Deformability of Oxide Inclusions in Tire Cord Steels
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THE diameter of steel cords can be less than 0.2 mm after hot rolling and cold drawing from billets. The breakage of steel during cold drawing and fabrication is mainly caused by nonmetallic inclusions, and is a crucial issue. The effects of inclusions on steel properties are different owing to their different plasticities. Nondeformable inclusions are extremely detrimental to the drawing performance of tire cord steels and can cause fracture[1]; therefore, deformable inclusions are required for such steels. The control of inclusions in tire cord steels has been reviewed and investigated.[2–6] Considering the deformation behavior of inclusions during hot rolling and cold rolling, several experimental investigations[7–10] and finite-element calculations[11,12] were reported. There have not been sufficient investigations so far on the
LIFENG ZHANG, WEN YANG, and YING REN are with the School of Metallurgical and Ecological Engineering of University of Science and Technology Beijing (USTB), Beijing 100083, China. Contact email: [email protected] CHANGBO GUO is with the School of Metallurgical and Ecological Engineering of University of Science and Technology Beijing (USTB) and also with the Qingdao Iron and Steel Group Co., Ltd., Qingdao 266000, China. HAITAO LING is with the School of Metallurgy Engineering, Anhui University of Technology, Ma’anshan 243002, Anhui, China. Manuscript submitted December 16, 2016.
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deformation of inclusions in tire cord steels, and the factors influencing their deformability are not clearly known yet. The inclusions in tire cord steels can be roughly classified into two categories[13,14]: the SiO2MnO-Al2O3 system and the SiO2-CaO-Al2O3 system. To achieve good plasticity, the composition of inclusions should be controlled by the regions having low melting points,[5,15] namely, the region around spessartine in the SiO2-MnO-Al2O3 system and that surrounded by anorthite-tridymite-pseudo wollastonite-gehlenite in the SiO2-CaO-Al2O3 system. The melting point is the temperature at which a substance changes from the solid state to the liquid state; this depends on the type of crystals and the associated forces, which are related to the strengths of covalent or ionic bonds. The inclusions exhibit plasticity at high temperatures owing to their softened state even though they are not liquids. Cold drawing of tire cord wires is usually carried out at room temperature, which is significantly lower than the solidus temperature of inclusions. Deformability will no longer have a direct relationship with the melting temperature. It is insufficient to control the inclusion composition only in regions with low melting points if the goal is to improve the deformation of inclusions. Some researchers have tried to identify other parameters that influence the plasticity of inclusions. Bernard et al.[16] studied the relationship between deformability and viscosity of the SiO2-MnO-Al2O3 and SiO2CaO-Al2O3 systems at high temperatures. Three composition fields were defined in the te
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