钢铁钒钛

Study on Process of Smelting Ferrovanadium by Tilting Furnace Using Mixture Vanadium Oxides

Yu Bin, Xian Yong, Sun Zhaohui, Jing Han, Tang Hongjian, Du Guangchao

2015, 36(4): 1-6. doi: 10.7513/j.issn.1004-7638.2015.04.001

Abstract(16) PDF(1)

Abstract:
Metallurgical characteristics of the aluminothermic reaction between vanadium oxides and aluminum,which is suitable for ferrovanadium smelting in tilting furnace by one-step and two-step approach,was studied. The effects of vanadium oxides ratio and aluminum coefficient were investigated on smelting efficiency and vanadium loss in slag. The results indicate that vanadium content in slag and the smelting efficiency both decrease with increase of V₂O₃ ratio in the vanadium oxides. When the ratio between V₂O₃ and V₂O₅ in raw materials changes from 0:8 to 6:2,vanadium content in slag reduces from 2.23% to 1.85% with the total weight of slag decreased by 19.7%,and the smelting time increases from 180 min to 194 min. Compared to one-step method,vanadium content in poor slag reduces from 1.85% to 0.44% and average vanadium content in poor and refining slag reduces to 0.88%,with aluminum coefficient increased to 1.20 in two-step smelting process. Dilution time reduces from 194 min to 146 min,yet refining time increases from 0 to 94 min and smelting time is prolonged by 46 min in twostep smelting process. Under the optimal conditions,the content of vanadium increases to 51.6% and the content of aluminum reduces to less than 0.3% in alloy,which improves the utilization rate of the aluminum and alloy quality.

Effect of Roasting Time on the Phase of Vanadium Slag

Shi Zhixin, Liu Jinyan, Wang Chunmei, Zhang Dafu

2015, 36(4): 7-12,18. doi: 10.7513/j.issn.1004-7638.2015.04.002

Abstract(28) PDF(1)

Abstract:
The morphologies,phase contents,existing forms and trace of vanadium in the roasted vanadium slag before and after leaching were comparatively analyzed. The results show that the morphology of the spinel transforms from compact and smooth surface to porous structure with unsmooth surface by roasting. There is no different in the phase species of the roasted vanadium slag and leaching residue by the MLA phase analysis data. However,the phase contents vary considerably between the roasted vanadium slag and leaching residue due to a great decrease of calcium vanadate. According to the test results of vanadium distribution,the solid solution of iron oxides cannot be leached by acid because of the impurities and plenty of vanadium dissolved in it. When the roasting time reaches to 360 min,the formed transition phase of pyroxene-calcium silicate hinders the diffusion of oxygen,leading to the package of vanadium in the solid solution which cannot be leached by acid.

Thermodynamic Study of Carbothermal Reduction of Panzhihua Ilmenite Concentrate in Vacuum

Liu Chang, Huang Run, Yuan Yi, Yuan Peng, Zhang Heng

2015, 36(4): 13-18. doi: 10.7513/j.issn.1004-7638.2015.04.003

Abstract(35) PDF(1)

Abstract:
In the present work,vacuum carbothermal reduction of Panzhihua ilmenite concentrate at various temperatures,system pressures and carbon addition was simulated using Fact Sage software. The results show that the total mass of the gas phase is increased and the mass of impurities in the slag phase is decreased with decrease in system pressure under 1 550 ℃ of temperature and 12% of carbon addition,which is beneficial to improve the reaction degree and obtain titanium slag with high quality. Under a pressure of 100 Pa and a temperature of 1 550 ℃,the reduction effect of the reaction can be improved with increasing carbon addition. Under 100 Pa of pressure and 12% of carbon addition,when the temperature exceeds 1 300 ℃,Mg,SiO,Mn vapor can be produced in the gas phase. The composition content of the gas and slag phase keeps at a stable level when the temperature is higher than 1 700 ℃,and the main oxides in slag phase are TiO₂ and Ti₂O₃ with 88% of grade for titanium slag.

