钢铁钒钛

Thermodynamic Study on Sulfuric Acid Leaching for Vanadium Extraction from V-bearing Steel Slag

Zhang Hao, Ye Guohua, Lu Lu, Zuo Qi, Chen Ziyang, Xie Yu

2020, 41(1): 1-6. doi: 10.7513/j.issn.1004-7638.2020.01.001

Abstract(22) PDF(1)

Abstract:
Thermodynamic problem is the core issue of the sulfuric acid leaching reactions of vanadium bearing steel slag.According to the mineral compositions in vanadium bearing steel slag,thermodynamic calculation and analysis of the steel slag leaching system were carried out in this paper.The results show that,tricalcium silicate can react with sulfuric acid easily as a result of low and high equilibrium constant of acid dissolution reactions of tricalcium silicate at room temperature.Therefore,much of sulfuric acid will certainly be consumed due to the high content of tricalcium silicate in the steel slag.FeO can be fully leached by sulfuric acid in theory while vanadium cannot be leached at the terminal acid concentration（leaching equilibrium acid concentration） of 10^-4 mol/L,which indicates that the thermodynamic trend of FeO leaching is greater than that of vanadium leaching.Based on this result,a new leaching method of "selective stage leaching" can be designed,and a better selective leaching separation between vanadium and iron can be achieved significantly with pre-leaching of impurities in the first stage and leaching vanadium in the second stage.Eh-pH diagram shows that VO²⁺,VO²⁺,and V³⁺ are the main dissolved phases of vanadium in the acidic media,and the stable region of VO²⁺ is very large and just in the middle of the three dissolved phases.Thus in the leaching process,the vanadium should be controlled in the stable region of VO²⁺.

Influence of Si on the Electrolyte Properties of Vanadium Redox Flow Battery

Chen Yong, Peng Sui, Han Huiguo, Liu Bo

2020, 41(1): 7-12,17. doi: 10.7513/j.issn.1004-7638.2020.01.002

Abstract(23) PDF(1)

Abstract:
The effects of Si on the electrochemical performance and battery performance of the positive electrolyte of vanadium redox flow battery（VRFB） were studied by cyclic voltammetry,electrochemical impedance spectrum and charge-discharge test.The results indicate that with the content of Si in the electrolyte at 0.03 g/L,the diffusion coefficients of V（IV） species are decreased from（1.43～2.32）×10^-6 cm²/s to（1.23～1.99）×10^-6 cm²/s,and the value of electron transfer resistance is increased from 1.188 Ω·cm² to 1.593 Ω·cm²,resulting in the decrease in both of the electrochemical activity and the reversibility of V（IV）/V（V） reaction of the electrolyte.Meanwhile,the decay rates of capacity and energy of the battery are increased significantly,with the average coulombic efficiency and the average energy efficiency decreased by 1.39% and 3.23%,respectively.

Analysis of Factors Affecting the Whiteness of Titanium Dioxide

Wu Jianchun, Lu Ruifang, Liu Chan, Wang Haibo

2020, 41(1): 13-17. doi: 10.7513/j.issn.1004-7638.2020.01.003

Abstract(28) PDF(4)

Abstract:
Taking the original and final titanium dioxide products from a titanium dioxide factory in 2019 as the object,the influences of iron content and rutile TiO₂ content on the whiteness of the product were statistically analyzed.On this basis,samples of different whiteness with similar iron content and rutile TiO₂ content were selected to analyze the particle size distribution by a laser particle size analyzer and SEM,respectively.The results show that the whiteness of the product decreases with increase of the iron content,and a significant decrease of the whiteness can be found with the iron content exceeding 50 ppm.At 97% to 100% of the rutile TiO₂ content,the whiteness of the product shows a slight decrease with increase of the rutile TiO₂ content.With the increase of the product’s laser particle size D₅₀,the whiteness of the product shows a downward trend,and a higher whiteness can be obtained with D₅₀ less than 300 nm.At 200～300 nm of the average particle size by SEM,the product’s whiteness decreases with increase of the particle size,and the whiteness increases with increase of the ratio of particles of 150～350 nm.Hunter whiteness above 95 of the product can be obtained at the average particle size less than 240 nm and the proportion of particles of 150～350 nm above 75%.

