蒸気タービン軸車材のオーステナイト粒度とクリープ破断強度の関係について
蒸気タービン軸用Cr-Mo-V鋼の高温強度に関する研究-II
1963 年 49 巻 13 号 p. 1892-1899
詳細
1963 年 49 巻 13 号 p. 1892-1899
To make clear the cause for the dispersion of the creep rupture strength of large sized steam turbine forgings made of a Cr-Mo-V steel, the relations between austenitic grain size and creep rupture strength of the rotors were investigated. The creep rupture and tensile specimens were cut from the body ends of the rotors. Creep rupture tests were carried out at 510°C, 538°C, 565°C and 593°C, excepting those of rotor H which were carried out at 565°C. The austenitic grain was revealed by J. B. Cohens' etchant. On the other hand, to make sure of the test results on actual rotor forgings, the creep rupture strengths of specimens austenitized at various temperatures were investigated. The results were as follows.
1. It was found that a relatively large difference of the actual a astenitic grain size existed between those of rotors, and the creep rupture strength of the rotors increased with an increasing mean actual austenitic grain diameter.
2. And it was ascertained by the test results on the tendency to grain growth of the rotors that the rate of grain growth is comparatively fast at about 960°C which is the austenitizing temperature of actual rotor forgings.
3. Creep rupture test results of specimens austenitized at laboratory also indicated that the creep rupture strength of the specimens was markedly affected by only the differences of austenitic grain size.
4. According to the results mentioned above, it may be concluded that the dispersion of the creep rupture strength of steam turbine rotor forgings largely stems from the differences of actual austenitic grain size which are due to the change of the austenitizing temperature of the rotors.
