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).
'Macrome' steel treatment, its success on valve springs, and plans for further testing on engine components.
| Identifier | WestWitteringFiles\W\May1931-August1931\ Scan085 | |
| Date | 6th August 1931 | |
| Hs{Lord Ernest Hives - Chair}/CHP1/AT6.8.31 contd. -2- It is claimed for the "Macrome" treatment that it causes complete normalization of the steel, for greater in extent than can ever be achieved by heat treatment, hence the resistance to fatigue is considerably increased. With regard to valve springs, the "Macrome" system has been very successful on the "Jaguar" engines used by Imperial Airways. On these engines a great deal of trouble had been experienced through broken valve springs, but since "Macrome" tempered springs were fitted eight months ago, not a single breakage has occurred out of more than four hundred springs. The steel used for these springs is of straight carbon specification, thus :- Outer spring. Inner spring. Carbon .77% .85% Silicon .24 .40 Manganese .35 .288 Phosphorus .024 .023 Sulphur .014 .010 Blued at 350°C. Concerning the treatment of our own valve springs in chrome-vanadium steel, Mr. Prist assured me that it would be equally beneficial, but he was careful to point out that the treatment would not, of course, remove any slight flaw caused by a particle of chrome-oxide which might be present in the steel. It is on account of this risk that Mr. Prist considers a straight carbon steel more reliable for springs. A set of "R" engine valve springs have now been "Macrome" treated, and are awaiting test. This set consists of groups of springs which have undergone slight variations in treatment, one of which groups will probably be superior to the rest. This trial and error method is necessary before the correct treatment for a given steel can be determined. It was pointed out to me that the "Macrome" treatment improves the wear resisting properties of almost any steel component; supercharger gears were mentioned as being likely to benefit by it. When submitting any component for treatment it is necessary to supply a complete specification of the steel. I was shown numerous letters from well-known firms confirming the claims made for this tempering treatment. Hs{Lord Ernest Hives - Chair}/C.H.Parkinson. | ||