Experimental Study on Fluidized Bed Oxidative Modification of Panzhihua Titanium Slag

Ye Endong

2020, 41(1): 18-23. doi: 10.7513/j.issn.1004-7638.2020.01.004

Abstract(20) PDF(1)

Abstract:
The parameters of fluidized oxidation of Panzhihua titanium slag were determined by TG-DSC and theoretical calculations,and the roasting experiments at different temperatures were carried out.Furthermore,the titanium slag after modification by fluidized oxidation was characterized by Raman,XRD and SEM,respectively.The results show that the titanium slag has a relatively uniform particle size distribution,which is suitable for roasting by fluidization.The transitions of the main Ti-containing phases,successively from titanium oxides of low-valence state to anatase titanium dioxide and finally to rutile,occur during the fluidized oxidation of the slag.The ferrous anosovite phase is transformed into rutile and brookite phases.The oxidation rate increases with increase of the temperature.In the process of strong oxidation,a large number of small pores and microcracks are produced in the solid solution of anosovite.At 850～1 100 ℃,more surface microcracks and internal small pores are formed at a higher oxidation temperature,with more destruction of the lattice of the anosovite solid solution.

Study on Preparation of CdS/TiO₂ Composite by Microemulsion and Its Photocatalytic Properties

You Jia, Jiang Huan, Han Yanlin, Zhong Yajie, Dong Zhihong, Zhang Liyuan

2020, 41(1): 24-31. doi: 10.7513/j.issn.1004-7638.2020.01.005

Abstract(21) PDF(2)

Abstract:
CdS/TiO₂ composite material was prepared by reverse-phase microemulsion method using cetyl trimethyl ammonium bromide（CTAB）,cyclohexane,n-butanol and water as main raw materials.The samples were characterized by field emission scanning electron microscopy（FESEM）,X-ray diffraction（XRD）,ultraviolet visible absorption spectrum（UV-Vis-Abs） and X-ray photoelectron spectroscopy（XPS）,respectively.The photocatalytic properties of the samples were studied with methyl orange as the target for degradation.The results show that cadmium sulfide has a significant effect on the surface morphology,crystalline composition,ultraviolet absorption band edge,element composition and chemical valence states of titanium dioxide.Compared with bare TiO₂,the photocatalytic activity of CdS/TiO₂ is significantly improved,and the sample of 3.3%CdS/TiO₂ presents the best photocatalytic performance with a degradation rate of 96.71% for methyl orange under irradiation of 450 W gold halogen lamps for 80 min.The absorption band edge of TiO₂ shows a certain blue shift after the compound.

Segregation of FeV80 Alloy by Electro-Aluminothermic Multi-Period Process

Yin Danfeng

2020, 41(1): 32-35. doi: 10.7513/j.issn.1004-7638.2020.01.006

Abstract(24) PDF(1)

Abstract:
The microstructure and elemental distributions of FeV80 alloy were studied by SEM-EDS and FactSage software.The results show that the FeV80 alloy consists of the light grey basic phase（σ phase） and dark gray granular or acicular secondary phase（BCC-A2 phase）.And silicon as the impurity tends to precipitate in σ phase.Based on the industrial experiments,the macrosegregation of FeV80 alloy was also studied.All the alloy elements have different degrees of segregation affected by the melting point,density and solidification of the elements.Casting is in favor of the homogeneity of elements,and reducing cooling rate simultaneously is necessary to improve the macrosegregation significantly,with the major element vanadium having the maximum range and standard deviation respectively at 1.510% and 0.4714%,and sulfur（impurity element） having the minimum range and standard deviation respectively at 0.004% and 0.0017%.

Preparation of Spherical Titanium Powder by RF Plasma and Its Application in Powder Injection Molding

Hu Kai, Zou Liming, Mao Xinhua, Liu Ruiyang, Hu Ke, Duan Bohua

2020, 41(1): 36-42,53. doi: 10.7513/j.issn.1004-7638.2020.01.007

Abstract(47) PDF(3)

Abstract:
The hydrogenated dehydrogenation（HDH） titanium powder with irregular morphology was spheroidized by RF plasma.The effects of carrier gas flow,powder feeding rate and sheath gas flow on the morphology and properties of titanium powder were studied.In addition,powder injection molding（MIM） experiments were carried out with raw HDH titanium powder and spheroidized HDH titanium powder as raw material respectively,and the microstructure,physical and chemical properties of the sintered samples were studied.The results show that the powder characteristics of spherical titanium powder prepared by RF plasma spheroidization technology are greatly improved compared with those of the HDH titanium powder.In the preparation process,the powder feeding rate,carrier gas flow rate,sheath gas flow rate and other factors have a great influence on the spheroidization of the powder.The MIM sample prepared from the spherical titanium powder has better performance than the MIM sample prepared from the HDH titanium powder.

