The Mechanism of Iron and Graphite Castings
Iron and graphite castings are some of the most common components used in engineering and construction. However, they have different mechanisms and chemistry of processing and use. Understanding the differences between these two materials is vital for selecting the most suitable casting material and achieving the best castings.
Iron castings are produced using a process called smelting. The metal is heated in a furnace which removes the undesirable elements and impurities, leaving a molten metal which can be cooled and formed into a desired shape. Compressed metal molds are usually used during molding, and the pattern is created by pouring a liquid metal into the mold and cooling it in order to harden it.
Graphite castings, on the other hand, are made through a process of carbonizing or graphitization. This method involves reacting a metal such as iron or steel with a carbon source such as coke or coal in a furnace at high temperatures. This creates a slag which consists of the carbonized metal and the other particles and impurities. The slag is then heated in a separate furnace to remove the other components leaving only pure graphite.
When comparing iron and graphite castings, there are several important differences in both the materials and their processes. Iron castings are usually more rigid and robust than graphite castings, while graphite castings have the advantages of being more ductile and resistant to thermal expansion. Graphite castings have a much lower melting temperature and are, thus, more resistant to thermal shock. However, they are not as strong or durable as iron castings and have a tendency to wear out quicker.
In terms of chemistry, iron castings are composed of a combination of iron and carbon, while graphite castings usually consist mostly of carbon. Iron castings are heated to a higher temperature than graphite castings, which means that impurities within the metal are burned out. As a result, iron castings are relatively “clean” and free from impurities. Graphite is impervious to oxidation and can, thus, be heated to lower temperatures, although these temperatures may still be above the melting point of the impurities.
From a manufacturing standpoint, iron castings are typically less expensive than graphite castings because they are relatively easier to produce. Graphite castings, on the other hand, require additional expense to produce due to the higher consumption of carbon and energy needed to achieve the required temperatures.
In summary, iron and graphite castings are two distinct materials with different characteristics and underlying mechanics. Knowing the differences between them is key to ensuring the right material is chosen for the right application. Iron castings are generally stronger and more rigid while graphite castings are more ductile and resistant to thermal shock. Understanding their chemistry is also important when considering the temperatures and processes involved in each casting process. Ultimately, which casting material is chosen will depend on the application and whether the advantages outweigh the disadvantages of any particular material.
