钢铁钒钛

Effects of Calcination Time on Rutile Pigment Production via Short Sulfate Process

Tian Congxue

2015, 36(6): 1-5. doi: 10.7513/j.issn.1004-7638.2015.06.001

Abstract(62) PDF(3)

Abstract:
Short sulfate process was adopted to produce rutile titanium dioxide pigment by using unenriched industrial TiOSO₄ solution as raw material. The effects of calcination time at high temperature on the crystal structure,particle size distribution and pigment performances of rutile pigment were investigated. The calcined samples were characterized by TG-DSC,XRD,particle size distribution test and pigment properties test. The rutile crystal grain size and rutile content for the pigment gradually increased as the calcination time was prolonged,with a positive linear correlation. Nevertheless,the blue phase index is negative linear correlation with calcination time. The optimized calcination time at high temperature for the production of rutile pigment is of 40 min at 850 ℃,and the as-prepared rutile pigment is with grain size of 170.8 nm,rutile content of 98.2%,suitable and narrow particle size distribution,and the optimal pigment performances.

Research on Reduction of Pre-oxidized Titanium Slag

Lu Hui, Xie Hongyan, Meng Jun, An Jianguo, Xie Gang

2015, 36(6): 6-12,17. doi: 10.7513/j.issn.1004-7638.2015.06.002

Abstract(60) PDF(5)

Abstract:
A new method of deep-reduction and high pressure acid leaching was introduced to prepare rich titanium material with the pre-oxidized titanium slag from Yunnan as raw material,and the effects of atmosphere,temperature,time and cooling system on the reduction were discussed. The results show that with 700 L/h of air flow rate,1 000 ℃ of temperature for 2.5h and 5 ℃/h of cooling rate for the reduction of pre-oxidized titanium slag,a relatively higher reduction rate of iron oxides can be obtained and the slag phase is partially damaged,with significantly high leaching rate of impurities satisfying requirements of rich titanium material for titanium dioxide production by chlorination process.

Study on Kinetics of Ammonium Polyvanadate Re-dissolution

Yin Danfeng, Sun Zhaohui, Jing Han, Du Guangchao, Chen Haijun

2015, 36(6): 13-17. doi: 10.7513/j.issn.1004-7638.2015.06.003

Abstract(88) PDF(2)

Abstract:
Ammonium polyvanadate re-dissolution is an important process for industrial production of high purity vanadium pentoxide. The pH calibration method was employed to measure the re-dissolution rate of ammonium polyvanadate. The re-dissolution kinetics of ammonium polyvanadate was studied under production process conditions of NaOH concentration 0.5 mol/L and liquid-solid ratio 20:1. According to the kinetics experiments and calculations,the re-dissolution rate of ammonium polyvanadate was found to increase with increasing temperature and agitation speed. The kinetic model for re-dissolution of ammonium polyvanadate is unsteady-state diffusion of liquid film,with unsteady-state diffusion of liquid film as the control step and 6.15 kJ/mol of the calculated activation energy. Proper increase in agitation speed and redissolution temperature can enhance the diffusion rate for re-dissolution of ammonium polyvanadate.

Research on Removal of Calcium in Metatitanic Acid

Wang Haibo, Wang Bin

2015, 36(6): 18-22. doi: 10.7513/j.issn.1004-7638.2015.06.004

Abstract(57) PDF(3)

Abstract:
In order to remove calcium sulfate in metatitanic acid produced by sulfate process,the changes in solubility of calcium sulfate in solutions containing 1% sulfate acid with addition of different cosolvents were investigated by isothermal equilibrium method,and then the removal of calcium for metatitanic acid was carried out using the better cosolvents under optimum conditions. The results show that the sequence of dissolving-aiding effect is ammonium citrate > sodium chloride > mixture of magnesium chloride and sodium chloride > magnesium chloride,and the optimum conditions for ammonium citrate and sodium chloride are 55 ℃ of temperature,10% of mass concentration and 0.5 h of dissolution time,respectively with 7.63 g/L and 9.84 g/L of solubility for calcium sulfate. Sodium chloride has a better efficiency for calcium removal than ammonium citrate and does not affect the quality of final product. The research has important realistic meanings for decreasing the calcium content in titanium dioxide and improving the quality of final product.

