Melt refining and purification processes in Al alloys: a comprehensive study

Abstract

Aluminum and its alloys having lots of advantageous properties are among the most-used metallic materials. So, it is of immense importance to find suitable processes and methods leading to high-quality purified Al melt. In this regard, there are numerous challenges in achieving high purity Al melts, such as its propensity to react with air, oxygen, and water vapor, the presence of a variety of oxide, non-oxide, and solid particle inclusions that lead to the production of pores, cracks, pinholes, and dross, finally adversely influencing the overall quality of the product. The main methods of melt refining are fluxing, floatation, and filtration, but more sophisticated methods have also emerged. The best method for purification can be chosen based on the type of impurities and the desired level of purification. With the industrial development, the need to establish more cost-effective and simpler methods has increased, and in addition, methods should be considered for recycling large volumes of scarp Al parts that contain more impurities. Moreover, achieving high purity melt is also a vital issue for use in specific applications. The present article has been written to discuss the above issues and focus on the study of various methods of aluminum purification.

Hydraulic Characterization of Ceramic Foam Filters Used in Aluminum Filtration

“…CFFs are, however, wetted unfavorably by molten Al, so a metallic static head is required to prime the filters, i.e., the force needed to push the air inside the tortuous structure of the filters out, and subsequently infiltrate the porous material [ 1 , 3 ]. The filter capacity depends on the type and size of the particles collected [ 4 ]. The filtration modes, i.e., cake and/or depth filtration, as well as the flow velocity, play significant roles in the removal of the particles [ 5 ].…”

Solid Salt Fluxes for Molten Aluminum Processing—A Review

“…Several refining strategies are available to clean aluminum scrap, and in many cases, they are also used to refine molten primary aluminum [8]. Such practices, the most popular being fluxing, flotation, and filtration [23], can also be employed jointly, depending on the contamination level of the melt and the desired final metal quality. Briefly, the main types of impurities, which compromise the mechanical properties of aluminum alloy products and cause critical issues during the manufacturing processes, are described here.…”

A New Strategy on Designing Fluxes for Aluminum Alloy Melt Refinement

“…However, nonmetallic inclusions may be introduced from the raw materials used in the extractive metallurgical processes, from the refractory materials and the atmosphere during aluminum production, and even from the refining processes [ 5 ]. Nonmetallic inclusions (mainly aluminum oxide), including undesired gases (hydrogen), and oxides, borides, nitrides, carbides, and chlorides in aluminum may cause serious defects [ 6 , 7 , 8 ]. These inclusions cluster, causing the formation of pores in aluminum [ 9 ].…”