Yongsheng WANG
,
Chenxi JI
,
Jiongming ZHANG
,
Xinhua WANG
,
Wanjun WANG
金属学报(英文版)
doi:10.1016/S1006-7191(08)60108-8
Mathematical model of solute [C] distribution in twin-roll strip casting process has been setup successfully with Calcosoft for the first time. Simulation result shows that in the center of the molten steel pool between the two rolls there is a vortex flow, which is a solute enriched area. But the highest solute concentration position is at the solidification front of the columnar grain zone near the cooling roll surface. Another solute enriched position is in the back flow above the nip point. Combined with the formation mechanism of microstructure in final as cast strip, analysis shows that solute enriched area is in the transitional area between columnar and equiaxed grain zone.
关键词:
Twin-roll strip casting
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Xiaoxuan DENG
,
Min JIANG
,
Xinhua WANG
金属学报(英文版)
Inclusion characteristic and microstructure of rare earth (RE) elements containing steel were evaluated with scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), element-mapping, optical microscopy (OM), and automated feature analysis (AFA) option equipped with ASPEX PSEM. Factsage was used to calculate the equilibrium inclusion composition. Based on the calculation, an inclusion evolution mechanism was proposed. Furthermore, line scanning analysis was used to elucidate the intra-granular acicular ferrite (IAF) nucleation mechanism. The result showed that two different inclusions exist in sample steel: (Mn-Al-Si-Ti-La-Ce-O) +MnS complex inclusion and isolated MnS inclusion. Almost all nucleation sites for IAF are complex inclusions, while single MnS inclusion cannot induce IAF. A possible formation mechanism of complex inclusion is proposed based on calculated results using Factsage, which agrees well with experimental results. A Mn-depletion zone (MDZ) which exists adjacent to the (Mn-Al-Si-Ti-La-Ce-O) +MnS complex inclusion can account for the IAF formation. However, the low volume fraction (1.49~10- 7) of effective inclusion may result in only 10% (volume fraction) IAF.
关键词:
Intra-granular acicular ferrite
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