Population Size Distribution of Rare Earth and Non-metallic Inclusions in 4130 and 8630 Steels
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The purpose of this work was to find the population size distribution of rare earth and non-metallic inclusions in polished samples and filter paper samples of 4130 and 8630 steels. The steels had additions of either rare earth silicide or EGR grain refiner. Interest in rare earth-containing inclusions has increased due to their ability to refine the solidification structure of steel. However, the exact mechanism is not fully understood. To accurately determine size and composition, electrolytic dissolution with 2% TEA was employed to dissolve the steel matrix away. A scanning electron microscope examined the isolated inclusions on filter paper specimens. For comparison, other samples were analyzed in a more typical polished metallographic specimen. All heats had very similar inclusion sizes. Most inclusions were between 5 and 9 μm. There was a variation in inclusion composition between the 4130 and 8630 heats. The cause of this variability appeared to be due to random changes in the amount of reoxidation that occurred during tapping.
Keywordselectrolytic extraction electron microscopy rare earth inclusions aluminum oxide-type inclusions
The authors would like to thank the support of the Office of Naval Research who financially supported this work through Award Number N141410740. Foseco’s support through donations of ladle liners is also acknowledged. Cody Megregian and Taylor Hunter are recognized for their assistance in pouring the plate castings. Jennie Tuttle’s persistence in editing the paper is also tremendously appreciated.
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