钢铁钒钛

Competitive Diffusion of Ions during Oxidation of Ilmenite

Zhang Jianbo, Zhu Qingshan

2013, 34(3): 1-7,18. doi: 10.7513/j.issn.1004-7638.2013.03.001

Abstract(29) PDF(1)

Abstract:
The oxidation mechanism of ilmenite was investigated by studying the morphologies,phase compositions and kinetics of Panzhihua ilmenite,which was oxidized in air at the temperature of 600~750℃.The results reveal that the oxidation mechanism of ilmenite is a kind of competitive diffusion of Fe and O ions.At the beginning,as ilmenite is oxidized by the outdiffusion of Fe ions,Fe₂O₃(gathering on the particle surface) and Fe₂Ti₃O₉ are obtained.When the oxidation process proceeds to a certain extent(the hematite layer grows to 1~2 μm),the reaction is dominated by the indiffusion of O ions,which leads to the formation of Fe₂O₃ and TiO₂ in the particle inner.As the transition of Fe ions diffusion to O ions diffusion always happens at the time when the thickness of hematite layer on the surface reaches to 1~2 μm,and the transition time almost has nothing to do with the temperature and particle size of ilmenite,the proportion of Fe ion diffusion increases with the decrease of particle size of ilmenite in a typical oxidation process.But for the O ion,the reverse is true.

Thermodynamic Analysis on Ilmenite Separation by Magnetic Roasting

Liu Yunlong, Guo Peimin, Pang Jianming, Zhao Pei

2013, 34(3): 8-12. doi: 10.7513/j.issn.1004-7638.2013.03.002

Abstract(42) PDF(1)

Abstract:
In order to investigate the possibility of separation of Fe₃O₄ and TiO₂ in ilmenite,oxidation and reduction thermodynamics of ilmenite at low temperature is analyzed in this paper.The results show that through direct magnetic roasting,FeTiO₃ can be oxidized to Fe₃O₄,but the reaction is difficult to be controlled,because Fe₃O₄ tends to be overoxidized to Fe₂O₃ and Fe₂TiO₅;in the existence of the CO₂ and H₂O,FeTiO₃ tends to be directly oxidized to Fe₂O₃ and Fe₂TiO₅ rather than Fe₃O₄.Therefore,the ilmenite cannot be directly magnetized by these two kinds of gas.Through indirect magnetic roasting,after oxidation of FeTiO₃ with oxygen or air,Fe₂O₃ and Fe₂TiO₅ can be reduced to Fe₃O₄ with a low-concentration CO at low temperature.According to the above results,a new process for separation of iron and titanium in ilmenite is put forward and iron concentrate powder and titanium slag can be obtained through oxidation and magnetization roasting,and then magnetic separation of the ilmenite.

Effects of Impurities on Ammonium Polyvanadate Precipitating

Yang He, Mao Linqiang, Xue Xiangxin, Liu Dong

2013, 34(3): 13-18. doi: 10.7513/j.issn.1004-7638.2013.03.003

Abstract(32) PDF(3)

Abstract:
Effects of impurities such as Cr,P,Si,Cl^-and SO₄^2-on ammonium polyvanadate are investigated as ammonium polyvanadate is precipitated with acidic ammonium salt.The results show that the increase of Cr concentration significantly reduces the vanadium precipitation rate,especially for the vanadium liquid with low concentration;Si and SO₄^2-exert little influence on the precipitation,while P has a noticeable effect as its concentration is above 0.1g/L,the precipitation rate of vanadium is below 75%;the effect of low-concentration Cl^-is not notable,however,when the concentration of NaCl is above 100 g/L,the precipitation rate of vanadium is below 20%.

