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I normalize three times. At the high end of 1600F - 1650F, they stepping down for the next two. If a steel is going to be quenched from 1475F, and the initial normalizing was from 1600F, I'll step down about equally... 1600/1560/1520/quench 1475.

Mike

Mike, in reference to the above quote, and this one,

"...A likely problem with more than three normalizing cycles is decreased hardenibility. With 10xx steels, W1/W2... steels with low hardenibility under best conditions... further reducing hardenibility will cause the steel to not fully harden (thicker sections cannot lose heat fast enough to form martensite)."

Do you do the triple normalize and quench even on your 10XX and W1/2 steels?

I will often do a post-forging high heat normalize followed by two reducing heat cycles, quench at around non-mag + 50 degrees or so and then an oven controlled spherodize for shaping, grinding, drilling, tapping, etc.

Do you feel I am losing hardenability in my W2 and such?

The lowered hardenability is due to finer grain size producing pearlite much more readily. Pearlite initiates at the grain boundaries, particularly at corners where three grains meet. With larger grains there is more inside grain area and less grain boundaries, and there are certainly less grain boundary corners because there are fewer grains. With decreasing grain size all of these points of nucleation increase, and can take the 3/4 second to avoid pearlite in hardening and push it to 1/2 second or less. Anybody can easily observe this by doing a simple exercise with a blade made from 1084. Just quench it normally in oil and clean it up to a 220X finish, you will probably have formed a natural hamon, hardening line where the blade thickness exceeded the speed of the oil. Without any other treatments and without overheating just re-quench the same blade and clean it up again. With each subsequent quench you can move that hardening line closer to the edge as the hardenability lowers.

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......formed a natural hamon, hardening line where the blade thickness exceeded the speed of the oil. Without any other treatments and without overheating just re-quench the same blade and clean it up again. With each subsequent quench you can move that hardening line closer to the edge as the hardenability lowers.

Thanks, Kevin.

Can I make a semi-accurate assumption that if I am having no appreciable difficulty in keeping observable hardening lines/zones above the working portion of the blade that I have not reduced my hardenability to the point of creating minimal martensite?

I don't feel that I am reducing my hardenability by over-doing the thermal cycle steps and my performance testing indicates a rather effective blade.

Very interesting Kevin. Are you indicating that the current blade I'm working on (1084) may not harden properly because I normalized three times and the grain size may have reduced too much, hence too much pearlite==> ie.-the steel can't cool quick enough to properly form martensite, or enough martensite? If this does occur, could I perform a second quench or even a third to increase hardness/martensite? <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//blink.gi f' class='bbc_emoticon' alt=':blink:' />

Not at all, careful normalizing is essential, the only time you may encounter issues is if your quenchant is already borderline in its cooling capabilities. However, should the goals shift from making a knife to making the finest possible grain size there will be these limiting factors with shallow hardening steels. Carbide size and distribution is of much more importance than grain size finer than the ASTM 8-10 it takes to make an excellent knife. As with all things in knifemaking it is all about the perfect balance and compromise to achieve our goals.

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Mike, in reference to the above quote, and this one,

"...A likely problem with more than three normalizing cycles is decreased hardenibility. With 10xx steels, W1/W2... steels with low hardenibility under best conditions... further reducing hardenibility will cause the steel to not fully harden (thicker sections cannot lose heat fast enough to form martensite)."

Do you do the triple normalize and quench even on your 10XX and W1/2 steels?

I will often do a post-forging high heat normalize followed by two reducing heat cycles, quench at around non-mag + 50 degrees or so and then an oven controlled spherodize for shaping, grinding, drilling, tapping, etc.

Do you feel I am losing hardenability in my W2 and such?

Karl,

I read down through the end of the thread before coming back here. I feel, if I'm looking to spheroidize anneal, I'll get small grains (not too small) quenching out of the second normalizing cycle. The reheat up through austenitizing range after the first, nucleates a lot more grains than there were. The quench puts a tremendous amount of strain into the blade and all of the strain points will nucleate grains when heating for final quench... making the grain size significantly smaller.

Still, Kevin is saying three with a quench (with a final quench to come later) is fine.

A person doesn't have to quench out of a normalizing cycle to spheroidize anneal and in that case I think 3 normalizing cycles is "right". I came to spheroidizing before having a kiln and learned it, as well as soaking prior to quench, messing with O1 in a Wayne Goddard design "two brick" forge (forge pics. in article in Blade's "Guide to Knife-making"). If all a person has is a simple forge, quenching out of normalizing then reheating from cooled to black-red/dusty red (below AC1/start of magnetism loss) 3 -4 times is the only way a person can get a spheroidize anneal. It's NOT as soft as an industry-spec spheroidize, but it works.

