Hardness test results for 8670M

Phillip Patton

Phillip Patton

Knifemaker / Craftsman / Service Provider
Joined
Jul 25, 2005
Messages
5,380
Hi guys,
Matt Bailey (Bailey Knives) asked me for my take on Admiral's 8670. I volunteered to do some heat treating and hardness testing for him (and to satisfy my own curiosity) since I have never seen any such data for this particular steel. Here's what I have so far:

The sample is 1.5" wide, 4" long, by whatever thickness they sell it in. I austenitized it at 1525 degrees F for between 10 and 15 minutes. I quenched it in Parks #50 (fast oil) until it stopped smoking. Since this wasn't a knife and I wasn't concerned about warping, I didn't do the interrupted quench that I usually do. I also wanted to eliminate the extra variable that auto-tempering might introduce...

It was late at night, and I didn't have time to wait for the Evenheat to cool down, so I "flash" tempered it at 300 F in my moms oven for a couple hours. I didn't check the hardness before doing the "flash" temper, so keep in mind, the first reading I took was after the 300 F temper. I don't know what the as quenched hardness was.

I took pictures showing where I tested, and how hard it was.

Tempered at 300 F:
firsttemper.JPG


I decided to temper it 25 degree increments, for 1.5 hours each time.

325 F:

secondtemper.JPG


350 F:

thirdtemper.JPG


375 F:

fourthtemper.JPG




Right now it's tempering at 400 F Since this isn't a blade, and I won't be chopping with it, I'll go ahead and temper all the way up to 500 degrees F.

Thanks for your attention. :D More to come tomorrow, and maybe tonight.
 
Thanks for all the work. I didnt realize how much work it was going to be when I asked you to take on this challenge.
 
Thanks for the test results. Back in Feb and March, I was hunting down information on 8670m. One of the things that caught my attention was the austinizing temperature was listed at 1550-1630F. This was a spec sheet from the producer. 1525F is pretty close, but you may not have gotten everything in solution.

Ken
 
Best not to put a tester indenter on the steel before temper anyway. Be a shame to have it explode in your face. Your test after snap temper looks pretty good to me. Smoother the surface the more reliable the reading. (Don't tell anyone but I usually test at about 120 grit.)

rlinger
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IronWolf said:
Thanks for the test results. Back in Feb and March, I was hunting down information on 8670m. One of the things that caught my attention was the austinizing temperature was listed at 1550-1630F. This was a spec sheet from the producer. 1525F is pretty close, but you may not have gotten everything in solution.

Ken
Click to expand...

Hi Ken,
One of my metallurgy books has heat treating info for 8660, which you would think would be pretty close to 8670, and it lists the austenitizing temp range as 1475-1550. Not sure who to believe now. :rolleyes: It would be interesting to harden a sample in the range you're saying, see if the hardness is higher, and break it to see how fine the grain is.
 
425 F:

sixthtemper.JPG


The sample didn't show any tempering color until the 425 temper.
 
So, if you're tempering it at close to 500 degrees and it's still harder than a Chris Reeve one piece knife(a good knife, by the way), is it safe to say it'll make a good blade?
 
Danbo said:
So, if you're tempering it at close to 500 degrees and it's still harder than a Chris Reeve one piece knife(a good knife, by the way), is it safe to say it'll make a good blade?
Click to expand...

In my opinion, no. When I was experimenting with this stuff, I had problems with the edge wrinkling and deforming, even at 60 RC. But then, I have the same problem with L6.... I've pretty much decided to stick with hyper-eutectiods for my knives; in my experience they hold up better.
 
Hey guys,
Finally got around to doing the last temper, for what it's worth:

500 degrees F:

ninthtemper.JPG
 
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