Papers by Keyword: Refining Slag

Abstract: The desulfurization ability of CaO-Al₂O₃-SiO₂-TiO₂ slag at 1873 K was studied through theoretical calculation by using thermodynamic software FactSage. The effect of binary basicity is significant, compared with the mass percentage factors of Al₂O₃ and TiO₂. Under the optimal experimental conditions, with the binary basicity is 7, the mass percentage of Al₂O₃ is 30 % and TiO₂ is 3 %, the corresponding highest sulfur distribution coefficient for the slag are 58.14. While the content of TiO₂ in the CaO-Al₂O₃-SiO₂-TiO₂ slag is in a range lower than 3-4 %, the desulfurization ability of the CaO-Al₂O₃-SiO₂-TiO₂ slag is equal to that of the CaO-Al₂O₃-SiO₂ slag. The slag system with TiO₂ can meet the desulfurization requirements of steelmaking, which is a good way for resource utilization of solid waster containing titanium.

Abstract: In past years, the exploitation of mineral resource in our country was stressed on capacity and the solid waste recycle and innocent treatment was ignored. Much valuable metal is associated and coexist with waste, it is in difficult position for present technology to recycle valuable composition in that waste, which leads to valuable component loss and environment pollution. Therefore, the development and utilization of copper refining slag is in significance. In this paper, the advantages and difficulties to process refining slag by flotation method are discussed based on property analysis of copper refining slag. The refining slag is featured by high specific gravity, high concentration, and its particles distributing at both ends of small and large size. A flotation cell with special structure of barrier grid plate and multi-loop channel is developed for refining slag processing, which provides a proper way to solve the sediment problem during refining slag flotation. The application of CLF-40(effective volume,40m3) flotation cell for processing slag mixture from flash furnace and converter is expounded, the production index shows that the Cu grade is up to 27.18% at recovery of 83.93% when slurry concentrate being 70%

Abstract: In order to verify an alternative metallurgical process of phosphorus removal for solar grade silicon (SOG-Si), slag treatment of metallurgical grade silicon (MG-Si) was conducted followed by acid leaching in the present study. MG-Si containing certain amount of phosphorus and calcium was equilibrated at 1723 and 1773 K with several compositions of the CaO-CaF2 slags and phosphorus in molten silicon was confirmed to be removed into slag phase also by reducing reaction as a form of phosphide ion, P3-, in addition to the phosphate ion, PO43-. These contents were separately determined by a wet chemical analysis method developed by ourselves. Although the distribution ratio of phosphorus could not exceed the highest reported values of 3, subsequent leaching brought about considerably high fraction of P removal. The removal fraction of 95.6% was attained when 5 g of silicon was treated with 10 g of the slag at 1773 K followed by the acid leaching, which would be much higher than that expected by the ordinary oxidizing slag treatment. Although the possibility of reducing dephosphorization by slag treatment was clarified, more effective condition should be pursued by changing slag composition, calcium content of silicon, temperature, etc.

Abstract: The effect of different composition of refining slag on absorption rate of Al2O3 has been tested by experimental method in the CaO-SiO2-Al2O3-MgO-CaF2-FeO-MnO-P2O5 refining slag. The result shows: under specified condition, CaO/Al2O3 between 1.4 and 1.7, the slag has higher absorption rate of Al2O3,The absorption rate of Al2O3 raised with the increase of the content of CaF2 when the content of CaF2 less than 8%; the absorption rate of Al2O3 increased with the increase of the CaO/SiO2 when the CaO/SiO2 less than 3.5; the maximum absorption rate of Al2O3 is 0.0226 g•cm-2•min-1 when CaO/SiO2=3.48, MI=0.124.

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.