When I read, "...and then an oven controlled spherodize.", I assumed you were running the quenched-out-of-normalize blade back in at 1250F for an hour +. Now I'm not sure. Seems like you may be running industry spheroidize anneal with the temp soak and step down over hours and hours. If that is so, I wouldn't bother quenching out of the third normalizing cycle. I'll probably evolve to industry-style in time... avoiding the possibility of quench-warp.

Kind of a side issue... because I use a kiln when I spheroidize anneal, it has to come down a long ways from normalizing temps. After the quench out of the second normalizing cycle, I put the blade(s) into a preheated toaster oven ("the tempering unit...") at 300F, and leave there until the kiln drops to spheroidizing temp. (1200F - 1250F)... spheroidizing for an hour after blades come to kiln temp.

In the end, normalizing, with or without quenching, reduces a steel's hardenibility, but the "standard" number of cycles 2, 3, maybe 4, if a person has a true reason) doesn't put me over the edge to where I get natural hamon (incomplete martensite formation). I quench the two fast steels I use (1086 structural cable and 1.03 W2) in Houghto-quench "K" (as fast or faster than Park #50). I've quenched fast steel in Houghto-quench "G" (speed of Park AAA) and used both an interrupted quench at 4 seconds and a quench-to-hand-warm. The interrupted quench did not form full martensite (you can see it in the pictures of the #10 blade I put into my gallery a couple of days ago), but the hand-warm quench did. Two things I think about here... for the hardenibility, the quench medium is near the "too slow" edge for the steel... and a person would be smarter to interrupt the quench after a little longer time... like 7 - 8 seconds. What I did was simple "operator error" and isn't the way it's supposed to be done.

Mike

For what it's worth, I finished my experiment and here's the results. I wish I'd had a camera set up to catch what I saw...

First I took a 1" X 1/4" X 18" piece of 5160 as delivered from Kelly Couples and heated 6 inches of one of it's ends to just above critical and proceeded to forge an area that started 1 1/2" from the end and continued to 3" from the same end. This gave me a 1 1/2" area on the steel that was forged and some untouched areas in front and behind the forged area. I put it through 4 forging cycles only hammering in the area that I determined for the experiment. As it thinned down in the area I was forging, I would turn it on it's side and hammer it to essentially upset it as close to original dimensions as I could get. My forging ended up leaving it at .22 thick at the point of impact. I then straightened the bar as close as I could with one last sub-critical heat. I only hammered in my designated area. After it had cooled enough to touch, I ground the last 8 inches of the bar down to .22 - .21 inches making sure that it was within .01" both longitudinally as well as across it's width. After I had it dimensionally where I wanted it, I heated 12 inches of the bar as evenly as I could in my propane forge to just above critical and then took it into a room that is nearly pitch black so that I could observe the colors draining out of it as clearly as possible. I kept the bar horizontal as it cooled in order to help prevent heat convection up the bar.

What I saw... The area exactly where I had hammered cooled faster or turned black before the inch and a half at the end of the bar or the 9 inches behind the forged area. (For some reason I really expected to see it retain heat while the end cooled to black.)

I heated it a second time, again as evenly as possible, and this time the end 5 inches of the bar cooled to black very evenly starting with the tip first but followed closely by the remaining 4 1/2 inches.

I know that this experiment isn't even close to being controlled but it was interesting to see a difference in colors between the first and second normalizing cycles. I guess the question still remains as to what is happening, but at the same time I was able to somewhat replicate what Ed noticed in his normalizing cycles.

I would agree that these are less than controlled tests to produce reliable data, and could be one of those situations where assumptions could produce a lot of confusion between cause and effect, as has been the case in the vast majority of sketchy bladesmithing concepts. That being said, however, believe it or not it occurred to me that there could be a sound metallurgical explanation for this- changing the rate of recalescence.

Recalescence is exothermic in nature, in other words it gives off energy, if one refines the internal structure enough to increase the nucleation points for pearlite they could raise Ar1 (the point where things come totally out of solution on the way down). This would mean more intense bright area sooner than the area with less points of nucleation for pearlite. Or if carbide was well refined it could do the opposite and retard recalescence, either way it may be possible to put one area out of sync with the rest of the steel by the internal condition when considering energy given off. It is also wort noting that in hardening it is best to void pearlite entirely if you can, since once initiated its exothermic nature can help sustain the pearlite formation as retards cooling by its creation.

Thanks for the explanation of your hypothesis Kevin. If I'm understanding what you're saying, in essence, the steel is possibly giving us a visual cue that things have become "homogeneous" (maybe not the best or most accurate word) due to the multiple normalizing cycles? Is that a fair statement?