Discussion on Lining Structure Design of Titanium Slag Melting Electric Arc Furnace

Gu Jing, Wang Shouzeng, Xia Dehong

2015, 36(4): 19-23. doi: 10.7513/j.issn.1004-7638.2015.04.004

Abstract(15) PDF(1)

Abstract:
Characteristics of the traditional heat preservation lining and the novel condensing lining were analyzed,and application of the condensing lining was put forward to prolong the service life of lining in the melting electric arc furnace for titanium slag. Wall temperature gradient and heat flux were calculated in the melting electric arc furnace with condensing lining. Taking 25 500 k VA melting electric arc furnace as an example,the increased 2.4% of heat loss with condensation lining is acceptable,considering the much higher maintenance cost and furnace shutdown loss with heat preservation lining. This paper can provide a method of determining the minimum thickness of the slag shell in titanium slag melting electric arc furnace with condensing lining. When the thickness of condensing lining composed of magnesite is 600 mm,the minimum thickness of titanium slag shell is 109 mm.

Study on the Preparation and Properties of Mg（OH）₂/TiO₂ Antimicrobial Flame-retardant Composite

Li Xue, Zhang Yan, Jin Ze, Zhang Ying, Liu Yunyi

2015, 36(4): 24-29. doi: 10.7513/j.issn.1004-7638.2015.04.005

Abstract(27) PDF(1)

Abstract:
Titanium dioxide （TiO₂） doped with nitrogen and tungsten,having a high photocatalysis performance,was prepared by sol-gel method with tetra-n-butyl titanate as raw material. Magnesium hydroxide （Mg（OH）₂）-titanium oxide composite materials were obtained by bubbling ammonia in mixture of the prepared TiO₂ and magnesium chloride （MgCl₂） solution,then heating and stirring. Employing XRD,SEM,XPS and FT-IR,the properties of the Mg（OH）₂/ TiO₂ composite were investigated. The results show that the size distributional width of the composite is 5.5200 μm and D₅₀ is 7.1800 μm. The composite is well dispersed and has a regular morphology,with tiny spherical TiO₂ particles adhered on the surface of the hexagonal flake powder. The spherical particles adhered on Mg（OH）₂ powder are anatase TiO₂,and there exists Mg-O-Ti chemical bonding between Mg（OH）₂ and TiO₂ in the composite. The weight loss of the composite is 24.5% under 300~400 ℃ with 387.1 ℃ of strongest endothermic temperature,meeting the requirements of Mg（OH）₂ flame retardant. The antibacterial properties of the composite were also tested by shake flask method,and the sterilization rate for coli can reach to 83.7% in 120 min.

Experimental Investigation of Precipitation Dynamics of Vanadium in HRB500 Rebar

Zhang Xinjian, Sheng Guangmin

2015, 36(4): 30-35. doi: 10.7513/j.issn.1004-7638.2015.04.006

Abstract(21) PDF(1)

Abstract:
The precipitation dynamics of vanadium in HRB500 rebar after rolling deformation was investigated experimentally by stress relaxation method. The test results show that two turning points appear in the stress relaxation curves under constant temperature and strain after rolling,which correspond to the starting and finishing of precipitation of vanadium respectively. The precipitation-temperature-time （PTT）curves of vanadium present the C shape. With the increment of rolling deformation,the PTT curves move toward the left lower direction. When the rolling deformation is larger than 0.2,the fastest precipitation temperature of vanadium is about 870 ℃,and the precipitation can be finished within 3 sec. Finally,the precipitation particles were observed under TEM.

Hot Ductility and Precipitation Analysis of 700 MPa Nb-Ti-bearing High Strength Steel Slab

Chen Yan, Jiang Zhongkuai, Lu Tan, Yang Xudong, Zhang Qi, Ni Feng

2015, 36(4): 36-42. doi: 10.7513/j.issn.1004-7638.2015.04.007

Abstract(29) PDF(1)

