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).
Letter from English Steel Corporation regarding steel specifications for the 40 mm Gun Mk III barrel.
| Identifier | ExFiles\Box 176\3\ img134 | |
| Date | 8th September 1940 | |
| COPY OF A LETTER RECEIVED FROM:- THE ENGLISH STEEL CORPORATION. HHB/MA. Research. 8.9.40. Messrs Rolls Royce Ltd., DERBY. Dear Sirs, re 40 mm. Gun - Mk III - Type BD.{Mr Berend} We have to acknowledge your letter of September 5th. in connection with the steel employed for the manufacture of barrels for the above gun. We note that the question of making these barrels to "OC" specification has arisen and we would point out, in the first place, that the composition of the Vibrac steel we have used for the gun forgings made so far falls definitely within the range specified in both Admiralty and War Office specifications, which include the "OC" grade. On the other hand, the tests specified for "OC" steel are in our view much too high in minimum Elongation and Izod test in relation to the requirements of other specifications such as "NN", which has a minimum yield point 10 tons/ sq. ins. lower than "OC". We definitely consider that the size of the forging required for the Rolls Royce gun involves too much forging reduction to enable full specified figures for "OC" specification to be met upon a production basis, and if 50 tons minimum yield point is sufficient for your needs, we would much prefer to work to the specification which was arranged between us in the first place. We would mention that we raised objections to the "OC" specification when it was first issued, and received what was described as a concession down to 12% in the Elongation, but in spite of this the copies of specifications issued subsequently still contain a requirement of 15% minimum, which we consider to be ridiculously high for forgings of small diameter. Yours faithfully, English Steel Corporation. H.H.Burton. | ||