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Synthesis and Mechanism of LiV₃O₈ Material by Solid Phase Coordination

Liu Jin, Wang Li, Sun Ruimin, Shi Zhaozhong, Zhao Hui, Luo Jing

2020, 41(2): 1-5. doi: 10.7513/j.issn.1004-7638.2020.02.001

Abstract(219) PDF(3)

Abstract:
Layered lithium vanadium oxide LiV₃O₈ was synthesized by solid phase coordination method,and the reaction mechanism was studied by TG-DTA and XRD.The results show that LiV₃O₈ with a single phase can be obtained at 550 ℃ of heat treatment temperature for 24 h.The initial discharge capacity of the material reaches 180 mAh/g,showing better capacity storage performance.Using Coats-Redfern integral method and Anderson-Freeman differential method,the most probable mechanism of the synthesis process is random nucleation and subsequent growth,and the reaction equation and kinetics equation are derived.

Study on Alkali Fusion Process of V-Ti Magnetite Concentrate at Lower Temperature

Hou Yaobin, Hong Lukuo, Sun Caijiao, Ai Liqun

2020, 41(2): 6-13. doi: 10.7513/j.issn.1004-7638.2020.02.002

Abstract(245) PDF(5)

Abstract:
In order to realize the smelting of V-Ti magnetite concentrate at lower temperature,the direct reduction-smelting separation process was studied by coal-based direct reduction technique with NaOH as the alkali fusion agent.Effects of NaOH addition on metallization rate and smelting separation of V-Ti magnetite concentrate were investigated and the phase compositions of the metallized pellets and slag were observed by XRD.The melting points of slags of Na₂O-SiO₂-TiO₂-Al₂O₃-CaO with different Na/Si ratios were calculated by Factsage software.The results show that a higher Na/Si ratio corresponds to a lower melting point of the slag.NaOH can improve the direct reduction and smelting separation performance of V-Ti magnetite concentrate significantly.With increase in Na/Si ratio,the metallization ratio of pellets increases,but the increase amplitude decreases gradually.At a temperature of 1 150 ℃ for 30 min,Na/Si=5.0 and C/O=1.4,the metallization rate of metallized pellet can reach 93.17%.When Na/Si＞4.0,the granalated iron obtained by melting indicates that the flatness is good,and there is no small-sized gramular iron dispersed in the molten titaniam slag.Titanium,aluminum and silicon in the slag obtained by the method mainly exist as sodium salts.The addition of NaOH can realize smelting separation at lower temperatures and promote the separation between slag and metal.

Effects of Hydrolysis Conditions on High Purity TiO₂ Preparation from Industrial Low Concentration Titanyl Sulfate Solution

Tian Congxue

2020, 41(2): 14-19. doi: 10.7513/j.issn.1004-7638.2020.02.003

Abstract(353) PDF(14)

Abstract:
High purity TiO₂ was prepared via authigenic seed thermal hydrolysis route by using industrial low concentration titanyl sulfate solution as titanium source.The as-prepared metatitanic acid and TiO₂ powders were characterized by XRD,particle size distribution,BET analysis and TiO₂ content determination.The hydrolysis conditions had important influences on the hydrolysis process of low concentration titanyl sulfate solution.The appropriate amount of induced water and hydrolysis time were conducive to form appropriate quantity and quality of hydrolysis seeds,adjust and control the precipitation,crystal growth,particle growth and aggregation velocity of the hydrated titanium dioxide,which could obtain metatitanic acid with smaller average particle size and specific surface area.These effects were beneficial to reduce the adsorption of impurities and produce TiO₂ with high purity.And the hydrolysis conditions had internal influencing relationship between them.The optimized hydrolysis conditions were the induced water volume ratio of 60% and the hydrolysis time of 120 min,and the high purity TiO₂ over 99.97% content could be obtained.

Effects of Heating Rate on Pigment Properties of Rutile TiO₂

Chen Xinhong, Wang Rongkai, Li Li

2020, 41(2): 20-23,28. doi: 10.7513/j.issn.1004-7638.2020.02.004

Abstract(376) PDF(11)

Abstract:
Using industrial metatitanic acid as raw material,rutile TiO₂ was prepared via bleaching,washing,salt treatment and calcination.The effects of heating rate on the crystal structure and pigment properties of titanium dioxide particles were investigated.The samples were characterized by XRD,SEM,laser particle size analysis and pigment properties test.The results show that the heating rate has a significant effect on the phase transition,surface morphology,particle size and distribution,and pigment properties of the titanium dioxide particles.A faster heating rate can promote the phase transition and particle growth of titanium dioxide,but it causes sintering and leads to a larger particle size and a wider size distribution.At the optimum heating rate of 1.2 ℃/min,titanium dioxide having a particle size of 252 nm with the narrowest particle size distribution,a better sphericity and the best pigment performances can be obtained.

