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I need some critique from you experienced bladesmiths


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39 minutes ago, Chris Christenberry said:

What I did was to forge a knife shape................then trace around it.................and then try to design a knife that fit within that outline. 

That's exactly the way I used to do it when I started! :lol:

Don't knock it, it works.

 

 

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Well, as promised, here is my first forged knife.  It was forged at David Moonyham’s shop.  He can correct me if I’m wrong, but I don’t think he physically hammered on the knife.  I did all the work……

Conventional "wisdom" would lead me to say that it's a bit big for a 3 finger, but a bit small for a full sized handle.  It also looks a bit skinny up by the guard and the palm swell is a touch asymme

It's finished!!!!!    Well, the rough prototype is finished!   I won't post any more pics until I'm actually working on the real thing.     

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21 hours ago, Chris Christenberry said:

Well, I'll try and not feel so embarrassed about that particular step then.  Thanks.  Good to know I'm not alone in this process.

Don't feel embarrased, just forge the blade a little oversized and grind/file down to the exact shape. I look at forging as getting the shape 90%, that last 10% will take ten times longer if you want to get the blade to the exact shape. I always marvel at the people that make knives with the "as forged" finish on the spine, I guess that sort of precision with the hammer comes around the 1000 hour+ mark I always think I forged way too thin, only to find out I have to grind off a ton of metal. It must be a learned behavior from the few times I did forge too thin and left a gap in the tang.

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Well, it turns out I inadvertently forged a "hollow" in both sides of the blade as if I were planning on a hollow grind..............which I wasn't.  So when I got my bevels ground down, the blade is a far cry from what I'd originally expected it to be.  It's still going to be a sharp (no pun intended) little knife for someone and certainly sense of satisfaction for me for my first forged knife.  When all of these guys critique it, I'm sure it's going to generate a list of things I'll need to pay attention to on my next knife, but I'm happy with it at this point.  It's ready for heat treating.  Working on my recently designed EDC now that will be heat treated at the same time.  It's the one I started this thread about.  You might say I got sidetracked. :lol:

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What an evening!  I just ran two 1 hour cycles on tempering these blades.  I don't have an oven that will hold a temperature, so I sat on a stool in front of the oven with a digital pyrometer..........turning the stove off and on to keep it within 2 degrees of the required temp.  Pretty boring job, to say the least.  Any way, they are heat treated and tempered and now comes the fun part.  (or at least that's what they keep telling me!) :D

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One thing you can do is bury your blades in a tray full of clean sand while tempering.  The thermal mass of the sand helps to even out the temperature swings in the oven.  For most of the knives I make, I use an old toaster oven with a fire brick in the bottom.

 

Good luck on your hand finishing.  It's an absolute riot<_<.

Edited by Alex Middleton
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Overall looks good minor tweaks based on personal preferences but the big question is how does it feel in your hand...can you reverse the knife direction comfortably without any loss of grip....and no less important are you happy with what it looks like....

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I'm working on two knives at the moment.  One of them is a "stock removal" made from Nitro-V......................... the EDC of which I posted a wooden protype picture.  You guys helped me refine the design.  I've run into a snag I don't understand.  David heat treated the blade for me.  Brought it home and am cleaning the slag off.  Problem is after the HT, it is only about 50% attracted to my magnet I use to hold it while on the grinder.  I can't safely use the grinder because the blade keeps falling off the magnet.  Don't know how to hold it.  Any suggestions?  David says he doesn't understand, but that it seems as if it retained too much Austenite.  Now being the expert metallurgist I am (not)  I not only don't know what that means, I don't know if it's something I can correct.  If I can't correct it, how does it affect my finished knife?  And back to my original problem, how do I hold the danged thing to finish all of my rough sanding on the grinder?

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Some stainless steels are not particularly magnetic.  I don't know about Nitro-V.  However if you have too much retained austenite you may not have achieved the hardness you want from the steel.  Have you seen this procedure for heat treatment: https://knifesteelnerds.com/2019/09/23/nitro-v-its-properties-and-how-to-heat-treat-it/?  Do you know if David did any freezing or cryo after the quench?

