Formation of the primary structure of cast slabs from aluminum alloys during their twin-roll casting

Abstract

This paper demonstrates the feasibility of producing thin-thin slabs from a wide range of aluminum alloys using the twin-roll casting method. In the course of the research, the design and technological solutions of the currently known methods of continuous casting and rolling of sheet metal products were analyzed. In a laboratory setup for strip metal casting, the physical and technological parameters (such as temperature, casting speed, and heat removal rate) were tested to ensure a stable process for the production of thin-thin slabs (1–5 mm) from the aluminum alloys under study. For the first time in the field of metallurgy, the improvement of twin-roll casting technology allowed the cast thin slabs from wide-range aluminum alloys, specifically EN2024 (D16) (≥ 130 °C) and EN7075 (B95) (≥ 160 °C), to be produced.

In the initial phase of the research, the impact of the heat removal rate from the solidifying metal on the primary structure of the cast blank was investigated. It is demonstrated that, irrespective of the cooling rate, the α‑phase serves as the basic structure that determines the mechanical characteristics of the metal in cast workpieces for all the studied aluminum alloys. It was demonstrated that as the cooling rate increases to a level characteristic of twin-roll casting, the α‑phase in cast slabs exhibits a more uniform fine-grained structure. In this case, the small inclusions of dispersed intermetallic and eutectic phases present in the structure of cast slabs are evenly distributed across their cross-sections. As is known, there is a hereditary phenomenon between the primary structure of cast slabs and the quality of the final metal product. This relationship was confirmed by the improved strength characteristics of strips obtained by rolling experimental slabs.