1080 clay quench help

taylormadeknives

taylormadeknives

Well-Known Member
I was wondering if anyone has seen this before or if anyone can explain?
I have done a clay quench on several knives using 1084, 1095. I am no expert by no means. I understand the concept of the hamon. With that being said I don't have a clue what happened here. I have heard that 1084 is particular about a clay quench. I have never had any trouble with it. I figured the 1080 would be same. Wrong. It looks great from a distance, but the surface has a grainy textured look. I haven't seen this before. I heard the term thermal banding, but don't know if this is the case. I should mention this was a stock removal project. I normalized 3 times using my heat treat oven at 1600 F. Then I applied clay and on into oven again the next day. I equalized at 1200 if I remember right, then ramped up to 1475 for austenizing temp. I held at temp for 7 minutes. Not sure about soak time on 1080. Shouldn't be any since the carbon is below .084 correct? So all my carbon should have been into solution at this temp and soak. I then quenched in warm fast quench oil. It is the 11 sec. fast quench oil I got from McMaster Carr. After the quench I tempered at 380 F for 1 hr. Then once again for 1hr. I finished grinding the blade, started my polishing process and ended up with this. Sorry for the lengthy explanation, but I realize there are a lot of variables and I wanted to describe my process. If anyone has seen this before I would like to know. I think it is going to be ok, just not preferred. I may stay away from 1080 for a clay quench if this is a problem. What stumps me is I have had great results with Aldo's 1084. This 1080 came from Tracy here at USA KNIFEMAKER, so there is no doubt it is 1080. I have attached some pics. Any advice, help or tips would be great

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Did you etch the blade? I use 1075/1080 from admiral with no issues. I did experience a similar look one time but it was after multiple deep etching cycles while experimenting with the process. I do not soak my blades since I do not have an oven. If I am doing a stock removal I normalize with descending heats, cool to room temp, coat with clay and allow to dry at room temp overnight, and slowly bring up to non-magnetic+ and immediately quench in 120-125 degree oil, then temper 415 for 2 hours. I would eliminate the soak time and see what results you achieve. I'm no expert either, but that's how I do it for what it's worth.
 
Jon Kelly said:
Did you etch the blade? I use 1075/1080 from admiral with no issues. I did experience a similar look one time but it was after multiple deep etching cycles while experimenting with the process. I do not soak my blades since I do not have an oven. If I am doing a stock removal I normalize with descending heats, cool to room temp, coat with clay and allow to dry at room temp overnight, and slowly bring up to non-magnetic+ and immediately quench in 120-125 degree oil, then temper 415 for 2 hours. I would eliminate the soak time and see what results you achieve. I'm no expert either, but that's how I do it for what it's worth.
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Yeah I etched the blade with ferric chloride. I have it diluted to a ratio of 4 parts water to 1 part ferric. It might be the soak time that is doing it. I will try next time just using my forge

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That indeed does look like alloy banding. I thought I had it on a blade I just did on 1084, but turned out to be a decarb pattern that looked very similiar to the pattern on your knife. Even though there aren't many alloys in 1080, the iron carbides can do this, to my understanding. You normalized 3 times at 1600 degrees? I'm no expert either, but I BET you that is what did it. For stock removal this is too much temp. For your first normalizing (it's really called thermal cycling when we don't forge, not really normalizing), a 1600F heat may be good, as long as your successive heats are lower. 1600F 1500F 1400F. How long did you leave the blade in on each cycle? If you left it in there for any length of time over simple equalizing, this will add to your banding problem. Next time I would recommend doing 1550F 1450F 1350F, or you can start with 1600, then 1500 then 1400. You can vary these temps, just make sure they descend, and your last temp being around the nonmagnetic point (1350-1414). Some peopel thermal cycle three times at 1500 or 1450, without descending temps. The key is that it goes through it's crystal change each cycle.

