Kaowool harmed by flame

Home enthusiasts discuss their Foundry & Casting work.

Moderator: Harold_V

HDB
Posts: 53
Joined: Mon Oct 28, 2013 1:06 pm
Location: Europe

Kaowool harmed by flame

Post by HDB » Mon Aug 01, 2016 11:58 am

As mentioned in the other post, I made myself a siphon nozzle type diesel burner, primarely to melt cast iron.

The problem js that the heat is so intense, that it sinters the insulation and burns it off. So after 2 heats, the hottest parts are gone. So I have to patch up my furnace every time with new pieces of kaowool here and there.

This is not only iritating but also expensive and time consuming.

Anyone else with similar experiences?

Harold_V
Posts: 17624
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Kaowool harmed by flame

Post by Harold_V » Mon Aug 01, 2016 3:19 pm

I question the use of Kaowool in this instance. In order for you to be able to melt iron, you're forced to use a refractory that can deal with the required heat. There's no shortage of them on the market--and you have options of using one that can be poured, or one that can be rammed. It may not be cheap, but in the long haul, it's the wise choice to make. I tend to think you're asking more from Kaowool than it is intended to provide. Could be wrong, though.

Melting iron with a crucible furnace offers its own challenges. I'd be interested in reading more about your experiences if you're interested in disclosing more.
Wise people talk because they have something to say. Fools talk because they have to say something.

User avatar
steamin10
Posts: 6712
Joined: Sun Jun 08, 2003 11:52 pm
Location: NW Indiana. Close to Lake Michigan S. tip

Re: Kaowool harmed by flame

Post by steamin10 » Tue Aug 02, 2016 8:50 am

Rock wool is light weight and suitable for hung insulation up to red heats. Lining an old fridge cabinet can give you a paint oven, or burnout cabinet for de-waxing. Using it as a fire wall or gun target as in a furnace for melting will give you fits, as you are finding out. The furnaces I built I used hard refractory brick with fireclay and sand mortor. It has held up for many heats with only an occasional patch on the bottom where metal sticks to rubble, and it must be leveled for the block the crucible stands on. The lids are cast or cut brick too.

Melting iron in a crucible is hard on the furnace, and your vessels will burn away quite fast. If you are going to do a lot of iron, consider a refiners furnaceof 6 inch bore, and run on coke and charcoal. You can get good artificial gray iron, and bronzes too. There is more on the net about building one out of a water heater for a shell, and laying out the tweres and hearth, that can be run on a shop vac for blast.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.

HDB
Posts: 53
Joined: Mon Oct 28, 2013 1:06 pm
Location: Europe

Re: Kaowool harmed by flame

Post by HDB » Wed Aug 03, 2016 4:15 am

Harold_V wrote:I question the use of Kaowool in this instance. In order for you to be able to melt iron, you're forced to use a refractory that can deal with the required heat. There's no shortage of them on the market--and you have options of using one that can be poured, or one that can be rammed. It may not be cheap, but in the long haul, it's the wise choice to make. I tend to think you're asking more from Kaowool than it is intended to provide. Could be wrong, though.

Melting iron with a crucible furnace offers its own challenges. I'd be interested in reading more about your experiences if you're interested in disclosing more.
The type of kaowool i use ia sold in 2 versions: 1350 and 1400degrees Celcius. Given that cast iron melts below 1400 and its hard to reach these temperatures and thought kaowool would be more than up for the task.

And I think it really is. The thing is that the momentum of the flame hammers onto the fibers and kind of blow them away. The reason why I think this is because I only have this phenomenon on the bottom part of the vertical wall. Although the top part may be even hotter. So I need some sort of coating, that's what I'm thinking now....

HDB
Posts: 53
Joined: Mon Oct 28, 2013 1:06 pm
Location: Europe

Re: Kaowool harmed by flame

Post by HDB » Wed Aug 03, 2016 4:22 am

steamin10 wrote:Rock wool is light weight and suitable for hung insulation up to red heats. Lining an old fridge cabinet can give you a paint oven, or burnout cabinet for de-waxing. Using it as a fire wall or gun target as in a furnace for melting will give you fits, as you are finding out. The furnaces I built I used hard refractory brick with fireclay and sand mortor. It has held up for many heats with only an occasional patch on the bottom where metal sticks to rubble, and it must be leveled for the block the crucible stands on. The lids are cast or cut brick too.

