**4. Aluminum Alloy Grade, AA6111, Used in the Present Research**

Keeping in mind the suitability of the HSBC process to cast both ferrous and non-ferrous alloys, and knowing the usefulness of AA6111 aluminum alloy in the production of the lightweight body in white (BIW) automotive structures, AA6111 was selected for HSBC strip production. AA6111 is an alloy of Al-Mg-Si (Cu). It possesses higher mechanical strengths (i.e., 400 MPa), high formability, and good corrosion resistance. The main mechanism behind AA6111 s increased strength is precipitation hardening, along with the solid solution and work strengthening [16,17]. The alloying elements present in AA6111 are as shown in Table 1.


**Table 1.** Chemical composition of the AA6111 strip produced by the HSBC process, determined using the spark OES technique.

The casting of AA6111 strips via the HSBC process is comparatively new, and is presently in its development stages. It is, therefore, hoped that this paper will add fundamental knowledge to the information already existing on this subject, and help industries realize the versatility of the HSBC process to cast AA6111 aluminum alloy strips.

#### **5. Details of the Experimental Procedure**

AA6111 alloy was produced by first melting pure aluminum in a pre-heated induction furnace under a protective argon atmosphere, followed by the addition of Al-Mg, and Al-Mn alloys, etc. Good melt stirring was used, to ensure completely dissolved/mixing of the alloy additives into the pure aluminum. The melt was then de-gassed and Ti-B grain refiner was added in a conventional way. The AA6111 melt was then cast into the strips using the HSBC system. The step-by-step operation of the HSBC pilot caster is presented below.

The process started with the production of AA6111 alloy using the 600 lb induction melting furnace. Afterwards, the furnace was moved on rails to the casting station, where it was locked with the liquid metal delivery system. This consisted of a refractory cylinder (regulated by a servo motor) and a launder, as shown in Figure 1. Once the tight seal between the induction furnace and delivery system was ensured, the motorised refractory cylinder was allowed to enter into the induction furnace at a pre-selected speed, thereby displacing the molten metal into the launder. Once the molten metal reached the desired level within the launder, the stopper bar blocking the nozzle outlet was rapidly withdrawn, and liquid metal began to pour onto the belt. A weir and a dam were used to help prevent Al2O3 oxide skin from entering the nozzle slot, as well as to help in minimizing turbulence present within the flowing molten metal. The moving belt could also be equipped with two rotating side dams. Their purpose was to contain the molten metal once it leaves the nozzle slot, and to give a straight/smooth edge before it enters the minimill for hot reduction. To avoid any premature freezing, the entire delivery system and the refractory piston were preheated to approximately 500–550 ◦C, using electrical resistive heating systems.

To evaluate the bulk, as well as the surface, quality of the cast strips, samples were sectioned from the strip. All samples were polished and prepared for metallographic observations and analyzed under Leica DM IRM optical and Hitachi TM3030 scanning electron microscope. The surface roughness was measured using a 3D Nanovea profilometer. Results will be presented in later paragraphs.
