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Hard inclusions with high melting temperatures such as Al2O3 (2054°C) and MgO·Al2O3 (2135°C) generate nozzle blockage problems during continuous casting of Al-killed valve spring steel and are very detrimental with respect to fatigue properties. In the present paper, inclusion modification in Al-killed valve spring steel by Na2CO3 addition was investigated in the laboratory using a graphite tube resistance furnace. The results show that inclusions with high melting temperature can be successfully modified into Na2O-containing inclusions with lower melting temperatures by the addition of Na2CO3. The effectiveness of inclusion modification can be enhanced by increasing the Na2CO3 addition and/or decreasing the amount of Al. This suggests that Na2CO3 addition could possibly be a substitute for Ca treatment as a method for preventing nozzle blockage during continuous casting of Al-killed steel.
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Chen et al. (2018) studied this question.
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