Microstructure and Mechanical Properties of In-situ Synthesized TiB+TiC Reinforced Ti-Fe Matrix Composites

Shi Qi, Yan Zhiqiao, Liu Xin

2020, 41(1): 43-47. doi: 10.7513/j.issn.1004-7638.2020.01.008

Abstract(27) PDF(1)

Abstract:
Ti-Fe matrix composites were prepared by cold isostatic pressing（CIP）+ vacuum sintering using Ti,Fe and B₄C powders as the raw materials.The effects of the Fe content and volume fraction of the reinforcements on the microstructure and mechanical properties of the composite were discussed.The results show that the relative density of the composites reduces with increase of the Fe content and volume fraction of reinforcements at 1 150 ℃ to 1 250 ℃ of sintering temperature.The α lamellar structure is refined with increase in the Fe concentration.TiB whiskers and TiC particles can be in-situ synthesized as the reinforced phases with the addition of B₄C powder,and the microstructure of the matrix changes from lamellar to equiaxed structure.The mechanical properties of the composite increase with increase of the Fe content and the volume fraction of reinforcements.The composite of Ti-15%Fe-10%（TiB+TiC）having a micro-hardness of 334 HV and compression strength of 2 040 MPa can be obtained at 1 150 ℃ of sintering temperature.

Preparation of High Performance Battery-grade Cathode Material Lithium Iron Phosphate by Freeze-drying Method

Yi Dawei, Cui Xumei, Zhang Xuefeng, Liu Tiantian, Lin Danping, Xu Shanglin

2020, 41(1): 48-53. doi: 10.7513/j.issn.1004-7638.2020.01.009

Abstract(43) PDF(2)

Abstract:
Lithium iron phosphate powder as battery-grade cathode material was prepared by freeze-drying method respectively using LiOH·H₂O as lithium source,FeNO₃·9 H₂O as iron source,NH₄H₂PO₄ as phosphate source,citric acid as carbon source and chelating agent.The effects of sintering process on crystallinity and electrochemical properties of the carbon-coated lithium iron phosphate（LiFePO₄/C） cathode materials were investigated by XRD,charge-discharge test and cyclic voltammetry.The results show that the cathode material（LiFePO₄/C） sintered at 750 ℃ presents the best electrochemical performances,with a discharge specific capacity of 150.5,142.2,128.1,117.8 and 105.4 mAh/g at 0.1 C,0.2 C,1 C,2 C and 5 C,respectively.

Preparation and Properties of Vanadium-based Hydrogen Storage Alloy for V-Ti-Ni-Al Battery Negative Electrode

Wei Shengjun, Liu Lijie

2020, 41(1): 54-58. doi: 10.7513/j.issn.1004-7638.2020.01.010

Abstract(19) PDF(1)

Abstract:
The hydrogen absorption and desorption properties and electrochemical stability of vanadium-based hydrogen storage alloy for negative electrode of V₃TiNi_0.56Al_0.3 battery at different ball milling speeds and sintering temperatures were tested,compared and analyzed.The results show that with the increase of ball milling speed and sintering temperature,the maximum hydrogen uptake first increases and then decreases,while the discharge capacity decay rate first decreases and then increases,with the hydrogen uptake and desorption performance and electrochemical stability of the alloy increasing first and then decreasing.Compared with those of the alloy obtained at 300 rpm of ball milling speed,the maximum hydrogen absorption is increased by 26.53% and the discharge capacity attenuation is decreased by 50% for the alloy at 600 rpm of ball milling speed.The maximum hydrogen absorption is increased by 21.17% and the discharge capacity attenuation is decreased by 46.6% for the alloy obtained at 1 300 ℃ of sintering temperature,compared with the alloy at 1 000 ℃ of sintering temperature.The technological parameters of vanadium-based hydrogen storage alloy for negative electrode of V₃TiNi_0.56Al_0.3 battery are optimized at 600 r/min of ball milling speed and 1 300 ℃ of sintering temperature.

Fatigue Fracture Analysis of TA1 Electron Beam Welded Joint with a Thickness of 30 mm

Bai Wei, Li Dadong

2020, 41(1): 59-64,69. doi: 10.7513/j.issn.1004-7638.2020.01.011

Abstract(10) PDF(1)

Abstract:
In order to investigate the causes for fatigue fracture of the electron beam welding（EBW） joints,fatigue tests were conducted on joints welded by TA1 medium plates with 30 mm of thickness,and S-N curve and conditional fatigue limit were obtained.The macro and micro structures and mechanical properties of TA1 joints were investigated,and the fracture characteristics of the joints were obtained by combining fracture analysis of the fatigue specimens for the typical short-life joints.Test results show that electron beam welding（EBW） process can strengthen the weld seam and heat affected zone of TA1 joint,which makes the entire joint without obvious softening zone.The S-N curve data of TA1 electron beam welded joint conform the linear fitting law.The fitted fatigue limit value of 163 MPa is 48.7% of tensile strength of the joint,which conforms the general law of fatigue design of the metal structural parts.The main cause for the joint fracture is the existence of micron-sized welding pores,and the fatigue fracture for part of the joints is due to the existence of welding slag inclusion.

