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).
Crankshaft steel compositions (LK.3 and GK.5) and the importance of post-nitriding polishing processes.
| Identifier | ExFiles\Box 146\1\ scan0117 | |
| Date | 2nd December 1937 | |
| ST.I/ST.2.12.37 - 2 - Monsieur Billardeau then went on to say that what is used almost entirely in France as a crankshaft composition is what is known by them as LK.{L. King}3, the British specification of which is to be found in an Air Ministry General Specification N°.D.T.D87, issued in March 1930. I understand, however, that in their particular case, they delete the nickel. This gives a Vickers Brinnel of 1100. He pointed out however that, in certain cases where the Vickers Brinnel of 1100 was not so essential as other qualities - in other words when such a high hardness figure was not required, what is known by them as GK.5 was utilised. The British specification of this is also to be found in Air Ministry Specification N°.D.T.D.306 of April 1937. This gives a Vickers Brinnel of 800 and Messrs. Aubert & Duval consider this to be a very fine composition for crankshaft purposes. I enclose both the LK.{L. King}3 specification, as per above, and the GK.5, which is a copy given to me by Monsieur Billardeau. He further went on to tell me that he wished us to appreciate the vital importance of high polishing the crankshafts after they have been nitrided, going on to say that, in the case of LK.{L. King}3 more so than GK.5, crankshafts were often rectified after the process of nitriding had taken place. By this he meant of course that a minute surface was removed by rectification after nitriding, to ensure a highly polished surface and the absolute removal of the outer crust which, from very long experience, they discovered to be apt to come away in a powdered form during the use of the crankshaft and, in this powdered form, drops into the oil flow coming from the crankshaft to the bearing metal and, as you can imagine, manufactures a perfect grinding substance which could do no end of harm both to the crankshaft and to the bearing material. Please take all this information as coming from one whose only desire is to help where he can. As I repeat, you no doubt know all about these various compositions, but the information obtained having come from someone who is recognised in France as being at the head of a most important steel producing Company and the pioneers of the nitriding process, I feel somehow that one cannot overlook these remarks. I should personally be very interested to have your views on these remarks. Sr h P.S. I should like to lay stress on the fact that Monsieur Billardeau was very insistent on the bad effects, from the nitriding point of view, of nickel in the composition of steels required for nitriding purposes. He seemed to lay stress on the use of aluminium, which does not appear to be employed where our crankshaft metal composition is concerned. I enclose a catalogue which may be of interest and will be pleased to find out any further particulars you may require. h | ||