Influence of Impurity Ions in the Electrolyte on Vanadium Battery Performance

Chen Fuyu, Gu Shiyan, Sun Qing, Chen Hui, Liu Qingyu

2015, 36(6): 23-27,31. doi: 10.7513/j.issn.1004-7638.2015.06.005

Abstract(164) PDF(6)

Abstract:
Study on the influence of impurity ions in electrolyte is critical for optimizing and improving the performance of vanadium battery. Considering electrolyte materials and operation of vanadium battery,two typical ions,SiO₃^2- and Fe²⁺,were selected as the research object. The influences of SiO₃^2- and Fe²⁺ on electrochemical activity of graphite electrode and coulombic efficiency,voltage efficiency,energy efficiency and capacity attenuation of battery were investigated by cyclic voltammetry and charge-discharge test,aiming to provide theory basis for the impurity ions control in electrolyte. The results suggest that Fe²⁺ does not affect the reaction activities of the electrodes and battery efficiency,and the capacity of battery is improved by adding Fe²⁺. Nevertheless,SiO₃^2- reduces the reaction activity,voltage and energy efficiency of the electrodes and accelerates the rate of capacity attenuation of battery. Thus,SiO₃^2- should be avoided during the manufacture and use of vanadium electrolyte.

Effect of Calcination Temperature on Pigment Properties and Particle Size of Anatase Titanium Dioxide

Luo Zhiqiang

2015, 36(6): 28-31. doi: 10.7513/j.issn.1004-7638.2015.06.006

Abstract(62) PDF(4)

Abstract:
The effect of calcination temperature on the achromic ability,whiteness,morphology and particle size of anatase titanium dioxide were studied in this paper,and the calcinated samples were characterized by Raman spectra,pigments properties test and SEM. The results show that with calcination temperature increasing from 915 ℃ to 970 ℃,the achromic ability of the sample gradually increases while its blue phase gradually decreases. The particles of titanium dioxide sinters under higher temperatures and the average particle size increases to 310 nm,with heterogeneous particle size distribution. The optimum calcination temperature is determined to be 935~945 ℃,under which the titanium dioxide owning narrow size distribution can be obtained with 260 nm of particle size,more than 1 500 of achromic ability and more than 4.0 of blue phase.

Effect of Vanadium on the Microstructure and Properties of Magnesium Alloy for Electronics and Electrics

Zhu Shunlan, Huang Hui, Deng Hao

2015, 36(6): 32-36. doi: 10.7513/j.issn.1004-7638.2015.06.007

Abstract(80) PDF(2)

Abstract:
A new type of magnesium alloy containing vanadium was prepared with the vanadium powder effectively added into the cast AZ81 parent magnesium alloy by friction stir processing,and the microstructure,phase composition,micro-texture and mechanical properties of the alloy were tested and analyzed. The results show that the new-typed alloy is with tiny grain and composed of α-Mg matrix and a small quantity of the Mg₁₇Al₁₂ and Al3V phase. Compared with the parent magnesium alloy,the internal microstructure of the new-typed magnesium alloy containing vanadium is obviously weakened with significantly improved mechanical properties. The maximum of texture of the new-typed magnesium alloy is decreased by 30%,and the tensile strength,yield strength and elongation after fracture of the alloy can be increased by 27%,60% and 82%,respectively. Moreover,the fracture mode of the new-typed alloy changes from mixed fracture to ductile fracture.

Dynamic Precipitation Behavior of V-N Microalloyed Steel in Low Temperature Region

Cui Chenshuo, Gao Cairu, Yang Xiongfei, Du Linxiu, Chen Yuxuan

2015, 36(6): 37-43. doi: 10.7513/j.issn.1004-7638.2015.06.008

Abstract(91) PDF(3)

Abstract:
The adverse effect of carbon on the toughness of steel can be reduced in low carbon steel.Through controlled rolling and cooling,high dislocation density of bainite organization was obtained in low carbon steel,and phase transformation strengthening can be achieved. However,single reinforcement method has its limitations. It is necessary to introduce precipitation strengthening on the basis of bainite phase transformation strengthening. The precipitation behavior of high-nitrogen vanadium micro-alloyed steel in bainite region was investigated by thermal simulation experiment and TEM. The specific values of precipitation volume fraction at different temperatures and time,and the enhancing contribution amount and the optimum precipitation temperature were obtained. It provides valuable reference for the development of V-N bainitic steel.

