115crv3?

[Aiden CC]

I recently decided to try out this steel, sometimes referred to as "silver steel," for some puukkos and I've had some problems with cracking. There isn't too much info (at least that I can find) about heat treating it, so I figured I would see if anyone has used it or has any insights. Here is the process based on what I have been able to find and my results so far:

 

-Forge to shape

-Normalize once "by eye" in the forge, air cool (well, technically in sand but just the tip to hold the blade upright)

-Grind to 60 grit (maybe this is too coarse? These knives are zero ground so I go back to 60 after ht anyways so it feels like a waste to go higher if it isn't necessary)

-5 Minutes at 1475 F, air cool

-5 Minutes at 1425 F, air cool 

-Austenize 10 minutes at 1475 F

-Interrupted quench with water and canola oil (6 blades, 1 cracked 1 warped and cracked in straightening during second temper, all had some "sori")

-Canola oil quench (1 blade, cracked but didn't open due to less distortion and only showed up during grinding)

-Temper 375 F twice for two hours

 

For reference, here's the steel's composition:

 

C:                  Mn:                Si:                   P:          S:          Cr:           Ni:    V:               Mo:    W:

1.10 - 1.25    0.20 - 0.40    0.15 - 0.30    <0.03    <0.03    0.5 - 0.8    -    0.07 - 0.12   -         -  

 

I ordered some Parks 50 to try, which may help as well. Thanks for looking and any insights/suggestions are appreciated!

[Gary LT]

Aiden, I also have wanted to try silver steel.  I used to use O1 in 9/16” round and would do round silver steel as well. (I realize it’s not the same stuff but as example)
But I would not grind at 60 grit, too rough, IMO, and certainly would not quench in water even interrupted, (but others might.) Using oil, canola should be warm, (at least 110F). I do full blade quench, (point first, at an angle) and never a crack or warp.

What temperature are you forging at and are you reheating often enough? I have a tendency to keep hammering…
Gary LT

Edited December 2, 2021 by Gary LT
Wording

[Jerrod Miller]

I would recommend grinding to a finer finish for better results during heat treat.  I would say a 220 minimum to be safe, but 120 may be enough.  You also have some decent carbide formers there, so I would recommend a normalization cycle going quite a bit hotter, like even 1600F.  And just hold onto the blade for the normalization.  It takes about a minute to cool from high temp to black.  Be patient and watch it while holding it.  I would then normalize again at a lower temp before grinding.  Then grind, normalize another time or 2, then harden.  I'd also start with a straight canola quench and see if that gets you the results you are looking for.  If not then you can move to something more aggressive (or less if needed).  And anything that has the potential for a pretty fair amount of retained austenite should get 2 complete tempers before starting to try correcting warps.  

[Doug Lester]

My sympathy on the crack.  Nothing breaks your heart like grinding you blade and thinking that it is coming along fine just to move up to a finer grit and seeing that the blade has cracked.  Not that has ever happened to me.

 

Doug

[Aiden CC]

Thanks everyone!

 

Gary, some of the blades were briefly at a welding heat when I forged welded a mild steel tip onto the tang, but I think I had pretty good temperature control after that. Last few heats were lower but only for straightening before normalizing. 

Here is the grain in the break. The dark section is oil that got into a crack in the quench, it's hard to see in the photo, but it isn't oxide from being open at temperature, it has a wet appearance and slowly spread over time.

 

Jerrod, I'll try out normalizing in a furnace instead of the forge to make sure I get a higher temperature and go up to a higher finish before hardening. Also I'll delay straightening until after a second temper. Does retained austenite act differently in the small volume fractions in high carbon martensitic steels than it does in something like TRIP/QP steels? It seems like it can increase ductility to a certain extent, right? 

 

Doug, that's quite true. I had another crack show up in the hand sanding stage for one of these after I had fit a handle etc which was quite unfortunate. 

 

I have a bit more of this steel on hand and some more on the way, so I hope to have some redemption with a second batch of these.

[Jerrod Miller]

Retained austenite can increase ductility, but after your first temper cycle some of that austenite has converted to un-tempered martensite, which is the problem that the second temper is there to solve.  

[Aiden CC]

That makes sense about straightening and the second temper, thanks Jerrod. It's possible I've gotten away with it in the past because I've mostly been doing minor adjustments to thinner knives, primarily in 80crv2. 

 

I had hoped to make a new batch of knives with this steel and try out the suggested changes, but it may have to wait a bit. If I remember I'll post the results here.