钢铁钒钛

A New Process for Vanadium Extraction from Molten Vanadium Slag by Direct Oxidation and Sodium Activating Method

Song Wenchen, Li Hong

2012, 33(6): 1-5.

Abstract(40) PDF(1)

Abstract:
To address the problem of heat waste of vanadium slag in the existing vanadium extraction process,a new process is proposed in this paper to extract vanadium from molten vanadium slag by direct oxidation and sodium activating method.On the basis of current vanadium extraction process,the new process was verified by thermodynamic and kinetic calculation and analysis,and then simulation tests were carried out in the laboratory.The results show that with enough heat,vanadium slag can be kept in molten state during the vanadium extraction process.The dynamic conditions of the new process are noticeably better than the existing process.The oxidization rate of vanadium slag is about 90% and vanadium leaching rate can reach 82% or above with enough oxygen and Na₂CO₃ content at 20% ~30% of vanadium slag’ weight.Thus,the feasibility of the new process is confirmed by the results.

Effect of Carbon Ratio on Vacuum Carbon Thermal Reduction of TiO₂

Zhou Yuchang

2012, 33(6): 6-10.

Abstract(70) PDF(1)

Abstract:
By using titanium dioxide and graphite as raw material,TiO₂/C vacuum carbon thermal reduction experiments were carried out to investigate the effect of carbon ratio on the TiO₂/C vacuum carbothermic reaction process and the reduction product.The experimental results indicates that the reduction process exhibits a characteristic of staged reduction and the extent of reaction at each stage depends on carbon ratio;apparent differences of the reduction products obtained at different carbon ratio lie in free carbon contents and their existing state;with the increase of carbon ratio,particle size of the reduction products decreases and porosity of the product increases;resistivity of the reduction products ranges from 2.61×10^-3 Ω·cm to 4.20×10^-3 Ω·cm with conductivity varying between conductor and semiconductor.

Experimental Study on Two- step Synthesis of Vanadium- aluminium Alloy

Chen Haijun

2012, 33(6): 11-15.

Abstract(80) PDF(5)

Abstract:
Main factors affecting vanadium-aluminum alloy smelting by two-step process were studied,and the products were analyzed through metallographic inspection.The results show that vanadium yield and apparent quality of the products can be noticeably improved by applying appropriate unit burden heat and superheat degree during tapping in the process of vacuum refining.It is found that the appropriate unit burden heat for aluminum heat smelting process is 3 250 kJ/kg,and the best degree of superheat for vacuum refining is 30 ℃.All the chemical compositions of the vanadium-aluminium alloy so obtained can meet the standards of GfE.

Effect of Ti on the Microstructure and Thermal Fatigue Property of ZA27 Alloy

Dong Xingsheng, Si Naichao, Si Songhai, Zhang Zhijian, Liu Rong

2012, 33(6): 16-21.

Abstract(36) PDF(1)

Abstract:
The effect of Ti modification on microstructure and thermal fatigue property of ZA27 alloy is discussed in this paper.The samples’ microstructure and morphologies of cracks caused by thermal fatigue are examined by optica1 microscopy（OM） and scanning electron microscopy（SEM）,and mechanism of Ti modification and thermal fatigue damage are analyzed.The results show that after Ti modification,the grains are obviously refined and primary α-A1 phases are found to vary from thick dendrite to fine petal-shaped dendrite.The plasticity and toughness of ZA27 are significantly increased,which results in the improvement of the thermal fatigue property.With a Ti addition at 0.3%,ZA27 exhibits the best thermal fatigue property.

Research on In- situ Synthesis of （V,Nb） C Reinforced Iron Matrix Composite and Its Microstructure

Xian Yong, Wang Yisan, Ding Yichao, Wang Jing

2012, 33(6): 22-25,30.