Technological Conditions and Mineralogical Changes of Alkaline Treatment on Ti-bearing Blast Furnace Slag

He Siqi, Sun Hongjuan, Peng Tongjiang, Wu Xiao

2015, 36(6): 44-50,56. doi: 10.7513/j.issn.1004-7638.2015.06.009

Abstract(126) PDF(10)

Abstract:
Ti-bearing blast furnace slag is the industrial waste produced by blast furnace ironmaking in Panzhihua steel plant,and the results of XRD,XRF and metallurgical microscopy analysis of the slag suggest that the main mineral phase includes perovskite,diopside and spinel with 20% of titanium content,and the mineral facies are closely combined. This research adopted alkaline calcinations to dispose the Ti-bearing blast furnace slag and then used deionized water to leach the roasted product for the recovery of SiO₂,Al₂O₃ and the enrichment of titanium component,which can realize separation of the three kinds of valuable component.Through researching the effects of the calcination temperature and time,mass ratio of Na₂CO₃ to slag on the extraction efficiency of SiO₂ and Al₂O₃ and the mineralogical changes in the reaction process,the results show that the spinel precedes diopside to react with Na₂CO₃ but perovskite does not react with the additives. Under the following optimum conditions: calcination temperature 900 ℃,mass ratio of Na₂CO₃ to slag 2:1 and reaction time 180 min,47.52% SiO₂ and 82.97% Al₂O₃ can be extracted.

Removal of the Harmful Elements and Iron Recovery from the Blast Furnace Gas Ash by Chloridizing Roasting

Deng Yongchun, Jia Suqi, Wu Shengli, Jiang Yinju

2015, 36(6): 51-56. doi: 10.7513/j.issn.1004-7638.2015.06.010

Abstract(55) PDF(3)

Abstract:
Due to the complexity of Bayan Obo iron ore,the blast furnace gas ash of Baotou steel has low content of iron but is rich in harmful alkali metal oxides like K₂O and Na₂O as well as oxides of Pb and Zn. Two methods named reduction-evaporation-magnetic separation and chlorination-evaporation were introduced in this paper to transform the mentioned oxides into metals or volatile chlorides respectively by the carbon in the ash or adding calcium chloride into the ash,by which the harmful elements can be separated and the residual iron can be recovered from the ash. The results of reduction-evaporation-magnetic separation experiments show that under condition of 1000 ℃ for 2 h the removal rate of Na,Pb and Zn is respectively 94.21%,98.53% and 91.98%,while K cannot be removed by carbon reduction. With the products of reduction-evaporation at 950 ℃ for 2 h as raw materials for magnetic separation,the recovery rate of Fe reaches 90.24% with 0.6 A current. The results of chlorination-evaporation experiments indicate that the removal rate of Pb and Zn can separately reach 99.62% and 85.56% with 1000 ℃ of temperature. Removal of K and Na is barely affected by temperature with both more than 98% of removal rate. K is removed by chlorination reaction. Nevertheless,Na is separated both by carbon reduction and chlorination in which it's easier for the latter.

Injection of Gravity Precipitator Dust into Blast Furnace

Li Yanjiang, Lü Qing, Lu Jianguang, Liu Xiaojie, Huang Honghu, Wang Yan

2015, 36(6): 57-62. doi: 10.7513/j.issn.1004-7638.2015.06.011

Abstract(114) PDF(5)

Abstract:
The properties of gravity precipitator dust of blast furnace (BF) in Hanbao Iron and Steel Co.,Ltd. (Hanbao),including ignition point,grindability and fluidity were analyzed,and the effect of combustion improver on the burning rate of the dust was studied on pulverized burner. The structural morphology of unburned coal powder and coke in the gravity precipitator dust was tested by lithofacies measurement technology,and the origin of carbon materials in the dust was determined. It is indicated that the carbon content in the gravity precipitator dust of BF in Hanbao is relatively high with a better grindability and fluidity than that of pulverized coal. The microstructure of coke in the gravity precipitator dust can be divided into blocky,flake-like,granular mosaic,flowing and filament-like textures,and the unburned coal powder exists as organic residual carbon,micro-change raw coal,stomata raw coal micro-particles.Considering the economic efficiency for injection of gravity precipitator dust into BF,it is put forward that this technology can be applied to Hanbao.

