Study on Slag Forming Route of Dephosphorization in Combined Blown Converter

In order to achieve the purpose of high-efficiency dephosphorization by single-slag method during the combined blown converter steelmaking process, the CaO-SiO2-FetO-MgO-MnO-P2O5 slag system was taken as the research object, and the slag-forming route of dephosphorization was studied. The effects of slag compositions on the liquidus and the contour map of phosphorus distribution ratios (recorded as Lp) were calculated by thermodynamics software FactSage, and then the theoretic slag-forming route of dephosphorization was obtained. The effects of slag compositions on dephosphorization rate and Lp were studied by a high-temperature experiment. Based on the results of the theoretic calculation and high-temperature experiment, the actual slag-forming route of dephosphorization by the single-slag process in the combined blown converter was obtained: The initial slag composition should be around 15.0%CaO-44.0%SiO2-41.0%FetO. The composition of high-efficiency dephosphorization slag should be around 50.8%CaO-24.2%SiO2-25%FetO. The final slag composition should be around 65.6%CaO-28.3%SiO2-6.1%FetO. After using the actual slag-forming route in the production, the dephosphorization rate was increased by 3.6%, and the consumption of slagging materials was reduced by 3.78 kg/t.

The investigation on the middle period dephosphorization in 70t converter

An experimental test is carried out on the 70t converter in Masteel to study the law of middle period dephosphorization in the smelting period. It is found that the dephosphorization rate is slow in the early and middle period of smelting and the content of the final P in steel cannot reach the standard due to the low oxidation of slag. The content of the final P in steel can be controlled within 0.02% by adding ore to the molten bath in the middle period and raising the lance position. The experimental test shows that the dephosphorization can still be achieved by a large margin if appropriate slag conditions are maintained in the middle period when the C and O reactions are strong. By theoretical calculation, it is concluded that the slag content should be controlled between 15 and 23%, and the basicity of slag should be between 2.5 and 2.8 in the middle period of production. Through the observation of experimental slag by SEM, it is found that the limiting factor of dephosphorization in the middle period under the test conditions is that the dephosphorization speed is too slow due to the low oxidation, rather than the solidification of phosphorus.

Removal of Phosphorus from High-Phosphorus Manganese Ores by Ammonia-Ammonium Carbonate Leaching Method

High-phosphorus manganese ores provide an important source of manganese, which is regarded as an irreplaceable material in the steel industry. The ammonia-ammonium carbonate leaching method was proposed for the removal of phosphorus and extracting manganese from high-phosphorus manganese ore, both effectively and environmentally. To explore the dissolution behavior of phosphorus and manganese in the ammonia-ammonium carbonate solution, the effect of the ammonia-to-ammonium carbonate concentration ratio, the leaching temperature, and the liquid-to-solid ratio on manganese extraction and dephosphorization rate were investigated. In addition, the composition of precipitated manganiferous sample, which was obtained from high-phosphorus manganese ores by ammonia-ammonium carbonate leaching process, was also studied. The results indicated that more than 99.2% phosphorus was removed and more than 83.5% of manganese was extracted by ammonia-ammonium carbonate leaching under the following conditions: ammonia to ammonium carbonate concentrations: 14:2 mol/L; liquid/solid ratio: 5:1 mL/g; leaching temperature: 25 °C; The precipitated manganiferous sample has little impurities, Mn% is 44.12%, P% is 0.02%, P/Mn = 0.00045.

Fundamental Research on Gasification Dephosphorization with Coke Powder Reducing Converter Molten Slag

In order to realize the gasification dephosphorization process in converter slag splashing stage for avoiding the P enrichment, and the dephosphorized slag can be left for recycling in subsequent furnaces. The experiment of reduction of converter slag by coke powder in laboratory was carried out, The results show that with the increase of the experimental temperature, the gasification dephosphorization rate of coke powder gradually increases, and the gasification dephosphorization rate reaches up to 82.35% at 1900K. The gasification dephosphorization rate decreases with the increase of slag basicity. When the coke powder is added in a sufficient amount, increasing properly the FeO content of slag is favorable for the gasification dephosphorization reaction; when the coke particle size is between 0.5 and 2.5 mm, the gasification dephosphorization rate changed little, about 58%, but when the coke particle size between 2.5 and 3.5mm, the gasification dephosphorization rate dropped to 52%. The results provide some theoretical guidance for industrial development.

