The Damasteel Got Here !!!!

if it's worth anything Roger I use 425 - 430 deg F
(the way I heat treat)
just my thoughts but I'm thinking you'll have better edge retention
and a little easier re-sharpening with the temper before cryo
at about 59 - 60 Rockwell harder isn't ways better as you know..

but for testing purposes I'd keep the same 450 F , 2 hours for comparing at least
just 2 cents..:)
 
Roger , I would try a 1 hour 350 F snap temper. There are a number of variables here that change the risk. The snap temper ,of course ,stabilizes the austenite which resists transformation and therefore reduces hardness. Then there is the cryo ( in the old days we called it sub-zero quench ) ,how low a temperature and how fast you get there. Do you put it directly into cold liquid or into the gas ( n2 etc ) above the liquid . Also the condition of the blade before quenching .In the end your procedures and equipment and experience will tell you the limits. When it goes 'ping' back off.LOL Again when you temper or cryo do it immediately.
 
I'm reading you load and clear Dan but for now it's the process of elimination. When Mete gets back about his minimum snap temperature I will plan a test using that and may drop the temper down to 400 too to see how high this puppy can go with the same soak temp. and times (assuming the grain still looks good).

RL
 
Mete, "which resists transformation"; bingo - yet another thing you have taught me. Thanks !!!

I will do one with your snap temp.(350) / snap time (1 hr). I think I would like to drop the tempers down close to 400 F.. What about that with you ?? I'd like to get this steel above 60 HRc and have proper grain structure while being able to temper before cryo. I remain having a problrm understanding how a plate quench is going to work well on a distal taper but for these testings I will stay with the aluminum plates quench.

I lower the steel into the liquid nitrogen. I go as reasonably quickly as I can without causing the liquid to boil out onto my hand.

I always temper and/or cryo immediately and always have the temper oven pre-heated before hand.

No pings yet but I know it is a bad sound to behold.

RL, and thanks
 
Heat Treat Sample #6B:

The same as #6 except with a temper before deep cryo.
-----------------------

(0.75 X 1.5 X 0.138 inch RWL-34, foil wrapped and placed in cool oven)

Ramp to equalize

1400 F. / soak 7 minutes

Ramp to target

1950 F. / soak 25 minutes

Aluminum plate quench

Temper immediately: 450 F. / 2 hours

Deep cryo: 18 hours

Temper after still air warming to room temp.: 2 hours

Temper: 2 hours
------------------------
Rockwell after temper before cryo: 58 HRc
Rockwell after first temper AFTER cryo: 58 HRc
Rockwell after final temper: 58 HRc
------------------------

Fracture Picture: http://riflestocks.tripod.com/steelgrain6.html

RL
 
Dan, I have not on any of these test pieces Rockwelled as quenched or after cryo before a temper. My thoughts of this, right or not, is that I did not want to put such pressures on un-tempered martensite because of fear it might cause fracturing and show up in the intentional breaks. I thought had that happened it might cause me to take a false fork in the road as to where to go next on the target temp., soak, or other. I also practice this when HT'ing a real blade although on test pieces of stainless before this thread I have Rockwelled as quenched but that answers nothing for the RWL-34.

RL
 
just wondering Roger,,
because if it were right at 58 Rockwell(which it shouldn't be)
the 450 temper would prove inconclusive, I'd think.
 
Dan, if I had to guess at it I would think 'as quenched' at about minimum 61 to 62 and after a deep cryo without a temper at about 3 to 4 points higher. I base that guess only on some ATS-34 tests I had previously done. I am also guessing, and now want to do a cross test, ATS-34 will turn out 1 to 1.5 point lower using these same HT's. I want Mete's opinion on this because the analysis I've seen shows RWL-34 has a slight amount of vanadium in it. This is vacant in ATS-34 and Mete might also explain that the manufacturing process is more responsible but I since from my ATS-34 work this steel for our purposes is superior to ATS-34 significantly or modestly.

RL
 
Roger, you might rewrite that last sentence so that I can understand it. The amount of vanadium in RWL-34 (.2% ) is there for grain refinement....Btw I think you could reduce the cryo time also but that's for the next chapter.
 
