钢铁钒钛

Effects of Na₂MoO₄on the Properties of Negative Electrolyte of Vanadium Battery

CHEN Yong

2018, 39(3): 1-6. doi: 10.7513/j.issn.1004-7638.2018.03.001

Abstract(33) PDF(1)

Abstract:
Used as an additive for the negative electrolyte of vanadium battery,the effects of Na₂MoO₄ on electrochemical performances and stability of the electrolyte,and properties of the battery were studied. The results indicate that electrochemical activity of the negative electrolyte and diffusion coefficient of V（Ⅲ） species can be enhanced by adding Na₂MoO₄,with the charge transfer resistance decreased. The stability of negative electrolyte at low temperatures can not be affected when 0 ~1. 5% of Na₂MoO₄ is added. Compared with the battery without adding Na₂MoO₄,capacity and energy of the battery added 1. 0% of Na₂MoO₄ are increased to a certain extent. Especially,the discharge capacity and discharge energy at 120 mA/cm² for the battery with adding 1. 0% of Na₂MoO₄ are increased by 25. 59% and 21. 89%,respectively.

Preparation of Metallized Pellets from Panzhihua Titanium Concentrate by Pre-reduction

Wei Guangliang

2018, 39(3): 7-11. doi: 10.7513/j.issn.1004-7638.2018.03.002

Abstract(47) PDF(1)

Abstract:
Aiming at the problems of high power consumption and low production capacity of titanium slag produced by direct use of titanium concentrate in smelting titanium slag.A new process for preparing metallized pellets from Panzhihua titanium concentrate,"internal carbon containing titanium concentrate pressure ball,rotary hearth furnace pre-reduction",has been developed.It is found that the main factors affecting metallization rate are:reductant proportion,reduction temperature,residence time,cooling method,etc.Industrial test results show that: The metallization rate of pellets is up to 70%,with a maximum of 72.65%. The scanning electron microscope and phase structure analysis of shows that:The phase composition of titanium concentrate has changed obviously by carbon-thermal reduction,transformation from ilmenite phase to anosovite,iron and so on.

Research on Impurities Removal from Alkaline Solution Containing Vanadium and Chromium

JIANG Lin

2018, 39(3): 12-16. doi: 10.7513/j.issn.1004-7638.2018.03.003

Abstract(24) PDF(1)

Abstract:
Using the alkaline V-Cr solution obtained from sodium roasting of V-Cr slag as raw material,the contents of main elements like V and Cr,impurities such as Si and P in the solution were analyzed.The removal mechanisms of Si and P using aluminum salt in alkaline solution were discussed.The effects of Al₂(dosage,pH value,reaction temperature and time,and rest time on the removal efficiency of Si and P were studied.The results show that 98%of Si and 92%of P can be effectively removed from the V-Cr solution using aluminum salt at low basic conditions,which satisfies requirements for the subsequent vanadium precipitation.The optimum test conditions are as follows:Al∶Si（molar ratio）=1.2,pH=9.0,90℃of temperature,15 min of reaction time,and 1 h of aging time.The loss of V and Cr are less than 5%in the purification process.Moreover,V and Cr in the slag of impurities removal can be easily washed and recycled.Through precipitation of the purified liquor and subsequent calcination of the precipitate,powdered product containing more than 99%ofthe standard requirements of YB/T5304—2011,can be obtained with precipitation rate of vanadium over 98%.

Influence of Particle Size on the Optical Properties of Titanium Dioxide Pigment

Liu Yong, Luo Zhiqiang, Liu Chan

2018, 39(3): 17-20. doi: 10.7513/j.issn.1004-7638.2018.03.004

Abstract(64) PDF(5)

Abstract:
The influence of particle size ranging from 210 to 260 nm on the pigment properties and hiding power of rutile titanium dioxide was studied.Scanning electronic microscopy（SEM） was utilized to characterize the particle size and morphology of titanium dioxide. The experimental results show that the tinting strength（TCS） increases whereas the spectral characteristics（SCX） decreases gradually when the particle size of titanium dioxide increases from 216 to 259 nm. The increasing particle size causes the increase of brightness（Jasn） from 95.36 to 96.18. When the particle size is greater than 250 nm,Jasn almost keeps constant.The hiding power of ink film pigmented with titanium dioxide also increases with increasing the particle size,and the rising rate becomes slow gradually.The best optical properties can be obtained when the particle size is 250 ~260 nm with TCS over 2100 Ranolds,SCX between 3.5 and 3.8,Jasn more than 95.9 and hiding power over 78.9%.

