Laboratory report on a fractured car spring, attributing the failure to incorrect heat treatment.
| Identifier | ExFiles\Box 80\2\ scan0087 | |
| Date | 28th February 1920 | |
| Mr. Hives. E.F.C. C to By. {R.W. Bailey - Chief Engineer} X.2628/B. H16/EB28.2.20. Laboratory. X.2628 Re Car Spring you sent in about three days ago. (no covering note received up to the present). The steel as received was found to be harder than usual, i.e. 460-470 Brinell hardness, and we think that this in conjunction with a rather high first quenching temperature is the principal cause of the fracture. It was also noted that the steel has a rather rough pitted surface in parts; this may have had an influence in starting a crack, and such is what might be expected in the case of an exceptionally hard material. The steel has a composition which is fairly normal though somewhat on the hard side, viz. Carbon .59%, Chromium .78%, Manganese .38%. On tempering to a further extent so that the Brinell hardness was brought down to 415, there was a decided improvement in the appearance of the fracture, and this could be further improved by a complete re-heat treatment. It may be concluded from the above that the trouble was primarily one due to incorrect heat treatment. A micro photograph showing structure as received herewith. HCH. [STAMP: EXAMINED MAR 24 1920 P.T.A] [STAMP: RECEIVED] R.R. 235A (100 T) (S.F. 846, 6-8-19) G. {Mr Griffiths - Chief Accountant / Mr Gnapp} 2460 | ||
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).