What did I do?! Normalize 1095...

B

Black cat

Well-Known Member
Im prepping a couple of 1095 for my first attempt at a hamon.
After the rough grind I normalized at 1575 and cooled in still air...

Ok now what? I've never normalized before... They are hard as heck.
I'm using 80 grit and it's not having any effect at removing the carbon scale.

Did I miss a step?

I assume I have to get all the scale off before I add the clay?
 
You've normalized the blade. Carbon scale can be difficult to sand off especially with some of the softer abrasive belts. You might want to try soaking in white vinegar overnight and then scrubbing with a brass wire brush. That should remove most of it and make what remains easier to grind off.

Doug
 
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It occures to me now that they are normalized and so hard. Do I have to anneal them to clay coat for a hamon? or will the HT after the clay allow the spine to soften and the edge to harden?
 
You may have caused some hardening in the air cooling , next time get yourself a bucket of vermiculite and stick your blade in the bucket , the vermiculite will act as an insulator and slow the cooling.
 
I... Would say. The blades are very HARD now. Just from air cooling? This is strange to me, my plan is to de scale the blades and then apply the clay and back into HT. It... Doesnt make sense to me but all the proceedures I read dont seem to mention the blades being so hard at this point. Just "normalize to prevent cracking, clay, HT, temper.
 
I would have to respectfully disagree about air hardening 1095. The nose of the cooling curve is way too far to the left of the diagramto get martensite formation during air cooling. Personally, I don't anneal my blades as I understand that this can cause coursening of the carbides. As far a clay coating for a hamon it should work fine to give you a soft spine and a hard edge. With the relatively low hardenability of 1095 you could well end up with a soft spine and a hard edge even without any clay coating just from the effect of quenching something as thin as a blade. The blade will only harden to a certain thickness determined by the speed of the quenchant and the grain size of the steel with small grain size decreasing hardenability.

Doug
 
If it really is 1095 it will not truly air harden. True hardening involves entrapment of carbon in solution to form martensitic structure, and you need to cool from 1430-1500F to below 950F in less than .5 seconds in order to achieve that in 1095. But what can happen is carbide segregation into course networks which will be the equivalent of sheets of diamonds mixed into a ball of soft clay. A file will simply skate off from this but a Rockwell penetrator will bury itself into it. I implore you- do not use lamellar annealing practices with 1095, it will only make this problem much worse. Lamellar annealing is slow cooling from critical, ala wood ashes, vermiculite, or cooling forge, will only make this segregation problem much, much, worse. There are two methods of annealing, lamellar and spheroidizing, the latter is a subcritical or isothermal method that you want to use for 1095. Normalize exactly as you have done and then follow it up with several heats to around 1300F (reddish color) but never allow the magnet to stop sticking, if you do, start over again. This subcritical cycling will take all of those carbides sheets and turn them into very tiny spheroidal globules within the iron matrix for a very soft structure. If you find that you still have some issues with hard areas then the carbides are not spheroidizing evenly, to help with this you can follow up the normalization with a heat to 1475F and a quench to trap things into solution. When this solid solution is then spheroidized at around 1300F the carbides will be much more finely and evenly distributed.
 
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Kevin R. Cashen said:
If it really is 1095 it will not truly air harden. True hardening involves entrapment of carbon in solution to form martensitic structure, and you need to cool from 1430-1500F to below 950F in less than .5 seconds in order to achieve that in 1095. But what can happen is carbide segregation into course networks which will be the equivalent of sheets of diamonds mixed into a ball of soft clay. A file will simply skate off from this but a Rockwell penetrator will bury itself into it. I implore you- no not use lamellar annealing practices with 1095, it will only make this problem much worse. Lamellar annealing is slow cooling from critical, ala wood ashes, vermiculite, or cooling forge, will only make this segregation problem much, much, worse. There are two methods of annealing, lamellar and spheroidizing, the latter is a subcritical or isothermal method that you want to use for 1095. Normalize exactly as you have done and then follow it up with several heats to around 1300F (reddish color) but never allow the magnet to stop sticking, if you do, start over again. This subcritical cycling will take all of those carbides sheets and turn them into very tiny spheroidal globules within the iron matrix for a very soft structure. If you find that you still have some issues with hard areas then the carbides are not spheroidizing evenly, to help with this you can follow up the normalization with a heat to 1475F and a quench to trap things into solution. When this solid solution is then spheroidized at around 1300F the carbides will be much more finely and evenly distributed.
Click to expand...

From the mouth of the Master when it comes to HT! I must admit Kevin will never steer you wrong but, sometimes I find myself shaking my head at the end of reading what he said but, he usually explains it well enough for even me to understand!!!!

Some of this technical explanations are beyond me. However I look at it like this I don't know why a plane flies but it is enough for me to understand that it does fly!!!:biggrin:
 
Wow thanks Kevin! That makes perfect sense. I kept thinking these knives shouldnt be hard but couldnt for the life of me figure out why they are hard. What you described explains what I'm seeing here.

