钢铁钒钛

Study on Extraction Separation of Non-roasting Acid Leachate of Vanadium Slag

Yu Bin, Sun Chaohui, Xian Yong, Tang Hongjian

2014, 35(5): 1-6. doi: 10.7513/j.issn.1004-7638.2014.05.001

Abstract(30) PDF(1)

Abstract:
Extracting-stripping process was used to separate vanadium from other elements in the acid leaching solution of vanadium slag without roasting.The effects of extraction temperature,extraction time,pH value,composition of extraction agent,extraction phase ratio,stripping time,acid concentration and stripping phase ratio on the extraction rate and stripping rate of vanadium were investigated by single factor experiments.The results indicate that the extraction rate of V and Fe is respectively 74.49% and 1.92% without any other impurity ion in organic phase,under the temperature of 20℃,leaching solution pH=2.0,organic phase composition of 20% P204+5% TBP+75% sulfonated kerosene,phase ratio (O/A)=1:1 and shaking time of 5 min;the total extraction rate of V is 97.89% after 4-stage cross-flow extractions under the conditions mentioned above.The stripping experiment results indicate that,under the stripping time of 4 min,acid concentration of 200 g/L and phase ratio (O/A) of 5:1,the stripping rate of vanadium is 98.58% without iron ions in the water phase.

Effects of Hydrolysis Conditions on Rutile Titanium White Pigment Prepared by Low Concentration of Titanyl Sulfate Solution

Chen Hua, Tian Congxue, Liang Anbing

2014, 35(5): 7-11,30. doi: 10.7513/j.issn.1004-7638.2014.05.002

Abstract(28) PDF(0)

Abstract:
The rutile titanium white pigment was prepared by thermal hydrolysis sulfate process without adding external seed crystals,using low concentration of industrial titanyl sulfate solution as raw material.The effects of pre-adding water,feed rate and aging time on particle morphologies,particle size distributions and pigment properties of the rutile titanium white were investigated,and the samples were characterized by particle size distribution test,SEM,XPS,TEM and pigment properties test.The results show that the optimal hydrolysis conditions are 22% of the pre-adding water,8.3 r/min of feed rate and 30 min of aging time,and the obtained rutile titanium white has suitable particle size,narrow particle size distribution and excellent pigment properties.The effect order on the pigment performances is:preadding water>feed rate>aging time.

Research on Thermal Behaviors of Shaft Furnace for Vanadium Extraction from Stone Coal

Feng Junsheng, Dong Hui, Wang Aihua, Zhang Jingfan, Hu Jia

2014, 35(5): 12-16. doi: 10.7513/j.issn.1004-7638.2014.05.003

Abstract(21) PDF(1)

Abstract:
The shaft furnace for vanadium extraction from stone coal is the roasting equipment with independent intellectual property rights,which has the advantages of smaller initial investment,higher vanadium conversion rate and lower energy consumption,etc.The research on thermal behaviors of the shaft furnace was carried out by means of thermal testing to find out the furnace conditions and energy consumption,and the measures for the energy saving,stable and efficient operation of the shaft furnace were proposed.The conclusions are as follows:① The oxygen concentration and roasting time can basically meet the requirements for pellet roasting with uneven distribution of gas flow in the shaft furnace.②The main measures for stabilizing the furnace performances are ensuring the uniformity of qualities and quantities of the fuel,combustion-supporting and cooling air provided to the furnace and the flue gas from the furnace top,improving the pelletizing process of raw stone coal and keeping the continual feeding and discharging of pellets.③ The thermal efficiency and exergy efficiency of shaft furnace are respectively 71.24% and 37.22%,and the unit energy consumption of shaft furnace is 9.16% higher than that of the rotary kiln and 40.50% lower than that of the flat kiln.④The effective measures for energy saving are recycling the waste heat of the flue gas from the furnace top,enhancing the heat transfer between the pellets and cooling air and increasing the thickness of furnace wall.

