Method for measuring ductile-brittle area proportion of nodular cast iron impact fracture

The invention relates to a method for measuring the ductile-brittle area proportion of a nodular cast iron impact fracture. The method comprises steps that a nodular cast iron impact sample obtained after impact breaking is placed in an ultrasonic cleaning instrument to be cleaned, dried through blowing of an air duct, bonded to a sample table and placed in a scanning electron microscope sample bin, and a fracture image is called out; an impact test sample fracture is provided, an electron microscope fracture morphology picture is shot by moving for a fixed distance each time, five pictures are shot in total, the grids are added to the pictures, and all grid intersection points falling in the pictures, all points falling on the graphite nodules in the pictures and all points falling on a brittle fracture in the pictures are counted, calculating is carried out, and an average value of the percentage of the brittle fracture for five times is calculated according to a formula, namely thearea percentage of the br