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).
Outlining the specific temperature and time for hardening H.R. Crown valves using the nitrogen process to avoid patent infringement.
| Identifier | ExFiles\Box 154a\1\ scan0190 | |
| Date | 9th January 1930 | |
| RHC.{R. H. Coverley - Production Engineer} c.Hs.{Lord Ernest Hives - Chair} c.Sft{Mr Swift}/Mr.Pendlebury. BY/EM6/J.9.1.30. H.R.CROWN VALVES HARDENED BY NITROGEN PROCESS. With reference to the set of valves you are producing in the above material which are having the stems hardened by the nitrogen process, will you kindly note that in order to avoid any infringement of the nitralloy patents it is necessary for the H.R.Crown parts to be hardened at a temperature of 600°C for a period of ten hours. HL. has carried out experiments and finds that the process is satisfactory when carried out at the temperature and for the time stated. BY/EM. | ||