I understand that rapid cooling increases undercooling and results in fine grains. However, due to the nature of the casting process (investment casting of thin objects), a very slow cooling rate is a necessity. Given this, are grain refining inoculants and such effective solutions still?
Hello Vaanchit,
As you said it is difficult to have control over grain refinement in the slow cooling rate process. So inoculation process can be employed for that purpose. Generally in steels, Si, Carbon, and oxygen are used in minor quantities so that it forms SiO2 as base nuclei on which graphite starts to grow.
In the case of low alloyed or unalloyed steels, 1.5 to 3 % Si and 3 to 4 % C are used. During cooling, the eutectic composition is achieved and the precipitating carbon is then fully present as graphite.
Elements with higher carbide tendency (V, Ti, Ta, Si) than iron are generally used so that it prevents the formation of Fe3C.
Besides that, inoculation-effective elements should have a high affinity to oxygen, such as calcium, aluminum, barium, zircon, strontium, and some rare earth metals. This is because successful inoculation is always associated with a depletion of the oxygen dissolved in the melt. However, some inoculants also contain elements such as bismuth, titanium, manganese, sulfur, and oxygen, for example, which can also have a positive effect on graphite nucleation.
Hope this helps you.
Thank you.
Hi,
The answer to your question is yes. You can apply a microstructure inoculant.
As Koushik written, in general, all carbide-forming elements are used to the grain refinement of cast steel. They are commonly used for heavy steel castings, which are cools down very slowly. What grade of cast steel do you want to modify?
Sebastian Sobula I am specifically looking at austenitic stainless steels.
Ferrotitanium is commonly used in grain refinement of this type of steel.
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