Research on Carbothermic Reduction for Dephosphorization from Converter Slag by Microwave Heating

Ai Liqun, Zhang Yanlong, Zhu Yiheng

2015, 36(6): 63-67. doi: 10.7513/j.issn.1004-7638.2015.06.012

Abstract(61) PDF(2)

Abstract:
The carbothermic reduction experiments of converter slag were carried out by microwave heating under nitrogen atmosphere. The effects of reduction temperature,carbon equivalent,granularity and reduction time on the phosphorus distribution in slag,iron and gas phase were studied.Results show that pyknotic Fe-C-Mn-P iron bead can be obtained by carbothermic reduction of converter slag by microwave heating. With the increase of reduction temperature,carbon equivalent and the extension of reduction time,the phosphorus into iron and gas phase increases,and the phosphorus in residue decreases. With the decrease in particle size of the steel slag,the phosphorus into iron increases,and the phosphorus in residue and gas phase is decreased. XRD and SEM/EDS analysis of the residue evidences that there is no phosphorus in the residue. This research can lay the basis for the efficient utilization of converter slag.

Effect of V Microalloying in The Hot Working Behavior of High Mn TWIP Steels

Llanos L, Pereda B, Rodriguez-Ibabe J M, Lopez B

2015, 36(6): 68-73,93. doi: 10.7513/j.issn.1004-7638.2015.06.013

Abstract(30) PDF(2)

Abstract:
The present work focuses on the study of static softening and strain-induced precipitation in high Mn (20%~30 %) TWIP steels microalloyed with vanadium. The effect of different V (0.1%,0.2%) and C (0.2%,0.6%,1 %) contents has been investigated. The aim is to evaluate at which conditions (composition/hot working parameters) vanadium remains available for further precipitation hardening after hot rolling. Double hit torsion tests at temperatures in the range 700~1100 ℃ and coiling simulations (from 700 to 550 ℃) were carried out. Advanced characterization techniques have been used,such as EBSD for the determination of the grain size and recrystallized fraction,and TEM for the analysis of the precipitation. The results show that precipitation of vanadium at the hot working temperature range is relatively sluggish. It only occurs for the combinations of 20Mn- 0.6C- 0.2V or 30Mn- 1C-0.1V. Reducing the carbon content to 0.2C,precipitates were only observed after coiling simulation at 650 and 700 ℃. Moreover,in those cases where strain-induced precipitation is observed there is a complex interaction between recovery,recrystallization and strain-induced precipitation. Static recrystallization is severely delayed leading to a major contribution of recovery to softening kinetics.

Effect of Titanium Compounds on the Fluidity of Medium-titanium Slag of Blast Furnace

Zhao Guohong, Zhang Shuhui, Lan Chenchen

2015, 36(6): 74-78. doi: 10.7513/j.issn.1004-7638.2015.06.014

Abstract(41) PDF(2)

Abstract:
The effect of TiO₂ and TiC content on the melting properties of medium-titanium slag at different conditions was investigated using melting properties instrument (RTW). And the viscosity of slag in the tuyere areas of blast furnace (BF) was measured. The results show that,under a reducing atmosphere,the viscosity of the medium-titaniun slag has an obvious turning point with changing temperature. The melting temperature of the slag increases with increasing TiO₂ content of the slag. However,under a neutral atmosphere,both the viscosity and melting temperature of the slag decrease with increase in the content of TiO₂.The viscosity and melting temperature of the slag also increase sharply as the content of TiC increases. The slag in the tuyere areas has poor stability because of the high Ti C and Ti N content of slag. The results can be used as reference for choosing proper operation system of medium-titamium slag in blast furnace.

Research of TiO₂/SiO₂ Influence on Furnace Burden’s Dropping Performance of Vanadium-titanium Magnetite

Wang Fujia, Lü Qing, Chen Shujun

2015, 36(6): 79-83. doi: 10.7513/j.issn.1004-7638.2015.06.015

Abstract(26) PDF(2)

Abstract:
Experiments were carried out in the lab to simulate dropping zone of blast furnace in a high temperature oven,the effect of different TiO₂/SiO₂ on charge softening temperature range,melting temperature range,maximum pressure and other high temperature physical properties had been respectively discussed. The results showed that with the increase of TiO₂/SiO₂ from 0.17 to 0.45 starting softening temperature of furnace charge was increased by 56 ℃,and the end softening temperature was increased by 35 ℃,which indicated the lower position of the cohesive zone; at the same time the renewed pressure temperature was increased by 40 ℃,and dropping temperature was increased by 30 ℃; the maximum pressure (ΔP_max) increased,which led to worse burden permeability; the total characteristic droplet value was increased,which resulted in low droplet performance. It can be concluded that with the increase of TiO₂/SiO₂ droplet performance got worse. Therefore,TiO₂/SiO₂ should be appropriately reduced under the existing burden structural conditions of Cheng steel.

