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 production and testing of nitrided austenitic steel Kestrel cylinder liners, detailing issues with hardening and distortion.
| Identifier | ExFiles\Box 179b\2\ img037 | |
| Date | 1st October 1932 | |
| COPY. To Hs.{Lord Ernest Hives - Chair} From HIC. AUSTENITIC STEEL LINERS. We have produced two Kestrel cylinder liners in nitrided austenitic steel, the treatment being carried out by the Sheepbridge Stokes Co. in accordance with recommendations outlined in ET/MR/J.21.6.32. Previously, when producing liners in austenitic steel to be hardened, an allowance was made for grinding or honing to remove distortion after treatment, but for the purpose of this experiment, the bores were ground to finished size and then electro copper deposited. It was expected that 48 hrs. treatment at 600°C would produce hardened surface of .003" deep with a brinell of 800 to 1,000, the actual hardened surface being .002" deep with a brinell of 450, therefore from the point of view of hardness, liners cannot be regarded as satisfactory. There is, however, an improvement in the general hardened surface condition, as previously it was discovered that austenitic liners did not wholly respond to the hardened process, having hard and soft patches. One liner distorted to the extent of .004" to .005", the other being sufficiently free from distortion to justify fitting for running. Distortion was expected and it was anticipated that this could be removed by the use of split wooden clamps, but on account of the localised nature of the distortion and the flexibility of the liner, it has been found impracticable to restore to the original shape. Whilst this method may be effective in the case of plain liners where the section is even and distortion general, it cannot be applied successfully in the case of Kestrel liners owing to the variation in shape and stiffness of section. In order to obtain some idea of the effectiveness of the treatment under running conditions, the liner that had little distortion was fitted to the Single Cylinder Engine fitted with a 6-1 piston, and run for 2 hrs. at full throttle. Some tightness was observed towards the end of the test and upon examination the liner had distorted inwards behind the rubber groove, particulars of which are given on the attached blueprint. The result of test and general condition of liner suggest that the material is unsuitable since it is liable to distortion and it being impracticable to remove same except by grinding which would remove the hardened surface. HGS. | ||