Troy-Bilt Tiller knife project finally underway

[Frosty]

Picker: How closely are you examining the broken faces? Crystal size commonly called "grain" is pretty coarse though even and "relatively" smooth. 

However the one that's only been hardened is significantly different, the crystal size appears to be inconsistent and the faces are uneven across the fracture plane.  Looks like a broken dirt clod so to speak, rather than a broken coffee mug. See what I'm looking at?

When bladesmiths talk about "refining the grain" they are breaking the crystals, crystal boundaries are initiation points for catastrophic failure. Tempering is a controlled softening process that is actually crushing the crystals and boundaries through thermal expansion and freezing them in place by relatively quick cooling. This is NOT quenching. Quenching is chilling steel from critical temperature to below one where carbon and iron molecules can change position. 

I'm not a bladesmith though I know the dance. Perhaps try annealing the blades more than once, even sloppy normalizing helps break the crystal structure down. Heat to critical and wave the blade in cool air, several 3+ times.

Another factor common to new guys that causes excessive grain growth is keeping the steel HOT too long too many times. Don't think you're screwed up, it's normal part of the learning curve. We all spent too much time playing pitty pat when we were getting started. 

Plan out what you want to do and in what order BEFORE the steel goes in the fire, the get with the program when you take it to the anvil. Faster is better, blemishes and not what you wanted profiles are what grinders are for. Also, remember the thinner the steel the faster it heats so the edges are going to be above critical before the spine is hot enough to bend and the tang? Who cares about the tang, it kills me to see people on Forged In Fire putting nearly finished blades in the fire to make the tang!

Isolate, set and forge the tang to a good preform and FORGET IT! Grind it after the blade is finished. 

Anyway, try spending less time in the fire, more time forging faster. Get it close enough and give it a few thermal cycles before annealing. Harden and temper till you find the range THIS steel works well to.

Just don't do it on knives, Why waste all that time and effort experimenting? Instead forge down some test coupons, say 1/8" x 1/2" x 2". Pick A coupon, do your annealing cycles, harden then draw your temper colors from one end and chill it before they run to the other end. This will leave your coupon as quenched at one end and as tempered as you made it at the other.

Place the coupon in the vise with one end protruding, lay a rag over it to act as a scatter shield in case it shatters. Give the protruding end a rap with a hammer, observe and note the effects. Note the results.

Oh, did I forget? Take note of EVERYTHING, heck number the coupons if you're making more than a few. 

None of this will tell you WHAT that steel is but it WILL tell you what YOU can do with it. 

Make sense?

Frosty The Lucky.

[picker77]

Wow. Thanks Frosty, That does make sense. A second and much closer look with a 10x glass DID show some differences I had not noticed at first glance. I think I was incorrectly expecting a dramatically different, easy to see look to "bad" grain in steel, so comparing these two didn't ring any alarms. Another tidbit learned. Lots to think about, I'll take it a step at a time. I think I'll print this out and chew on it while I consider my next series of moves. This will be the third post I've hung on my shop wall, the first two being your PDF on burners, and the second being Steve Sells' clear and simple article on heat treating. Hope things in the Great North are good.

[Irondragon Forge ClayWorks]

You might PM stormcrow here to see if he would tell you his treatment

 

[picker77]

Thanks IFC, already tracked it down, lots of good info. Storm Crow does some absolutely jaw-dropping work. His knives are a sight to see.