Effects of Pre-adding Water on Structure of Metatitanic Acid

Chen Hua, Tian Congxue, Liu Haibo, Meng Junquan, Liu Huiling, Yang Dong, Zhu Yuxuan

2018, 39(3): 21-26. doi: 10.7513/j.issn.1004-7638.2018.03.005

Abstract(29) PDF(2)

Abstract:
Using low concentration of industrial titanyl sulfate solution as raw material,metatitanic acid was prepared via the self-seeded thermal hydrolysis sulfate process.The effects of pre-adding water on structure of metatitanic acid were investigated.The as-prepared samples were characterized by pigment properties test,particle size distribution measurement,XRD,TEM,HRTEM,Raman and IR.The results show that a balance is reached between the growth rate and formation rate of the crystal nucleus by pre-adding water to control the TiO₂ concentration at around 160 g/L in the system,and finally the consequential metatitanic acid with high anatase degree and quality can be obtained.The amount of pre-adding water affects the number,structure and activity of crystal nuclei and changes the combination ofand Ti⁴⁺,resulting in a decrease in the unit cell parameter c,a reduction in the integrity of the metatitanic acid particles,and the formation of discontinuous grid stripes on crystal plane（101）.The amount of pre-adding water also affects the bonding way of the anatase TiO₂and the vibration mode of the bond in metatitanic acid.The greater the intensity of the Raman peak of metatitanic acid,the more complete the crystal structure.

Current State and Prospect for Preparation of Magnéli Phase Titanium Oxides

Wang Yici, Zhang Bao

2018, 39(3): 27-32. doi: 10.7513/j.issn.1004-7638.2018.03.006

Abstract(69) PDF(7)

Abstract:
Magnéli phase is a series of titanium sub-oxides with the general formula of Ti_ⁿO_2ⁿ-1（4≤ⁿ≤10）,which have excellent conductivity and great significance for battery research.At present,the main method for preparing Magnéli phase titanium oxides is high temperature reduction of TiO₂ or its precursors.Such method is complicated and time-consuming. In this paper,the preparation methods for Magnéli phase titanium oxides using carbon as reductant were introduced,and the microwave heating technology was introduced into the preparation process.The method with carbon reduction and microwave heating not only shortens the preparation process,but also makes the Magnéli phase titanium oxides obtained have smaller particle size and more regular shape. Finally,the prospect for preparation methods of Magnéli phase is put forward,providing references for research and application of such titanium oxides.

Preparation and Properties of Ti/TiO₂/BGC Bioactive Composite

Xu Ying, He Shiyu, Wang Huanhuan, Kong Fanbei

2018, 39(3): 33-39. doi: 10.7513/j.issn.1004-7638.2018.03.007

Abstract(33) PDF(1)

Abstract:
Nano-TiO₂ layer was prepared by in-situ growth on pure titanium matrix via anodic oxidation method,then the bioactive glass coating（BGC） was clad on the nano-TiO₂ layer through sol-gel method.Employing SEM,XRD,scratch test and human body fluid simulation test,the morphology and phase,biological activity of the coating were studied and evaluated respectively.Furthermore,the effect of CaF₂ molar fraction on bonding force of the coating was also investigated.The results show that after introduction of nano-TiO₂ layer the contact angle of the titanium matrix surface decreases with the hydrophilic ability increased,resulting 27% of rise for the binding force between the coating and titanium matrix.The maximum binding force between the coating and titanium is determined at 64 N when the CaF₂ content is 4%.After soaking in the simulated body fluid for 7 days,abundant hydroxyapatite can be generated on the surface of Ti/TiO₂/BGC composite.