Effect of Pouring Temperature on Microstructure and Properties of New Vanadium Microalloyed Casting Magnesium Alloy

Huang Fang, Xu Yang

2020, 41(1): 65-69. doi: 10.7513/j.issn.1004-7638.2020.01.012

Abstract(14) PDF(1)

Abstract:
The casting experiments for the new magnesium alloy Mg-9 Al-1 Zn-0.6 V used for automotive parts were carried out at different pouring temperatures.The microstructure,tensile properties and corrosion resistance of the obtained magnesium alloy were tested and analyzed.The results show that with the pouring temperature increasing from 680 ℃ to 730 ℃,the tensile strength of the magnesium alloy increases first and then decreases,and the corrosion potential of the alloy presents a positive shift first and then negative displacement,companying improvement in microstructure,tensible properties and corrosion resistance of the samples.Compared with those of the sample obtained at pouring temperature of 680 ℃,both the tensile strength and yield strength of the sample at 710 ℃ increase by 18 MPa,and the corrosion potential positively shifts by 85 mV while the elongation after fracture decreases by 1% for the sample at 710 ℃.The optimum pouring temperature of the novel magnesium alloy Mg-9 Al-1 Zn-0.6 V is determined at 710 ℃.

Effects of Processing Parameters on Fuel NO_x in the Sintering Process

Liu Donghui, Li Junhua, Peng Yue, Chen Jianjun, Li Bing, Li Yuqing

2020, 41(1): 70-74. doi: 10.7513/j.issn.1004-7638.2020.01.013

Abstract(20) PDF(2)

Abstract:
Effects of processing parameters on emission concentration of the fuel NO_x in the sintering process were investigated using tube furnace.The results show that the average concentration of fuel NO_x increases first and then decreases with increasing the sintering temperature,reaching a maximum with the sintering temperature approximately at 1 100 ℃.As the holding time of high temperature and heating rate increase,the average concentration of fuel NO_x decreases from 87 mg/m³ and 91 mg/m³ to 77 mg/m³ and 80 mg/m³,respectively.When the oxygen content is lower than 21%,the average concentration of fuel NO_x has positive correlations with the oxygen content in the sintering process.The emission concentration of fuel NO_x mainly depends on the formation and reduction of NO_x in sintering process.Therefore,in the sintering process,the formation of NO_x can be inhibited or reduced by controlling sintering temperature,increasing heating rate,prolonging high temperature time or decreasing oxygen content,then the discharge amount of NO_x in the sintering flue gas can be reduced.

GRNN-SA-Based Model for Formula Optimization of Reconstructed Steel Slag

Xu Ying, Yang Shanshan, Wang Qiaoling

2020, 41(1): 75-81,94. doi: 10.7513/j.issn.1004-7638.2020.01.014

Abstract(9) PDF(1)

Abstract:
In order to solve the complex operation involved in steel slag reconstruction caused by the fluctuation of chemical compositions of steel slag,the general regression neural network（GRNN） model was constructed,taking the chemical compositions of steel slag,quicklime,fly ash and calcium fluoride（CaF₂） as input variables and activity index as output variables,respectively.And the formula optimization model of reconstructed steel slag based on GRNN-SA was established by using simulated annealing algorithm（SA） to optimize the calculation.Through empirical analysis,it is concluded that the model can realize the intelligent calculation of reconstruction batching process.This model is universal and can guide the intelligent calculation for steel slag from different sources.And it can predict the experimental results of steel slag reconstruction.The relative error between the actual activity index value and the predicted value is less than 5%,having a high simulation accuracy.

Uniaxial Compression Failure Test and Numerical Simulation of High Titanium Blast Furnace Slag Pervious Concrete

Wang Jun, Wang Hao, Jiang Zhongyou, Liang Hezhi, Yang He

2020, 41(1): 82-87. doi: 10.7513/j.issn.1004-7638.2020.01.015

Abstract(13) PDF(2)

Abstract:
Through uniaxial compression test of high titanium blast furnace slag（HTBFS） pervious concrete,it is found that the compressive strength of HTBFS pervious concrete can reach 9.2 MPa,which meets the design strength requirements of no-fines concrete on road base.And the morphology of failure surface for HTBFS pervious concrete with small particle size is mainly shown as aggregate fracture,slightly different from that of ordinary pervious concrete.In addition,through numerical simulation of uniaxial compression,the mesoscopic mechanical parameters of HTBFS pervious concrete were obtained,based on which the uniaxial compression numerical simulation curves can coincide well with the stress-strain curves of HTBFS pervious concrete with different particle size.Furthermore,the fracture development of HTBFS concrete model was observed by numerical simulation,and the feasibility for PFC simulation of uniaxial compression test of HTBFS pervious concrete was verified.The results of above research can provide reference for studying the stress state and failure mechanism of HTBFS pervious concrete.

