钢铁钒钛

Theoretical and Thermal Simulation of Vanadium Extraction from Molten Iron in Combination Blowing Converter

Liu Zhibin, Zhang Xidong, Ma Deng, Zhao Bin, Wu Wei

2016, 37(2): 1-7. doi: 10.7513/j.issn.1004-7638.2016.02.001

Abstract(36) PDF(0)

Abstract:
Based on the ion and molecule coexistence theory,we calculated the activity coefficient of V₂O₃ in the vanadium removing slag V₂O₃-SiO₂-TiO₂-Cr₂O₃-MgO-MnO-FeO,the influence of vanadium composition、temperature on the activity coefficient of V₂O₃ has been investigated,the activity coefficient of V₂O₃ is between 0.5×10^-6 and 9.0×10^-6.Through studying the vanadium-carbon reaction equilibrium,the oxidation transformation temperature of vanadium and carbon is 1 380℃,which is the temperature control during blowing.The vanadium removal in combination blowing converter process was simulated by experiment in 500 kg intermediate frequency induction furnace with top and bottom blowing function,the experiment results shows:at the end point of blowing the average vanadium content in hot metal was 0.06%,vanadium oxidation rate was 95%.In addition,bottom blowing can accelerate vanadium oxidation,shorten 3 minutes oxygen supply time.

Effects of Heat Treatment Conditions on Precipitation Behavior of Perovskite in the Titanium-bearing Blast Furnace Slag

Zhang Shiqiu, Wang Weiqing, Yan Wu, Deng Jie, Huang Yang

2016, 37(2): 8-14. doi: 10.7513/j.issn.1004-7638.2016.02.002

Abstract(29) PDF(0)

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In order to achieve the effective recovery of titanium component in the titanium-blast furnace slag from Pangang Group Co.,Ltd.,the effect of different heat treatment conditions on selective precipitation behavior of perovskite as the enriched phase of titanium were studied in this paper.Through analyzing the chemical components and mineral compositions of the slag,the effects of Fe₂O₃ addition amount,crystallization temperature and period,and cooling rate on the enrichment of perovskite were explored using selective precipitation technology integrating phase diagram theories.It is shown that with 2.54% CaO added as regulator and pre-oxidation at 1 025℃ for 30 min,then with 1% Fe₂O₃ mixed and smelting at 1 470℃ for 60 min,and cooling to 1 320℃ at a speed of 0.5℃/min and insulation for 90 min,the modified slag having 30.62% of perovskite with 63.17 μm of crystal size can be finally obtained,which realizes the efficient enrichment of TiO₂ in titanium-bearing blast furnace slag and is beneficial to the separation of titanaugite and perovskite.

Regression Relation between the Achromic Ability of the Rutile Titanium White Pigment and the Influence Factors of Salt Treatment and Calcination

Liang Anbing, Tian Congxue, Chen Hua, Chen Zhirong

2016, 37(2): 15-20. doi: 10.7513/j.issn.1004-7638.2016.02.003

Abstract(49) PDF(2)

Abstract:
With metatitanic acid hydrolyzing from low concentration of industrial titanyl sulphate solution as raw material,the orthogonal mutual influences of the addition amount of salt treatment agents(zinc salt,potassium salt and phosphorus salt) and the highest calcination temperature were investigated by using four-factor quadric orthogonal regression test.The metatitanic acid was characterized by particle size measurement and XRD.The achromic abilities of the calcined samples were measured to establish effective regression model and forecast the quality of titanium dioxide pigment.The optimal conditions of salt treatment and calcination are 0.36% of ZnO,0.70% of K₂O and 0.20% of P₂O₅ with 850℃ of highest calcination temperature.The experimental results fit well with the predicted values.

