Steel testing underway...

tmanifold said:
This has been very interesting to me because I am doing up a batch of knives in A2. One of A2's benefits is its cost compared to a lot of the other tool steels. It is nice to see some data that shiws that it is every bit as good (and in some ways better) compared to the pricier metals.
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The main tradeoff is simply that it's not stainless... My understanding is that the level of chromium required to make a stainless steel simply makes it much harder to get nice small carbides and a correspondingly tough steel.

My results are not the be-all and end-all though. Lots of makers have developed specialized heat-treats for some of these steels and may well be getting better results. My second round of testing I'll be trying out some optimized recipes for each steel.
 
While some people may have tricks for various steels, the way you did this test is great for you average knife maker. I would guess most people heat treat in accordance with the data sheet. Just as you did. It doesnt matter what Paul Bos can get out of the steel if I am the one doing the heat treating. Thanks for putting in the time for this.
 
tmanifold said:
While some people may have tricks for various steels, the way you did this test is great for you average knife maker. I would guess most people heat treat in accordance with the data sheet. Just as you did. It doesnt matter what Paul Bos can get out of the steel if I am the one doing the heat treating. Thanks for putting in the time for this.
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Sure, I think that's a reasonable way of looking at it. There are often optimized recipes floating around for the various steels though. I intend to try some of them out with my next batch of testing, I'll be interested to see what the results are like!
 
Thanks Aaron! You've done testing most of the rest of us don't the time or resources for. I'm not real surprised to see simple carbon steel do so well compared to stainless in general terms. All my years of carrying a 3 blade stock knife in my pocket has shown me I like the performance of simple carbon steel more than stainless, even if I do have to pay extra attention to the blades and take care of them.

I have a hand plane in the wood shop that has a Hock brand A2 cryogenic blade in it. The Hock blade holds an edge much better than the stock blade that came with the hand plane. A2 must be good stuff, I'll have to look I to A2 some more.

If you can get some in Canada could you add 1095 to your list of steels to test? I sure would like to see 1095 compared to the other steels.

Thanks again for all your hard work! :thumbup:
 
woodwrkr221 said:
Thanks Aaron! You've done testing most of the rest of us don't the time or resources for. I'm not real surprised to see simple carbon steel do so well compared to stainless in general terms. All my years of carrying a 3 blade stock knife in my pocket has shown me I like the performance of simple carbon steel more than stainless, even if I do have to pay extra attention to the blades and take care of them.

I have a hand plane in the wood shop that has a Hock brand A2 cryogenic blade in it. The Hock blade holds an edge much better than the stock blade that came with the hand plane. A2 must be good stuff, I'll have to look I to A2 some more.

If you can get some in Canada could you add 1095 to your list of steels to test? I sure would like to see 1095 compared to the other steels.

Thanks again for all your hard work! :thumbup:
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Thanks mate!

I'm actually going to hold off on testing the simple steels for the moment as I'm under a bit of a time crunch to get back to making knives for my customers... I'd love to be able to do a test with damn near every steel at some point, in the future that will definitely be something I look at doing! I quite enjoy the process.

I quite like 1095 personally (In the KaBars that I've owned at least), but I don't have much experience with it beyond that.
 
1095 is no prob in Canada. I have about 10' of 1/8" 1095 in the shop. Same source as I posted above for the 1084.
 
I'm excited to see what the 1084 can do. With it being low cost and easy to work with I'd love to see it perform well.

Also I'd just like thank you for taking the time to share your results
 
Ok guys! The next batch of test blades have just gone into the kiln for stress relieving. I'm doing a full spread of steels again in order to compare optimized heat-treats across all the steels. Steels being tested: A2 (2 blades), O1, CPM154, CPM3V, 440C.

