25Cr-20Ni耐熱鋼の相変化について
1970 年 34 巻 7 号 p. 706-711
詳細
1970 年 34 巻 7 号 p. 706-711
High purity 25Cr-20Ni steels were melted in vacuum and air respectively, and the phase change due to annealing at 750°, 800°, and 850°C for 2∼1500 hr after casting or forging was studied by means of micro-Vicker’s hardness testing, magnetic analysis, X-ray diffraction and microstructure examination.
The results obtained are as follows:
(1) The δ-ferrite which remains in the as-cast and as-forged specimens is sigmanized in less than 100 hrs annealing at 750°∼850°C.
(2) In the high purity 25Cr-20Ni steels, annealed at 750°∼850°C for a long time, the higher the temperature, the more rapid the ferrite precipitation, and the ferrite precipitation is more rapid in the forged materials than in the cast ones.
(3) The precipitated ferrite is sigmanized gradually with the annealing time and most rapidly in the temperature range between 800° and 850°C.
(4) The ferrite precipitated in annealing disappeares more slowly than that of δ-ferrite which remains in the as-cast and as-forged specimens.