Abstract:
The influence of the addition of Nb and Ti on the hot ductility and the precipitation of continuous casting 700 MPa Nb-Ti-bearing high strength steel slabs was researched. Its high temperature mechanical properties were tested by Gleeble -3500. The morphology characteristics of fracture surface of the tensile specimen and the precipitation were observed and analyzed by scanning electron microscopy （SEM）and energy dispersive spectrometer （EDS）. Thermo-calc software was employed to calculate the species and starting temperature of precipitation during the solidification of the steel slabs. The brittle temperature zone Ⅲ of the 700 MPa Nb-Ti-bearing high strength steel slabs was observed to widen and extend to high temperature area （725~925 ℃） with the addition of Nb,according to the result of high-temperature tensile test. It was calculated that （Nb,Ti） carbonitride were precipitated during solidification of 700 MPa Nb-Ti-bearing high strength steel. Nb C-containing face-centered cubic phase was precipitated in large amount at about 1 100 ℃ which led to the rapid reduction of hot ductility of the slab. The hot ductility was further decreased due to the occurrence of phase transformation γ→ α at about 835 ℃. When eutectoid transformation was finished,the hot ductility of the slab was recovered. The parameters can be provided as reference for reducing crack in the 700 MPa Nb-Ti-bearing high strength steel slabs through this research.

Effect of Alloy Elements on the Microstructure and Electrochemical Performance of Vanadium-based Solid Solution Hydrogen Storage Alloy

Dong Yuzhen

2015, 36(4): 43-47. doi: 10.7513/j.issn.1004-7638.2015.04.008

Abstract(38) PDF(2)

Abstract:
The V₃TiNi_0.56 series vanadium-based solid solution hydrogen storage alloys were prepared with different contents of alloying elements of Sc or Y,and the microstructure,electrochemical corrosion resistance and charge-discharge cycling stability of the alloys were tested and analyzed. The results show that adding alloying elements of Sc or Y could improve the electrochemical corrosion resistance and charge-discharge cycling stability of the alloy. And the effect is better with the composite additives of Sc and Y than a single adding of Sc or Y. Compared with the V₃TiNi_0.56 alloy,the corrosion potential of the alloy with composite additives of Sc and Y is positively shifted by 193 mV,and attenuation rate of discharge capacity is decreased from 95% to 21% after 20 times of charge-discharge cycling.

Preliminary Studies on the Chloride Recycle from Residue of Fused Salt Chlorination and the Effect of Recycled Chloride on Hydrochloric Acid Leaching of Ilmenite

Zhang Jianbo, Wu Xuan, Miao Huijun, Zhou Li

2015, 36(4): 48-52. doi: 10.7513/j.issn.1004-7638.2015.04.009

Abstract(20) PDF(2)

Abstract:
This work preliminarily studied chloride recycle from residue of fused salt chlorination and the effect of recycled chloride on hydrochloric acid leaching of ilmenite. The results show that the soluble chloride and insoluble oxides in residue of fused salt chlorination can be effectively separated by water leaching. The insoluble residue of water leaching that mainly consists of stable oxides such as Fe₂O₃, （Fe,Mg）₂TiO₅, （Ca,Al,Mg） SiO₃,etc.,is only 11% of mass fraction. It is easy for stockpiling and harmless to the environment. The main chloride in residue of fused salt chlorination,KCl and Na Cl are enriched in the crystalline salts by evaporation of solution of water leaching,and the recovery rate of Cl element exceeds 95%. Adding the recycled chlorides into the system of hydrochloric acid leaching of ilmenite can improve the leaching reactivity. More recycled chlorides are added,synthetic rutile products with higher TiO₂ grade are obtained. The TiO₂ grade of synthetic rutile can increase from 80.8% to 84.5% by adding recycled chlorides with a mass ratio of 50%.

Study on the Application of Titanium Gypsum in Sintered Brick

Li Liang

2015, 36(4): 53-57. doi: 10.7513/j.issn.1004-7638.2015.04.010

Abstract(7) PDF(1)

Abstract:
Titanium gypsum is a by-product in producing titanium dioxide （TiO₂） by sulfuric acid method. 4~5 tons of titanium gypsum is produced for the production of every one ton of titanium dioxide. The environment pollution of the titanium gypsum can be efficiently resolved by adding the pretreated titanium gypsum to the sintered brick with gangue as main raw material. The influences of calcination temperature,addition amount of clay and titanium gypsum,and heat preservation time on the strength of the sintered brick were investigated by conditional and orthogonal tests. The results of conditional tests show that the strength of sintered brick increases with increase of calcination temperature,heat preservation time and the addition amount of clay,but it decreases with increase of addition amount of titanium gypsum. The results of orthogonal tests show that under a relatively stable addition amount of clay,the influence order of other factors on the strength of sintered brick is addition amount of titanium gypsum ＞heat preservation time ＞ calcination temperature. The optimum parameters are as follows: 14% of titanium gypsum addition,8 h of heat preservation and 1 000 ℃ of calcination.