Effect of Silver Content on Microstructure and Mechanical Properties of Porous Titanium

Zhao Chaoyong, Zhang Xuefeng, Zhang Lei, Chen Min

2018, 39(3): 40-45. doi: 10.7513/j.issn.1004-7638.2018.03.008

Abstract(33) PDF(1)

Abstract:
Using antibacterial silver as the alloying element and ammonium bicarbonate as the pore-forming agent respectively,porous titanium-silver alloys（Ti-Ag alloys） with different silver contents were prepared by powder metallurgy method.The effects of silver content on microstructure and mechanical properties of the porous titanium were investigated by weighing,SEM-EDS,XRD and universal mechanical testing machine.The results show that the porosity of Ti-Ag alloy increases from 65. 18% to 68. 25% when adding 3% of silver,with both of the compressive strength and elastic modulus for porous Ti-Ag alloy increased.When the content of silver is further increased to 10%,the porosity of Ti-Ag alloy keeps at about 68%,and the compressive strength and elastic modulus change little.The addition of silver has no obvious effect on pore structure of the porous Ti-Ag alloy,and its phase composition is mainly α-Ti.Porous Ti-Ag alloy has good pore structure and mechanical properties,owning the potential as an antibacterial orthopedic implant material for cancellous bone defect repair.

TiO₂Quantum Dots Modified g-C₃N₄and Its Photocatalytic Decoloration Performance

Si Yujun, Li Minjiao, Xiong Zhongping, Zhang Shulin

2018, 39(3): 46-50. doi: 10.7513/j.issn.1004-7638.2018.03.009

Abstract(35) PDF(1)

Abstract:
To further promote the photocatalytic performance of g-C₃N₄,TiO₂ quantum dots were loaded on g-C₃N₄ by a pore impregnating method.The results show that the TiO₂ quantum dots modification significantly influences the XRD patterns,surface parameters,particle size distribution and the visible light adsorption of g-C₃N₄.Using Rhodamine B as a simulated pollutant,the photocatalytic activity of obtained TiO₂/g-C₃N₄ was evaluated under a simulative sunlight irradiation.It is indicated that all the composites with TiO₂ quantum dots modification exhibit higher photocatalytic performance than the pristine g-C₃N₄.When the mass ratio of TiO₂/g-C₃N₄ is 3%,the composite displays the highest photocatalytic activity.The trapping experiments show that ·O^2- is the main active free species for the photocatalytic decolorization reaction.

Effect of Preparation Method on Properties of TiNi Hydrogen Storage Electrode Alloy

Zheng Xin, Yang Yuling, Liu Ronghai

2018, 39(3): 51-54. doi: 10.7513/j.issn.1004-7638.2018.03.010

Abstract(11) PDF(1)

Abstract:
TiNi hydrogen storage electrode alloy was prepared respectively by four methods to improve its properties,and the cycling stability and electrochemical corrosion resistance of the alloys obtained were tested and analyzed.The results show that compared with the conventional induction melting,the vacuum induction melting,mechanical vibration assisted vacuum induction melting and ultrasonic vibration assisted vacuum induction melting can reduce the discharge capacity decay rate of the TiNi alloy separately by 34%,48% and 65%,and make the corrosion potential positively shift by 92,141 and 173 mV,respectively.The vacuum induction melting,mechanical vibration assisted vacuum induction melting and ultrasonic vibration assisted vacuum induction melting can help to improve the cycling stability and electrochemical corrosion resistance of the TiNi hydrogen storage electrode alloy,of which ultrasonic vibration assisted vacuum induction melting is the best and determined as the optimum preparation method for TiNi hydrogen storage electrode alloy.

Effect of Vanadium Content on Wear and Corrosion Resistance of Magnesium Alloy for Mechanical Shell

Zheng Shuqin, Zhang Xiaohong

2018, 39(3): 55-58. doi: 10.7513/j.issn.1004-7638.2018.03.011

Abstract(19) PDF(2)

Abstract:
The microstructure,wear and corrosion resistance of magnesium alloy shell with different vanadium content were tested and analyzed.The results show that with increasing vanadium content from 0 to 0.7% of the sample,the grains are refined,and the wear volume decreases firstly and then increases.Meanwhile,the corrosion potential of the sample shifts in positive direction first and then in negative direction,with both of the wear resistance and corrosion resistance increasing first and then decreasing. The optimized vanadium content is 0.5% for the magnesium alloy shell.

