Unusual auto-hamon formation

[Nate Webb]

My last couple of blades have formed a weird auto-hamon around their periphery. The pictured knife was made from an unknown steel (1920s Ford Model T leaf spring) so it didn't overly surprise me, and indeed the buyer was really happy with it. but then I quenched a nice thin 26C3 nakiri the other day which did the exact same thing, which *is* out of the ordinary in my experience, which has me concerned. The heat treat regimen for the 26C3 is the same as I've always used with good results until now. I wonder if it might be an oil issue? I used the same Parks AAA that I've been using for the last couple of years without issue (I realize AAA is considered a tad slow for 26C3, but it's never been an issue before, and I've made several knives with that steel/oil combo up to now). is it possible the oil might have degraded, and be quenching slower somehow? Not sure how else to explain the results

I appreciate any insight you may have.

Nate

 

[Stacy E. Apelt - Bladesmith]

Mod-T leaf springs were "SAE 6000" steel, which was a chromium alloy steel. I would normally see the hamon you got on a simpler steel, like 1070 buggy springs.

 

[Nate Webb]

Mod-T leaf springs were "SAE 6000" steel, which was a chromium alloy steel. I would normally see the hamon you got on a simpler steel, like 1070 buggy springs.

Oh they were definitely Model T springs. My cousin is a mechanic who specializes in classic cars and we took the springs off the vehicle ourselves

It's the nakiri which really has me stumped though. What could cause that same type of hamon in known 26C3? I've never seen its like.

 

[Stuart Davenport Knives]

Not much help, but maybe a clue....

I have used 26c3 with Parks 50 for a while, and never had an auto hamon. I made a sujihiki a few weeks ago and it had one. I didn't change a THING in my procedure. I'm wondering if there is some 26c3 out there with even lower manganese and/or chromium than in the past. Just a guess.

 

[Nate Webb]

Not much help, but maybe a clue....

I have used 26c3 with Parks 50 for a while, and never had an auto hamon. I made a sujihiki a few weeks ago and it had one. I didn't change a THING in my procedure. I'm wondering if there is some 26c3 out there with even lower manganese and/or chromium than in the past. Just a guess.

Hmmm, interesting it's certainly possible I suppose. I believe this bar was sourced from Pop's a few years ago, but it's been long enough that I couldn't swear to it.

 

[DevinT]

Use parks 50 or normalize first. If you have pearlite condition before heat treating (prior condition) you should be fine.

Hoss