Hardening oven saga

[ddickey]

It does but the amount that I need to coil not sure if it would fit in my size oven. What was the dimension of your lower brick?

 

[Ray C]

It does but the amount that I need to coil not sure if it would fit in my size oven. What was the dimension of your lower brick?

1.5" thick (with insulation underneath it). 2 squares of 12" x 12".

Ray

 

[Ferrous Turner]

I used that type insulation when I was in the heating business. It works well, but you don't want to breath the dust from it. Use a mask when working with it, and enclose it in something. Maybe some thin sheet alum. I've been enjoying your journey, and I believe in the end your persistence will carry the day. Cheers, Mike

Thanks Mike, it's been a real learning project for me. I've been looking around for an old appliance, like a big microwave oven, that I can gut and use the shell for an enclosure around the insulation. I should be able to find something on Craig's list that someone is trying to get rid of.
And thanks for the heads up on a respirator (and gloves)!

Ted

 

[Ferrous Turner]

I made my kiln with that kind of insulation. It's great stuff! As Mike says, use a respirator and I will add, be careful handling it. It has shards of glass glass in it. I got a sliver of glass in my thumb that took 3 months to finally work itself out.

Ray

Yeah, if I had to to it again, I would use nothing but the ceramic fiber material. It insulates better, much easier to machine and quite a bit lighter! How much power do you run in your kiln?

 

[brino]

I've been looking around for an old appliance, like a big microwave oven, that I can gut and use the shell for an enclosure around the insulation.

....and be sure to keep the transformer so you can re-wind it for a spot welder.....
https://www.hobby-machinist.com/threads/show-us-your-welders.16877/post-388854
https://www.hobby-machinist.com/threads/show-us-your-welders.16877/post-414922
https://www.hobby-machinist.com/threads/show-us-your-welders.16877/post-415193

https://www.hobby-machinist.com/threads/q-regarding-homemade-spot-welder.37660/post-321885

-brino

 

[brino]

deleted double post.....

 

[Ray C]

Yeah, if I had to to it again, I would use nothing but the ceramic fiber material. It insulates better, much easier to machine and quite a bit lighter! How much power do you run in your kiln?

Here's a link to the original build: https://www.hobby-machinist.com/threads/heat-treat-oven.9929/

Power is 20A at 230V = 4.6kW

Ray

 

[pdentrem]

The Fibrfrax insulation will hold the heat in that the masonry bricks is transferring to the exterior. Due to the density of the masonry material in those bricks, the whole brick comes up to nearly the same temperature as the interior and you are loosing lots of heat. The Fibrfrax is low density and it will not transfer as much heat to the outside. We use this stuff on many pieces of heat treatment equipment. For example on our continuous casting machine the top made of 3/8” steel has 4 layers of the Fibrfrax between it and the 2300 F interior. It is not stone cold but under 200 F! This stuff is fantastic. When you cut it use a particle mask to protect your lungs as it is the same as glass insulation in it effects. I use either large scissors or a sharp box cutter with the blade extended a fair bit. I roll it out on to the floor or a table to cut. Try not to crush it too much as this reduces its effectiveness. Cover with some tin/aluminum sheets when finished. In the end you will use a lot less time to get to temperature and reduce the power bill.

 

[Ferrous Turner]

I read your thread Ray, and I must say I wish I had done as thorough a job researching this project as you did. You made a really nice oven!
I tend to have a lot of enthusiasm and little patience, which has worked to my detriment more than once. This isn't the first project I've gotten halfway through and realized a major design element was overlooked.
Nevertheless, more power and more insulation might be able to save this oven from the dumpster. I am going to rewire it for 230 VAC and wind a new element. I have plenty of room in my electrical box for a new 30 amp breaker, and it's right in the shop.
I'm thinking I might line the inside of the oven with some fiber board, both to hold the element and to give a little more impedance to ever escaping heat. Do you guys think it's worth the trouble?
I've got some aluminum sheet metal, but not enough to cover the whole thing. Cement board?
Thanks for all the input!

Ted

 

[Ray C]

I read your thread Ray, and I must say I wish I had done as thorough a job researching this project as you did. You made a really nice oven!
I tend to have a lot of enthusiasm and little patience, which has worked to my detriment more than once. This isn't the first project I've gotten halfway through and realized a major design element was overlooked.
Nevertheless, more power and more insulation might be able to save this oven from the dumpster. I am going to rewire it for 230 VAC and wind a new element. I have plenty of room in my electrical box for a new 30 amp breaker, and it's right in the shop.
I'm thinking I might line the inside of the oven with some fiber board, both to hold the element and to give a little more impedance to ever escaping heat. Do you guys think it's worth the trouble?
I've got some aluminum sheet metal, but not enough to cover the whole thing. Cement board?
Thanks for all the input!

Ted

Personally, I hate the cement board but, it works. It's starting to crumble and will need to be replaced. That will be minimal effort and expense.

The oven works well and is used frequently. Along the way, the pyrometer went bad and needed to be replaced. No big deal.

I wrapped the whole oven frame in one more layer of that insulation (3 layers total), stuffed it in that cement board enclosure and it does not get terribly warm on the outside walls. Of course, if you touch the metal door frame, you'll get a 2nd degree burn -this is to be expected. Most everything I do needs temps of 1525 and it takes about 50 minutes to hit that temperature. Once I accidentally set it to 1650 and it hit that with no problem. The coils have been replaced twice and it was due to using carburizing compounds. The fumes weaken the wire. Now, I use argon purge and the coil has lasted a couple years now. They are cheap to replace.

I would some day like to make a smaller one. I hate the cement board and the way it feels but, like I said, it works... It eventually crumbles due to the heat but, mine has been holding up all these years well-enough to be functional.

For your setup... I'd cut the legs off, wrap a layer of the insulation around the whole thing, build an enclosure around that, set it on some bricks, and call it a day.

Ray

EDITED: To fix a broken sentence and clarify a statement about layers of insulation.