Effect of Friction Stir Processing on Properties of Titanium Alloy for Automobile

Zhao Fuli, Wang Yongjiang

2018, 39(3): 59-62. doi: 10.7513/j.issn.1004-7638.2018.03.012

Abstract(8) PDF(1)

Abstract:
The microstructure,mechanical properties and wear resistance of automotive titanium alloy at different friction stir processing parameters were studied.The results show that compared with those of titanium alloy before friction stir processing,the crystalline grains of the automobile titanium alloy after friction stir processing is finer and more uniform,and its tensile strength,yield strength increases,elongation after fracture decreases,with mechanical properties and wear resistance of the alloy improved.

Research on Gravity Separation of Anosovite from Ti-bearing Slag

Ji Su, He Qi, Li Qiuju, Zheng Shaobo

2018, 39(3): 63-68. doi: 10.7513/j.issn.1004-7638.2018.03.013

Abstract(24) PDF(2)

Abstract:
In this paper,the method of gravity separation by spiral chute was used to separate the anosovite phase from titanium-bearing slag,thereby realizing the selective separation of titanium components and laying the foundation for comprehensive utilization of the titanium resources.The titanium-bearing slag was ground to different particle size limits,and the monomer dissociation degree of anosovite phase was determined.According to the statistical results,when the upper limit of the particle size of titanium-bearing slag was 74 μm and 50 μm,the monomer disassociation degree of anosovite phase was relatively high,which was 77.76% and 82.18% respectively. A set of optimal gravity-separation experimental parameters was obtained through gravity separation.When the position of the wedge-shaped block was controlled at 3 cm from the inner edge of the chute,the number of chute laps was 5 and the ore concentration was determined at 35%,consequently,the grade of TiO₂ in the concentrate reached 67. 19%,the recovery rate of TiO₂ was 61.62% and the recovery rate of anosovite was 68.74%.

Adsorption Characteristics of Ti-bearing Blast Furnace Slag for Total Phosphorus in Water

Xu Rui, Liu Rong, Wang Guoxiang, Ji Lingchen, Xu Yifan, Ye Fei, Yang Ming

2018, 39(3): 69-74. doi: 10.7513/j.issn.1004-7638.2018.03.014

Abstract(10) PDF(1)

Abstract:
Using Ti-bearing blast furnace slag as the adsorbent for total phosphorus removal from waste water,the performances and mechanisms for total phosphorus adsorption of the slag were studied by combination of the kinetics equation and isothermal adsorption equation. The results show that the adsorption of total phosphorus by Ti-bearing blast furnace slag is consisted of surface adsorption and particle inner diffusion stages,and the process is more inclined to monolayer chemical adsorption.96% of total phosphorus in 100 mL(50 mg·L^-1 of KH₂PO₄ concentration) solution can be removed by 6.0 g Ti-bearing blast furnace slag with 40 ~60 mesh of particle size,at 20 ℃ for 60 min and p H = 8.

Microwave-absorbing Media Cooperative Treatment of PAHs in Coking Wastewater

Zhao Ying, Shi Yan, Zhao Xin, Kong Zheng, Feng Yingying

2018, 39(3): 75-79. doi: 10.7513/j.issn.1004-7638.2018.03.015

Abstract(7) PDF(1)

Abstract:
With polycyclic aromatic hydrocarbons（PAHs） in coking wastewater as research object,activated carbon,steel slag and silicon carbide as absorbing media,PAHs in the coking wastewater was qualitatively and quantificationally analyzed by ultrasonic extraction and high performance liquid chromatography.The influences of microwave temperature,heating time,various types and masses of activated carbon,steel slag and silicon carbide on removal efficiency of PAHs were studied.The experimental results show that the microwave temperature and heating time have a great effect on PAHs removal.The most efficient removal of PAHs with more than 55% of the average removal rate can be obtained at 60 ~90 ℃ of microwave temperature and 9 ~12 min of heating time.Meanwhile,the removal mechanisms of PAHs by absorbing media under microwave radiation were discussed,finding that the activated carbon and silicon carbide have better removal efficiency of PAHs than steel slag and the average removal rate of PAHs for all the absorbing media（activated carbon,silicon carbide and steel slag） is over 30%.Adaptive mass of the absorbing media is beneficial for PAHs removal.

