Rare earth cast iron additives

： Rare Earth Cast Iron Additives

Rare earth cast iron additives have been used in a variety of methods over the last 50 years or so. The development of rare earth cast iron additives began in Europe in the 1970s when European countries sought to produce higher quality gray and ductile cast iron products. Since then there have been a number of different forms of rare earth cast iron additives developed.

These rare earth additives are used to improve the machinability of cast iron. Generally, these additives are added in small amounts to a melt either before or after its initial melting. The rare earth elements (REEs) act as a nucleating agent during solidification to increase the rates of cooling and stabilize the generated phases. This stabilizes the as-cast structure as it cools, allowing for higher quality castings.

The rare earths act as powerful nucleating agents because they are soft enough to not disturb the crystallization process while they are small enough to fill the gaps between the iron crystals. As a result, the rare earths are able to promote the formation of finer iron grain sizes in the cast iron. This decreases the necessary machining time needed to get the desired shape and size of the final product.

The rare earth elements that are used as strong nucleating agents are the lanthanides, a series of elements that can be found on the periodic table at the bottom of the fourth and fifth periods. The lanthanides series of elements have very similar chemical and physical children of other elements, called the “rare earth metals”.

In addition to their nucleating properties, rare earths have the ability to increase strength and wear resistance in the cast iron which is considered to be a hindrance in cast iron because of its higher carbon content and greater grain size. The REEs act as grain refiners and decrease the size of the grains in the cast iron, which decreases the amount of shrinkage. This helps to reduce porosity and other such defects in the cast iron as well as improving its strength and its ability to resist wear.

Although rare earths are beneficial to the production of cast iron articles, there are also some drawbacks to the use of them. It is important to remember that they are unstable in their oxygen form and can therefore evolve into an aerosol form when heated. This can be an irritant both to workers and the surrounding environment.

In addition, the cost of rare earths continues to rise and thus their cost effectiveness decreases. Many foundries are now turning to more cost-friendly options for rare earth additions such as using oxides or carbides.

Overall, rare earth cast iron additives continue to play an important role in the production of iron and steel parts. The rare earths act as powerful nucleating agents to help improve the machinability of the cast iron and promote a finer grain size for a better finished product. Despite their high cost, the benefits of their use make them a worthwhile addition to any casting operation.