Steel Oxide Composition and Thickness Measurement

Good find. I'm force to award you a tomato GA.

I wonder why this company has no engineers on staff?

Thanks.

There seems to be a lot of people that just decide to go into a particular business on a whim, and then set about figuring out how to do it as they go along.

Can I turn my tomato into a spicy red beer?

As you are likely aware from previous answers, the colors of the steel are caused by optical interference related to the thickness of the oxide layers. There are important variable that can influence the oxide thickness. You have already been told of steel composition variables. Oxidizing gas composition, gas flow rate, temperature variations, etc. are a few of the others. Your task is to monitor the color variations and observe how they track the variables you measure. Your problem will then be solved.

You did not mention if this is an electric furnace, or a fuel-fired furnace. Obviously, if fuel-fired, the exact composition of the oxide produced (assuming you know the composition of the wire rod) depends on an oxidizing or reducing condition in the furnace. If I have to explain that, then you need to go back to school.

Other parameters include residence time in the furnace, temperature control band, etc. Watch out the for the etc. Your oxides might in fact only be different thickness of oxide, the colors are partially due to absorption of light, but thin films can result in light interference for various wavelengths that result in "newton colors". Something like anodizing on aluminum.