One way to tell if it is REALLY alloy banding is if it will NOT sand out. If you try and try to get it to sand out and it stays there...it is alloy banding, because it is part of the steel's composition. If it sands out...it could be a cool decarb pattern (like I had), or something else.....like your etching.
 
samuraistuart said:
That indeed does look like alloy banding. I thought I had it on a blade I just did on 1084, but turned out to be a decarb pattern that looked very similiar to the pattern on your knife. Even though there aren't many alloys in 1080, the iron carbides can do this, to my understanding. You normalized 3 times at 1600 degrees? I'm no expert either, but I BET you that is what did it. For stock removal this is too much temp. For your first normalizing (it's really called thermal cycling when we don't forge, not really normalizing), a 1600F heat may be good, as long as your successive heats are lower. 1600F 1500F 1400F. How long did you leave the blade in on each cycle? If you left it in there for any length of time over simple equalizing, this will add to your banding problem. Next time I would recommend doing 1550F 1450F 1350F, or you can start with 1600, then 1500 then 1400. You can vary these temps, just make sure they descend, and your last temp being around the nonmagnetic point (1350-1414). Some peopel thermal cycle three times at 1500 or 1450, without descending temps. The key is that it goes through it's crystal change each cycle.

One way to tell if it is REALLY alloy banding is if it will NOT sand out. If you try and try to get it to sand out and it stays there...it is alloy banding, because it is part of the steel's composition. If it sands out...it could be a cool decarb pattern (like I had), or something else.....like your etching.
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Thanks for all the useful info! It sounds like a made a few mistakes. I did the thermal cycling at the same temp and soaked it for 5 min. on each cycle. Sounds like I left it in the oven too long at too high of a temp. I didn't realize that about the iron carbides. It was for sure alloy banding like you described because it didn't sand out at all and it became more noticeable after each etch and polishing. I will definitely be doing it different next time as you described with the descending temps. Thank you for all the help!

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Much of alloy banding is steering of proeutectoid phases by chemistry segregations that occurred during cooling at the mill. The steel is rolled and treated to break this stuff up the best they can but nothing is perfect, and traces of it remain. Then when we heat treat the steel in certain ways we accentuate it by allowing things like proeutectoid (that in excess of.8%) carbide to gather in those areas. Even in simple steels like 1084 there is more than just iron and carbon, there is a substantial amount of Mn in 1084 in particular.

Normalizing, by definition, should be a heat to at least 1600F (with our simple steels) or better, the whole idea behind normalizing is to completely dissolve things into a single phase austenitic condition for homogeneity. It is not in how hot we get it, the hotter the better for homogenizing, but instead how we cool the steel that affects things like banding, this is why normalizing also, by definition, involves air cooling rather than slow cooling via insulation or oven cooling. You never want to slow cool from a normalizing heat or you will get segregation of proeutectoid phases and basically undo all you are trying to do with the normalizing.

fefe3c.jpg

On the Fe/Fe3C phase diagram you can visualize it by reading it from the top down in cooling, rather than from the bottom up from heating. The chart will say “A” for the arrest temps because it was aimed to describe both heating and cooling generally but I will refer to the same temp designations as Ar since we are talking about cooling and I didn’t want to post a separate diagram. The large “V” or delta shaped field above the eutectoid point (.83%C) is the austenite phase field and is where any steel will be in proper normalizing heats. There you will have a total solution of austenite with no leftover phase, i.e. homogeneity. As you cool you will encounter the lines Ar3 (for steels with extra ferrite) or ArCm for steels with extra carbide), this is where those extra phases will begin to separate out of the solution until you reach Ar1 where you will be at the eutectoid level and all of the remaining austenite has then formed homogenous pearlite.

However, what we need to remember is that this diagram is for equilibrium conditions, so it assumes that you hold long enough at the temperatures for diffusion to accommodate these phases forming. For nice homogenous structure you don’t want these separated phases, so that is why it is important not to go any slower than air cooling when normalizing. High temp erases effects like banding and air cooling keeps them gone.

The other cycles that bladesmiths do, Such as heating to 1500F or 1475F and air cooling, do not actually meet the definition criteria of normalizing and really should only be referred as thermal cycling. And it is in the other cycles that most of the banding is accentuated by bladesmiths, provided normalizing was done properly. At elevated temperatures below the Ac/Ar lines carbon will also become mobile but will not necessarily go into solution, instead it will want to segregate out into concentrated groupings, this is the basis of spheroidizing. So heavy cycling, while avoiding proper austenite solution, is the most effective way to bunch up proeutectoid phases and accentuate alloy banding. One can then erase the banding again by taking one good normalizing heat.