Your thoughts regarding nucleation points for pearlite and carbides got me to thinking... Dangerous I know <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//smile.gi f' class='bbc_emoticon' alt=':)' /> ... Since proper normalization is generally credited with helping to prevent warped blades during quench, it would seem to me that if areas of a forged blade are "out of sync", (whether that be from an abundance of pearlite or carbides) with the rest of the blade, that, in itself, could contribute considerably to warpage problems during quench. Essentially, the "out of sync" areas would heat and or cool at different rates than the rest of the blade which could result in warpage. Sound right?

Sorry if I'm jumping to conclusions, the last thing I want to do is confuse anyone else or myself. I for one really appreciate your input and anything you can add is greatly appreciated!

Rick

Rick,

Thanks for taking the time to recreate what I saw...and it does sound like what I saw. I'll be finished forging another blade this weekend (full tang, but I moved every bit of steel except the ricasso area), so I'll try to take pics, however, I'm no photographer <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//wink.gi f' class='bbc_emoticon' alt=';)' />

Kevin,

You are a wealth of information, and before I joined the ABS I never would have understood what you explained. However, thanks to you and others on the forum, I actually do understand <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//cool.gi f' class='bbc_emoticon' alt='B)' /> . What you offered makes sesne, and it will be interesting to see what other smiths see in the future (if anything).

Ed C.

No problem Ed! I very much enjoy a good mystery and am glad that you brought up what you saw. I only wish I had the wherewithal to be more controlled and scientific with it. Every little thing that we can figure out can help all of us as a group.

I look forward to hearing about what you see with your next one.

Rick

|quoted:

Thanks for the explanation of your hypothesis Kevin. If I'm understanding what you're saying, in essence, the steel is possibly giving us a visual cue that things have become "homogeneous" (maybe not the best or most accurate word) due to the multiple normalizing cycles? Is that a fair statement?

Your thoughts regarding nucleation points for pearlite and carbides got me to thinking... Dangerous I know <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//smile.gi f' class='bbc_emoticon' alt=':)' /> ... Since proper normalization is generally credited with helping to prevent warped blades during quench, it would seem to me that if areas of a forged blade are "out of sync", (whether that be from an abundance of pearlite or carbides) with the rest of the blade, that, in itself, could contribute considerably to warpage problems during quench. Essentially, the "out of sync" areas would heat and or cool at different rates than the rest of the blade which could result in warpage. Sound right?

Sorry if I'm jumping to conclusions, the last thing I want to do is confuse anyone else or myself. I for one really appreciate your input and anything you can add is greatly appreciated!

Rick

Not so much homogenized as refined in regards to grain size. Your thoughts on distortion are spot on as it applies to transformation to differential phases. On heating when you reach decalescence (critical temp) the steel actually undergoes a dramatic contraction, it shrinks a bit, as the crystalline array move to a more efficient stacking, so here is where one can get warping on heating if different parts of the cross section heat out of sync. Even wonder why some steels recommend a short rest at a presoak before jumping to the full soak temperature?* On the way back down any phase other than the austenite you now have will result in a drastic expansion as you move back into the less efficient stacking. Martensite will be the most dramatic expansion of all and that is why Japanese swords go into the quench straight and come out curved. But if you make pearlite at around 1,000F in one portion of the blade and not the other, there will naturally be distortion, those same Japanese swords first take a nose dive in the quench and then dramatically reverse their curve when the edge hardens.

Of course the old "edge packing" nonsense was just that, but another thing about it that I never understood was that if all that magic packing was so great for the steel, why just do the edge, why not the entire blade? And of course this is what proper normalizing actually does do, it evenly and thoroughly refines the entire blade, making for less distortion and improved properties throughout. I always say that I feel and even grain size is just as important as the grain size itself, with a mixed grain size you will encounter the issues that you have laid out here.

Jumping to conclusions can be a bad thing if knifemakers then broadcast them as if they were facts, and the more weight your conclusions hold with people the more damage they can do, we already have enough of that going on in our business, and that is why I very much appreciate your recognizing my hypothesis as exactly as I would like it labeled without definitive proof. I see lot of things that blow my mind all the time in my shop and in my testing, but I feel the responsible thing to do is to keep it to myself or label it as my best guess if I don't have a solid data to back it up. Too many other influential folks do not have the same consideration, and I don't want to be another part of the problem.

*well this and some other reasons.

Thanks Kevin! As usual, I've learned something new from you. Thanks again for all your contributions to our community!

So, without jumping to any radical conclusions, and maybe it is one, do you think that what Ed and I have seen is a viable way for us folks that use a forge to heat our steel for normalizing to be able to tell that the grain has been made uniform/normalized? Or is that too much of a stretch? My goal in all of this was to determine if there is a visible way to know that normalization has taken place. Obviously, heating the blade in a controlled environment like a HT oven would be more certain as it pertains to grain type and size. The problem is that a lot of us don't have a HT oven so a visual cue like this would be very useful for folks like me.