Effect of Different Treatment Processes on Expansion Stability of Steel Slag

Xu Bo, Lan Tianzhu, Liu Chaohui, Liu Li

2020, 41(1): 88-94. doi: 10.7513/j.issn.1004-7638.2020.01.016

Abstract(7) PDF(1)

Abstract:
In view of the poor stability in engineering application of steel slag caused by the volume expansion,the methods of acetic acid immersion and micro-silicon powder addition were adopted to reduce the volume expansion ratio of steel slag according to the hydration reaction mechanism of free calcium oxide（f-CaO）.The volume fraction of acetic acid solution was controlled at 10%,15% and 20%,and the proportion of micro-silicon powder was 0.6%,1.2%,2.4% and 4.8%,respectively.The results show that both of the methods can effectively reduce the volume expansion ratio of steel slag,and its effect is positively correlated with the reagent proportion.In the acetic acid immersion group,soaking for 3 h is enough for full function,and more than 76.1% of reduction for volume expansion ratio can be obtained for each experiment.In the group of micro-silicon powder addition,obvious difference on reduction of expansion ratio of the steel slag can be found for different micro-silicon powder addition.When the micro-silicon powder proportion is more than 2.4%,the volume expansion rate reduces to less than 2%,and an expansion ratio of 0.4% corresponding to 87.1% of reduction can be obtained with the proportion of micro-silicon powder at 4.8%.

Coupled Model of Chemical and Heat Transfer for Preparing Ultrafine Iron Powder by Carbon Thermal Reduction in Steel Strip Furnace

Dong Yafeng, Guo Peimin, Zhao Pei, Wang Lei, Kong Lingbing

2020, 41(1): 95-99. doi: 10.7513/j.issn.1004-7638.2020.01.017

Abstract(10) PDF(1)

Abstract:
In this paper,a coupled mathematical model of temperature field and chemical reaction for producing ultrafine iron powder by carbon thermic reduction in a steel strip furnace is established.The simulation results are in good agreement with those of related experiments.Temperature distribution of material shows a a centrosymmetrical pattern. Temperature of upper and lower layer is higher than the center layer.The distribution law of reduction fraction is similar to the temperature distribution.The reduction degree of superfine iron powder is very sensitive to its thickness.The thinner the material layer,the higher the reduction degree.The average reduction degree of material with 25 mm thickness can reach 90%,while the material with 35 mm thickness is only 60% reduction degree.The reduction effect can be improved by prolonging the reaction time,but its effect on the reaction is smaller than the thickness.

Influence of CO-CO₂ mixture on Gas-solid Decarburization Reaction of Fe-C Alloy Sheet

Zhou Meijie, Hong Lukuo, Ai Liqun, Hou Yaobin, Zhou Chaogang

2020, 41(1): 100-104,112. doi: 10.7513/j.issn.1004-7638.2020.01.018

Abstract(15) PDF(1)

Abstract:
To investigate influence of CO-CO₂ mixture on the gas-solid decarburization reaction of Fe-C alloy sheet,the high carbon domain Fe-C alloy sheets with 1 mm the thickness was used to conduct decarburization reaction in weak oxidizing atmosphere（Ar-CO-CO₂）.The results show that the coverage rate of oxygen on surface of Fe-C alloy sheet decreases with increasing the flow rate of mixed gas.The higher coverage rate of oxygen is beneficial for decarburization.XRD analysis on decarburized surface shows that P_CO₂/P_CO shall be less than 0.37 to make sure less Fe being oxidized in 1 413 K.At the given conditions,when the volume ratio of CO is 25%,the better decarburization effect can be achieved.Increasing the decarburization temperature and/or prolonging the decarburization time to a certain degree can improve the decarburization effect.

