Thermal Cycle Scale?

Brian Avila

Brian Avila

Joined
Jan 2, 2011
Messages
1,286
So I have found that I get this "thin scale" when I thermal cycle my blades. I put the blades in, hit the temp and then when it hits temp take them out and hang them so they can cool enough for me to touch and then continue again.

This scale is really brittle, it starts to crack and then fall off each time I thermal cycle. I am using an EvenHeat oven. I am at 5800 feet in elevation.

I was hoping you guys could tell me what it is and how to prevent it. I don't think it is actual scale. It seems to only happen on my 1095 blades and not on my O-1 blades. This "scale" if it is scale doesn't come off when I soak the blades in vinegar either.

Ideas?

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Well, no one has described scale like this to me before, and it doesn't look like this to me after heat treat. But after soaking the stuff in vinegar for about 4 hours it is starting to come off. I will let the knives sit in the vinegar over night and see what happens. From what I am seeing, it is just normal scale, and it will come off after soaking for a long time.

I will update this tomorrow.
 
Well, no one has described scale like this to me before, and it doesn't look like this to me after heat treat. But after soaking the stuff in vinegar for about 4 hours it is starting to come off. I will let the knives sit in the vinegar over night and see what happens. From what I am seeing, it is just normal scale, and it will come off after soaking for a long time.

I will update this tomorrow.
 
Usually after forging Ill let something sit in vinegar overnight or if I am using ferric probably a couple hours then give it a good scrubbing. Looks like scale but I do stuff in a forge so probably not much help as far as your oven goes.
 
Just plain old scale.

You can soak the blade in vinegar for a few hours to remove most of it before final sanding/grinding if needed.

A blade coating of ATP-641, PBC or other anti-scale coating will prevent it.
 
Protect your blades in a kiln. The rate of decarb is MUCH higher than the reducing atmosphere you can create in a forge. If you're doing lots of thermal cycles (which you probably should be doing), you'll be significantly reducing carbon. Coatings are your friend here. Be advised, however, you need to place a layer of HT foil on the bottom of your kiln so the coating doesn't eat the bricks of your Evenheat, cuz it will!!!!
 
Also a thin wash of satinite is a good coating for thermal cycling.

Stan
 
Yeah, the scale was just normal scale like you guys said, took almost 24 hours to get all the stuff off. I will try a thin wash of satinite because I have that. And place some tin foil at the bottom of my kiln.
 
Wait... doesn't using a thin layer of satinite not allow it to work as well when you thermal cycle?

Differences between using satinite or ATP-641, PBC to help reduce scale when thermal cycling in a kiln?
 
I use PBC for thermal cycling. Satanite doesn't keep the steel immaculate, and although it helps, it doesn't work as well as PBC.

If you're going I be clay coating the blades for hamon, thermal cycle them using PBC, then clean the blade entirely of the coating and apply satanite and quench. Your blades will have good grain refinement, no loss of carbon during thermal cycling in your kiln, and be ready to quench!
 
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