Technology Research on Vanadium Precipitation with Flue-gas Sulfuric Acid

Wu Zhenxiu, Sun Chaohui, Chen Wenlong, Du Guangchao

2014, 35(5): 17-20. doi: 10.7513/j.issn.1004-7638.2014.05.004

Abstract(27) PDF(0)

Abstract:
The exploratory experiments of precipitating vanadium which simulated the process conditions in a vanadium plant with the indexes of vanadium loss and cost were respectively tested with industrial sulfuric acid and flue-gas sulfuric acid in laboratory.The technology optimizations were studied by selecting the experimental group with the lowest vanadium loss and cost.The results indicate that the vanadium loss and cost are the lowest by one-step vanadium precipitation with flue-gas sulfuric acid,and the optimum processes are as follows:the pH of vanadium-containing solution is adjusted to 2.2 after adding the precipitation agent and the precipitation is proceeded 1 hour at 99℃ or 100℃.The vanadium loss and cost per 1 000 kg V₂O₃ are respectively 3.06 kg and 763.18 RMB yuan by the optimum processes,which are much less than the processes with industrial sulfuric acid.The new technology,which has been applied to industry,can wholly satisfy the production requirements with 0.31 g/L vanadium in the upper-liquor of precipitating vanadium process.Meanwhile,the purity,size distribution and bulk density of the final product V₂O₃ by the new technology are at the same level as those of the V₂O₃ by vanadium precipitation with industrial sulfuric acid.

Preparation of New Vanadium Based Solid Solution Hydrogen Storage Material by Ultrasonic Stirring Assisted Casting

He Chunshan

2014, 35(5): 21-24. doi: 10.7513/j.issn.1004-7638.2014.05.005

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In order to improve the properties of V-based solid solution hydrogen storage materials,ultrasonic stirring assisted casting method was used to prepare a new V-based solid solution hydrogen storage material V₃ TiNi_0.56Co_0.1Al_0.2.The phase compositions,microstructure,hydrogen absorption and desorption properties and corrosion resistance of the material were tested and analyzed.The results show that the new material consists of V-based solid solution phase,small amount of TiNi and Ti₂ Ni phases,and it has favorable hydrogen absorption and desorption properties and corrosion resistance,of which the maximum hydrogen absorption capacity at room temperature is 1.781% and the plateau pressure of hydrogen desorption at room temperature is 0.46 MPa,and the corrosion potential shifts positively by 709 mV in comparison to V₃ TiNi_0.56.

Microstructures and Properties of TC4 Alloy Bar with Different Heat Treatments

Huang Deming, Liang Shenglong, Tang Jing, Yang Xiongfei, Jiang Rengui

2014, 35(5): 25-30. doi: 10.7513/j.issn.1004-7638.2014.05.006

Abstract(35) PDF(2)

Abstract:
Microstructure and properties of TC4 alloy bars under various treatment processes were investigated.Results show that with increasing of single annealing temperature,the microstructure of TC4 alloy bar changes from equiaxed to bi-modal type and the tensile strength decreases while elongation and reduction of area first increase and then decrease,and the impact toughness increases continuously.With the increase of duplex annealing temperature,the microstructure of TC4 alloy bar changes from bi-modal to equiaxed type,of which the mechanical properties of the alloy with bi-modal microstructure are better.For the solution aging bar,the microstructure changes from basket-weave to bi-modal and equiaxed types,and the mechanical properties of the bar decrease with aging temperature increasing.The best comprehensive mechanics performances can be achieved under the heat treatment parameters of solution at 940℃ and aging at 530℃.