Effect of Ca₃TiFe₂O₈ on Temperature of Liquid Phase Appeared in Sintering Process of Iron Ore Fines

Fu Xinyuan, Guo Xingmin

2020, 41(1): 105-112. doi: 10.7513/j.issn.1004-7638.2020.01.019

Abstract(6) PDF(1)

Abstract:
The different minerals were mixed with titanium-containing calcium ferrite Ca₃TiFe₂O₈ to study the melting temperature and mineral composition in sintering process of titaniferous iron ore by DSC and XRD methods.Results showed that the melting temperature of samples was lower than that of the each individual mineral in the sintering process,i.e.that of the Ca₃TiFe₂O₈+CaFe₂O₄,the Ca₃TiFe₂O₈+Fe₂O₃,the Ca₃TiFe₂O₈+CFA and the Ca₃TiFe₂O₈+SFC were 1 213 ℃,1 215 ℃,1 204 ℃ and 1 205 ℃ respectively.In addition,it was found out that Ca₃TiFe₂O₈ existed simultaneous with CaFe₂O₄,but was decomposed when it existed together with Fe₂O₃,CFA,and SFC,so it was considered as a intermediate product.Nevertheless,the sintering conditions of titanium-containing iron ore could be properly controlled to obtain the Ca₃TiFe₂O₈ that was conductive to the liquid phase formation for improving the diffusion condition during sintering process of iron ore fines.

Effect of MgO Content on Metallurgical Properties of Acid Pellets

Li Shenzi, Long Yue, Pan Xiangyang, Du Peipei, Ma Baoliang

2020, 41(1): 113-118. doi: 10.7513/j.issn.1004-7638.2020.01.020

Abstract(12) PDF(1)

Abstract:
Appropriate MgO content in pellets can improve their metallurgical properties and is beneficial to blast furnace smelting.Therefore,it is very important to determine suitable MgO content in pellets.In this experiment,Yanshan No.3 type of iron concentrate powder,dolomite powder and high magnesium powder were mixed to make pellets.The influence of MgO content on the metallurgical properties of acidic pellets was investigated by means of comprehensive tester for metallurgical properties of iron ore,XRD and metallographic microscope.The results show that with the increase of MgO content,the low temperature reduction pulverization and reducibility of acid pellets are improved.The best compressive strength of acid pellets can be achieved when MgO content is 2.0%,reaching 3 050 N.When MgO content is in the range of 1.8%～2.0%,the better mineral composition of pellets is obtained with morecalcium ferrite content and better crystallization of hematite.

Influence of Rare Earth on Microstructure and Carbide of 21-4N Steel

Wang Hongli, Du Simin, Cao Meijiao, Zhang Jian

2020, 41(1): 119-124. doi: 10.7513/j.issn.1004-7638.2020.01.021

Abstract(11) PDF(1)

Abstract:
The influence of Ce on microstructure and carbide of austenitic stainless steel 21-4 N both at as-cast and as-forged states were analyzed in this paper.The results show that the dendritic spacing,pearlite-like colony and the primary carbide M₇C₃ of as-cast steel can be refined significantly by adding appropriate rare earth Ce elements.The morphology of as-cast pearlite-like colony is improved and the number of primary carbides M₇C₃ is reduced significantly.Moreover,the grain size of forged austenite is remarkably refined.But the pearlite-like colonies of as-cast steel coarsens and primary carbides increase, therefore as-forged austenite coarsens when Ce content is too high.When Ce content of 21-4 N steel is between 0.011% and 0.015%,as-cast pearlite-like colonies are smaller and spheroidized,primary carbides are refined and increased,and austenite grains are refined.

Effect of Rare Earth on Inclusions Evolution of Cr12MoV Steel during VD Process

Du Simin

2020, 41(1): 125-130. doi: 10.7513/j.issn.1004-7638.2020.01.022

Abstract(14) PDF(1)

Abstract:
For Cr12 MoV steel produced by a domestic steel plant via EAF → LF → VD → die casting process,the amount of rare earth（La,Ce） added is 134×10^-6,and the samples is taken from liquid steel during VD process at different times.ASPEX automatic scanning electron microscope was used to analyze the composition,quantity and size of non-metallic inclusions in steel.It is found out that rare earth can improve the type and morphology of inclusions in steel,and transform more than 60% of irregular oxide and sulphide inclusions into spherical or ellipsoidal rare earth inclusions.The influence of rare earth on the amount and size of inclusions is related to the soft blowing time of the VD process.When the soft blowing time is controlled at 26 min～45 min,the number and size of inclusions in the steel are continuously reduced with the increase of soft blowing time.When the soft blowing time is prolonged to 55 min,the size of inclusions is still decreasing but the number is increasing,in particular to Al₂O₃ and REAlO₃ types.Considering the cost for inclusion modification and VD process for studied steel with 134×10^-6 rare earth（La,Ce） added,the optimal soft blowing time of the Cr12 MoV steel VD process should be controlled between 33～45 minutes.