Study on Preparation of TiO₂ Pigment with Sub-molten Salt Process from Titanium-bearing Slag Obtained in Direct-reduction Ironmaking

Wang Shuyi, Jin Yingjie, Chu Jinglong, Qi Tao

2013, 34(3): 19-23. doi: 10.7513/j.issn.1004-7638.2013.03.004

Abstract(17) PDF(1)

Abstract:
Using titaniferous slag from the process of ‘coal-based direct reduction in rotary hearth furnace-further reduction and smelting and separation in electric furnace’ as raw material,TiO₂ Pigment with a content of titanium dioxide over 98% was produced by sub-molten salt process.The optimum testing conditions for the production were studied,aiming to find out the optimum reaction time,alkaline ratio,reaction temperature,and granularity of the raw material.After multistage solid-state ion exchange and removal of impurities,titaniferous solution(C_TiO₂=180 g/L,effective acid coefficient F=2.0) was prepared from the intermediate product sodium metatitantate.Through hydrolysis,metatitanic acid with a particle size of D(0.5)=1.2 μm was obtained,and then it could be calcined to anatase TiO₂ products.

Industrial Experiment of FeV80 Smelting with Two-step Process

Zhou Fang

2013, 34(3): 24-28. doi: 10.7513/j.issn.1004-7638.2013.03.005

Abstract(31) PDF(1)

Abstract:
Industrial tests for two-step FeV80 smelting by tilting furnace were carried out to investigate the effects of the aluminum proportioning coefficient,power-on smelting time and refined materials on technical indicators and find out the optimized technical controlling parameters of smelting.The result shows that FeV80 alloy produced by two-step smelting process with tilting furnace meets GB/T4139-2004 standard,and is characterized by better composition uniformity.Vanadium content in the slag is noticeably decreased to lower than 0.6%,so the slag can be directly dumped as waste.Furthermore,the average vanadium recovery rate smelting is 96.5%,higher than that in the one-step process.

Preparation Technique of High Quanity Ammonium Metavanadate

Hou Haijun

2013, 34(3): 29-32. doi: 10.7513/j.issn.1004-7638.2013.03.006

Abstract(49) PDF(4)

Abstract:
This paper analyzed the cause of high impurities in ammonium metavanadate products at the aspect of the production process and selection of process control parameters.To control the content of impurities in AMV,the change trend of the impurity content after filtering,adjustment of the impurity removal coefficient and the selection of ammonium salt in basic precipitation were investigated in different temperature conditions.In the technological process of preparing ammonium polyvanadate(APV) by low ammonium salt precipitation,return dissolving the APV to remove the impurity,and then precipitating AMV in basic condition,the impurities in AMV could be reduced from 0.05% to 0.02% effectively,which was of important guiding significance on the improvement of high purity vanadium production technology,and laid a foundation to develop new products for Vanadium industry Co.,Ltd.,Pangang group.

Progress and Prospect of Industrialization of Comprehensive Utilization of Pangang Blast Furnace Slag(High Titanium Content)

Lu Ping

2013, 34(3): 33-38. doi: 10.7513/j.issn.1004-7638.2013.03.007

Abstract(54) PDF(3)

Abstract:
Years of research on the comprehensive utilization of Pangang blast furnace slag(BF slag) is reviewed,and the progress in laboratorial and industrial technologies for titanium tetrachloride production by "high-temperature carbonization and low-temperature chlorination" from high titanium content BF slag.At present,the 10kt/a titanium tetrachloride production line employing "high-temperature carbonization and low-temperature chlorination" technology is capable of continuous production.In stability tests and trial production,the average carbonation rate of dioxide titanium in blast furnace slag was 88.20% in the high-temperature carbonization pilot line,the average chlorination rate of carbide titanium in carbonization slag was 85.35% in the low-temperature chlorination line,and the total recovery rate of titanium in BF slag in these two lines reached 75.45%.The test result shows that the process with significant economic and social benefits is feasible in technology,indicating an optimistic prospect in industrialization.