Abstract: The effect of the refining slag composition on the total oxygen content and inclusions in steel was investigated in 100 t UHP Electric Furnace – LF – Billet CC process. The test steel was 77B hard wire steel and Si-Mn alloy was used as the deoxidizer. Three types slag were used in the industrial tests, which including CaO-CaF2, CaO-CaF2 adding CaC and CaO-Al2O3 refining slag. The results shown that the lowest total oxygen contents of rolled bar can be gained using the CaO-CaF2 refining slag adding CaC, which is 0.0036%, while the total oxygen contents of rolled bar using CaO-Al2O3 refining slag is higher a little than the heats using CaO-CaF2 refining slag. The CaO-SiO2 and CaO-Al2O3-SiO2 compound inclusions with the size of about 5 μm are the main inclusions in the heats refining by the CaO-CaF2 refining slag in the rolled bar, but the pure, indeformable Al2O3 inclusion can also be found with the size of about 10 μm. The CaO-Al2O3-SiO2 and Al2O3-SiO2-MnO compound inclusions are the main inclusions in the heats refining by the CaO-CaF2-CaC refining slag, but most of the inclusion shape is irregular with bigger size of about 10 μm. Similar with the heat using CaO-CaF2 refining slag, the pure Al2O3 inclusion with edge angle can be found in the rolled bar. The inclusions in the rolled bar treated by CaO-Al2O3 refining slag are CaO-Al2O3-SiO2 compound inclusions, most of which are nearly globular shape with the relative small size of about 5 μm. All of the inclusions in rolled bar lie on the low melting zone in the CaO-Al2O3-SiO2 ternary phase diagram in the heats using CaO-Al2O3 refining slag. The similar condition appeared on the most of the inclusions in the heats using CaO-CaF2 and CaO-CaF2 refining slag adding CaC, while part of which are lied on the high melting zone. Therefore, considering of the plastic deformation ability, the CaO-Al2O3 refining slag is the best slag for the melting process of hard wire steel.

Abstract: The variation of non-metallic inclusions and total oxygen contents in different steel grades were investigated by taking samples in steelmaking process, including gear steel, anchor chain steel, hard wire steel, bearing steel and spring steel. The inclusions mainly were Al2O3, MnS, and their composite inclusions in aluminum killed steel at the beginning of LF refining due to addition of FeAl alloy during the tapping from EAF and feeding of Al wire in LF process, and then Al2O3 inclusion changed to the Al2O3 - CaO composite inclusions after feeding of SiCa wire. The inclusions at the beginning of LF refining mainly were MnS, SiC and their composite inclusions in non-aluminum killed steel due to addition of the composite deoxidation and slagging agents (mainly including CaC2 and SiC) when EAF taping, while the inclusions in tundish mainly were MnS, CaO - SiO2 - Al2O3 composite oxide - sulfide inclusions. It is showed that the inclusions in bearing steel and spring steel samples were mainly globular oxide inclusions and silicate inclusions with higher rated results. Therefore, the refining process should be improved to remove globular oxide inclusions. The inclusions in molten steel were controlled by enhancing the diffusion deoxidation process, adjusting and controlling the basicity and composition of refining slags, respectively, and satisfactory results were obtained. The industrial test shows that the total oxygen content of the aluminum killed steel in the test heat after feeding wire reached the minimum value, which indicates that the optimized slag has a strong ability of absorbing Al2O3 inclusions. For non-aluminum killed steel, the total oxygen content was 0.0027 % to 0.0029 % in rolled products. The inclusions in the end of refining and rolled product were small and dispersed composite inclusions, and the separate Al2O3 inclusions can not be found in the non-aluminum killed steel after optimization of the refining process.

Abstract: The principal purpose of this paper are to determine the viscosity of refining slag with the features of high crystallinity and strongly oxidizability, and to solve the problem that slag sticked onto the RH immersion tube during the RH refining process. Then, the fluid length method was used to determine the viscosity, and the effect of compositions on melting point and viscosity of refining ladle slag was studied. Overall, the relationship between viscosity and fluid length was acquired, and it achieved the slag with lower melting point and good fluidity which can avoid slag building-up on RH immersion tube by adjusting the basicity of refining slag to 4-5, the content of Al2O3 to 14-15% with additives.