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DGentile

Scaling prevention during HT ????

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Ok...

usually I use some Heat-treating stainless foil to cover blades made from strong scaling steels like D2...

however I don't have much of the foil left and it's kind of expensive to get.

 

Now the problem... I today got a bunch of knives from a fellow knifemaker (I offer heat treating services) and he said that it's urgend and it would be good if he got 'em back by monday afternoon...

I told him that I'll see what I can do...

 

the knives all are made from D2 (which I rarely use) and I know this steel, if not protected "developes" verry hard and abrasion resistant oxide-layer which is a pita to remove... which is the reason I normally use the stainless foil to seal the whole blade in (including a thin piece of toilett-paper (which, whilst it burns consumes every rest bit of oxigene left in the "envelope".

 

This methode works good... but as I've said... I don't have enough foil left... and it's kind of "urgent"... no way to get more on monday (it takes at least four days for my supplier to deliver).

 

I know brownells sells a "non scaling compound" however that is only good for steel which have a hardening temp lower then 1600°F... and D2 is arround 1900°F... besides it would take more time for brownell to deliver to switzerland...

 

Now... DO YOU HAVE any recepies for "homemmade" scaling-prevention "compounds", "solutions", "whatever"???

please share :)

 

btw... I anyways am going to build a saltbath for my knives... so the problem will not last... but I would be happy if I can help that other guy out with his "urgent" knives...

 

 

dan

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How about a quick wash of satanite or other refractory?

 

I've heard that some use it to prevent scale formation, and a real light wash shouldn't effect the heat treat.

 

josh

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my only thought on this is a rich atmosphere in a gas forge this should consume most of the oxygen. another idea i have from one of the other forums, i think there was some sort of stainless they were having problems trying to weld so the sealed it in a box brought it up to welding temp etc.

you may be able to do a similar method for the heat treat. basically instead of the foil you used your using a box instead, it may work but i suggest using some scrap D2 first for obvious reasons.

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How about a quick wash of satanite or other refractory?

 

I've heard that some use it to prevent scale formation, and a real light wash shouldn't effect the heat treat.

 

josh

22363[/snapback]

 

Josh, well that could work...

I have some "scrap" D2 pieces arround (leftovers) and will give it a try... I have no idea how a light coat of "AP-Green" will affect the themics and heat-conductibility of the steel... but I'll give it a try...

 

dan

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my only thought on this is a rich atmosphere in a gas forge this should consume most of the oxygen. another idea i have from one of the other forums, i think there was some sort of stainless they were having problems trying to weld so the sealed it in a box  brought it up to welding temp etc.

you may be able to do a similar method for the heat treat. basically instead of the foil you used your using a box instead, it may work but i suggest using some scrap D2 first for obvious reasons.

22364[/snapback]

 

Dracozny,

 

it will not work this way... or at least the results will be "crippled"...

the reason is the airspace which acts as an insulating layer inside the box... even if the box is airtight and all oxygene will be burned during the heat up... due to the "solid shape" of the box there will always be a space between the walls of the box and the blade... heat up is no problem but the quench will not work due to different cooling rates..

 

The Box-Welding works for damascus... you squeeze the whole thing, compress it.... that's a whole different issue....

 

the reducing atomosphere has still too much oxigene to get the material to form a nasty oxide layer...

A kiln with an argon-purge system does work... but that's too much work... I could get one running, but the costs for all the parts, bells & Whistles by far exceeds the costs for a nice salt-pot setup (which I'm getting anyways...)

 

The stainless foil is actually verry thin and formable... if you use it correctly and the vacuum takes it's process the foile will be tight fitted to the blade... quenching works... or with air hardening steels you can just let it air cool...

 

dan

 

I've heard of mixtures made from ash and some types of liquid soap... but I doubt that it will work.. but I maybe expereminet around a bit.

Edited by DGentile

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Tell me if it works out for you?

 

Good luck as always.

 

Edited to add:

 

I'm guessing that it will work as long as the AP-green stays on, which it should? D2 is air hardening, correct? I think that it will cool fast enough, even with the AP-green, but I'm interested to see what happens.

 

josh

 

Josh, well that could work...

I have some "scrap" D2 pieces arround (leftovers) and will give it a try...  I have no idea how a light coat of "AP-Green" will affect the themics and heat-conductibility of the steel... but I'll give it a try...

 

dan

22365[/snapback]

Edited by josh powell

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Guys, I'm listening in on your conversation to learn about this matter too. I have one side question about the ashes/soap combination. I tried to use some dishwashing liquid with no success. Would a powdered soap that has to have water anyway work with the ash and clay mix? I dont want to sidetrack your conversation, so carry on till you have a minute. Thanks, Lin

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i put a pipe inside my forge and as it reaches temp

i throw wood chunks in one end run to the other and insert the blade

works for me

but

i ant doing d2

harley

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... or just throw some wood chunks right inside the furnace or forge.

 

I used to work exclusively with air hardening steels for over ten years and used the foil wrap. The pipe or forge method can create the same kind of "contained reduction" as the foil method. The only difference is you will need more solid fuel inside the chamber or envelope, and you will need to remove the blade from the chamber, pipe or whatever to air cool it. With the pipe method, hammer the back side shut and leave the front open, so you can add wood chunks and withdraw the blade when it's time.

Edited by Tai

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How about using regular borax just as in welding?

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How about using regular borax just as in welding?

