Effect of thermophysical property and coating thickness on microstructure and characteristics of a casting

Abstract

A new improved investment casting technology (IC) has been presented and compared with the existing IC technology such as lost foam casting (LFC). The effect of thermophysical property and coating thickness on casting solidification temperature field, microstructure and hardness has been investigated. The results show that the solidification rate decreases inversely with the coating thickness when the coating contains silica sol, zircon powder, mullite powder and defoaming agent. In contrast, the solid cooling rate increases as the coating thickness increases. However, the solidification rate and solid cooling rate of the casting produced by the existing IC and the improved IC are very similar when the coating thickness is 5 mm, so the microstructure and hardness of a container corner fitting produced by the improved IC and the existing IC are similar. The linear regression equation for the grain size (d) and cooling rate (v) of the castings is d= –0.41v+206.1. The linear regression equation for the content of pearlite (w) and solid cooling rate (t) is w=1.79t + 6.71. The new improved IC can greatly simplify the process and decrease the cost of production compared with the existing IC. Contrasting with LFC, container corner fittings produced by the new improved IC have fewer defects and better properties. It was also found that the desired microstructure and properties can be obtained by changing the thermophysical property and thickness of the coating.

Keywords

• improved investment casting; thermophysical property; coating thickness; microstructure; property