Effect of Feed Rate on the Hydrolysis of Titanyl Sulfate Solutions with Low Titanium Concentration

Liu Cuicui, Liang Bin, Lü Li, Li Chun

2016, 37(2): 21-26. doi: 10.7513/j.issn.1004-7638.2016.02.004

Abstract(38) PDF(0)

Abstract:
The hydrolysis of titanyl sulfate solutions was investigated,mainly focusing on the influence of feed speed of titanium solution on hydrolysis rate,gray-turning point of solution,size of primary and secondary particles for hydrolysis.The results show that with decrease in feed rate the hydrolysis rate of titanium solution increases,since the dilution extent of initial titanyl sulfate solution is enhanced with longer duration by slow feed speed which results in more formed seed crystals.The gray-turning time for the solution is shortened with decrease of feed speed.The size of primary hydrolysis particles is affected by feed rate that a slower feed speed contributes to the formation of fine-uniform primary particles.The average particle size of hydrolysate from low-concentration of titanium solution is 1.69~1.78 μm.With decrease in feed speed,the size distribution of obtained hydrolysate becomes narrow,and the morphology of the hydrolysate gradually transforms from irregular-dense to spherical-loose particles.This research could provide guidance to further improvement for the production process of titanium solution hydrolysis.

Preparation of Ti(C,N) Composite Powder by Fractional Steps of Ball Milling and Carbon Thermal Reduction

He Pingji

2016, 37(2): 27-30. doi: 10.7513/j.issn.1004-7638.2016.02.005

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The Ti(C,N) composite powder was prepared by fractional steps of carbon thermal reduction after ball milling using ilmenite as raw material,and the particle size,morphology,phase composition and sintering performances of the obtained composite powder were tested and analyzed.The results show that the particle size of the Ti(C,N) composite powder composed of Ti(C,N) and α-Fe phases is 2~5 μm,with nearly normal distribution.The flexural strength of the sintered body of the as-prepared Ti(C,N) composite powder could reach to 98% of that for commercial Ti(C,N) powder.Meanwhile,the fracture toughness of the sintered body of the as-prepared Ti(C,N) composite powder could reach to 110% of that for commercial Ti(C,N) powder.

Process Mineralogy of Vanadium Titano-magnetite from Shanxi

Zhu Xiaobo, Li Wang, Sun Zhiyong

2016, 37(2): 31-36. doi: 10.7513/j.issn.1004-7638.2016.02.006

Abstract(19) PDF(0)

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The chemical composition,mineral composition,ore particle size and ore structure were deeply analyzed using a variety of detection methods to investigate the process mineralogy of a polymetallic mineral from Shanxi.It is shown that the polymetallic mineral mainly contains magnetite and ilmenite,as well as a small amount of pyrite and limonite.Vanadium and titanium mainly exist in magnetite and ilmenite,respectively.The simple ore fabric is beneficial for full dissociation of the mineral.The magnetite and ilmenite mainly exist in gaps of the gangue mineral grains in form of sparse impregnated-star status,and small amount of magnetite and ilmenite are wrapped in the gangue minerals,with few adhesions to pyrite and hematite.

Hot Deformation Behaviors and Processing Map of Pure Titanium TA1

Li Jun, Shi Qingnan, Yu Hui, Ren Wanbo

2016, 37(2): 37-43. doi: 10.7513/j.issn.1004-7638.2016.02.007

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The isothermal and iso-strain rate hot deformation for pure titanium TA1 was tested on Gleeble-3800 thermal simulator at 650~850℃ with strain rates of 1~20 s^-1 and deformation degree of 60%.The results show that the flow stress of the pure titanium decreases with increase in deforming temperature while increases with strain rate increasing.The constitutive equation of pure titanium was constructed by Arrhenius constitutive model,which can be used as the reference model for the numerical simulation of hot processing of pure titanium.The hot processing map for pure titanium was established according to the dynamic materials model,which is consistent with the experimental observations for the microstructure evolvement of pure titanium.The obtained results in this paper can provide technical base for establishing and optimizing of hot processing of pure titanium.

Simulation and Industrial Validation of Molten Pool Morphology and Solidification Structure of Pure Titanium during VAR Process

Xiao Cong

2016, 37(2): 44-49,83. doi: 10.7513/j.issn.1004-7638.2016.02.008

Abstract(26) PDF(1)

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Change rules of molten pool morphology and solidification structure of Ø980 mm pure titanium ingot during VAR process were studied by using ANSYS and μMatIc softwares.The simulation results show that the molten pool is very small with shallow U type at the arc starting stage,then gradually changes from U to V type.The depth and width of molten pool no longer change in the stable stage of smelting when the equilibrium between heat input and output in the crucible is attained.During the filling process,the molten pool gradually shrinks and disappears.The evolution of solidification structure is that fine crystal structure is formed from the liquid contacted with the crucible wall by rapid cooling,and a part of the fine crystals growing as arborization finally form into columnar crystals with a certain preferential orientation.In the center region of the ingot and the critical region of liquid-solid phase,nucleation and growth of crystals directly occur in the metal liquid,and the formed equiaxed crystals block the growth of columnar crystals coupled with transformation between equiaxed and columnar crystals.By anatomizing the industrial ingot,the simulation results of numerical model are with good accordance with the industrial tests.

