...many power plants
    have coal that you can use...

    To get enough heat the amount of propane or waste oil needed would be very high...may be possible, but the system
    to do so would be frought with serious danger in my opinion...for an amateur...

    Best Regards,

    Preston
     
  11. Apr 17, 2019 #11

    Jack3M

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    Thanks Preston, I think I will just stick with what I can already play with. If I want something bad enough in cast iron I have local foundries.
     
  12. Apr 17, 2019 #12

    Preston Engebretson

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    That is what I would do Jack

    Best Regards,

    Preston
     
  13. Apr 18, 2019 #13

    Cogsy

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    Home casting of iron using waste oil burners is reasonably common with well constructed furnaces. Not something to be taken lightly but certainly not out of the realms of possibility.

     
  14. Apr 18, 2019 #14

    Preston Engebretson

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    Thanks Cogsy...I stand corrected...been out of pouring since 2009

    I use to Teach and Assist at Glassell with the Houston Museum of Fine Arts...

    Need to revisit pouring iron, as we were working on some very nice SS nozzles when
    I last was pouring...

    Thanks for the link and update.

    Preston
     
  15. Apr 18, 2019 #15

    aonemarine

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    Ive been melting iron with a forced air propane burner for about 5 years now. Once you figure out how to get up to temperature its actually pretty easy.

    if your getting it to a gooey bubbly type semi solid blob then yes that is all most there. Just a wee bit of air blown in should finish the job. I use a hair dryer set on low speed to do it with my Reil burner....
     
  16. Apr 19, 2019 #16

    jacobball2000

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    You're right air matters. And the more pure the oxygen "which you are using" the hotter
     
  17. May 1, 2019 #17

    CrashedAgain

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    I have melted cast iron with a home made propane burner........very simple with just a forced air fan and a propane jet, manually adjust the air/fuel mixture. Furnace was a metal pail lined with firebrick. Burner was big enough to completely surround the crucible with flame.
    It can be done, the important part is getting the air/fuel setting as close to correct as possible to obtain the maximum flame temperature. Too much or too little air reduces the flame temp. It is difficult to get the air/fuel setting with a venturi burner, the only way to adjust is to restrict the air flow then maybe the flame is too small.
    I was using a 3/32" propane orifice with about 2 psi propane which I think is about 130,000 BTU/hr....more than enough to provide the latent heat.
     
  18. May 2, 2019 #18

    jacobball2000

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    I used a number 60 drill bit on my burner and it seems to small. I don't get the constant wore but a pulsating sound. And what type of crucible are you using?
     
  19. May 2, 2019 #19

    CrashedAgain

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    I am using a purchased crucible, either #A6 or #A8 size. The furnace can be seen here: https://saskatoonmodelengineers.webs.com/ (another photo on the "photos" page. #60 drill bit is .040" dia, mine is twice that (3/32") so 4 times the flow area.
    What it your propane pressure? I used a big orifice so the pressure is low (2psi). It sucks propane so fast (7 lbs./hr) that I have difficulty maintaining the tank pressure. I get a constant roar and adjust the burner so there is flame right up to the exhaust hole in the lid.
    I also have a speed control (dimmer switch) on the fan but generally it is wide open.
    Actually it all depends on the size of the fan......if you have a small fan you are going to have a small burner.
     
  20. May 2, 2019 #20

    CrashedAgain

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    Actually, the furnace described above is my "old" furnace. I am now using a new one which looks pretty much like a trash can (Photo).
    It uses two burners from a BBQ. Much less output but better insulated using home made refractory (1 part clay, 4 parts perlite). It is much safer, less a thing of sound and fury, and can even be left unattended for short periods. It will melt bronze if you wait long enough but I doubt if it will melt iron.
    In theory, provided your flame temperature is high enough, you should be able to get the interior of the furnace up to melting temperature even with a small burner if the furnace is well insulated. It will just take longer.
     

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