The process is: various castings are heated to a temperature of 860-900℃ , the original matrix is ??completely austenitized by heat preservation , and then cooled in oil or molten salt to achieve quenching, and then heated at 250-350℃ for heat preservation and tempering, and the original matrix is ??converted The structure of tempered martensite and retained austenite, the original spherical graphite shape remains unchanged. The processed castings have high hardness and certain toughness, retain the lubricating properties of graphite, and improve wear resistance. As shaft parts, ductile iron parts, such as crankshafts and connecting rods of diesel engines, require comprehensive mechanical properties with high strength and good toughness. The iron castings are quenched and tempered .