Abstract(63) PDF(2)

Abstract:
In-situ synthesized（V,Nb）C reinforced iron matrix composites with sintering density of 7.07 g·cm-3 at 1 360 ℃were prepared by powder metallurgy process.The microstructure of the composites were investigated by X-ray diffraction（XRD）and scanning electron microscope（SEM）respectively.The results show that NbC absorbs on the surface of VC particles during high temperature precipitation process and then（V,Nb） C solid solution that could inhibit the growth of hard-phase particles is formed by inward penetration of NbC.When the molar ratio of Nb/V was 0.4,Nb could effectively inhibit solid solution of alloy elements in carbides,bringing a large number of V,Mo and Cr into austenite,and thus the iron matrix comprising of bainite and residual austenite was obtained with furnace cooling.

Preparation of MnO_x-MoO₃ /TiO₂-Al₂O₃ Catalyst and Its SCR Denitration Performance

Liu Renlong, Xie Yinyin, Wu Xuhong, Liu Changkang, Du Jun, Tao Changyuan

2012, 33(6): 26-30.

Abstract(67) PDF(1)

Abstract:
MnO_x-MoO₃/TiO₂-Al₂O₃（MMTA） catalysts with various loads of Mn and Mo were prepared by dipping method,and its catalytic activity was studied in the selective catalytic reduction of NO with NH₃（NH₃-SCR）.The effects of temperature and different carrier on the SCR reaction were evaluated in the fixed bed continuous reactor.The catalyst was characterized by X-ray diffraction（XRD）,scanning electron microscope（SEM） and BET to observe its crystal phase and micro-morphology.The results indicate that,compared to the catalysts supported by TiO₂（T）,the catalysts supported by TiO₂-Al₂O₃（TA） have larger specific surface area and pore volume,which are favorable to decentralize active component MnO_x.Meanwhile,MnO_x-MoO₃/TiO₂-Al₂O₃（MMTA） catalysts exhibit good catalytic activity and excellent stability at high temperature.The NO_x conversion ranges from 75% to 95% at 150 ℃ to 450 ℃ and airspeed of 10 000 h^-1.Thus,the emissions of nitrogen oxides can be controlled effectively.The products show great application potential.

The Novel Technology of Two-step Roasting Desulfurization for Sulfur-bearing Slag

Cui Yuyuan, Wang Deyong, Liu Chengjun, Jiang Maofa

2012, 33(6): 31-34.

Abstract(64) PDF(1)

Abstract:
The existence of sulfur in steel slag restrains its recycle and re-use in steelmaking process.To recycle the waste slag as much as possible,a novel approach of two-step roasting desulfurization has been proposed in this present study.The thermodynamic analysis shows that CaO stable region in Ca-S-O system increases with increasing of reaction temperature and decreasing of oxygen partial pressure in atmosphere.So,the roasting process should be controlled at a high temperature and a low oxygen pressure.The optimized parameters of two-step roasting are also obtained.In the first stage,CaS is roasted under the air atmosphere at 900 ℃ for 180 min,then the intermediate is reacted under argon gas at 1 100 ℃ for 40 min.After treatment of two-step roasting,the sulfur content in the actual waste slag was decreased from 0.8% to 0.23%.The products can be recycled to the steelmaking process.

New Treatment Process for Three Wastes Generated from Chloride TiO₂ Pigment Production

Sun Hongtao

2012, 33(6): 35-39.

Abstract(48) PDF(2)

Abstract:
In view of shortcomings in conventional ’three wastes’ treatment method,a new process is developed to deal with the wastes generated from chloride TiO₂ pigment production.In the process,waste slag from chlorination can be slurried with acid waste water produced from washing off-gas,and then it can be recycled after filter pressing,neutralization and sedimentation,and refiltering.The liquid waste generated from filtration can be directly evaporated and concentrated with high temperature flue gas from burning off-gas containing high CO,and a co-product of calcium chloride dihydrate can be obtained at the same time by desulfurizing the off-gas.The process not only solves the problem that SO₂ concentration in the off-gas exceeds standard,but also creates economic benefits for enterprises through comprehensive treatment.The practical production shows that with this process,waste dust and waste water emissions are greatly reduced compared with the traditional process,and CO,SO₂ and COS difficult to deal with in the off-gas are successfully eliminated or recycled.About 100 kg of raw materials can be recycled and about 250 kg of by-product calcium chloride can be produced per ton TiO₂ product.

