Abstract:Herein, a method of supergravity-enhanced separation was used to remove oxide and nitride inclusions from Inconel 718 superalloy melt, with elucidating the inclusion removal behavior by varying the gravity coefficients (G) and separation times (t) used for melt treatment. Under supergravity conditions, inclusions concentrated at the sample top and are almost absent at the sample bottom. Moreover, the inclusion number density and average size showed a gradient distribution along the supergravity direction, and … Show more
“…The supergravity field can achieve the separation of suspended dross and liquid as an efficient method used to separate components of complex materials based on the differences in the relative movements of the heterogeneous phases in the supergravity field. 16,17 The supergravity separation technology has also been successfully applied to purify metals such as steel, Al, and Sn. [18][19][20] Some researchers studied the influence of the supergravity field on zinc slag and inclusions in different materials and showed that the supergravity field could realise the separation between different phases.…”
In this research, supergravity enrichment experiment was conducted to determine compounds in suspended dross and to analyse density of the suspended dross in the hot-dip Al–Zn (ZA) melt. It was found that the suspended dross was composed of Al–Fe–Si–Zn intermetallic compounds (IMCs), mixtures of Fe2Al5Zn0.4 and Alx–Fe3–Siy with various Al and Si contents. The density of suspended dross was small compared with the molten hot-dip ZA liquid. After being quenched in water, the morphology of the suspended dross was confirmed as polygonal granular structures. Thermodynamics was applied to explain why there were various morphological structures of the suspended dross in the solidified hot-dip ZA melt. This research had also demonstrated that it was technically feasible to separate the suspended dross from the molten hot-dip ZA melt in a supergravity field.
“…The supergravity field can achieve the separation of suspended dross and liquid as an efficient method used to separate components of complex materials based on the differences in the relative movements of the heterogeneous phases in the supergravity field. 16,17 The supergravity separation technology has also been successfully applied to purify metals such as steel, Al, and Sn. [18][19][20] Some researchers studied the influence of the supergravity field on zinc slag and inclusions in different materials and showed that the supergravity field could realise the separation between different phases.…”
In this research, supergravity enrichment experiment was conducted to determine compounds in suspended dross and to analyse density of the suspended dross in the hot-dip Al–Zn (ZA) melt. It was found that the suspended dross was composed of Al–Fe–Si–Zn intermetallic compounds (IMCs), mixtures of Fe2Al5Zn0.4 and Alx–Fe3–Siy with various Al and Si contents. The density of suspended dross was small compared with the molten hot-dip ZA liquid. After being quenched in water, the morphology of the suspended dross was confirmed as polygonal granular structures. Thermodynamics was applied to explain why there were various morphological structures of the suspended dross in the solidified hot-dip ZA melt. This research had also demonstrated that it was technically feasible to separate the suspended dross from the molten hot-dip ZA melt in a supergravity field.
“…For example, based on the different density of metal melt and inclusion, Meng et al 18) achieved the purification of scrap Al-Mg alloys by supergravity, leading to a concentration of nonmetallic inclusions and Fe-rich impurities at the bottom of the alloy and an increase in enrichment proportional to the gravity coefficient. Shi et al 19) employed supergravity to separate Al 2 O 3 and TiN inclusions from 718 superalloy, which induced the migration of most inclusions to the top of the sample and a decrease in total O and N contents from 34.4 ppm to 8.7 ppm and 133.4 ppm to 34.1 ppm, respectively. Given the successful applications of supergravity in metal purification, it is considered feasible to use supergravity to remove oxide impurities from waste NdFeB magnets.…”
NdFeB magnets are the most widely used rare earth permanent magnet materials at present. The increasing number of the waste NdFeB magnets and their high rare earth content motivate a search for technologies to allow their cost-effective and environmental-friendly recycling. In this study, removal of oxide inclusions from waste NdFeB magnets by supergravity technology was investigated and the separating conditions were optimized for maximum oxide removal. Under the optimized conditions of G = 800 and t = 15min, the total oxygen of the sample decreased from 410 ppm to 28 ppm, with the oxide removal efficiency of 96.8%. The theoretical time to remove inclusions with different sizes was calculated by Stokes' law, and the experimental phenomena were in good agreement with the calculated ones. The supergravity technology has been demonstrated highly efficient in removing oxide from waste NdFeB magnets for the recycling. A design for an industrial reactor was presented to pave the way for future commercial processing and utilization of waste NdFeB magnets.
“…34,35) However, the control of strict pouring temperature is difficult. Shi et al 36) have investigated the effect of supergravity-induced separation on the removal of oxide and nitride inclusions from IN718 alloy melt. The removal behavior of inclusions is dependent on the gravity coefficients (G) and separation times (t).…”
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