钢铁钒钛

Preparation of Ti Powder by Calciothermic Reduction of TiO₂ in Vacuum Atmosphere

Jia Jingang, Xu Baoqiang, Xu Min, Yang Bin, Xiong Heng

2013, 34(2): 1-6. doi: 10.7513/j.issn.1004-7638.2013.02.001

Abstract(40) PDF(2)

Abstract:
Calciothermic reduction of titanium oxide is a new process to prepare titanium powder with short route and low cost.In this paper,effect of the amount of additive(CaCl₂) and reduction time on reduced products is studied at 1000℃ in vacuum atmosphere.The results show all the titanium oxide is converted into Ti metal after reduction for 1.5 h when mass ratio of CaCl₂ to TiO₂ in raw materials is 1:4 and the reduction reaction can be promoted with the addition of CaCl₂.After pickling,the obtained Ti powder was detected by X-ray diffractometer,scaning electron microscopy,and oxygen and nitrogen analyzer.It is found that there is no metallic impurity other than Ti in the titanium powder with oxygen content of 1 000×10^-6,nitrogen content of 170×10^-6.

Control of Furnace Bottom Rising during Carbonization of Titanium-rich BF slag

Li Liang

2013, 34(2): 7-10,15. doi: 10.7513/j.issn.1004-7638.2013.02.002

Abstract(37) PDF(3)

Abstract:
The reaction mechanism of high temperature carbonization of titanium-rich BF slag and principles of non-Newtonian fluids mechanics were employed to analyze the cause of furnace bottom rising.The results demonstrate that the primary cause is the deposition of TiC particles in carbonization process of titanium-rich BF slag.To reduce the deposition of TiC,the method of controlling absolute smelting time,smelting temperature and carbon addition is proposed.As a result,uniform BF slag with consistent viscosity is obtained,and smooth tapping is achieved.The problem of furnace bottom rising in high temperature carbonization of titanium-rich BF slag is effectively resolved.

Determination of Operating Parameters for a New Roasting Shaft Furnace for Vanadium Products

Dong Hui, Feng Junsheng, Li Peng, Cai Jiuju, Zhang Jingfan

2013, 34(2): 11-15. doi: 10.7513/j.issn.1004-7638.2013.02.003

Abstract(32) PDF(1)

Abstract:
Through studying on the relationship between operating parameters and utilization coefficient of a new roasting shaft furnace using vanadium-bearing titaniferous magnetite as its major raw material,three levels that affect thermal operating parameters of the shaft furnace are proposed,and the interrelation between these three levels is clarified.Meanwhile,suitable operating parameters under a certain utilization coefficient are identified,which is of great significance to guide operation of the shaft furnace.

Research on Industrial Test of V₂O₃ Production with Rotary Kiln

Chen Haijun, Sun Zhaohui, Yin Danfeng, Liu Fengqiang, Li Qianwen, Lian Zhonghua

2013, 34(2): 16-18,23. doi: 10.7513/j.issn.1004-7638.2013.02.004

Abstract(25) PDF(1)

Abstract:
Major factors influencing V₂O₃ production with rotary kiln were examined.It was found that the impurity content of the products could be regulated by controlling reduction temperature,discharge rate,flow rate of reducing gas,and rotating speed of cylinder.Thus,the product quality was greatly improved.Experiments show that:the gas flow rate is 140~160 m³/h,the discharge capacity of 320~350 kg/h,reaction temperature is 860~920℃,the cylinder speed variable is 37.5 s/r,the V₂O₃ products can meet the ferrovanadium and vanadium nitride production requirements.

Experiment on Preparation of Vanadium Nitride from Vanadium Pentoxide Flake and Graphite

Ning Angang, Ding Huanan, Guo Hanjie

2013, 34(2): 19-23. doi: 10.7513/j.issn.1004-7638.2013.02.005

Abstract(27) PDF(1)

Abstract:
Vanadium pentoxide flake and graphite were used as raw materials to prepare vanadium nitride(VN) with high temperature non-vacuum method in the laboratory.The result shows that ball milling time of vanadium pentoxide flake has influence on the content of nitrogen and carbon in VN.Vanadium pentoxide flake is characterized by its grindability,and the optimal granularity proportioning is 0.48(the flake milled for 15 s):0.52(the flake milled for 2 min).After the milled vanadium pentoxide flake is subject to the agglomeration process(1 490℃) following reduction and nitridation,agglomeration time exerts little effect on the reaction process and chemical composition of product.The agglomeration time can be controlled within 2 to 4 hours.