Analysis and Calculation on Recycling of the Sulfuric Acid Waste from Sulfate Titanium Dioxide Production

Du Jianqiao

2013, 34(3): 39-43. doi: 10.7513/j.issn.1004-7638.2013.03.008

Abstract(43) PDF(3)

Abstract:
To investigate recycling of sulfuric acid waste from titanium dioxide production,the material balance of sulfuric acid during production was analyzed and the effect of heat released from acidolysis reactants diluted with concentrated sulfuric acids instead of water on the temperature of the reaction system was also calculated.Finally,conditions to achieve a 100% recycled use of the 50% concentrated sulfuric acid in sulfate TiO₂ production were discussed.The results indicated that the minimum concentration of the spent acid for acidulation of ilmenite was 50% and the acid concentration for reaction should be no more than 81% to achieve a 100% recycled use of concentrated acid waste without external heat supply.

Research on Recovery of Iron from Ti-bearing Blast Furnace Slag by Wet Low-intensity Magnetic Separation

Zhou Guobiao, Peng Tongjiang, Sun Hongjuan, Xian Haiyang

2013, 34(3): 44-49. doi: 10.7513/j.issn.1004-7638.2013.03.009

Abstract(34) PDF(1)

Abstract:
Based on research status of comprehensive utilization of titanium rich blast furnace slag(BF slag)in Pangang,the technical approach of "Fe recycling by magnetic separation-dealuminizing by activation-Ti leaching by acidolysis "was proposed to recycle valuable elements including Fe,Al,and Ti in the slag.Mineral phases and iron occurrence in the Ti-bearing BF slag were analyzed by means of XRD and metallographic microscope.The technologies of single low-intensity magnetic separation and staged grinding and low-intensity magnetic separation were adopted respectively for iron recycling.The results show that the main mineral phases of the BF slag are perovskite,diopside and spinel,and metallic iron existing as globularity mostly distributes in the diopside.Except grinding cost saving,the utilization of the staged grinding and low-intensity magnetic separation also boosts an iron concentrate of 63.5% with a recovery rate of total iron at 64.2%,which creates favorable conditions for subsequent dealuminizing and Ti leaching.

Technologies and Practices of BF Intensified Smelting of Vanadium-bearing Titanomagnetite at Pangang

Fu Weiguo, Wen Yongcai, Xie Hongen

2013, 34(3): 50-53. doi: 10.7513/j.issn.1004-7638.2013.03.010

Abstract(31) PDF(6)

Abstract:
Technologies of increasing proportion of vanadium-bearing titanomagnetite used as feedstock for BF smelting at Pangang are introduced.By optimizing sintering material structure and BF burden structure,strengthening BF operation,and upgrading coke quality,the quality of raw material and fuel into blast furnace and metallurgical properties of burden were drastically improved,and intensified smelting with higher proportion of vanadium-bearing titanomagnetite as feedstock for BF was achieved.Based on 50% grade of burden,desirable technical and economic indices were achieved,with annual average utilization coefficient reaching 2.4~2.5 t/(m³·d).

Experimental Research on Ultra-low Phosphorous Steel Smelting

Zhou Jian, Qin Zhe, Hou Zewang, Qiu Shengtao, Gan Yong

2013, 34(3): 54-58. doi: 10.7513/j.issn.1004-7638.2013.03.011

Abstract(11) PDF(1)

Abstract:
After investigating the influence of some additives(i.e.,Li₂O,Na₂O,K₂O,CaF₂) on hot metal dephosphorization in 15 kg vacuum induction furnace,production test in 120 t top and bottom combined blown converter was carried out to smelt the ultra-low phosphorous steel through adding lepidolite ore which contains Li₂O,Na₂O and K₂O during the dephosphorization period.The experiment results of 15 kg vacuum induction furnace show that through adding 15% Li₂O to the dephosphorization slag,the phosphorus mass fraction was decreased from 0.109 4% to 0.003% with a dephosphorization ratio up to 97.3%,and the apparent dephosphorization rate reach to 0.021%/min within 5min since the beginning of dephosphorization.Furthermore,in the production test,the average phosphorus mass fraction and the average dephosphorization ratio of semi-steel are 0.035% and 68.1% with the original phosphorus content in the molten iron charged into converter at 0.109 9%.In addition,the average phosphorus content and the average dephosphorization ratio at the BOF endpoint are 0.005 8% and 94.8%.The corresponding minimum phosphorus content and the maximum of dephosphorization ratio at the BOF endpoint are 0.003% and 97.3%,respectively.

