A crystallizer for continuous casting comprising a tubular body (11) defining a longitudinal axis and having at least one wall (12) that defines a longitudinal through casting cavity (13), a plurality of longitudinal grooves (14) obtained at least on a portion of an outer surface of said at least one wall (12) and open towards the outside thereof, said plurality of longitudinal grooves (14) defining a corresponding plurality of longitudinal fins (16) on the tubular body (11), one or more layers of fiber composite material arranged in direct contact with the outer surface of said at least one wall (12) so as to close said longitudinal grooves (14) making corresponding longitudinal cooling channels (17) for the flowing of a cooling liquid, wherein said longitudinal grooves (14) cover at least 70% of said outer surface, and wherein the width of the longitudinal grooves (14) is greater than the width of the longitudinal fins.

In production of a reactive metal using a melting furnace for producing metal having a hearth, ingots can be efficiently produced by efficiently cooling the ingots extracted from the mold provided in the melting furnace. In addition, an apparatus structure in which multiple ingots can be produced with high efficiency and high quality from one hearth, is provided. A melting furnace for producing metal is provided, the furnace has a hearth for having molten metal formed by melting raw material, a mold in which the molten metal is poured, an extracting jig which is provided below the mold for extracting ingot cooled and solidified downwardly, a cooling member for cooling the ingot extracted downwardly of the mold, and an outer case for keeping the hearth, the mold, the extracting jig, and the cooling member separated from the air, wherein at least one mold and extracting jig are provided in the outer case, and the cooling member is provided between the outer case and the ingot, or between the multiple ingots.