Hypereutectoid steel

the possum said:
Thanks a heap for startin' this thread, Kevin. I slowly pick up another nugget of info each time I read this stuff. If you start a thread like this every month, maybe I'll have a decent grasp of it before I die. :D (Only meaning my feeble possum brain can't handle much in one sitting; Kevin can convey the info in a manner easier to digest than most.)

On a side note, I was eagerly following this thread the first couple days. I kept thinking to myself how well the thread was going; how much good info was being shared. Then I actually wondered to myself, "Did Tai Goo's computer crash or something?" I didn't think he could stand to let such a thread be. And now I see I was right. Tai, I respect your creativity, design skills, and metalsmithing abilities. But c'mon, dude. You are not The Oracle from The Matrix. It is not your job to "unbalance" every equation you encounter and add chaos to order.
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LOL :)


I guess I can't say anything on one of these types of threads without disrupting it and drawing unnecessary/unwanted attention to myself. So, just leave me out of it and let me shut up,... if that's O.K.

I’m all for letting order come back out of the chaos… :)
 
The discussion that Nick and Mete had makes me worry...

When using O1, I have been doing exactly as Nick described, making a stock removal blade, soaking it for 15 minutes at 1475 F in my gas forge, then quenching in Parks AAA. I do it this way because, frankly, if I forge it I'm liable to screw the steel up more than I can repair with my current equipment.

Mete's comment that Nick's procedure was "OK if prior HT is OK" is what made me worry. I have been buying Starrett precision ground spheroidized flat stock because I have assumed that the steel company has put their steel in good order before it gets to me. But should I be so trusting?

With the problems that Kevin mentioned with steels coming from the mill with a "segregated stringer of concentrated carbide running right up the center" or "segregation and other issues from the milling manufacturing process", is it really safe to assume that the steel you buy is what it's supposed to be? Perhaps it would be safer to assume the steel is screwed up and to always go through the heat treating procedures that will fix it?

Since you guys use a lot more steel than I do, how much faith would you put in steel from Starrett? Is there a more reliable manufacture that I should be going to?
 
without going through all the possibilities the most common is improperly annealed material.Drill a hole in it or file it .If it's difficult to do it's not annealed.You have pearlite instead of spheroized carbides.
 
Now I'm just guessing, but Starret PC 01 is spheroidized annealled. I would think it would be in very good structure as it comes, but I would like to see Kevins thoughts on it. I see Mete already gave his opinion on the matter. For the record, I have never gotten a piece of Starret 01 that wasn't well annealled, but the day may come.
 
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Hi NTS

i should point out that this thread is more to deal with modern hypereutectoid steels.... and not to be confused with ancients steels... .. as i think in alot of cases they avoided using ultrahigh carbon steels.. except for crucible steel and that is processed in an entirely different manner to deal with the surplus of carbon..



never too sharp said:
You metalurgist types make it worth the price of admision here EVERY DAY. Although, this is coming from someone who's dream occupation is an archeometalurgist.

Thanks for the science that explains my(our) obsession. You guys rock. :thumbup:
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Mete, in Nick's question of the 3 steel conditions, I have a question?
condition 1 was only normalized with no speriodize
condition 2 was heated to 1500 instead of 1400 missing the lower heat and possibly causing a larger grain than wanted.
condition 3 .. with the same thought that I asked Kevin,
wouldn't you want to hit the temp at 1500 deg since he has the equipment to do so >> to put the most amount of carbon into soultion?
The above are all in question form, and not in challange form. Just using what you and the rest have tried to teach.
Nick thanks for the 3 steel conditions, and in no-way am I useing your part of the post in a bad way!!!!!!
 
Chris Meyer said:
...With the problems that Kevin mentioned with steels coming from the mill with a "segregated stringer of concentrated carbide running right up the center" or "segregation and other issues from the milling manufacturing process", is it really safe to assume that the steel you buy is what it's supposed to be? Perhaps it would be safer to assume the steel is screwed up and to always go through the heat treating procedures that will fix it?...
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For the most part much of this is splitting hairs on the final performance in knives. Banding and as far as all of our marketing [[[[[us believe. Most industrial applications really test the properties much more than the sharp piece of steel we carry on our side for cutting twine, skinning a dear or whittling. Compare that to an O1 slitter blade that cuts thousands of feet of abrasive onditions, and yet the maker and the end users have found them quite wonderful. There are a good numinconsistencies have always been a part of traditionally milled steels and many knives have been made using many methods which simply cannot result in optimum cand yet their knives are prized by many. Knives really do not push the steel performance envelope ber of people using methods that exaggerate and intensify these issues that you have concerns about Chris, material per hour!
 