It is for these reasons that one should never slow cool (slower than air) any steel with more than .84% carbon from above “critical”, as you will not only make nasty carbide sheets but eventually you will load up the grain boundaries with carbide and have a brittle steel regardless of how soft you think it is. This is the reason that steels like 1095 have gotten a bad rap from bladesmiths for years, because they were treating like it was 1084 or 5160, and essentially handicapping an otherwise excellent steel.

Now I realize that some reading this are saying “O.K. proeutectoid carbide in 1095, I get it, but what about the problem in 1084?” There is also banding based upon pearlite formation, and many of the same thermal conditions will allow the chemistry segregations from the mill to channel and steer pearlite formation and the carbide lamellae therein, not to mention that if you mess up the thermal effects enough that you may even segregate carbide in eutectoid steels.

It is good to remember that almost all desirable properties are enhanced with homogeneity, mixed structures and segregations are generally avoided by industry when they want the best results, and industry tries very hard to eliminate things like banding whenever possible. One case where heavy segregation adds to a property is with ductility in very high carbon steels, under tensile loads such steels may exhibit higher plasticity but this is at the expense of tensile strength. Despite high plasticity allowing a blade to easily bend; we want blades made from strong stuff like steel, not Playdoh. The very common confusion among bladesmiths between ductility and impact toughness must also be pointed out, tensile ductility is NOT interchangeable with true toughness, which or more about impact and sudden loading, like a knife chop, and there homogeneity is definitely the way to go. Large blades need to handle sudden loads in use, I can't think of any legitimate knife use that involves gradual tensile loading, despite the widespread popularity of the concept.
 
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No problem at all. With 1080 or 1084, there is no need to soak for any length of time. There isn't extra carbon to try to bring into solution, and there aren't many alloys either. But carbides do form, no doubt about it, and this is what causes the banding. I like to say that normal size hunting type blades need just 5 minutes max to come up to temp and equalize, but I do 1080 and 1084 for 10 minutes. 5 to come up to temp and 5 to equalize. This is probably the max time you want to leave 1080 1084 in the kiln....10 minutes. Anything longer and you aren't doing anything good, but could be doing something bad. Now alloy banding isn't necessarily bad. It looks cool to some people. It doesn't detract from the performance. Some say it adds to performance and I say hogwash. At the minimum, it isn't easy to duplicate, and that is what heat treat is all about.....nailing it and duplicating it. It depends on the condition the steel comes in as well. Trying to shoot for banding is a crap shoot at best. Best to avoid it, if you can. Sometimes you will get some steel and can't avoid it.

With those descending temps, every cycle creates a new grain boundary and they get smaller and smaller. This translates into a keener edge. You can imagine an edge made out of tiny tiny particles compared to an edge made out of larger particles. The edge with tiny particles can be sharpened keener, and last longer.

I would NOT go to 1600F with 1080 or 1084, especially if you're doing only stock removal. It really won't hurt, as long as you go lower on your subsequent heats, but I think it's just a bit too hot. Start with 1550, 1450, 1350. Then harden at 1500. There is NO NEED to quench during thermal cycling. Just let it cool to black, and then once it is black you can quench in water if you like. Some people say quenching during thermal cycling produces even finer grain....and that may actually be true....but you're risking micro-cracking, especially inside where you can't see it. Air cool is plenty fast enough to form those new boundaries without the risk of cracking during quench.

Kevin and I posted at the same time. He is THE MAN to talk to about heat treating. He will tell you why, not just how.
 
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Kevin R. Cashen said:
Much of alloy banding is steering of proeutectoid phases by chemistry segregations that occurred during cooling at the mill. The steel is rolled and treated to break this stuff up the best they can but nothing is perfect, and traces of it remain. Then when we heat treat the steel in certain ways we accentuate it by allowing things like proeutectoid (that in excess of.8%) carbide to gather in those areas. Even in simple steels like 1084 there is more than just iron and carbon, there is a substantial amount of Mn in 1084 in particular.