Potential Benefits of Vanadium Microalloying in AHSS Cold Rolled and Annealed Strip

C. P. Scott, I. Pushkareva, D. Milbourn, R. Glodowski

2015, 36(4): 58-64. doi: 10.7513/j.issn.1004-7638.2015.04.011

Abstract(20) PDF(1)

Abstract:

The application of vanadium microalloying to advanced high strength steels （AHSS） is discussed. Some of thepotential benefits to a wide range of steel grades including dual phase （DP）,transformation induced plasticity （TRIP） and twinning induced plasticity （TWIP） are illustrated and examples are given. Attention is drawn to areasof research which merit further support from AHSS suppliers.

Split-thickness Layer of Vanadium-titanium Magnetite Ore Sintering Process

Bai Ruiguo, Li Yanjiang, Lü Qing, Ding Haichao, Sun Yanqin

2015, 36(4): 65-70. doi: 10.7513/j.issn.1004-7638.2015.04.012

Abstract(25) PDF(1)

Abstract:
Base on the characteristics of Cheng Steel vanadium titanium ore and actual production conditions,the shunt granulating sintering process under different material layer thickness conditions （conventional sintering,acid mixed sintered） had been investigated. Compared with conventional sinter （600mm）,when the material layer thickness is 1 000 mm,acid mixed sintering improves the sinter quality,especially RDI index. The resulting sinter by shunt granulating thicker layer of vanadium titanium ore features the typical structures of both high basicity sinter and acid pellets. On the other hand,the acid mixed sinter has a decreasing content of hematite,most of which independently existing in acidic ball.For the high basicity sinter existing in the resulting sinter microstructure,it has a higher content of magnetite and remarkable amount of binder phase acid calcium,while perovskite content decreases.

Effects of Pulsed Magnetic Field on Solidified Structure of Ti-bearing Low Carbon Steel

Zhang Qingjun, Mei Guohong, Zhu Liguang, Cui Zhimin, Yan Chunliang, Cao Shengli

2015, 36(4): 71-76. doi: 10.7513/j.issn.1004-7638.2015.04.013

Abstract(9) PDF(1)

Abstract:
The solidification process of Ti-bearing low carbon steel was controlled by self-developed pulsed magnetic field generator. With the help of metallographic microscope,scanning electron microscope and energy spectrum,the influence rules of the precipitation behavior of inclusions and solidification structure under different discharge voltages were studied. The refining effect with pulsed magnetic field under different solidification cooling rates was analyzed. The results showed that the inclusion size increases at first,then decreases with the increase of discharge voltages,while the number of intragranular ferrite gradually increases,and the grain size becomes smaller and more homogeneous. As the solidification cooling rate decreases,the action time of pulsed magnetic field on the solidification process of liquid steel is extended and the grain refinement effect is more obvious. When the discharge voltages is 80 V and the solidification cooling rate is 60 ℃ / min,the solidification microstructure is almost entirely comprised of fine and interlaced acicular ferrite.

Thermodynamics Study of High-phosphorus Hematite Gasification Dephosphorizing

Zhang Wei, Fu Junkai, Xing Hongwei, Tian Tielei, Wang Hui

2015, 36(4): 77-82. doi: 10.7513/j.issn.1004-7638.2015.04.014

Abstract(7) PDF(1)

Abstract:
The effects of different conditions on the equilibrium species about high-phosphorus hematite were investigated by Fact Sage6.4 thermodynamic analysis software. And some experiments were made to verify the thermodynamic analysis data. The results show that the existence forms of gas phosphorus were different at different temperatures,a rise of temperature enhances the phosphorus removal. The right amount of SiO₂ concentration can reduce the onset temperature of carbothermic reduction of fluorine calcium phosphate,when the SiO₂ concentration is high,the phosphorus removal were restricted by the produced silicate melts. When the C concentration is low,phosphorus is still contained in the fluorine calcium phosphate,when the C concentration is high,phosphorus is reduced to form FeP. Cl₂ can react with P₂ to produce PCl₃,when the temperature is low,the dephosphorizing product is PCl₃,when the temperature is high,the first dephosphorizing product is P₂,changes the dephosphorizing product to produce PCl₃ need higher concentration of Cl₂. Experimental verification was conducted by using simultaneous thermal analyzer,the experiment results are in good agreement with those of the thermodynamic analysis.