Study on Inclusions in the First Slab of Ultra-low Carbon Steel

Yi Zhengming, Xiao Hui

2013, 34(3): 59-62,66. doi: 10.7513/j.issn.1004-7638.2013.03.012

Abstract(13) PDF(1)

Abstract:
Through studying the varying pattern of inclusions in the first slab of ultra-low carbon steel produced by BOF-RH-CC process,it is concluded that the nitrogen content and T[O] obviously decrease with increasing casting length;generally,the quantity of micro and large inclusions decrease with the increase of casting length.The micro inclusions in the first slab are mainly Al₂O₃,TiN and Al₂O₃-TiN,and the large inclusions are mainly TiN,SiO₂,Al₂O₃,K-containing aluminosilicate and Na-containing calciumaluminum.This study suggests that the inclusion quantity in the first slab of ultra-low carbon steel is closed to the level of normal slab at and after the length of 3.5 m.

Influence of Mould Wear on Strand Heat Transfer

Guo Wang, Liu Zengxun, Zhu Liguang, Tong Zhixin

2013, 34(3): 63-66. doi: 10.7513/j.issn.1004-7638.2013.03.013

Abstract(13) PDF(1)

Abstract:
Based on the genetic characteristics of stress in the solidified shell,a coupled thermo-mechanical model for strand was established.Heat transfer and stress analysis on the strand in mould were completed by ANSYS.The shell thickness,surface temperature and air gap distribution were contrasted between new and worn moulds.The results suggested that the hot pot would appear apart from the corner area after mould was worn.Air gap distribution area extended from 10 mm to 80 mm apart from the corner.The maximum thickness increased from 0.1 mm to 1.2 mm.

Effect of Ce on the Purifying Degree and Inclusion modification of Low Carbon and High-Strength Steel

He Lei, Hou Yang, Yuan Chunyang, Guo Qingli, Wang Shebin

2013, 34(3): 67-71. doi: 10.7513/j.issn.1004-7638.2013.03.014

Abstract(10) PDF(1)

Abstract:
In order to improve the refining process of low carbon and high-strength container plates,four steel samples were prepared by adding Ce into the molten steel containing 0.08C-0.60Si-0.45Mn-0.3Cu-0.09P(mass%) at 1 873 K in a 3.0 kg vacuum induction furnace under Ar atmosphere(800 Pa).The chemical composition,SEM and EDS analytic results were obtained to study the cleanliness of 0.08C-0.60Si-0.45Mn-0.3Cu-0.09P-xCe(mass%)steel and the change of inclusions.When content was 0,the inclusions were MnS-MgO-Al₂O₃ system;when content was in the range of 0.008%~0.020%,the inclusions were MgO-Al₂O₃-Ce₂₂O₃>O₂S system;when content was 0.043%,the inclusions became FePCe-Ce₂₂O₃>O₂S system and spherical inclusions of 2 μm or even smaller than 0.3 μm were transformed from 7 μm inclusions with irregular shape.The residual area of inclusions in the steel matrix was reduced by 58.1% and the size of inclusions was below 3 μm approximately.The liquid steel was cleaned profoundly due to the floating up and removal of inclusions which were formed by Ce deoxidation and desulfuration.The formation of different kinds of inclusions was relevant to the relative thermodynamic conditions.