Normalizing, by definition, should be a heat to at least 1600F (with our simple steels) or better, the whole idea behind normalizing is to completely dissolve things into a single phase austenitic condition for homogeneity. It is not in how hot we get it, the hotter the better for homogenizing, but instead how we cool the steel that affects things like banding, this is why normalizing also, by definition, involves air cooling rather than slow cooling via insulation or oven cooling. You never want to slow cool from a normalizing heat or you will get segregation of proeutectoid phases and basically undo all you are trying to do with the normalizing.

fefe3c.jpg

On the Fe/Fe3C phase diagram you can visualize it by reading it from the top down in cooling, rather than from the bottom up from heating. The chart will say “A” for the arrest temps because it was aimed to describe both heating and cooling generally but I will refer to the same temp designations as Ar since we are talking about cooling and I didn’t want to post a separate diagram. The large “V” or delta shaped field above the eutectoid point (.83%C) is the austenite phase field and is where any steel will be in proper normalizing heats. There you will have a total solution of austenite with no leftover phase, i.e. homogeneity. As you cool you will encounter the lines Ar3 (for steels with extra ferrite) or ArCm for steels with extra carbide), this is where those extra phases will begin to separate out of the solution until you reach Ar1 where you will be at the eutectoid level and all of the remaining austenite has then formed homogenous pearlite.

However, what we need to remember is that this diagram is for equilibrium conditions, so it assumes that you hold long enough at the temperatures for diffusion to accommodate these phases forming. For nice homogenous structure you don’t want these separated phases, so that is why it is important not to go any slower than air cooling when normalizing. High temp erases effects like banding and air cooling keeps them gone.

The other cycles that bladesmiths do, Such as heating to 1500F or 1475F and air cooling, do not actually meet the definition criteria of normalizing and really should only be referred as thermal cycling. And it is in the other cycles that most of the banding is accentuated by bladesmiths, provided normalizing was done properly. At elevated temperatures below the Ac/Ar lines carbon will also become mobile but will not necessarily go into solution, instead it will want to segregate out into concentrated groupings, this is the basis of spheroidizing. So heavy cycling, while avoiding proper austenite solution, is the most effective way to bunch up proeutectoid phases and accentuate alloy banding. One can then erase the banding again by taking one good normalizing heat.

It is for these reasons that one should never slow cool (slower than air) any steel with more than .84% carbon from above “critical”, as you will not only make nasty carbide sheets but eventually you will load up the grain boundaries with carbide and have a brittle steel regardless of how soft you think it is. This is the reason that steels like 1095 have gotten a bad rap from bladesmiths for years, because they were treating like it was 1084 or 5160, and essentially handicapping an otherwise excellent steel.

Now I realize that some reading this are saying “O.K. proeutectoid carbide in 1095, I get it, but what about the problem in 1084?” There is also banding based upon pearlite formation, and many of the same thermal conditions will allow the chemistry segregations from the mill to channel and steer pearlite formation and the carbide lamellae therein, not to mention that if you mess up the thermal effects enough that you may even segregate carbide in eutectoid steels.

It is good to remember that almost all desirable properties are enhanced with homogeneity, mixed structures and segregations are generally avoided by industry when they want the best results, and industry tries very hard to eliminate things like banding whenever possible. One case where heavy segregation adds to a property is with ductility in very high carbon steels, under tensile loads such steels may exhibit higher plasticity but this is at the expense of tensile strength. Despite high plasticity allowing a blade to easily bend; we want blades made from strong stuff like steel, not Playdoh. The very common confusion among bladesmiths between ductility and impact toughness must also be pointed out, tensile ductility is NOT interchangeable with true toughness, which or more about impact and sudden loading, like a knife chop, and there homogeneity is definitely the way to go. Large blades need to handle sudden loads in use, I can't think of any legitimate knife use that involves gradual tensile loading, despite the widespread popularity of the concept.
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Thanks for the detailed explanation of this topic Kevin. I really got a lot out of it. I really enjoyed reading this. I can't honestly say I understand all of it, but I got most of it. It means a great deal to me that you took the time to explain this to me in such detail