22489[/snapback]

I don't think it will serve the purpose, due to two things:

The viscosity of liquid borax... and it's corrosivity... it's kind of agressive on steel... so for heat treating a blade I don't think it serves well...

but I maybe would have to give it a try

 

 

dan

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just a thought.... maybe the borax will work... cause I think it's the high temp of forging and welding that makes it more corrosive..

- i think at the lower temps it maybe ok ??

 

heard jeweler's use boric acid mixed in rubbing alcohol (for flux)... slather it on the piece and the alcohol evaps leaving an even coating.... stuck to the piece...

-maybe that might work...

 

personally,i just use the pipe in the forge trick... but never worked d2 .......woof

 

 

Greg

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Get your self a space station and do it in outer space. :)

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I haven't tried this, but if you welded up a can for a container it should work like the foil. Spray WD40 or put in a piece of charcoal to consume the oxygen.

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... or just throw some wood chunks right inside the furnace or forge.

 

I used to work exclusively with air hardening steels for over ten years and used the foil wrap. The pipe or forge method can create the same kind of "contained reduction" as the foil method. The only difference is you will need more solid fuel inside the chamber or envelope, and you will need to remove the blade from the chamber, pipe or whatever to air cool it. With the pipe method, hammer the back side shut and leave the front open, so you can add wood chunks and withdraw the blade when it's time.

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Hey, Tai, I think I still have the articles you did on making damascus with airhardening stock, I think a point in favour was the stuff had less chance of shearing in HT than oil or water-quench stock.

When DID you eventually come over to the Dark Side, anyhow?

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I haven't tried this, but if you welded up a can for a container it should work like the foil. Spray WD40 or put in a piece of charcoal to consume the oxygen.

22501[/snapback]

 

Don,

 

The canister would need to be tight fitting or I guess the heat los and insulation value would be to great to proivde a successfull quench?

I have used the canister thing for some damascus stuff I did... but for HT? I'm not sure wether this would work...

 

besides this I've heat treated the blades anyways...

 

@all

I had some test-pieces arround (which I prepared from D2 Leftovers)... on which I tested the various "inputs" I got from this thread:

- Coating with AP-Greens... didn't work... D2 gets heated to 1050°C and needs to be held for approx. 20-30minutes for a complete aust.

The AP Green, as it was only a light coating did come loose after a whil

 

- Coating with High Tempereature Paint (till 850°C) whilst this works for the lower temp steels if you need to preserve some surface... it defently doesn't work for D2 at 1050°C-

 

- Coating with a mix of liquid dish-washin soap and Kaolin clay did hold on to the piece at 1050°... but it didn come loose at the quench too fast and scaling still occured... not as bad, but not worth the effort...

 

As I did not have the time or means to "waste" more time on this I contacted the knifemaker who gave me the pieces and told him that he's got two options:

wait till I get new foil or live with the hard to remove oxide-layer...

He told me that it was urgent and he would go with the later option...

 

So I heat treated the knives to a nice HRC 58 (as he wanted)... and gave them back with a nice, hard oxide layer :)

he has since then given me two other knives made from D2 (I don't know what he likes about that stuff... really... I have had better, cheaper, easier to handle steels... and I don't see much of an advantage in useing D2 for smaller knives anyways...)

but these are not urgent... so he will wait till I got new stainless foil...

 

 

about stainless foil:

Tai is right about this... the non-stainless foil will oxidize through and not be effective... and besides this, it's hard to find non stainless foil here...

 

dan

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Guest MPerks89

I may be wrong, but if A.P. Green is created to refract heat, won't it prevent the heat from escaping your knife during heat treating?

 

It seems that the benefits of using a refractory as a barrier would be negated, as your knife wouldn't be able to cool down at the proper rate.

 

I'm not sure what the melting point of glass is, but assuming that it is around the temperature of your forge, this would be pretty cool: Grind glass into dust and apply evenly to the blade like flux. Unlike flux, however, the glass won't react with your blade, and should instead form a viscous "glove" around the knife. When quenching, the quick heat change from extremely hot to relatively cold should cause the glass "glove" to shatter.

 

I'd definately recommend wearing full protection when doing this, and that you stand back when dunking the hot blade into the cold water.

Edited by MPerks89

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I may be wrong, but if A.P. Green is created to refract heat, won't it prevent the heat from escaping your knife during heat treating?

 

It seems that the benefits of using a refractory as a barrier would be negated, as your knife wouldn't be able to cool down at the proper rate.

 

Why not use an oil-based barrier such as beeswax?

22557[/snapback]

 

Of course if the coating would be "thick" it would have a negative impact... but my coat was barely more than "paint"... the test piece got hard...

 

beeswax?? well I don't believe this holds up at 1050°C ?? I mean it will "vaporize"...

or??

 

dan

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Guest MPerks89

...

Edited by MPerks89

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Guest MPerks89

You're right - my idea was faulty, check above for my new one.

And by above, I mean check my first post.

 

(Meanwhile, I'm still trying to figure out how these posts work...)

Edited by MPerks89

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You're right - my idea was faulty, check above for my new one.

And by above, I mean check my first post.

 

(Meanwhile, I'm still trying to figure out how these posts work...)

22562[/snapback]

 

allright... well glass should hold the temp... I'm however not sure at what temps glass liquidifies.... and if in liquid state it would stick to steel...

but I guess it would be worth some experimenting....

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beezewax would have burned off before it got to 300 deg.

and the glass would only bond to the steel once you start boiling the steel and you are not trying to get to that temp range so its not a worry.

glass glove?, i cant say if that will work or not :)

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