Dealing with Decarb in multiple normalaztion cycle's, coarse spheroid annealed steels

Kentucky

Kentucky

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Dec 13, 2008
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When your normalizing coarse spheroidal annealed steels like Aldo's 80crv2 how do you personally deal with the ridiculous amount of decarb you end up with :grumpy: Just leave it extra thick and grind it thin? maybe a satanite wash or doing it before you grind?
 
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80crv2? After normalizing at 1650,1550 and 1450 we do a 1500° aust' with a 10 minute soak and quench in parks 50.
 
Grind it. But I'm playing with satanite skim coats. Worked well on my cutlass. Going to try the same on the hunters I've got in progress.
 
I'm a relatively new maker here but just experimented this past weekend during my heat latest heat treat. BORIC ACID - my new best friend! I don't have my phone handy to upload the pics but check this link to my WIP post, scroll to the second set of pics: http://www.bladeforums.com/forums/showthread.php/1440303-Knives-5-amp-6-WIP-Gyutos

I preheat the blades in my little toaster oven to 450-475, pour the boric acid powder over the blade onto some foil, then wrap the foil around the backside of the blade to get both sides. The power will stick and kind of "fry" to the blade. Once i put the blades in the furnace the boric acid powder melts to a sticky clear consistancy and coats the blade stopping the decarb. You can see on the blades where I didn't coat fully, especially on the handles. Really making post HT clean up much better than my last 3. I got that bottle off Amazon for $9.98 it is more granular like sugar. I also got a bottle of ant rid stuff same size bottle from Walmart for under $3 that is 99% boric acid per the label, it is more powdery like powdered sugar and it kind of clumped up (chalk that up to Florida humidity) both worked equally well and will become a part of my HT regimen from now on.

Make sure if you use stands in your furnace or oven the knives will be a bit sticky so the stand may come up with the blade. My furnace blade stands were heavy enough to drop off once the blade was lifted an inch or two up. Also when I quenched the boric acid solidifies and for me it turned a slight orange-ish tint so when I pulled the blade out of the oil I thought I was still super hot! Not so. The solid boric acid also cracks and falls off into the quench oil- it scared me as I thought the blade cracked. Again, not so. Blades came out clean and hardened. Super cheap solution to a problem and easy to do. Very pleased and am starting post HT work.

I wish I'd taken pics to show in progress but imagine the blades covered with glaze like a Krispy Kreme doughnut going through the oven. Any remaining crust from the BA can be scraped off during clean up. I'm a fan. Let me know your results!

Blaster-6
 
I use Rust oleum 2000 degree spray paint on all steels that I do not wrap in foil, it keeps the decarb to a minimum thickness.
 
I use the Brownells ATP 641, I think that's the number, but whatever it is I found it works great. I was quite amazed at how much scale it prevented when you get a good coat on. The blades come out nearly as clean as stainless in foil. I mention getting a good coat because if you do not clean all the oil and crap off the blade before trying to coat it the wash tends to bead up and not want to cover.

I've never tried satanite or anything else on carbon steels so I can't compare its effectiveness.

-Clint
 
in heat treating oven where theres lots of oxygen I use stainless foil to normalize, then during hardening just go in without foil. Much less decarb than having naked blade heated 3x first. :)
 
I use PCB antiscale compound, it doesn't eliminate decarburation, but keep it at bay.
Even the forging scale slows the decarburation, PCB does its own too and if you don't burst the blades by final grinding you could keep the norm. step before and just do a subcritical stress relieve before hardening.
Not many take decarburation into the deserved high consideration
 
ndp_2010 said:
in heat treating oven where theres lots of oxygen I use stainless foil to normalize, then during hardening just go in without foil. Much less decarb than having naked blade heated 3x first. :)
Click to expand...

The risk in doing this is cooling too slow between cycles if using a hypereuctoid steel. This can cause undesirable structures in the steel. I'd have to look up the technicalities to explain it better.
 
I still have some Turco left, which is what I use. It appears to be a mix of boric acid and yellow ochre, with some sort of binder like gum Arabic.
 
Don't forget that decarb and scaling are two different things.
Excessive scaling may be indicative of some carbon loss, but carbon loss is measured usually in long periods of time at almost welding heat. Carbon moves much slower than is often tossed around in conversations like this.
In just a recent thread Stacy even mentions that, for the most part, the carbon you start with is the carbon you end with.
Doing simple normalizing cycles should result in almost no carbon loss at all. The only carbon you're losing is what was in the scale/iron you're losing right at the surface of the steel.
It didn't just jump out of the remaining steel.

Literally, carbon moves at the atomic level in MICRONS per HOUR at high heat.

I see four different references in this thread to "decarb" when what is being referred to is "scale/iron oxide".
You can't SEE decarb. You can only assume it's happening. And it doesn't happen except for during long periods of high heat.
Just a little grinding and you're right back to the steel/carbon you started with.

Now some are going to freak out about this and defend their honor.
Yes - there may be some carbon loss, but how much is lost during normal forging and normalizing, heat treating, etc., is so small as to not even be worth worrying about.
If you find you can't harden your steel or something odd like that because of 'carbon loss'. then you have some other serious over-heating issues in your knife making process.
 
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That's a good point. When I say decarb, I'm referring to the soft layer of material that always exists after heat treat, usually .005" to .020" thick depending on material, temp, time, etc. I'm using satanite wash to reduce scaling, not necessarily decarb, although I imagine it does help with that.

If carbon moved out of the blade as fast as some think, forging wouldn't be possible.
 
I used to deal with decarb. No longer. ATP-641. I use it on normalizing, thermal cycling, and austenitizing. ZERO decarb, ZERO scale. None. The only thing I don't like about it, it will flake off during air cool, and needs to be reapplied every cycle. No big deal, just wish it would stick better. I have heard PCB will stick better during cycling.

It is super easy to apply, water based. I use a toothbrush (my wife's...ha ha!), dip the tip in the can, use the toothbrush to paint it on and make thin layer. Wife's hair dryer to dry it!

Like Clint mentioned, blade needs to be clean. Acetone, kitchen soap/scrub real quick, finish with Windex.
 
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