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samuraistuart said:
No problem at all. With 1080 or 1084, there is no need to soak for any length of time. There isn't extra carbon to try to bring into solution, and there aren't many alloys either. But carbides do form, no doubt about it, and this is what causes the banding. I like to say that normal size hunting type blades need just 5 minutes max to come up to temp and equalize, but I do 1080 and 1084 for 10 minutes. 5 to come up to temp and 5 to equalize. This is probably the max time you want to leave 1080 1084 in the kiln....10 minutes. Anything longer and you aren't doing anything good, but could be doing something bad. Now alloy banding isn't necessarily bad. It looks cool to some people. It doesn't detract from the performance. Some say it adds to performance and I say hogwash. At the minimum, it isn't easy to duplicate, and that is what heat treat is all about.....nailing it and duplicating it. It depends on the condition the steel comes in as well. Trying to shoot for banding is a crap shoot at best. Best to avoid it, if you can. Sometimes you will get some steel and can't avoid it.

With those descending temps, every cycle creates a new grain boundary and they get smaller and smaller. This translates into a keener edge. You can imagine an edge made out of tiny tiny particles compared to an edge made out of larger particles. The edge with tiny particles can be sharpened keener, and last longer.

I would NOT go to 1600F with 1080 or 1084, especially if you're doing only stock removal. It really won't hurt, as long as you go lower on your subsequent heats, but I think it's just a bit too hot. Start with 1550, 1450, 1350. Then harden at 1500. There is NO NEED to quench during thermal cycling. Just let it cool to black, and then once it is black you can quench in water if you like. Some people say quenching during thermal cycling produces even finer grain....and that may actually be true....but you're risking micro-cracking, especially inside where you can't see it. Air cool is plenty fast enough to form those new boundaries without the risk of cracking during quench.

Kevin and I posted at the same time. He is THE MAN to talk to about heat treating. He will tell you why, not just how.
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Thank you sir for explaining this to me and taking the time. I really got a lot out of yours as well as Kevin's. I will definitely be doing this method next time. You mention the thermal cycling letting it cool to black then finally go back in the oven to 1500 for the final heat before quench. I do a similar method with 52100 to refine the grain, but I actually quench the blade during the cycling and have never had any trouble. I read somewhere that quenching during the thermal cycling further refines the grain. Maybe I shouldn't be doing it. Like I said I never had any trouble and the grain is very small doing it this way. Actually I can't make out a grain, it just looks silky and smooth when I tested it. I know it sure does sharpen to a very keen edge. Thanks again!

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Hey, you are certainly welcome. Like I said, Kevin is THE guy to talk to, all I can do is relay what I THINK I know!!! Listen, if you want to quench your blade during your thermal cycles.....go for it. Many knifemakers do this exact process. Kevin has done a LOT of research in this area. I believe his conclusion is that quenching during normalizing/grain refining/thermal cycling can POSSIBLY cause micro cracking...stuff you're not going to see or notice....but it's there. POSSIBLY. The theory is that if we allow the steel to air cool and not quench, this negates the possible micro-cracking, but the cooling rate is fast enough to from new boundaries, smaller grains. No need to go to quench speed, just air cool. Seems like Kevin studied this extensively, and he stands in the air cool camp right now. But that doesn't mean you need to change what you are doing. If you're getting the results you want....that's what matters. Possibly smaller grains by quenching? Yep Possible micro cracking when quenched? Yep Possibly smaller grains by air cool? Yep Possibly micro cracks when air cooled? Nope

I don't mean to single out Kevin, either. He has been extremely helpful to me and many others, so his name pops out. There are many others out there who are just as willing to divulge what they've gleaned over their years. I could start a list, but would be leaving out others unintentionally.

Oh, yeah, one other thing.....no need to call me sir!!! Thank you for the respect, tho. I think we need more of it in this world.
 
