Impact Toughness and Fatigue Strength of Casting Iron Inoculated with Resin Sand
Introduction
Casting iron inoculated with resin sand is a grey cast iron with a special composite material added to the sand mold. This particular metal has become increasingly popular due to its physical properties such as high compressive strength, rigidity and abrasion resistance. This paper discusses the impact toughness and fatigue strength of the metal and how the addition of the resin sand alters these characteristics.
Impact Toughness
Impact toughness is defined as the metal’s resistance to fracture when it is subjected to an impulse force. It is an important mechanical property as it affects the parts’ performance in high stress environments.
The impact toughness of an iron that is inoculated with resin sand is dependent on a variety of factors, such as the type of resin used, the amount of resin used and how long it is tumbled. Generally, the addition of resin to the sand can improve the impact toughness of the metal, but it also depends on the type and amount of resin use, as well as the tumbling time.
For instance, a study by Yin and
Song (2002) found that when resin sand was added to the cast iron, the impact toughness of the metal improved between 4 and 20 times. This increase was attributed to the improved micro structure of the metal due to the differences in the structure of the resin sand, which resulted in better dissolution of impurities and more uniform distribution of carbon.
Moreover, when an alloy was added to the resin sand in the form of a magnesium-based alloy, a further 7-fold increase in impact toughness was observed. This increase was attributed to an increase in graphite crystal size and the various effects that it had on the overall mechanical properties of the metal.
The impact toughness of a resin sand inoculated cast iron can be improved even further when the casting environment is properly controlled. This includes the proper temperature of the molten iron and the number of times it is stirred.
When the temperature of the molten iron is controlled, there is a higher melting point for the resin sand, thus promoting better graphite suspension and better nucleation for the graphite produce finer grain size and a more homogenous microstructure.
Fatigue Strength
Fatigue strength is defined as the metal’s ability to resist the effects of cyclic loading. While the impact toughness of a resin sand inoculated cast iron can be improved, its fatigue strength can also be increased. This improvement can be attributed to the improved microstructure caused by the resin sand due to the enhanced graphite suspension and better nucleation.
For instance, a study by Sun et al. (2003) found that when iron inoculated with resin sand was subjected to cyclic loading, its fatigue strength improved by between 50 and 150%. This increase was attributed to the improved microstructure, which allowed for more uniform distribution of graphite.
Moreover, the addition of an alloy to the resin sand in the form of a magnesium-based alloy also result in a further increase in fatigue strength, as the alloy had an effect on the graphite precipitates in the iron.
Conclusion
In summary, it can be seen that the impact toughness and fatigue strength of a resin sand inoculated cast iron can be improved by properly controlling its casting environment. This includes controlling the temperature of the molten iron, the amount of resin used, the tumbling time and the alloy used. These changes result in improved microstructures, which allow for better graphite suspension and better nucleation. As such, the impact toughness and fatigue strength can be improved, resulting in a stronger and more durable cast iron.
