Inclusion control in steel castings

“Non-metallic inclusions are mainly comprised of oxides, sulfides, and nitrides, and are formed in liquid steel during the melting and refining process, as a result of reoxidation, worn-out refractories, or entrained slag. The notch toughness of high strength steels is particularly susceptible to the type, number, size, and distribution of non-metallic inclusions. High manganese and aluminum austenitic steels, or Fe-Mn-Al steels, have gained much interest in the military and automotive sector because of their excellent combinations of high strength and toughness. However, these steels are subject to both oxide bifilms and aluminum nitride, AlN, inclusions which form during melting and casting. During the casting process, the gating system plays an important role in determining the casting quality and the overall level of inclusions and bifilm defects. Two solutions to control inclusions during mold filling include molten metal filtration and design of novel “naturally pressurized” gating systems that control metal flow into the casting cavity and reduce air entrainment. However, the use of filters and these naturally pressurized gating systems add an additional cost and generally reduce casting yield. In the current study, the effects of filtration and gating design on reduction of bifilms and inclusions in Fe-Mn-Al steel were determined using two novel mold designs. A parallel gating study involving an aluminum deoxidized, cast composition of SAE 8630 was also performed. The results of this study showed that ceramic foam filters were more effective at removing solid oxide bifilms and aluminum nitride inclusions from Fe-Mn-Al steel castings than the naturally pressurized gating systems. Future studies should be directed at developing naturally pressurized gating systems with filters”--Abstract, page iv

Filtration Efficiency of Inclusions in Lightweight FeMnAl Steels

This presentation was given at the Transaction of American Foundry Society Conference

β-Iminoenamine-BF2 Complexes: Aggregation-Induced Emission and Pronounced Effects of Aliphatic Rings on Radiationless Deactivation

The synthesis, photophysical, and electrochemical attributes of a novel class of boron difluorides containing an aromatic-fused alicyclic/hetero-alicyclic ring built on a β-iminoenamine chromophoric backbone are reported. The compounds displayed large Stokes shifts (86–121 nm), and were emissive in the solid state. The quantum yields obtained in solution at room temperature were unusually lower by an order of magnitude compared to those in the solid state. Some of the tested compounds displayed aggregation-induced emission (AIE). Single crystal XRD analyses revealed a lack of interplanar π–π interactions, which are presumed to be absent owing to non-planarity of the alicyclic component in the molecule. For most of the studied compounds, time-dependent DFT (TD-DFT) calculations invariably reveal intramolecular charge transfer (π–π*) characteristics with the frontier orbitals concentrated on the boron–nitrogen heterocycle. The participation of boron and fluorine atoms was found to be negligible

Metal-free triplet phosphors with high emission efficiency and high tunability

Design of highly efficient phosphorescent emitters based on metal- and heavy atom-free boron compounds has been demonstrated by taking advantage of the singlet fission process. The combination of a suitable molecular scaffold and appropriate electronic nature of the substituents has been utilized to tailor the phosphorescence emission properties in solution, neat solid, and in doped PMMA thin films