Effect of MnO on the Fluidity and Thermodynamic Behavior s of Low Magnesium Titaniferous Slag

Chang Zhiyu, Zhang Jianliang, Jiao Kexin, Ning Xiaojun, Liu Zhengqiang

2018, 39(3): 80-85. doi: 10.7513/j.issn.1004-7638.2018.03.016

Abstract(16) PDF(1)

Abstract:
In order to analyze the effect of MnO on viscosity of slags under the conditions of titanium ore retaining furnace and manganese ore washing furnace,the low magnesium titaniferous slags had been used as basic slag system.The relationship between MnO content and slags viscosity,melting temperature,activity and so on under different temperatures were studied through experiments and Factsage calculations,respectively.The results show that viscosity,initial melting temperature and complete melting temperature decrease with the increase of MnO content under the experimental conditions.When the content of MnO is more than 1.5%,its effect of reducing viscosity of slags is weakened.In the process of slags cooling,the melilite is the main precipitated phase and the first precipitation from slags.Increasing MnO content helps to increase the fraction of liquid phase and inhibit the formation of phase having a relatively high melting point,thereby improving slags fluidity.At the same time,the enthalpy of slags increases with the increase of MnO content.The fraction of solid phase and specific heat capacity as well as the structure of liquid slags are the main factors affecting the enthalpy changing.In addition,the activity of MnO and TiO₂ in liquid slags showed the opposite trend with the increase of MnO content.The increase of MnO activity and the decrease of TiO₂ activity further reflect that MnO can simplify the structure of the slags.

Influence of Atmosphere Condition on Iron Sheet Gas-solid Decarburization Process

Liu Xinliang, Ai Liqun, Gao Jianxin, Li Yaqiang, Chen Pengfei, Li Qiang

2018, 39(3): 86-93. doi: 10.7513/j.issn.1004-7638.2018.03.017

Abstract(19) PDF(1)

Abstract:
The study of gas-solid reactions is performed in order to investigate the impact of weak oxidizing atmosphere Ar-H₂O-H₂ on the 1 mm thick 4. 25% C iron-carbon alloy sheet. A serious of orthogonal experiments have been performed to investigate the influence of bath temperature,initial H₂ content and gas flow on the decarburization of iron-carbon alloy ribbon.It is found out that the significance of gas flow,initial H₂ content and bath temperature on decarburization sequentially decrease.When gas flow rate is in range of 200 ~500 mL·min^-1,increasing flow rate can significantly improve the decarburization result.When water bath temperature exceeds 333 K,oxidation of iron takes place,and dense layer of Fe O appears when water bath temperature exceeds 343 K.Suitable parameters for the decarburization at 1 413 K are flowrate 500 mL·min^-1,15% H₂,bath temperature 333 K.

Study on Properties of Fluxed Pellets Based on Fractal Theory

Xing Hongwei, Liu Zhenchao, Cai Shuang, Tian Tielei, Zhang Huiqi, Zhang Yuzhu, Ren Chengran

2018, 39(3): 94-99. doi: 10.7513/j.issn.1004-7638.2018.03.018

Abstract(5) PDF(1)

Abstract:
To investigate the pore structure of the fluxed pellets and the effect of basicity on the properties of the fluxed pellets,based on the mercury theory intrusion and the fractal theory,the multifractal spectrum fitting curve of the pore size distribution of the pellets was obtained by numerical simulation and analysis of the pellet image.The results show that the compressive strength of the fluxed pellets is approximately quadratic function of basicity.When the basicity is 1.0,the compressive strength of the fluxed pellets is the highest value of 3 753 N. The pore size distribution gradually changed from homogenization to nonuniformity with the increaseing of basicity and reaches the optimum size when R is 1.0.

