ASPECTS OF CAST IRON GRADE SELECTION FOR COUNTER-PRESSURE DIECASTING DIES.

The dies used in the counterpressure diecasting process encounter additional molten metal pressure during die cavity filling and holding under excess gas pressure. Under actual production conditions, the overall die temperature is steady at about 200-220 degree C. The temperature differences of 280-300 K within the die produces cracking. The practical resistance of cast irons to temperature cycling has been evaluated by thermal resistance tests on various grades. The highest thermal durability was reached by a ferritic nodular cast iron. Molten gray iron can be simultaneously modified and alloyed with Cr by ladle treatment with ferrosilicochromium grade FSKh30 or FSKh18. This provides three times the thermal durability of the original gray iron.