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Steve may be proved correct regarding pattern welded barrel strength. Both English machine forged Skelp (Twist) and Belgian Pointelle' Twist were in the middle of the pack in the 1891 Birmingham Proof House Trial
http://docs.google.com/a/damascusknowled...TEK8OtPYVA/edit

Good stuff to know AISI 1084- close to the AISI 1090 steel that Ka-Bar uses and did even in WW11 for their famous sheath knives adopted by the Army and USMC in 1941-- Wonder what the steel analysis of the Fairborn-Sykes "Commando" knife used by the Limey Force 316- see "Bridge On The River Kwai" etc- later the British Royal Marine Air Service was- different shape, no fuller. full hilt- great fighting tool for "up close and personal" work indeed.

Progress report and another image; 20X Nitrol etched



Steel above and below, with iron in between.

From Adam:
The globular shape of some of the inclusions looks like molten (cast) material, but with our better prep technique and some EDX work the inclusions appear to be mixture of silicates, oxides, and carbon (not just graphite). This is more indicative of wrought iron (or what we call wrought iron today). The chemical analysis we measured also had 0.01 weight percent C and I would expect to see something closer to at least 1.5 weight percent if it were truly cast iron (by today's standards). I suspect they used whatever was at hand that they called iron (wrought or scrap perhaps). I wonder if perhaps they used the terms "steel" to denote an alloy with controls on the individual elements and "iron" to indicate whatever else that was iron based.

I'm meeting with Adam again Weds.

Drew,

Hope your mission trip to Guatemala was productive and rewarding!

This information from Adam is very interesting! I question the carbon content stated in your text. 0.01 carbon content would be virtually nil. Is it possible that the decimal point is off one place? Maybe the correct number should be 0.1?

Still, I am surprised that the average carbon content is so low as 0.1. Though, I would not argue with the analysis. My SWAG estimate would have been 0.3 to 0.4.

From what I have read in old metallurgical books, they were quite adept at controlling the carbon content in steel at the time damascus barrels were made. 0.5 to 0.6 carbon content is sufficient for making springs and cutting tools. They were aware of the difficulties of heat treating hypereutectoid steels, so typically avoided making steel with more than 0.8 carbon content. Given this information, I have assumed that the carbon content of the "steel" element used in gun barrels to be around 0.6 to 0.8 carbon content.

Greener wrote that the steel to iron ratios were typically at least a 50/50 mix in English made barrels. And usually, the steel percentage was higher than the iron. Assuming a 50/50 mix of steel and iron, and knowing that carbon migration would happen at the elevated temperatures of forging, I would have made the guess that the average carbon content of gun barrel steel would be in the 0.3 to 0.4 range. This however, may only apply to English barrels. Without information on Belgian barrel steel, it may be possible that the Belgian steel could have been lower in carbon content. It would be interesting to see a chemical analysis on an English barrel, to see if the average carbon content is higher.

I was kind of wondering about that decimal point also. Great picture also Doc Drew, possibly higher magnification than 20x. Do the folks at the lab think that's a view of the grain in the steel component.

Seems most of Adam's comments were about inclusions, with none of them likely to contribute to the strength of the barrel. I'd still wonder if the labor was put in to overcome the shortcomings of the material.

Maybe, mono steels needed to be reliable and cost effective before taking over. Might be too that alloying became more important than just upping the carbon percentage.

Drew,
A.H.Bogarbous in his book, "Field Cover an Trap Shooting", pages 426-431, records a visit to W&C Scott In which he comments on Scott's method of manufacturing Damascus barrels.We learn that the key ferrous ingredients used were old coach springs and rusty anchor chains. This would likely result in a mixture of Wrought Iron and a carbon steel with a C content of approx.;0.5%.The report also states that following extensive sorting and cleaning of the scrap the net yield of good metal retrieved for best barrels was 20% and that the resultant cost was very high at 70 - 80 pounds per ton.
Based on this report it would seem reasonable to suppose that English Damascus made from Scott,s feed stock would have a carbon content in the .2-.3% range
I am also aware, that faced with soft barrels ,[low carbon content] the old barrel makers quote, "densified" the barrels by cold hammering to increase strength and hardness. Which today we realise had the effect of raising the yield point[but not the ultimate strength] and hardness of the barrel material.

As always, thanks to everyone for the thoughtful posts.
Dennis Potter graciously provided two 3 rod 'Oxford' Damascus barrels from English gun makers for tensile strength testing, but the tubes are very likely of Belgian manufacture.

Another valuable meeting with Adam. What follows is the non-technical non-deep thinkin' Baptist version

1. Adam confirmed the .01 carbon weight percentage.
2. The barrel did not fail by an intrinsic defect but by a single high pressure event ie. NO LOW CYCLE FATIGUE and NO INTERLAMINAR RUST.
3. The inclusions are slag and when lined up, can be the site of micro-fractures. but did not seem to contribute to the barrel failure. The linear structures (mostly in the iron) in the image above were likely formed as part of the rolling process.
4. The barrel does act like a monometal; although the iron bands have greater ductility than the more brittle steel bands. Composition analysis shows significant blending of the base materials.
5. The fracture lines did not, for the most part, follow weld lines.

Thanks to AmarilloMike, I've been reviewing Burrard on barrel bursts and feel confident that he would diagnose the event that destroyed THIS barrel as from an obstruction.

Very nice.

The old major would likely be pleased.

His work proven beyond reasonable doubt near 100 years later using techniques he never dreamed of.

Well done Drew.

I have said it before & I'll say it again;
"IF" you want to learn about Shoguns, don't "Read" Burrard, "Study" Burrard.