Effect of Slagging Agent on Quality of V-Al Alloy

Zhang Na, Li Lanjie, Zhang Suxin, Xu Feng, Wan Heli, Wang Haixu, Dai Baoshuang

2020, 41(2): 24-28. doi: 10.7513/j.issn.1004-7638.2020.02.005

Abstract(375) PDF(11)

Abstract:
The effects of types and addition amount of slagging agent on the recovery rate of vanadium（V） and qualification rate of products during vanadium aluminum alloy（V-Al alloy） preparation by electro-aluminothermic process were studied.The results show that during the selected agents of calcium vanadate,mixture of calcium fluoride and calcium oxide and single calcium fluoride,the calcium vanadate has the most significant influence on the vanadium recovery with 88.4% of V recovery rate,while the single calcium fluoride exhibits the minimum effect with 87.4% of V recovery rate.Adding 10% of the slagging agent,a maximum qualification rate of 86% for V-Al alloy can be obtained.The defects of V-Al alloy,such as oxidation film,solidification shrinkage cavity and crystal phase segregation can be reduced by the slagging agents,which is beneficial for improvement of the qualification rate of the products.

Analysis of Difference between Zinc Salt and Aluminum Salt Treated Titanium Dioxide

Wu Jianchun, Lu Ruifang, Ma Weiping

2020, 41(2): 29-32. doi: 10.7513/j.issn.1004-7638.2020.02.006

Abstract(282) PDF(10)

Abstract:
Using metatitanic acid from titanium white production by sulphate process as the raw material,the aluminum salt and zinc salt were used as salt treatment agents to treat the metatitanic acid,and initial product of titanium white was obtained after calcination.The difference of viscosity and zeta potential for the two kinds of titanium dioxide slurries was compared and analyzed,and the morphology and structure of the samples were characterized by SEM and XRD respectively.The results show that under the same concentration,pH and amount of dispersant,the slurry containing aluminum salt treated sample has a lower viscosity and better dispersibility.Zeta potential analysis shows that the aluminum salt treated sample has a higher absolute zeta potential than that of the zinc salt treated sample.XRD analysis shows that aluminum ions are doped into the lattice and replace part of the titanium ions in the aluminum salt treated titanium dioxide after calcination,leading to a change in its unit cell parameters and an increase in the cell volume.Meanwhile,the aluminum salt treated titanium dioxide has a more electronegative character due to the substitution of tetravalent titanium ions by trivalent aluminum ions,resulting in a better dispersibility.

High Temperature Mechanical Properties and Microstructure of TC4 Titanium Alloy Prepared by Selective Laser Melting

Song Jingwen, Fang Minhan, Hu Fuguo, Mao Jianwei

2020, 41(2): 33-37. doi: 10.7513/j.issn.1004-7638.2020.02.007

Abstract(1259) PDF(46)

Abstract:
In this paper,the mechanical properties and microstructure of TC4 titanium alloy,prepared by selective laser melting（SLM）,at room temperature（RT） to 550 ℃ were studied by universal tensile testing machine,optical microscopy,scanning electron microscopy,and transmission electron microscopy.The results show that the TC4 alloy produced by SLM consists of acicular α' martensite with a large number of grain boundaries,and the dislocation movement is limited to the interior of martensite during plastic deformation.Therefore,the experimental alloy has a high strength,with a tensile strength of 1 265 and 834 MPa at RT and 500 ℃ respectively,which is better than that of the TC4 alloy separately by solid solution aging treatment and anneal treatment.However,when it is deformed at temperatures above 500 ℃,martensite gradually transforms into equilibrium α phase,and the morphology changes from acicular to lamellar structure.The decrease in the number of grain boundaries leads to a decrease in deformation resistance,so the tensile strength decreases rapidly to 562 MPa at 550 ℃.

