Insulation board.

[92220]

Hi folks.

Does anyone know where I can get 1/4" thick Vermiculite insulation board or something similar? I am experimenting with heating steel parts for soldering, using a portable single ring induction hob. When I worked for Delapena Ltd, back in the late 1960's/early 70's, they invented induction heating of steel parts, for heat treatment. Thinking of that gave me the idea of trying to use a cheap induction hob to try heating parts for soldering. I got a 2Kw hob from Aldi for £29.00, so if it doesn't work to heat steel, I can at least use it to make coffee in the workshop, instead of trapesing back to the house!


I just want to have about 1/4" good insulation to keep as much of the heat away from the glass hob surface as I can, to stop it getting heat damage. I would prefer something hard like Vermiculite, if I can get something. If I can get something, I think the induction hob may be able to heat steel up to red heat. My first experiment was with a sheet of 1mm steel and a blob of soft solder, just to see if it melted. It did. Very quickly, and I left the steel plate on for about a minute and it rapidly changed colour to pale blue so it got damned hot!! If my idea works, I'll report back. It might be a good way of heating sheet steel fabrications evenly so they don't distort.

Bob.

[simplyloco]

Jan 1, 2019 17:34:41 GMT 92220 said:

Hi folks.

Does anyone know where I can get 1/4" thick Vermiculite insulation board or something similar? 
SNIP
Bob.

I'll need some for the back plate of my Scotch boiler, seeing as asbestos sheet doesn't seem to be available anymore. 
BTW Bob, have you tried the hob with your steel plate at a stand off of 1/4"? Inverse square law will apply, thus affecting the power delivery, and the hob may switch itself off as well.
John

[don9f]

B & Q and other places, sell a board called “Hardiebacker” which is available in a 6mm thickness. It’s supposed to be fire resistant and I’ve used it as a “backer” behind my workshop heaters (wooden walls).

But I agree with John’s thinking, the induction hob might not like the use of it as a “spacer” but it will be interesting to find out!

www.diy.com/departments/hardiebacker-backerboard-l-1200mm-w-800mm-t-6mm/150528_BQ.prd

Cheers Don

[jasonb]

The stuff CuP sell can be cut with a bandsaw or even a handsaw if need be, one cut down the middle of the 15mm sheet should do the trick

www.cupalloys.co.uk/brazing-ancillaries/index.asp

Another alternative is "undercloak" board from your local builders merchant or roofers, 3mm fibre cement board about 6" x 48"

[92220]

Hi John.

Yes I know about the inverse square law. Actually I tried raising the steel plate off the hob by 1/4". It does still work which is why I'm looking for 1/4" or 6mm material. The plate still gets damned hot at 1/4" but at 1/2" the magnetic field is too much reduced. It might be that I have to work out some way of suspending the plate in the field but I want to try a piece of solid insulation to see how much it effects the magnetic field. It should have little effect.....hopefully.

Hi Don.

Thanks for that info. I'll look into that.

Hi Jason.

It's not a heatproof material I'm after. I want an inmsulating board to reduce the heat that gets to the hob.

Bob.

[uuu]

I'm looking at my log burner, with its glass door, which stands burning logs resting against it, thinking that the hob might stand the heat OK.

Wilf

[jon38r80]

Mineral fibre cement board, Monolux or Supalux it used to be called and comes in 6mm or 9mm thicknesses its fire resistant (used for facing doors, ceilings etc for fire resistance) . Vermiculite is a bit like weetabix and soft. The stuff i've named is like the sort of asbestos cement stuff you used get in pan protectors for putting on a gas hob before they outlawed asbestos. Used in construction instead of asbestos/cement board.
Its expensive!

[Jim Scott]

Hi Bob

Watching with interest. Have you seen the 'stainless iron' discs that some folk use on induction hobs so as to allow them to use their favourite non-magnetic pots and pans? A thin disc which gets VERY hot and then transfers the heat (very inefficiently) by conduction/radiation to the pan above. There is no doubt that thin steel sheet will heat up fairly quickly and this may be acceptable for soft soldering but would it be fast enough for silver soldering I wonder?

From my experience with Raydyne RF induction heating equipment in the early 1970's considerable RF output was required to heat metals to red heat and above, certainly I remember one of the smaller machines had an output of 15kW. The RF inductors were water cooled and usually made from square section thick walled copper tubing. Its a long time ago now but I recall that success was all to do with getting the coupling correct, a bit of a black art...

