Manufacturing tests of ODS ferritic steels by spray-dispersion method (I)

Fujiwara, Masayuki*; Nishida, Toshio*; not registered; Soshiroda, Tetsuo*

The Spray-Dispersion (SD) Method is a recently developed technique which can produce a steel containing dispersed oxide particles sprayed from outside into the molten steel stream. To evaluate the applicability of the oxide dispersion strengthened (ODS) ferritic steels made by this new process for the long life core materials of the large scale FBR's, a fundamental study using Fe-13Cr ferritic steels was conducted. The main results are summarized as follows : (1)From the results of the simulation tests utilizing water and molten Sn, it was cleared that the molten metal diameter, the throat diameter and the number of the spray gas nozzles, the spray gas nozzle angle, and the spray gas pressure are the important to get a favorable spray-dispersion condition. (2)An experimental apparatus for the SD method installed in a vacuum induction furnace was manufactured and the SD tests utilizing ZrO oxide particles were performed on the 10kg ingots of Fe-13Cr ferritic steels containing the dispersion-controlled elements such as Ti, Nb, V. The maximum quantity of ZrO added in the steels was about 0.5%. But the oxide particle sizes in the steels were large and the distribution of the oxide particles was not homogenious. It is considered that the higher pressure of the spray gas and the higher feed rate of the oxide powders are needed for the improvement of these problems.