Casting Temperature

While both binder ratio and level affect porosity formation, their effect is temperature-dependent. Results obtained from castings poured at several temperatures and incorporating unbalanced binder ratios (favoring excess Part II) are shown in Table 2.

Table 2. Effect of Pouring Temperature on Porosity Formation




Pouring temperatures of 2700F (1482C) and higher (as measured in the pouring ladle) produce severe subsurface defects when unbalanced ratios are used. This is not observed with balanced ratios or excess Part I. Reducing pouring temperature at both binder levels resulted in less porosity until, at the lowest temperature, sound castings were achieved.

Pouring temperature effects also were demonstrated by pouring step cores coated with the Part II component. For these tests, pouring temperatures were 2500F (1371C), and cores were bonded with an unbalanced (35:65 ratio) binder system containing 3% total resin. Sectioned castings were entirely sound.

The porosity-temperature dependency is illustrated in Fig. 2, in which pouring temperature is plotted against binder ratio. There is a region in which porosity forms and one where sound castings are obtained. In between these areas, porosity may or may not occur, depending on other liquid metal processing factors.



Fig. 2. Effect of pouring temperature and binder ratio on porosity formation.

Table of contents
[Paper Header]
[Porosity Study]
[Binder Ratio] [Binder Level] [Casting Temperature] [Section Size]
[Sand Effect] [Iron Oxide Additions] [ Binder Dispersion/Mixing]
[Metal Composition] [Core Age]
[Eliminating Porosity]
[Ti and Zr Additions] [In-the-Mold Additions] [ Core Washes]
[Core Post-Baking]
[Discussion]