Titanium slab for hot rolling produced by electron-beam melting furnace, process for production thereof, and process for rolling titanium slab for hot rolling

A process for production of a titanium slab for hot rolling, comprising:

• using an electron beam melting furnace, in which a rectangular mold having a ratio (W/D) of the width (W) versus the thickness (D) of the rectangular mold is in the range from 2 to 10 is equipped, in a melting chamber maintained at a reduced pressure,
• pouring molten metal from the top of shorter side wall of the mold, wherein intensity of electron beam irradiated to the surface of the poured molten titanium pool in the rectangular mold is controlled in the manner which decreases the intensity from one of the shorter side walls of the mold to the opposite shorter side wall of the mold where the molten metal is poured,
• withdrawing out from the rectangular mold a titanium slab having a deformation of not more than 5 mm for the thickness direction versus the longitudinal direction, a deformation of not more than 2.5 mm for the width direction versus the longitudinal direction, both per a length of 1000 mm of the slab, and having a ratio (L/W) of the length (L) versus the width (W) is not less than 5, into an ingot chamber maintained at a reduced pressure,
• cutting off an interface of the melting chamber and the ingot chamber,
• filling the ingot chamber with argon gas to recover pressure inside the ingot chamber until a normal pressure,
• cooling the slab down to room temperature in the ingot chamber, and then moving the slab to the atmosphere.