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I finally nailed down a deal on a 1928 Sterlingworth in very nice shape. 6lbs 2oz. #3, 28", M/F barrels. The barrels are marked Sterlingworth Fluid Compressed Steel. What are the differences in these barrels, Chromox and Krupp?

TIA

the markings...

Interesting question and timing Bill. I dropped 2 "Armory Steel" barrels at METL today (Crescent and Meriden Fire Arms) for composition analysis by Optical Emission Spectroscopy (OES). Crescent advertised the barrels as "Decarbonized Steel" into the 20s.
Dave Suponski published an analysis of Parker Steel, Titanic Steel, Vulcan Steel, and Trojan Steel in the Summer 2014 Parker Pages, and Walt Snyder has shared the results of an Ithaca barrel tested in 1919. I also have the published composition of a number of early Fluid Steels including Winchester Nickel Steel, Halcomb Steel Co. Nickel Steel, and several Krupp variants.
Most early Fluid Steels are AISI low carbon steels, 10XX variants. Krupp Fluss steel and Krupp Spezial are AISI 1060 and 1045.
Turns out Parker Steel is Resulphurized Decarbonized Steel, likely "rolled" for added strength like Winchester Standard Ordnance Rolled Steel.
Anyway - until we actually OES a bunch of vintage barrel segments, we won't really know what they are. What we could have done, and known, with all the chopped off barrel ends!! For the record, I'm still collecting fluid steel segments IF we know the name on the barrel.

RevDocDrew,
Good evening.
I would have thought that the Krupp and Chromox were more along the lines of a 4130/40 with a higher chrome content than a 1045 with a tensile of something like 100k. Wishful thinking.
The 1045 makes sense for actions where you are going to case harden. Just thought barrels would be better steel than that.

I may have a stub off of a nitro special at the shop if you want it.

1045 is too high in carbon for general case hardening. 1045 is a through hardening carbon steel. In the L C Smith Plans & Specifications book a matl spec chart is given. Both the frame & barrel specs show a 1020 steel. However under the Feather Weight drawings the drawing for the lug denoted a forging of 1020 steel but notes the barrel as approx 40 carbon, with actual grade not given.
This drawing is dated to Feb 19, 29. My guess is that at some point smith increased the carbon content of their barrel mat'l to give a "Harder" barrel.
Most case hardening was done on mat'l having no more carbon than around 20 points.

Thank you Miller; I missed that. Is there a date on the 1020 Spec. Chart?

I would VERY much like to composition analyze samples of Hunter Arms Royal, London, Crown & Nitro Steels.
The Armor Steel sample was comparable to AISI 1045 Plain Carbon Steel, but with slightly higher sulfur (.075) and phosphorus (.112) content similar to AISI 1211 rephosphorized and resulfurized steel.

Walt Snyder graciously shared a 1919 Ithaca Gun Co. letter from A.P. Curtis, General Manager requested tensile strength testing on a section �cut from a barrel made in Belgium� to be performed by E.J. Stormer of Racine, Wisconsin.
The letter did not indicate if the barrels were �Smokeless Powder Steel� used on the Field grade, also commonly found with the �LLH� mark of Laurent Lochet-Habran, �Fluid Steel� or �Nitro Steel� used on the No. 1 and No. 1 1/2, Cockerill Steel used on the No. 1 Special, or �Best Fluid Steel� on higher grades.
Tensile strength was reported to be �about 70,000� psi.
Carbon .32%
Manganese .78%
Phosphorus .018%
Sulphur .033%
No molybdenum, chromium, or nickel

This is quite similar to the composition of Parker Titanic Steel.

The �LLH� mark of Laurent Lochet-Habran has been found on L.C. Smith Royal, Armor, London, Crown and even Nitro Steel barrels (on an Eagle Grade) from 1914 to 1948, Hunter Arms Fulton and "Gladiator" & "Ranger" for Sears, and also Fox, Ithaca, Lefever, Crescent, and Baker guns. This composition MAY therefore be that of the Belgian �rough forged tubes� used by most U.S. makers.

The 2 or 3 still interested in all of this will recall that 'Zircon' resurfaced last Spring, and he still has about 40 Pattern Welded and Fluid Steel barrels to be tested. My sincere hope and prayer is that they don't end up in some recycle bin if something happens to him.

A lot of sterlingworths have Belgium makers marks on them. Bobby

Drew;
No date given on the material specifications chart. It is on page 204 in my book. Item numbers are given linked to the Feather Model section of the book. The "40 Carbon" is on the part drawing for the barrel lug in this section, page 21. It gives dimensions etc for the lug with a note of the barrel being of "Steel App 40 Carbon" & does carry the '29 date. On the assumption that both of these numbers are correct but reflect different points i time then my thoughts are the 1020 would have been earlier than the "40 Steel". This was most likely still a 1040 steel or similar. Once the steel got up to about a 1025 special process were required for carburizing (Case Hardening) as the core would also harden & then have to be drawn to prevent brittleness which killed the effect of the extra hard case. According to an old Machinery's Handbook tempering of low carbon carburized steel was recommended at 250�F to 325�F.

The term decarburized steel may come from the process of making steel from cast and wrought iron which have very high carbon content.

I believe I recall that barrels on Remington 1889's were marked decarbonized steel.