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A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y 2 0 1 9 2 7 consisting of two large stampings, one medium stamping, and three smaller reinforcements. The amount of alumi- num in the plant had tripled from 1% to 3%, and the aluminum offal account- ed for almost 15% of the plant’s total scrap value. Because Ford had convert- ed its entire production to 6111, Alcan expressed interest in purchasing the scrap and establishing a tolling system, returning the scrap from the stamping plant to the aluminum mill in Oswego. The preferred solution was to install a redundant scrap conveyor system for the aluminum, so that it could be kept separate from steel throughout the entire process. The problem was that CHSP was a large plant operating 20 major press lines. A separate system for aluminum would have been prohib- itively expensive and there was simply no room in the basement to install it. After several false starts, the plant decided instead to mix the two scrap streams and separate them at the exit. The mixed scrap flow was magnetical- ly sorted, with the steel directed to the shredder and compacted as before. The aluminum pieces fell directly into con- tainers that could be sent to the mill (Fig. 4). For the tolling loop to work, the system needed to achieve 99.85% steel separation from the aluminum. As ev- eryone quickly realized, this was far from easy. After multiple improvement loops and much added investment, the system peaked at 99.7% and only a ma- jor redesign could have improved it be- yond that level. The problem lay in the millions of small steel buttons generat- ed in a plant such as CHSP (Fig. 5). In any given day, it generated about two tons of steel buttons and a total of only 12-13 tons of aluminum scrap. Due to the capillary action of the stamping lubricants, the buttons would stick to any relatively flat aluminum surface, and no amount of shaking or magnetic pull would dislodge them. The offal needed a secondary process- ing pass at a scrap dealer before return- ing to Alcan, and so the system never achieved its cost reduction targets. But the scrap team learned an important lesson. For an effective tolling loop to work, the scrap would have to be sepa- rated at the press. Nissan implemented such a meth- od five years later at its Smyrna, Ten- nessee, plant when launching the aluminum hood and trunk lid for its 2002 Altima sedan. Compass Systems installed a pneumatic scrap conveying system that could be easily retrofitted in any existing stamping plant. In such a system, the aluminum offal is shred- ded, then carried across the plant in a high-speed airstream inside reinforced steel tubes. The metal is then captured in a cyclonic separator before dropping into containers (Fig. 6). Alcoa was by now Ford’s largest supplier. With increasing volumes and the prospect of a large new program on the horizon, the company felt confi- dent enough to open a new dedicat- ed automotive heat treat line. The new plant opened in Danville, Illinois, in 1997 and was strategically located to supply CHSP, Ford’s aluminum stamp- ing center. The inclusion of a modern cut-to-length line underlined its auto- motive focus. FORMABILITY AND PRE-AGING Even so, there was still plenty for aluminum metallurgists to work on. In the U.S., dent resistance was a key char- acteristic, which critically depends on strength after paint, while in Europe and Japan, formability and the ability to form flat hems were the dominant concerns. These differences explained why alloy 6111 had become the mar- ket leader in the U.S. and 6016 was favored in Europe. Unhappy to pay roy- alties to Alcan, Alcoa’s researchers set their sights on combining the strength of 6111 with the formability of 6016. In 1995, Alcoa registered 6022, a very lean alloy with a base composition and form- ability similar to 6016 (Table 1). The Fe and Mn contents, which help control Fig. 6 — Pneumatic scrap conveyor system. Fig. 4 — Separated aluminum scrap falling into a container at Ford’s Chicago Heights stamping plant. Fig. 5 — Engineering scrap from a typical hood inner panel. Note the number of small buttons.