Highlights of the new heat-treats:
Lower Austenitizing temperatures where possible: each steel will be austenitized toward the lower end of it's temperature range to help lower amounts of Retained Austenite after the quench. (except CPM3V which needs the higher temp to reach full hardness)

Faster Quenches: all blades will be either plate quenched or oil quenched, again this will help lower levels of retained austenite

Sub-zero treatments before tempering: last time most of the sub-zero treatments I did were in between the tempers, this means that some blades may have had retained austenite that was stabilized by the first temper. This time all blades will undergo sub-zero treatments before the first temper in order to help fully eliminate retained austenite.

Better protection from atmosphere: 440C, CPM154, and CPM3V will all be enclosed in stainless foil tool wrap. The envelope for each blade will have a small piece of paper added to burn up oxygen inside the envelope. All other blades will receive a double coating of anti-scale compound (ATP-641).

The specific recipes:

A2:
Double coat in anti-scale (ATP-641)
Ramp to 1740ºF @ 400ºF/hr, hold 20 minutes
Oil quench until no longer glowing, then cool in still air to room temperature
Sub-zero treatment in dry ice and isopropanol for 45 minutes
1 blade: Temper @ 360ºF, twice, 2hrs each time
1 blade: Temper @ 400ºF, twice, 2hrs each time

CPM154:
Wrap in stainless foil envelope
Preheat to 1400ºF, hold 10 minutes
Ramp to 1900ºF, hold 60 minutes
Plate quench to ambient
Sub-zero treatment in dry ice and isopropanol for 45 minutes
Temper @ 400ºF, twice, 2hrs each time

O1:
Double coat in anti-scale (ATP-641)
Preheat to 1200ºF, hold 10 minutes
Ramp to 1470ºF, hold 30 minutes
Quench into oil to ambient
Sub-zero treatment in dry ice and isopropanol for 45 minutes
Temper @ 400ºF, twice, 2hrs each time

CPM3V:
Enclose in stainless foil envelope
Preheat to 1500ºF, hold 10 minutes
Ramp to 1975ºF, hold 30 minutes
Plate quench to ambient
Sub-zero treatment in dry ice and isopropanol for 45 minutes
Temper @ 975ºF, three times, 2 hrs each time

440C:
Enclose in stainless foil envelope
Preheat to 1500ºF, hold 10 minutes
Ramp to 1875ºF, hold 30 minutes
Plate quench to ambient
Sub-zero treatment in dry ice and isopropanol for 45 minutes
Temper @ 400ºF, 2 times, 2 hrs each time


After all the blades are heat-treated they will be polished on a scotch-brite belt, and then lightly etched to help make any decarb or other issues visible. After they've all gone through the testing process I will be taking all the blades in for Rockwell testing.

Looking forward to seeing the results! I sure have learned a lot already through this whole process...
 
Looking forward to the results of this one man.

Quick question, what kind(s) of oil are you using for the oil quenched steels?
 
weebus said:
Looking forward to the results of this one man.

Quick question, what kind(s) of oil are you using for the oil quenched steels?
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Unfortunately I'm just using vegetable oil. I have a Houghton rep locally that I've talked to, but the prices are too high to justify given that I haven't decided which steel I'm using yet!

The vegetable oil should be fine for the steels involved, and you just end up having to replace it more often to make sure the consistency doesn't change too much...

If I decide to use a steel that requires an oil quench then I'll be investing in some appropriate Houghton quench oil for longer term use.
 
Heat the vegetable oil to 120-130f for the O1. If you get the 1084 in time for the test, it really benefits from a faster oil. Its OK with heated canola, but not at its best. I am using Maxim DT-48. Its about the same speed as Parks 50. Pricey, but really only about double what 5 gallons of canola oil would cost in my area. I have done an interrupted brine quench with 1084, and was much happier with that than the straight canola oil quench.
 
Ok guys! The second batch of blades are now heat-treated and ready except for the CPM3V which is still in the temper process.

Here are the blades as they are right now:
JhHQSkml.jpg


The two on the right are 440C and CPM154, which were both heat-treated in foil envelopes. The others are the oil quenched steels.