Study on the Dephosphorization Agent for Secondary Dephosphorization of Semi-steel without Vanadium

Huang Bo, Sun Yanhui, Zhao Zhichao, Bai Xuefeng, Chen Lian

2018, 39(3): 100-106. doi: 10.7513/j.issn.1004-7638.2018.03.019

Abstract(19) PDF(1)

Abstract:
Based on a vanadium extraction converter,the semi-steel secondary dephosphorization process had been investigated,in order to improve the dephosphorization process without affecting the production schedule,thus reducing the dephosphorization pressure of the converter and decreasing the phosphorus content at the end point so as to produce the ultra-low phosphorus level in steel.The appropriate temperature,the reaction time and the addition of dephosphorizing agent which are used when the vanadium-extracted semi-steel is dephosphorized in the laboratory tube furnace are obtained by laboratory study.Based on these findings,CaO-Fe₂O₃-CaF₂ series,CaO-Fe₂O₃-CaF₂-Al2O3 series,Na₂CO₃-CaO-Fe₂O₃-CaF₂ series and BaO-CaO-Fe₂O₃-CaF₂ series dephosphorization agents are studied to find out their best matching ratio.Then the dephosphsrization process of vanadium-extracted semi-steel outside the furnace has been designed and validated by field test.

Theoretical and Experimental Study on Dephosphorization and Carbon Conservation

Shen Chang, Chang Lizhong, Wang Kaizhong, Zhang Ping, Zhu Zhenghai, He Fei, Zhou Li

2018, 39(3): 107-112. doi: 10.7513/j.issn.1004-7638.2018.03.020

Abstract(11) PDF(1)

Abstract:
Based on the ion and molecule coexistence theory,the calculating model of action concentration for CaO-MgO-FeO-SiO₂-P₂O₅ slag was established. Based on this,the influence of slag compositions on the Gibbs free energy of decarburization and dephosphorization was analyzed,the feasibility of dephosphorization and protection carbon was proved.On the basis of thermodynamic analysis,the high temperature thermal experiment was conducted and the result showed that when the slag basicity is about 5 and the（FeO） content is between 10% and 20% with the condition that initial carbon content is 0.5% and the phosphorus content is 0.032 5%,the dephosphorization rate is up to 75%,the carbon conservation rate is between 50% and 70%.

Research on Non-metallic Inclusion Behavior of Q195 Rectangular Billet

Wen Juwen, Zhu Liguang, Sun Ligen, Tian Kuo, Xu Jinzhong

2018, 39(3): 113-117,122. doi: 10.7513/j.issn.1004-7638.2018.03.021

Abstract(13) PDF(1)

Abstract:
Q195 steel is mainly used for strip production.In order to reduce the cost,the LF refining process is removed on the basis of the original process 80 t converter→argon blowing→LF→continuous casting.In order to ensure the slab quality does not affect the product performance,the composition and source of the non-metallic inclusions in the slab are analyzed by tracer method,metallographic,oxygen and nitrogen test,large sample electrolysis and scanning electron.After argon blowing[O]in the steel is up to 226×10^-6,[N]is 33×10^-6;For different heats,[O]in the tail billet is up to 251×10^-6,and[N]is 37×10^-6.The contents of micro-inclusions and large inclusions are high,and-MnO composite inclusions and-CaO composite inclusions are present in the slab.Therefore,a stable casting process is necessary,and the tundish structure shall be modified to improve the flow field to prevent slag entraping,hhile protection pouring shall be strengthen to reduce the occurrence of secondary oxidation.

Evolution Behavior of Inclusion in DP590 Steel during LF Refining Process and Continuous Casting Process

Zhao Maoguo, Xiao Pengcheng, Zhu Liguang, Tang Guozhang

2018, 39(3): 118-122. doi: 10.7513/j.issn.1004-7638.2018.03.022

Abstract(9) PDF(3)

Abstract:
This study on the evolution behavior of the the Non-metallic inclusion in the steel was conducted systematically by the means of the oxygen and nitrogen analysis,microscopic inclusion statistics and SEMEDS energy spectrum.The CaS-CaO-Al₂O₃ tenary phase diagram in 1 600 ℃ was calculated and plotted by Factsage software.The evolution behavior of inclusions was analysed in the CaS-CaO-Al₂O₃ tenary phase diagram.It can be found that,under the current technological conditions,The total oxygen content and number of non-metallic inclusion in the molten steel has been decreased by the LF calcium wire-feeding treatment process.From the end of metal tapping to the tundish of caster,the total oxygen content has been decreased by 27×10^-6.The number of non-metallic inclusion has been decreased by 54.5%.The content of the total oxygen and nitrogen and the number of the non-metallic inclusion in the steady billet is low.The main components of microscopic inclusion is Al₂O₃ before the calcium treatment in the LF.There are a great number of the globular CaO-Al₂O₃ inclusion observed in the sample after the calcium treatment,in the LF and in the Tundish and slab.This research results indicates that calcium treatment achieves good results and the objective of the modifing alumina inclusion has been achieved.The thermodynamic calculation results show that the evolution behavior of inclusion is as follows:Al₂O₃→Al₂O₃+CaO·6 Al₂O₃+CaS→Al₂O₃+CaO· 2Al₂O₃+CaS（higher CaS and less CaO）→Al₂O₃+CaO· 2Al₂O₃+CaS（less CaS,higher CaO）.