Study on Metallurgical Effects of M- EMS during Bloom Continuous Casting

Li Zhiqiang

2012, 33(6): 40-44.

Abstract(57) PDF(1)

Abstract:
In this paper,M-EMS magnetic field intensity and bloom quality at different periods is counted,and on this basis,the effect of magnetic field intensity of M-EMS on casting bloom quality is analyzed.Different magnetic field intensity in a single strand can be obtained by changing the current intensity of M-EMS.Then,the corresponding bloom under different magnetic field intensity are sampled for testing.Thus,the effect of magnetic field intensity on bloom quality is studied in a single strand.Analysis suggests that M-EMS should not be used when its magnetic field intensity is less than 300×10-4 T.Furthermore,the metallurgical effects of bloom M-EMS in Pangang are evaluated and the applicable standard for M-EMS is established.

Characteristics of the Shell with Sticking Breakout Problem and Temperature Variation of the Mold’s Thermocouple in Slab Casting

Pei Hongbin, Zhang Hui, Xi Changsuo, Wu Yeming, Shi Zhe

2012, 33(6): 45-48,62.

Abstract(88) PDF(1)

Abstract:
In order to study the formation mechanism of sticking breakout in slab and prevent its occurrence,main characteristics such as thickness,crack and oscillation mark of the solidified shell are analyzed.A mathematical model simulating the acting force on primary solidified shell is developed.Based on the measured mold temperature data in slab continuous casting,characteristics of temperature variation in the mold under normal and abnormal conditions are analyzed.Typical characteristics of the shell with sticking breakout problem are summarized,and the factors leading to this type of breakout are discussed,such as the properties of protecting slag,casting speed and oscillation parameter.Temperature variation characteristics of the thermocouple in the sticking process are concluded and the results can provide guidance for the sticking breakout prediction.

Formation Mechanism of the Meniscus Solidified Hook in the Continuous Casting Mold

Cao Chunlei, Zhou Li

2012, 33(6): 49-52.

Abstract(87) PDF(1)

Abstract:
A solidified hook was found by observing the macrostructure of a leaked strand.The general formation theory of solidified hook is revised in this paper.It is pointed out that during vibration of the mold,the existence of the negative slip results in variation in temperature in the solidified front and pressure in the molten slag channel which constitutes the main reason for formation of the solidified hook.The varying pattern of the pressure in the protecting slag channel of the casting mold is analyzed,through which the validity of the revised theory can be proved.It can be concluded that by adjusting steel temperature,smoothening the running condition of the mold and choosing reasonable protecting slag,the formation of solidified hook can be avoided.

Influence of La₂O₃ on Physical Properties of B₂O₃-containing Fluoride- free Casting Powder

Li Rong, Guo Jiang, Zhang Fang

2012, 33(6): 53-57.

Abstract(54) PDF(1)

Abstract:
In order to solve the problem that B₂O₃-containing fluoride-free casting powder tends to refrain the formation of crystals,crystallization properties of the fluoride-free mold casting powder and heat transfer of slag film were investigated with the basicity（CaO/SiO₂） of casting powder at 0.9,compositions of 27% ~36.47% w_CaO,30% ~40.5% w_SiO₂,4% w_Al₂O₃,5% w_MgO,8% w_Na₂O,2% w_Li₂O and 4% w_B₂O₃ and the increase of w_La₂O₃ from 0 to 20%.The research shows that La₂O₃ can increase the thickness,crystallization ratio and crystallization temperature of slag film and reduce the melting temperature of the molten slag,thus effectively improveing heat transfer performance of the mold.

Study on Morphology and Size Distribution of Sulfide Inclusions in Free Cutting Steel AISI 1215

He Yingying, Zhou Cheng, Li Hongyou, Ma Han

2012, 33(6): 58-62.