Influence of Mold Electromagnetic Stirring on Carbon Segregation on Continuously Cast Blooms of Bearing Steel

Sun Yanhui, Li Shiwei, Liu Fengjun, Zhao Haiyang

2013, 34(3): 72-76,87. doi: 10.7513/j.issn.1004-7638.2013.03.015

Abstract(10) PDF(1)

Abstract:
As metallurgical targets of mold electromagnetic stirring(M-EMS) in continuous casting of bloom for bearing steel were not fully achieved in Nanjing steel,experiments for optimizing process parameters of M-EMS were carried out.Carbon segregation of cast bloom and rolled products at different electromagnetic stirring parameters and stirring patterns was studied.The results show that there is negative segregation in the core and edge of bloom,and positive segregation in the 1/4x bloom,with the carbon segregation index of 320 mm×480 mm bloom at 0.87~1.05;the carbon segregation index of rolled metal is at 0.94~1.03.Positively and negatively alternating electromagnetic stirring is helpful to reduce the carbon segregation.When electromagnetic stirring current is relatively strong,negative segregation is severer in the core,and with the increase of the stirring electric current,the white zone moves to the bloom center and its width increases.The carbon segregation hands down from cast bloom to its rolled products.

Research on Strengthening Mechanism of Microalloying Elements in Low-carbon Bainite Steels Produced with TMCP Process

Li Bingjun, Li Jing, Liu Weijian, Zhang Ti

2013, 34(3): 77-82. doi: 10.7513/j.issn.1004-7638.2013.03.016

Abstract(5) PDF(1)

Abstract:
Microstructures and second phase precipitates in microalloyed high-strength steel Q690D produced with TMCP process are analyzed by means of optical microscope(OM),transmission electron microscopy(TEM),and energy dispersive spectroscopy(EDX) in order to study the strengthening mechanism.It is found that the surface microstructure is mainly consisted of lath bainite,a small amount of granular bainite and acicular ferrite,and the central microstructure of granular bainite and polygonal ferrite.Most of the second phase precipitates are niobium and titanium carbonitride with a size of about 20nm in length,dispersively distributing in the matrix in the shape of square or quasi-square.Boron,mainly existing in the form of acid-soluble boron,remarkably increases the hardenability of the steel.Results show the strengthening mechanism is dominated by bainite transformation strengthening,fine grain strengthening and precipitation strengthening.

Analysis on Formation of Cracks in High Nb and Ti Content Billet and Control Measures

Liang Wen, Wu Run, Chen Jiqing, Pei Hai, Zhang Pengwu, Liu Zhiyong, Han Rongdong

2013, 34(3): 83-87. doi: 10.7513/j.issn.1004-7638.2013.03.017

Abstract(11) PDF(1)

Abstract:
The causes of cracks in high Nb and Ti content billet in the process of steel rolling was investigated by pickling,metallography detection and energy spectrum analysis.The results show that the direct reason for crack forming is the inner microcracks caused by large amount of carbonitride separated out in the process.It is proved in the thermoplasticity test that there is a brittleness temperature range at 660~910℃ for the steel.The cracks can be avoided through controlling chemical compositions,stabilizing the casting speed and liquid level in the mold,and reducing the cooling rate in the secondary cooling.

Development and Welding Thermal Simulation Test of the Structural Steel Q460D for High Heat Input Welding

Li Min

2013, 34(3): 88-92. doi: 10.7513/j.issn.1004-7638.2013.03.018

Abstract(18) PDF(1)

Abstract:
The structural steel Q460D for high heat input welding was trial-manufactured by using a 50 kg vacuum electrical furnace,a small-sized experimental rolling mill and other equipments.Cu,instead of Mo and Cr,was the main strengthening element of the steel plates,so the cost of plates was effectively controlled.The steel plate was smelted by using Ti deoxidation process,and then after controlled rolling,controlled cooling and tempering treatment,final products were obtained.The steel plates under different tempering temperature were studied by mechanical property tests and welding thermal simulation test.The results show that when the temperature of tempering treatment was 610℃,the strength and toughness of the plates match best.Under 100~120 kJ/cm high heat input welding conditions,the-20℃ low temperature impact energy of the welding coarse-grained heat-affected zone(CGHAZ) of the plates so produced is greater than 100 J,and the CGHAZ strength is not less than the substrate.

