Study On The Effects Of Refractories On The Evolution Mechanism Of Inclusions In Tire Cord Steel

Inclusions with higher hardness and melting point can act as breakage initation sites and increase breakage rate during the cold drawing process of tire cord steel.So,it is important to reduce the melting point of the inclusions in steel to make them deformable.The influence of refractories on the evolution mechanism of inclusions can not be neglected during refining process.Focusing on this aspect,some laboratory experiments were conducted to investigate the effects of different refractories(Al2O3 and MgO)on the inclusions in tire cord steel in the present study.The effect difference of these two kinds of refractories was discussed.Meanwhile,considering the entrainment possibility of some non-deformable exogenous inclusions,the effect of these refractories on the evolution mechanisms of three kinds of exogenous inclusions(MgO,spinel and Al2O3 inclusions)in tire cord steel was also investigated.In the present study,no slag is taken into account.The mian results and conclusions are given as follows:(1)As expected,the dissolution of Al2O3 from alumina refractory can increase the dissolved Al content in steel,which results in a significant increase of Al2O3 content in SiO2MnO-Al2O3 system inclusions and SiO2-Al2O3-CaO system inclusions.With reaction time,these two kinds of inclusions eventually change into high melting point inclusions due to the high content of Al2O3,which is not conducive to the plasticity of inclusions.(2)MgO refractory has a significant effect on inclusions.MgO refractory could lead to the rise of the MgO content in SiO2-MnO-Al2O3 system inclusions and SiO2-Al2O3-CaO system inclusions.The increase of MgO content to a certain extent reduces the melting point of SiO2MnO-Al2O3 system inclusions,and keep them in the low melting point region.It is noteworthy that the Al2O3 content in these two kinds of inclusions could also be evidently increased,when a trace amount of Al2O3 exists in the MgO refractory.Compared with Al2O3 refractory,MgO refractory is benefit to the plasticization of inclusions,but high purity of MgO refractory is very necessary.(3)Without the influence of slag,MgO refractory has alsmost no effect on the exogenous MgO and spinel inclusions,and these two kinds of inclusions could stay stably in liquid steel.But the results of thermodynamic calculations implied that MgO inclusions will eventually change into spinel inclusions under the influence of liquid steel.The corrsion of MgO refractory therefore is one of the major sources of spinel inclusions detected in the cord steel.(4)Influenced by MgO refractory,Al2O3 inclusions in liquid steel would finally transform into spinel inclusions.The spinel inclusions found in cord steel may also originate from exogenous Al2O3 inclusions(e.g.from alloys).