Research on Friction Stir Welding of New Type of Titanium Alloy

Duan Yali

2014, 35(5): 31-34. doi: 10.7513/j.issn.1004-7638.2014.05.007

Abstract(35) PDF(0)

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Single-side friction stir butt welding tests for automotive titanium alloy Ti-6Al-4V-0.2Y plate with thickness of 6 mm were conducted,and the macroscopic morphology,X-ray nondestructive flaw detection,microstructure,surface hardness and mechanical properties of the joints were tested and analyzed in this paper.The results show that the joints have good shapes,bright surfaces,favorable mechanical properties and no obvious defects;tensile strength of the joint at room temperature reaches 900 MPa and the joint coefficient is up to 96%;the area with maximum and minimum hardness of weld joint is located in the weld nugget zone and the heat-affected zone of forward side,respectively.

Research on Electrolytic Hydrogenation of Titanium Alloy for Automobile

Hou Shiyuan

2014, 35(5): 35-39. doi: 10.7513/j.issn.1004-7638.2014.05.008

Abstract(24) PDF(0)

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In order to improve the mechanical properties of the titanium alloy SP700(Ti-4.5Al-3V-2Mo-2Fe) used for automobile,the influences of faraday effect,charging time,additive and temperature on the hydrogenation of SP700 were investigated by electrolytic hydrogenation under acidic conditions (1N H₂SO₄).The results indicate that the most effective hydrogenation of SP700 exists after 12 h of charging time under conditions of shorter time and higher current density,with 0.1 g/L As₂O₃ in solution at 25℃.

Recovery of Ti from Titanium-bearing Blast Furnace Slag by Aluminum

Zhen Yulan, Zhang Guohua, Zhou Guozhi

2014, 35(5): 40-44. doi: 10.7513/j.issn.1004-7638.2014.05.009

Abstract(27) PDF(0)

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The recovery of Ti from titanium slag by alu minum was investigated.After smelting,Ti-Si-Al alloy and slag with high content of alumina were obtained.It is indicated from the experimental results that the recovery of Ti from titanium-bearing blast furnace slag by aluminum is technically feasible.The effective enrichment and separation can be achieved in a short time.The main factors affecting the smelting results are temperature,time,contents of reducing agent aluminum and flux CaO.The effective enrichment and separation can be achieved with w_slag:w_Al=100:25.98 at 1 600℃ for 10 min.At the same time,adding CaO is helpful to achieve the separation of the alloy and slag.

Effect of Li₂CO₃ on Hydration Capability of High Titanium Blast Furnace Slag after Extracting Titanium

Wang Peng, Han Bingqiang, Ke Changming, Li Nan

2014, 35(5): 45-50. doi: 10.7513/j.issn.1004-7638.2014.05.010

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The rapid cooling tailings produced in the process of silicon-titanium alloy extraction from high titanium blast furnace slags by plasma fusion technique were used as raw materials to prepare calcium aluminate cement.The chemically combined water content analysis,pore size distribution test,XRD and SEM were employed to investigate the effect of Li₂CO₃ on the hydration properties of the tailings.The results show that the rapid cooling tailings,mainly consisting of glass phase and also containing part of calcium aluminate (CA) and magnesia alumina spinel (MA) phases,have weak hydration ability;hydration of the tailings can be significantly promoted,and the mortar strength,porosity after hydration and bounding water in early hydration of the tailings are increased by adding not more than 0.1% Li₂CO₃.

Processes,Microstructure and Properties of Vanadium Microalloyed Steels

T N Baker

2014, 35(5): 51-64. doi: 10.7513/j.issn.1004-7638.2014.05.011

Abstract(27) PDF(0)