Microstructure and Properties of the Vanadium Based Hydrogen Storage Battery Anode Material Modified with Graphene

Hu Yinquan, Wu Xiaobing, He Xiaohui

2016, 37(2): 50-54. doi: 10.7513/j.issn.1004-7638.2016.02.009

Abstract(35) PDF(0)

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The vanadium based hydrogen storage battery anode material modified with graphene was prepared by the method of sintering after ball milling,and the phase composition,microstructure,hydrogen absorption and desorption properties,and cycling stability of the anode material were tested and analyzed.The results show that the material is composed of vanadium-based solid solution as main phase,Ti Ni phase with three-dimensional network structure and graphene with diffuse distribution,having better hydrogen absorption and desorption properties and cycling stability.Compared with V₃TiNi_0.56 prepared by the same method,the maximum hydrogen adsorption of this material could increase by 16.4% with comparative hydrogen platform pressure and its decay rate of discharge capacity after 20 times of charge and discharge cycles could decrease from 92.8% to 6.7%.

Study on Microstructure and Photocatalytic Activity of TiO₂ with Surface Modification by SiO₂ and Al₂O₃

Lü Bo

2016, 37(2): 55-61. doi: 10.7513/j.issn.1004-7638.2016.02.010

Abstract(14) PDF(2)

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Sodium silicate and sodium metaaluminate were used for the inorganic surface modification of TiO₂ matrix to block the electron-hole produced by light irradiation on TiO₂,finally attempting to improve the weatherability and dispersity of TiO₂.The growth of membrane layer on the surface of TiO₂ particles was tested online by focused beam reflectance measurement(FBRM).The phase composition and micro/nano structure of TiO₂ before and after modification were characterized and analyzed by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),scanning electron microscope(SEM),transmission electron microscope(TEM) and specific surface area test(BET),respectively.The results show that a uniform and compact amorphous SiO₂ and stable boehmite colloid membrane layer have been formed on the surface of TiO₂ particles,which can fill the oxygen vacancies and make up the defects of photochemical activity for TiO₂.It is also indicated through the test of photodegradation that the photocatalytic activity of TiO₂ samples respectively with single silicon and silicon-aluminum binary modifications decrease with slower degradation rates,proving that TiO₂ has gotten effective protection.

Preparation of KVO₃ by Solventing-out Process

Wu Liuzhu

2016, 37(2): 62-65. doi: 10.7513/j.issn.1004-7638.2016.02.011

Abstract(8) PDF(2)

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Potassium metavanadate(KVO₃) was firstly prepared by solventing-out crystallization,and the proper acidity range for crystallization from high-vanadium solution was determined.The results show that KVO₃ owning purity more than 98% can be obtained with vanadium recovery rate more than 95%,under the conditions of 150 g/L vanadium concentration,7.6~8.5 solution pH,ethanol as precipitation agent with volume ratio of 1:1 to the vanadium solution,and stirring for 60 min.The recovery rate for crystallization is closely related to the volume ratio of precipitation agent,vanadium concentration of mother liquor and crystallization time.The chromium content in the obtained crystals increases with rise in vanadium concentration of mother liquor and is not affected by crystallization time.However,the silicon content in the crystals decreases with increase in crystallization time and not change with vanadium concentration in mother liquor.Moreover,the particle size of crystals can be controlled by addition amount of precipitation agent.

