Reproducing mill scale

I'm looking for information on how mill scale forms during the
steel-making process (i.e., the atmospheric conditions, mechanical
processes, heating and cooling profiles), with the ultimate goal of
being able to recreate mill scale in a small shop/studio environment.
The reason for this is that I would like to incorporate the look of
mill scale in some of my sculptural work, but the processes involved
in creating the work tend to destroy or degrade the original scale. No
other coatings or processes I've encountered yield quite the same
color, texture, uniformity, and overall look of mill scale. Any
thoughts or suggestions?
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Boy, I get lots of scale when I put steel into a propane forge! Do you know any blacksmiths? Heat the steel to cherry red in air - that oughtta do it. Actually, that scale isn't quite as tight as mill scale.
What I have done also is to do blending with a sandblaster, using a very light sand sweep. However, your cosmetic requirements are likely to be tighter than mine were.
Bert wrote:
Reply to
Grant Erwin
I share studio space with a blacksmith, and do some smithing myself, but the scale from the propane forge isn't nearly as uniform nor quite as adherent as mill scale, and it doesn't have the same color. I suspect the former may be due to the turbulence, hot spots, etc., that occur in a small forge, and the latter may be due to oxygen concentrations and heating profiles, but that's just a guess at this point.
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I have heard that propane forges don't produce the same type of scale as a coal forge (something along the lines of less contaiminents in propane). So if the blacksmith is willing to try purchase a coal forge you might be able to get the type of scale you are looking for (though he might know someone with a coal forge that you could just borrow). Ken
Reply to
Ken Vale
Ken Vale wrote: I have heard that propane forges don't produce the same type of scale as a coal forge (something along the lines of less contaiminents in propane (clip) ^^^^^^^^^^^^^ How about throwing some lumps of coal in the propane forge, to introduce the desired "contaminants?"
Reply to
Leo Lichtman
Put it outside, build a bonfire around it of hardwood, completely cover it in the coals as it burns down. Take video/pictures of the fire and it becomes perofrmance art.
Reply to
Nicholas Carter
Boy's A rose by any other name. Mill scale is black iron oxide, ie. FeO. It occurs when iron or steel is heated above approx. 1000?F. in the presence of excess oxygen. Above 1500?F scaling can be very rapid. I know what you are trying to accomplish Bert. Anyone who fabricates with steel and wants to maintain natural mill scale surfaces has a problem. I have a friend who used to make steel furniture and even though he used welders and grinders he was able to obtain an evenly scaled final surface. You might not like this solution but it does work. You need to have a box furnace big enough to hold the work. As the final process, the entire object is heated slowly & evenly to a temp of about 1200?in a slightly oxidizing atmosphere then held there for several hours followed by a slow cool down. An exact heating cycle would have to be by trial and error. Temp, time, and atmosphere are the key variables. I have tried "touching up" disturbed areas with a rosebud heating tip with mixed results (mostly unsatisfactory) If your work is large you better find a friend that works at a steel mill or a heat treating plant. Good luck dude,
Glen G.
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