W2 grain size discussion

[PaulDiStefano]

Hey guys, so I figured I would start doing some testing on normalizing then quenching vs. normalizing followed by grain refinement cycles then quenching. I wanted to test the difference between cutting performance on a larger grain vs refined grain.
I do grain refinement cycles on my knives to 1350. The one I left at normalizing temp was 1650 then quenched.
I haven't started testing the two yet. I wanted to ask you guys how much of a difference grain refinement will matter on a bowie. What should I be looking for when I test. Edge retention and sharpness? Should the grain refined knife outperform the other very obviously or will it be very subtle?

I also quenched little pieces of w2 and broke them to see the difference. I lost the refined grain piece but here is the only normalized piece and then quenches at 1440



What can you guys tell me about this grain. I have seen some people only normalize steel and then quench without thermal cycling. Is this grain size acceptable or would it be complete crap?

I would never sell a knife without grain refinement cycles. Just curious what your thoughts are on this grain to further my knowledge
Tell me what you guys think or any personal experiences with testing!
thanks guys!

 

[Russ Andrews]

Normalizing IS grain refinement......Should be several heats...decending from 1650/1625, 1550, 1450(f)......at this point I prefer a quench from an additional heat
at 1460, followed by spherodizing at 1250/1 hour..........this is for forged blades.......after this do your drilling/filing and rough grinding.......followed by final hardening and
tempering.

Your grain is much too large......won't perform well at all.......

 

[PaulDiStefano]

Normalizing IS grain refinement......Should be several heats...decending from 1650/1625, 1550, 1450(f)......at this point I prefer a quench from an additional heat
at 1460, followed by spherodizing at 1250/1 hour..........this is for forged blades.......after this do your drilling/filing and rough grinding.......followed by final hardening and
tempering.

Your grain is much too large......won't perform well at all.......

Oh I always thought normalizing was one high temp to get all the grain to a uniform size and then grain refining was done following right after to reduce the size. Ya I'm curious to see how portly it does. Do you think it will just not get as sharp and therefore not cut as cleanly as the blade with grain refinement cycles

 

[JTknives]

That’s some big grains. It should look like a solid mat gray finish. You should not be able to see the individual grains.

 

[PaulDiStefano]

That’s some big grains. It should look like a solid mat gray finish. You should not be able to see the individual grains.

Haha ya I was actually surprised when I broke it. I didn't think it would be that big. I'm curious to see how much of a difference there is in performance

 

[Larrin]

Normalizing IS grain refinement......Should be several heats...decending from 1650/1625, 1550, 1450(f)......at this point I prefer a quench from an additional heat
at 1460, followed by spherodizing at 1250/1 hour..........this is for forged blades.......after this do your drilling/filing and rough grinding.......followed by final hardening and
tempering.

Your grain is much too large......won't perform well at all.......

I’ve never seen a recommendation for descending temperatures outside of knifemakers and can’t think of a good reason for doing so. Maybe a high temperature normalize followed by lower temperature cycling, but descending temperatures seems odd. Who originated that idea?

 

[PaulDiStefano]

I’ve never seen a recommendation for descending temperatures outside of knifemakers and can’t think of a good reason for doing so. Maybe a high temperature normalize followed by lower temperature cycling, but descending temperatures seems odd. Who originated that idea?

I've always read that it refines the grain size making the edge able to get sharper and last longer. I've always done it but now I've finally decided to actually test the difference out now. I'm curious to see if anyone has a real answer for you. That would be a good read

 

[PaulDiStefano]

Here's another question. If I have two knives. One with smaller grain then the other and both are sharpened to 600 grit. Will one be obviously sharper then the other even though the cutting edge isn't sharpened to a really high grit

 

[Larrin]

Grain size doesn’t really contribute to edge retention except secondarily through toughness improvement if the sharpness is lost through chipping. Grain size also shouldn’t affect sharpness.

 

[Tenebr0s]

I’ve never seen a recommendation for descending temperatures outside of knifemakers and can’t think of a good reason for doing so. Maybe a high temperature normalize followed by lower temperature cycling, but descending temperatures seems odd. Who originated that idea?