Should I be removing the scale prior to the sub critical heats? I dont think it will matter but thought its worth asking.
 
Leave the scale on, if you are going to decarb or oxidize the outer skin why not let it be the crud you are going to grind off anyhow?
 
Thanks again Kevin! That was kind of what I was thinking. I just comleted my third cycle at 1300 cooling in still air between. Next I will put them in at 1475 then quench in the canola (all I have) then de scale and apply clay.
Never having attempted a hamon before I think that's the process.
I still have to look up the temp for HT the 1095 i'm guessing in the 1500 range. And I will do the final quench in hot water.
 
You have it a little backwards. You want to apply the clay to the blade and then harden by taking the blade up to about 1450-1475° and then quenching in oil. I'm also a little unsure of what you mean by a final quench in hot water. Are you thinking about an interrupted quench where you quench in oil for three or four seconds and then immediately switch to hot water until the blade is cool enough to handle? If you are talking about multiple cycles of austenizing the blade and then quenching I would recommend against it. That would give more opportunities for microscopic cracks to develop where the plate martensite intersect.

Doug
 
LoL now i'm confused too :p The 1450-1475 then oil quench was based on Kevins advice to trap the carbodes in a solution then sphearoidizing at 1300 to evenly distribute the carbides. But... I suspect this step was more of an "after normalizing" or if I still have hard spots but I did it anyway.

So after the 1475 I ddi a final heat too 1300 and air cooled. I will have to heat again tomorrow because one blade has a small warp.

Now in theory the blades shouldnt be hard having come from a sub critical 1300 heat and air cool.
They still feel a little hard but not as much as they did yesterday.
I think it's as Kevin mentioned stratification? of carbides.

The next step as far as I know now is too clean off the scale and apply the clay. Allow to dry overnight then HT.
I've read you can do a 1095 hamon quench in canola. I've heard hot water quench works better but more chance of cracks or breaking a blade. Thats why I started with the "normalization" kind of wish I hadent because it's taking me into uncomfortable territory (techniques I dont feel ready to attempt) but hey... Thats how I learn lol (jump right in)

I just want to make sure i'm getting the process right before I go ahead. I'm running out of time to complete these blades and running out of money on materials from all my failed attempts.

The blades i'm working on atm are the fifth attempt for what should have been one set of knives.
 
Well... They are turning out great so far. Got the small warp out of one pretty easily. With Kevins advice the blades are nice and workable now. My plunge lines turned out great for once. I think it's due to a combination of things, the steel is soft yet not... Easily workable now but it doesnt gouge to quickly if I mess up on the grinder, I also spent the better part of a day rebuilding and upgrading my grinder (like night and day now).
Cleaned off the scale quick and easy and applied the clay. Tomorrow into the heat treat. (Fingers crossed)
 
Ok, that makes more sense now that I realize that you were going to do a sub critical anneal after the austinization and quench.

On hardening the blade you might want to give hot brine a try if you want something faster than the canola oil. It's still a bit nerve racking to do but it creates a more even vapor jacket around the blade which results in more even cooling. If it were me though I would give the canola oil a chance to fail before I went to something as harsh as water or brine.

Doug
 
I personally never mess with water quenches with modern alloys, some old industrial specs show water as an option but that is with much greater cross sections than knife blades, but if one couldn’t get their hands on very fast quench oils I could understand the temptation. Vapor jackets never result in more even cooling since they boil when they collapse and the chaos of a rolling boil is always somewhat non uniform, this is why agitation can be critical to break the vapor jacket and eliminate the boiling effects as much as possible. Adding brine creates vast amounts of nucleate boiling points and actually increases the rate of the jacket collapse rather than having any stabilizing effect, the quicker the jacket is broken up and the liquid can contact the steel, the more uniform the quench.
 
That makes sense! I'm glad I went with oil, the blade came out perfect!
Your earlier recommendation for heating to 1475 then 1300 after normalizing and several 1300 heats. I take it that final step is really only required if needed? Or is there benefit to this... 1475 normalize > 1300 > 1300 > 1300 > 1475 > oil quench > 1300. That's how I ended up normalizing this last batch and it turned out quite nice but did I overkill?
 
I think that most would have done 1500° to dissolve the carbides then to 1400°, then 1300° with air cooling between the heats to refine the grain and then take it back up to 1450-1475° and quench to harden. At least those who have a regulated oven would. The rest of us have to heat treat by the light of a full moon and watch for the decalessance. I doubt that you are doing any harm by repeating the 1300° cycles a few times as you aren't causing any phase changes. Reading Kevin's earlier post he did recommend repeated 1300° cycles to help spherodize the carbides and knowing Kevin's reputation I know that he wouldn't steer you wrong.

Doug
 
What Doug said. The final quench and heat sequence is only necessary of you have done everything else correctly and are still getting dulled tooling from uncuttable steel, which is mostly likely he result of carbide clustering that needs to be brought to heel. Heating to 1475F is a refinement heat cycle but, by definition, not normalizing, which would require temperatures above the upper critical limit to qualify.
 
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