O1 Tempering Issues

No that's the bainite line.Air cooling from 400 F is just the right cooling rate. Holding at 400 f -just enough time for the temperature to equalize throughout the piece .
 
Man, that Cashen thread was perfect!! Thanks guys!
 
I guess the confusion (for myself) is where does the pearlite line go after 400F. Seems the orginal HT method I had believed that you would hold at 400f through the temper and then let go to room temp. I can see that is probably not necessary, I can let go to room temp after quench, and then temper. Well I am breaking the blade tonight, got a handle on it last night. I plan to sharpen, do the rod test, chop a hole in a 2 x 4 w the tip and try to break the tip, cut some rope, chop some wood and then bend (break) in half.

Thanks for the info
 
Patrickknives said:
I guess the confusion (for myself) is where does the pearlite line go after 400F. Seems the orginal HT method I had believed that you would hold at 400f through the temper and then let go to room temp. I can see that is probably not necessary, I can let go to room temp after quench, and then temper.
Click to expand...

The point is not just that it's "not necessary", but that it's counterproductive for the blade. Even at 350F, you only have 40% of the austenite converted to martensite. Tempering anywhere higher than the Mf, you might be lucky enough to make bainite of some of the unconverted austenite, but there's a very good chance you stabilize a bunch of it and end up with a less than optimum blade loaded with retained austenite.
 
... first make sure that it is actually a piece of good 01, and ready to heat treat!

... I love the basics! :)
 
If you just take a “real” piece of 01, heat it up to a cherry red, toss it in a bucket of oil, pull it out, slap it in the oven with your pizza, while it‘s still warm... Hey! It'll pass the brass rod test.
 
Interesting point, which a buyer at the forum brought up, if I recieve a piece of steel marked O1 with a white marker from a supplier how can we be sure if it is O1. Could be the guy cutting the 3' lengths from the long bar got sloppy.

This O1 was packaged (see pic) so I have alot of confidence in the steel but I have began to wonder about some of the unpackaged steel I buy.

steel011.jpg
 
Mismarked and mispackaged steel happens. I've had a few. I think it's still a good idea to "at least" do a spark comparison test with a known piece or pieces of 01.

If it doesn't have the properties of 01, it's not 01.

Paper is one thing, steel is another...

It just didn't sound like 01 to me. 01 is a very forgiving steel and it's easy to make a passable blade from.
However, to get the very most out of it, is a bit more tricky.
 
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I'm pretty sure my piece is O1 but I'll give it a spark test this weekend against another package of O1 I have around.

Another question. Assuming a fairly thin sharpening angle of approx 25 degrees inclusive, at what rockwell hardness will an edge pass the brass rod test and at what hardness will it fail on either end of the spectrum???

I'm guessing that it could have a pretty low rockwell hardness and the edge would not roll over. I'm curious as too how hard it can be and not experience any edge chipping?

Tai, you asked if I was performing my brass rod test like Wayne Goddard. I looked his info up and I'm pretty much doing it like he suggest. I may be using a little higher angle and a little heavier pressure.

One thing I'm going to try and do this weekend before tempering this blade a little higher is put a 15 degree per side microbevel on this blade and see how it does.
 
Lynn
I havn't tested a plain O-1 blade in awhile, I use all o-1&l-6 damascus, and my edges are ground to less than half what you listed and I have no problems passing the test. I temper at 400f. If it were me I would add a temper cycle before cryo. You may have microfracturing leading to brittleness.
Del
 
My understanding of the brass rod test is not to see if you can mash a blade into the brass and have it not chip. I believe it's more to see the properties of the edge as opposed to being a torture test. Basically, you want to push into the brass rod just enough to cause the edge to flex. If the edge flexes and doesn't return to true, the edge may not be hard enough. However, if the edge flexes and then chips, you have too much hardness. I would try the test at a bit lower angle, approaching so that the edge is just tipped up into the rod. Then look closely and press down to flex the edge and see what happens when you let up. If you're concerned about bone, take a piece of fresh bone and hack/slice away. Apples to apples.

Of course, I'm no expert in this, so above is taken with a grain of salt.

--nathan
 
With 01 you should be able to pass the brass rod test that way anywhere between a Rockwell 48 to 64, depending somewhat on the geometry... That's why I'm saying there's probably something else wrong with the steel besides just needing minor heat treating adjustments. All the brass rod test will tell you is whether or not the blade is seriously screwed up. It's not a good test for fine tuning...

With a well heat treated piece of 01 with good geometry,... you should be able to vigorously chop through a 3/8 inch round brass rod with multiple 45 degree angle blows, with little to no deformation or chipping along the edge.
 
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BTW, thank you ALL for this thread. Yesterday was a "Eureka!, I get it" day for me. It was perfectly timed too as I'm shopping for ovens as we speak. So thank you all for helping me so much, especially yesterday!
 
Well, I retempered at about 510F for an additional two hours. Brass rod test was performed with no chipping. That was the good news. The bad news is that the edge retention on this blade (there are actually two) was less than 40% of what I have recently been getting. (My edge holding test isn't very scientific but lets me compare my blades to each other. I have some approximately 3/4" manilla rope. Since I have had my salt pots I get 100 cuts. I quit at 100, which is significantly better than life before the salt pots. These blades struggled to do 40 cuts.)

I did do a spark test and am pretty sure that this is O1. I don't know what went wrong on these two blades. I have a variety of precision ground O1, lately I've been getting it from Flatground.com (I think). I've had some very good blades come out these shipments.

I'm going to reexamin my heat treating procedures, do some more blades and more testing. I had been heating at 1480F and getting good results. I'll try that again and keep good notes. I'll make sure and use steel from another bar and also probably re-heat treat one of these knives.
 
510 is too high. I usually temper O1 at 450-475, for a hardness of 60-61. I'm surprised you invested in salt pots, but don't have a hardness tester. :confused:
 
There could be some abnormality, flaw, impurity or error from the manufacturing process.

One other test you might try is fracturing a piece of the stock as it came and checking the grain. From an unhardened state you will probably need to cold chisel a groove to snap it along. If it looks real gritty, you may need to do some thermal cycling first to reduce the grain size, prior to hardening.

... something just doesn't sound right.

Were these blades forged or stock reduction? I was sort of assuming it was stock reduction. However, if they were forged, overheating could have screwed it up. If it was forged using blacksmith coal, sulfur contamination can make it brittle if you aren't careful with it.
 
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