THE MANUFACTURING, USE AND PLANT TEST RESULTS OF TF COMBO BAGS FOR DC SHEET INGOT CASTING

In the last decade, the molten aluminum distribution in the ingot head of DC sheet casting ingots has been achieved using mostly a combo bag made of fiberglass fabrics. Some of these fabrics are open-weave materials while others are solid fiberglass fabrics sewn together. This bag is usually soft and flexible and extensive sewing operations are required to manufacture it. The bag can deform and this can effect not only the distribution but also the molten metal temperature profile around the mold and at the end, the final ingot quality. This paper will review the production and use of a new combo bag for DC sheet ingot casting. The paper is divided in two parts. The first part will deal with the manufacturing of the TF combo bag. Description of the used fabrics as well as the new production techniques to manufacture that bag will complete this first part. Part two (2) will present the test results of the TF combo bag used at different plants to cast AA-1045, AA-3003 and AA-5052 alloys. The following variables and measures will be discussed: Cast start-up, actual metal flow observations, ingot surface finish, temperature profile around the mold, and finally, results from the rolling plant. Comments from an operation point of view on the use of the TF combo bag will be also presented. TF combo bag Introduction This graph shows the evolution of the beverage can downgaging over the years. The constant reduction in can thickness has forced the aluminum producers to improve the overall molten metal cleanliness. Usually, molten metal cleanliness is maintained up to the distribution trough. However, a good distributor is the key component to maintain that metal cleanliness. Figure 1. Beverage downgaging Last year, at TMS, Pyrotek presented the ReMAD technology which consists of a reusable composite frame coupled with an preshaped inner bag (Figure 2.) to distribute molten aluminum in the ingot head. This technology is still at the β phase testing. However, the pre-shaped inner bag has led to the TF combo bag technology which is the subject of this presentation. This paper will review the TF combo bag distributor development and plant trial results to fulfill today’s high quality standard of cast sheet ingots. Molten aluminum is mainly distributed in the mold of DC sheet ingot using a combo bag made of sewn fiberglass fabrics. Some of these fabrics are open-weave materials while others are solid fiberglass fabrics. The main functions of the combo bag are the following: • It acts as metal distributor in the ingot head. This distribution determines the temperature profile around the mold and it influences the final metallographic structure. • The combo bag should also minimize turbulence, retain oxide patches and collect any large particles.