Preparation and Properties of Ti-ZrO₂ Bilayered Composites with Interfacial Doping Graphene

Xian Yong, Liu Wei, Chen Liming, Ding Yichao, Wang Jing, Liu Yao

2020, 41(2): 38-41. doi: 10.7513/j.issn.1004-7638.2020.02.008

Abstract(271) PDF(4)

Abstract:
Ti-ZrO₂ bilayered composite was synthesized by vacuum hot pressing sintering under 1 200 ℃ and 10 MPa through interfacial doping of graphene.The interfacial bonding was characterized by tensile strength.The interfacial phase compositions and element distributions were analyzed by X-ray diffraction（XRD）and scanning electron microscopy（SEM）,respectively.The results show that graphene could not exist stably on the interface,nor form titanium carbides.Instead,it dissolves into the lattices of titanium and zirconia,which hinders the mutual diffusion of titanium and zirconia,avoiding the formation of TiO₂ and ZrTiO₄.The interface is under the state of diffusion bonding with the strength reaching 52.1 MPa±3.8 MPa.

Effect of Mo₂C/WC Ratio on Microstructure and Properties of Cermet

Ma Yichuan, Zhang Xuefeng, Chen Min, Zhang Ning

2020, 41(2): 42-47. doi: 10.7513/j.issn.1004-7638.2020.02.009

Abstract(204) PDF(3)

Abstract:
Ti（C,N）-based cermets were prepared by powder metallurgy using TiC,TiN,Mo₂C,WC,Co and Ni as raw materials.The effects of Mo₂C/（WC+Mo₂C） ratio on the microstructure and mechanical properties of Ti（C,N）-based cermets were investigated by XRD,SEM and mechanical properties test.The results show that with the increase of Mo₂C/（WC+Mo₂C）,the hardness of Ti（C,N）-based cermets increases gradually,and the bending strength decreases first and then increases.At Mo₂C/（WC+Mo₂C）=0.8,the microstructure of Ti（C,N）-based cermets is refined significantly and the comprehensive mechanical properties are the best,with the Vickers hardness（HV） and bending strength reaching 1 411.15 and 1 053.7 MPa,respectively.

Diffusion and Control of Ti/Al Interface in Preparation of Ti/Al Alloy by Cold Rolling

Li Yaoping, Zhang Fuqin

2020, 41(2): 48-53. doi: 10.7513/j.issn.1004-7638.2020.02.010

Abstract(196) PDF(3)

Abstract:
The Al/Ti/Al sheet was prepared by cold rolling and it was annealed under different processes.The morphology of the Ti/Al interface before and after annealing was observed with a scanning electron microscope.The microhardness of the titanium layer was measured with a microhardness,and the growth rule of the Ti/Al interface during the annealing and rolling process was explored.The rules of interfacial growth show that the thickness of diffusion layer increases exponentially with the increase of annealing temperature.When the annealing time is less than 45 min,the thickness of the diffusion layer is not sensitive to the time.However,with the annealing time more than 45 min,the thickness of the diffusion layer increases sharply with the time.The microhardness results show that the rolled sheet could be basically annealed at 580 ℃ for 30 min.At the rolling reduction of 5% and annealing temperature of 580 ℃ for 30 min,the interface diffusion layer can be deformed with the rolling process with the thickness controlled at about 0.8 μm.

Preparation and Properties of Vanadium-titanium-nickel Based Hydrogen Storage Alloys for New Energy Automotive Batteries

Cui Xiajing, Shou Haofang, Su Yuefeng

2020, 41(2): 54-57,81. doi: 10.7513/j.issn.1004-7638.2020.02.011

Abstract(333) PDF(7)

Abstract:
V-25 Ti-10 Ni and V-25 Ti-10 Ni-0.5 Ce alloys for new energy automobile batteries were prepared by self-propagating method,and their microstructures,hydrogen absorption properties and corrosion resistance were tested,compared and analyzed.The results show that the grain of V-25 Ti-10 Ni-0.5 Ce alloy is finer than that of V-25 Ti-10 Ni alloy.In comparison with those of V-25 Ti-10 Ni alloy,the hydrogen absorption capacity of V-25 Ti-10 Ni-0.5 Ce alloy increases by 13.38% at 50 min of hydrogen absorption time,and the mass loss rate of V-25 Ti-10 Ni-0.5 Ce alloy decreases by 37.61% after 240 h of corrosion.Both of the hydrogen absorption and corrosion resistance of V-25 Ti-10 Ni-0.5 Ce alloy are improved.

