Abstract: A method of refining metal to be processed to a high degree of purity by heat-melting the metal in a melting furnace in the form of a metal crucible placed in a vacuum vessel. The method includes evacuating prior to melting, preheating the inside of the entire vacuum atmosphere including the inner wall surface of the vacuum vessel, component parts inside the vessel and the like in order to keep the total pressure within the vessel at 1.times.10.sup.-8 Torr or lower, and effecting high frequency induction heating while controlling the partial pressure of each of O.sub.2, H.sub.2, CO in the atmosphere inside the vessel. Further, the vacuum vessel, the metal crucible and an induction heating coil attached to the crucible, each of which has double jacket structure, are heated or cooled by supplying circulating heating or cooling water in a water-passage space of each of the vacuum vessel, the metal crucible and the induction heating coil, so that the inside of the melting furnace is baked.

Abstract: A method of refining metal to be processed to a high degree of purity by heat-melting the metal in a melting furnace in the form of a metal crucible placed in a vacuum vessel. The method includes evacuating prior to melting, preheating the inside of the entire vacuum atmosphere including the inner wall surface of the vacuum vessel, component parts inside the vessel and the like in order to keep the total pressure within the vessel at 1.times.10.sup.-8 Torr or lower, and effecting high frequency induction heating while controlling the partial pressure of each of O.sub.2, H.sub.2, CO in the atmosphere inside the vessel. Further, the vacuum vessel, the metal crucible and an induction heating coil attached to the crucible, each of which has double jacket structure, are heated or cooled by supplying circulating heating or cooling water in a water-passage space of each of the vacuum vessel, the metal crucible and the induction heating coil, so that the inside of the melting furnace is baked.

Abstract: A cold crucible induction melting furnace is provided with a plurality of segments separated by a plurality of slits that surround a bottom member which together form the melting chamber. Each lower end of each segment is overlapped with and spaced from a short part of a vertically extending side wall of the bottom member so as to form a horizontal gap there between. A radially and outwardly extending flange protrudes from the bottom member side wall below each segment lower end to form a lower gap there between. An induction coil is disposed around and spaced from an outer face of the segments with a lower end adjacent to each of the lower segment ends and an upper end adjacent to an upper part of each segment that is in turn connected with an adjacent upper segment part to form a short circuited part.

Abstract: A high temperature microscope having an optical system and a chamber system is disclosed. Frictional rotation of the peep window provided in the chamber system is caused together with frictional rotation of a first flange, in which the peep window is provided, and a second flange, which surrounds the first flange and is surrounded by a stationary third flange. It is thus possible to greatly delay the limit of the period, during which observation of the object can be made, due to fogging of the peep window. Double wall sealing ring members are provided between the first and second flanges and between the second and third flanges of the chamber of the high temperature microscope. The space between the double wall sealings can be evacuated through an inverted T-shaped ventilation hole provided in the second flange. Thus, the chamber can be evacuated to a superhigh vacuum higher than the vacuum degree obtainable in the chamber of the prior art high temperature microscope.