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).
The results of cyanide heat treatment and hardness testing on steel, including conclusions.
Identifier | ExFiles\Box 154a\4\ scan0059 | |
Date | 7th December 1937 guessed | |
-4- After 15 mins. Cyanide treatment and. direct quenching from bath, Surface 504 "Core" 480 Surface +24 After 30 mins. Cyanide treatment and direct quenching from bath. Surface 519 "Core" 481 Surface +28 The results of further tests are shown in a series of graphs in the second blue print. It is important to note that both the figures quoted above and the graphs very considerably underestimate the differences between the surface and core hardnesses, and must be regarded only as an illustration of the effects of the two methods of the heat treating. This is because it is necessary to remove at least .002" from the decarburised surface to obtain a finish suitable for hardness testing. This leaves only .002" of decarburised surface. Also we found that consistent results were best obtained with the 30 Kg. load and 1mm ball. Under these conditions accurate measurements of the hardness of the surface layer is impossible. CONCLUSIONS. (1). The method of finally grinding and polishing still remains the most certain way of maintaining the full fatigue resistance of the steel used. (2). It is possible to restore the carbon in the decarburised surface of an unground spring by a comparatively short cyanide treatment, and this might be effective, provided a secondary loss of carbon in heat treatment can be avoided, and that adjustment of the carbon content of the surface to overcome possible variations in the initial decarburisation does not introduce fresh difficulties. It is also necessary to consider the harmful effect of oxide inclusions and similar surface flaws which this method does not eliminate. H1/EJW. | ||