Larrin, that's really interesting. For the lower temperature cycling, do you recommend the temperature be the same each time? E.g. do a proper normalization once above Acm, then a couple thermal cycles around A1?

 

[PaulDiStefano]

Grain size doesn’t really contribute to edge retention except secondarily through toughness improvement if the sharpness is lost through chipping. Grain size also shouldn’t affect sharpness.

what the heck!! my life is a lie lol. So what is the reason you should aim for small grain?? Because bigger grain chips more easily and is less tough?

 

[Russ Andrews]

I’ve never seen a recommendation for descending temperatures outside of knifemakers and can’t think of a good reason for doing so. Maybe a high temperature normalize followed by lower temperature cycling, but descending temperatures seems odd. Who originated that idea?

decending normalizing cycles do actually reduce the grain size a little with each cycle. I"ve demo'd this in my shop, and Kevin C. had a thread w/photos
here, some years ago.

 

[JTknives]

1+^
I have seen it in my shop as well.

 

[DevinT]

After putting everything into solution at around 1650f, can you get the same grain size reduction by cycling multiple times from a set temperature?

Hoss

 

[PaulDiStefano]

Normalizing IS grain refinement......Should be several heats...decending from 1650/1625, 1550, 1450(f)......at this point I prefer a quench from an additional heat
at 1460, followed by spherodizing at 1250/1 hour..........this is for forged blades.......after this do your drilling/filing and rough grinding.......followed by final hardening and
tempering.

Your grain is much too large......won't perform well at all.......

Russ if grain size won't affect sharpness like Larrin said, in what way won't the blade perform well. Sharpness was one of the main reasons I thought grain refining was so important. Thanks

 

[JTknives]

Overall blade toughness is affected by grain size

 

[Larrin]

decending normalizing cycles do actually reduce the grain size a little with each cycle. I"ve demo'd this in my shop, and Kevin C. had a thread w/photos
here, some years ago.

I didn’t say it doesn’t work. I said using descending temperatures doesn’t make sense mechanistically to me vs one high temp followed by lower temperature cycling. The first normalize puts (almost) everything in solution and transforms to pearlite plus carbides, so the cementite structure should then be good. But for grain refining I don’t see any reason to do anything but form austenite and cool, at that point higher temperatures would only grow the grain somewhat, the extent to which it did so would be controlled by the heating rate and hold time.

 

[Don Hanson III]

Russ if grain size won't affect sharpness like Larrin said, in what way won't the blade perform well. Sharpness was one of the main reasons I thought grain refining was so important. Thanks

If the steel is tougher because of a finer grain, then the edge will not roll or chip if heat treated properly. With fine grain W2 I can heat treat to a higher Rc hardness and have a very thin edge that performs outstanding.

 

[PaulDiStefano]

If the steel is tougher because of a finer grain, then the edge will not roll or chip if heat treated properly. With fine grain W2 I can heat treat to a higher Rc hardness and have a very thin edge that performs outstanding.

Ohhh, I see. Thanks Don. This thread helped a lot. I'm one step closer to being less of an amateur now haha

 

[kuraki]

I didn’t say it doesn’t work. I said using descending temperatures doesn’t make sense mechanistically to me vs one high temp followed by lower temperature cycling. The first normalize puts (almost) everything in solution and transforms to pearlite plus carbides, so the cementite structure should then be good. But for grain refining I don’t see any reason to do anything but form austenite and cool, at that point higher temperatures would only grow the grain somewhat, the extent to which it did so would be controlled by the heating rate and hold time.

So, for example-

Normalize at ~1600f - cool in still air = pearlite and carbides
Thermal Cycle at ~1460f - cool in still air = refined grain (though my question here is the austenite is formed but if cooled in still air won't it become pearlite again?)
Austenitize at ~1460f - quench?

1 thermal cycle at or around aus temp for grain refinement? Or are multiple beneficial and it's simply the progressive temperature you're taking issue with? Or is it one step further and a pre-quench like Devin is recommending with AEB-L is a grain refinement thermal cycle to harden from?

I'll admit I've broken quenched steel with grain like Paul shows in the OP, where no normalization has been done. But I've only then broken quenched pieces that have been treated with a normalizing and progressively decreasing thermal cycle all together, not at any steps in between.