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 discussing the performance and selection of nitriding steels for crankshafts.
| Identifier | ExFiles\Box 146\1\ scan0128 | |
| Date | 8th December 1937 | |
| [handwritten] 1245 [/handwritten] [handwritten] Poles [/handwritten] [crossed out] BY.10/C.8.12.37. [handwritten] GTE } Please note Pm_ [/handwritten] c. Rm.{William Robotham - Chief Engineer} RE: NITRIDING STEELS. [handwritten] SWDS [/handwritten] Referring to Messrs. Aubert & Duval's letter of Decr. 24th 1936, and the short talk we had on the subject of nitriding crankshafts during your visit to Derby, I have gone over the information submitted which represents the stage through which we passed some several years ago, when we were considering nitriding steels in the first instance. Messrs. Aubert & Duval are the concessionaires for Europe for the original nitriding steel. This, however, had certain characteristics which as the result of work we carried out were proved to be undesirable, particularly the loose skin of excessively nitrided material on the outer surface which we found it necessary to grind away. We carried out a considerable amount of running with shafts made in steel of the type, and roughly the same composition, as that quoted in Messrs. Aubert & Duval's letter sent under cover of Sr.1/ET.2.12.37., but after making extensive tests in our aero engines using lead bronze bearings we decided that the material was not really suitable for our purpose. About this time Mr. Dickenson of the English Steel Corporation Limited, who had spent in conjunction with Mr. Burton considerable time in considering the nitriding steel, introduced to our notice the English Steel Corporation's V.C.M. type. This had the advantage of not producing the loose nitrided skin which we considered to be a defect in the nitralloy type as marketed in England under Messrs. Aubert & Duval's licence, and as a result of experiments carried out on model cranks to check up the durability of the steel under fatigue conditions as produced in an engine, we found that this condition was also better in the V.C.M. type of steel. We have turned out a large number of cars and aero engines fitted with V.C.M. crankshafts, and they have given us practically complete satisfaction. I only know of two complaints that we have had, and in each case the fault was, insufficient nitriding, which could have occurred with Aubert & Duval's steel equally well as with the V.C.M. V.C.M. steel has a brinell hardness on the skin of between 600 and 700. Their Hykro steel which is a further development gives us a brinell of between 900/1000, without the excessive nitriding effect of the outer skin, and this is the material we propose to use in the near future. We do not wish you to submit this letter to Aubert & Duval, as we have no intention of re-opening a controversy which raged some years ago on this subject. | ||