Development of 600 MPa High-strength Anti-seismic Rebars by Nitrogen-rich V-Cr Microalloyed Technology

Chen Wei, Wu Guangyao, Zhang Weiqiang, Chen Bisheng, Li Jinzhu

2016, 37(2): 66-72. doi: 10.7513/j.issn.1004-7638.2016.02.012

Abstract(8) PDF(0)

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In order to meet the needs of the upgrading development for construction steel,preparation of 600 MPa anti-seismic rebars by nitrogen-rich V-Cr microalloyed technology in domestic steel plant was carried out.The mechanical properties,fatigue performance,microstructure,precipitates and inclusions of the obtained rebars were tested and analyzed using tensile testing and material testing machines,metallographic microscopy,transmission electron microscopy and X-ray diffraction apparatus,respectively.The results show that the tested rebars feature favorable comprehensive properties with good strengthtoughness performance,anti-seismic properties,fatigue performance,high and low temperature tensile properties.The microstructure of the tested rebars are consisted of ferrite and pearlite(content 42%~48%),and the size of ferrite grains is greater than 10.5 grade with small and uniformly distributed particles.A large number of small and diffuse V(CN) precipitates sized 2~30 nm are formed and distributed on ferrite matrix,grain boundaries and dislocation lines,and the fraction of V(CN) precipitates is more than 70% to the total vanadium content.Meanwhile,there are a spot of small sized inclusions in the steel,which is helpful to improve the plasticity and toughness of the rebars.

Smelting Chromium Using Low Iron Chromium-containing Slag in Treatment of Vanadium Precipitation Wastewater with Low COD

Teng Xiaohui, Zhuang Lijun, Li Wenhui

2016, 37(2): 73-77. doi: 10.7513/j.issn.1004-7638.2016.02.013

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Vanadium precipitation wastewater was treated separately using supernatant of sodium thiosulfate solution and sodium metabisulfite,but COD of the wastewater reduced by the former was as high as 2 878 mg/L,far exceeding the emission standards.Wastewater with a lower COD and chromium-containing slag with low iron content can be obtained by sodium metabisulfite reduction,neutralization and precipitation for the vanadium precipitation wastewater.Industrial operating conditions for treatment of vanadium precipitation wastewater with sodium metabisulfite are proposed as follows:addition amount of sodium metabisulfite is 3.1~3.2 times as much as Cr⁶⁺ content in the wastewater,with 15~30 min of reduction time.Through ammonia removal for the wastewater after the treatment mentioned above,no hexavalent chromium is detected in the water discharged to the sewage treatment plant with 65 mg/L of average COD value,satisfying the emission limits of Liaoning province local standard "Integrated Wastewater Discharge Standard"(DB21/1627-2008).Meanwhile,slag with low iron content(0.27%,calculated as Fe₂O₃) and high content of chromium(41.6%,calculated as Cr₂O₃) can be obtained.After roasting the chromium-containing slag,qualified chromium JCr95(Cr ≥ 95%) can be produced by outfurnace smelting.

The Physical and Chemical Properties of Slag Wool by Direct Fibration of Blast Furnace Slag

Long Yue, Du Peipei, Zhang Liangjin, Li Zhihui, Zhang Yuzhu

2016, 37(2): 78-83. doi: 10.7513/j.issn.1004-7638.2016.02.014

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Slag wool was prepared in laboratory by four-roller centrifugation method using blast furnace slag with 1.25 of acidity coefficient as raw material.The microstructure,diameter,shot content and moisture,mineragraphy and crystallization temperature of the obtained slag wool were analyzed.The results show that the slag wool is solid cylindrical fiber with smooth surface,and its diameter,shot content and moisture is respectively 4.9 μm,3.76% and 0.73%,satisfying the international standard overall.Furthermore,the slag wool has a higher vitrification degree with about 882℃ of crystallization temperature and almost no crystallization except for a very small amount of calcium aluminum melilite(Ca[Al(AlSi)O₇]) and calcium magnesium melilite(Ca₂MgSi₂O₇).

Prospect of Researching and Developing Vanadium Functional Materials Using Vanadium Resources in Panxi Area

Yang Shaoli, Ma Lan, Liu Jinfeng, Lei Zhuojun

2016, 37(2): 84-91. doi: 10.7513/j.issn.1004-7638.2016.02.015

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The application of vanadium functional materials in non-steel fields,such as laser,catalyst,synthesis of chemical raw materials,coatings,architectural ornament,energy utilization and far infrared technology,etc.,has been gradually increasing.This paper has reviewed and summarized the preparation of vanadium functional materials including Nd:YVO₄ laser host crystal,nano-V₂O₅ catalyst,BiVO₄ photocatalyst,VO₂ thermosensitive thin film,V-Ti black porcelain infrared coating and vanadium battery,etc.The feasibility of using vanadium resources in Panxi area to prepare vanadium functional materials has been analyzed,and the development prospect of vanadium functional materials has been given.

