Refractory questions

[Rainbows]

So heres the  furnace I plan to build

 

Steel body, ceramic wool insulation (50mm of) and surrounding the interior 1600C dense castable refractory (I don't think the £3 upgrade to 1700C is necesarry?).

For scale the pipe at the top is 2" and the interior will be 100x230x550mm.

 

 

These are the parts that need to be made of refractory. 

Having two flanges on the middle one seems difficult though.

If I split the middle one into two parts to be cast does anyone know if there is a way to join the two pieces together? Also the refractory is 12mm (~0.5") thick, is this a suitable thickness or should I increase it to 25mm? 

[Mikey98118]

Pop rivets or sheet metal screws.

I don't think you have a very clear idea of how to build a forge, or a clue about refractory. You can download a pirated copy of Gas Burners for Forges, Furnaces, & Kilns for free. Get a copy and learn the basics.

People mainly build a box shaped forge for a sound structural reason, which you don't seem to have. You are planing to use a castable refractory; not bricks, kiln shelves, or one of the various ceramic boards. On the other hand there are vary sound reasons not to go for a box shape. 

[ThomasPowers]

Monolithic refractory pours in convoluted shapes will generally not weather the expansion/contraction of use well.   I suggest further research and redesign.

[Frosty]

Wow, that's more elaborate than my first double lined forge, not counting the ribbon burner.

Have you used a gas forge for any length of time? Your design is pretty common for someone who doesn't know much about them.

You've designed in a couple serious flaws: First is serviceability, how are you going to change the liner? It doesn't make a lot of difference what you wash the ceramic blanket with it will erode: thermally, Mechanically and chemically. It's going to end up like one of my early attempts taking up room on the shop floor because it's WAY easier to build one than reline that one.

Another little problem is all the sharp corners each one is a weak point we'd call a "cold shut" were we talking about forges steel. Thermal cycling causes everything to expand and contract the forces generated in a HARD refractory conduct like a shock wave in a tuning fork. When the pressure encounters an obstruction like a sharp corner it concentrates. Your liner will break at the corners.

The shape is also not conducive to smooth vortices so the internal temp isn't going to be as even as a ribbon burner says you want.

A "Vault" shape is much more conducive to resisting all the above problems. It's easy to make, is virtually all smooth curve which also promotes even circulation of the flame and heat.

Frosty The Lucky.

[Rainbows]

I had to google the ribbon burner, I see the resmebelance. The burner is actually based off the urutsz burner and is designed to burn oil (vegetable,motor, diesel or other). However the use of refractory in gas and oil forges seems similar and since the oil section is pretty dead looking I thought I would ask in the much more active gas section.

The oil burns in the chamber above the refractory grill and the flame is pushed down into the forge. I was going to use tapered steel pins to create the holes in the refractory but after getting a PDF written by Emmerling I much prefer his wax crayon idea, much easier. Since combustion occurs in the burner instead of in the forge body there needs to be refractory in the burner too. 

Since oil burns hotter than propane I don't think coated ceramic wool would last.  Gas Burners for Forges, Furnaces, & Kilns  was still an interesting read though. 

Would something like this be better? Roof and walls one piece, floor and ends seperate pieces. More room to breathe. Just unsure how well the wool surrounding would keep it located. Pretend the sharp corners on the end piece have slight radiuses on them.

 

Edit: And yeah my expierence of gas forges is pretty non existant. 

[Frosty]

I'm not a fan of oil fired forges for reasons I won't go into again. I'll leave you to your fuel of choice.

yes, that's a much better shape but you can skip the vertical walls and make it a half cylinder. It's easier to make and stronger.

How thick are you thinking of casting the inner liner, contact layer? Much over 1" is approaching the point of diminishing returns as it becomes enough of a heat sink you start burning too much fuel to heat the liner. If you're getting your furnace hot enough to damage 2,600f refractory blanket through 1/2-3/4" of 3,000f high alumina refractory with a zirconia content you're going to be melting whatever you put in it anyway.

You'll HAVE to turn it down or just burn your furnace up.

Frosty The Lucky.

[Rainbows]

The wool from my planned supplier is rated for 1300C (2372f). The refractory is 1700C or 1600C (3092 or 2912F) but doesn't mention Zirconia.

1" appears to be the standard that people using oil burners for foundry furnaces seem to use. Might just follow their footsteps.   

 

Also the original design was based off pictures of a Devil Forge forge.

Thats why I thought a square box would be a good idea.

 

[Frosty]

Have you read any of the reviews of the Devil Forge forges on Iforge? Have you watched their videos? I can only base my evaluation on watching their videos and my experience building gas forges and burners. IMNSHO  Devil Forge products are grossly inefficient. In THEIR advertisement videos their forges never get to welding temps regardless of their claims. Being wide open at both ends they only get to a decent forging temp directly under the burners, not even close to positive welding temps. Their burners are also mediocre linear burners rather than the much more efficient jet ejectors. I don't know what the Devil Forge appliances really are for but they're certainly not forges. There are guys out there selling . . ."things" who don't know the difference between a forge and a pizza oven.