Mete, never mind the last sentence for now. It has nothing to do with what we are doing at the moment.

I am getting ready to put the 'snap temper' piece in cryo. How long in deep cryo do you suggest??

Have you looked at the pic of #6B grain, posted this evening?? I need to know what you think.

Thanks. Roger
 
#7:

Same as #6B except snap temper at 350 F. / 1 hour before cryo and will be tempered at 400 F. instead of 450 F..

After snap temper: 59 HRc

In cryo now.

I abandoned the #6 series nominclature on this one because tempering temperatures have been altered for the express purpose of acheiving a different hardness instead of just comparing the results of different quench methods and tempering before cryo or not.

RL
 
Roger, 12 hours cryo would be more than enough. The 6B fracture looks ok. The photo looses some clarity when posting though it looks like you were holding the samples with your fingers ?
 
Dan, excellent.

I'll be taking pictures of the #7 break in a few minutes and post. It looks okay to me but that doesn't mean a lot yet.

RL
 
Heat Treat Sample #7:
-----------------------

(0.75 X 1.5 X 0.138 inch RWL-34, foil wrapped and placed in cool oven)

Ramp to equalize

1400 F. / soak 7 minutes

Ramp to target

1950 F. / soak 25 minutes

Aluminum plate quench

Snap temper immediately: 350 F. / 1 hour

Deep cryo: 13 hours

Temper after still air warming to room temp.: 400 F. / 2 hours

Temper: 400 F. / 2 hours
------------------------
Rockwell after snap temper before cryo: 59 HRc
Rockwell after deep cryo: 61.5 HRc
Rockwell after first temper: 61 HRc
Rockwell after final temper: 60.5 HRc
------------------------

Fracture Picture: http://riflestocks.tripod.com/steelgrain7.html

RL
 
Roger , that looks ok and you got the hardness up.QED as they used to say in math class -the 450 F stabilized the retained austenite too much to permit obtaining full hardness .The 350 F after the Al quench will reduce cracking in the cold but permits full hardness. The only question now is will the Al quench be ok on a ground blade where the bevel may not contact the Al.
 
My grandfather used to get on me all the time for not using my head for anything other than a hat rack, as he put it. Common horse sense tells me no, it will not. A couple or a few others here say yes it does and Kit grinds after quench - so yes it should be great for him. I have not tried it and will not, as just an experiment, on one of my blades because it takes me too long to grind a good blade. I may just simply grind a double sided bevel on a short piece to use as a test piece for that.

On a tapered tang, full-v flat grind all you really have for the plates to contact is the area of ricasso, as I see it anyhow.

How about I do a #7 again with air quench ? The previous air quench comparison got me the same hardness as al plate quench but the fracture didn't look as good. Those were without temper before cryo.

What think, please ?

RL
 
Keep 'em coming Roger.

BTW I hate to make more work for you, but I'm still interested in warm oil quench. Like the data sheets, I'm got an extra point or 2 that way.

Mete, sorry to ask in the middle of this thread, but I think it's related ....

Given that cryo converts more austenite into martensite. Does that mean that the extra hardness in oil quench is because of the same effect (better conversion)? Therefore, the cryo doesn't have the same impact on oil quenched vs. air quenched?

In other words, Roger went from 59 to 61.5 after cyro. If he had used an oil quench, then is it possible it would have been 61 to 61.5? And the resulting internal structure would be the same?



Steve
 
Steve, my guess (without doing a cross test using oil quench) is that the al plates beat the crap out of oil. It was unbelievable to me how increadibly quick the plates brought that small piece of steel to PLAIN cold - not cool - cold. I actually believe I got it way too cool before temper. It is super fast. The fact I got in a previous cross test here the same hardness with air quench leaves me to believe I prefer oil quench because it will contact all surfaces of a beveled and tapered blade and the bottom temperature before placing in temper can be controlled - but only if I can figure a way to get the steel in there quick enough without fumbling around with foil. I emailed you a couple days back about an idea and still want to try that.

RL
 
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