Multiscale Modeling of the Vacuum Arc Remelting Process of Titanium Alloy

Li Pengfei, Li Jinshan, Sun Chang, Kou Hongchao, Zhong Hong, Chang Hui, Zhou Lian

2013, 34(2): 24-29. doi: 10.7513/j.issn.1004-7638.2013.02.006

Abstract(77) PDF(2)

Abstract:
With the help of the software ANSYS,a finite element model was proposed to simulate the vacuum arc remelting process of a Ø600 mm Ti6Al4V alloy ingot,and the temperature field variation and effect of melting current on the morphology of molten pool in the process was studied.And then the results were coupled to a microstructure simulating model,namely,the CAFD model,to simulate the dendrite growth and segregation behavior of the element V on the solidification front in several characteristic regions.According to the results,the molten pool becomes deeper and mushy zone becomes wider with the increase of the melting current,so that less time is required to achieve steady state of melting;in the steady state of the melting process,relatively short and discrete columnar dendrites grow in the center of the ingot,while continuous columnar dendrites form in the middle-radius and marginal regions.

Microstructure and Properties of Trial-produced Large Size TA15 Alloy Bar

Huang Deming, Wang Huailiu, Chen Xin, Chen Yong, Guo Hua, Bai Lin, Jiang Rengui

2013, 34(2): 30-35. doi: 10.7513/j.issn.1004-7638.2013.02.007

Abstract(39) PDF(1)

Abstract:
The microstructure and properties of TA15 alloy bar were investigated.The results show that there are noticeable differences in the microstructure and properties of TA15 alloy bar produced by different forging processes.In order to obtain desirable microstructure and properties,it is essential that full upsetting and stretching operation should be carried out to break up as-cast structure of TA15 alloy ingot during billet forging,and forging temperature and deformation should also be well controlled when forging finished products.

Preparation of Mesoporous TiO₂ and Its Photocatalytic Decolorization Performance

Zhang Shulin, Li Minjiao, Li Zhiyuan

2013, 34(2): 36-38,45. doi: 10.7513/j.issn.1004-7638.2013.02.008

Abstract(38) PDF(1)

Abstract:
Mesoporous TiO₂ was prepared by a sol-gel method with the assistance of cetyl trimethyl ammonium bromide(CTAB).Then the activity of the photocatalyst so produced for photocatalytic decolorization of methyl orange(MO)solution was evaluated,and the photocatalyst was characterized with BET specific surface.The results indicate that with the ratio of n_CTAB to n_TBOT at 1:4 and calcination temperature at 450℃,mesoporous TiO₂ can be obtained.In addition,the activity of TiO₂ prepared in our experiments for photocatalytic decolorization of methyl orange is two times that of the TiO₂ commercially available.

Research on Increase of Iron Recovery during Smelting & Reduction of Metallized Pellet of Vanadium-bearing Titaniferous Magnetite

Zhang Zongwang, Wu Xuan, Chen Shichao, Guo Zhenting, Yang Huajun, Chen Gang

2013, 34(2): 39-45. doi: 10.7513/j.issn.1004-7638.2013.02.009

Abstract(42) PDF(1)

Abstract:
Production of vanadium-rich pig iron by smelting and reduction of metallized pellets is one of the ways to utilize vanadium-bearing titaniferous magnetite.There is a positive correlation between vanadium and iron recovery rates.In order to improve iron recovery,orthogonal experiments were conducted to investigate the effects of melting and reduction temperature,slag basicity,fluorite proportioning and reduction time on the iron recovery rate.After that,single-factor tests were carried out to optimize process condition for reduction.The results show that among those factors most influencing the recovery rate,the basicity and reduction time ranks first;the temperature comes second and fluorite proportioning exerts the least influence.As the temperature is at 1 530℃,basicity at 0.8,fluorite proportioning at 2%,and reduction time for 40 min,the optimal process condition for iron recovery is obtained.Under this condition,iron and vanadium recovery rates can reach 95.39% and 92.49% respectively,and the separation of slag and iron is good.

