Muffle furnace

[FulmenParticipant @fulmen]

@SOD: Yes, the carbon is dissolved in the steel. But how does the carbon get into the steel? Carbon isn’t volatile so simply being in contact won’t do much. This is where the CO comes into play. It acts as a carrier that can diffuse into the steel and deposit carbon.

And there will be oxygen/CO2 available. First of all there will be air left in the case, and coal and charcoal does contain some chemically bound oxygen. But they will also add carbonates to the case as a source of CO2.

[noel shelley]

On noel shelley Said:

Hey Sonic, The thermocouple you need is an Inconel sheathed K type, 3mm dia will be good and of whatever length you think best. They are rated for the temps you want, I use them in dip pyrometers at 1150c or more. Good Luck. Noel.

Yes, that is exactly the type I was considering. And maybe a grounded version to have faster response.

Meanwhile I ordered this USB thermocouple interface. I liked their API documentation. There are even VB.NET examples. This is great since this is my favorite programming language for Windows. I didn’t used it since 2000’s and it changed a lot. But Copilot, Microsoft’s AI, is very helpful. I even put it to write the PID algorithm 🙂

To control the solid state relay I’ll use the RTS pin from the serial port. Is easy to access it from code and no extra HW is required.

Now I’m abusing the AI to write the code for a nice graphic way to program the ramps and temperature points.

 

 

[Howard LewisParticipant @howardlewis46836]

In Carburising the iron or low carbon steel is packed into a box, sealed and heated at high temperature for a time. The longer the time, the deeper the carbon penetrates into the iron, increasing the carbon content.

The carbon atoms are mixed with the iron atoms. Cast iron, on the other hand has carbon particles amidst the ferrite particles. (Which is why it is easy, but filthy to machine)

Other additives such as Cobalt, Vanadium or Nickel are added to the steel when it is in an open hearth furnace, (Which will have a reducing atmoshere) and samples can be taken to ensure the desired composition is produced.

Howard

[Sonic EscapeParticipant @sonicescape38234]

It looks like three materials are suitable for the furnace. Bellow I gathered their most relevant properties. The numbers might vary depending on specific product. There is no significant difference between them. Except that the vermiculite is heavier. Also there is no significant difference in cost or availability. Hard to decide. Vermiculite is available in a hardware store close to me and I’m going tomorrow to see it.

I incline more towards vermiculite since it has less health hazards. I think the other two create an irritating dust when machined. Also since it is heavier maybe vermiculite is also harder. Also I found a glue for it that works up to 1300°C

 

[jaCK HobsonParticipant @jackhobson50760]

You can make your own insulating refractory with bentonite cat litter, vermiculite, and a little cement.

[Nigel Graham 2Participant @nigelgraham2]

Would the “little cement” be better as lime, or lime-rich, mortar rather than purely Portland cement? I have a vague idea of reading this in connection with domestic chimneys.

[Sonic EscapeParticipant @sonicescape38234]

There are available bags of refractory cement already made. You need only to pour water. And it can be used up to 1300°C. But they have much lover thermal conductivity, in the range of 1W/m*K. I guess this is normal since the density is also much higher at around 2000 kg/ m3.

[FulmenParticipant @fulmen]

My plan is to cast an outer shell of refractory cement filled with either leca, vermiculite or perlite (some testing needed there I guess) and face it with straight refractory.

[BazyleParticipant @bazyle]

The cement needs to be that sold in tubs as ‘fire cement’ not regular builders stuff.

There used to be a firm advertising in ME for hobby level oven supplies. Think the name began with W. Might go look this evening if nobody else comes up with the answer.

There is a staggeringly expensive ceramic paint I think based on Zirconia that reflects heat and is apparently worth the expense for hight temperature work.

[noel shelleyParticipant @noelshelley55608]

Gentlemen ! In the context of high temperature,ie 1150/1200c, been there ! There are 2 types that will work well and not cost the earth, 1 is ceramic fibre and 2 is K23 fire brick. The latter is very easy to work with or form. Intended for pottery kilns Etc it comes in numerous shapes and sizes and can be glued into position with air setting cement. How well does it work = I would run up the furnace to white heat for 20mins and be able to pick it up put it in the back of the car afterwards, the wall is a single brick thick, was made 30 years ago and still has the paint on the outside. The whole furnace weighed about 17Kg. When thinking about the cost of building DO NOT forget the cost of running, a cheaper lining will cost more fuel ! The traditional fire cement lined furnace would use 4 times as much gas as the K23lining did. I costed the bricks a few years ago at about £3 each and 20 would make a furnace to take an A6 crucible. In passing, the body was the casing of a Creda spin drier !

Ceramic fiber is good but needs to be treated carefully, it is fragile even if rigidizer is used.

For electric elements one can use old stock electric fire elements if you can find them to make a small heat treatment oven and for Fulmen and ally it will work but it is important to heat the metal as fast as possible so gas is better.

For smelting to prove the point I set 8 bricks on end in a circle (bit like stonehenge) and used a sievert 2943 (I think) burner in at a tangent and melted the brass to do a casting – you don’t need a furnace per se !

I’ll help if I can, Good Luck. Noel.

[ChrisLHParticipant @chrislh]

Alec Tiranti of Newbury / Thatcham ? Like you said begins with a “W” !

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