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).
Letter to Toledo Woodhead Springs Ltd. concerning the elimination of decarburisation in spring manufacturing using a cyanide bath.
| Identifier | ExFiles\Box 154\2\ scan0111 | |
| Date | 14th July 1938 | |
| -2- 14th. July, 1938. Messrs. Toledo Woodhead Springs Ltd., Sheffield, 1. For some years now I have been advocating both in connection with leaf and helical type springs, the elimination of decarburisation by means of a cyanide bath. For this operation to be successful, it demands that (a). Decarburisation should be of small depth. (b). Regularity in regard to the depth of decarburising over the length of the plates. for which purpose I had suggested to different makers, rolling the plate in short lengths and the maintenance of steady temperatures in the furnaces, the temperature, of course, being kept as low as possible consistent with the necessities of the rolling operation. During the last year or so, the N.P.L. have taken up this scheme and demonstrated that by use of a cyanide bath, accurately controlled, decarburised plates can be restored, and more than that, a slight gain in tensile strength is produced in the outer fibres, which masks the effect of small discontinuities and faults which normally occur in rolling. This effect is so marked that results were better than material which had been ground to remove decarburisation completely, and then shot blasted after heat treatment. If you wish to make a real success of spring making, these factors should be taken into consideration and the necessary experimental work put through to determine the length of time the plates should lie in the cyanide bath, also the best temperature for same, bearing in mind, of course, the fact that there is the accurate temperature for quenching, but slight departures to be made from this in the direction of going higher with the object of giving better control of the cyanide bath and its effects upon the steel. One other factor which we had proved beyond all question, is the serious issue of corrosion attack. A small area pitted by rust will reduce the tensile strength of the steel from its heat treated value round about 90 tons to the figure characteristic of the normalised condition. | ||