Method for producing metal ingot

A method for producing a metal ingot by using an electron-beam melting furnace having an electron gun capable of controlling a radiation position of an electron beam, and a hearth that accumulates a molten metal of a metal raw material, the metal ingot containing 50% by mass or more in total of at least one metallic element selected from titanium, tantalum, niobium, vanadium, molybdenum and zirconium, said method comprising:

• radiating a first electron beam onto a surface of the molten metal along an irradiation line, wherein:
• among a plurality of side walls of the hearth that accumulate the molten metal of the metal raw material, a first side wall is a side wall provided with a lip portion for causing the molten metal in the hearth to flow out into a mold;
• the irradiation line is disposed in a downstream region between an upstream region in which the metal raw material is supplied onto the surface of the molten metal and the first side wall, such that the irradiation line blocks the lip portion, and two end portions of the irradiation line are positioned at an inside face of any of the plurality of side walls of the hearth, or in a region in which a separation distance from an inside face of any of the plurality of side walls of the hearth is 5 mm or less;
• the irradiation line has a convex shape that projects from the lip portion side toward the upstream, and is in a V-shape, or a circular arc shape having a diameter that is equal to or larger than an opening width of the lip portion;
• a radiation position of the first electron beam runs between the two end portions of the irradiation line, such that the irradiation line on the surface of the molten metal is repeatedly scanned with said first electron beam emitted from the electron gun;
• and
• the radiation of the first electron beam along the irradiation line increases a surface temperature (T2) of the molten metal at the irradiation line above an average surface temperature (T0) of the entire surface of the molten metal in the hearth, and forms, in an outer layer of the molten metal, a molten metal flow toward upstream that is a direction toward an opposite side to the first side wall from the irradiation line, wherein radiation conditions are set such that the molten metal flow can be formed and constantly maintained.