This is piddle poor performance.

Do some reading in the Iforge gas forge section then pick a better design to copy. Pick one of the MANY sets of plans posted here and follow just one, mixing and matching is a disaster unless you know just what you're doing. Even then, ask me how I know.

For a zirconia kiln wash you can order the high dollar ITC-100 or shop pottery and kiln suppliers for "Zirconium Silicate" Flour the finer the better.

Walk with us lad, listen and we'll pass on the secrets of the craft. (like we can keep a secret !!)

Frosty The Lucky.

[Rainbows]

No idea where to get ITC 100 in the UK. However zirconium silicate was much easier to find. 

Also recently discovered my local builders merchant does firebrick, however they only do the dense kind, no insulating brick. Would reduce cost of shipping compared to posting castable refractory but not seen any existing furnaces use it. 

[ThomasPowers]

The basic problem with the dense "hard" firebrick is that they make for VERY inefficient forges so the "I saved $50 in building it and will spend $200 more to use it for a net savings of....") comes into play.  Industrial systems may use the hard firebrick as they may need the longevity over the efficiency under hard usage.  They may also leave their systems HOT and so needing the forge to run for a couple of hours to come up to full temperature is not a factor either.

[Frosty]

You local builder doesn't build furnaces that reach steel melting temperatures either. ITC products are shipped world wide but read up about them and the alternatives before you buy something.

You WILL no fooling burn probably 5x the propane and still not get a hard brick forge to positive welding temps.

Frosty The Lucky.

[timgunn1962]

Hard fire brick is a lousy insulator. It has its place, but I don't think it's very likely to be appropriate for you.

That said, you don't actually seem to have told us what you are intending to do in the forge and it makes a big difference to the appropriate design and materials selection.

On 01/06/2016 at 11:10 PM, Rainbows said:

The burner is actually based off the urutsz burner

I've tried googling Urutsz burner without success. Do you have a link to any online information, or maybe a book to look for? It sounds interesting. 

"Based off" and similar phrases are always rather worrying when discussing burners, given the number of folk that seem able to louse up even relatively simple Propane burners by not following well-documented plans accurately.

Where in North West England are you, and do you drive?  An advantage of living on a little island is that, if it can be got here, it's not likely to be very far away.

ANH Refractories have a place on the Wirral, for example. They don't sell direct, but IMS do. They are on the same site and are an ANH distributor.

 

[Rainbows]

Why does it keep eating my replies aaahhhh

Edit:

Woops I can't blame you for not being able to find it, managed to misspel it. 

Ursutz rather than Urutsz

Here are some examples

http://www.abymc.com/Articles/Gallery/Peter_OddDuck.html

http://www.backyardmetalcasting.com/oilburners02.html

http://www.instructables.com/id/Waste-Oil-Furnace-For-Melting-Metal/

http://www.oupower.com/index.php?dir=_My_Projects/_Shop_Projects/WVO%20Ursutz%20Burner

Now this guy managed to get himself banned off here a while ago. He also got banned from a hobby casting forum I occasionally look. Not the brightest cookie but his burners sure were something. 

[originally I linked a video by the youtube channel "oil burner" here, wouldn't let me submit the post while it had a video embedded though]

 

Essentially you get a hot box, pour oil in it to vaporize it then add some air. 

 

Also this forum has a lot of missing images. Getting to be a pain trying to visualize what peoples past plans have been. 

[Frosty]

I looked at the links and I don't think those guys actually  know what they're doing building furnaces. Only one guy talks about getting ambitious and buying "Real" refractory for a later build. Anything with Portland cement in more and say 2% will spall when it gets to forging temps. Buy real refractory, castable or rammable but get high alumina rated to a higher temp than you're going to need.

Are you REALLY going to use one of those little incendiary devices for a burner? Do it well away from anything that can catch fire. 

Frosty The Lucky.

[Rainbows]

In their defense if you only plan to melt aluminium in one off melts that home made refractory holds up fairly welll. I once melted iron in a coal forge and the steel crucible wasn't even glowing by the time the aluminium was melted.

 The backyardmetalcasting guy used the oil burner later to try and melt iron, which he did but his final comment was to get proper refractory.

 

Final design will get a steel stand and be used outside so shouldn't have any problems with fire. 

[Charles R. Stevens]

Did you meen "melted aluminum in a coal forge" heck I have burned up more than my share in a coal forge, lol

[Rainbows]

Woops :x 

[Frosty]

Just because a thing CAN be done doesn't mean it should. I used to melt aluminum in tin cans and campfires. Ever make a cope and drag from ham cans? The really tricky part is getting the sand tempered well enough to hold it's shape.

I certainly wouldn't bother with a gas burner for aluminum casting charcoal briquettes works a treat and is more controllable, you can actually put your head over the top to look into the crucible.

While you CAN make your own refractory liner it's more trouble than it's worth and the quality is too variable dependent on your experience. Expect to have several fail before you get one to stay together through firing the liner. A 50lb. bag of insulating high alumina refractory runs between $120-$150 here where shipping often doubles prices.

Your game, your choice of course.

Frosty The Lucky.