Evaluation of Effects of Inclusions Modification in Steel by Different Calcium Treatment Routes

Fang Zhongqiang, Sun Yanhui, Wen Bang, Zhu Wei, Wang Zhen, He Wen

2018, 39(3): 123-128. doi: 10.7513/j.issn.1004-7638.2018.03.023

Abstract(12) PDF(1)

Abstract:
To investigate effects of inclusions modification in steel,the morphology and composition distribution of inclusions in liquid steel from tundish,and composition changes of molten steel in the production of oil casing steel by BOF→LF→RH→CC flow of three different calcium treatment routes were observed.It is found out that the composition changes of molten steel,and the morphology and composition distribution of inclusions in liquid steel from tundish has significant difference due to different calcium treatment routes.In order to select the optimum route,the effects of calcium treatment are evaluated by modification index of inclusions,and the advantages and disadvantages of different calcium treatment routes are considered.

Development of High Strength Weathering Steel Q450 NQR1 Containing Vanadium

Wang Chuangwei

2018, 39(3): 129-133. doi: 10.7513/j.issn.1004-7638.2018.03.024

Abstract(25) PDF(1)

Abstract:
The high strength weathering steel Q450 NQR1 contaning vanadium was developed through TMCP process. Laboratory test results indicate that the microstructure of plate is ferrite-pearlite and grain size rating is ASTM No. 12,the yield strength,tensile strength,yielding-to-tensile ratio and specific elongation are 493.57 MPa,599.00 MPa,0.823 9,30.21%,respectively. The impact absorbing energy at -80℃ and -40 ℃ are 51.6 J and about 92 ~97 J,respectively. The corrosion rate for 72 hours and 144 hours are 44.47% and 34.06% compared with the Q345 B,respectively. The developed steel can meet the requirement for the railway boxcar.

Influence of Cooling Rate and Austenite Grain Size on Nucleation of Ferrite

Wu Zhe, Zhang Caijun, Chen Jin, Liu Yi

2018, 39(3): 134-138. doi: 10.7513/j.issn.1004-7638.2018.03.025

Abstract(15) PDF(2)

Abstract:
In this paper,influence of cooling rate and austenite grain on intragranular ferrite in non quenched and tempered medium carbon steel had been investigated by using high temperature quenching and high temperature phase change machine confocal microscope.Furthermore,the nucleation and growth of intragranular ferrite had been studied in order to provide the basis for smelting clean steel.Experimental results show that the cooling rate of 0.1 ℃/s can produce optimal equiaxial ferrite and the cooling rate affects the transformation temperature of ferrite.600 s holding time at quenching temperature can generate small size of austenite which is more suitable for ferrite nucleation at grain boundaries.

Effect of Finishing Rolling Temperature on the Microstructure and Mechanical Properties of Low Si-Mn-Nb Hot Rolled Dual-phase Steel Strip

Li Qiuhe, Wang Gang, Ying Chuantao, Fu Qingcai, Li Jiangwei

2018, 39(3): 139-143. doi: 10.7513/j.issn.1004-7638.2018.03.026

Abstract(15) PDF(1)

Abstract:
The effect of finishing rolling temperature on the microstructure and mechanical properties of Si-Mn-Nb hot-rolled dual-phase steel were investigated by using TEM,SEM technology and optical microscopy.The results showed that with finishing rolling temperature decreasing,the size of ferrite grains decreased and the size differences increased,the volume fraction of martensite decreased and the volume fraction of bainite increased.When the finishing temperature was 860 ℃,the microstructure of strengthening phase was mainly martensite,the tensile strength was higher and the yield ratio was lower,the second phase was mainly composed of Nb（C,N） and its size was larger.When the finishing temperature was 743℃,the microstructure of strengthening phase was mainly bainite,the yield strength was higher and the plasticity was good,the second phase was mainly composed of Nb（Ti） CN carbonitride compound and its size was smaller. Comprehensive analysis shows that the different proportions of the strengthening phase and the second phase of different components was obtained through reasonable control of the final rolling temperature,thus the controlling of mechanical properties can be obtained as well.

