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| Thermodynamics of Calcium Treatment for 20CrMnTiH1 |
HAN Zhijun1,LIN Ping1,LIU Liu1,CUI Jingyu2,ZHOU Deguang3 |
| 1. Metallurgical Department, Central Iron and Steel Research Institute, Beijing 100081, China;2. Research Institute of Shougang, Beijing 100041, China;3. Steelmaking Plant of Shougang, Beijing 100041, China |
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Abstract 20CrMnTiH1 is a aluminumdeoxidized resulphurized steel. Normally calcium is added in the last stage of refining process to modify oxides and sulphides to improve the product quality. Based on the thermodynamic equilibrium, the conditions of Al2O3 modification and CaS formation for Ca treated 20CrMnTiH1 steel were discussed in detail. The calculated results show that in the steel melt containing 0.02%0.03%［S］, 0.02%0.04%［Al］ treated by calcium, CaS is easily formed and it is difficult modify Al2O3 into low melting point C12A7. With analysis of the steel sample and blocked nozzle by SEMEDS, it was found that there were CaS and not fully modified calciumaluminate in the steel. Inclusions which caused nozzle blockage during casting were mainly of CaS and CA. The calculation agreed well with the SEM observation. Counter measures to avoid nozzle blockage are proposed.
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Received: 01 January 1900
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2007, Vol. 42 
