RESEARCH BY COMPUTER SIMULATION ON THE INFLUENCE OF PAINTED MOLDS ON THE THERMAL REGIME OF IRON CASTINGS SOLIDIFICATION (part II)

摘要

Experimentally it was found that application on the active surface of molds of a coat of paint based on metallic compounds, causes the occurrence of a degenerated graphite layer at the surface of nodular or compacted graphite iron castings. Have been carried out by computer simulation, research on the influence of coat of paint on the cooling and solidification of iron castings. Have been studied four types of paints: Al_2O_3, Fe_2O_3, FeS_2 and MgO respectively. The coat of paint applied on the surface of molds had a 1 mm thickness. The results were compared with those obtained in the case of pouring into the molds without paint. It was revealed that in a thin layer at the interface (1mm thick) occurs a pronounced (up to approximately 1100 ° C) and very fast (in about 0.2 or 0.3 seconds) cooling. The fast cooling can be explained by the higher thermal conductivity of coat of paint compared with the moulding sand. The cooling is followed in the next 15 seconds, by a reheating up to temperatures of 1205-1215°C. This superficial layer cooling at the metal-paint interface',"explains the occurrence of degenerated graphite layer. This section of the paper presents the results obtained on the influence of the paint layer applied to the casting mould on the kinetics of liquid metal solidification at the metal-mould interface.