Study on Molding Conditions and Metallographic Microstructure of Super Thin Section Ductile Iron Casting

摘要

The purpose of this study is to investigate the effect of pressurized (the maximum instantaneous pressure is 0.2kg/cm~2) on the green sand mold when pouring for molding conditions (fillability degree, surface defects) and metallographic microstructure of the different thickness specimens (1.0mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm, 2.0mm, 2.5mm, 2.8mm). The result of experiment show that when in the condition of pressurized for super thin section ductile iron specimens have significantly improved in fillability. For example about the thin specimens 1.0mm, the degree of fillability improvement is from 32.29% to 84.09%, rised 51.80%. And the degree of improvement about 1.2mm specimens is from 65.09% to 99.36%, rised 34.27%. When in the conditions of pressurized and unpressurized system for super thin section ductile iron specimens. (1) Have no significant difference in metallographic microstructure for specimens thickness from 1.0mm to 2.8mm. (2) The distribution ratio for graphite, pearlite, cementite and ferrite have no obviously difference. (3) When the casting specimens with increasing thickness, along with reducing about transformed ledeburite and pearlite (white cast iron). (4) The mass effects for the different thickness specimens are also not evident.(5) In as-cast condition with no white cast iron microstructure, the super thin section ductile iron specimens can completely filling thickness is in 2.5mm.