Melting iron in a crucible is hard on the furnace, and your vessels will burn away quite fast. If you are going to do a lot of iron, consider a refiners furnaceof 6 inch bore, and run on coke and charcoal. You can get good artificial gray iron, and bronzes too. There is more on the net about building one out of a water heater for a shell, and laying out the tweres and hearth, that can be run on a shop vac for blast.

Google Kaowool. It's an aluminum oxide wool that stands up too iron melting temperatures. As metio ed on my reply above, i think I need a thin protevtive layer to keep the fibers in place.

I may be wrong, but I'm gonna try thus first.

I"ve experimented with all kinds of refractories in the past, and I like the fact that kaowool is a phenomenal thermal insulator (I melt 2kg of in 25minutes easily) and it's lightweight.

I want a furnace that is lightweight so I can put.it in my car and bring it to fellow casting enthousiasts i know, yet very tough.

I'll have to experiment some more.

choprboy
Posts: 226
Joined: Sat Oct 29, 2011 11:23 pm

Re: Kaowool harmed by flame

Post by choprboy » Wed Aug 03, 2016 1:24 pm

HDB wrote:Google Kaowool. It's an aluminum oxide wool that stands up too iron melting temperatures. As metio ed on my reply above, i think I need a thin protevtive layer to keep the fibers in place.

I may be wrong, but I'm gonna try thus first.

Yeah, your wrong, at least in the way that you are trying to use it. Kaowool melting temperature is 3200F, maximum use temperature is:
Kaowool/Kaowool RT** - 2000F continuous, 2300F intermittent
Cerablanket - 2150F continuous, 2400F intermittent
Cerachem/CeraChrome - 2500F continuous, 2600F intermittent

** - there are many different grades of Kaowool with different properties (1100/1260/1400/B/RT/S/SZr/etc.) and you don't say which you are using.

Melting points:
Cast Iron - 2100-2200F
Iron - 2800F
Steel - 2500-2700F

In the furnace you are going to be at least several hundred degrees hotter than the minimum melting point of the material you are melting, so figure 3000F+ for running iron mixes. Your Kaowool is rated to 2300F. You can try applying a ceramic wash to the surface of the Kaowool, but Kaowool is not really designed for direct-fire high temp applications, it is a high-R insulation backfill.

User avatar
steamin10
Posts: 6712
Joined: Sun Jun 08, 2003 11:52 pm
Location: NW Indiana. Close to Lake Michigan S. tip

Re: Kaowool harmed by flame

Post by steamin10 » Wed Aug 03, 2016 1:29 pm

Agreed that the KAO wool is a good product, but as you have mentioned is melting or blowing apart, says you have exceeded its limits in the flame path. This is a common problems usually confined to one area. Understood, you want something light, and reasonably portable. my furni are on wheels, and because of their trash can size are mostly portable, for a portable truck or trailer.

I would suggest if you have a hot spot that a target wall of better material be installed to buffer the hot zone. A thin coat of harder material as a face for rock wool product, has proven too fragile for my use, and simply rolling a furnace out for use causes separations and collapses of the coating. The one lid constructed with rock wool, is supported with a piece of doubled highway grid, and the salvage strips of wool laced on top. It is very effective at keeping the heat in that furnace. I encourage you to experiment with your chosen materials, keep an open mind as to what happens, and how to solve your problems. You may learn things along the way useful in other terms of what you do.

In the end, there is no"right' answer that is the tell all. You will find many ideas, for this mini casting mill you want, and that will be your zenith. I can only relay what I have done by comparison, and exposed some of my trials and failures, to help guide your progress. Keep at it, and make it work. I am interested in your trail.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.

HDB
Posts: 53
Joined: Mon Oct 28, 2013 1:06 pm
Location: Europe

Re: Kaowool harmed by flame

Post by HDB » Thu Aug 04, 2016 10:01 am

choprboy wrote: Yeah, your wrong, at least in the way that you are trying to use it. Kaowool melting temperature is 3200F, maximum use temperature is:
Kaowool/Kaowool RT** - 2000F continuous, 2300F intermittent
Cerablanket - 2150F continuous, 2400F intermittent
Cerachem/CeraChrome - 2500F continuous, 2600F intermittent

** - there are many different grades of Kaowool with different properties (1100/1260/1400/B/RT/S/SZr/etc.) and you don't say which you are using.

