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Wellburn

15n20 ttt diagram? Bainite questions

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Hi does anyone know where I can find a ttt for 15n20 

I vaguely remember someone mentioning a book with all this kind of stuff in? 

Im wanting to experiment with forming  bainite for Historical martial arts fencing swords as they need a good amount of flex without breakage  and there seems to be bugger all information out there 

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Here's one for 1080, and 15n20 is reasonably close:

2-Isothermal-%E2%80%93-Transformation-Di

I honestly don't know how much effect the 2% nickel has on the curve, but based on how it performs in 1084/15n20 pattern-weld I suspect not much.

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2 hours ago, Alan Longmire said:

Here's one for 1080, and 15n20 is reasonably close:

2-Isothermal-%E2%80%93-Transformation-Di

I honestly don't know how much effect the 2% nickel has on the curve, but based on how it performs in 1084/15n20 pattern-weld I suspect not much.

Thanks! Is this combo of Damascus bainite doable? Or will the welds fail on repeated flexing? 

 

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That's beyond my experience, but in theory if the welds are good it should work.  Howard Clark's L6 and 8670M bainite swords are pretty much indestructible, but then they are monosteel and higher alloy than 15n20.  He uses salt pots.  What is your setup?

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I've been looking at molten lead or tin or a combination, as that's what wilkinson sword were doing and it's less expensive and dangerous than salt pots 

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You have to be careful about working around molten lead to avoid heavy metal poisoning. Use plenty of ventilation and stay away from your pot because you are going to want to soak the blade at just above the Ms point which, depending upon the alloys in question could take hours for complete conversion to bainite.  You might want to see if you can locate bismuth.  The last time I ordered babbitt metal from RotoMetals they carried it.  I believe it's a lot less toxic than lead.

Doug

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18 hours ago, Wellburn said:

 less expensive and dangerous than salt pots 

Why would low temp salts would be more dangerous than molten lead?  I think low temp salts are a faster quench than lead so you have more time to 'avoid the nose'. Low temp salts would be handy for doing 'Blueing' as well which you might find a use for... and it is easy.  Where do you think the extra cost is? 

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That's a good point.  Unless you already have a few hundred pounds of lead or tin lying about.  Low-temp salts are relatively benign as long as you don't spill them on organics like wood or cloth.  Then you have a fire hazard.  High-temp salts are indeed dangerous, but I'd rather deal with them than lead at austenitizing temps due to the toxicity of the vapors.  Your neighbors might not like the idea either.  I know industry used to use lead for the purpose, but they were forced to switch to other means for safety reasons.

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Maybe I will go with tin or possibly bismuth, 

unless anyone can direct me to a salt pot with greater than 45 inch depth that doesn't cost more than a small country 

even then I know nothing about salt pot safety except the people say it can go off like a volcano,  whereas molten metal I know quite well 

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 I've just read a bit more on salt. I think I might be ok with a low temp one if I can get over my fear of wiring and electrical diy stuff and make one, might ask you for a few pointers when you're down Mr Hobson :-) 

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For just starting out experimenting, I think this can be really low tech. The salts are good for: quick quench, thermal mass, reduce oxidisation. I think you can get all these benefits by having a small trough inside an oven... get it up to heat, then quickly open the door and drop the blade into the trough, slam the door shut. For a one-off, I would guess any iron/steel trough would do. You probably only need thick stainless if you are doing this repeatedly. However, I am guessing  so do this on a non-organic floor!

I have proper 20kg of salt I (well, Owen) bought 10 years ago and I'm still waiting to use them. Back then, it seemed difficult to get nitrate salts in quantity because they make good weapons. Now it seems much easier to buy potassium nitrate (which i think is a key low-temp salt - melting point 334° C so needs mixing with some other salt (mixtures are always lower melting point - something to do with entropy :) )) in reasonable bulk. So take a look at the salt recipes... used to be here https://www.bladesmithsforum.com/index.php?/topic/6375-heat-treating-salt-recipies/&page=2 but all links seem broken.  I'd love to see that document again :(

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I reckon I can make an oven and a trough, sounds much more doable I will probably do a batch of 2or 3 at the same time which will most likely keep me going for a while 

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Re-reading... I would guess that a  horizontal quench could increase warping for a fencing blade. Vertical oven would be the way to go but initially the 'tank' can be thick wall steel pipe - just make sure to empty it of salt and check it after each use.

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