OPTIMISATION OF THE GRAY CAST IRON SAFETY CASTING CASTED WITH AUTOMATIC FURNACES AND IMPORTANCE OF THE PRECONDITIONING OF THE MELTED IRON

摘要

The passage from the classic pouring with ladle to automatic sistems means is certainly a progress mostly in term of productivity, hut at the same time it has raised some metallurgical problems. The report details the experience carried out in a foundry with coreless electrical melting furnaces. This foundry had to face metallurgical and mechanical working problems after the passage to an automatic pouring system. The main problems faced in the foundry were: 1. Eccessive slags in the casting furnace 2. Very changeable metallographic conditions 3. Fall down of the working degree of the casting 4. Increase of the scrapes for pinholes and blowholes The above listed problems have been faced by an effective preconditioning of the melted iron. The report details the difference between the bath conditioning and the pre-inoculation, explaining the mechanisms. The results obtained by the foundry have been detailed in the following report and they can be summarized in: 1. elimination of the problems due to slags 2. eliminartion of the inoculation in the ladle or in a stream, consequence of the long time of the nucleation status due to the preconditioning. 3. quality stabilization and reproducibility considerable increase of castings in the mechanical working The report gives a new way to understand the mechanisms of the slags formation and of the nucleus in the careless electrical furnace. This is of a pratical interest for all the foundries having similar characteristics to the foundry where the research has been carried out.