State of the Art in the Control of Inclusions in Tire Cord Steels - a Review

The control of inclusions in tire cord steels and techniques used in the production process are extensively reviewed. Inclusion and segregation requirements for the tire cord steel are discussed. The deformability of an inclusion is significantly affected by its Al2O3 content. Inclusions containing 20% Al2O3 has best deformability. The undeformable inclusions can be avoided by controlling the dissolved aluminum in the steel. Low basicity slags favour the generation of deformable inclusions. When the basicity R (=CaO/SiO2) = 0.8-1.5, the dissolved aluminum in the steel should be 1-5ppm to achieve 20% Al2O3 in inclusions. With R=1.0-1.4, in order to control [Al] in the range of 1-5ppm, the slag should contain approximately 8% Al2O3. The technologies to control inclusions in tire cord steels are reviewed including steel deoxidizer choice, steel refining method, slag carry over from BOF to the ladle, ladle stirring practice, control of nitrogen pickup and caster curvature. Control methods to decrease the central segregation in the tire cord steel are briefly reviewed, such as electromagnetic stirring during continuous casting.