Study on Determination of Composition of Converter Steelmaking Slags for Hot Metal Containing Vanadium and Titanium

Zhou Hai, Tang Ping, Pan Yinhu, Hou Zibing

2015, 36(6): 84-88. doi: 10.7513/j.issn.1004-7638.2015.06.016

Abstract(48) PDF(2)

Abstract:
The hot metal produced by Chonggang has 0.28% vanadium-titanium content,therefore the slag complete melting temperature is lower than that of common slag due to the action of vanadium-titanium oxide in smelting process. As a result,furnace lining is subject to serve erosion and leads a shorter campaign life. In order to address these issues the related research on adjusting slag melting temperature by controlling TFe content was carried out. The relationship between TFe content of slags containing vanadium-titanium oxide and slags complete melting temperature was studied in laboratory by using different basicity of slags. Based on the experimental results approriate content of TFe was obtained and plant trials were carried out. Industrial results indicated that when vanadium-titanium oxide was 4%,bacisity was 4.5,TFe was 21% and MgO was 9%,superheat of the studied slag were equal to that of common slag,and meet high requirements of efficient dephosphorization as well.

Effects of Normalizing Temperature on Impact Toughness of Gas Cylinder Steel 34Mn2V

Dai Huayun, Deng Tongwu, Li Hongguang, Lei Xiuhua

2015, 36(6): 89-93. doi: 10.7513/j.issn.1004-7638.2015.06.017

Abstract(46) PDF(2)

Abstract:

"Mechanical properties of 34Mn2V after being normalized at different temperatures had been measured,and the effects of resulting microstructure on impact toughness had been investigated Results from laboratory and industrial production indicated that impact toughness of 34Mn2V could be improved by using appropriate subcritical normalizing treat. 34Mn2V steels would have a good combination of high strength and improved toughness by after being normalized at lower temperature,and meet the requirements of specifications for high-pressure cylinder. "

Study on Refining Technology of High Quality Cord Steel Production

Zeng Jianhua, Chen Yong, Wang Xinhua, Jiang Min, Yang Senxiang, Zhang Min, Pan Hong

2015, 36(6): 94-100. doi: 10.7513/j.issn.1004-7638.2015.06.018

Abstract(104) PDF(13)

Abstract:
In order to meet the strict requirements of inclusion and cleanliness for high quality cord steel,top slag composition and refining process had been studied through predication and industrial practice.The results show that the inclusions can meet the requirements of plasticity at lower melting temperature when the tap slag basicity (CaO/SiO₂) and Al₂O₃ content are controlled at about 1.0 and in the range of 6%~8%,respectively. Compared with the process of DeS-LD-LF-Ar-CC,the process of DeS-LD-LFRH-CC can lead to inclusion meeting requirements of plasticity and further reducing content of T[O] and [N],and thus improve the cleanliness. The average wire broken ratio of cord steel products is 0.47 time per ton and the fatigue lifetimes reached over 20,000 cycles.

Numerical Simulation of Gas-solid Flow in Fluidized Bed with Inner Partition Plates

Pan Gang, Fan Yong, Peng Yingbin, Wu Wenfei

2015, 36(6): 101-107. doi: 10.7513/j.issn.1004-7638.2015.06.019

Abstract(47) PDF(2)

Abstract:
Numerical simulation of gas-solid flow in the fluidized bed with inner partition plates had been carried out based on EMMS model coupling with two-fluid model in order to investigatethe gas-solid velocity distribution and solid particles volume fraction distribution,as well as the effect of the size of solid particles on the solid particles volume fraction distribution. The result shows the back-mixing of solid particles in the fluidized bed,and presence of the inner partition plates enhances the back-mixing of solid particles. Higher local solid particles volume fractionindicates the agglomeration of the solid particle. Heterogeneous distribution of solid particles exists in the fluidized bed,the solid particles volume fraction distribution along height direction shows“S”shape profile. With the decrease of solid particle size,the amount of solid particles being brought into the zone within 0.1 m to 0.4 m increases. The simulation result could provide theoretical guidance for understanding the gas and sold flow of magnetic roasting in fluidized bed with Inner Partition Plates.

