Semi-solid processing is believed to be effective at improving the quality of various properties of the materials that are processed, i. e., reduction of segregation, surface crack, porosity, etc. To realize these improvements, it will be necessary to produce semi-solid metal slurry with a high fraction solid and fine primary particles. A basic study was carried out in order to produce semi-solid metal having high fraction solid at high cooling rate. The study used shearing and cooling roll method to examine the controllability of the discharge velocity of semi-solid metal, the fraction solid, the solidified structure, and the quality of the semi-solid metal slurry. The results of the study have clarified the following points.
1) The discharge velocity of semi-solid metal slurry can be controlled by changing the clearance of the discharge port and the number of revolutions of the roll, thereby making it possible to produce slurry with a desired fraction solid.
2) Slurry with a high fraction solid (greater than 0.3) and very fine primary particles can be produced.
3) The conditions necessary for producing fluid slurry with a high fraction solid have been clarified.
