A little confused

D

DanCo

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Dec 10, 2010
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OK, I am not trying to spread bad information with this post. I am a bit confused right this moment due to a really weird experience. I am working with 15n20 at 3/32 thick. I had some ulus I was working on and they had some crazy bends and twists. I took a piece of stainless plate (304 maybe) and a plate of pig iron, put it in my vice and dropped the ulu in between and tighten. Just a flattening jig really and crude at that. It worked great for its purpose. I then do this same routine with some small blades I made out of the same material. I did this last night. I intended to harden and temper this morning after everything is flat.

This is where I am at a loss. I get to the shop this morning and notice that one blade still has a slight bend in it. I go to straighten this blade and it snaps. I look at the grain and it is velvet. I then hit this blade with a new Nicholson bastard file, skates the file. I go to each piece I did this routine on and they all skate the file. OK, so I think, did I just plate quench 15n20. Look up on the web and can't find much. I go back out to the shop, fire up the forge, take a scrap piece of 15n20 and do the same procedure as last night. Check the steel after putting in between the plates. Skates a file, put it in the vice put pressure on it and snap. Look at the grain and it is beautiful.

So, is it possible to plate quench this steel? Is it because it is so thin?

Thank you very much for any information on this. Also, since these do appear to be hardened, and I did not temper immediately, is it to late to temper these?

Thank you very much,
Daniel Combs
 
Are you even sure its 15n20? It's possible to harden a lot of alloys to various degrees in air/plate, but the degree will vary from steel to steel.

If this is bandsaw steel, maybe its Crucible L6 instead, which supposedly is an air hardening variety, I've seen some stuff that ended up much harder after forging than it was with the original bandsaw ht.
 
I've done a lot of plate quenching on stainless and then when the wrapped (ss foil)
comes about I try 01 between frozen plates- it worked. To my understanding the quicker you
get the temp below the nose the better. With that said I don't believe it would work on all
carbon steels. If it does not ping and you get the temp down faster great. I can't believe
any quenchant will take the temp down faster than frozen 1 1/2" Aluminum plates. Now before
I go hide I'd say yeah you plate quenched it. Draw them and see what you've got.
Ken.
 
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Like I was talking about earlier in our phone conversation Dan, I think this will work with thin stock just fine, but maybe 1/8" or more might not work. Face those Al ingots you have and I believe you should get repeatable results. Even though you didn't intend to, testing by looking at the grain is a good way. A rockwell test would be ideal, but sounds like you got good enough evidence.

Too bad it was my knife that broke, though!


-Xander
 
Hey thank you guys.!!!

Javand, it is band saw steel. It is about 50 yrs old. I was told (not guaranteed I know) that it was 15n20 by the smith I got it from. Now I am not positive. It has definitely hardened better than my current band saw recipe.

kc, Yes it does look like I plate quenched them, but I did not even have the plates chilled and the were only 1/4 in. thick. This has me quite surprised.

Xander, I am working on the new one while I am getting some feedback. I really want to make sure it is right before I run with it.

Thank you again everyone. Anyone else have some ideas or information it is appreciated.
Daniel Combs
 
Yeah there's a lot of acknowledged confusion amongst knife makers as to what steel band saw blades are made from, most will swear up and down that its either all 15n20 or L6. Truth is, there's no telling unless you've seen the certs on it, especially at that age.

I use 15n20 bandsaw blades to make damascus, but it comes from one specific saw mill that buys specific blade stock, and has the sheet to prove the composition.

I'll be happy to test the hardness if you don't have access to an RC tester.
 
Dan
I'm gonna be busy this week with work and the Ft.Worth show but if you want to come by my place the next weekend I'll Rc test them for you.
Stan
 
Ray Kirk, MS, plate quenches a lot of fillet knives from 15N20, but they're under .100". I don't know how successful one would be with almost double that.
But, if it works - it works.
 
I have some bandsaw blade that was tested to be 15n20, but it's only 1/16". If you don"t come to a firm decision, PM me & I'll try plate quenching a piece or two & do some testing.[Evenheat oven] Maybe we can learn something.
 
Hey guys thank you again.

javand, Thank you for the offer. I don't have a tester yet, however Stan doesn't live too far from me so I think I will try to head over to his shop. I will keep that in mind for the future though.

Stan, Thank you and I hope to take you up on that offer. I am trying to get up to Ft. Worth this weekend to check out the show. If I don't see you there, Good Luck at the show. I will be in touch next week and we will make arrangements.

Karl, Thank you for letting me know that it is a possibility that it works. Sorry you didn't have a good day in the shop yesterday. Hope today is better.

Rick, thanks for looking at the thread. Please feel free to give your opinion on what is happening.

Dewey, If you want to test it out, I say go for it. I will be more than happy to tell you exactly how I did it if you want to test my process.

I really thank you guys for the input. I will be trying it out again today on a couple and I will post back what I find. I wish I had aluminum plates so I might make some today. I wonder if that would be even better.

Do you guys think there is a problem with having tempered them the next day instead of immediately? I normally temper right after the quench, due to the circumstances outlined above I did not. I just want to make sure it is OK.

Thank you again,
Daniel Combs
 
Hey bud, my understanding with tempering immediately after quench is to reduce the risk of catastrophic failure or clumsiness and having a glass hard blade sitting around waiting to get knocked off the bench and broken. Tempering the next day or even ten years later will have the same effect as an immediate temper.

So, go ahead and plate quench my knife and I'll test it for you, and I'll let you know. Maybe if you get me that tree rat recipe I'll try the knife out on a couple...


-Xander
 
Hey Xander,
Eating lunch right now. They are all tempering as we speak. I will get you some recipes for the chicken of the trees soon.
Daniel Combs
 
DanCo said:
Rick, thanks for looking at the thread. Please feel free to give your opinion on what is happening.
Click to expand...
I believe Karl had your answer and my small contribution only confirmed Karl's response.

I think you are fine tempering them the next day... just don't make a habit of it.

Xander, there is more to it than a risk of impact breakage. The steel is under tremendous stress just sitting there. Depending on steel type, thickness, surface stress risers and method of HT, the blade could fracture minutes, hours, days, weeks after the quench. Get it tempered as soon as you can but not before the Ms phase is mostly complete (somewhere around 130F or when you can pick it up with your bare hand and not do the hot-potato dance.).
 
Rick, thanx for that clarification. I was under the impression that the quicker the quench the more latent stress was imparted into the steel, I.e. water quench and brine were more prone to building high stress levels in the steel. I know they are more prone to crackin out of nowhere, I've had a few! Sorry to put up bad info out there, but I learn something from almost each thread I read, and this is now in my mental rolodex! Just tryin to learn!


Thanx for not jumping on my case about it!


-Xander
 
Rick is dead on about a wrong temper possibly taking years to crack. A while back when I
didn't have spring tempering down pat I had folders see constant use (usually daily) and then
for no reason crack while sitting on a dresser or nite stand. Combo of use, internal stress, and
god knows what --fatigue? oddly enough when tempered right problem solved.
Ken.
 
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