Summary on Characteristics of Oxidation Reactor for Titanium Dioxide Production by Chloride Process

Wu You

2016, 37(2): 92-96. doi: 10.7513/j.issn.1004-7638.2016.02.016

Abstract(21) PDF(1)

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The technologies of oxidation process in the main foreign titanium dioxide manufacturers adopting chloride process,such as Dupont,Kronos,Tronox and Cristal Global were studied in this paper with emphasis on the structures of oxidation reactor and crusting removal technique.The results show that all the mentioned four large-scale companies adopt the similar charging methods that O₂ and TiCl₄ are preheated to maintain the smooth operation of gas phase oxidation,and the ektexine of burner is protected by forced cooling.So far,oxidation reactor with relatively small diameter is preferred for titanium dioxide production with chloride process by these large-scale manufacturers,and the methods including mechanical scraping,sand blasting,gas film protection or combined sand blasting and gas film are usually employed for the crusting removal on the oxidation reactor.

Experimental Study on High-phosphorus Hematite Gasification Dephosphorizing in Sintering Process

Fu Junkai, Zhang Wei, Xing Hongwei, Tian Tielei, Wang Hui, Liu Weixing

2016, 37(2): 97-101. doi: 10.7513/j.issn.1004-7638.2016.02.017

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The effects of various factors on high-phosphorus hematite gasification dephosphorizing in sintering process were studied through pellet sintering.The results show that gasification dephosphorizing is mainly a gas-solid phase reaction process.Under low oxidizing atmosphere,the rate of high-phosphorus hematite gasification dephosphorizing increases when the increasing reaction temperature,reducing the basicity and extending the holding time.When the the content of dephosphorization agent is 6.8%,the optimal gasification dephosphorizing process parameter are as follows:carbon content 4%,reaction temperature 1 250℃,basicity 1.2,reaction holding time 30 min,and the resulting gasification dephosphorization rate can reach 23.8%.XRD microscopic detection on the finally calcined product confirmed the occurrence of gasification dephosphorization reaction.

Influence of H₂ Content in Gas on Burden Reduction of Blast Furnace

Li Jianpeng, Li Fumin, La Xiaoshuai, Lü Qing, Qie Yana, Liu Xiaojie

2016, 37(2): 102-107. doi: 10.7513/j.issn.1004-7638.2016.02.018

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The influence of different H₂ content on reduction process of burden in blast furnace was investigated.The chemical compositions of the reduced burden were determined.The results show that the Fe aggregates obviously with the increasing of the H₂ content in the reducing gas.The weight loss rate,the reduction rate and the metallization rate of the burden increase with the increasing of the H₂ content.Because the H₂ content was increased the indirect reduction was improved,so the degree of direct reduction was decreased effectively.Although the metallization rate also increases with the H₂ content,much higher H₂ content will cause the reduction of non-ferrous metal and thus higher energy consumption.So H₂ content in the reducing gas should be controlled within a proper range of~15%.

Physical Simulation of Bubble Behavior in Liquid Steel Under the Condition of High Pressure and Bottom Blowing

Zhao Dingguo, Guo Fujian, Wang Shuhuan, Gao Aimin

2016, 37(2): 108-112. doi: 10.7513/j.issn.1004-7638.2016.02.019

Abstract(11) PDF(1)

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In order to explore the existence form and movement form of the gas in liquid metal under the condition of high pressure,a serial of water model experiments had been carried to obtain the effect of pressure and bottom flow rate on the shape,diameter,quantity of bubble and slag eye area.The experimental results indicate that compared with atmospherica pressure,when increasing bottom blowing flow rate,high pressure cause air bubbles generated tend to be much round,and the average bubble diameter decreases and the number of bubbles increases.When the bottom blowing flow rate is 4 L/h,the change of bubble diameter and shape is most remarkable.When at constant flow rate and bottom blowing position,with the increase of the pressure,the bubble shape gradually tend to round,air bubble diameter became smaller,the the number of bubble increase gradually, "slag eye" area gradually decreases.Under the condition of normal pressure and high pressure,when bottom blowing flow after excesses 5 L/h,the change of bubble diameter and shape is not obvious.When the bottom blowing flow rate is at 4 L/h and pressure is at 0.5 MPa,the change of average bubble diameter and shape is very small.This research result can provid reference for the development of high pressure metallurgy.

