8670 heat treat coupon results

Kyle Jones said:
Warren,

I like using the 8670, but I'm puzzled by either the numbers you're getting or what AKS has on their site for heat treating results. They're chart isn't getting anything near what you are. What's the deal with that?

I can't post the picture of the chart, but as quenched at 1600 puts the HRC at barely over 61, then descends rapidly with tempering. Do you think I should ask Chuck where they are getting the info? I'll bet the manufacturer's chart was intended for something other than "knife" blades.

Thanks in advance!
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The charts are inconsistent at times. This steel was designed to be used in saw blades, and the heat treat is optimized for the structures advantageous to sawmill saw blades.

Chuck sent me some of this steel to experiment with as he made a very tough kitchen knife at Rc63, with a really low temper, like 150f. (I’d have to look it up.) I was using a lot of 15n20 for kitchen knives, and I got a couple extra Rc points from the graphs by using 1465f, rather than the 1500 or more often recommended. Chuck likes to tinker with things, and is quite generous with like minded people. I’ve got a few kitchen knives out there now at Rc62/63, and they work as well as the 15n20 knives I’ve made before. Some experimentation for our purposes is required. We want a fine grain structure with tiny carbides, and minimal retained austenite. Bearings and saw blades will do better with larger carbides, and some retained austenite.
 
The chart shown on our website is based on the information from the steel company. It is a chart for sheet, not thicker material.

We've also gotten better results than shown on the chart. I think the numbers released by the steel company are for "the lowest common denominator". In other words, people who are participating in this thread will get better results because they are interested in doing the best heat treatment possible. Someone who heats the blade non-magnetic and quenches in used motor oil will probably not get close to the published numbers.

Chuck
 
I want a thread compiled of all your results and stickied .
My 52100 HT greatly improved by reading posts from Kevin Cashen as well as 2 forum members who have posted in this thread .
Used to quench at 1575 and go into dry ice/acetone. Now i get it harder without needing to cryo
 
We knew that guys like Bob Kramer had nailed the HT for 52100 just like Bob Dozier nailed the HT for D2. What we didn't know until Mr. Cashen and some others started playing and publishing was exactly how to get those results with 52100 consistently and without voodoo.
 
Willie71 said:
So, in summary, I would use 1525-1575f for most consistent results. I only got one reading at Rc66, and that was at 1525f. You basically have a very forgiving steel that will get good results over a 100f Range. With a kiln, set it at 1525f, and go.
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Once this temperature is reached, is there a recommended soak time, or direct to quench?
 
Soak time is done mainly for 2 reasons. 1. Extra carbon past the eutectoid point (soaking with these steels is generally at a lower temp like 1475f)

2. Alloying. Because 8670 has no extra carbon and very little alloying soaking is not necessary. But it does have a little bit of chromium, so if you have good temp control it may help the alloying come into solution.

With that said, I wouldn’t soak it more than 10 minutes. 5 is probably plenty good. If you are using a forge and don’t have tight temp control, just bring to temp throughout and quench.
 
Yes I also agree. The company charts are for the typical customer uses . It may not be best for you. Don't be afraid to experiment .
Quenchants can go bad .Make occasional checks for that. I assume that an 'organic type would have more of the problem .
 
what are you guys using for tempering temps?
the ones on AKS are really low to get decent hardness. im used to seeing 300-400 for temps, but 200F to get 60 HRC is crazy low!
does sub zero/cryo have an effect? though now i think about it, its a simple steel and likely wouldnt really benefit from it.
 
ShannonSteelLabs said:
what are you guys using for tempering temps?
the ones on AKS are really low to get decent hardness. im used to seeing 300-400 for temps, but 200F to get 60 HRC is crazy low!
does sub zero/cryo have an effect? though now i think about it, its a simple steel and likely wouldnt really benefit from it.
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1525f, quench, 350f temper gets Rc60. 200f is about Rc64.
 
Hardness numbers and tempering and hardening temperatures are almost identical to old tool steel type 234(family member 232 is now called L6). Composition is almost the same. ref. Tool Steels by Roberts, 4th ed. copyright 1980 pg 370-78. Mf 95% temperature is 300F, so I doubt cryo would do much. according to old Crucible data, you have 10 seconds to get steel below 800F.
this study has cooling curves of vegetable oils including canola
https://www.researchgate.net/public...erties_of_a_Series_of_Vegetable_Oils/download
the old sailor
 
How long do you guys quench the 8670.
I'm using parks AAA oil.
Had some hardness issues with some previous blades. But all I have is a file. And I think it may be suspiciously hard. I've heat treated 4 knives with the same temp and none hardened to where I would like. (But maybe I'm used to super steels)

I'm running 1525F.
Gonna try heat treating the comp chopper prototype today.
 
ShannonSteelLabs said:
How long do you guys quench the 8670.
I'm using parks AAA oil.
Had some hardness issues with some previous blades. But all I have is a file. And I think it may be suspiciously hard. I've heat treated 4 knives with the same temp and none hardened to where I would like. (But maybe I'm used to super steels)

I'm running 1525F.
Gonna try heat treating the comp chopper prototype today.
Click to expand...

I quench until I can hold it in my bare hand.
 
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