Steel testing underway...

LRB said:
Considering that all of the HT work may not be up to the max results, what has he proven?
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It's worth pointing out that I'm only suspicious about 1 of the test blades, which was one that was heat-treated in a forge. All the others were heat-treated using an Evenheat kiln, and I have no reason to believe that they were bad. I'll be verifying this by getting them hardness tested, but only really because I want to be doubly sure.
 
Don Nguyen said:
I remember encouraging you not to test out so many types of steels and to focus on a smaller group for simplicity's sake, but you've proven me wrong with these tests. Really well done man.
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Thanks mate! It was actually perfectly manageable, I feel like I could test up to about 10 samples at once and it would be ok. Next time I might get all the samples hardness tested before starting the test, just to make sure that I'm not working with dodgy samples, but apart from that I'm pretty happy with how things went!
 
Never said the HT may be bad, but just that it may not be optimal, and I still stand by that. Examples being the A-2 and 01. If your HT doesn't get the best out of each sample, what does the testing actually show? Even if all are at their best, some steels do some things better than others, just as certain blade design performance will vary. Just my thoughts on the matter. If you enjoy what you're doing, go for it, but don't bet that the results necessarily mean a lot.
 
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LRB said:
Never said the HT may be bad, but implied it may not be optimal, and I still stand by that. Examples being the A-2 and 01.
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Ah gotcha!

Well if you have suggestions (particularly for the A2) I'd love to hear them! I'll be doing a bunch more testing with different heat-treats on A2 blades this week. I should be receiving 9 feet of A2 tomorrow so I can get started making the rest of the test blades.

My plans right now for the A2 are:

First up, test that A2 is ok with getting cryo-treated before the first temper. Ideally I would do the cryo before the first temper as A2 tends to have a lot of retained austenite, but if the stresses are too much for the blade I will have to do cryo after the first temper. I think it sould likely be fine...

All blades:
  • Preheat to 1100ºF, equalize
  • Ramp to 1775ºF, hold for 35 minutes
  • Quench in air to below room temperature
  • Cryo-quench into dry-ice & isopropanol for 2 hours

Then for individual blades (each blade tempered twice, 2 hours each time):
  • Temper 1 blade at 360ºF (Aim hardness 63HRC)
  • Temper 1 blade at 400ºF (Aim hardness 62HRC)
  • Temper 1 blade at 500ºF (Aim 59HRC, first toughness peak)
  • Temper 1 blade at 1000ºF (Aim 56HRC, second toughness peak)


NOTE: All these hardness numbers will likely be lower than the actual hardness, as these numbers are taken from a chart that documents testing from heat-treats that did not include cryo-quenching, which should add somewhere between 1-3 points HRC. I will be getting all the blades hardness tested.

Any suggestions/constructive criticisms greatly welcomed!
 
Lone Fortress said:
Stainless steels are best Ht in atmospheric purged enviroments, but still a very interesting thread.
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I've been wondering whether I might be able to get a tank of nitrogen in the shop to purge foil envelopes for exactly that reason. I have to do a bit more research on that first. That being said plenty of makers have had great success heat-treating using stainless tool wrap instead of an inert atmosphere. Sometimes a piece of paper is placed inside the tool wrap, it burns up and consumes any oxygen before the blade gets hot enough to start scaling...

I have to experiment with all that stuff more though as it's all still new to me.
 
This thread is running now. I have only done a few of A-2, and have not tried this, but advice doesn't get much better than that from Roman Landes


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01-06-2013, 08:06 AM #11


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Troop





Troop is online now KnifeMaker / Craftsman / Service Provider


Join Date:Oct 2006Posts:2,821




Here is the HT recommended to me by Roman Landes for A-2.
Note where it says "Heat at a rate not exceeding 400 F per hour." To get maximum performance of A-2, I've found that directive to be a must.
For whatever it's worth, Joe Szilaski also advised me that all HT operations involving A-2 must be done with a slow ramp.
Thank you to Alpha Knife Supply for the link.

