PURPOSE: To manufacture the roll tire excellent in wear resistance by forming the matrix structure of a stock made of spheroidal graphite cast iron into a mixed structure of bainite, retained austenite, and spheroidal graphite by means of austempering treatment.

CONSTITUTION: A roll tire 11 supporting a cylindrical metal mold 12 of a device for centrifugally forming a Hume pipe 13 is manufactured by forming the matrix structure of a spheroidal graphite cast iron stock into a mixed structure of bainite, retained austenite, and spheroidal graphite by means of austempering treatment where the stock as it is, after rough working, or after finish working is heated and held at 800-900°C for 0.5-3hr, rapidly cooled down to 200-400°C, and held for ≥0.5hr. By this method, the roll tire 11 having particularly superior wear resistance can be obtained, and further, replacing time can be shortened and manufacturing costs in forming the Hume pipe can be remarkably reduced.