Experimental Investigation of Reduction and Melting-separation for Carbon-bearing Pellets

Li Rong, Guo Jiang

2015, 36(4): 83-87. doi: 10.7513/j.issn.1004-7638.2015.04.015

Abstract(8) PDF(1)

Abstract:
The reduction experiment was carried out on carbon-bearing pellets made of iron concentrate,pulverized coal and limestone. Morphology observation and separation degree of slag-metal had been analyzed. Based on these investigations an optimum experimental program for reduction and separation process was obtained as follows: temperature is 1 480 ℃,C/O is 1.2,reduction time is 22 min and binary basicity of slag R₂ is 1.0. The optimal experiment scheme resulted in the highest reduction degree and a good quality index of granular iron,and the iron yield reached up to 98.62%.

Research on Purity Control of Tube Bloom

Li Hongguang

2015, 36(4): 88-93. doi: 10.7513/j.issn.1004-7638.2015.04.016

Abstract(14) PDF(1)

Abstract:
In this paper thermodynamics analog calculation has been made for tube bloom in order to obtain a deoxidization technology and refining slag system. Industrial tests showed that if optical basicity and CaO /Al₂O₃ could be controlled at 0.75~0.80 and 2.0~2.5 respectively,then T[O]＜ 20 × 10^-6 in molten steel.T[O] decreases with increasing [Als] for bloom,where [Als] exceeds 0.015% then T[O] ＜ 20 × 10^-6,and[Als]＞0.020% then T[O]＜15 ×10^-6. The resulting technology can be effectively used to control the degree of purity. When T[O]≤2.0 × 10^-6,total content of non-metallic inclusion averages 21.6 ×10^-6 and all of the inclusion rating meet the requirements. For typical steel grades like B （PSL2） and JS25 Mn with stricter demand for [S]%,the average [S]have been controlled at 0.005% and 0.008% respectively.

Study on Devitrification Behavior of Continuous Casting Mold Flux

Zhu Liguang, Li Yaoguang, Wang Xingjuan

2015, 36(4): 94-100. doi: 10.7513/j.issn.1004-7638.2015.04.017

Abstract(18) PDF(1)

Abstract:
In order to investigate devitrification behavior of continuous casting mold flux in the process of annealing,glassy flux was annealed by single hot thermocouple technique,and then observed by scanning electron microscope and XRD. It is found out that the devitrified phenomenon occurred from the glassy flux during annealing and the main crystal phase is cuspidine. Temperature of devitrification increases with increasing annealing rate. When treating temperature is increased,degree of crystallization increases first then decreases. Increasing the steady temperature causes the shorter incubation time. With treating temperature of glassy flux film increase,the roughness on the surface of flux film increases,and the number of void increases.

Thermodynamic Simulation on Viscosity of CaO-MgO-SiO₂-Al₂O₃ Quaternary Refining Slag System

Zhao Lina, Tang Guozhang, Li Junguo, Feng Shuai

2015, 36(4): 101-107. doi: 10.7513/j.issn.1004-7638.2015.04.018

Abstract(46) PDF(5)

Abstract:
On basis of the quaternary slag system used for bearing steel refining,the influence of basicity,Al₂O₃ and MgO content on the viscosity of CaO-MgO-Al₂O₃-SiO₂ slag system has been investigated by Fact Sage software,and the calculation was compared with the measured value for actual system,for the purpose of providing theoretical basis for optimization of the refining slag system components. Viscosity of the slag system could be simulated with the thermodynamic software. There was a tendency that viscosity declined to the minimum and then increased with increase of the basicity. When the basicity is low,the addition of basic oxides accelerates disintegration of silicate minerals,then the amount of α-C₂S crystallization and the viscosity of the slag decline dramatically. When the basicity is high,the amount of two kinds of solid solution,in which the main component is CaO and MgO,respectively,increases gradually and then the viscosity increases,suggesting that viscosity of the slag system declines with Al₂O₃ content increasing. When the content of Al₂O₃ is low,the amount of α-C₂S and the solid solution crystallization decline with the increase of Al₂O₃ content,and the viscosity declines quickly. At the high Al₂O₃ level,the amount of solid phase is low,change of Al₂O₃ content has weak influence on the viscosity. When the temperature of slag system is low,the viscosity has been impacted by the modification of MgO on net structure of the molten slag and the crystallization of solid phase. There is a tendency that the viscosity declines to the minimum and then increases with the increase of MgO content. When the temperature of the slag system is high,the viscosity is controlled by the amount of solid solution crystallization and increases with the increase of MgO content.

