Thread: Heat Treatment Furnace Construction

Looks good. You are certainly gunna need more than a few solar panels to keep the juice up to this baby.

Hi Stuart,

I have a Non contact IR thermometer with adjustable emissivity, but a bit of masking tape on the spot works too. I figure that touching anything with on a furnace at 1000C is not a good idea, not without a temperature check.

The ends of the elements are doubled back on themselves and twisted, from where it exits the inside of the furnace. I had a clamp meter watching the amps on each circuit and I didn't see much of a drop in current as the elements heated up, but I'm new to kanthal elements, maybe they don't increase in resistance as much with temperature as nichrome?

Don't know why the circuit breaker tripped, it's a C curve 20A breaker only drawing 10A, the other element was on a seperate circuit. I'll wait to investigate further when we finish the insulation.

Hi Paul,

The roof pins are 310 stainless, but the other stainless parts, the support frames and outer sheeting are 304. I must look up 346, and see what it is.

Regards
Ray

Originally Posted by Stustoys

You must have some big plane blades in mind.
Stuart

Here's a short list, of the sort of things that I think the furnace will be useful for.

1. Heat treatment of M2 D2 and other tool steels (obviously the main motivation)
2. Tempering.
3. Annealing
4. Stress relieving
5. Normalizing (I hope I have the right term here), not quite like Stress relieving, more like when you soak cast iron at high temperature to convert to SG.

6. Furnace Brazing (I want to learn more about how to braze those brass,steel laminated mag transfer blocks.)

7. Someone else, wants me to do some enamelling, basically melting glass onto a copper substrate.

So it's not all about plane blades...

Regards
Ray

I hope a licensed person did the electrical work on it..

Ray are you going to control it with a PID?

Hi .RC, Of course... wouldn't have it any other way...

Hi PeteF,

The control system is one of these... Temperature Controller PID Kiln Ramp Soak 64-Setpoints | eBay

The main reason for choosing that particular one is that it has a modbus interface, so I can interface it to an embedded linux box with mysql database and wifi web access. The profile is loaded onto the controller and it can then just run stand alone if needed, but I'm logging the actual temperatures versus the programmed profile and I can view current status on any device with web browser, laptop, iphone, etc. Sounds complicated but it's pretty simple, and shares a lot of the code that I've written for other web based control applications.

You could use the controller without the additional user interface, but then you'd have to go through programming all of the multiple setpoints and times, with this interface I can just select a pre-programmed profile and download it.

Regards
Ray

Cripes, that's going to be a sophisticated set up! Nice. Yes that's a bit more sophisticated than the PIDs I've used, yet the price is good, particularly considering it comes with a thermocouple. I am hunting for furnace myself and will convert it to PID control when I get it. I have a spare controller here but if I didn't would probably also use the one you linked to as it looks to be extremely versatile.

Pete

Originally Posted by Pete F

yet the price is good, particularly considering it comes with a thermocouple.

Pete

Not really, that supplied thermocouple is not suited to kiln operation, you need heavier gauge and ceramic spacers. I'm using this one...Type K Thermocouple Ceramic Kiln probe 8G Temperatuture | eBay

Regards
Ray

Originally Posted by RayG

By extrapolating from the heating curve so far, I expect we should get to 1200 C within 4 hours.

plus the time it takes to get product upto to temp

why did breaker trip....bit on the small side would be my guess

Originally Posted by RayG

Hi Stuart,

Hi Paul,

The roof pins are 310 stainless, but the other stainless parts, the support frames and outer sheeting are 304. I must look up 346, and see what it is.

Regards
Ray

Ray

Don't worry about the 346. It is 347!

I was close though.

Regards
Paul

Originally Posted by eskimo

plus the time it takes to get product upto to temp

why did breaker trip....bit on the small side would be my guess

Hi Eskimo,

It might have something to do with the 2.4Kw fan heater that was on the same circuit...

We got the rest of the insulation today, so the next test will be in a day or so.

Hi Paul,

Thanks for the PM, I've sent reply, While talking about stainless, did you see the new 410 Stainless plane by Ron Brese Brese Plane


Regards
Ray

Originally Posted by Stustoys

Ray,
Its coming along great but isnt bar going to add a lot of thermal mass?

Been flipping through the book you have(has yours turnen up yet BT?), I assume you have seen the part about case hardening powders not mixing well with furnaces and S/S foil? I'd never seen that before.

Stuart

The book arrived yesterday. I have only read the introduction. I do like the author's style!
BT

Originally Posted by RayG

Hi Paul,

Thanks for the PM, I've sent reply, While talking about stainless, did you see the new 410 Stainless plane by Ron Brese Brese Plane


Regards
Ray

Ray

My mouth went dry. I wondered what was happening. Then I realised I had run out of drool.

Regards
Paul

Hi All,

The insulation is finished, but not the front door as yet, and with a temporary controller installed.

The picture tells the story. red is current temp, green is setpoint.



Looking through a hole in the bricks that blocked up where the door is going to go..



Got up to 1230C (the critical temperature for M2) in a little over 4 hours..

Regards
Ray