Normalizing carbon steel with a foil packet

[Tyler.t76]

I have a forged out blade that I am going to normalize in my kiln (15n20+1084 billet), usually when normalizing I’ll either just leave it thick and grind through the decarb or use some of the anti-scale clay. I’m wondering if I could use my heat treat foil instead of the clay for my normalizing cycles, as I’m not the biggest fan of the clay.
Obviously it’s “overkill” to use a foil packet here, but I have plenty of foil and a lot of hate for decarb and scale… so is this an option?
Or would there be an issue with the cooling rate having the packet acting as an insulator?

Apologies if this has been asked before, but I couldn’t find anything on it.

 

[Stuart Davenport Knives]

No problem at all using foil during normalizing or cycling. You are good to go.

 

[JV Knives]

No issues....I leave my blades wrapped in the foil through austentize and temper. I'm sure your steel will not be affected by using the foil for temper...except maybe a bit cleaner

 

[Pinoy Knife]

i guess im the stupid one here that all high carbon steel will have decarb on it after any high heat ...
but a very smart guy once told me to just soak it in white vinegar overnight and the decarb is gone without any real work except patients on my part...
you are going to get scale/decarb every time you get it very hot ...so why not eat that scale/decarb off with vinegar ?? instead of grinding your steel away at each step
then once heat treated/tempered get the surface smooth ..... just have to wonder how many have actually soaked their blade in vinegar overnight ????

 

[Stacy E. Apelt - Bladesmith]

No chemical soak will dissolve decarb. Decarb is still steel ... just low to no carbon steel.

White vinegar (glacial acetic acid) works fine to remove scale from forging. Use the higher strength type. It ranges from 6% to 10%.

Even better is sodium bisulphate, AKA Ph-down. Make a 10% solution of one cup to a gallon for pickling steel. It will dissolve scale and oxides. Decarb will be easier to grind off pickled steel. It is also great for pickling copper/bronze/brass fittings after brazing or forging. It is what jewelers use to clean gold and silver after soldering and other torch work.

 

[Seedy Lot]

I did a 52100 batch last month with a normalizing and DET anneal. 12 blanks all wrapped in one big foil packet.

 

[Stuart Davenport Knives]

Just to reiterate what Stacy said, decarb and scale are not the same thing. Scale will come off with a vinegar soak, but decarb is actually a surface layer of carbon robbed steel. The only way to get rid of decarb is to either stop it in the first place (SS foil works excellent for this, and coatings like ATP-641) or grind it off afterwards. When removing decarb by grinding, the most important part of the knife that needs attention is the actual edge. The sides/bevels/flats/spine should all be ground a bit if decarb was a problem during heat treat, but the edge is the most important part.

Sometimes you might notice a knife will not hold an edge as excpected when new, but a few sharpenings later the edge retention goes up. This is primarily due to one of two things, or both. Decarb was not properly dealt with or the edge was overheated during powered sharpening.

As I understand it, "scale" is actually the carbon that came out of the steel.

 

[Alex Topfer]

As I understand it, "scale" is actually the carbon that came out of the steel.

Nope, it's mostly Fe3O4. The carbon burns off at these temperatures, into CO2

 

[Pinoy Knife]

i know a white vinegar soak used to clean my steel very nicely after forging...
i always soak my high carbon blades in it after heat treat and the clean up is much easier....
like you don't have to grind away very much for clean metal again...
yet very seldom does this get mentioned...

 

[Alex Topfer]

Here's an example of the difference between scale and decarb on one of my kitchen knives

I've always found that just grinding and wire wheeling removes all the scale that I'm worried about. And i don't want to forget a blade in acid for 6 months

 

[Stuart Davenport Knives]

After questioning myself on what scale actually is and doing some research, I found this.....

"Mill scale, often shortened to just scale, is the flaky surface of hot rolled steel, consisting of the mixed iron oxides iron(II) oxide (FeO, wüstite), iron(III) oxide (Fe2O3, hematite), and iron(II,III) oxide (Fe3O4, magnetite)."

So it isn't carbon, but rather a mixture of different types of iron oxides. Learn something new every day!

 

[Taz]

I use 321 foil packets for normalizing/annealing/DET annealing carbon blades. I make a pouch, put all the blades in it, seal it and leave them in throughout those processes. When I am ready to austentize, I use ATP641 on the blades. I found out the hard way that 80CRV2 decarbs a LOT during a normalizing/thermocycling and DET anneal. Went from .135" thick to .090" to get the decarb removed fully! My kiln was super slow to rebound, so they were in a lot longer. The new HT oven should be better!

I have tried the graphite spray stuff and it helps if just doing austentizing and no other cycling, but I started cycling my steel regardless of forging/stock removal to get consistent results.