Manufacturing and Mechanical Property Test of the Large-Scale Oxide Dispersion Strengthened Martensitic Mother Tube by Hot Isostatic Pressing and Hot Extrusion Process

Narita, Takeshi; Ukai, Shigeharu  ; Kaito, Takeji ; Otsuka, Satoshi   ; Fujiwara, Masayuki

Mass production capability of Oxide Dispersion Strengthened (ODS) ferritic claddings are evaluated in the PhaseII of Feasibility Studies on Commercialized Fast Reactor Cycle System. The cost for manufacturing mother tube has a dominant factor in the total cost for manufacturing ODS ferritic cladding. In this study, the large scale 9Cr-ODS martensitic mother tube were produced by overseas supplier with mass production equipments for commercialized ODS steels. The process of manufacturing the ODS mother tube consists of production of raw material powder, mechanical alloying by high energy ball mill, hot isostatic pressing (HIP), and hot extrusion. Following results were obtained in this study. (1) Micro structure of the ODS steels is equivalent to that of domestic products, and fine oxides are uniformly distributed. The mechanical alloying by large capacity (1 ton) ball mill can be satisfactorily carried out. (2) A large scale mother tube (65OD48ID10,000L), which can produce about 60pieces of 3m length ODS ferritic claddings by four times cold rolling, have been successfully manufactured through HIP and Hot Extrusion process.(3) Rough surface of the mother tubes produced in this study can be improved by selecting the reasonable hot extrusion condition. (4) Hardness and tensile strength of the manufactured ODS steels are lower than domestic products with same chemical composition. This is owing to the high aluminum content in the product, and those properties could be improved by decreasing the aluminum content in the raw material powder.