Study on Effect of Ce for Titanium Inclusion of Steel by Aqueous Electrolysis

Lü Yong, Ren Hongzhi, Xing Jinxin, Jing Qiang, Peng Jun, An Shengli

2020, 41(1): 131-135. doi: 10.7513/j.issn.1004-7638.2020.01.023

Abstract(7) PDF(1)

Abstract:
The titanium-containing inclusions in the titanium-containing microalloyed steel were completely electrolytically extracted by an aqueous solution electrolytic method,and the non-destructive separation of the inclusions was achieved by a physical magnetic separation method.Samples of titanium-containing inclusions were prepared by ultrasonic dispersion and dripping of the suspension of the inclusions,and the morphology of titanium-containing inclusions in steel with the addition of rare earth was studied in combination with a scanning electron microscope.The study results showed that the morphology of titanium-containing inclusions changed to varying degrees with the increase in the amount of rare earth added.Without the addition of rare earth cerium,the titanium-containing inclusions in the steel had a typical cuboid morphology.When 0.003 8% rare-earth cerium was added,the rectangular parallelepiped titanium-containing inclusions were transformed into rectangular parallelepiped titanium-containing inclusions.When the amount of rare earth added was 0.005 4%,0.007 2%,and 0.009 8%,TiC-CeAlO₃,Ti（C,N）-CeAlO₃ formed,and the titanium-containing inclusions gradually changed into ellipsoid,and sphere,and the shape changed from the angular shape into inclusions with smooth curved surfaces,and the size of titanium-containing inclusions are reduced.With the increase of the amount of rare earth added,the precipitation amount of titanium-containing inclusions in steel increased,the precipitation ratio of titanium-containing inclusions with a diameter less than 1 μm increased,and the average size of titanium-containing inclusions gradually decreased.

Influence of Hot Compression on the Microstructure of GH4169 Alloy

Li Jialian

2020, 41(1): 136-140,151. doi: 10.7513/j.issn.1004-7638.2020.01.024

Abstract(9) PDF(1)

Abstract:
A systematic study has been made to investigate the microstructural evolution of GH4169 alloy under hot compression at temperatures from 900 to 1 150 ℃ with a reduction in thickness of 50%.It is shown that with increasing temperature,the microstructure of the compressed alloy evolves from a deformed structure to a partially recrystallized structure and finally to a fully recrystallized structure.Block carbides with sizes in micron scale and granular δ-phase with sizes in submicron scale are the main precipitates of the compressed alloy,which shows a significant contribution to the structural refinement.The grain size of deformed steel had been significantly reduced even at only 50% reduction.

Mathematical Modeling of the Recrystallization Kinetics of High Ti Microalloyed High Strength Steel

Hang Zidi, Feng Yunli, Cui Yan, Wan Decheng, Xu Yongxian, Zhang Zhen

2020, 41(1): 141-146. doi: 10.7513/j.issn.1004-7638.2020.01.025

Abstract(19) PDF(4)

Abstract:
Static recrystallization behavior of high strength steel with high Ti microalloying was studied by a Gleeble 3500 thermal simulation testing machine and stress relaxation method.The results show that the static recrystallization process is accelerated and the deformation rate has little effect on the static recrystallization under high deformation temperature and large deformation.The calculated activation energy of static recrystallization is Q_rex=276.45 kJ/mol,which confirms that the microalloy element Ti can inhibit recrystallization.Based on Avarami equation,the static recrystallization model of experimental steel has been established.

Corrosion Behavior of Ferritic Stainless Steel in Hydrochloric Based Acid with Ferrous and Ferric Ions

Jie Qiong, Xu Yong, Liu Chengjun, Jiang Maofa

2020, 41(1): 147-151. doi: 10.7513/j.issn.1004-7638.2020.01.026

Abstract(9) PDF(1)