Abstract(42) PDF(1)

Abstract:
The morphology and size distribution of MnS inclusions in AISI 1215 free cutting steel billet were studied.The results show that the sulfides evolve from type I to type II with the position moving from edge to center at the cross section.Based on Uhlmann model and chemical compositions of the billet,it is suggested that cooling rate and sulfur segregation play an important role in controlling the morphology and diameter of MnS inclusions.The increasing cooling rate facilitates the formation of type I MnS,but is unfavorable to the growth of MnS.Sulfur segregation contributes to the formation of type II MnS.

Numerical Simulation of Fluid Flow and Thermal Characteristics in the Funnel-type Mold with Different Width

Xu Mianguang, Liu Heping, Chen Yuanqing

2012, 33(6): 63-68.

Abstract(42) PDF(1)

Abstract:
The width of the thin slab mold can be changed to produce different steel grades to satisfy the needs of customers.Therefore,it is necessary to study the fluid flow,heat transfer and solidification behavior in the mold.In this paper,the coupled model was adopted to analyze the fluid flow,heat transfer and solidification behavior of different width,1 100,1 300 mm,and 1 600 mm in the funnel-type mold.The casting speed was at 4.0 m/min.The results showed that the free surface condition compared to the conventional slab show some differences as the width of the mold increases.The width change mainly reflected the impact of heat transfer and solidification of the local area in the direction along the outlet jet,the weak areas of the mold exit of the solidified shell with a width increase in expansion.

Research on Precipitation of Inclusions in Calcium- treated Sulfur- containing 20CrMo Gear Steel

Guo Dengyang, Wu Xiaodong, Chen Ruilong, Tan Shengkang

2012, 33(6): 69-73.

Abstract(53) PDF(1)

Abstract:
In order to meet the rating requirement for inclusions in the steel,the additive amount of calcium to the steel was controlled through thermodynamic calculation,and after calcium treatment,Al₂O₃ was modified to low-melting-point 12CaO·7 Al₂O₃ which could be removed from 20CrMo steel.Thermo-Calc software was used to simulate the precipitation process of calcium aluminates including CA6,CA,and CA2 and MnS inclusions during the solidification of liquid steel.SEM was employed to analyze the spindle-shaped inclusions.It was found that a small amount of inclusions had dark-colored core consisting of Al₂O₃ and CaS etc,and light-colored outer layer consisting of MnS inclusion.It indicates that in the solidification process of liquid steel,composite inclusions precipitated earlier such as Al₂O₃ and CaS can be captured by MnS precipitated later as its core.

Experimental Study on Two-dimensional and Three-dimensional Morphology Differences of Non-metallic inclusions in Aluminum Killed Steel

Tian Yonghua, Bao Yanping, Wang Min, Ruan Wenkang

2012, 33(6): 74-79.

Abstract(52) PDF(1)

Abstract:
By taking non-metallic inclusions in aluminum killed steel as object of study,the advantages and disadvantages of metallography method and extraction method are comparatively used to observe the differences of the inclusions’two-dimensional and three-dimensional morphologies.As inclusions in the steel are extracted by organic solution（methanol as major dissolvent）,three-dimensional characteristics of clustering Al₂O₃ can be observed clearly.Compared with traditional metallography method,extraction method can extract the entire inclusions and perfectly observe the three-dimensional morphology,structure and external composition of the inclusions,which are valuable for effectively controlling inclusion morphologies and compositions and removing harmful inclusions.However,inner morphologies of inclusions can’t be observed by this method.On the contrary,by the metallography method,certain crosssections of inclusions can be observed with SEM,which is important for concluding the formation and transformation processes of inclusions.To sum up,reasonable integration of the two methods helps to obtain more detailed information about inclusions in steel,which can provide theoretical principles for controlling inclusions more effectively.

Research on Influence of Rare Earth on ICDP Roll Structure and Thermal Fatigue Resistance

Wang Weiguo, Li Zhonghua

2012, 33(6): 80-85.