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samuraistuart said:
Hey, you are certainly welcome. Like I said, Kevin is THE guy to talk to, all I can do is relay what I THINK I know!!! Listen, if you want to quench your blade during your thermal cycles.....go for it. Many knifemakers do this exact process. Kevin has done a LOT of research in this area. I believe his conclusion is that quenching during normalizing/grain refining/thermal cycling can POSSIBLY cause micro cracking...stuff you're not going to see or notice....but it's there. POSSIBLY. The theory is that if we allow the steel to air cool and not quench, this negates the possible micro-cracking, but the cooling rate is fast enough to from new boundaries, smaller grains. No need to go to quench speed, just air cool. Seems like Kevin studied this extensively, and he stands in the air cool camp right now. But that doesn't mean you need to change what you are doing. If you're getting the results you want....that's what matters. Possibly smaller grains by quenching? Yep Possible micro cracking when quenched? Yep Possibly smaller grains by air cool? Yep Possibly micro cracks when air cooled? Nope

I don't mean to single out Kevin, either. He has been extremely helpful to me and many others, so his name pops out. There are many others out there who are just as willing to divulge what they've gleaned over their years. I could start a list, but would be leaving out others unintentionally.

Oh, yeah, one other thing.....no need to call me sir!!! Thank you for the respect, tho. I think we need more of it in this world.
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Thank you again! This info has really helped me out! It has changed the way I think about refining the grain

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Quenching during normalizing could indeed very well involve cracking, micro or macro, I never cool quicker than air from proper normalizing temperatures. The subsequent procedures that we refer to as thermal cycling, as they do not meet the definition of normalizing, may involve a quench with less risk if the temperatures are safely within the proper hardening range, but one must establish the need.

On every cycle from room temperature to above recrystallization and then back to below Ac1 involves 3 separate sets of grains, the initial phase (perhaps pearlite), the new austenite crystals that form on the heating, and then the final phase formed from the cooling of the austenite. So on every heat there are plenty of opportunities to refine grain so long as one keeps the temps totally under control. That last part carries the caveat, for years many bladesmiths haven’t even realized what actual temperature control is; they may have felt confident that they judged “that color right” at best. Now that more of us are understanding what holding a temp within five degrees for an extended soak is like perhaps the morbid fear and obsession over grain size will come into more realistic proportions. It is worth noting that the folks who single mindedly focus on grain size the most often prefer heat sources such as torches or forges, the oven guys seem to have other neurosis ;) .

What I am getting at here is that when you understand how the steel resets itself with every heat the grain size bogy man loses a lot of his potency and so long as you have control over your temperatures grain size is one of the easiest and natural things to control, and that can be done with simple heating and cooling cycles. So yes, you can refine grain quite well by simple air cooling, but things are different with faster rates of both heating and cooling. With faster rates of heating and cooling there are higher rates of nucleation of the diffusional process, i.e. the ground is more fertile for more grains to form at once. So a what you get is that by quenching the steel you get that effect of doing perhaps two air cooled cycles in one heat instead.

So if you think you need to reduce grain size quickly a quench, from an appropriate temperature, could help. Here is an example of how I would use such a step- after proper normalization to equalize grain size and carbide distribution on a piece of steel that I forged the snot out of, such as damascus, I may then bring the grain size down to reasonable size with a heat to hardening temperatures, and then quench. The quench is not radical (no Parks #50) because I don’t care if I get full martensite conversion, in fact I prefer to go for upper bainite for such an operation so I use a sluggish oil and interrupt at a much higher temp. This does a couple of things for me, it gives me a finer phase than pearlite with much less stress than full hardening, it allows me to get things done quicker by not fully cooling and reheating from cold, but it also traps carbide in a very well dispersed and very fine condition rather than big lunky sheets or lamellae.

From here I can go right into a spheroidizing treatment if I want or I can follow it up with more cycles for more effects I may want. But the idea is that I may do it a little different every time, depending on what I have and what I have and where I want to go with it and that is what readers of this need to do as well. This is not a “recipe”, I don’t do recipes. Recipes are for people who don’t know how to cook, I want folks to work out the way that work best for them and that is why I didn’t mention particular steels or temperatures; folks need to work that out for their own methods and materials.

One last word on the subject- carbides. Much of the fixation on grain size over the years has been at the expense of carbide size and distribution. One can get fine edges with large grained steel, the edge just won’t be as stable, but carbide size can indeed limit the quality and fineness of the edge. Proper normalizing is the tool to use on carbides, while subsequent cycles may do other things they need to also be done in such a way that they do not undo the carbide benefits gained in the normalizing. Properly normalized 1075 that is then annealed by heating to critical and stuffing in wood ash is still just fine, but 1095 that sees the same treatment is ruined until it is renormalized to fix it; 1095 has carbides to deal with 1075 doesn’t.
 
