Comprehensive utilization of metal materials for steelmaking at Baosteel

Optimization of scrap utilization, through maintaining a reasonable heavy scrap ratio, determination of scrap yield, development of substitutes for scrap, recycling of high-alloy scrap and optimization of scrap utilization technology, was investigated in this paper, in terms of the supply of metal materials, production cost, production quality and environment protection. Then, recycling of solid waste resources was discussed, and the utilization conditions and methods of slag-steel, slag-iron, steel-slag, etc. were determined. Finally, the management system for comprehensive resource utilization was introduced.

Improvement of Service Life of Small Furnace Covers on 150 t Refining Ladles

The factors restricting the life of the refining furnace cover were introduced,including the airflow erosion of the refining dust removal system,the melting loss caused by the arc radiation of the electrode,the chemical erosion and penetration of slag and gas,and the condition of refining slag.The improvement measures are adjusting the material of the small furnace cover from corundum to chrome corundum,using a large shaking table to vibrate,optimizing the size design of the small furnace cover,and appropriately thickening the weak areas in the triangular area.The average service life of the refining furnace cover has been increased from one week to two months,reaching 4 maintenance cycles,which meets the needs of the refining production.

Study on inner defects of continuously-cast blooms and soft reduction process

At the initial operation stage of the continuous bloom caster at Baosteel, a lot of central porosity and cracks occurred in blooms, especially in the blooms of high-pressure boiler steel. In this study, a model of heat transfer and solidification was set up to analyze the process of continuous bloom casting. Based on the model, the distributions of temperature field and shell thickness were obtained, the mushy zone was defined, and thereby the technology of soft reduction for blooms was developed. After several tests were conducted, a reasonable test plan was developed, which led to the determination of the optimal reduction zone and gauge reduction. Now, central porosity and cracks in blooms are almost avoided and the inner quality has been obviously improved.

Development of CO_(2) capture and utilization technology in steelmaking plant

The performance of a recycling process for CO_(2) capture and utilization of exhaust gas in the steelmaking plant was reported.A facility capable of capturing CO_(2) at 3200 m^(3)/h was established in the steelmaking plant,resulting in the CO_(2) production of 50,000 t/a.The CO_(2) concentration of the exhaust gas from the lime kiln increased from 25.0 to 99.8 vol.%using the comprehensive method of the pressure swing adsorption and cryogenic separation.The captured and purified CO_(2) was successfully applied in the converter process by the top blowing and bottom blowing.The utilization of CO_(2) was 3.5 m^(3)/t through these two modes.After optimizing parameters of CO_(2)-O_(2) mixed top blowing,the value of[C]×[O]and the content of TFe in slag were reduced by 1.33×10-4 and 1.27%,respectively,and the dephosphorization rate of the molten steel increased by 2.31%.For the CO_(2) bottom blowing,the[N]content in the molten steel was significantly reduced by 5.7×10^(-6).

Effect of Mg addition on formation of intragranular acicular ferrite in heat-affected zone of steel plate after high-heat-input welding

The effects of Mg content, inclusion size, and austenite grain size on the intragranular acicular ferrite （IAF） nucleation in heat-affected zone of steel plate after high-heat-input welding of 400 kJ/cm were investigated by welding simulation and observation using a scanning electron microscope equipped with an energy dispersive spectrometer and an optical microscope. The IAFs are observed in steel with Mg addition, and the volume fraction of IAF is as high as 55.4% in the steel containing 0.0027 mass% Mg. The MgO-Al2O3-Ti2O3-MnS inclusions with size around 2 μm are effective nucleation sites for IAF, whereas Al2O3-MnS inclusions are impotent to nucleate the acicular ferrite. The prior-austenite grain （PAG） size distribution in low Mg steel is similar to that in steel without Mg addition. The austenite grain with size about 200 μm is favorable for the IAF formation. In the steel with high Mg content of 0.0099%, the growth of PAG is greatly inhibited, and PAG sizes are smaller than 100 μm. Therefore, the nucleation of IAF can hardly be observed.

A comparison study on viscosity and heat transfer property of fluorinebearing and fluorine-free mold flux for casting silicon steel

A comparison study was conducted on viscosity and heat transfer property of the traditional fluorine-bearing(F-bearing)mold flux and the newly designed fluorine-free(F-free)mold flux for casting silicon steel.The results showed that the viscosity of F-free mold flux is lower than that of F-bearing mold flux,as the apparent activation energy of F-free mold flux is also lower than that of F-bearing mold flux confirmed by the kinetics results for viscous flow,which meant that the energy barrier of F-free mold flux that the migration of ion clusters needs to overcome is smaller,and thus leads to a lower viscosity of F-free mold flux.Besides,the research results of the heat transfer suggested that the comprehensive heat transfer coefficient of F-free mold flux is lower than that of F-bearing mold flux in all directions.One reason is that the true density of F-free mold flux increases from glassy state to crystalline state,while that of F-bearing mold flux is opposite.Another reason is that the air gap gets increased due to the volume shrinkage of F-free mold flux from glassy state to crystalline state and the solidification of the molten steel.These introduce a larger thermal resistance of F-free mold flux than that of F-bearing mold flux.Through the comparison,the designed F-free mold flux shows a better lubrication and capacity to control the heat transfer than the traditional F-bearing mold flux.

High-temperature modification and air-quenching granulation of steel slag

To solve the problem of difficult utilization of steel slag,the liquid steel slag was modified and the air-quenching granulation process was carried out to make steel slag into a value-added end product:air-quenching granulated steel slag.The granulated slag was tested to analyze the variation rule of slag properties under different modification conditions.Based on the phase diagram of CaO–Si_(2)O–FeO–MgO–Al2O3 slag system,the feasibility of blast furnace(BF)slag as modifier was determined.When the addition of BF slag was increased from 0%to 35%,following results were obtained.The slag fluidity was improved,and the air-quenching temperature range was expanded.Then,the yield of air-quenched steel slag increased,while the granulation rate,the degree of sphericity,the compactness were decreased.Furthermore,the air-quenching granulation process could substantially improve the stability and the amorphous content of steel slag.The maximum removal rate of free CaO was above 80%and the amorphous content was up to 95%.Taking the factors of yield and properties of granulated steel slag into full consideration,the optimum proportion of BF slag is around 15%.