Abstract(58) PDF(1)

Abstract:
Liquid iron was modified by adding rare earth at later stage of melting,and metallographic and thermal fatigue tests were carried out to investigate the effects of different contents of rare earth on structures and thermal fatigue performance of rolls.The test shows that when the content of rare earth is not more than 0.1%,the morphology and distribution of carbide and graphite in the matrix structure can be effectively controlled,thereby thermal fatigue behavior of the rolls can be improved.However,when the rare earth content is more than 0.1%,there is little change in the morphology and distribution of carbide while graphite grows larger,which leads to unfavorable thermal fatigue behavior of rolls.

Thermodynamics Analysis on the Precipitation of Titanium Nitride in a Welding Wire Steel

Chen Tao, Li Hong, Lü Naibing, Tang Guozhi, Wang Lifeng, Wu Keng

2012, 33(6): 86-90.

Abstract(68) PDF(3)

Abstract:
As a kind of main non-metallic inclusions of ER50-G for welding wire,TiN has an obvious influence on the property of ER50-G.The sample with a Ti content of 0.16% obtained from the production process of ER50-G is examined by FE-SEM.Based on the chemical composition of the wire rod,the critical temperature for precipitation of TiN is calculated to be 1 822.6 K,which is above the liquidus of ER50-G.TiN precipitates in both liquid and solid phases,but mainly in liquid phase.It can be concluded that in the production of ER50-G,the precipitation amount of TiN particle in liquid steel is higher than theoretical value while lower in solid phase.Finally a practical curve of TiN precipitation is obtained.

Analysis and Countermeasures of Bulging Defect at the Edge of Cold-rolled Products

Dou Zhiyong, Huang Bin, Feng Shaoqiang

2012, 33(6): 91-94.

Abstract(45) PDF(2)

Abstract:
Bulging defects at the edge of strip steel forming during cold rolling process and corresponding measuring data are analyzed.It is concluded that local high spots at hot rolled strip steel are the major causes of the defects.In addition,convexity and wedge of the hot rolled plates and rolling length have certain influence on the formation of defects.Causes of local high spots are analyzed in the aspects of microstructure and rolling stress,and finally the bulging defects are noticeably reduced through process improvement.

Precipitation Behavior and Texture Formation at Different Stages of Processing in Ti-IF

Feng Yanqing, Wang Fuming

2012, 33(6): 95-98.

Abstract(49) PDF(1)

Abstract:
The precipitation behavior and texture formation during hot rolling,cold rolling and annealing（at 700 ℃ and 800 ℃） have been studied in a Ti-containing interstitial freesteel.The presence of FeTiP in the 700 ℃ annealed steel and its absence in the 800 ℃ annealed material are considered to be responsible for the poor {111} texture and low r in the former and strong {111} texture and high r in the latter.Annealing at 700 ℃ produces copious FeTiP type precipitates,while after annealing at 800 ℃ Ti₄C₂S₂ precipitates form.Due to the formation of Ti₄C₂S₂,C is easily taken out of the solid solution during recrystallization annealing and this results in better {111} texture formation and thus better formability in the 800 ℃ annealed material.

Study on The Method for The Determination of Vanadium in V- Al Alloy

Zheng Xiaomin, Yang Ping, Dan Juan, Wu Jianguo, Luo Yunchuan

2012, 33(6): 99-102.

Abstract(54) PDF(2)

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In this paper,the ammonium ferrous sulfate titrimetric method for the determination of vanadium in V-Al alloy has been established,which used HCl+HNO₃ to decompose the sample,used ammonium persulfate oxidate the vanadium to pentavalent in the 6~7 mol/L sulfuric acid.The determination conditions,such as sample quantity,concentration of ammonium ferrous sulfate standard solution,sulfuric acidity,ammonium persulfate solution dosage,were selected and optimized to determine the best experimental conditions.The method was used to measure the content of Vanadium in the V-Al alloy,and the determination of relative standard deviation（RSD,n = 8）＜0.2%.The recoveries was 99.8%~100.7%,which fully meet the analysis and quick analysis requirement.

2012, 33(6): 103-105.

Abstract(30) PDF(1)

Abstract:

2012 Vol. 33, No. 6