Abstract:
Vanadium as an important alloying element in steels was initially associated with the properties achieved following tempering.Interest in the microstructure was stimulated by the advent of transmission electron microscopes with a resolution of y1 nm together with selected area electron diffraction techniques.A second timely development was that of controlled rolling,particularly of plate and sheet products.The scope of this review will include the historical background on quenched and tempered vanadium steels,precipitation during isothermal aging,conventional controlled rolling and during thin slab direct charging and the development of strength and toughness in vanadium microalloyed steels.The characterisation of microstructure,in particular the methods for the analysis of the chemical composition of precipitates has progressed since the availability of X-ray energy dispersive analysis in the 1970 s,and the role played by electron energy loss spectroscopy in providing quantitative analysis of carbon and nitrogen in vanadium microalloyed steels will be presented.There are still many topics involving vanadium microalloyed steels that are controversial.These include the nucleation sequence of homogeneous precipitates of vanadium carbonitride and whether this occurs coherently,the composition of the vanadium precipitates,the nucleation mechanism for interphase precipitation,the importance of strain induced precipitation in austenite of vanadium carbonitride,the contributions of both interphase precipitation and random precipitation in ferrite to the yield strength,and the role of the process route parameters in developing properties.These topics will be considered in this paper which concentrates on hot rolled vanadium microalloyed steels placed in the context of pertinent research on other alloys.

Dephosphorization during the Process of Vanadium Extraction from Vanadium-bearing Hot Metal Based on the Coexistence Theory of Slag Structure

Song Wenchen, Li Hong, Wang Yannan

2014, 35(5): 65-71. doi: 10.7513/j.issn.1004-7638.2014.05.012

Abstract(17) PDF(0)

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The activity model of vanadium slag was established according to the coexistence theory of slag structure,based on which the influence of CaO addition on the dephosphorization of liquid iron containing vanadium during the process of producing vanadium slag was conducted in this paper.The equilibrium experiments between the hot metal and the molten slag were designed to validate the proposed model.In the comparison of the calculated value with the measured value,it was found that the calculated value of vanadium and phosphorus distribution ratio (L_V and L_P) between slag and melt agreed well with that of the measured value when the binary basicity was low(R<1).And the relationship D_V=72.43+0.79 D_Pwas obtain through regression analysis.The model calculation results indicated that both L_V and L_P increased with the increase of the binary basicity,and the effect on LPis more obviously.The increase of temperature will reduce L_V,however,it can increase L_P when the binary basicity was low(R<1).With the increase of binary basicity,the activity and activity coefficient ratio of FeO and Mn O increased and that of SiO₂ and TiO₂ decreased.

Study on Liquid Phase Generation of Vanadium-titanium Sinter with Moderate Titanium Content

Liu Ran, Liu Chaoqing, Lü Qing, Liu Xiaojie, Qie Yana, Li Chao

2014, 35(5): 72-77. doi: 10.7513/j.issn.1004-7638.2014.05.013

Abstract(18) PDF(0)

Abstract:
The factors influencing liquid phase generation of vanadium titanium-sinter with moderate titanium content had been investigated by sintering cup test combining with thermodynamic calculations and sinter microstructure observations.The results show that increasing alkalinity promotes Fe₂O₃ reaction with CaO leading to calcium ferrite formation and thus increase the amount of liquid phase,ie,improve the quality of sinter.With the increase of carbon content,the heat generated during sintering process would increase and then benefit to the generation of liquid silicate.As TiO₂ content increases,TiO₂ will take preferential reaction with CaO,which promotes perovskite generation and inhibit generation of calcium ferrite with better performance.The resulting perovskite dispersed between the slag phase and iron minerals weakens the bonding of silicate and crystal stock effect of hematite and magnetite containing titanium,and thus cause the reduction in liquid amount of sinter.

Influence of the Ratios of Limonite on Properties of Vanadium-titanium Sinter

Lü Qing, Liu Donghui, Zou Leilei, Chen Shujun

2014, 35(5): 78-82. doi: 10.7513/j.issn.1004-7638.2014.05.014

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The influence of the ratios of limonite on properties of vanadium-titanium sinter was investigated in this paper.The results show that the tumbler index and RDI_+3.15 of vanadium-titanium sinter increases first and then decreases with the increase of the ratio of limonite.The RI and T_10% of vanadium-titanium sinter decreases with the increase of the ratio of limonite.The ΔT of vanadium-titanium sinter decreases first and then increases with ratio of limonite increasing.With regards to comprehensive utilization of low-priced materials,reducing production cost and improving the quality of vanadium-titanium sinter,the influence of the ratio of limonite on the properties of vanadium-titanium sinter has been analyzed,which generates the best sintering ore-blending schemewhere the ratio of limonite is 10% and the total ratio of limonite is 37.2%.

