3" Naval Ordnance Steel and Its Hardening Process

[gunsonwheels]

I purchased a 3" naval barrel in 1973 and had a friend at a tubing supplier cut it into sections to use for sleeves.  Wore out a few blades doing it and the end faces looked like tree growth rings though much courser.  I tried to machine out the rifling and after chewing up everything from high speed to cobalt to carbide to ceramic, I took it to a heat treat place to be annealed.  The fellow there had worked for Watervliet during WWII and kinda lit up when he saw the piece... he identified the alloy as 4357 (a chrome molybdenum steel with 57 points of carbon) and said after rifling them they left lugs or fittings on both the muzzle and breech ends.  To wit was attached hoses from high pressure hydraulics which pulsed the tube from zero to 60,000 PSI at about one pulse per second a day or two.  The result is the tube is stress hardened from the inside out and the "growth rings" represented very hard rings of steel (lots of martensite) interspersed with softer metal (more austenite).  The bores were as a result were glass hard resisiting abrasion and wear while the overall tube remained comparitively flexible.

Three sections were purchased: 1) a breech end for an 1841 six pounder, 2)one muzzle section to be used for sleeving up a couple 40mm tubes ( to a 2/3 scale 1861 Parrot and a .61 scale 1841) and the last one I hoped to use for the liner of a full scale 1861 Parrot.  Between the nasty metallurgy and buying a lathe too small for that stuff it all went back to the scrapper.  If anyone out there has any of this it must be annealed or normalized (not just stress relieved) before trying to machine it into a CW cannon's rifled liner (the rifling is actually pretty close to James rifling config. used in his tubes and was also cut into a few 1841's).  Most of the full scale guns that show up in Casper, WY  are made from such stuff... how I don't know.     

[moose53]

I also bought some 3in-50 navy barrels with chrome rifling in the 1970s . Did not seem to have the same problems truing up the ends and removing of rifling to prepare for breech plug. It is very sad to hear of a barrel getting cut up into little sections .

[Cat Whisperer]

Interesting process.  That verifies the hardening of steel from repetitive shootings (in this case hydraulic pulses).

A company here in town makes bi-metalic tubes.  4140 stock is cored, then a propriatary granular metal instered inside, plates welded on the ends, put into a kiln and rotated.  The mix melts and provides an even coating of a very hard surface.  Tubes are then honed smooth.  They are used for injection molding machines.