Study on Static-recrystallization and Phase Transition under Continuous Cooling of Offshore Platform Steel F550

Wang Huanyang

2013, 34(3): 93-96. doi: 10.7513/j.issn.1004-7638.2013.03.019

Abstract(7) PDF(1)

Abstract:
Double-pass compression tests were carried out on the MMS-200 thermomechanical simulator to obtain static-recrystallization curves of offshore platform steel F550.By using a combined method of dilatometry and metallography,dilatometric curves of continuous cooling of F550 were measured,and dynamic CCT curves were obtained.Transformation process of austenite during continuous cooling and microstructure of the transformed products were studied.These tests could provide references for the on-site rolling process of F550.

Study on Relationship between Temperature and Thermal Conductivity in Different Kinds of Steel

Meng Yuyong, Wang Jianjun, Zhou Li, Wang Xianghong

2013, 34(3): 97-100,106. doi: 10.7513/j.issn.1004-7638.2013.03.020

Abstract(94) PDF(7)

Abstract:
To have systematical understanding of the varying pattern of thermal conductivity with temperature in different steels,the method of laser light scattering was used to measure the thermal conductivities of steel 08 A,35 K,45^# and GCr15 from 28℃ to 1 060℃.Through drawings and analyses,the results can be concluded that different steels have different thermal conductivities at the same temperature,and at room temperature,the thermal conductivity of the high-carbon steel is lower than that of the low-carbon steel,which indicates the carbon-content has an effect on the coefficient of thermal conductivity;the same steel also has different thermal conductivities at different temperatures.The thermal conductivities of all kinds of steel decrease with the increase of temperature below phase transformation temperature(700~800℃),and then increase with the temperature rising above.

Solidification Structure in La and Ti-containing FeCrAl Stainless Steel

Wang Zhen, Liu Jianhua, Yu Xiaoyan

2013, 34(3): 101-106. doi: 10.7513/j.issn.1004-7638.2013.03.021

Abstract(6) PDF(1)

Abstract:
Optical Microscope(OM) and Scanning Electronic Microscope(SEM) were used to analyze the solidified structure of La and Ti-containing FeCrAl stainless steel.The results show that the grain size in pure ferrite solidified structure without La and Ti treatment can be relatively big with the average values at 4.64 mm in longitudinal section and 4.71 mm in cross section.The grain size can be noticeably refined by addition of La as well as Ti to the steel.In addition,Ti can improve equiaxed grain ratio at the same time.The high-melting point second-phase particle formed after La and Ti addition is beneficial to refine grain and the large amount of TiN separated out in the steel contributes to improve equiaxed grain ratio.

Analysis on Occurence and Cause of Linear Defects on Cold-rolled Sheet

Song Jinying, Zhao Yuan, Chen Liansheng, Wei Yingli, Tian Yaqiang, Yang Dong

2013, 34(3): 107-112. doi: 10.7513/j.issn.1004-7638.2013.03.022

Abstract(6) PDF(1)

Abstract:
Types,causes and influencing factors of linear defects on cold-rolled sheet were analyzed by such detection means as field emission scanning electron microscopy,energy dispersive spectroscopy and optical microscopy.The results show that typical linear defects on the sheets include bubble,scratch,inclusion and press-in of iron oxide scale,and most of the inclusions are entrapped from casting powder.In order to eliminate those typical linear defects,countermeasures for the processes like converter steelmaking,tundish metallurgy,and high pressure water descaling are proposed.

2013, 34(3): 113-114.

Abstract(14) PDF(1)

Abstract:

2013 Vol. 34, No. 3