Practice of Vanadium Titano-magnetite High Coal Injection Ratio Blast Furnace Process under Low Grade Condition

Du Sihong, Huang Bin, Ceng Huafeng

2014, 35(5): 83-87. doi: 10.7513/j.issn.1004-7638.2014.05.015

Abstract(22) PDF(0)

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The burden components and smelting practice with high PCI rate under low grade vanadium titano-magnetite at No.1 blast furnace of Ironmaking Plant of Panzhihua Steel and Vanadium Co.,Ltd had been discussed in the paper.For the purpose of increasing PCI rate and decreasing coke rate,some measures like adding pulverized coal combustion supporting agent,double pulverized coal injection guns,increasing the rate of high volatile bituminous coal of pulverized coal,increasing blast temperature and improving the particle size of pulverized coal as well were taken in order to improve the combustion performance of pulverized coal.Furthermore,some other measures,for example,increasing the blast kinetic energy,increasing the theoretical combustion temperature,increasing ore platform width to stabilize gas flow,reducing the temperature fluctuation range of blast furnace,maintaining suitable slagging system,were used at blast furnace to improve the combustion performance of pulverized coal and increase PCI rate.In the burden grade of 49.35% iron in the first quarter of 2014,the PCI rate was 154.29 kg/t,coke rate decreased to 421 kg/t.In the burden grade of 49.32% iron in 2014 April,the PCI rate reached 164.47 kg/t,coke rate decreased to 417 kg/t.

Study on Catalytic Reduction Kinetics of Micro-fine Lean Hematite by Thermal Analysis Method

Wang Tianming, Guo Peimin, Pang Jianming, Wang Lei, Zhao Pei

2014, 35(5): 88-92. doi: 10.7513/j.issn.1004-7638.2014.05.016

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The non-isothermal kinetics study is implemented on micro fine lean hematite to investigate the rate-determining system of chemical reaction and the effect of alkali salt on the reduction process.The results show that the reduction process is decided by the interface reaction and catalyzed by alkali salt which lowers the reaction of activation energy.Both alkali-metal salt and compound alkali metal salt have the capability to accelerate the reduction process.The stronger the metallicity of cationic is,the weaker the electronegativity and the stability of halogen will be.Besides,the activation energy will abate more at high temperature and the catalyst will perform better.If the stability of compound salt lessens,the catalytic effect will be stronger.Therefore,as addition of the catalyst increases,the reaction rate will increase and the activation energy at high temperature will decrease,which will promote the reduction process.

Production of Iron Nuggets Using Limonite by Direct Reduction

Chen Weipeng, He Chao, Zhao Zengwu, Wu Wenfei

2014, 35(5): 93-97,109. doi: 10.7513/j.issn.1004-7638.2014.05.017

Abstract(15) PDF(0)

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Using limonite and anthracite mined in Baotou region as main raw materials to manufacture pellets containing carbon which is used to produce iron nugget by direct reduction technique.The impacts of n_C/n_O,particle size,temperature and heating time on the reduction and melting has been investigated.The analysis of experimental results was carried out.The results showed that temperature and holding time strongly influenced the direct reduction and melting process.When the pellets with n_C/n_O=1.1,limonite and anthracite particle size less than 0.048 mm (320 mesh) was held at 1 370℃ for 5 min,slag and iron nuggets could be separated well,and the reduction rate of product was high.The separated slag can be readily pulverized.The iron nuggets can be used as a kind of steelmaking feed.

