From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
The material specifications and physical requirements for gun barrels and breech blocks.
| Identifier | ExFiles\Box 170\4\ img015 | |
| Date | 17th July 1940 | |
| OY. from Rm.{William Robotham - Chief Engineer} Rm{William Robotham - Chief Engineer}/FJR.1/ML.17.7.40. GUN MATERIALS. The barrels and breech blocks of both the 40 mm. and the 13.2 mm. guns are to be in E.S.C's Vibrac V.30. The nearest American steel is S.A.E. 4340. Below are the compositions of these materials, together with Vibrac V.45. | | VIBRAC. V.30. | VIBRAC. V.45 | SAE. 4340. | |---|---|---|---| | Carbon. | 0.27 - 0.35 | 0.38 - 0.45 | 0.35 - 0.45 | | Silicon. | - 0.30 | - 0.30 | - | | Manganese. | 0.5 - 0.7 | 0.5 - 0.7 | 0.5 - 0.8 | | Nickel. | 2.3 - 2.8 | 2.3 - 2.8 | 1.5 - 2.0 | | Chromium. | 0.5 - 0.7 | 0.5 - 0.7 | 0.5 - 0.8 | | Molybdenum. | 0.55 - 0.65 | 0.55 - 0.65 | 0.3 - 0.4 | The physical requirements for the 40 mm. barrel and breech block are :- Proof stress = 50 tons sq/in. Maximum tensile stress = 70 tons sq/in. Elongation = 12% Impact in transverse direction = 14 lbs/ft. In the case of the 13.2 mm. gun the barrel is less highly stressed and the heat treatment should be such as to give 45 tons sq/in proof stress and 65 tons sq/in maximum tensile stress, with correspondingly higher values for the elongation and impact. - Continued - | ||