Effect of Rolling Process on Microstructure and Properties of TC4 Titanium Alloy Plate

Ren Wanbo

2020, 41(2): 58-62. doi: 10.7513/j.issn.1004-7638.2020.02.012

Abstract(320) PDF(14)

Abstract:
In order to establish and optimize the rolling process of TC4 titanium alloy plate with moderate thickness and develop the TC4 titanium alloy plate with excellent comprehensive mechanical properties,the rolling industrial test of TC4 titanium alloy plate with moderate thickness was carried out in a company based on the characteristics of 4 300 mm hot rolling equipment.The effects of rolling temperature and pass deformation on microstructure and mechanical properties of the TC4 titanium alloy plate were studied.The results show that in the（α + β） two-phase region,the grain size of TC4 titanium alloy plate decreases continuously while the strength,plasticity and toughness of the plate gradually increase with decrease in the rolling temperature.As the pass deformation decreases,the microstructure of the surface and core of the plate trends to be more uniform,and the plasticity and toughness are significantly improved.After annealing（850 ℃×2 h,AC） treatment,the homogeneity of TC4 titanium alloy plate with moderate thickness can be improved obviously,realizing a well match during the strength,plasticity and toughness.

Photocatalytic Performance and Reaction Pathway of TiO₂ Composite Materials on Ammonia and Nitrogen Degradation in Water

Wang Yingwei, Li Yufei

2020, 41(2): 63-68. doi: 10.7513/j.issn.1004-7638.2020.02.013

Abstract(354) PDF(8)

Abstract:
The nano-TiO₂ composite photocatalysts,i.e.activated carbon supported TiO₂（TiO₂/AC）,Tween-80,Cu²⁺and Fe³⁺doped TiO₂,were separately prepared by sol-gel method,and the samples were characterized by X-ray powder diffraction（XRD） and ultraviolet-visible spectrometer（UV-VIS）.The photocatalytic performances of the modified TiO₂ materials were tested in ammonia and nitrogen solution under the irradiation of ultraviolet lamp,and the photocatalytic degradation pathways of the ammonia and nitrogen were also discussed.The results show that TiO₂ doped by Cu²⁺ or Fe³⁺ is mainly composed of anatase phase,with the average particle size of TiO₂ decreased.Obvious redshift of the absorption spectrum occurs for Cu²⁺ doped TiO₂,while it is unconspicuous for Fe³⁺ doped TiO₂.The order of photocatalytic degradation efficiency for ammonia and nitrogen by the materials（from high to low） is TiO₂/AC＞Fe³⁺/Tween-80/TiO₂ ＆ Cu²⁺/Tween-80/TiO₂＞Fe³⁺/TiO₂ ＆ Cu²⁺/TiO₂.Simultaneous doping of Cu²⁺ and Fe³⁺ can play a.synergistic effect on photocatalytic efficiency of TiO₂.The reaction pathways for photocatalytic oxidation of ammonia and nitrogen by the modified TiO₂ are basically similar to those of bio-oxidation process,with N₂ as the terminal product.

Mechanical Properties of High Titanium Heavy Slag Fiber-reinforced Concrete

Yang He, Liang Hezhi, Die Jian, Chen Wei, Wang Wei

2020, 41(2): 69-74. doi: 10.7513/j.issn.1004-7638.2020.02.014

Abstract(346) PDF(4)

Abstract:
Considering the three main factors of fiber content,water-binder ratio and fly ash content,20 sets of high titanium heavy slag fiber-reinforced concrete specimens were designed using orthogonal experiments.The effect of fiber content,water-binder ratio and other factors on mechanical properties of titanium heavy slag fiber reinforced concrete were studied by SEM.The test results show that the water-binder ratio has the greatest impact on the flexural and compressive strength of the high titanium heavy slag concrete.Basalt fiber can significantly increase the flexural strength of the high titanium heavy slag concrete,and plastic steel fiber can significantly improve the compressive strength of the concrete.When the water-binder ratio is 0.32,the basalt fiber content is 1 kg,and the fly ash content is 5%,the flexural strength of the high titanium heavy slag fiber concrete reaches 5.61 MPa,which is 10% higher than that of the high titanium heavy slag concrete without fiber.At the water-binder ratio of 0.34,the plastic steel fiber content of 2 kg,and the fly ash content of 5%,the compressive strength of the high titanium heavy slag concrete reaches 60.45 MPa,satisfying the C55 level specified in Concrete Structure Design Code（GB50010—2010）.