Study on Softening Melting Properties of BF Primary Slag and Medium-term Slag

Zhang Fang, An Shengli, Luo Guoping, Wang Yici

2014, 35(5): 98-102. doi: 10.7513/j.issn.1004-7638.2014.05.018

Abstract(14) PDF(0)

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Considering this fact that the slag skull on copper cooling stave is unstability and scales off frequently due to the worsen material condition and the increased combustion intensity of blast furnace (BF) ironmaking,the softening melting properties of BF primary slag and medium-term slag of had been studied based on the particularity of the compsitions of BF slag of Baotou Steel and Iron Company,and the work was implemented by means of test and phase diagram analysis.The results show that the weakly acidic BF slag is most unstable while w_(FeO) is 15%.Meanwhile the influence of basicity on the stability of BF slag is more significant than that of FeO,and K₂O is also more remarkable than FeO.Furthermore,the softening melting temperature will derease by 20℃ while w_(K₂O) increases per 0.5%,but the content of calcium fluoride increasing from 1.47% to 2.67% can not strongly affect the softening melting properties of BF slag.

Effect of Two Pairs of Electromagnetic Stirrer in Secondary Cooling Zone on Slab Equiaxed Crystal Ratio and Hot-rolled Plate Microstructure of Non-oriented Silicon Steel

Wan Yong, Wu Shaojie, Chen Weiqing

2014, 35(5): 103-109. doi: 10.7513/j.issn.1004-7638.2014.05.019

Abstract(27) PDF(4)

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Based on electromagnetic force calculation and industrial test,slab equiaxed crystal ratio and hot-rolled plate microstructure of 50W800 non-oriented silicon steel under different stirring parameters and combination modes of two pairs of electromagnetic stirrer in secondary cooling zone were studied.The results show that when the two pairs of stirring parameters are consistent and being 380A/6Hz,the equiaxed crystal ratio of slab is the highest and 23.48%.When the two pairs of stirring parameters are inconsistent,the equiaxed crystal ratio of slab is the highest and 25.42% with the first stirring parameters being 380A/6Hz and the second stirring parameters being 350A/3Hz.With the increase of slab equiaxed crystal ratio,the surface recrystallized grain size of hot-rolled plate increases gradually,the banded structure in the 1/4 thickness and center of hot-rolled plates decreases significantly,the number and size of recrystallized grains in the 1/4 thickness of hot-rolled plates increase.In combined consideration of increasing equiaxed crystal ratio and grain size of hot-rolled plates,decreasing banded structure of hotrolled plates and lowing power consumption,the first stirring parameters of being 380A/6Hz and the second stirring parameters being 350A/3Hz is the optimal combination mode of stirring parameters.

Influence of Elements Used as Inhibitor on Precipitation Behavior of the Inclusions and Hot Rolled Microstructure of Grain-oriented Silicon Steel

Zhou Bowen, Li Guangqiang, Zhu Chengyi, Zheng Jianxin, Fu Yong, Zhang Feng

2014, 35(5): 110-116. doi: 10.7513/j.issn.1004-7638.2014.05.020

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The influence of the molar ratio of Al to N and Mn to S on precipitation behavior of the inclusions and hot rolled microstructure of grain-oriented silicon steel has been studied in this paper.The results show that the inclusions in steel with different content of Al,N and Mn,S nucleate with Al₂O₃,where MnS and Al N grow surrounding Al₂O₃,and their size is less than 5 μm.The main precipitates in steel are complex inhibitors of MnS and Al N whose size is less than 0.5 μm.The number of precipitates is the most in the sample where the molar ratios of Al to N and Mn to S are 0.9 and 15.7 respectively,and its density are 5 937/mm³ in slab and 7 024/mm³ in hot roll plate.The average diameter of the resulting precipitates is smallest,which is 0.17 μm in slab and 0.15 μm in hot roll plate.The number of precipitates in hot roll plate increases when compared with that in slab,and the structure is the most uniform in edge and center of hot roll plate.

