Heat Treat problem?

rhrocker

rhrocker

Joined
Jan 18, 2004
Messages
1,135
This is some O1, the blade is a rather large Bowie that I'm making. While finishing at about 400 grit, I started noticing the "blotchy" pattern. If I slowly run my fingernaeil across these areas, I can feel that it's rougher, maybe "micro-pitted" if you will. I used Brownells PBC at about 550 F and got a nice dark coverage, then ran the temp up to 1550, with the blade in the furnace (Lindberg), soaked 30 min, edge quenched in Brownells super, I did not heat the oil, but rather followed the instructions on the can. The blotchy pattern was in the oil. Then tempered at 400 for one hour, twice. I'be backed down to 220 grit, but it hasn't taken the problem out, will try aggressive 120 today. The other side of the blade is beautiful. Any ideas, any solutions?
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The problem has been taken care of. The strange pattern on the blade might be due to how I applied the PBC, or maybe the blade was oily or dirty there?? At 550, the oil or dirt may well not have burned off, then the oily part was protected throughout the ride to 1550. Anyway, all's fine. I took my air sander with 220, and really worked the entire blade this AM, and followed with hand working 120-1200, and things look fine. I'm going to chalk this one up to improper use, or inadequate temp of the blade when applying the PBC. I have a digital thermocouple, and will also be checking and verifying the temps. My Lindberg is an old fossil, and so the calibration, setpoint, etc may be way off.
I was worried, I have a lot of time in the Bowie already, and it's for my first show next month.
 
Great thing about O1 is that you can always normalize it and reheat treat it without any problems(coupla normalize/anneal cycles if you really overheat it and end up with massive grain. But case still stands). I think you're right though that it'sjsut a surfact problem, either with it being dirty, or not hot enough when applying the PBC. THink you're fine there.
 
Robert,

Looks like you may have gotten a little decarburation there. Nothing perhaps to do with that particular anomoly but the 30 minute soak seems a bit long to me for O1; 1475 - 1500 F soaked about 5 minutes is what I would have done. Maybe you have been doing it the other way with good results and if so I won't argue with success.

RL
 
I've also been having some trouble in hardening and tempering O1. The last 3 knives i've done have went into to the oven looking smooth and come out looking like i've etched a web pattern on them. I bring the oven up to 1500 and hold for about 5 to 10 minutes then quench in salt water. I always clean the blade well with acetone before cooking them. Am I doing something wrong or is it just a bad piece of steel.
 
It did not dawn on me earlier to mention this but since I also use Brownell's PBC:

I heat treated a 1075 blade a couple days back. I used PBC to coat it. I too preheated the blade to about 525 F before coating it. After quenching, in Brownell's Tough-Quench preheated to 105 F, I have a really nice but not expected or even wanted quench line (I did a full quench). The hamon looking thing matches on each side, just like if you wanted to do it that way. The only thing I can figure is either mY PBC was too thick near the spine or there is something about that batch of steel. I am inclined to believe it the former and since this is a 1/4 inch thick stock it might make sence that if the PBC was thicker at the spine that portion of blade would lag in quench.

A thing I have noticed about PBC is that it is receptive to gravity. I place blades edge up in the oven. I have learned that in order to get the blade out quickly for quenching you really have to be on your toes because any excess PBC rolls down to the base that the spine is setting upon and it is like thick glue in liquid form. Getting the blade released from the foundation requires two quick steady hands.

I have post heat treat grinded the blade to 400 grit and the (supposed) quench line is still there. You have to turn the blade just right to see it but is distinct and very close to being the same on both sides. It is not a crack. Looking at it through magnification shows it fades in contrast as it approaches the edge part of blade.

It is interesting to me and I have not experienced this before on a full quench. It is also my first time heat treating 1075.

RL
 
Roger,
I don't think it's that unusal to get the line on a full quench with the 10xx series steels, whether you use an anti-scale compound or not. I can't tell you why. Maybe Mete or Kevin Cashen can.
 
The steels like 1075 are fairly low hardenability and using 1/4" stock and retarding the quench a bit with the PBC is probably the reason for the hamon.Have you tried comparing pieces with and without PBC to see how much it retards the quench ? ...We should be using the word hamon rather than 'temper line ' because it has nothing to do with tempering .It is just where the martensite and pearlite areas meet.
 
Good point, mete! Coin an Americanized term, like "hardening transition" or something like that we can all start using.
 
fitzo said:
Good point, mete! Coin an Americanized term, like "hardening transition" or something like that we can all start using.
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MPT Zone

Martensite Pearlite Transition zone
 
Could it maybe be your blade geometry? If the quench time was borderline close, the thinness of the edge could harden leaving the spine not properly hardened and leaving you with the transition line.
 
I still don't think that the PBC was the cause, though it may have possibly contributed in making the line more pronounced. I was working with the 10xx series steels before I started using PBC, and it was not unusual to get a line even when the blade was fully quenched -- though obviously nowhere nearly as pronounced as what I do on purpose now.

By the way, I don't think the term temper line has been used in this thread -- at least I don't see it. I get tickled when the purists get upset about it though. I still think that the term is just a holdover from the old days when the entire process of hardening and drawing was often referred to as tempering.

Most of my customers call what I do "bold temper lines", as do most of the Masters, as well as the magazine editors and authors. I never correct any of them and often use the term myself simply because it is so widely used. That is except when I'm around someone that I know is "anal" about terminology. :D Then I generally say "transition line" or something of that effect.

It just doesn't bother me. To me it's about like someone offering me a bag of "Tom's Corn Chips", and asking me if I want some "Fritos". I know what they mean and that's all that matters.
 
primos said:
That is except when I'm around someone that I know is "anal" about terminology. :D Then I generally say "transition line" or something of that effect.
Sorry. I guess I've been anal about terminology for so long it just comes natural to be that way. Probably some leftover from science-boy days! Organic chemistry sorta hammers "terminologic anality" into one.... :)

At least we're not calling it "that line thingy in the blade" ;)

And you're right, Terry, as long as we all know what's meant, colloquialisms are just fine.
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