Research on coherent jet oxygen lance in BOF steelmaking process

The properties of conventional supersonic oxygen jet and coherent jet were simulated by Fluent in this paper. Their velocity field and jet radius were analyzed comparatively. The attenuation of gas jet was slowed down by the coherent jet oxygen lance. Besides, the effects of annular flow rate on the central oxygen jet velocity were also researched. It is showed that the core of the jet is gradually prolonged with the increase of annular gas flow rate. Based on the simulations, the designed coherent jet oxygen lance was experimented in 35 ton converter. It is found that the end-point phosphorus content is decreased from 0.024 to 0.016%, and dephosphorization rate is increased significantly, the average consumption of steel material is reduced by 3.4 kg/t, and iron-loss of slag is also reduced, which is favorable to improve oxygen utilization and metallic yield. This research provides good foundation for coherent jet technology promotion and application in Basic Oxygen Furnace (BOF).

Numerical Model of Dephosphorization Reaction Kinetics in Top Blown Converter Coupled with Flow Field

A 3D transient numerical model of dephosphorization kinetics coupled with flow field in a top blown converter was built. Through the model the dephosphorization reaction rate influenced by the oxygen jets and the steel flow were simulated. The results show that the dephosphorization rate at the droplet metal–slag interface is two orders of magnitude faster than that at bath metal–slag interface. When the lance oxygen pressure increases from 0.7 to 0.8 MPa, the dephosphorization rate increases notably and the end content of P has a decrease of 19 %. However, when the pressure continues rising to 0.9 MPa, the dephosphorization rate has no significant increase. In addition, the lance height shows a nearly linear relation to the end P content of steel, that the lower the height, the faster the dephosphorization rate.

Experimental Research on Influencing Factors of Melting Reduction for High-Phosphorus Titanomagnetite Pellets

Reduction of high-phosphorus titanomagnetite was studied for future comprehensive utilization of resource. Experimental temperature (T), burden alkalinity (CaO/SiO2) and carbon-oxygen ratio (C/O) had an influence on the content of [P] and [S] in hot metal. Highest dephosphorization rate in hot metal appeared at C/O=1, high temperature was beneficial to desulphurization, but not for dephosphorization. High CaO/SiO2may decrease the content of [P] and [S]. C/O and CaO/SiO2had great influence on the content of [P] and [S] in hot metal.

Cr and Ni Recovery and Oxidational Dephosphorization of Stainless Steel Dust during the Iron-Bath Smelting Reduction Process

According to the comprehensive utilization of 300 series and 400 series stainless steel dust (SSD), and the dephosphorization of the reclaimed Cr-Ni contained hot metal, an experimental method of smelting reduction in iron-bath and oxidational dephosphorization was studied. The result shows: The yield rate of Cr in 300SSDand 400SSDis 98.13% and 98.39% respectively, the yield rate of Ni is almost 100%; During the dephosphorization, through the BaO and CaO-BaO based dephosphorizer has a higher Dephosphorization rate, it can bring pollution problems and the cost is too high, however, under some circumstance when the requirement of phosphorus content is not critical, the CaO based dephosphorizer can also achieved the dephosphorization goal.

Research on Low-Phosphorus Steel Melting by Semi-Steel

In this study, double-slag method is used to melt low-phosphorous steel by semi-steel. The results show that, the average phosphorous content of the aimed molten iron of BOF is 0.0052% and after the first slag pure-out, the dephosphorization rate is 56.2%, while the total dephosphorization rate of BOF melting is 92.46%, rang from 91% to 93.4%. Low phosphorous content alloy and slag-stopping tapping technology is adopted and rephosphorization of molten iron is controlled in 0.002%. Finally the average phosphorous of the finished product is 0.0064%, range form 0.0055% to 0.0071%, which means that Pangang Group can produce the steel with phosphorous content is less than 0.008%.

Effect on Inclusion and Microstructure of Ultra-Low S and Low P Steels with Vacuum Treatment

The simultaneous desulphurization and dephosphorization of molten steel with CaO-based slag containing BaO for vacuum treatment, and inclusion in steel and microstructure of steel are carried out separately. These results show that desulfurization rate exceed 92% and dephosphorization rate exceed 50% , final [S] content and [P] content in molten steel are less than 0.0024% and 0.020% respectively for all heats, and the lowest final [S] content and [P] content are 0.0012% and 0.010% respectively, they satisfy the demand of ultra-low S steels and low P steels; Comparing a grade 1.5 of inclusion level of the compared sample without vacuum treatment, inclusion level of these treated samples with vacuum is all less than grade 1.0 and that is less than grade 0.5 for 78% of treated samples; And micro-structure of the compared sample is ferrite + pearlite in steel base, but micro-structure of these treated samples is all needle-like ferrite + pearlite + netted ferrite in steel base and netted ferrite + pearlite in local area. This kind of fiber structure which comes from netted ferrite + needle-like ferrite and grade 0.5 of inclusion level can make steel possess better mechanical properties.