Reduction Behaviors of Pellets under High Reduction Potential

Zuo Xiaojian, Wang Jingsong, An Xiuwei, She Xuefeng, Xue Qingguo

2013, 34(2): 46-53. doi: 10.7513/j.issn.1004-7638.2013.02.010

Abstract(16) PDF(2)

Abstract:
As processes of pure oxygen blast and top gas recycling are applied in the top gas recycling oxygen blast furnace,gas compositions in the furnace are dominated by H₂ and CO,which are quite different from those in traditional blast furnace.In order to study the influence of H₂ and CO on reduction behavior of pellets,experiments were conducted with mixed gas H₂-N₂,CO-N₂ and H₂-CO respectively at 1173K by measuring the weight loss.It is found that the reduction degree increases with the increase in H₂ or CO ratio in the mixed gas,but the reduction with hydrogen is faster than that with carbon monoxide.The increase in hydrogen content in H₂-CO mixture improves the reduction rate while the increase in carbon monoxide in H₂-CO mixture lowers the reduction rate.The reduction rate of pellets under H₂-CO atmosphere can not be simply calculated by adding together the reduction rates under H₂-N₂ and CO-N₂ atmosphere.The result shows that dense structure of iron is obtained in the reduction with hydrogen while the iron falls apart in the reduction with carbon monoxide.As gas mixture containing carbon monoxide was taken as reducing agent,the reduction curve showed a declining trend due to carbon deposition at the later stage of reduction.It is concluded that the existence of H₂ could aggravate the carbon deposition while existence of N₂ could restrain carbon deposition.The results of X-ray diffraction and chemical analysis demonstrate carbon in the reduced sample mainly exits in the form of cementite(Fe₃C) and graphite.

Key Technologies for Square/Round Billet Continuous Casting

Chen Yong, Wu Guorong, Pan Hong, Li Jianquan

2013, 34(2): 54-61. doi: 10.7513/j.issn.1004-7638.2013.02.011

Abstract(23) PDF(1)

Abstract:
Main problems associated with square/round billet continuous casting include poor castability of molten steel,longitudinal surface cracks of round billet as well as internal strand defects which are difficult to eliminate during rolling due to low compression ratio.To increase castability of molten steel and improve strand surface and internal quality of the new 6-machine and 6-strand square/round billet caster,continuous casting processes of square/round billet and associated technologies were systematically studied.As a result,integrated technologies covering continuous casting processes and equipments for improving molten steel and strand quality were proposed.Large scale production application of the technologies shows that sequence casting heats in a single tundish can be increased from 4~5 heats to 7~8 heats;defect free rates of square and round billet surface can reach 98.91% and 97.81% respectively.The comprehensive rates of internal defects(such as center porosity,center segregation and center cracks)less than level 1.0 for the square and round billet are above 98.9%% and 98.5% respectively.Furthermore,carbon segregation index is in the range of 0.93~1.09.The results obtained provide significant technological supports for the operation of the new caster,improvement of billet quality,and development of new steel grades.

Sine-wave Inverse Oscillation Synchronous Control Model for 304 Stainless Steel Mold

Liu Cai, Chen Huashun, Liu Yunfeng

2013, 34(2): 62-66. doi: 10.7513/j.issn.1004-7638.2013.02.012

Abstract(10) PDF(1)

Abstract:
Causes of deep oscillation marks on the 304 stainless steel slab were analyzed based on solidification characteristics of the steel.Combined with characteristics of steel structure,the optimum parameters for mold oscillation process were determined.By investigating characteristics of inverse oscillation synchronous control model,a specific model building method for the mold was proposed.It has been concluded that the sine-wave inverse oscillation synchronous control model designed for the 304 stainless steel can reduce the depth of oscillation marks and ensure good slab surface quality.The research results can not only be applied to the production of 304 austenitic stainless steel,but also serve as guidance to the establishment of synchronous control model for other kinds of steels.