Preparation of Ordinary Portland Cement Clinker from Vanadium-titanium Magnetite Tailing

Yang Fei, Sun Xiaomin

2020, 41(2): 75-81. doi: 10.7513/j.issn.1004-7638.2020.02.015

Abstract(196) PDF(4)

Abstract:
To efficiently utilize the vanadium–titanium magnetite tailing in Chengde area,ordinary portland cement clinker was prepared by high temperature calcination using the tailing,limestone and quartz sand as raw materials.The evolution of phase compositions and microstructure of the cement clinker during calcination and curing was discussed,and the comprehensive physical properties of the cement were analyzed.The clinker having a better properties than 42.5 R ordinary portland cement can be prepared by calcination at 1 400 ℃ for 30 min with the ratio of vanadium-titanium magnetite tailing∶limestone∶quartz=20∶75∶5.The clinker obtained is mainly composed of C₃S,C₂S,C₃A,C₄AF and glass phases.The formations of C₃S and C₃A phases are promoted by increasing the calcination temperature and prolonging the calcination time.After hydration,needle and bar like ettringite,plate like calcium hydroxide and amorphous C-S-H are formed in the clinker.With extension of the hydration time,the content of C-S-H increases,improving the compactness and strength of the sample.An ordinary portland cement with better performances than 42.5 R grade in GB 175-2007 standard can be obtained by compounding the clinker prepared with 5% gypsum.

Experimental Study on Carbonization Resistance of Concrete Containing Iron Tailings

Sun Qiurong, Liu Lei

2020, 41(2): 82-88. doi: 10.7513/j.issn.1004-7638.2020.02.016

Abstract(226) PDF(3)

Abstract:
The carbonization resistance and mechanical properties of concrete containing iron tailings sand under carbonization environments were investigated in this paper.Three factors including water-binder ratio,iron tailings sand content and binder content were analyzed and discussed by orthogonal tests.The results indicate that that water-binder ratio and iron tailings sand content are the most important factors affecting carbonization resistance of the concrete.The concrete is easier carbonized with higher iron tailings sand content,while the concrete containing iron tailings sand with water-binder ratio of 0.4 has the best carbonization resistance.The microstructure shows that ettringite（AFt）and C-S-H gel grow and form dense structure during the hydration process,and AFt decomposes into calcite after carbonization resulting in a significant reduction in structural compactness.

Effect of NaOH on Direct Reduction of Vanadium Titano-magnetite

Wang Xufeng, Hong Lukuo, Sun Caijiao

2020, 41(2): 89-93. doi: 10.7513/j.issn.1004-7638.2020.02.017

Abstract(174) PDF(5)

Abstract:
In order to reduce the direct reduction temperatures of vanadium titano-magnetite and improve the metallization ratio of pellets,sodium-treatment was adopted to the direct reduction of vanadium titano-magnetite.The vanadium titano-magnetite was direct reduced with coal and NaOH,and the influences of C/O,temperature,time,Na/Si on direct reduction were studied,the chemical analysis and XRD were used to measure metallized pellets as well.The results show that NaOH can reduce the direct reduction temperature and improve the reducibility performance of vanadium titano-magnetite significantly.The metallization ratio of pellets reduced at 1 150 ℃ for 50 min without NaOH is only 79.87%;the metallization ratio of pellets reduced can reach 93.17% at 1 150 ℃ for 30 min with Na/Si=5.0.XRD analysis indicates that titanium,aluminum and silicon oxides have been changed into the sodium salt respectively in the metallized pellet.The addition of NaOH is favorable for the reduction of iron bearing minerals,and the energy consumption can be greatly reduced.

Influence of TiO₂ Content and Basicity Level on the Metallogenic Regularity of V-Ti Sinter

Lin Wenkang, Hu Peng

2020, 41(2): 94-100. doi: 10.7513/j.issn.1004-7638.2020.02.018

Abstract(179) PDF(4)

Abstract:
In order to investigate the influence of different TiO₂ content and basicity level on the technical and economic indexes of V-Ti sintering and the metallurgical properties of V-Ti sinter,so as to determine a better sintering and blast furnace material mixture,an experimental study was carried out to reduce the TiO₂ content of sinter and increase the basicity level of sinter.Experimental results show that with the decrease of TiO₂ content and the increase of basicity of V-Ti sinter,the technical indexes of sinter are improved significantly.When the content of TiO₂ in sinter decreases from 6.0% to 0.5% and the basicity level is increased from 2.0 to 2.5,the yield is increased by 5.21%,the drum strength is increased by 5.60%,and the utilization coefficient is increased by more than 25% compared with those of the reference period.