Investigation on the Reduction Kinetics of Carbon Addition to Baiyan Obo Barun Ore by TG-MS Analysis

Shi Xuchao, Zhao Zengwu, Jin Yongli

2015, 36(6): 108-112. doi: 10.7513/j.issn.1004-7638.2015.06.020

Abstract(34) PDF(2)

Abstract:
Taking Baiyan Obo Barun ore as raw material,the carbon reduction process and its kinetics had been studied by by TG-MS analysis under 1 323~1 573 K,and the different minerals activation energy in the reduction process with the carbon gasification reaction as controlling process had been investigated. The present results indicate that the carbon reduction process of Baiyan Obo Barun ore is divided into three stages which are corresponding to three temperature ranges. According to Arrhenius equation,activation energy of the carbon gasification reaction and the gas diffusion was calculated at 96.8 kJ/mol and 76.5 kJ/mol respectively. It is thus concluded that the carbon reduction was controled by carbon gasification reaction under the investigated conditions. In addition,compared with results of Fruehan,Donskoi and other researchers the calculated activation energy of Baiyan Obo Barun ore is relatively low when taking the carbon gasification reaction as controlling process.

Influence of End-point Temperature Control on Dephosphorization for 100t Top and Bottom Combined Blown Converter Process

ABuLikemu·Yasen, Luo Kaimin, Li Jing, Yao Yongkuan, Hu Daofeng, Li Xiang

2015, 36(6): 113-116. doi: 10.7513/j.issn.1004-7638.2015.06.021

Abstract(89) PDF(4)

Abstract:
In order to address the dephosphorization problem of converter at the condition of high temperature,based on a 100 t converter dephosphorization experiments,the effect of end-point temperature control in converter on dephosphorization and measures that increase the dephosphorization capacity of converter with high tapping temperature had been studied in this paper. It is found out that with the increase of temperature,the phosphorus distribution ratio of slag/metal decreases,the dephosphorization capability of slag degrades and the liquid steel phosphorus content increases. Low temperature is an essential requirement for deep dephosphorization of converter. When the tapping temperature is lower than 1 620 ℃,it can realize tapping with liquid steel phosphorus content less than 0.01% even at~3.0 of the slag basicity. Increasing slag basicity leads to high absorption of phosphorus,while reducing P₂O₅ content in slag causes the increase of phosphate capacity of slag,and increasing FeO content in slag oxidizing atmosphere of converter bath increased. All these three measures can reduce the negative effect of high tapping temperature on dephosphorization.

The Mineral Composition and Disseminated Structure Change of Specularite in the Magnetic Roasting Process

Ding Chunjiang, Chen Tiejun, Huang Xianbao, Ma Hao, Su Tao, Qu Wangang

2015, 36(6): 117-122. doi: 10.7513/j.issn.1004-7638.2015.06.022

Abstract(105) PDF(5)

Abstract:
Thanks to its complex composition and subtle disseminated extent,the specularite is a refractory iron ore. In this paper,a magnetic roasting experiment was implemented on specularite ore fines by a rotary kiln. The good roasting results had been achieved,and under the condition of grinding fineness(-0.074 mm) of about 85% and magnetic field intensity of 144 k A/m,a concentrate with Fe grade at 55.22% was obtained. The microscope analysis results indicated insufficient magnetite discrete which affecting the Fe grade of resulting concentrate. The phase analysis and microstructure of iron-bearing minerals during the roasting process suggested that that after magnetic roasting the siderite,limonite and most of specularite had been converted to magnetite,and some magnetite was dissociative,however,the resulting magnetite mainly remained the texture of the original specularite,and the embedded characteristics and disseminated extent was not changed significantly. The most magnetite had coarse band,dense and sparse infected structure,and unevenly embedded in gangue,while the disseminated extent of some magnetite was fine,all these had a significant effect on subsequent dissociation of magnetite.

Causes Analysis and Improvements of Tundish Nozzle Clogging for Aluminized Steel

Duan Yongqing, Chen Xiaohui, Wang Yuecong

2015, 36(6): 123-127. doi: 10.7513/j.issn.1004-7638.2015.06.023

Abstract(64) PDF(2)

Abstract:
In this paper the fluorescence scanning results from the tundish nozzle clogging material in combination with production data including deoxidizing degree of refining process,the effect of calcium treatment,the refining treatment time and the secondary oxidation degree in continuous casting process had been investigated to identify the causes of tundish nozzle clogging when producing the aluminized steel. It is found out that Al₂O₃,CaO·6Al₂O₃,CaO·2Al₂O₃ and MgO-Al₂O₃ are the main components in the clog of tundish nozzle. Clogging has caused by irrelevant refining slag system and insufficient calcium treatment. Therefore a modified process had been utilized which led to reduction of the tundish nozzle clogging probability from 8% to below 3%.

