Problem with O-1 or is it me???

calharkins

Well-Known Member
I use O-1 quite a bit especially on tactical blades. I went to test a blade that had just been finished and it would not hold a good edge. I didn't do anything different that I know of. All of the blades in that batch had the same problem. I will give you my procedure. I use a forge to heat the blades. First I normalize the blades 3 times. I heat the blade to about 1500 degrees and soak the 1/4 inch thick blade about 3 minutes. I quench in vegetable oil heated to about 125 degrees and then temper twice at 425 degrees in a toaster oven. I grind the heat treated blades with my bare hands so I don't get them too hot. I am still scratching my head trying to figure out what happened. Could it be the steel? Any help would be appreciated.
 
Cal I use a lot of O1 and your pretty close to what i do. the first this I'd look at is the toaster oven. they are notoriously fickle and can go south at a drop of a hat. it may be getting a lot hotter than you had planned and over tempering your blade.

Erik
 
Cal, obviously this HT has worked for you in the past, so it makes sense to see what has changed. The toaster oven is a usual suspect for sure. You have enough experience that we can presume you have the soak temperature close. I'm going to suggest you'd get more out of O1 if you soaked it longer - like maybe 15 minutes or more but you haven't done that before so it wouldn't account for the reduced performance.

The only other suspect that comes to mind would be to ask if there is new lighting in the shop / smithy that might affect your color perception.
 
I would agree that it is likely the oven, but you also have other factors working against you. 1500° is a tad hot for 01, and is better at 1475° for your quench heat. It really needs to soak at least 15 minutes at temp, and 20 may be better for 1/4". Especially if you are grinding after HT. You say about 1500°. How do you determine that temp? 01 is not a forge friendly steel. With consideration for your equiptment, 1084 would serve your needs much better.
 
Thanks for the replies. I am going to use the wife's oven to temper the next batch. I will use an oven thermometer as well. I have a thermometer on the forge (a PID with a K thermocouple). I would try to soak longer but it is real hard to try to control the forge temperature. I started with O-1 and have had very good results with it. I normally get a real sharp edge that holds well. I tried 1095 but I have had a lot of warping with it. Thanks again for your help.
 
It could be that your vegetable oil has degraded. How much have you used the same batch, how old and what does it look like?
 
Tai, the oil is about a year old but it was clear. You could see the bottom. It smelled ok. It may need replacing. I don't know. Planned on getting some canola oil any way.
 
I just made a trip to Jantz. It is about an hour away from me to get more steel. I have to get these blades done. I will watch everything very closely. Tai, do you think the oil may have been bad?
 
Yes.

One year on a small volume is about it. Even that might be pushing it, depending on a number of variables.
 
My first thought was the oil....that and 01 can be persnickety.
Have you tried making "junker" blade and seeing how hard it got? It should snap easily if bent and shatter if smacked hard with a hammer. Watch for flying chips in either case. Sharp little missiles are going to come off a snap or shatter test.
 
Boss, making some test blades is next on my list of things to do. Working is getting in the way of a lot of things:biggrin:
 
I had a buddy that had the same problem with an 01 blade. Told him to put at least one oven thermometer in his toaster oven and he found it it was almost 100 degrees too hot. I can get my toaster oven set where I want it one day and do nothing to it other than start it another day and it may be off 50 degrees. Gotta watch it!
 
The other problem with toaster ovens is that the blade will be too close to the heating elements. The edge and point can overheat as they cycle on and off. It's a good idea to shield the blade with a muffle or some extra baffling and be sure and give it time for the inside temp., to stabilize (as well as it can) before putting the blade in.
 
Well I made a test blade of 1/8 thick O-1 tool steel. Heated in forge at 1500 degrees until non-magnetic then held it for 3 minutes. Quenched in fresh canola oil heated to 120 degrees. Tempered in wife's oven at 400 degrees for 1 hour. Repeated temper cycle. The blade is hard and will hold an edge well. At this point my best guess is that the old vegetable oil I had been using as a quenchant was not doing the job.

Thanks to all you guys that offered your help.
 
Well I made a test blade of 1/8 thick O-1 tool steel. Heated in forge at 1500 degrees until non-magnetic then held it for 3 minutes. Quenched in fresh canola oil heated to 120 degrees. Tempered in wife's oven at 400 degrees for 1 hour. Repeated temper cycle. The blade is hard and will hold an edge well. At this point my best guess is that the old vegetable oil I had been using as a quenchant was not doing the job.

Thanks to all you guys that offered your help.

Reading the above, I see another possible clue. Non-magnetic is 1414°, and not 1500°. You may not be getting the 01 hot enough to get hard enough.
 
“Non magnetic” means at or above the curie point (1414). It’s nearly impossible to hit 1414 on the nose in a forge. The problem with using a magnet is that it will tell you that you are above the curie point, but not how much over. The magnet can be used as a temperature reference, but what you have to do is find the point just below non magnetic and just above. For most carbon steels you’ll want to go 50 to 100 degrees above the curie point… which is usually what happens anyway.
 
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True, that's why you need to find the point just below and just over, then bring it up a shade,... rather than just relying on luck.
 
On using the toaster oven to heat treat the blade. Use a pan or tray of sand to put the blade in the buffer the effects of the elements cycling on and off.

Another thing that could be happening is your soak time, and I admit that I'm talking theory here, is that you are not giving the O1 time enough to put the carbon into solution. I know that you say the you're holding it at 1500 degrees for three minutes but if you are using a forge, I wouldn't bet on it. You could be going higher or lower. Too low and three minutes will not put enough carbon into solution and too high you may get the carbides to break down and release the carbon into solution but you risk growing the grain. You could be getting way too much carbon into solution by getting the steel up to 1550°-1600°, which would be very easy to do in a forge, and, even for a short period, you get so much carbon into solution that you form excess retained austinite formation and you can't achieve the hardness that you want either. Personally, I think that the best thing for steels with much over 84 points of carbon is to austinize in a regulated high temperature oven at under 1485° and stretch the soak out to about 10 minutes.

The vast majority of hobbiest or small time knife makers are at a disadvantage in the we have to operate on a bit of theory and a lot of by guess and by golly. A commercial outfit can make a test run, taking careful notes and send the blade out to be sectioned, polished, and examined microscopically and even a look with an scanning electron microscope to check the crystal formation in the steel. Kevin Cashen is the only person that I know of who can do such analysys and I doubt that even he has a scanning electron microscope in his basement. All that we, the average guys, can do is follow the cook book procedures and maybe throw in a third tempering cycle and hope for the best. It's also a good idea to match the steel that we are using to the equipment that we have at hand. For a gas forge and a toaster oven I think that it indicates a hypoeutectic to mildly hyhpereutectic simple steel that is more forgiving of an austinizing temperature that cannot be held within range. I know that we want to use the super duper higher alloy steels, believe me, I'm the same. And yes, we can produce a good knife with the likes of O1 or 52100 but to do it reliably and consistently we need something with more heat control than a gas forge. All it takes is a little brigher shade of orange for just a tad too long and we have problems and no way to see it.

Doug
 
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