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Finally got some of my blades hardness tested today... and I’m not happy with the results
- Thread starter Jesse WW
- Start date
- Joined
- Dec 21, 2006
- Messages
- 3,158
Do what, JTKnives?
I'm still at a loss for your retort against my post. You essentially agreed with what I said, reiterated it, with a slight variation in temps, and then condemned me for saying such.
Yeah, normalizing Aldo's steels. 1650f is a little high for 1084, but I like that normalizing heat. Then you "thermal
Cycle" AFTER normalizing.
Normalizing and thermal cycling accomplish two different things. Normalizing takes care of stress and especially freeing up carbon from its carbides, at the possible expense of austenite grain growth.
Thermal cycling helps to refine that aus grain.
They are 2 different operations to do 2 different things.
If someone has accounted for decarb and the other usual variables, and is STILL getting less than desirable HRC numbers, then normalizing is to be considered. (Discussed plenty of times here on this forum, and why it may be necessary even with stock removal).
Normalizing and thermal cycling achieve different things.
It is true, normalizing is a "thermal cycle". But so is austenitizing. So is tempering.
But we need to distinguish what we are talking about. Simply "thermal cycling", done close to, slightly above, and slightly below, critical temp does not free up heavily spheroidized carbides.
Normalizing does this.
I'm still at a loss for your retort against my post. You essentially agreed with what I said, reiterated it, with a slight variation in temps, and then condemned me for saying such.
Yeah, normalizing Aldo's steels. 1650f is a little high for 1084, but I like that normalizing heat. Then you "thermal
Cycle" AFTER normalizing.
Normalizing and thermal cycling accomplish two different things. Normalizing takes care of stress and especially freeing up carbon from its carbides, at the possible expense of austenite grain growth.
Thermal cycling helps to refine that aus grain.
They are 2 different operations to do 2 different things.
If someone has accounted for decarb and the other usual variables, and is STILL getting less than desirable HRC numbers, then normalizing is to be considered. (Discussed plenty of times here on this forum, and why it may be necessary even with stock removal).
Normalizing and thermal cycling achieve different things.
It is true, normalizing is a "thermal cycle". But so is austenitizing. So is tempering.
But we need to distinguish what we are talking about. Simply "thermal cycling", done close to, slightly above, and slightly below, critical temp does not free up heavily spheroidized carbides.
Normalizing does this.
Last edited:
- Joined
- Jun 11, 2006
- Messages
- 8,651
All I said is I did not see the point in doing 4 thermal cycles especially the 1650° soaking for 10min. The 3 step thermal cycle is normalisation but by stepping it down 100° per cycle it also refines the grains.
I would be interested in one of our resident metallurgist chiming in on this topic
I would be interested in one of our resident metallurgist chiming in on this topic
- Joined
- Jun 11, 2006
- Messages
- 8,651
Yes it is, and that’s the first thing that happens in the thermal cycling 3 step process. Heat to 1650 hold and air cool, then 1550 hold and air cool, 1450 hold and air cool. All I was saying is the first step of thermal cycling is also a normalisation
- Joined
- Oct 17, 2010
- Messages
- 2,424
Yep, what Don said. I've tested tons of blades on bevels before, and usually the reading is ~2 points lower than on the flat. It's not "accurate", but it's not going to show you crazy different numbers, with the typical angles of knife bevels.
Thermal cycling and/or decarb are your likely culprits. We have this convo a lot, I think people really underestimate the amount potential decarb they can get from heat treat, and don't leave enough material often to remove it during finish grinding. This can make your readings 10 points low or more. An easy way to check this, when you're doing the "file skating" test, is file the edge of the blade, and look how deep it files in before it's hard skating and not cutting anymore. That's how deep it is to the non-decarbed material, often, people are AMAZED when I show them how deep it is.
Of course, equally, the assumption so many people seem to have that "I bought steel from a steel vendor, so it must be ready to just harden", can cause just as many problems with HT, even if you're hitting expected hardness, doesn't mean you're getting remotely optimal performance.
Willie71
Warren J. Krywko
- Joined
- Feb 23, 2013
- Messages
- 12,214
If it’s aldo’s Steel, mid 40’s is where you come out if you don’t normalize and cycle. Just part of doing business with this steel. Not every batch needs it, but enough do that I just do all of his steel this way. If you don’t want that hassle, AKS has steel ready to harden without cycling.
- Joined
- Jul 8, 2017
- Messages
- 71
I have been doing a little reading through the forum about thermal cycling to better understand the concept, and I'm having a little difficulty understanding the process(s) involved.