Deoxidation of Steel by Aluminum-magnesium Alloys and Inclusion Analysis

Gong Hongjun, Yang Xingdi, Li Long, Ge Wensun

2020, 41(2): 101-107. doi: 10.7513/j.issn.1004-7638.2020.02.019

Abstract(293) PDF(6)

Abstract:
In order to solve the common problem of Al₂O₃ inclusion modification in aluminum deoxidized steel,the deoxidation of steel by Al-Mg alloys was explored and practiced.Al-Mg deoxidation can achieve slightly better result than that of aluminum deoxidization.The oxygen activity after Al-Mg deoxidization is less than 10×10^-6,and the inclusion rating is less than 1.0.Compared with aluminum deoxidization,the numbers of inclusions larger than 30 μm and sulfide inclusions in Al-Mg deoxidized slab and sheet has been significantly reduced.The magnesium content in Al-Mg alloys increases from 5% to 7.5%,the inclusions in steel decreases significantly after deoxidization.The Al₂O₃-MgO and Al₂O₃-M_xO_y-MnS-CaS composite inclusions gradually form in the deoxidization process of Al-Mg alloys,and then float up to remove them,which reduces the damage of the aluminum-deoxidized strip-like Al₂O₃ inclusions,and the inclusions in steel become small.At the same time,the magnesium vapor bubble adsorbs inclusions during the floating process,then reduces the number of inclusions and clean liquid steel.

Effect of TiO₂ in Refining Slag on Inclusions in Ti-Ferritic Stainless Steel

Feng Xiaoxia, Wang Qi, Tan Bo, Wang Lijun, Zhou Guozhi

2020, 41(2): 108-113. doi: 10.7513/j.issn.1004-7638.2020.02.020

Abstract(201) PDF(7)

Abstract:
The effect of TiO₂ in the refining slag on the inclusions in Ti-containing stainless steel was investigated under laboratory conditions during Al deoxidation.The results indicate that the inclusions initial Al₂O₃ forms then change into MgO-Al₂O₃ type inclusions with the dimention of 4 μm when the top slag does not contain TiO₂.In the case of TiO₂-bearing slag,the inclusion composition is migrated firstly to the high TiO_x region,then to MgO-Al₂O₃ types.Finally,TiO₂-MgO-Al₂O₃ forms in average size of 2～3 μm.The inclusion size is decreased with the addition of TiO₂.And the presentence of TiO₂ in top slag can prevent the oxidation of Ti in molten steel by increasing the activity of TiO₂ in slag phase.Meanwhile,TiN precipitation is enhanced both in amount and size,which also lowers the Nb content around TiN.Thus,NbC participation becomes smaller then that participate in the sample refined by the slag without TiO₂.

Effect of Interaction Between Superheat Degree and Combined EMS on Dendritic Structure and Homogeneity of Heavy Rail Steel Bloom

Li Hongguang

2020, 41(2): 114-119. doi: 10.7513/j.issn.1004-7638.2020.02.021

Abstract(204) PDF(3)

Abstract:
In order to determine the effect of interaction between superheat degree and combined EMS on dendritic structure and C,Mn homogeneity of heavy rail steel bloom,comparing experiment for different superheat degrees were carried out based on the specific combined EMS process.The effects of superheat degrees on the solidifying process and dendritic structure of bloom was qualitative analyzed by numerical simulate;the actual effects of interaction between superheat degree and combined EMS on dendritic structure and C,Mn macro segregation of bloom were further analyzed.Based on the analysis results the technical process improving the homogeneity and intensity of heavy rail steel bloom has been proposed.

Morphology of Ti-Al Inclusions in Ultrapure Ferritic Stainless Steel

Zhang Yimin, Sun Yanhui, Bai Xuefeng, Chen Ruimei

2020, 41(2): 120-127. doi: 10.7513/j.issn.1004-7638.2020.02.022

Abstract(215) PDF(6)

Abstract:
In this paper,the Ti-Al inclusions in ultra-pure ferritic stainless steel were studied.The Ti-Al inclusions in steel were observed by two-dimensional metallographic method and three-dimensional anhydrous electrolysis.Tungsten filament and field emission scanning electron microscope were used to observethe morphology,and its elemental composition was analyzed by an energy spectrometer.The results show that various forms of alumina inclusions are formed in the ultra-pure ferritic stainless steel after Al deoxidation.These deoxidation products will affect the subsequent Ti alloying and form a Ti-Al composite with excessive local titanium content.The equilibrium curve of TiN inclusions and the Ti-Al equilibrium curve in ultrapure ferritic stainless steel were obtained by classical thermodynamic calculations.The calculations showed that the formation of TiN should be in an unfavorable state at the experimental temperature and elemental content,but due to the local enrichment of Ti and N elements,TiN formed during the deoxidation product indicating or solidification.

