I'm curious what the burnt orange deposit is that I get on my steel in addition to scale. I did a search here, so if this topic has been beaten to death in the past I apologize. 

rust

 That was my first thought, but it looks different. I'll take your word for it. 

I’m no expert but I’ve seen some orange colored stuff on the coal in the forge right after burning coal from the stigler Oklahoma coal mine, but I’ve never seen anything transfer to the metal. Steve is likely right its probably rust though,  Do you have a picture of the orange deposit? 

More precisely, iron oxide in the form of Fe₂O₃ (rather than the Fe₃O₄ that makes up forge scale), also known as hematite. Rust as such is a combination of hydrous iron oxide (Fe₂O₃·nH₂O) and iron oxide-hydroxide (FeO(OH), Fe(OH)₃).

Here's a pic. This is on the outside of the scale. 

I have seen the same thing a few times and always assumed it was rust.

Looks like rust to me.

I wonder why it only happens rarely. Why is scale so predominant in forging and rust is predominant at low temperatures. I need to do some research. 

I think it has something to do with humidity. Look up flash rusting. I see it when working on muzzleloaders. Pretty good info here.

https://www.canada.ca/en/conservation-institute/services/training-learning/in-person-workshops/understanding-flash-rusting.html

Note when asking such questions is is nice to tell HOW you are getting that.  Using an induction forge in an inert atmosphere is different from using a coal forge which is different from using a charcoal forge which is different from using a propane or natural gas forge. YOU know the details we don't!

Lower temps scale less rapidly than higher temps; DEPENDING on the oxidizing/reducing atmosphere of the forge.  Hematite is the red rust and Magnetite is the scale/black rust  (Magnetite can rust to hematite in a moist oxygenated environment.)

Do you use water on a coal fire or quench in water?

Also, if you're using a gas forge with a neutral flame, the byproducts of burning propane are carbon dioxide and water vapor.

And nitrous oxide to a lesser degree if the flame is hot enough. Nitric acid leaves brown-orange stains.

Frosty The Lucky.

Sorry I didn't get back to you guys sooner. I'm using a propane forge and I try and keep the flame neutral, but things change as it gets hotter.

I think Frosty's idea is probably close if not right. I have never seen scale rust. I've collected magnetite (fe3O4) on the beach. After a storm all the white sand washes away and the beach is nothing but black sand. If salt water won't rust it...

This stuff appears more as a deposit than a reaction. Now that I think of it, it accumulates mostly on the parts of the steel which are exposed to the flame. It's also most prevalent when the forge is heating up.

I'll keep an eye on it to more accurately note the conditions. 

DARN, you aren't using coal! There goes my theory about palladium in that coal vein. Hmmm, maybe in the refractory in your forge? Palladium oxide is orange and if it were dissolved in the water or adhering to the surface of the pieces it'd make sense for it to form replacement deposits. 

There's also no telling what was in the scrap stream when they made the steel, I've had batches that show copper staining in some situations. 

Frosty The Lucky.

Looking at your photo, I’m guessing that you’re getting flash rusting in the places that don’t have scale adhering to them. 

I've watched this stuff accumulate on the scale while a piece is reheating.

I tried to scrape some off to see if it was magnetic. Unfortunately the layer is quite thin and all I got were bits of scale. I wiped some off with a towel and it was unaffected by a strong magnet. The sample was so small that it wasn't conclusive, but I couldn't get any movement at all, even on small threads that were covered in it.

I dunno. It's probably just some deposit from the propane. 

 

It forms while the piece is heating in the forge? That sounds like you have lime/calcium in the water and a residue is oxidizing in the fire. 

Frosty The Lucky.

 

JHCC hits it on the head. It happens in a forge too.