Currently this is pretty much what i have gathered:
Some steel stock is annealed in a spheroidial state. In order to properly harden steel stock that is annealed in a spheroidial state, the carbides need to be properly dissolved into solution. The thermal-cycling process to do this goes as follows:
1. The 1st cycle is a 15 minute soak at 1650f-1850f and is air cooled to black (1200f) in order to dissolve those pesky carbides into solution.
2. The 2nd cycle is a 15 minute soak at 1450f-1500f to evenly distribute those carbides, and is air cooled to black (1200f) to lock in the new smaller grains.
3. The 3rd cycle is done below non-magnetic (1350F?) to remove stress in the blade and make it soft. (Does this cycle really need to be done on non-forged, ground-from-stock steel though? Considering there wont be enough stresses in the piece to really worry about? Do i only need to perform cycles #1 & #2 in this case?)
After these 3 (or 2?) steps, the steel can be properly hardened.
Am i right to assume that thermal cycling should be performed on absolutely all types of steel stock including 5160, 15n20, w2, etc? Or is it just limited to the simpler 10xx steels?
Am i correct in the process i have outlined, or am i off somewhere?
Currently this is pretty much what i have gathered:
Some steel stock is annealed in a spheroidial state. In order to properly harden steel stock that is annealed in a spheroidial state, the carbides need to be properly dissolved into solution. The thermal-cycling process to do this goes as follows:
1. The 1st cycle is a 15 minute soak at 1650f-1850f and is air cooled to black (1200f) in order to dissolve those pesky carbides into solution.
2. The 2nd cycle is a 15 minute soak at 1450f-1500f to evenly distribute those carbides, and is air cooled to black (1200f) to lock in the new smaller grains.
3. The 3rd cycle is done below non-magnetic (1350F?) to remove stress in the blade and make it soft. (Does this cycle really need to be done on non-forged, ground-from-stock steel though? Considering there wont be enough stresses in the piece to really worry about? Do i only need to perform cycles #1 & #2 in this case?)
After these 3 (or 2?) steps, the steel can be properly hardened.
Am i right to assume that thermal cycling should be performed on absolutely all types of steel stock including 5160, 15n20, w2, etc? Or is it just limited to the simpler 10xx steels?
Am i correct in the process i have outlined, or am i off somewhere?
Jesse, it looks like you got it right.
Normalizing (soaking above Ac3) is necessary if you have an unknown hystory or known coarse pearlite or heavily spheroidized carbides conditions from the start....or messed up steel microstructure from forging. So almost always.
Normalizing will dissolve all the "pesky carbides", but it's hot and without carbides left (you dissolved all of them as per definition of normalization) your grain will grow larger than you might like in a blade's steel. The grain will be larger though even in size...normalized; that's why you should follow up with grain refinement thermal cycling after the normalization soak. With every cycle you'll get fresh new grains growing inside the old larger ones until you have filled the matrix with an even, small grain array. I'd suggest don't get tangled in the cool to black thing, it works, but better reaching ambient temperature every cycle to be on the safe side. Ready to austenitize last time and quench.
Expect the process to grow a wicked decarburation layer under the scale, so allow for its removal.
Normalizing (soaking above Ac3) is necessary if you have an unknown hystory or known coarse pearlite or heavily spheroidized carbides conditions from the start....or messed up steel microstructure from forging. So almost always.
Normalizing will dissolve all the "pesky carbides", but it's hot and without carbides left (you dissolved all of them as per definition of normalization) your grain will grow larger than you might like in a blade's steel. The grain will be larger though even in size...normalized; that's why you should follow up with grain refinement thermal cycling after the normalization soak. With every cycle you'll get fresh new grains growing inside the old larger ones until you have filled the matrix with an even, small grain array. I'd suggest don't get tangled in the cool to black thing, it works, but better reaching ambient temperature every cycle to be on the safe side. Ready to austenitize last time and quench.
Expect the process to grow a wicked decarburation layer under the scale, so allow for its removal.
Last edited:
- Joined
- Jan 6, 2005
- Messages
- 9,680
Yes... that'll work. If you forge, that process will dissolve everything. But yes, for most bar stock, unless the supplier gives you the thermal history and current internal structure, you should wipe the slate clean.
Some suppliers, say their steel doesn't require thermal cycling. That may be true. I usually take folks at their word, once they earn my trust... but if they refuse to share basic info about the steel they are offering, the relationship is lost before it even begins.
Some suppliers, say their steel doesn't require thermal cycling. That may be true. I usually take folks at their word, once they earn my trust... but if they refuse to share basic info about the steel they are offering, the relationship is lost before it even begins.