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>Improvement in Internal Quality of Steel by Controlling Mould Slag Entrainment during Continuous Casting Operation
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Improvement in Internal Quality of Steel by Controlling Mould Slag Entrainment during Continuous Casting Operation
Steel products which are subjected to heavy and cyclic impact loading must be free from any internal defect to avoid stress concentration and material failure during service life. Bhilai Steel Plant (BSP) produces steel grades for such critical applications through BOF - LF - RH degasser route. The final products were subjected to ultrasound testing (UT) to check internal soundness of product and if defect found product is rejected altogether or downgraded. Many factors dictates the internal quality of steel such as slag entrainment during casting, gas entrapment during steelmaking and casting etc. Metallurgical investigation of the defective samples with the help of Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray Spectrometer (EDS) was carried out to find the defect nature and genesis. It was fond that entrapment of mould flux along with erosion of refractory from SEN during casting process was the main reason for internal defects. Caster operating data analysis and CFD modeling revealed that there was turbulence at mould meniscus which may have led to mould flux entrapment. According to the findings corrective actions were taken as modification of SEN design, SEN depth ramping schedule and SEN pre-heating strategy. These interventions helped in controlling UT defect and improve internal quality.
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