Papers by Keyword: Mold Powder

Abstract: In this paper, the carbonization mechanism in ULCS continuous casting was discussed. It was found after analysis that carbonization was influenced by three points (the contact of powder slag layer and molten steel, the carbon pick up of carbon-rich layer and carbonization in mold). At the same time, some measures were put forward (the use of exothermic cast-on mold powder, the content of the free carbon should be reduced in the mold powder, carbon blacks is used as carbonaceous material, the use of carbon-free mold powder, stabilizing CC operation, adding MnO₂ to mold powder, viscosity of mold powder should be enhanced appropriately).

Abstract: In order to solve the problem of mold powder entrapment which is one of the affecting factors on faint-sliver defect in IF cold-rolled steel sheet in casting process, continuous casting process is optimized. Based on the analysis of the defect, the composition of mold powder is optimized. Otherwise, surface tension and viscosity of mold powder are raised. With theses countermeasures, mold powder entrapment and casting subcutaneous slag is decreased obviously. In addition, the rate of faint-sliver defect in cold-rolled IF steel sheet has been reduced from 5.21% to below 1.0%.

Abstract: The continuous casting technologies of the new square/round billet continuous caster in Panzhihua Steel have been studied. And on this basis, the effect of process parameters of primary cooling, mold powder, secondary cooling and electromagnetic stirring (EMS) on billet quality is investigated. With these studies, the continuous casting process is optimized, and the quality of square/round billet is improved as well. Comprehensive technologies for quality control of square/round billet in Panzhihua Steel have been proposed. The results of industrial tests show that the accept rate of surface quality for square billet is 98.44%, and that is 97.42% for round billet; the comprehensive rate below level 1.0 of internal defects of center porosity, center segregation and center cracks is more than 97%, and carbon segregation index is in the range of 0.93~1.09. The quality of square/round billet can meet the requirement of consumers absolutely.

Abstract: Slab quality affects the quality of hot rolled sheet significantly. There were serious transverse corner cracks on continuous casting slab of 510L steel plate in Panzhihua Steel before. Based on this, some effective countermeasures are put forward, such as the optimization of ratio of heat flux on narrow side and broad side of casting slab and mold powder, as well as the stabilization of casting speed and working condition of caster. With these countermeasures, transverse corner cracks on continuous casting slab have been significantly reduced, and the lines and peeling defects on hot rolled sheet reduce from 30% to 0.

Abstract: Mold powder entrapment is one of the affecting factors on faint-sliver defect in IF cold-rolled steel sheet in casting process. Based on the analysis of the defect, the composition of mold powder is adjusted. Otherwise, surface tension and viscosity of mold powder are raised. After taking these measures, mold powder entrapment and casting subcutaneous slag is decreased obviously. In addition, the rate of faint-sliver defect in cold-rolled IF steel sheet has been reduced from 5.21% to below 1.0%.

Abstract: Nozzle blockage is easy to take place in continuous casting process when producing 38CrMoAl steel due to high content of aluminum ([Al]=0.7%~1.1%). Slag-steel reaction will lead to large transformation for composition of molten steel and performance of slag on the condition of traditional high content of SiO2 in slag. And it will reduce the cleanliness of steel as well. The control target of refining slag and tundish powder has been gotten through the analysis of refining & continuous casting characteristics of high aluminum steel. Based on this, the content of Si and Al in molten steel can be controlled accurately, and the cleanliness of steel has gone to a higher level. Moreover, mold powder with high basicity and vitrification ensures the stability of slag after sorbing Al2O3 inclusions in theory. Continuous casting can be carried out successfully with the control of inclusion morphology through slag washing during tapping. Industrial practice shows that Si content is 0.25%~0.40%, Al content is 0.80%~1.00%, S content is below 0.004% and T[O] is below 0.0015% in steel products. Moreover, casting bloom with good surface quality is achieved, and the rate of bloom without cleaning is as high as 100%. With all these countermeasures, 38CrMoAl steel can be continuously cast for more than 6 heats.