Effect of Quenching Temperature on Si-Mn Steel Microstructure and Mechanical Properties after Intercritical Insulation+Q＆P Process

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

2014, 35(5): 117-121. doi: 10.7513/j.issn.1004-7638.2014.05.021

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Low carbon Si-Mn steel was processed through intercritical insulation-quenching-partition,and effect of quenching temperature on microstructure and mechanical properties of Q&P steel was studied by means of field emission scanning electron microscopy,X-ray diffraction and tensile tests.The results show that quenching temperature at 220℃ generates the best comprehensive mechanical performance where tensile strength is 1 400 MPa,elongation is 13.3%,product of strength and elongation up to 18 620 MPa·%.With the increase of quenching temperature,the tensile strength of experimental steel decreases gradually,the ductility has increased,and lath martensite content reduce,carbide particles increase,there also has been a small amount of massive martensite structure.Intercritical Mn partition complements the lack of carbon partitioning during Q&P process which leads to final retained austenite at room temperature consisting ofa small amount of carbon-rich austenite and Mn-rich residual austenite with carbon partitioning.Quenching at 220℃ provides the experimental steel a good plasticity.

R＆D of BSG-110TT High Collapse Resistance Oil Casing

Wang Jun, Bi Zongyue, Zhang Feng, Wei Feng, Li Yuanzheng, Wang Liang, Lu Biwei

2014, 35(5): 122-128. doi: 10.7513/j.issn.1004-7638.2014.05.022

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High frequency welding,hot stretch reducing,full body heat treatment and high temperature straightening"process was adopted to produce BSG-110 TT high collapse resistance oil casing.The evolution of microstructure and property of casing steel at different process stage was analyzed.The mechanical properties and corrosion resistance properties of BSG-110 TT were also tested.The results show that the dimensional accuracy,residual stress and collapse resistance of BSG-110 TT are much better than high collapse resistance seamless oil casing tube.Moreover,the used production process benefits to solve the problems of low impact toughness and poor corrosion resistance of weld zone.

Investigation of High Strain and Low Cycle Fatigue Behaviors for HRB500E Rebars

Zheng Jialiang, Sheng Guangmin, Wang Lijuan, Zhang Dongsheng

2014, 35(5): 129-135. doi: 10.7513/j.issn.1004-7638.2014.05.023

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Based on the failure model of rebars under seismic loading,the high strain and low cycle fatigue (HSLCF) behaviors of HRB500E rebar were tested systematically under constant strain condition.The statistical processing of HSLCF life tested were carried out using a double parameters Weibull probability function,and the HSLCF life with different confidence degree and the cyclic toughness with 95% confidence degree were obtained.Finally,the HSLCF mechanism and the ways to improve the HSLCF propertise were discussed.

Formation and Modification of MgO·Al₂O₃ Spinel in Oil Casing Steel

Fang Zhongqiang, Sun Yanhui, Zhang Xichao, Wang Chengyi

2014, 35(5): 136-141. doi: 10.7513/j.issn.1004-7638.2014.05.024

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The formation and modification mechanism of MgO·Al₂O₃ spinel in oil casing steel during secondary refining process was studied by industrial experiments and thermodynamic calculations.The results show that when dissolved Al are 0.02% and 0.05% respectively,the required amount of dissolved Mg for the formation of MgO·Al₂O₃ spinel are 1.5×10^-6and 2.8×10^-6accordingly.For molten steel with 0.02% dissolved Al,When the dissolved Mg ranges from 4×10^-6to 8×10^-6,MgO·Al₂O₃ inclusions would transform into CaO-Al₂O₃-MgO system inclusions under dissolved Ca content of 0.21×10^-6and 0.42×10^-6 respectively.MgO·Al₂O₃ spinel inclusions could be easier modified than Al₂O₃ inclusions.Because of the influence of slag-metal reaction and calcium treatment,the evolution of inclusion could be roughly described as follows:Al₂O₃→MgO-Al₂O₃ system inclusions→CaO-Al₂O₃-MgO or CaO-Al₂O₃ system liquid complex inclusions.

2014, 35(5): 142-144.

Abstract(19) PDF(0)

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2014 Vol. 35, No. 5