Research on Behaviour of Large Inclusions in IF Steel

Gao Ju, Liu Wenhui, Xing Wei, Ma Lixing, Chen Yonghong

2015, 36(4): 108-113. doi: 10.7513/j.issn.1004-7638.2015.04.019

Abstract(21) PDF(1)

Abstract:
In this paper,comprehensive analysis had been carried on the macro inclusion with regard to the type,source,composition and quantity and the main factors influencing the cleanliness of casting slab had been identified. Composition analysis shows that the [O] and [N] contents of the first slab are 82.5 ×10^-6and 61.5 × 10^-6,respectively,both are significant higher than these of other slabs; and the inclusions are mainly divided into three categories: block and cluster of Al₂O₃,compound Al₂O₃·TiOx and CaO（SiO₂） ·Al₂O₃·Ti inclusions,which come from re-oxidation products,slag entrapment in mould or tundish,and stuffing sand. First slab has the highest content of macro inclusions with average value of 3.287 mg / kg,followed by the last slab （2.739 mg / kg） and the mixed casting slab （1.557 mg / kg）,while the content of macro inclusions of the normal slab is 1.227 mg / kg. the distribution of macro inclusions is non-homogeneous along thickness direction of slab,where contents of inner arc slab are obviously higher than those of outer arc slab. Macro inclusions comprise of small particle with size of 140~300 μm and large particle bigger than 300μm in first slab,which account for 38.3% and 61.7% of total inclusions,respectively.

Experimental Studies on Corrosion Behaviour of Ferritic Stainless Steel in HCl Based Solution

Xie Qiong, Shi Peiyang, Liu Chengjun, Jiang Maofa

2015, 36(4): 114-118. doi: 10.7513/j.issn.1004-7638.2015.04.020

Abstract(15) PDF(1)

Abstract:
The effect of potassium chlorate （KClO₃） as oxidants on pickling behaviour in HCl-based electrolyte and the surface quality of original hot-rolled and blasted 430 stainless steel （430-SS） were studied,by means of weight-loss tests,microstructure analyses,potentiodynamic polarization curves and electrochemical impedance spectroscopy measurements. The results showed significantly accelerated pickling process for 430-SS happened by adding KClO₃ through enhanced cathodic reaction rate and reduced Rt,with pitting corrosion when excess KClO₃ was added. KClO₃ is a proper oxidant for pickling in HCl-based electrolyte of 430-SS,with reasonable addition of 1%.

Texture Evolution of High Grade Non-oriented Silicon Steel Produced by 20 mm Thin Slab

Xue Yanchun, Ma Liang

2015, 36(4): 119-123. doi: 10.7513/j.issn.1004-7638.2015.04.021

Abstract(10) PDF(1)

Abstract:
In this paper texture evolution of high grade non-oriented silicon steel produced by 20 mm thin slab in the course of hot rolling,normalizing,cold rolling and annealing process was investigated. The texture of samples was measured by EBSD. The results show that the texture intensity through thickness of hot rolled strip change obviously,Goss texture has highest intensity in the S = 0.9 layer,and Quite strong{221} ＜227＞ dominates in the S = 0.5 layer,while rotate cube texture takes a leading role in the S =0 layer. In the surface and center layer of the cold normalized strip,the main texture is {223} ＜110＞,while the main texture in the S = 0.5 layer is {332} ＜113＞. In the each layer of the cold rolled sheet,the {001} ＜110＞-{223} ＜110＞ has strong intensity. The annealed sheet has a strong {001} ＜130＞ texture while a certain amount of γ-fiber texture occurs in the surface layer.

