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).
On special steels for casehardening by nitrogenisation, comparing their composition to standard nickel chrome steel.
| Identifier | ExFiles\Box 154a\1\ scan0079 | |
| Date | 19th June 1928 | |
| SPECIAL STEELS FOR CASEHARDENING BY NITROGENISATION. Further to BY1O/G.14.6.28. on the above subject whilst in my memo quoted above I have given a brief resume of the steels for the above purpose, in this memo I propose to compare them with our present steels so far as my information goes in order to make clear their possibilities and limitations. I should have pointed out that the "nitrogenezing" steels have to be submitted to a heat treatment to attain the necessary physical qualities in a precisely similar manner to our standard 3½% N. or crankshaft type of nickel chrome steel, and that having been heated to 860°C and quenched in water (not oil as with the general types of alloy steels) and tempered at 500°C they are then heated in an atmosphere of N H3 at 500°C for 24 to 48 hours according to depth of hard skin required, they are then allowed to cool out in the furnace where the N H3 atmosphere is carefully maintained until the steel has dropped to approximately normal air temperature. The patent specification covers a range for aluminium of .50 to 2.00% which can be used in varying proportions with a wide range of other elements, in fact almost any alloy steel can be more or less affected by the "Nitrogenisation" treatment, but the latter is maximum in its effects with about 1.00% aluminium. Strength and other qualities are obtained by varying the alloying elements as one would naturally do for a Nickel Chrome steel in the absence of the aluminium. A comparison of a crankshaft steel as at present used by us, with an actual sample of the above gives the following results :- COMPOSITION. *N* Steel. Carbon .43% Manganese .09% Silicon .13% Nickel .10% Chromium 1.39% Aluminium 1.02% Standard Nickel Chrome. Carbon .34% Manganese .60% Silicon .20% Nickel 3.5% Chromium .66% Aluminium Nil. | ||