Water Simulation on Mixing Time and Slag Entrapment for a 100t Ladle

Zhao Qingsong, Qin Zhe, Zhang Mingbo, Qiao Zhi, Qiu Shengtao, Lai Chaobin

2015, 36(6): 128-133. doi: 10.7513/j.issn.1004-7638.2015.06.024

Abstract(48) PDF(3)

Abstract:
Based on similarity theory,the 1:4 water model was established for a 100 t ladle in a steel plant,the effect of different positions of bottom nozzle and gas flow-rate on mixing time and slag entrapment was studied by water model experiments. The results showed the mixing time for single nozzle was short when nozzle location distance from center of ladle bottom was between 0.5R and 0.65R; the mixing time was short for double nozzles with location 0.5R and angle of 180°. The mixing time with single nozzle blowing was a little shorter than that of double nozzles blowing when gas flow-rate was same. In order to reduce wall erosion,the nozzle distance from the center of the bottom of ladle should be less than 0.65R.It was concluded that the best blowing argon flow under this experimental condition was 426 L/min,the critical entrapped slag flow was 142 L/min for single nozzle,while 213 L/min for double nozzles,the flow benefitting steel slag interface reaction should be more than 284 L/min.

Property Optimization of Mould Flux for the Surface Quality Problems of ML08Al Billet

Sun Ligen, Fan Sai, Zhu Liguang, Zhang Qi, Han Yihua

2015, 36(6): 134-140. doi: 10.7513/j.issn.1004-7638.2015.06.025

Abstract(77) PDF(2)

Abstract:
The surface defects of ML08Al billet produced by a Chinese steel plant were dominated by angle hook type of oscillation mark and surface concave. Through the analysis of composition and physicochemical properties of the used mould flux,it was found out that the high level of Fe₂O₃ in mould flux would reduce the heat retention,and the liquid slag layer would be thinner. The higher melting point and the fractional melting phenomenon of the mould flux influenced the melting homogeneity of the slag,and the slag-ring readily formed. The mould flux was not easy to form crystallization,this would deteriorate the uniform heat transform for ML08AL initial solidification in the mould. In this research,based on the quality problem of the casting billet,the requirements for physicochemical properties of the mould flux had been fixed. Combining with the calculation of the molten steel solidification in mold via thermal coupling model,the mould flux had been modified in terms of melting point,viscosity,melting rate and alkalinity of the mould flux. The surface quality of the casting billet had been improved significantly by using the optimized mould flux.

Effect of Ce Addition on Microstructures and Properties of 65Mn Steel

Yang Jialin, Jiang Mingzhen, Cui Zilong, Wang Shebin

2015, 36(6): 141-149. doi: 10.7513/j.issn.1004-7638.2015.06.026

Abstract(69) PDF(2)

Abstract:
The 65 Mn steel with different contents of cerium were prepared by a vacuum induction furnace. Optical microscope,SEM,EDS and XRD were employed to analyze the influence of rare earth element on microstructure and mechanical properties of 65 Mn steel. The results are shown as follows: when the content of Ce is within 0~0.0046 %, the cleanliness of molten steel is greatly improved. Large strip Mn S inclusions are transformed into spherical composite inclusions containing MnS and Ce₃S₄ complex inclusions with size below 2 μm. The large oxide inclusions of around 11 μm in size with clear edges and irregular shape are transformed into smooth spherical oxide+Ce₂O₂S+Ce₂O₃ complex inclusions with size less than 2 μm. The size of pearlites decreases from 21.65 μm to 13.74 μm,the lamellar spacing of pearlites reduces from 264 nm to 116.77 nm. The mechanical properties of the steel is improved with Ce content. When the content of Ce is 0.004 6%,the yield strength,tensile strength,elongation and impact toughness reach to 714.38 MPa,864.70 MPa,22.75% and 37 J respectively.

2015, 36(6): 150-151.

Abstract(35) PDF(2)

Abstract:

2015 Vol. 36, No. 6