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Thanks Kevin, that’s a relief. I just hope that all your worrying over the condition of your steel isn’t rubbing off on me. :eek:

Since you mentioned Ashokan and said that “Knives really do not push the steel performance envelope as far as all of our marketing and fantasies would have us believe”, I thought of another question to ask. During your Sunday lecture at Ashokan 2008, you showed some metallography of Martensite in steel that had been soaked for a relatively short time, and another of a piece that had been soaked for five hours. The five hour piece had much more Martensite than the other piece. I had always been under the impression that, if we heat treated a knife blade properly, it would end up being mostly Martensite. However, judging by those pictures, that’s not the case. Assuming that I am interpreting those images correctly, what percentage of Martensite should we realistically expect in our blades? Would it be advantageous to try soak my blades longer to make more Martensite (and just learn to deal with the resulting decarb), or, as you mentioned, is that more of the “big problem we all suffer from is assuming that if a little bit of something is good then a whole lot must be great!”??
 
I was interested in the same thing. Was I misinterpreting those pictures of the O1 soaked for 10 minutes as opposed to the 5 hour soak which showed all that more martensite?
 
Go back to the reasons for the soak . Starting out with spheroidized structure the soak dissolves the carbides until the matrix is saturated .The carbon then must diffuse throughout the matrix.
Carbides are not all the same .Some dissolve easily [Fe and Cr] but others are difficult to dissolve [Mo,W,V].If the steel has one of the harder to dissolve carbides a longer [and even a higher temperature ] soak will get more carbon in the matrix and better properties.
 
'I am certain any number of people reading this could share a story of 1095 splitting, 1084 opening up in working or black stingers cropping up in the polishing of 5160."
Not to go too far off the track here, but this is the first time I have ever read anything that touches on my experience about 10 years ago with a bar of 1/4 x 1" 1085 that I was forging into a skinner. As I worked the point down , the bar delaminated down the centerline just as pretty as you please. I welded it up ,at a high heat of course, and it turned out well. The high heat required for the forge welding would have accomplished the "homogenizing" of the other wise segregated steel.
 
Chris Meyer said:
Thanks Kevin, that’s a relief. I just hope that all your worrying over the condition of your steel isn’t rubbing off on me. :eek:

Since you mentioned Ashokan and said that “Knives really do not push the steel performance envelope as far as all of our marketing and fantasies would have us believe”, I thought of another question to ask. During your Sunday lecture at Ashokan 2008, you showed some metallography of Martensite in steel that had been soaked for a relatively short time, and another of a piece that had been soaked for five hours. The five hour piece had much more Martensite than the other piece. I had always been under the impression that, if we heat treated a knife blade properly, it would end up being mostly Martensite. However, judging by those pictures, that’s not the case. Assuming that I am interpreting those images correctly, what percentage of Martensite should we realistically expect in our blades? Would it be advantageous to try soak my blades longer to make more Martensite (and just learn to deal with the resulting decarb), or, as you mentioned, is that more of the “big problem we all suffer from is assuming that if a little bit of something is good then a whole lot must be great!”??
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Nothing is 100% but martensite in simpler steels particularly one like O1 is about as close as we can hope. The only parts not martensitic in those images should have been the residual carbides which is not only expected but a good thing as long as they are fine an evenly distributed. In 10XX series steels it is not uncommon to have fine pearlite in the mix and in hypoeutectoid levels there could be left over ferrite (iron). But with hypereutectoid steels with any alloying you should have a solid field of martensite with those fine carbides until the free carbon or alloying gets high enough to cause retained austenite, which definitely is not complete martensite conversion and something to be concerned.

Actually the images of the 10 minute soaked O1 and the 5 hour O1 both contained the same microstructures and each contained essentially the same amount of martensite, the only real difference between the two was the number and size of those carbides. The 5 hour soaked carbide were obviously much smaller and fewer. Now the image of the slightly spheroidized pearlite earlier in this thread is another story. Simply taking an alloy steel to non-magnetic with no soak before quenching will result in very little martensite surrounded by messed up pearlite and ferrite. Which, as we have discussed a previously, will simply dull a new file but still be lousy in the long run.

So we have the two extremes, no soak and hours of soak, the realistic approach is get it up to temperature let it soak at that heat long enough to get things done and quench. That time is realistically on the order of minutes, 5-15, and not hours. This will give you a good even fully hard martensite with a nice dispersion of fine carbides, and it doesn’t get much better than that.
 
lcf- No worries! If I wasn't willing to get responses (good, bad, or in-between) I wouldn't post in a thread like this. I'll admit it's a tad intimidating putting yourself out there, but I'd rather welcome constructive criticism and learn than keep this all in my shop and possibly never reach optimal heat-treating methods. :)

Of course I can't find it right now, but I have it written somewhere that the annealing temp for O1 was 1500F. So is it actually 1400?