Not to side track the thread, but... In regards to the Japanese swords that you wrote about... I was wondering if you know why it is, or at least I've heard, that a blade will drop it's nose if edge quenched in oil but the same blade will have it's nose rise if quenched in water/brine? Based on what I've gleaned from your writing, I'm guessing it would have to do with the efficiency of the quench medium as it pertains to retained austenite in the quenched portion of the blade. I've noticed that my larger blades that I've oil edge quenched, performance test blades to be exact, have all had their points drop by about 1/4" and end up with a slight recurve to the edge (5160 steel & Texaco type A oil heated to 160 degrees).

Thanks again!

Rick

|quoted:

...Not to side track the thread, but... In regards to the Japanese swords that you wrote about... I was wondering if you know why it is, or at least I've heard, that a blade will drop it's nose if edge quenched in oil but the same blade will have it's nose rise if quenched in water/brine? Based on what I've gleaned from your writing, I'm guessing it would have to do with the efficiency of the quench medium as it pertains to retained austenite in the quenched portion of the blade. I've noticed that my larger blades that I've oil edge quenched, performance test blades to be exact, have all had their points drop by about 1/4" and end up with a slight recurve to the edge (5160 steel & Texaco type A oil heated to 160 degrees).

Thanks again!

Rick

Not retained austenite but, believe it or not, pearlite forming too late. I took some time a few years back to explore this problem because it was so often encountered and got some very surprising information about it. Most of the knowledgeable guys out there came close to an explanation that was was widely accepted, but I found the process to be much more complicated and the explanations were oversimplified. When I started to share my findings it wasn't long before I saw some of the guys I shared with telling others that they figured it all out. Obviously I don't get paid when I willingly share information, but a little credit isn't too much to ask. But at any rate here it is...

For things to stay completely straight you need to have the majority of the blade kick over to a BCC phase (pearlite, martensite, bainite etc...) evenly at the same time. If one of those phases is going to be martensite it should probably come last in the line up or the opposite of what you are shooting for could happen. In your case the edge cooled to begin the greatest expansion of all while the spine had not and was still quite ductile. When the expansion occurred there was no anchor on the opposite side of the blade (spine) so the blade compensated for the expansion. However when the spine fully kicked over the edge became an anchor and pulled the whole thing in the opposite direction. With a Japanese sword in water the spine reaches 1000F just at the right time to make it be the anchor for the edge when it transforms, have you ever noticed how they will scrape the spine clean of clay to control the amount of sori?? They knew exactly what they were doing, they just didn't know why.

I had to go deeper than the simple explainations when I saw the reverse effect happen on O-1 blades, blades that shouldn't have any pearlite! So it is all even much more complicated than this, involving phase sequences, timing of quench, amount of extra strain induced by the quenchant, and simple old thermal contraction and expansion falling just at the right place in the line up, and it is all heavily dependant on blade shape and cross section. One can understand how rituals evolved to replicate the successful process as closely as possible.

|quoted:

Not retained austenite but, believe it or not, pearlite forming too late. I took some time a few years back to explore this problem because it was so often encountered and got some very surprising information about it. Most of the knowledgeable guys out there came close to an explanation that was was widely accepted, but I found the process to be much more complicated and the explanations were oversimplified. When I started to share my findings it wasn't long before I saw some of the guys I shared with telling others that they figured it all out. Obviously I don't get paid when I willingly share information, but a little credit isn't too much to ask. But at any rate here it is...

For things to stay completely straight you need to have the majority of the blade kick over to a BCC phase (pearlite, martensite, bainite etc...) evenly at the same time. If one of those phases is going to be martensite it should probably come last in the line up or the opposite of what you are shooting for could happen. In your case the edge cooled to begin the greatest expansion of all while the spine had not and was still quite ductile. When the expansion occurred there was no anchor on the opposite side of the blade (spine) so the blade compensated for the expansion. However when the spine fully kicked over the edge became an anchor and pulled the whole thing in the opposite direction. With a Japanese sword in water the spine reaches 1000F just at the right time to make it be the anchor for the edge when it transforms, have you ever noticed how they will scrape the spine clean of clay to control the amount of sori?? They knew exactly what they were doing, they just didn't know why.

I had to go deeper than the simple explainations when I saw the reverse effect happen on O-1 blades, blades that shouldn't have any pearlite! So it is all even much more complicated than this, involving phase sequences, timing of quench, amount of extra strain induced by the quenchant, and simple old thermal contraction and expansion falling just at the right place in the line up, and it is all heavily dependant on blade shape and cross section. One can understand how rituals evolved to replicate the successful process as closely as possible.

Kevin,

I remember coming across various discussions between you and others on this, but quite a while back. Do you happen to have a link to one that fills out what you mention in your last paragraph here? I'm mostly trying to make simple process connections between "blade shape and cross section", but I'd like to have a better understanding of the whole.

Mike