# High temperature alloy for ashing



## anachronism (Sep 15, 2016)

Learning to ash carbon has been a steep learning curve for me over recent months. In fact it's probably worthy of a thread all of its own however I thought I would share the process I went through in selecting the correct material for the trays used in the furnace.

Requirements:

Large surface area to allow large volume of carbon therefore increasing furnace efficiency and lowering cost of production runs.
Material has to remain structurally sound at 650 degrees Centigrade for long periods of time. 
Material has to be impervious to the effects of high temperature ramps both up and down.
Material has to have no negative effects as a result of contact with carbon at high temperatures. 
Material has to be resistant to oxidation within the temperature requirements.
Material has to be resistant to corrosion even at high temperatures.
Material has to be workable.

So firstly let's look at Stainless Steel. 

Sadly the main problem is that the carbon would leach the carbon from the steel at high temperatures turning it effectively into iron and cracking. So that's no good.

Secondly let's look at Titanium.

Titanium's oxidation zone starts at 550 degrees C so given the furnace is operating at 650 degrees C that's a no go.

So where do we go from here? Having spent a fair amount of time on the net I decided to phone a couple of alloy specialists. The unanimous verdict given all the requirements was a Nickel Chromium superalloy known as Inconel 601. 

http://www.hpalloy.com/Alloys/descriptions/INCONEL601.aspx

So here it is. All ready to be shaped with a hydraulic press into the right shapes. It was laser cut to the right dimensions to allow a 340mm x 340mm tray, of which there are 6. I'l post pictures of the completed trays and some pictures of ashing in progress during the weekend.


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## Topher_osAUrus (Sep 15, 2016)

I don't know how well it would work, but corningware pyroceram can easily withstand those temperature variances. Ive used it to pyrolize, incinerate, leach, and everything in between. So, if you're just ashing carbon, it may do the trick.


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## anachronism (Sep 15, 2016)

I've tried it Topher. 

The furnace needs to be able to ramp at max heating capability up to the 650 degrees Centigrade. That's under an hour.

The airflow required for the ashing reduces the ability to counteract temperature shock because the front of the furnace is colder than the back, especially on the up ramp. I shattered a number of these trying various temperature ramps. Couple this with the fact that you can't load the furnace with anywhere near as much carbon using them and it makes it a no go.


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## Topher_osAUrus (Sep 15, 2016)

You may have had a fake, or flawed dish.

The clearance issue was one i was thinking would be problematic more than anything.

Hope you get it figured out.


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## pontoy (Jul 26, 2018)

For your requirements the best choice is AISI 310 / S31000. For your application stainless steel is enought and it will be cheaper.


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## snoman701 (Jul 26, 2018)

There are a number of alloys that will work, but your inconel 600 series are the most available. 

You should look in to doing a small rotary calciner. Call lou. He's been down this road. 

Whatcha burnin?


Sent from my iPhone using Tapatalk


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## 4metals (Jul 26, 2018)

Maybe 25 years ago now I needed to make some rollers in an incinerator so I could roll out trays. Rollers allowed me to burn a top and bottom tray in the chamber and essentially double the capacity. They were double tube rollers, a pipe within a pipe with the inside pipe carrying intake air into the burner and the outer pipe just rolling around the inner pipe. The make up air feed was only to keep the pipe a bit cooler by changing air. 

The manufacturers attempt was with stainless and after a few short months the inner and outer pipes warped enough that the outer pipe couldn't roll. Inconel was the metal of choice to replace the stainless and we enjoyed years of service. It took the heat well and did not bend. Not saying I didn't bend having to pay for the stuff but it was worth the cost in my application.


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