Melting points:
Cast Iron - 2100-2200F
Iron - 2800F
Steel - 2500-2700F

In the furnace you are going to be at least several hundred degrees hotter than the minimum melting point of the material you are melting, so figure 3000F+ for running iron mixes. Your Kaowool is rated to 2300F. You can try applying a ceramic wash to the surface of the Kaowool, but Kaowool is not really designed for direct-fire high temp applications, it is a high-R insulation backfill.
I use the brandname Kaowool as a synonym for high temperature insulation blanket. I bought mine at a local ceramic store and it's rated up to 1400°C (continuous use?). It's probably another brand. I've been using this stuff for the last say 6 years. I did have problems with it in the past while forge welding (due to the borax eating it), but never this type of destruction (due to blasting the fibers away). But I never used a forced air blower before (always venturi based), and the heat is easily 100-200°C higher than forge welding temperatures.

I either have to lower my temperature a bit (I think it's a bit to much anyway) by letting my blower blow less :-), or add a ceramic coating to the wool. I'll probably do both. The fact that my steel center pipe (the hole in my lid) melts (drips apart) tells me that I'm running easily 100°C to hot. Also my 'kanthal' K-type thermocouple went to thermocouple heaven, so I must have been in the 1500°C zone, almost 250°C to hot..

Not that my cast iron was that hot because I poured it once that it had the fluidity of water.

User avatar
Comstock-Friend
Posts: 130
Joined: Fri Apr 23, 2010 9:05 am
Location: Sun Valley, California

Re: Kaowool harmed by flame

Post by Comstock-Friend » Fri Aug 12, 2016 5:24 pm

Built quite a few petro-chemical furnaces with Kaowool (back when it came from Babcock-Wilcox). The furnace usually had a 2400 deg F rating. These were electrically 'fired' so just used as blankets impaled on Inconel studs (the studs had ceramic spools that held the Nichrome 70/30 furnace ribbon elements). The Kaowool would be backed by mineral fiber (better insulator and cheaper than Kaowool) typically 3 inches of Kaowool, 5 inches on mineral fiber next to the steel furnace body.

If we were firing with gas or oil, we would have the 1" thick outer layer rigidized (it would come wet in poly bags and dry up after you formed it into the furnace liner). Would last 2 plus years in 24/7 chemical plant operation.

John

HDB
Posts: 53
Joined: Mon Oct 28, 2013 1:06 pm
Location: Europe

Re: Kaowool harmed by flame

Post by HDB » Sat Aug 13, 2016 3:16 am

Comstock-Friend wrote:
If we were firing with gas or oil, we would have the 1" thick outer layer rigidized (it would come wet in poly bags and dry up after you formed it into the furnace liner). Would last 2 plus years in 24/7 chemical plant operation.

John
Interesting!
What 'liquid' was used to soak the kaowool into?

User avatar
steamin10
Posts: 6712
Joined: Sun Jun 08, 2003 11:52 pm
Location: NW Indiana. Close to Lake Michigan S. tip

Re: Kaowool harmed by flame

Post by steamin10 » Sat Aug 13, 2016 4:21 pm

Would that be sodium silicate,(water glass) that hardens chemicallly with carbon dioxide.. I suppose it would be diluted somewhat to get it to 'wet' the fibrous wool. Perhaps painted on, but is the major component in most furnace cements that I know of.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.

User avatar
Comstock-Friend
Posts: 130
Joined: Fri Apr 23, 2010 9:05 am
Location: Sun Valley, California

Re: Kaowool harmed by flame

Post by Comstock-Friend » Wed Aug 17, 2016 6:14 pm

HDB wrote:Interesting!
What 'liquid' was used to soak the kaowool into?
We bought it already prepared. I would assume that similar product is available today, but I've been out of that industry for 30+ years.

(I have an old box of samples, maybe I can find the product name.)

John

Post Reply