Effect of Heating Temperature on Microstructure and Mechanical Properties of Q235/Ti Composites Plates with Ni Interlayer

Peng Lin

2020, 41(2): 128-134. doi: 10.7513/j.issn.1004-7638.2020.02.023

Abstract(236) PDF(4)

Abstract:
In this paper,a comparative experiment was carried out to prepare titanium/steel rolled composite plates under different heating temperature conditions with Ni as intermediate layer.Scanning electron microscope,energy spectrometer,X-ray diffractometer and Instron universal tensile testing machines and other analytical methods were used to study the effects of heating temperature on the mechanical properties and microstructure of the composite sheets.The results show that when the heating temperature is 850～900 ℃,the shear strength of resulted composite plate increases with the increase of temperature,when the heating temperature is 900～950 ℃,the shear strength decreases with the increase of temperature.The highest shear strength is obtained at 900 ℃.When Ni is used as the intermediate layer,elements such as Fe and C can be effectively prevented from diffusing to the Ti side to form an intermetallic compound,the type of the interface compound does not change with temperature but the number of interfacial compound increases with increasing temperature.When the rolling temperature is 850 ℃,there are very few intermetallic compounds at the interface,and the corresponding shear strength is the lowest.When the rolling temperature is 900 ℃,the interfacial shear strength of the composite plate is the best,and the corresponding interface structure is more sufficient,the element diffusion and a small amount of intermetallic compounds.When the rolling temperature is 950 ℃,the intermetallic compound layer sharply thickens,TiNi₃ and pores increase sharply,thus seriously weakening the shear strength of the interface.

Roless of Ti in Cr12MoV Steel

Peng Pan, Luo Dengjie, He Yi, Liu Jinyun, Jin Yingrong

2020, 41(2): 135-141. doi: 10.7513/j.issn.1004-7638.2020.02.024

Abstract(226) PDF(5)

Abstract:
The effects of Ti on the formation of austenite and carbides during solidification and cooling in Cr12 MoV die steel were investigated by calculating the solubility products of carbides such as Ti,V,Mo and Cr in different temperature ranges.The results show that TiC can be precipitated only when Ti content in the Cr12 MoV steel exceeds 0.108 4%,and the precipitated TiC may become the nucleation core of austenite.TiC precipitates in austenite earlier than VC during the cooling after solidification,which may acts as the nucleation core of VC,causeing VC particles coarser,and making it difficult for VC particles to dissolve uniformly in austenite during the quenching process,thereby affecting precipitation hardening effect of VC after tempering.

Microstructure and Mechanical Properties of Fe-0.4C-2Mn-4Al System δ-TRIP Steel

Zhang Dongmei, Feng Yunli, Cao Kuo

2020, 41(2): 142-146. doi: 10.7513/j.issn.1004-7638.2020.02.025

Abstract(335) PDF(8)

Abstract:
The microstructure of Fe-0.4 C-2 Mn-4 Al experimental steel in as-cast and hot-rolled state was analyzed by SEM,XRD and EBSD.The mechanical properties of the experimental steel before and after rolling were studied.The results show that the TRIP steel contains a large amount of δ-ferrite in the microstructure before and after hot rolling,but the δ-ferrite morphology changes after hot rolling,and the fish bone shape is stretched into strips along the rolling direction.Shape,and the grain size has been refined.Consequently,the strength and elongation have been significantly improved,and the strong plastic product has reached 13.7 GPa·%.

Influence of Nb/Ti on Corrosion Resistance Properties of Low Chromium Ferritic Stainless Steels

Dang Jie, Zhou Peng, Shi Hongyuan

2020, 41(2): 147-150. doi: 10.7513/j.issn.1004-7638.2020.02.026

Abstract(215) PDF(6)

Abstract:
The corrosion resistance of low-chrome ferritic stainless 409 L,409 M,410 L,410 S were evaluated by the chemical immersion erosion test,electrochemical corrosion test and intergranular corrosion test,and morphology and component analysis of corrosion film on the tested stainless steels’ surface were studied by Scanning Electron Microscopy.Compared with type 410 stainless steels,the corrosion rate of type 409 stainless steels is obviously decreased by the addition of Nb and Ti.Due to the existence of inclusions containing Nb and Ti,for example TiS,Ti（CN）and Nb（CN）,the pitting corrosion and intergranular corrosion resistance performances of type 409 stainless steels are observed,but type 410 stainless steels is readily to produce the general corrosion.

