Not your average S35VN heat treat question

S

spareparts

Joined
May 12, 2010
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303
I made some paring knives and small utility knives out of S35VN, for which I plan to send to a pro for heat treat. I had a scrap left over so I went ahead and ground a small paring knife out of it with a little stick tang to experiment with.

I heat treated it in my backyard propane forge. Triple normalized, soaking it for about 10 mins each time. Then soaked for about 15 mins and quenched in canola. Tempered for two hours at 400F, LN quench for about 4 hours, then final temper at 400F for two hours.

Going by the color charts I found online, I'm pretture sure it was over 1800F but below 1900F. Crucible only lists hardnesses for 1900F and up. Question-will the hardness on this blade be high enough to be considered a knife?

It's just for practice so I don't mind if it's in the mid 50's HRC but if I didn't achieve that then might as well give it to the nephew to dig in the dirt.
 
Your only way of knowing will be to test it. If you see edge rolling in heavier use, you didn't acheive high enough hardness. If you see edge chipping, it's likely that you experienced significant grain growth through over-heating in the forge. Judging temperature by color for long-soaking complex alloys, especially high-heat alloys is a very difficult task and requires a lot of experience to get right, and even then, experienced smiths will use an oven to harden stainless steels. Colors look different to different people, and your ambient lighting also impacts the true color of the steel. I'd be suprised if you got the heat treatment close, but it's fun to try.

BTW, for the vast majority of bar stock (I'm assuming stock removal here), there is little need to normalize, and doing so three times at the same temperature for 10 minutes is really just intruducing the possibility for more errors. After forging, many do what is often called heat cycles which include a normalizing heat, and several subsequently lower heats below non-magnetic to refine grain. However, modern bar stock comes in a very nice annealed form ready for heat treating in most cases.

--nathan
 
Thanks for the input! This is exactly why I decided to screw around with it, so I could learn something new from some otherwise scrap steel.
 
If the blade was not wrapped in a sealed foil packet, after all that time it is probably pretty bad. The chances of it being very hard or holding an edge well is very, very, low.
 
Thanks, Stacy. I'll screw around with it a little more for kicks and pass it along to a youngster to stab dirt and throw at trees.
 
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