Kevin, I'd be glad to help out if I can! So how are you normalizing now? I must have missed that.

Thanks guys! :)
 
I went and found my shop notes, and I did the annealing at 1450. So I guess I split the difference between right and wrong ;) :D
 
Thanks for clearing that up Kevin, I guess I did misunderstand the slides you showed.

Nick, the Heat Treater's Guide says to heat O1 to 1400 to 1450 F to anneal it. "Use lower temp for small sections, and the higher temp for large sections." Holding time is 1 to 4 hrs, depending on whether its a light or heavy section.

There's more, but I'll just email it to you.
 
NickWheeler said:
...Kevin, I'd be glad to help out if I can! So how are you normalizing now? I must have missed that....
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No, you didn't miss it, it is not here. Contrary to what is sometimes suggested I am very careful not to put too much of my own personal methods in my posts. I put the proven principles that guide my methods, but for much the same reason I don't make a habit of posting my knives I like to keep my input just about the objective metallurgy and allow those who can use it to develop thier own practices without everybody just following yet another recipe. We have more than enough smiths pushing recipes on the way to make the greatest knives, and not enough just giving out the basic information on how the individual can work out their own sound methods, so instead we have a hodge podge of parts of famous guys methods instead of an understanding of why we would do any of it. For example, the guy who after edge packing, torches a blade edge up to temp to quench into goo 3 times before packing in dry ice and acetone, or on the opposite end of the spectrum the guy who goes right for a low temp salt bath in order to make bainite or martemper without even considering why:confused:. This is not a critique of your normalizing in any way just an explanation of why a guy like me who shoots his mouth off so often needs to keep his head clear about what he is promoting and what he is not.

I normalise using other heat sources than the salts due to the issues I have had, but I have heard many folks talk about good experiene with the salts, making me always wnat to ask if they could do and etch and let me know if I just had a couple of bad days with the salts, you happened to mention it while I was thinking about it so I finally asked. I seemed to have encountered an oxidizing issue with the salts cooling in air on the blade and then re-entering the bath.
 
Nick, thanks for not being offended by my using your post. I agree that it takes courage to put it on the line.
In the past I have done the same here also, and then thought the better of it.
1400deg is from pg 533 of the Heat treaters guide. With the range being from 1400 to 1455deg. with a sub note of using the lower temp for smaller parts. Along with a detailed reducing temp step on the cooling.
And from what I read above, Chris is mailing more info to you.
My point was in the "hair splitting" that I think alot of us are zeroing in on is what I was focusing on with the temp questions. Since this thread is past the heat it to red and stick in peanutbutter Q&A.
Then after reading Kevins last post I realized that my question was possibly a little too "to the point". That it would stem more into the recipes answer (for the way I asked the question).
My main goal was to determine if the steel does see a change in that low of temp difference.
The book say's it does
 
No problem lcf :) There's not too many things I can't stand back and laugh at myself over.... Wait, I don't think there's anything I can't/don't make fun of myself for :D

Chris very graciously sent me the pages from the Heat Treater's Guide. I've been wanting to buy it for years, but every time I try to find it I come up empty handed. Chris sent me some links... can anybody tell me if there's an appreciable difference between an early 80's copy or a more recent copy... with knifemaking in mind?

I guess with 1450 I wasn't too far off, but it certainly seems I'd have been better off with 1400.

Kevin- I don't totally understand where you're coming from, but I think I do for the most part. I know you want to help people understand what's going on in the steel and not just give a recipe that someone can blindly follow. And hype has driven some really crazy "legends" in knifemaking.

I was surprised as I thought you used salts almost exclusively for your heat-treating.
 
NickWheeler said:
No problem lcf :)Chris very graciously sent me the pages from the Heat Treater's Guide. I've been wanting to buy it for years, but every time I try to find it I come up empty handed. Chris sent me some links... can anybody tell me if there's an appreciable difference between an early 80's copy or a more recent copy... with knifemaking in mind?
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Nick,

This may help looking for Heat Treater's guide. http://www.usedbooksearch.co.uk/ This outfit searches about everywhere or connects to outfits that have huge numbers of sellers.

1982 Ed. ISBN: 0871701413
1995 Ed. ISBN: 0871705206

Don't be drinking anything when you search for the 1995 edition or you'll swallow your tongue, too.

I solved my "want it" problem by getting a copy through inter-library loan and making copies of the material I wanted for my personal reference.

Mike
 
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