To quote Kevin, "Recipes are for people who don’t know how to cook, I want folks to work out the way that work best for them and that is why I didn’t mention particular steels or temperatures; folks need to work that out for their own methods and materials." Needless to say, I don't know how to cook, yet. But my goal is exactly what Kevin is talking about....to be able to answer heat treat questions not because I can repeat what a bladesmith said, but because I understand what is going on. I don't quite think I have it down yet. For the most part, yes. Carbides have me going right now. I'm at a loss in understanding them. For example, in a hypereutectoid steel that has a bit of chromium, a bit of vanadium, a bit of tungsten maybe....there should be a target austenitizing temperature to maximize edge retention. To me...that is what a knife is for. A sharp edge that stays that way...and can be resharpened relatively easily. I could care less if I need to take care of it during/after use. I could care less if I could beat through a redwood tree with it. I want a slicing instrument, and I want it now! Oh no, wait.....that's a commercial. I don't know enough about all this yet to answer, "Using steel "S", to get the most out of it, you need to heat to "T" temp for "M" minutes". I wish I did!

"1095 has carbides to deal with 1075 doesn't". Why is that? I understand the eutectoid point of .8% or so, and that 1095 has a bit of extra carbon past that point. I suppose I just don't quite understand carbides at all, and carbon past .8% and how it is used. Especially in something like 1095. What happens if we heat treat 1095 like 1084, get it to temp and quench without soak? I assume only .8% carbon (theroetical max) will go into solution, and the remaining 1 or 1.5% carbon does what? Does it become retained austenitite, or does it form an iron carbide? And in saying that, Kevin please don't think you have to answer that question, but I sure would read, re-read, and re-read it. I should just do a search to see what I can pick up.
 
Hey, Stuart. Welcome to the head spinning subject of steel metallurgy. When you austinize something like 1075 at temperatures and time sufficient to arrive at maximum solution of carbon into the austinite there is no carbon left over to form carbides with anything. If you do the same trick with 1095 there will be excess carbon left over. That will form proeuticoid carbides, that is carbides that will combine with the some of the iron and the manganese and stray carbide forming elements (thanks to recycling scrap steel). Something like 52100 will never even dissolve all of it's carbides during austinization according the Verhoeven. Because the 1075 does not have any proeuticoid carbides you can't screw them up with a slow furnace or insulated cooling. Something like 1095 or 52100 does have protoeuticoid carbides that you can screw up with a slower than air cooling.

Doug
 
.8% is the magic number for pearlite in simple carbon alloys, at that carbon level the steel will make little else but pearlite when cooled and will go totally into solution when heated to 1335F for complete austenite at the lowest possible temperature. The farther you get from .8% in either direction the more temperature it will take to put everything into solution, the pearlite still converts at 1335F but above .8% you have extra carbide to dissolve and below .8% you have extra ferrite to engage in the austenite solution. The more carbon you have above .8% the more extra carbide there will be to dissolve and the higher the temperature will need to be (see the diagonal line to the right of .83% labeled ACm on the diagram). This works for normalizing but in hardening putting all that proeutectoid carbon into solution is not desirable as it will decrease hardness due to retained austenite, so it is best to scatter it throughout the hardened steel in the form of fine carbides. This is why 1095 has a recommended hardening temperature of 1475F while 1080 or 1084 can be heated to 1500F, and why steels with .50%- .55% carbon are heated even higher than 1500F, the need for total solution is still important but there is little problem with retained austenite.
 
I am loving this thread! There is so much more going on in simple steels that I never realized! Taking notes, so I can put it to good use

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If you want a couple of books to keep on the nightstand for lite reading before roll over and go to sleep try Steel Metallurgy for the Non-Metallurgist by Verhoeven and Metallurgy Fundamentals by Brandt and Warner. Both are like Cliff Notes on metallurgy with Verhoeven's book dealing strictly with ferrous alloys. The two books compliment each other and are probably the next best thing to going down to the local Community College and seeing if they offer an associates degree in metallurgy.

Doug
 
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