Drain Free Filtration (DFF)—A New CFF Technology

The Minerals, Metals &Amp; Materials Series

Akhtar³

et al. 2021

Self Cite

Grain refinement of aluminium and its alloys is a common industrial practice. Fine equiaxed, grain structure leads improved castability, strength, machinability, formability, and good surface finish. Filtration is one of the widely used technologies to remove inclusions from the melt. Ceramic Foam Filters (CFFs) are commonly used to clean the aluminium melt before the casting process. However, at a high inclusion load and with grain refiner addition, reduced filtration efficiency is well known to occur. In the current work, the filtration behaviour of CFFs with three different levels of inclusions and grain refiner has been systematically studied in plant scale pilot trials at Hydro's reference centre in Sunndalsøra, Norway.The results show that oxide films capture grain refiner particles. Grain refiners tends to agglomerate heavily with inclusions at higher inclusion content. These heavy and compacted small clusters are more likely to be released from the CFF during the filtration process. Little effect from grain refiner addition on filtration efficiency is observed when the level of grain refiner and chips addition is relatively low or when both are high, but not with high grain refiner addition with middle level of inclusion load. The threshold of the grain refiner addition effect is further discussed in this paper.

Section: Methodsmentioning

confidence: 99%

The Effect of Grain Refiner on Aluminium Filtration

The Minerals, Metals &Amp; Materials Series

Akhtar³

et al. 2021

Self Cite

“…The metal temperature in launder was measured and held at approximately 730 °C. The priming of 80 PPi filters was done by using the new Drain Free Filtration (DFF) technology developed by Hydro [26] ; 80 kg of inclusion chip blocks was introduced into the melting furnace approximately 20 to 30 minutes after filtration started. Two Liquid Metal Cleanliness Analyzers (LiMCA) II were used and placed both before and after the filter as illustrated in Figure 1.…”

Section: B Experimental Processmentioning

confidence: 99%

Effect of Inclusion and Filtration on Grain Refinement Efficiency of Aluminum Alloy

et al. 2022

Metall Mater Trans A

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It is well known that the filtration efficiency of ceramic foam filters (CFF) on aluminum melt can be significantly reduced by the addition of grain refiner particles under a high inclusion load. Also, it is usually considered that the filtration process has little impact on grain refinement efficiency. In this work, the influence of inclusions and filtration on the grain refinement effect of AA 6060 alloy has been studied. This was done through TP-1 type solidification experiments where the aluminum melt prior to and after the filter during a pilot-scale filtration test was investigated. In the experiments, 80 PPi CFFs were used to filtrate aluminum melt with an ultra-high inclusion load and two addition levels of Al–3Ti–1B master alloys. It is found that both inclusions and filtration significantly reduce the grain refinement efficiency of the grain refiner master alloys. A detailed characterization of the used filters shows that the reduction of grain refinement efficiency is due to the strong adherence of TiB2 particles to the oxide films, which are blocked by the CFF during filtration. A grain size prediction model based on deterministic nucleation mechanisms and dendritic growth kinetics has been applied to calculate the solidification grain size and estimate the loss of effective grain refiner particles during filtration. It is shown that due to the strong adherence between TiB2 particles and oxide films in the melt, the high addition level of aluminum chips also has an influence on reducing the grain refinement efficiency of aluminum melt without filtration. The results of this study extended our understanding of the behavior and performance of inoculant particles in CFF and their interactions with the inclusions.

“…The metal temperature in launder was held at approximately 730°C. By using the new Drain-Free Filtration (DFF) technology of Hydro, [29] the filter was first primed from below, and then a normal filtration process began. The liquid in the melting furnace was removed at the end of each day.…”

Section: A Materials and Experiments Proceduresmentioning

confidence: 99%

The Influences of Grain Refiner, Inclusion Level, and Filter Grade on the Filtration Performance of Aluminum Melt

Akhtar

et al. 2021

Metall Mater Trans B

Self Cite

The addition of grain refiner particles in the aluminum melt is known to reduce the filtration efficiency of ceramic foam filter (CFF). In the present work, a systematic study on the influence of the addition level of Al-Ti-B master alloys and the inclusion level on the filtration performance of aluminum melt has been investigated by pilot-scale filtration tests using 50 PPi and 80 PPi filters. The inclusion level of the melt has been measured using both LiMCA and PoDFA. For 80 PPi CFF, the N20 inclusion (diameter larger than 20 μm) value in the post-filtrated melt does not increase when an ultra-high level of inclusions is introduced in the form of chips. For the melts with a low level of grain refiners (~ 0.5 kg/ton), the filtration performance of CFF is not affected by grain refiners, regardless of inclusion load. An addition of 2.0 kg/ton grain refiners reduces the filtration performance for melts with a high inclusion level, where post-filtration inclusions with the size of 15-20 µm were significantly increased. It is found, however, for the melts with an ultra-high inclusion load, the filtration performance of 80 PPi CFF is not affected by the grain refiner addition up to 2.0 kg/ton. The interactions between inclusions and grain refiner particles and the filtration mechanism have been studied by characterizing the spent filter and measuring the pressure drop during the filtration process. It is revealed that the strong adherence between oxide film with grain refiner particles dominates the grain refiner influence on the filtration performance of CFF. During the filtration process, oxide films have strong influences on the capturing of other inclusions such as oxide particles and TiB2 particles by the filter. A mechanism based on the interactions between oxide films and grain refiner particles is proposed to explain the CFF performance under the influence of grain refiner.