Abstract: In the paper, a new method and a device for fast evaluating the graphite shape in liquid cast iron are advanced. The new method is named amplitude and frequency equivalent of bubbles and its foundation is to take the pressure in the bubble and the frequency of blowing bubbles as the characteristics to obtain the equivalent by which the graphite shape in liquid cast iron can be known before casting. The testing process will take only 10 seconds. The new device based on the new method consists of a heat resistant and replaceable detector and a microcomputer acquisition system. The new method and the device have advantages of convenient operation, high resolution ratio and high anti-jamming ability.

Key words: cast iron, graphite shape, test