Development of Manufacturing Technologies to Increase Scrap Steel Recycling Into New Tires

This paper describes our projects efforts to develop innovative processing technologies that can enable a greater rate of recycling of steel scrap into the manufacturing of new tires since it is known that recycling steel scrap has the potential to reduce up to 90% of embedded energy when compared to carbon-based reduction from iron-ore. To resist harsh conditions during use, tires are built with steel cables constructed by assembling together fine wires of diameters as low as 0.2 mm. To obtain these fine wires, steelmakers first hot roll square billets to steel cords of 5.5 mm in diameter. Steel wire makers or tire manufacturers then cold-draw these cords to the finer diameters mentioned. During the cold drawing process, the fine wires are subjected to high levels of tensile and torsional stresses that are known to generate wire breakage when impurity levels are too high. For this reason, since most steel scrap has about 0.23% Cu originating from wires and motors in cars, current use of recycled steel scrap for producing new tires is limited to 20%, with the remaining coming from virgin iron sources, primarily pig iron. The goal of this work is to increase the scrap recycling rate from 20% to 80% while maintaining the industrial performance of the tire manufacturing process and the product quality. We will identify the location of Cu-containing phases, and develop, validate and optimize a processing step to mitigate the detrimental role of copper.