cheap and very efficent furnace.

[kye]

hey guys

so im not sure weather anybody else out there has stumbled apon this little secret but i use a material called "hebal" (airated cement blocks) to construct my furnace. if your familiar with the stuff youll know its used to insulate houses etc but it works just a well at much higher temperatures. these are some of its positive attrubutes:
-its easily fabricated and can be cut with a hand saw.
-a Very effective insulator
-cheap
-has a relatively high alumina content (a very good refractory material)

at aluminium temperatures a furnace made of this will last for a good 50+ melts and probably the same for copper and its alloys, but at these temps it will start to cinter on the furnace surface creating cracks which will eventually ruin the furnace.

hope you find this interesting/ inspiring for people

kye

 

[ksor]

Hi Kye

Idon't know what " "hebal" (airated cement blocks) " is in danish, so a picture would be very nice - please.

I'm going to construct my own furnace, so I'm very interested in experiences others may have got.

 

[kye]

http://i1020.photobucket.com/albums/af324/mackye/DSC00109.jpg?t=1274945449

http://i1020.photobucket.com/albums/af324/mackye/DSC00110.jpg?t=1274945654

http://i1020.photobucket.com/albums/af324/mackye/DSC00111.jpg?t=1274945656

http://i1020.photobucket.com/albums/af324/mackye/DSC00117.jpg?t=1274945658

this is the first time ive ever tryed to put any photoes up on here so im not sure wheather this will work.

 

[ksor]

Oh, yeah ... now I think I know, what it is in danish (gas-beton) - thanks !

 

[shred]

I'll have to see if that's available around here. Looks perfect for the job. I can get the good lightweight firebricks from a pottery supply place, but they get expensive by the time you get enough to make a furnace.

Edit: the generic name seems to be Autoclaved Aerated Concrete (AAC) and the brand name is "Hebel" here. It's supposed to be a "Green" building material, so we should be awash in salesmen of such around here.

 

[kye]

this is a smaller one ive made, the furnace chamber itself was only 50mm in diameter and it happily melted cast iron and cupronickel. these temps really were pushing the capabilities of the furnace though as afterwards it was quite vitrified in places and large cracks had started to develop.

http://i1020.photobucket.com/albums/af324/mackye/DSC00185.jpg?t=1275028468

http://i1020.photobucket.com/albums/af324/mackye/DSC00186.jpg?t=1275029662

im planned on making my next one with a lining of some other refractory maybe 10-20mm thick just to take the brunt of the heat allowing the hebal to insulate without being destroyed.

here are a few things ive cast if anyone is interested

 

[njl]

Hi Kye just stumbled across your thread,

I like the design of your furnace, just wondering how you are you heating it? I see the hole in the middle block, is this for an electric element or do you poke a blow lamp into the hole or have I got it completely wrong?

Nick

 

[Omnimill]

Could these blocks be used for a brazing hearth?

Vic.

 

[Lykle]

Brazing hearth,
oh yes for sure.

I use them all the time for that.
Another nice aspect is, that they are soft. So it is easy to stick pins in them to hold small parts in position.
I think it is wonderfull stuff.

I also used it to build an extension to the bedroom and to build a walk in closet. So hey, I am sold.

 

[neubert1975]

Hi all
I think it´s called
CLC (Cellular Lightweight Concrete) Concentrate


Hope this helps.


Best

Martin

 

[va4ngo]

I had never considered this material for a furnace. I have sime of this in large panels (offcuts from a building site) my panels have wire reinforcement embedded in them. will give it a try as it seems much simpler than other home furnaces. Can someone give me guidelines as to how karge a hole is needed aat the top? say if i am using a 4" diameter crucible (I have a couple of small cast iron crucubles)

 

[neubert1975]

when i tried them, i just used a long drill, and made holes in a circle, and used a chisel to carve it out.

 

[Herbiev]

Kye great looking furnace. 100model posted a great video on how he constructed his furnace. To take the brunt of the heat he used Kaowool adhered to the shell with water-glass (Sodium silicate) and coated that with a refractory wash called zircoat-W. this keeps the weight down and as you can see in the video, produces first class clean iron castings. I love the Hebel block idea so please keep us posted.

 

[TorontoBuilder]

Hi all
I think it´s called
CLC (Cellular Lightweight Concrete) Concentrate


Hope this helps.


Best

Martin

Sorry Martin, you are incorrect... they are very different products.

Cellular Lightweight Concrete, Lightweight Aerated Concrete, and Foamed concrete are all the same thing, and they are not autoclaved concrete. They are not cured in the manner ACC is.

Also, they cellular matrix can be very different due to the way each product develops the matrices. That can dramatically affect the insulating properties... and the ability to withstand furnace temperatures. I'd be especially cautious using non-autoclaved lightweight concrete.

 

[va4ngo]

Tried cutting my hebel blocks which are reinforced with steel and these have proved to be too dufficult as the block cracks when cutting through reinforcement close to an edge. will not pursue with my material.
phil

 

[neubert1975]

oh sorry about that then.
As ksor wrote earlier, in Dk it´s calles gas beton, directly translated it would be something like "gas concrete"

Best
Martin