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).
Comparative study on valve stretching for four different steel materials under specified load and temperature conditions.
| Identifier | ExFiles\Box 66a\2\ scan0086 | |
| Date | 4th June 1928 | |
| F.BY. Hs.{Lord Ernest Hives - Chair} Fk. X8060 H11/EA4.6.28. Laboratory. Re Valve Stretching. Below are given comparative figures on valves made from four different materials. The figures indicate the stretch under the conditions specified. The temperature given was only attained for about 1 1/2" of the valve length close to the head, i.e. comparable with running exhaust valves. Load 1cwt. 6 hrs. 700°C. | Load 1cwt. 6hrs. 850°C. | Load 1cwt. for further 9hrs 850°. | Approx. coeff. of expansion K.E. DTD49: No Change. | No Change. | No Change. | 0.000019 Silchrome: No Change. | 0.004" * | Still 0.004" | 0.0000125 Firth's Crown: 0.001" | 0.008" | 0.011" | 0.000018 Quickstep: 0.0005" | 0.021" | 0.037" | 0.000012 * From the above it appears that Silchrome steel has elongated at 850°C, but does not continue creeping. In consideration of this, a valve was heated without load at 850° for 6 hours, when an elongation of 0.002" was noted. The same valve was then loaded at 850 C and only extended 0.002" after 12 hours, thus showing that the real creep due to load was only 0.002". This is very much less than Quickstep or Firth's Crown (austenitic) steel. HC Further tests on bars are on progress. | ||