 

As far as holding the blade for grinding, there are certainly several techniques to hold a blade without use of a magnet.  You can free-hand hold the blade and just grind on your platten, use a tool rest and grind either by hand or with a jig, use a push stick with and of the options (except the jig)...

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I could hold it easily with the magnet when I did the prep work before HT.  We used no Cryo on it.  It's hard, plenty hard.  Not trying to grind the bevels............did that before HT.  Trying to grind the flat of the handle sides to clean off the slag and improve my distal taper.

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That blasted nitro-v :P

 

I'm thinking something went wrong. But for it to have enough RA to be less magnetic? I've never seen that before. It got hard, but skating a file isn't really the whole story. 

 

I'm thinking finish it up for the practise, and start another one.

 

Two first knives...both better than anything I was able to make for a few years after starting.

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It does sound like retained austenite.  Nitro-V is basically AEB-L with a shot of nitrogen, right?  So no large carbides, shouldn't need true (liquid nitrogen) cryo, but most definitely responds to dry ice.  If you get it there quickly...

 

Larrin at www.knifesteelnerds has a whole post on Nitro-V, https://knifesteelnerds.com/2019/09/23/nitro-v-its-properties-and-how-to-heat-treat-it/. Upon reading that, it sounds like perhaps a slightly too high austenitizing temperature and no cryo can certainly lead to enough retained austenite to affect its magnetic properties.  

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Hmmmmm.  Interesting.

 

Would the knife be sub-standard to any degree to the end user?  I'm wanting to sell it............but not if it's not a good blade.

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*WARNING* I may not know what I'm talking about in some of the following bit of verbiage...  :o

 

What retained austenite does varies, depending on the steel.  The main issue with it is that it is A:) soft, and B:) unstable.  It's soft because it's in the body-centered cubic crystalline phase. It's also not magnetic, which has something to do with the electron energy levels and is beyond what I can safely talk about, even with the warning that started this post.  It is unstable because it really wants to convert to martensite (if there's enough carbon present) or ferrite (if there's not.)  If it converts to martensite, which is the hard phase of steel, it will do so AFTER you've already tempered the blade.  This is why we always say to do two or three tempering cycles.  If you temper once, and you have 40% retained austenite that then converts to 20% martensite upon cooling, that 20% martensite is at full hardness.  It is untempered.  This translates to a brittle blade at worst, and a tendency to edge chipping at best.  The more you temper most non-stainless  and low-alloy tool steels, the more retained austenite you transform to martensite, up to a point of diminishing returns around three or four temper cycles.  With stainless and high-alloy tool steels you get into other issues, the big one being that on many of those the austenite will not finish converting to martensite until it's chilled well below room temperature.  Depending on the alloy that can mean anything from "stick it in the freezer" to "hold in liquid nitrogen for three to four hours."  What seems to be the important thing is that if you're going to do that, it has to be immediately after the quench. 

 

According again to Larrin in this article: https://knifesteelnerds.com/2018/12/03/cryogenic-part1/, even waiting an hour after the quench to freeze the steel will result in "stable" retained austenite in steels that respond well to cryo.  Like all stainless steels.  Stable austenite at room temperature, you say?  Yes.  The 300 series stainless steels are austenitic at room temperature because they have no carbon.  They are extremely corrosion resistant, which is why boat and truck hardware tends to be 316L.  That's one of the most corrosion-resistant common steels we have.   But the 300 series doesn't harden.  Nitro-V has 0.68% carbon, so it will harden.  And the "stable" retained austenite may just be metastable, and may transform to untempered martensite if stressed by bending or heavy cutting.  I don't know.

 

SO to get back to your actual question, what you now have is a blade that's got maybe 30-40% retained austenite (I got this number by WAG).  It may be stable by now, I don't know.  It's enough to make it less magnetic than it was.  IF it's stable, it means the blade will be both softer and tougher than it would otherwise.  A little retained austenite in stainless steel increases impact toughness.  A lot increases it more, but starts to affect hardness when it gets over around 30%.  What this means is your blade will resist snapping when bent, but may not hold an edge quite as long as it could have.  If you do a search on other forums where stainless is the rule rather than the exception, you'll see that many other people have had this exact issue with Nitro-V and with Sandvik 14C28N, which is close in composition.