All of the blades are very smooth and seem free of scale, I don't see any decarb as of yet either, but that will be proven one way or the other after polishing.

I will say that it looks like the blades are cleaner overall this time. The double-coating of anti-scale seems to have worked well. It's also worth noting that the thicker coating of anti-scale actually blew off more cleanly in the quench, with only a single coat I normally have some compound stuck to the blade after the oil quench, this time there wasn't any!

I'll be putting all the blades to the scotchbrite belts, and then etching them today. Tomorrow the real testing will begin!
 
Willie71 said:
Heat the vegetable oil to 120-130f for the O1. If you get the 1084 in time for the test, it really benefits from a faster oil. Its OK with heated canola, but not at its best. I am using Maxim DT-48. Its about the same speed as Parks 50. Pricey, but really only about double what 5 gallons of canola oil would cost in my area. I have done an interrupted brine quench with 1084, and was much happier with that than the straight canola oil quench.
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I decided the 1084 will have to wait until the next round, I need to get back to making customer knives after this round of testing is finished!

The oil used for the O1 would have been about 120ºF or so when I did the quench, as it was pre-warmed by the A2 quench which went a while before it. I didn't measure it exactly though.
 
Thank you for doing this. Its been a lot of fun reading and seeing the results. I am really curious as to the differences with the "knife specific HT" compared to industry spec.
 
Backyard O1 was really interesting.
Top tiers in cutting - fine and coarse, which means good wear resistance and yet - plastic deformation on bending.
Did you made hardness tests?
 
Willie71 said:
Thank you for doing this. Its been a lot of fun reading and seeing the results. I am really curious as to the differences with the "knife specific HT" compared to industry spec.
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I'm definitely interested to see the comparison as well mate!
 
idaho said:
Backyard O1 was really interesting.
Top tiers in cutting - fine and coarse, which means good wear resistance and yet - plastic deformation on bending.
Did you made hardness tests?
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Haven't done the hardness tests yet, the place I have to go to get them tested is a while away from my house, so I figured I would wait and get all the blades done at once as I'm doing a second round of testing right now.
 
Ok! Well I found a minor issue after polishing the blades on a scotchbrite belt, it appears some of the blades suffered some slight decarb. The foil envelope for the CPM154 clearly had a tiny leak near the tip of the blade, and there was some noticeable decarb at the tip.

zXl5D7Dh.jpg

Here's what the CPM154 looked like after polishing, notice the speckly decarb in the middle of the photo.

The A2 blades both also had 'pinhole' spots of decarb spread evenly over the blade surface. The decarb seemed shallow, so to test this I sanded the blade surfaces back to see how long it would take before the physical symptoms of the decarb were no longer visible. It only took 1 piece (not sheet) of 150 grit, and 1 piece (not 1 sheet!) of 220 to sand off the visible decarb in all cases.

I then etched the blades for a few seconds in a strong solution of Ferric Chloride to see whether there were still decarburized areas. You can see the decarburized areas as lighter colored areas on the blades. The darker colored areas are sections where the steel is physically less smooth (finished to a lower grit), the dark lines are leftover grinder marks. I'm not finishing these blades to a high standard as they're only test blades...

QreoJUzh.jpg

CPM154 test blade after light etching, notice the crescent of lighter color indicating decarb near the tip.

0I9cZeth.jpg

Reverse side of CPM154, notice small lighter color section of decarb on the spine toward the tip.

TN2gOqFh.jpg

A2 test blade after etching, notice small lighter colored speckles spread across the blade indicating small sections of decarb.

I seriously doubt that any of this decarb is deeper that a couple of thousandths of an inch, and I also doubt that it will cause a problem for any of the blades. If anyone believes otherwise though then they should definitely speak up now!
 
No laughing at my grinding by the way! :D

I'm still learning to use the grinder as all my previous knives were done on a filing jig, my grinding has gotten better since doing these knives.
 
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