Microstructure and Property of Vanadium Micro-alloyed Cold Rolling Dual Phase Steel

Yu Cansheng

2020, 41(2): 151-157. doi: 10.7513/j.issn.1004-7638.2020.02.027

Abstract(180) PDF(4)

Abstract:
The effect of coiling temperature after hot rolling and annealing temperature on the microstructure and properties of vanadium micro-alloy cold-rolled dual phase steels was studied in laboratory.Microstructure and property were compared between the as-hot rolled and after annealing strip,strength mechanism of microstructure with dual phase was also analyzed.The results showed that the best mechanical properties is obtained when the hot rolling uses a final rolling temperature of 900 ℃,a coiling temperature of 650 ℃,and continuous annealing uses an annealing temperature of 800 ℃ and an overaging temperature of 270 ℃.The results are as follows:the yield strength of the steel is 437 MPa,tensile strength is 815 MPa,elongation is 21.0%,n value is 0.191 2.The mean grain size of annealed sample is 11.5 grade,volume fraction of martensite is about 38%.Explore the influence of hot rolling and continue annealing process on the microstructure and properties,the production process were optimized.

Kinetics of Precipitation for AlN in Austenite of Grain-oriented Silicon Steel

Liu Lei, Qiao Jialong, Yin Sibo, Hu Jinwen, Xiang Li, Chou Shengtao

2020, 41(2): 158-162. doi: 10.7513/j.issn.1004-7638.2020.02.028

Abstract(214) PDF(8)

Abstract:
The kinetics of precipitation of AlN in austenite of oriented silicon steel was calculated by the theory of second phase precipitation.The results show that the critical nucleation sizes of AlN in austenite under different nucleation mechanisms are identical and the critical nucleation size increases with the increase of temperature.The critical nucleation energy of AlN at grain boundary is the smallest,the relative nucleation rate is the largest and the precipitation time is the shortest.Although the critical nucleation energy of homogeneous nucleation and dislocation nucleation is equal,the relative nucleation rate of homogeneous nucleation of AlN is 2～3 orders larger than that of dislocation nucleation,and the initial precipitation time of homogeneous nucleation is also shorter than that of dislocation nucleation.The main nucleation mechanism of AlN in austenite is controlled by grain boundary nucleation.

Precipitation Behaviors of Second Phase in Er-containing Stainless Steel Shielding Material

Zhao Yong, Liu Yunming, Gu Mingfei, Pan Qianfu, Wang Yurong, Wu Yu

2020, 41(2): 163-168. doi: 10.7513/j.issn.1004-7638.2020.02.029

Abstract(195) PDF(8)

Abstract:
The precipitation behaviors of the second phase in Er-containing stainless steel were investigated by means of optical microscope（OM） and scanning electron microscope（SEM）.The second phase in stainless steel is mainly Ni-Er system,there are two second phases with the same elements but showing obviously different content,and the molar fraction ratio of Ni and Er in the two second phases is 2∶1.Most of the second phases in stainless steel are rod-like and precipitate along the grain boundaries,their amounts increase linearly with increasing the Er content.When the mass fraction of Er increases from 1.62% to 7.45%,the area percentage of the second phase increases from 7.0% to 24.5%.The plasticity of the second phase is worse than that of the matrix,thus the two phases cannot deform synergistically.Consequently the external force causes the second phase to break and fracture,which leads to the initiation and development of micro-cracks.

As-cast Microstructure and Mechanical Properties of Fe-12Mn-8.5Al-0.8C Low Density Steel

Wang Yinghu

2020, 41(2): 169-174. doi: 10.7513/j.issn.1004-7638.2020.02.030

Abstract(307) PDF(5)

Abstract:
The as-cast structure and mechanical properties of Fe-12 Mn-8.5 Al-0.8 C low density steel were studied by means of optical microscopy（OM）,scanning electron microscopy（SEM）,energy dispersive spectrometer（EDS）,X-ray diffraction（XRD）.The results show that the as-cast structure is mainly composed of ferrite,austenite and κ-carbide.A small amount of massive κ-carbide precipitates along the grain boundaries of austenite and ferrite.Dendrite segregation can affect the mechanical properties of Fe-12 Mn-8.5 Al-0.8 C low density steel.The tensile strength,yield strength,elongation after fracture and impact toughness of the steel are 522 MPa,506 MPa,13% and 6.85 J,respectively.The density of Fe-12 Mn-8.5 Al-0.8 C steel is 7.0 g/cm³,which is 10% weight lighter than common cast steels.

2020 Vol. 41, No. 2