Too fine grained

Cody Hofsommer

Cody Hofsommer

Joined
Dec 2, 2011
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I have been thinking of his for some time. It is possible to refine the grain of the steel too much, right?. Is this a worry, under normal circumstances? I usually thermo cycle 3 times, about 1650, 1550, 1450 degrees. Judging the temp by color, I'm close but I'm sure there is some error in temp. I have tested and broke pieces several times and seen major reduction in grain size. Most of my knives are Damascus that I forge, I thermo cycle, grind, but I'm unsure what I should do to releave the stress from grinding, before hardening. Just normalize it again? Once? Three times? Soak at 1250 for a while?

What say you? Any help or clarification is appreciated.
Thanks
Cody
 
The minimum fineness of the grain is determined by the size of the atoms in the mix, and how they are combined. It isn't really possible to have too fine a grain.
 
Thanks Stacy, that make sense. So there would be no harm to thermocycle it again? But would a 1250 soak do as good? Or better because less time at high heat?
 
Cody, you do not say what your damascus mix is. If it is the standard 15N20 and 1084 or 1080, a post grinding stress relief cycle is fine. I would suggest a soak at 1200-1250 for an hour then air cool, would be fine. Actually you can get the grain so fine that you will have problems with effectively hardening the blade.
Brion
 
BRTATCK said:
Actually you can get the grain so fine that you will have problems with effectively hardening the blade.
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Not with the heat treat equipment that most knifemakers posess... especially when judging temperature by eye. I wouldn't be giving it a second thought, bud.:thumbup:
 
Thanks for the response Rick. I have a evenheat, so the 1200 soak, pull them out to cool while the oven gets to temp for hardening, should work well for me.

Just tring to do the best I can, with the material, equipment, and knowledge that I have. I guess the knowledge is the cheapest to acquire, although maybe not the easiest.

Thanks everyone for takin the time to help me out.
 
Much of the difference is if you go above the transformation line .The subcritical anneal doesn't have that problem.
The triple normalizing is enough .After 3 times you may reduce the grain size so much as to change the hardenability !!
 
mete said:
After 3 times you may reduce the grain size so much as to change the hardenability !!
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I apologize for the thread-drift, and I'm not arguing... I'm just interested. I do not understand how/why minimum grain would have that effect. Could you explain please?
 
james terrio said:
I apologize for the thread-drift, and I'm not arguing... I'm just interested. I do not understand how/why minimum grain would have that effect. Could you explain please?
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The finer the grain, the lower the hardenability. I don't know why, but I have experienced this with shallow hardening steel like W2. For me it took more than 3 normalizing cycles though, more like 6 or 8.

Cody, I just do a normalizing cycle after grinding. Up to around 1400f and air cool. Works for me.
A one hour soak at 1250 will do good as a stress relief also.
 
I am with Brion. With an Evenheat, and especially with pattern welded steel if you want an even etch, you could definitely get it to the point where it won't through harden.
 
I have never had this happen with W2, but I did have it happen with a piece of 1084 that i was playing with to try to make a JS performance test knife. Combination of normllzing it way too many times and clay quenching made for a knife that didn't really harden very well at the edge. Another area where I have heard that you can have different ype of problems is trying ot do the "kitty litter" anneal on hypereutectoid steels. Kevin Cashen says that there are just too many things that you can mess us doing that that you don't have with stuff like 1050 or 5160.
 
With hyper-eutectiod steels ( 52100 and W-2) it is possible to get the grain very small and effect hardenability. With the proper cycling and preparatory HT, it isn't usually a problem. The only problem I am aware of is Aldo's 52100 which comes as a very fine grain steel. If you cycle it too much, you can make it so it doesn't want to harden past Rc56. This isn't a usual problem, and can be solved by a quench form 1600F in the first cycle.
 
Well, I learned something new. I didn't think you could refine grain enough(using simple means) to effect hardenability. I take it, this is exclussive to hypereutectoid?
 
Yeah, I think Verhoeven has some information in it when he reduced the grain size of 5150 to a 13 or 14. It would still harden better than the 1084 he was using, but it was noticable, at least by him for the book.
 
I also had problems with W2. I did 5-7 reducing temp normalizing and it would not harden, at least to my desires. That and the Hamon sucked.. I now do 2 lower temp noramlizing and have great success. Glad to hear that others have had the same experience. It was not until I called Don that the light-bulb went off.

Thanks Don:D
 
mete said:
Much of the difference is if you go above the transformation line .The subcritical anneal doesn't have that problem.
The triple normalizing is enough .After 3 times you may reduce the grain size so much as to change the hardenability !!
Click to expand...

Although there are other problems that might occur, could you overcome the hardenability issue with a faster quenchant?
 
Yes you might be able to do that but other complications may occur .Just stop at three. Your properties won't improve that much with finer grain.
 
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