Quench for O1

C

cgdavid

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Sep 12, 2005
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Read through several past threads trying to determine what to try for quenching O1. The most often mentioned are Texaco A, McMaster Carr slow and, Brownell's tough quench. Along with the commercial stuff, ATF, peanut oil, olive oil etc were mentioned.

What I've tried so far is atf @ 140deg with what I consider decent success. What I'm hoping for is some kind of idea as to what will improve - if possible - what I'm getting from atf.

All of my blades are being used as slicers - not choppers so toughness is down on the scale from edge-retaining characteristics. I do a classic heat to a little past critical, plunge into warm atf until at temperature of the quenchant, wipe off oil and put in an oven at 380deg for 3 - two hour cycles.

If the answer is out there somewhere, I'd appeciate a link to it otherwise I'm open to recommendations and procedures.

Thanks ....Curt
 
I'm no expert on O-1, or any steel for that matter! But what I'd suggest is to try several quenchants, and test the blades for cut, toughness, ect, and see what works best for you. I know it's kinda tough to destroy a knife you've put so much effort into, but it's the only way to realy be assured of your product and it can even be kinda fun and addictive.
 
O1 hardens very well, easily and deeply, so your quenchant does not have to be the fastest, this would allow you to focus on other characteristics, like vapor points and stability. If you know it will get hard it is nice to know it will stay straight.

If you are mainly concerned with slicing and edge holding, the quench is a much lesser concern with this alloy than nailing the heating before the quench. Soak it for a good 5 minutes or more at a constant temp and this steel will blow you socks off for edge holding. If you nail the soak 380F temper will not even begin to soften O1.

Also remember that critical temp varies from steel to steel, in fact critical temp is such a relative term that it can be quite confusing. Some put critical temp at the Currie point (nonmagnetic) which is 1414F for ferrous metals, which make the magnet not as fool proof as some believe. Do the magnet check while cooling and watch the color shift (a direct indication of transformation) and see how far off things can be. But on a rising heat, proper soak temp for O1 would be around 65-70 degrees above non magnetic, holding it there long enough for good solution is the trick.
 
I make a bunch of little blades from O-1 for a neighbor/test monkey :) . I hardened them in the Mc Master slow. When he used blades that were tempered at anything less than 425 the blades would chip and get the tips snapped off.
 
Thanks!

Gives me a good direction to follow. What I have to do now is to figure out how to hold the temp for a 5 minute soak in a propane forge.

One thing I am suprised about is that 380deg is not high enough to draw back the hardness. It gave me the 'straw' color at the edge and while I've not used these blades for any chopping, they seem to hold a decent edge and don't seem to chip. May need to check my temperatures with a different thermometer.

Curt
 
Ive found the same for O-1....i need to temper at 425 at least before it will soften a bit. Below that and I get chipping under heavy chops with a thin edge. O-1 hardens like crazy. I wish it were a bit cheaper!

I use 120-130 degree veggie oil straight from the supermarket off the stove and have never had any problems.
 
Mark Williams said:
I make a bunch of little blades from O-1 for a neighbor/test monkey :) . I hardened them in the Mc Master slow. When he used blades that were tempered at anything less than 425 the blades would chip and get the tips snapped off.
Click to expand...

I hear that!:D I just finished knife number 7 as far as experimenting with O1 is concerned. I found exactly what you said. 425F works best so far. Even 420F wasn't satisfactory. I did the last 2 at 425F and I'll do one more for confirmation and I think I'll be satisfied with the results if they're consistent. The fine edge just kept chipping below 425F. I've been using canola oil for quenchant. I had a blade tested in front of me and they came out to around 59ish-60ish HRC on average from 5 points along the edge. I've done numerous tests such as malleting my blade through a 2 x 4, cutting strips of cardboard etc with great edge retention results.
Mike
 
cgdavid said:
...One thing I am suprised about is that 380deg is not high enough to draw back the hardness...
Click to expand...

Soak, Soak, Soak. Go ahead and check your thermometers, one can't be too accurate, but if you only heat to say 1450F and then immediately quench, it would make sense that you do not need to go very high in the temper to avoid chipping, there is plenty of leftover stuff that was not fully dissolved. This is not specific to O1. Before I used extended soaks at constant temps, 400F. would work for any of the steels I used, but when I started getting more complete solution in my austenitizing, 400F was just the starting point, more of a flash temper that I would do before it was time to really temper the stuff.

For years I have heard of folks who taught a 375F temper, this is barely enough to stabilize the BCT to BCC condition (remove the high stress factors) and one shouldn't see less than 63.5HRC in almost any high carbon steel with this. The only explaination of such low tempers being succesful is that maximum hardness based upon carbon solution was not achieved to begin with.

It is one of those cases of having a pretty hard sell to folks who have made serviceable knives, but the proof is in those temperatures. A blade that tempers out entirely at 375F did not have much trapped carbon to diffuse, but one that needs to go to 440F just to get to 59 HRC obviously had a lot of carbon locked up in the martensite. Hardness based just upon stress induced dislocations in the lattice (strain), will soften fairly quickly as temps rise, but trapped carbon needs higher temps to diffuse. One could theoretically get this by insufficient soak and then quenching into water. Initial rockwell could be very high, making it very hard to tell the guy he didn't get enough carbon in solution, but the strain in that steel will be very quickly removed with heat. A blade that achieved good solution and quenched in water (first of all it would most likely be blown apart, another tell tale sign of how many makers get total solution), would see only a minor change below 400F and would then hold on to its carbon based hardness fervently, forcing one to go much higher to lower the rockwell.
 
this brings up a few more questions...
Does the ramp up time to the soak temperature play into the equation?

What is used to accurately test temperatures that high? My tempering oven is easily measured but 1400+ deg in a forge is a bit more of a challenge.


Thanks all....Curt
 
You guys that had a problem with chipping, do you double temper? I do my O1 blades at 400 twice, two hours each time and have had excellent results. No chipping problems.
Scott
 
same as tik tok... maybe our edge geometry is different. I go for around 20 degreesish usually depending on use. In this case I had gone ahead with 20 degrees give or take.
 
I am sure that the soak point is correct. its difficult to get a 5-10 minute soak in a propane-driven forge without overheating some part of the blade. Maybe I am just not good enough! Do many makers do full length soaks in a convection heated forge like a typical venturi burner gives? How do you maintain a 1450 degree internal temp without a pyrometer and controller, beyond playing with a regulator? My propane forge does not have a pyrometer since I rely mostly on magnetism to designate the edge of critical, then I just bring it a little hotter....
 
Same questions as TicTock....

How do we get steady temps from a venturi burner/propane forge?
How do we measure temps that high?

I'm willing to bet that it involves an electic oven rather than a gas burner.

Thanks...Curt
 
Over the last couple of years using the same steel, I have found that the more efficient my heat treating becomes (industrial quench oils, temp controlled ovens for quenching, soaking etc), the higher I have to ramp the tempering temperature to get the same temper hardness. I now temper as much as 70 degrees higher than I used to.
 
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