Abstract: A method of refining molten metal includes the steps of reduced-pressure-refining molten metal in a heated vessel, adding slag-forming agents into the refined molten metal while keeping the molten metal in the vessel, or after pouring the molten metal into another vessel, re-refining the molten metal by heating the molten metal with inert-gas plasma and while stirring the molten metal as occasion demands. Preferably, the refining apparatus includes two adjacent chambers, each chamber isolated from the surrounding atmosphere. The chambers can be connected with, or separated from, each other and each chamber is provided with an exhaust device. One of the chambers is provided with an induction heating refining furnace, and the other chamber is provided with inert gas plasma heater. The apparatus also includes a re-refining vessel which is transferable between the two chambers, and a material feeder for feeding slag-forming agents into the re-refining vessel.

Abstract: 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.