Hitachi Metals, Ltd.

Tamiya Kishida

Mitsuru Suzuki

Toshio Okuno

Noboru Hanai

Iwao Kashiwagi

Takashi Mukai

Kenji Tokuda

Atsusuke Nakao

Kokichi Mikutsu

Katsumi Kanamoto

Method for refining molten metal and apparatus for same

Isotropic tool steel consisting essentially of necessary elements as tool steel, less than 0.005 weight % of S and less than 30 ppm of O, the balance being substantially Fe. The necessary elements are, by weight, 0.10-0.70% of C, 2.00% or less of Si, 2.00% or less of Mn, 7.00% or less of Cr, 0.20-12.00% of W and/or Mo alone or in combination (1/2W+Mo), 3.00% or less of V. They may further include at least one of 4.00% or less of Ni, 6.50% or less of Co and 0.20% or less of N. The isotropic tool steel has cleanliness with respect to non-metallic inclusions defined by JIS G 0555 of dA60.times.400.ltoreq.0.010% and d(B+C)60.times.400.ltoreq.0.020%, and a ratio of transverse direction toughness to longitudinal direction toughness of more than 0.70. Since it is highly resistant to the generation and propagation of cracks and fracture, dies for hot working made therefrom can enjoy a long life.

Isotropic tool steel

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Yonago, Japan

Tamiya Kishida