Parker Fluid Steels and Finish

[Bruce Day]

There has been discussion about differences or non differences between Parker fluid steel barrels.

Here are two barrel sets, one a Titanic ( D ) 20 ga and the other a Rem Cro-Moly ( C) 16, the larger diameter one obviously being the 16. These were refinished identically and at the same time, using the same grit and polishing steps and the same bluing tank. I switched positions on the barrels for photos so as to catch the same light and negate any light differences.

I'll add another set of photos with Parker Steel barrels.

[Dean Romig]

They both appear to exhibit the same luster. Not surprising given that they were refinished in the exact same manner. We know that they are made of entirely different steels and I wonder what we can take from this comparison knowing they are not in their original finish?

Have the original longitudinal striking marks been eliminated from the Trojan barrels due to the recarding?

[Fred Verry]

Bruce, are you saying the two barrels were blued for the same length of time, temperature, humidity, and the same batch of chemical compound by the same person?

[Bruce Day]

Bruce, are you saying the two barrels were blued for the same length of time, temperature, humidity, and the same batch of chemical compound by the same person?

yes

[John Havard]

Thanks as always for an interesting post Bruce. To my untrained eye it appears that one set of barrels is less well polished (more coarsely polished) than the other. But given the fact that they were prepared precisely the same what else could the difference in appearance be attributable to other than the steel? Interesting.

[Bruce Day]

John, they were polished they same. Some barrel steels take a higher degree of polish than others. I suppose it has to do with the grain structure. In this example, the Titanics (20ga) polished better than the Rem Cro-Molys( 16ga) , to my eye, and apparently yours as well. Others may not see any difference.

Unanswered is whether these Titanics are representative of all Titanics, etc. I suppose same spec barrels can differ by batch and have the same constituents.

[edgarspencer]

I suppose same spec barrels can differ by batch and have the same constituents.
You're right, Bruce, but the key word is 'spec'.
Industry specifications for all alloys of steels, and stainless steels give ranges for each off the roughly 8 principle elements, other than Fe (iron), which makes up the remainder. They are Carbon (C) Silicon (Si) Manganese (Mn) Chrome (Cr) Nickel (Ni) and Molybdenum (Mo). Phosphorous and Sulfur, always reported, are kept as low as possible and are in the .015% range.
Carbon ranges for the Cr-Mo, Cr-Ni-Mo, and, the later developed Cr-Mo-V (vanadium) go up from lows of .12% to over .40% as strength requirements dictate. In most all low alloy steels, Fe ranges from 94 to 97%, so regardless the alloys name, it's still a lot of iron. What does iron do? It rusts.
In it's natural state, Carbon doesn't mix well (go into solution) but as controls increase in heat treatment, carbon is more finely dispersed, though always visible at grain boundaries when photo-micrographed. As critical as the temepatures in the heat treat cycles, the method and rate of cooling from those temperatures is equally important. The more quickly the steel is cooled, the better the carbon is trapped in solution, and not migrated dback to the grain boundaries.
Bruce, your assumption that grain structure plays a major part in the finish appearance of cold rust bluing is correct. While the iron content seems to vary very little, maybe 3%, it too plays a significant part in the cold rust process. Also, as Cr, Ni and Mo play a big part in corrosion resistance (rust is corrosion) they have an inhibiting factor in the cold rust process. In the end though, Iron (Fe) wins. (Iron looses when Cr, Ni and Mo gang up on it when those three elements make up up to 30% of stainless steel)

[Eldon Goddard]

Reading Mr. Spencers post is like a refresher coarse in metallurgy. Just as long as I do not have to study those phase diagrams I enjoy it. I am guessing you worked in the steel industry.