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).
Laboratory report on a fractured car spring, concluding the cause was incorrect heat treatment.
| Identifier | ExFiles\Box 76\3\ scan0114 | |
| Date | 28th February 1920 | |
| R.R. 235 a (100 T) (S.F. 846. 6-8-19) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2460. Mr. Hives. C 134 H16/EB28.2.20. Laboratory. 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. | ||