抄録
Hereunder is presented the report of experimental studies that have been made in our laboratory extending for a considerably long period of time, of the creep-rupture strength of boiler tube materials, i. e. of steels of 11 grades of carbon steel, molybdenum steel and Cr-Mo steels including even 9% Cr-1% Mo. The test samples were taken from at least 3 heats of each grade up to as many as 21 heats of 2.25% Cr-1% Mo steel.
The main results obtained from these experiments are as follows.
(1) Very small effect of conbon on carbon steel has been observed in the long time test at above 400°C for creep-rupture strength.
(2) Similarly there has been but little difference in the creep-rupture strength of steels of 2 different 0.5% Mo grades with slightly different amount of carbon ingredient, in their long time test at above 450°C. These steels of variant molybenum grades occasionally showed very low values of rupture elongation, and had to be improved by addition of 0.5% Cr.
(3) The steels of 2.25% Cr-1% Mo and of 5% Cr-0.5% Mo showed low values of rupture strength at comparatively low temperature in 105hr when fully annealed