Microstructure and Mechanical Properties of Medium Carbon Martensitic Steel after Warm Rolling at Different Temperatures

Liu Tianyu, Feng Yunli, Xue Ruifeng

2018, 39(3): 144-148,157. doi: 10.7513/j.issn.1004-7638.2018.03.027

Abstract(9) PDF(1)

Abstract:
The effects of rolling temperature on microstructure transformation and mechanical properties of medium carbon martensitic steel were investigated by means of SEM,EBSD and tensile tests. The results show that when sample are subject to 80% deformation,with the rolling temperature increased from 500 ℃to 600 ℃,ferrite grain size increased from 0.51 μm to 0.78 μm,the carbide particle size increased from 40 nm to 200 nm,and the effect of temperature on the carbide particle size was significantly higher than that of ferrite.When the rolling temperature is increased from 500 ℃ to 600 ℃,the tensile strength decreased from 1 029 MPa to 909 MPa,and the total elongation increased slightly.The tensile strength ratio of the experimental steel was between 0.963 9 and 0.983 2 after warm rolling.

Effect of Carbon Content on the Center Segregation and Banded Structure of the 600 MPa Grade High Strength Steel

Liang Wen, Wu Run, Huang Hai'e, Xia Nianping, Wang Lixin, Hu Jun, Zhao Jiangtao

2018, 39(3): 149-157. doi: 10.7513/j.issn.1004-7638.2018.03.028

Abstract(18) PDF(1)

Abstract:
The center segregation and banded structure of the tested steels with three different carbon contents were investigated by original position analyzer for metal,direct reading spectrometer,optical microscope and electron probe microanalyzer. The results showed that the center segregation in the slab was highly associated with the banded structure in the finished product. The distribution of the center segregation in the cross section is uneven,where 1/4 width of slab shows the greatest segregation,the center is the next,and the edge hasthe slightest level. The carbon,phosphorus,sulfur,niobium and titanium element in the steel seriously segregate in the slab and with the increase of carbon content the segregation becomes worse. The distribution of the banded structure in the cross section is also uneven. The existing standard for inspecting banded structure have certain limitations for the gradation of the banded structure.

Cause of Contact Fatigue Damage on U75 V 60 kg/m Rail

XU Cong

2018, 39(3): 158-164. doi: 10.7513/j.issn.1004-7638.2018.03.029

Abstract(34) PDF(1)

Abstract:
Aiming at the defect inspection alarming of U75 V60 kg/m rail in small radius curve section of heavy-haul railway,the tests of macroscopic appearance,non-metallic inclusion grade,macrostructure and microstructure examination of the alarmed rail were carried out and the results were analyzed. The analysis results show that the rail was in good condition after 400 million tons passage. The defect of the tested rail is contact fatigue crack,which is related to the rail operating conditions of and the railway line operation conditions. The defect is independent of the rail quality.

Micro-analysis on Oxide Scale of U75 V Hot Rolled Rail

Chen Chongmu

2018, 39(3): 165-168. doi: 10.7513/j.issn.1004-7638.2018.03.030

Abstract(15) PDF(1)

Abstract:
The surface morphology,section morphology,thickness and microstructure of oxide scale on the surface of U75 V hot rolled rail were observed by optical microscope,scanning electron microscope and energy spectrum.The causes for the difference of thickness and morphology of oxide scale on rail and strip surface were analyzed.The study shows that the scale has a typical three layer structure of FeO,Fe₃O₄ and Fe₂O₃ oxides from inside to outside,the concentration of Si elements exists at the interface between the inner layer and the matrix.The average thickness of oxide scale of rail is over 50 μm,the thickness of underside is bigger than upside.The difference of thickness and morphology of oxide scale on rail and strip surface is mainly related to the section shape and the production process.

2018 Vol. 39, No. 3