Study on Optimization of the Baffle for Two-strand Slab Caster's 80 t Tundish

Tian Yonghua, Bao Yanping, Li Yihong, Shen Xiaowei, Wang Min, Tang Dechi

2013, 34(2): 67-72. doi: 10.7513/j.issn.1004-7638.2013.02.013

Abstract(17) PDF(2)

Abstract:
Flow field of the two-strand slab caster's 80 t tundish equipped with flow control devices in a certain domestic steel plant was studied.Based on this research,the effects of position and height of tundish dam on flow field were tested and analyzed.It is concluded that with a double-deck turbulence controller,the flow field of the tundish was the most reasonable when the dam of 400 mm is installed 2 000 mm away from long nozzle;the structure of the flow control device consisting of turbulence controller and dam is so simple that it can protect molten steel from being polluted by its scouring to the dam or other tundish devices.Compared with previous tundish,the average residence time of fluid is increased from 292 s to 380 s,dead area ratio decreased from 37.3% to 18.5%,and ratio of piston area to dead area increased from 0.35 to 0.65,which is beneficial to uniformize steel temperature and composition,maximize inclusion floating and removal and improve cleanness of slab.

Comparison of Fluid Flow, Heat Transfer and Solidification Behaviors of H² Mold with Different Widths

Xu Mianguang, Wang Peng, Liu Heping, Chen Yuanqing

2013, 34(2): 73-78. doi: 10.7513/j.issn.1004-7638.2013.02.014

Abstract(12) PDF(1)

Abstract:
The H² funnel-shaped mold for FTSC process can produce the slab with width of 860 mm~1 730 mm.The study on molten steel flow,heat transfer and solidification behavior of H² mold with different widths can help to make a better understanding about metallurgical behaviors in the H² mold and provide guidance for equipment manufacturing and process parameters optimization.Numerical simulation technique is employed to study the fluid flow,heat transfer and solidification behaviors in the mold with the casting speed of 4.5 m/min and the H² mold widths of 900 mm,1 300 mm,and 1 700 mm.The results show that with the increase in mold width,the flow field has noticeable change,and the wave fluctuation at the free surface near the SEN intensifies.Under the conditions of different widths of mold,the differences in surface temperature and solidified shell thickness of the slab at the exit of the mold are mainly reflected near the narrow face.

Viscosity Properties of Flux under High Frequency Electromagnetic Field

Wang XingJuan, Zhu Liguang, Liu Ran, Jia Xiangming, Li Zhihao

2013, 34(2): 79-83. doi: 10.7513/j.issn.1004-7638.2013.02.015

Abstract(18) PDF(1)

Abstract:
Mould flux is a very important function material in continuous casting process.The viscosity of flux under high frequency electromagnetic field were tested by rotational viscosity tester and a measurement device for electromagnetic characteristics of flux viscosity under high temperature conditions.With finite element finite element,the flow field of flux under high frequency electromagnetic field were simulated.The results show that high frequency electromagnetic field make the flux viscosity rising significantly.With basicity rising(R=0.66~0.91),the viscosity increasing rate at 1 300℃ grows larger,but the melting temperature incressing rate decreasing gradually.It may be the main reason for the significant increasing of flux that the electromagnetic forces disrupt the ordered structure of flux and make the ion rate increaseing.

Effect of Ultra-fast Cooling on Microstructure and Mechanical Property of Vanadium Micro-alloyed Steel

Chen Jing, Xu Guang, Wang Fengqi, Yang Jing

2013, 34(2): 84-87. doi: 10.7513/j.issn.1004-7638.2013.02.016

Abstract(13) PDF(1)

Abstract:
Rolling and cooling experiments were conducted under ultra-fast cooling(UFC) condition to investigate the influence of UFC on microstructure(including homogeneity of microstructure) and mechanical property of vanadium micro-alloyed steel.Following UFC process,there is martensite on the surface and bainite and a small amount of martensite in the core of the specimen while with conventional cooling process,there is bainite and a small amount of martensite on the surface and a small amount of massive ferrite,bainite and martensite in the core of the specimen.The tested steel exhibits increase in strength and slight decrease in plasticity after UFC.Different microstructures and inhomogeneous cooling are observed on the surface and in the core of the 20 mm thick rolled pieces subject to UFC.