Regarding the temperature rating of ceramic hobs, there are direct gas-fired versions available so it would seem that they must be able to withstand red heat..?

Jim S

[cupalloys]

CuP Alloys have two options for you.
They have vermiculite board and a ceramic blanket made from a clay wool.

[doubletop]

Bob

Check out page 10 of the Polymodel Eng catalogue. Boiler lagging ceramic matting 1200 degC in 2mm or 3mm. Not very expensive either

Pete

[92220]

Jan 2, 2019 0:06:09 GMT Jim Scott said:

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[92220]

Jan 2, 2019 0:06:09 GMT Jim Scott said:

Hi Bob

Watching with interest. Have you seen the 'stainless iron' discs that some folk use on induction hobs so as to allow them to use their favourite non-magnetic pots and pans? A thin disc which gets VERY hot and then transfers the heat (very inefficiently) by conduction/radiation to the pan above. There is no doubt that thin steel sheet will heat up fairly quickly and this may be acceptable for soft soldering but would it be fast enough for silver soldering I wonder?

From my experience with Raydyne RF induction heating equipment in the early 1970's considerable RF output was required to heat metals to red heat and above, certainly I remember one of the smaller machines had an output of 15kW. The RF inductors were water cooled and usually made from square section thick walled copper tubing. Its a long time ago now but I recall that success was all to do with getting the coupling correct, a bit of a black art...

Regarding the temperature rating of ceramic hobs, there are direct gas-fired versions available so it would seem that they must be able to withstand red heat..?

Jim S

Hi Jim

I used to work in the Delapena Ltd RF Heating drawing office back in the late 1960's/early 70's. Raydyne bought out the RF division and were were all offered jobs at the factory down South (can't remember exactly where). We were all invited down for a guided tour. While we were there we were shown their research lab. We saw the very first microwave oven in the world!! It was about 6" cubed cooking spcae in a cabinet the size of an american style double fridge freezer...massive!!!

Thanks for that info. I hadn't heard of the 'stainless iron' discs used. That does seem it indicate that i might be on the 'right road'. I have tried having an airgap but I thought it would be better to actually insulate the glass from the hot metal if it was capable of getting up to silversoldering temperatures. That is what I am hoping to achieve. I will report back when I have got some insulation.

Bob

Thank you to everybody who has posted info on brands of 6mm insulation. I'm pretty sure they will all do the job but I shall follow them all up until I get exactly what I am looking for. 

Bob.




 

[jasonb]

Jan 1, 2019 20:10:33 GMT 92220 said:

Hi John.



Hi Jason.

It's not a heatproof material I'm after. I want an inmsulating board to reduce the heat that gets to the hob.

Bob.

From the CuP site "Made from highly insulating and heat reflective vermiculite"

You can stick your hand on the back surface and blast the other side with a torch which is quite good insulation in my book.

[92220]

Hi Jason.

Thanks for clarifying that. That sounds as if it is exactly what I'm looking for.

Bob.

[92220]

While following up on the products suggested, I came across something that may be invaluable for steam locos. It can be used to seal smokeboxes easily. You can apply it with a normal bath sealer gun, in the same way as you would apply bath sealer:-

(Vermiculite)

Heat sealant

HRS - HEAT RESISTANT SEALANT 1300°C
VITCAS Heat Resistant Sealant is a ready to use, pre-mixed, high temperature sealing and caulking paste for use in fixing and jointing, as well as in providing fire protection. Vitcas Heat Resistant Sealant will withstand up to 1300°C.

VITCAS Heat Resistant Sealant is a ready mixed, high temperature sealant. It comes as a caulking paste for use in fixing and jointing in ceramics, metals, silica and glass. The sealant also gives fire protection. Rates to 1300C.

Uses:
• Sealing or fixing ceramics, glass and metal
• Sealing other silica based materials
Application:
Make sure the area is clean and that all dirt, dust, rust and grease is removed. Cut off the top of the cartridge, screw on the nozzle and cut the nozzle to the required size. Apply using a cartridge gun and aim for a thin joint of 2 – 3mm. The material will set at room temperatures but the time will be reduced by applying heat, gradually increasing over a four hour period. When dry, the sealant can be sanded and over painted.

Bob.

Edit:  I should have added that it can also be squeezed out as a string and then applied using a finger to push it into any gaps like between the smokebox  door ring and the smokebox tube, and the smokebox tube and the saddle, etc.