Water-cooling casting method and device of hollow pipe blank

The invention relates to a water-cooling casting method and device of a hollow pipe blank. The water-cooling casting device comprises a barrel-shaped water-cooling outer metal mold and a barrel-shaped water-cooling inner metal mold, wherein the barrel-shaped water-cooling inner metal mold is arranged in the barrel-shaped water-cooling outer metal mold; a ring-shaped casting piece cavity is formed between the water-cooling inner metal mold and the water-cooling outer metal mold; riser casting molds are arranged at the tops of the water-cooling outer metal mold and the water-cooling inner metal mold; water-cooling bottom boxes are arranged at the lower parts of the water-cooling outer metal mold and the water-cooling inner metal mold; molten metal enters the cavity from a pouring gate through the water-cooling bottom boxes; the pouring gate is a tangential horizontal pouring gate, the molten metal enters the water-cooling bottom boxes along the tangential direction from the pouring gate, and by means of pushing of the outlet velocity of the tangential horizontal pouring gate, molten steel rises from the lower part of the cavity in a circumferential rotating manner; and the shapes of the longitudinal sections of the water-cooling outer metal mold and the water-cooling inner metal mold are tapered metal molds with thin upper parts and thick lower parts, the relative setting time of the molten metal at the upper part in the cavity is delayed than that of the molten metal at the lower part, and sequential cooling of the molten metal from bottom to top is realized by controlling and adjusting the height of cooling water, so that the quality of a finished product is improved.