Process Practice of Desulfurization in Silicon Steel Produced by the KR-BOF-RH-CC

Zhang Zouhua, Lü Jiping, Guan Pingping, Wang Yuan

2015, 36(4): 124-127. doi: 10.7513/j.issn.1004-7638.2015.04.022

Abstract(6) PDF(1)

Abstract:
The desulfurization of silicon steel in the course of KR-BOF-RH-CC process were analyzed by industrial practice verification and statistics. The results show that the resulfurization quantity of hot metal is lower when the rate of slag skimming increases above 98%. The combing measure of using high quality scrap steel,and free of iron piece addition,and 15 kg/t of cold-bound pellets ratio can guarantee the end [S] content of BOF less than 0.006%. The ability of desulfurization is weak in RH,the rate of RH desulfurization depends on the desulfurizer consumption and the [O] content before alloying. The [O] content should be controlled at less than 450 × 10^-6 in the liquid steel. By increasing the rate of slag skimming,controlling sulfur source and the [O] content of molten steel,the unqualified rate of silicon steel due to [S] dropps by 75% and the desulfurizer consumption will decrease by 17.72%.

Microstructure Characteristics and Phase Transformation of Specularite during Microwave Magnetic Roasting Process

Ma Hao, Chen Tiejun, Yuan Yizhong

2015, 36(4): 128-133. doi: 10.7513/j.issn.1004-7638.2015.04.023

Abstract(9) PDF(1)

Abstract:
Through microwave magnetizing roasting the Jiugang’s specularite in the high temperature microwave reactor,the heating characteristic of specularite under microwave treatment,phase transformation before and after magnetic roasting and the effect of microwave heating on the microstructure were investigated. It was shown that the mineral absorbed microwave power effectively and could be heated up to more than 500 ℃ in 15 minutes by microwave heating. SEM analysis indicated that intergranular fractures occurred both in the conventional heated sample and microwave heated sample,but the form of crack was different. The crack in the sample by conventional magnetizing roasted was mainly caused by siderite decomposition,but the crack in the sample by microwave heated widely distributed in the siderite and also the specularite and the interface between specularite and gangues. These crack are expected being caused by excess internal stress due to the selective microwave heating result.

Preparation of Low-carbon Ferrochromium from Chromite Fines by Microwave Silicothermic Reduction

Li Lei, Zhu Hongbo, Peng Jinhui, Zhang Libo, Dai Linqing, Wu Kuilin

2015, 36(4): 134-139. doi: 10.7513/j.issn.1004-7638.2015.04.024

Abstract(13) PDF(1)

Abstract:
To achieve chromite fines resources utilization effectively,the new process of preparation of low-carbon ferrochromium from chromite fines by microwave silicothermic reduction was investigated.FactSage software was used to simulate the ternary slag （SiO₂-CaO-Cr₂O₃） and the binary slag （SiO₂-CaO）,in order to generate the optimum technological conditions in combination with experimental data.The results show that with combining parameters of final temperature at 1 450 ℃ and binary basicity of 1.64,ferrochrome and slag can be entirely separated during the reaction and the recovery of chromium reach to 81.03%. XRD and XRF analysis on the phase and chemical composition of the products indicate that ferrochrome does not contain the slag and its chemical composition meet the standard of FeCr55C25 Ⅱ. SEM observation and EDX analysis show that crystalline grain contains tiny amounts of Si and C mainly distribute in the grain boundary.

Experiment Study of Partical Residence Time Distribution in Fluidized Bed with Vertical Partition Plate

Peng Yingbin, Li Haiguang, Gong Zhijun, Wu Wenfei

2015, 36(4): 140-144. doi: 10.7513/j.issn.1004-7638.2015.04.025

Abstract(6) PDF(2)

Abstract:
According to magnetization reduction roasting of limonite in a fluidized bed,a vertical partition plate is installed in fluidized bed to improve particle behavior,reduce dead region and short circuit condition and average RTD. In this paper the impact of superficial gas velocity,feed rate,particle size on particle RTD in fluidized bed with vertical partition plate have been investigated by pulse method. Results showed that with increasing superficial gas velocity and feed rate,RTD concentrated,while increasing particle size led to a scattered RTD. Experiment data can provide beneficial references to this type of fluidized bed in reduction of limonite.

2015, 36(4): 145-146.

Abstract(20) PDF(1)

Abstract:

2015 Vol. 36, No. 4