Abstract:
The effects of ferrous(Fe²⁺) and ferric(Fe³⁺)ions on pickling behaviour of originally hot-rolled and blasted ferrite stainless steel（FSS） in HCl^- based electrolytes were investigated in this work through weight-loss test,macro profile,SEM morphology,self-corrosion potential test, polarization curves and electrochemical impedance spectroscopy measurements.The results demonstrated that the accumulation of Fe²⁺ in the electrolytes for pickling FSS would lower both the self-corrosion potential and the weight-loss rate,meanwhile Fe³⁺ had the opposite functions with higher self-corrosion potential and weight-loss rate.In the electrolytes of 3 mol·L^-1HCl,0.5 mol/L Fe³⁺ enhanced the weight-loss from 0.22% to 1.23%,while the same amount of Fe²⁺ reduced it to 0.14%.By promoting the molar ratio of Fe³⁺ and Fe²⁺(C_Fe³⁺/C_Fe²⁺) in the pickling electrolytes,the weight-loss rate of FSS would also increase accordingly.In the pickling electrolyte with 1.37 mol/L HCl and total ferrous and ferric ions of 1.79 mol/L,the weight-loss rate of FSS were enlarged 7.2 times or more than that without any ferrous and ferric ions when C_Fe³⁺/C_Fe²⁺≥2.It is concluded that in the pickling electrolyte with HCl,Fe³⁺ acts directly in cathodic reactions to accelerate the pickling of FSS,and Fe²⁺ replaces originally attached H⁺ in the interface of FSS and the electrolyte to partially inhibit the pickling rate.

Effect of Velocity of Atmospheric Laminar flow Plasma on Microstructure and Properties of Ductile Iron

Xue Ling, Li Longyi, Shuai Fan, Wang Jun

2020, 41(1): 152-157. doi: 10.7513/j.issn.1004-7638.2020.01.027

Abstract(16) PDF(1)

Abstract:
The surface quenching of QT450 ductile iron was carried out by using a self-developed laminar plasma system for surface quenching.The size,microstructure,hardeness of quenching zone was studied by optical microscope（OM）,microhardness tester,X-ray diffraction（XRD）,and scanning electron microscope（SEM）.The results showed that the quenching zone was composed of cementite,fine pearlite,martensite and partially retained austenite.The cross section from the outside to the inside of the samples was mainly composed of quenching zone,heat affected zone and matrix.Under these conditions,when the scanning rate was 500 mm/min,the size of the molten zone was the largest and the hardness was the highest.

Industrial Development of Extra Wide-width X70M Pipeline Steel Plate

Zhai Dongyu, Du Haijun, Jiang Jinxing

2020, 41(1): 158-164. doi: 10.7513/j.issn.1004-7638.2020.01.028

Abstract(10) PDF(1)

Abstract:
According to the technical requirements of Saudi Aramco and the technical parameters of 5 000 mm hot plate mill in NISCO,, the alloying design and process parameters had been deliberately selected,and thus producing 260 mm×2 570 mm section blanks with uniform composition and excellent low-profile structure. Combing TMCP rolling process with ultra-fast cooling technology, fine and uniform fine-grained structure dominated by acicular ferrite had been achieved. The developed products have good mechanical properties and low temperature impact toughness. Through small batch rolling, production process technology was established. Now NISCO is capable of supplying extra-wide X70 M grade pipeline steel plates.

Green Production Practice and Problem Analysis of Rebars under Newly Issued National Standard

Zhang Xiangjun, Fang Shinian, Lu Yong, Xiao Yuanzhong, Ding Hanlin, Pu Chunlei

2020, 41(1): 165-172. doi: 10.7513/j.issn.1004-7638.2020.01.029

Abstract(7) PDF(1)

Abstract:
In this paper green production practice of hot rolled ribbed bars in several domestic production lines under newly issued national standard has been present,and the process problems which is widespread in many production lines has been analyzed and summarized.In the end,corresponding solutions for producing rebar satisfying the requirement of new GB/T 1499.2—2018 standard in domestic iron and steel industry has been put forward.

Application of Rotary Injection Desulfurization Technology in Hot Metal Pretreatment

Gong Hongjun, Liang Xinteng, Zhou Zunchuan, Ge Wensun, Ceng Jianhua, Chen Jun

2020, 41(1): 173-178. doi: 10.7513/j.issn.1004-7638.2020.01.030

Abstract(24) PDF(1)

Abstract:
The existing problems of injection desulfurization had been analyzed.Based on the principle of KR desulfurization,the numerical simulation of rotary injection desulfurization process of injection desulfurization gun had been carried out.Through comparison,It is found out that the rotation of injection desulfurization gun can effectively reduce the splash of desulfurization process and improve the stirring of injection gas to semi-steel molten pool.On the basis of theoretical research,a new semi-steel desulfurization process based on rotary injection technology has been designed and developed in Panzhihua Iron and Steel Co.Ltd.The process has been applied to 140 t and 230 t semi-steel desulfurization convertors at Panzhihua Iron and Steel Co.and good results have been achieved.The average utilization ratio of magnesium in desulfurizer has increased from 55.46% to 68.27%,and the consumptions of splashing,iron loss and desulfurizer were reduced remarkable.The desulfurization efficiency has been improved to a certain extent.

2020 Vol. 41, No. 1