Effect of Orifice Spacing on the Impact Area of Molten Bath under Gas Jet Sprayed from Oxygen Lance

Tang Guozhang, Feng Shuai, Ceng Yanan, Li Junguo

2016, 37(2): 113-120. doi: 10.7513/j.issn.1004-7638.2016.02.020

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Based on the design and technology parameters of four-hole oxygen lance applied in an steelmaking workshop,influence of orifice spacing,lance level and syncretizing length on the impact area of molten bath under gas jet sprayed from non-variable angle and variable angle four-hole oxygen lance were simulated by Fluent software.It is showed that the impact area of molten bath under gas jet sprayed increase to the summit and then decline with the increasing of the lance level.From the view of effective impact area of molten bath,the lance level should be controlled within the lance height at which the maximum effective impact area can achieved.The influence of syncretizing length on the impact area of molten bath is significant,the impact area of oxygen jet to molten bath increase with the increasing syncretizing length and the drift distance of central line.The impact area of molten bath decline with the decrease of the orifice spacing.The fluctuation of flow speed increase with the increasing of orifice spacing,reducing the orifice spacing can make the speed stable quickly.The impact area of molten bath by variable angle oxygen lance are considerably larger than that by non-variable oxygen lance at the same lance level.

Effect of Nitrogen on the Vanadium Precipitation Behavior of Higher Yield Strength Weathering Steels

Liu Qingchun, Yong Qilong, Zheng Zhiwang

2016, 37(2): 121-124. doi: 10.7513/j.issn.1004-7638.2016.02.021

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The separate addition or combined addition of microalloy elements based on common weathering steel is usually applied in producing higher yield strength weathering steels.The target-oriented researches on the vanadium-containing weathering steels were conducted in this paper that combined with the advantage of vanadium resource at Panzhihua Iron & Steel(Group) Co..Methods such as Glbeele-3500 thermal simulated test machine,phase analyzing,and so on were used to investigate the vanadium precipitation amount-temperature-time(PTT) of test samples with different deformation degree and nitrogen content.The relationship between the amount of vanadium precipitates,temperature and precipitate time was analyzed.It has been found that the PTT curves of test samples with the same austenite amount are C curve shape,a shortest time of precipitation along with the vanadium precipitation process is also been found.Increase the nitrogen content will make PTT curve move to the left obviously.Additionally,increasing deformation degree can accelerate the rate of V(C,N) particle precipitation in the austenite,make PTT curve move to the left obviously.It has been also found that the more deformation degree,the shorter start time of the V(C,N) particle precipitation.The study offers the essential technical support for the further development of products.

Solidification Structure and Inclusions of Ti-containing FeCrAl Stainless Steel

Han Zhibiao, Liu Jianhua, He Yang

2016, 37(2): 125-132. doi: 10.7513/j.issn.1004-7638.2016.02.022

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The precipitation of TiN and AlN in FeCrAl stainless steel were calculated using Thermo-Calc software.The results indicated that the Ti content should be controlled around 0.08%.The ratios of central equiaxed grain in longitudinal and cross section firstly rise then decreased with Ti content.When Ti content was 0.088%,these two ratios reached maximum of 39.5% and 16%,respectively.Results of high temperature tensile indicated that the addition of Ti did not improve the high-temperature mechanical properties.SEM analysis indicated that there were mainly five kinds of Ti-containing inclusions,which were pure TiN,TiN(AlN) compound inclusion,TiN-Al₂O₃ compound inclusion,pure TiS and TiS(oxidation) compound inclusion.The former three types of inclusions were dominant while the latter two were very low in terms of their quantities.

