I have NO interest in reviving a vendetta, but am simply trying to give the rest of the story regarding this black stuff



Rib extension wedge left - braze and contamination center - barrel steel right



The composition by EDX of the areas are at the bottom here
http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=546106&page=10

re: "dirty steel". The metallurgical (non deep thinkin') version would be steel contaminated by metal oxides, silicate, sulfide, and manganese sulfide inclusions.

"Scale" is on the surface of forged steel and is black iron oxide, and obviously could contaminate a braze or weld joint.

The comment by the metallurgist last week:
The braze contamination descriptions are kept vague because that's about as conclusive a statement we can make based on the data. The concentrations of iron and oxygen detected could technically be consistent with corrosion (rust) or overheated steel. Based on where it was observed in the braze, we need to refer to it as ferrous braze contamination. We don't know exactly what it is. This could have occurred during the brazing process (likely) and been exaggerated over time by successive heating cycles, moisture, etc via possible alloy segregation effects, electromigration and such phenomena.

By the metallurgical engineer today:
What I mean by dirty braze is that they may have not controlled the environment well or cleaned properly. Also, the braze material itself may have had contamination in it. We can not say for certain but since it is such an old braze.

This doesn't really add much to what several here postulated from the start, but might be of interest. Thoughtful comments/corrections are of course welcome.

Drew, it interests me because I know nothing about metallurgy and barrels. I've learned more on the subject from this thread than any other.

Scale- found also on hot rolled mild steel- in the machinist's trade parlance, it is called "bark"" Cold Rolled steel is Hot rolled that has been "pickled" in an acid bath, and then rolled again at ambient temp--Sulphuric acid and a H2O bath is my guess for the "de-barking" Kingy- 3 things I've studied all my life fascinate me to the 9th Degree- one of them is the science of metallurgy- both ferrous and non-ferrous metals, and the proper techniques of welding same- RWTF

Then you would know what flux is for & what slag is.
Is this slag ?
O.M

Moses: I was hoping someone else would step up, but I'll go ahead and embarrass myself. The "contamination" is unlikely to be slag, which is usually more silica oxides than ferrous (and other metal) oxides. Slag can form an inclusion, but the big inclusion that was likely the initiation point in the subject barrels was gone with the burst pieces; which is why having the burst pieces would have been valuable. We know the steel had manganese sulfide inclusions.

This big inclusion is likely slag



This is a photomicrograph of slag in the fractured edge of a Twist barrel



A welder will have to help with flux.