Analysis on Decarburization of 50CrV4 Steel and Its Effect on Hardenability

Yang Lin, Yu Chibin, Bao Siqian, Ding Bei, Yu Chong, Cheng Jian, Mao Xinping

2013, 34(2): 88-92. doi: 10.7513/j.issn.1004-7638.2013.02.017

Abstract(16) PDF(1)

Abstract:
Surface decarburization is one of the important processes in hot-rolled plate production.Decarburizing characteristics of 50CrV4 steel and its effect on hardenability of steel at 650~1 100℃ were investigated in the laboratory.According to the diffusion theory,the test data were studied through regression analysis.The research shows that the decarburized depth increases with the increase of temperature or holding time,and the depth is proportional to the extraction of the holding time.There is a minimum value in decarburized depth appearing at 1 000~1 100℃.The hardness of the steel decreases with the increase of the decarburized depth.

Analysis on Metallographic Structure and Surface Defect of Heat-resistant Austenitic Stainless Steel 309S

Chen Xingrun, Wang Jianze, Wang Jianxin, Pan Jixiang

2013, 34(2): 93-97. doi: 10.7513/j.issn.1004-7638.2013.02.018

Abstract(7) PDF(1)

Abstract:
A research was carried out to investigate the as-cast,as-rolled and as-annealed metallographic structure as well as as-annealed mechanical property and surface defects of heat-resistant austenitic stainless steel coil 309S which was produced with smelting-rolling-annealing and pickling process.The results show that under the above three conditions,the steel is composed of austenite and high temperature residual ferrite that could not be eliminated by heat treatment.For the as-rolled and as-annealed structure,there is low content of ferrite near the surface and high content of ferrite in the core along the thickness direction.The product's mechanical properties are not affected by the high temperature residual ferrite.Fine grinding of the continuously cast slab can avoid surface defect of the product.

Study on the Model for Static Recrystallization of DC03 Steel

Li Lixin, Lei Hao, Fang Yanzi, Yuan Xiang, Su Yumeng, Pi Daguang

2013, 34(2): 98-102. doi: 10.7513/j.issn.1004-7638.2013.02.019

Abstract(16) PDF(1)

Abstract:
Through the method of orthogonal design,experiments were carried out to simulate the process conditions of high-temperature short-time continuous annealing and low-temperature long-time batch annealing of DC03 steel in the high-temperature chamber-type electric resistance furnace.Static recrystallization softening rate of DC03 steel under various annealing conditions after cold rolling was measured by using back-extrapolation method and its relationship with deformation degree,annealing temperature and annealing time was studied.The model was built based on Avrami equation and compared with static recrystallization kinetics model in double-pass hot working.The result indicates that annealing temperature has more influence on static recrystallization rate between two passes of hot deformation than that after cold rolling while the influence of holding time on them is totally opposite to that of annealing temperature.

Study on “Black Line” on the Edge of SPHC Hot-rolled Strip

Chen Liansheng, Gu Huige, Song Jinying, Tian Yaqiang, Zhang Dawei, Wei Yingli, Shen Yongge

2013, 34(2): 103-108. doi: 10.7513/j.issn.1004-7638.2013.02.020

Abstract(12) PDF(1)

Abstract:
In order to eliminate the black line defect occurring on the edge of SPHC hot-rolled strip after pickling,the reasons for producing black line were investigated by means of microscope,scanning electron microscopy,energy dispersive spectroscopy and other related test equipment.The results show that the main element in defect area is Fe,and the microstructures are dominated by ferrite and a small amount of pearlite,accompanied by coarse crystal and mixed crystal.It is found that the black line is formed from edge cracks which are turned over and brought to the strip surface due to tensile stress.By improving the strip's edge and corner quality and optimizing vertical roll type and rolling process,the black line can be effectively eliminated,which ensures good product quality and yield,thus satisfying the need of market.

2013, 34(2): 109-110.

Abstract(14) PDF(1)

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2013 Vol. 34, No. 2