Anti Scale Contamination?

[tkroenlein]

I've recently started using Turco, and I'm not sure if I'm solving a problem or making a problem.

In the picture, if you strain your eyes just right, you can see a shadow about 3/16" from the grind line. I believe this is an effect of the migration of whatever is in Turco that occurs during heat treating. It is .008"-.010" deep.

This particular blade is 52100. I double dipped it in Turco, and normalized the blade at 1700F for 20 min, followed by two heats for 30 mins at 1460F with a furnace cool to 1260F on the last cycle.

My intent with this was to set up the blade to need only the final austenitizing heat at 1500F, treated again with Turco, so I can get closer to final grind dimensions. The Turco is effective at limiting decarb, even at 1700F which is over the 1600F limit that it is advertised at.

I'm curious if anyone has experienced this.

 

[opaul]

Has the blade been quenched yet?

 

[tkroenlein]

Has the blade been quenched yet?

No.

 

[tkroenlein]

Let me first apologize.....there's a much bigger issue going on here than the turco, and it's gona seem like I'm ranting....which in a way I am, but it's NOT directed at the OP...... but rather an overall thing.


Not trying to be mean, but if you actually did that on a 52100 blade, you might as well throw it out and start over. That blade is wrecked. 52100 is very susceptible to overheating damage..... and that temp, for that amount of time is WAY overdoing it. I'm not going to even ask where you got that formula..... this overheating and over soaking steels has gotten so far out of hand. Suffice to say that with it's current dimensions, I doubt there's going to be any saving that blade. I have no idea who's out there pushing the times and temps for "soaking" blades.....but each time I see an instance posted, the temps get higher, and the times get longer.......again..... IT IS WAY OUT OF CONTROL! At MOST...... for any carbon/alloy steel, a soak of anything more than a couple of minutes (with very few exceptions) is causing far more harm than good. I would venture to say that if you were to break that blade, it's likely going to look like a gravel road inside. Finishing it out would produce nothing more than a KSO (a knife shaped object)

Wouldn't forging subject 52100 to even higher heat for an even longer period of time?

I'm following Larrin Thomas' recommendation for DET annealing to the letter. It was performed and tested by Devin Thomas. I suppose folks can disagree with the HT schedule, but this steel is *butter* soft and in no condition to austenitize as-is. I chose a HT schedule to follow that seemed to have supporting data that suggested it would work for me.

 

[KenH]

to the OP: While I don't have any knowledge of using Turco, let me see if I understand your process here. The idea with this stage was to get the billet of metal as soft as possible realizing the grain was waay large. After profiling and any bevel grinding desired, the next heating step would be a grain reduction phase to prepare the blade for final HT 'n Quench.

 

[tkroenlein]

to the OP: While I don't have any knowledge of using Turco, let me see if I understand your process here. The idea with this stage was to get the billet of metal as soft as possible realizing the grain was waay large. After profiling and any bevel grinding desired, the next heating step would be a grain reduction phase to prepare the blade for final HT 'n Quench.

Here is the exact processing. There are 2 reduction cycles.

1700 F x 20 min Air Cool
1460 F x 30 min Air Cool
1460 F x 30 min Furnace Cool to 1260 F (665F/hr)

The next step is austenitizing at 1500F for 10 min.

The purpose is to normalize and thermal cycle like a lot of other schedules. That is to say to improve HT response.

I did it in this order in an attempt to minimize decarb due to the Turco failing after a few cycles.

 

[J. Hoffman]

I've never used Turco, but have used hi temp paint with ok results. I prefer just wrapping them in foil when doing the thermal cycling.

 

[tkroenlein]

Just in case anyone was following along...

I am pretty well finished with the 3 knives I had processed with the Turco.

My verdict is the "line" is/was decarbed steel. The interesting thing is that the surface layer wasn't pock marked and uneven like it normally does. But it was definitely decarbed. Hardness readings before I ground the line out were anywhere from 40-55 HRC. After I ground about .005" off, all 3 tested at 61 HRC.