Effect of Heating Temperature on the Growth of Austenite Grain of Titanium Microalloyed Steel

Luo Xu, Kang Yonglin, Li Junhong

2016, 37(2): 133-138. doi: 10.7513/j.issn.1004-7638.2016.02.023

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The Ti microalloyed steel was heated in an electric furnace up to the temperature ranging from 850℃ to 1 250℃ and heldfor 30 min.The behavior of austenite grain growth and the solid solution of Ti were investigated by observing the microstructure of austenite grain and the distribution of precipitates.The results indicate that the tested steel has two austenite grain coarsening temperatures,i.e.,1 050℃and 1 250℃,corresponding to the solution temperature of two types of Ti precipitates,however,they are lower than the values expected from solid solution product equation.It is found that the activate energy of grain growth decreases from 265.6 kJ/mol to 239.8 kJ/mol with the dissolving of TiC precipitates by analyzing two stages of the austenite grain growth process.

Analysis on Surface Upwarp Defects of Heat-resistant Stainless Steel Plate 310S

Li Yufeng, Liu Tianzeng, Li Hongliang, Li Jucang

2016, 37(2): 139-143. doi: 10.7513/j.issn.1004-7638.2016.02.024

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Surface upwarp defects of heat-resistant stainless steel plate 310 S were investigated by means of optical microscope(OM) and scan electron microscope(SEM).The results show that the main causes of surface upwarp defects are the protective slag entrapped in the process of casting and iron oxide pressed during hot rolling.The surface upwarp defects appears different morphology and distribution profile through the surface to the matrix.The oxide inclusions of chromium are found in the internal of defects,but oxide inclusions of iron and silicon are present on surface of defects.

Analysis on Tension Fracture Separation of the Steel Plate for Shipbuilding

Yang Huixian

2016, 37(2): 144-148. doi: 10.7513/j.issn.1004-7638.2016.02.025

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Morphology and microstructure of separated fracture were observed by metallurgical microscope and scanning electron microscopy.The results indicate that the inclusions,the center segregation and the banded structure are the causes of separated fracture on tensile sample of high strength ship plate.Combining with production practices,the forced cooling measures upon casting billet solidification end at secondary cooling zone were put forward,with which columnar grains growth can be slowed down and percentage of equiaxed crystal has been increased,and static pressure and central segregation reduce.Thus,the tension fracture separation of the shipbuilding steel plate was prevented remarkably.

Analysis of Pitting Defects of Magnesium Chromate Insulating Film on Non-oriented Silicon Steel

Wang Shuanghong, Zhao Shilu

2016, 37(2): 149-153. doi: 10.7513/j.issn.1004-7638.2016.02.026

Abstract(11) PDF(1)

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The magnesium chromate insulating coating of non-oriented silicon steel plate was prone to some pitting defects,which had affected surface quality and performance of the insulating coating.In this paper the morphology of the pitting defects coating and the components difference between the pitting defect location and normal location had been investigated by using SEM/EDS.The results showed that the pitting defects mainly occurred in the pit of the substrate,the contents of Cr,Mg and O at the pitting defect location were significantly higher than that at normal.The structure of pitting defect location was similar to the "volcano" or "crater" structure.At the cove,the coating dropped off seriously,the thickness of the coating decreased from the center to the surrounding with many cracks.Some solid particles suspended in the coating were main contributor to the pitting defects.The preferred raw paint materials,strict production process,and the installation of a vacuum filtration equipment were expected the effective measures to remove the pitting defects.

Cause and Improvement Measures of Common Lamination Defect of Steel Plate

Tian Yaqiang, Zhang Mingshan, Song Jinying, Chen Liansheng, Zheng Xiaoping

2016, 37(2): 154-158. doi: 10.7513/j.issn.1004-7638.2016.02.027

Abstract(17) PDF(1)

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Lamination defects are commonly present inside steel plate,and they have a serious impact on the comprehensive properties of steel plate,in particular to the Z direction.Microstructure observation and microanalysis of lamination defects are carried out by using OM、SEM and EDS.Causes of common steel plate lamination defect are analyzed.The results show that the main cause of lamination defect include banded structure,mould powder,sulfide,folding,abnormal structure etc.Therefore,countermeasures for the processes like control of casting temperature and cooling rate,optimizing the process related to the mould powder,calcium treatment,stabe rolling and avoiding feed roll stalling are proposed together with appropriate quenching process.

2016, 37(2): 159-160.

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2016 Vol. 37, No. 2