 

If I were you, I'd ask Garry Keown.  He uses a lot of Sandvik 12C27, which is pretty close to Nitro-V minus the nitrogen.  And he seems to have nailed the HT. 

 

David M.: this does not reflect poorly on you!  These things happen to all of us.  What is your HT setup for the Nitro-V?  That may also have something to do with the end result.  Like, it may just be a decarb issue and not retained austenite at all.... :ph34r:

 

All the above is me trying to figure out what's happening here, stream-of-consciousness style.  I'm working at the limit of what I know about metallurgy in this particular circumstance, so please don't take any of it as proven truth.  I know 10XX and 5160 steels very well.  Higher alloys not as much, and stainless least of all.  I'm working on it, though!  Two years ago I would not have been able to offer any advice on it at all, and look at me now!  :lol: I'm just waiting for Jerrod to chime in telling me I'm full of anti-scale powder, though... 

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We austenized a bit high, at 1980F with a 15 minute soak. There was a bit of decarb for sure. Was using no-scale for the first time and I think it might have flaked off in the oven. I need to investigate that. But under the decarb it was hard. We did have a hiccup during the ramp that forced us to go from 1900 back to 1800 while I restarted the program. 

 

The 80CRV2 blade came out perfect though. Stupid stainless. ;P

 

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If my 12C27 is anything like the Nitro-v to HT then I simply dust with talcum powder and wrap in SS foil, soak at 1960  for 5 minutes and plate quench. Blades come out clean and my 100lb magnet holds them hard. I always grind the SS blades after heat treat.

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That sounds about right. Larrin's recipe is 1950 for 15 minutes. Should have been "ok" at 1980. 

We didn't have the supplies for a cryo, but I didn't think the RA would be anything like what this seems to be.

Need to play with it some more. I've neglected my nitro-v.

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1 hour ago, Alan Longmire said:

 I'm just waiting for Jerrod to chime in telling me I'm full of anti-scale powder, though... 

That is a new one, and I would never say that to or about you.  

 

I would like to start by noting (as I have at other times) that I do not think that these steels are worth the effort.  Only at the upper echelon of users will there be anyone that could appreciate the difference.  The ABS Journeyman test is more abuse than I would ever expect a knife to see, and 5160 works just fine (as do many other simple alloys).  The only caveat to this is where saltwater and other such corrosive environments may favor a more corrosion resistant material.  

 

That being said... I would love to see the TTT for this steel.  Something to really consider is not just martensite start temperatures, but also martensite finish (hence cryo-treatments).  It would be especially nice to see the TTT for this alloy with 2 or 3 distinct autenitizing temps, because that changes things (as noted in the link Dan and Alan posted earlier).  An interesting thing about retained austenite (in addition to the stability and transformation things Alan mentioned) is that it is worse at impact toughness, while better and deforming.  This is a major concern for my day-job with high chrome white irons.  These alloys have very high volume fraction of carbides (25-30% or more).  The goal is to have those carbides in a completely martensitic matrix, because any retained austenite will cause premature failure in impact situations.  The only time that retained austenite is a good thing (as far as I am aware, but I could certainly be wrong) is when dealing with high temperature applications.  You don't want your part to go through phase changes in service, so if it is always austenite, you're a step ahead.  This is done via chemistry.  Check out the Schaeffler Diagram, and importantly the equations for Cr equivalency and Ni equivalency, for a little more insight into controlling phase stability through chemistry.  Things get a little weird with carbide formation versus what is actually in the matrix, too.  Speaking of carbides, that is why the 300 series limits C to low amounts:  to prevent Cr Carbides, not to have austenite, that is just a non-critical side-effect.  The presence of carbides can really throw off a file skate hardness test.  

 

That is all the time I have at the moment.  Hopefully I covered things fairly well.  Please let me know if there is anything else you want touched on a bit more and I'll see what I can do.  

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On 1/3/2020 at 8:33 PM, Alan Longmire said:

because it's in the body-centered cubic crystalline phase

 

Isn’t it face-centred cubic or is retained austenite different from that above A1?

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