http://www.alphaknifesupply.com/Pict...DS-Latrobe.pdf
 
LRB said:
This thread is running now. I have only done a few of A-2, and have not tried this, but advice doesn't get much better than that from Roman Landes


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01-06-2013, 08:06 AM #11


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Troop





Troop is online now KnifeMaker / Craftsman / Service Provider


Join Date:Oct 2006Posts:2,821




Here is the HT recommended to me by Roman Landes for A-2.
Note where it says "Heat at a rate not exceeding 400 F per hour." To get maximum performance of A-2, I've found that directive to be a must.
For whatever it's worth, Joe Szilaski also advised me that all HT operations involving A-2 must be done with a slow ramp.
Thank you to Alpha Knife Supply for the link.

http://www.alphaknifesupply.com/Pict...DS-Latrobe.pdf
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Thanks for the response LRB, interesting advice! I'll have a look around, I certainly don't see how ramping slowly would hurt, and I have a kiln that's capable of doing it so I probably will.

Do you guys think I should start a separate thread for the A2 tests? Or would you prefer they stay here?
 
Might I also add, and this may have been pointed out already, but quenching the air hardening steels in oil isn't prime. Neither is a "Cryo" with dry ice and alcohol. For future tests on air hardening steels, I would suggest using quench plates and proper liquid nitrogen cryo, which gets colder than dry ice. Regardless, it was very interesting.
 
I was thinking of plumbing argon from my TIG into the kiln I'm building. I don't know if it would be worth the trouble.
 
jawilder said:
Might I also add, and this may have been pointed out already, but quenching the air hardening steels in oil isn't prime. Neither is a "Cryo" with dry ice and alcohol. For future tests on air hardening steels, I would suggest using quench plates and proper liquid nitrogen cryo, which gets colder than dry ice. Regardless, it was very interesting.
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Hey mate, the CPM154 is actually recommended to be an oil quench (Crucible recommends that), that was the only air-hardening steel that was oil quenched. This recommendation is present in the datasheet for CPM154.

Crucible also recommend using dry ice for the cryo treatment. I talked to them and they said that doing a liquid nitrogen quench wouldn't do much more than the dry ice, and the dry ice is what's recommended in their datasheets whenever a cryo quench is specified...
 
Willie71 said:
I was thinking of plumbing argon from my TIG into the kiln I'm building. I don't know if it would be worth the trouble.
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That would be nice! Apparently nitrogen is fine too, and supposed to me much cheaper... Never messed with either though so I can't really comment.
 
aarongough said:
Crucible also recommend using dry ice for the cryo treatment. I talked to them and they said that doing a liquid nitrogen quench wouldn't do much more than the dry ice, and the dry ice is what's recommended in their datasheets whenever a cryo quench is specified...
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Well how about that... Interesting.
 
jawilder said:
Well how about that... Interesting.
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I was originally planning on getting liquid nitrogen into the shop to do the tests as I assumed 'colder was better', but after I talked to them I just went with dry ice instead. That advice only applies to CPM154, but the same seems to hold true for A2 at least as well. This is from the Uddenholm datasheet for AISI A2:

Immediately after quenching, the piece should be sub-zero refrigerated to between –40 and –110°F (–40 and –80°C)
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Dry ice holds a temperature of about -78ºC if I understand correctly, so it should certainly be cold enough for the application. I'm not sure if the temperature range applies to all steels, but my best guess is that it would...

EDIT: it's lucky that dry ice is all that's necessary too! I was quoted about $450/month to get a liquid nitrogen service in my shop. Whereas dry ice costs only about $100 per month, assuming that I'm heat-treating once per week in batches.
 
Nice job and interesting. I have never HT 440c myself, but the blades I made from it almost 30 years ago included subzero from the heat treaters. I was suprised you subzero'd most other steels, but not this one?
 
stevomiller said:
Nice job and interesting. I have never HT 440c myself, but the blades I made from it almost 30 years ago included subzero from the heat treaters. I was suprised you subzero'd most other steels, but not this one?
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The datasheet that I used for 440C didn't include a recommendation for cryo, so I left it out. That's honestly the only reason.
 
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