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Simultaneous Extraction of Vanadium and Chromium from Vanadium-chromium Slag by Sodium Roasting

Fu Zibi, Jiang Lin, Li Ming, Wu Zhenxiu

2020, 41(4): 1-6. doi: 10.7513/j.issn.1004-7638.2020.04.001

Abstract(293) PDF(16)

Abstract:
Based on the theoretical analysis and thermodynamic calculations of chemical reactions for sodium roasting of vanadium-chromium slag,the simultaneous extraction of vanadium and chromium by high sodium and low temperature roasting was proposed.The effects of particle size of vanadium chromium slag,addition amount of sodium carbonate,roasting temperature and time on leaching rates of vanadium and chromium were researched.The results show that a rate of 98.31% and 93.53% respectively for vanadium and chromium leaching can be obtained at the optimum conditions for sodium roasting,i.e.less than 0.074 mm of the particle size of vanadium chromium slag,50%～53% of sodium carbonate addition,60～70 min of the roasting time and 790～850 ℃ of the roasting temperature.After sodium roasting,the phases of V-Cr-Fe spinel,iron olivine and glassy in vanadium-chromium slag disappear basically,mainly with the new phases of sodium vanadates,sodium chromates,sodium pyroxene and Fe₂O₃ formed.

Experimental Study on Direct Reduction of Vanadium and Titanium-bearing Sea Sand Ore Pellets in Gas-based Shaft Furnace

Yan Fangxing, Zhang Qifu, Cao Chaozhen, Hou Jian, Li Naiyao, Lan Jiran

2020, 41(4): 7-11. doi: 10.7513/j.issn.1004-7638.2020.04.002

Abstract(223) PDF(6)

Abstract:
To explore the feasibility of direct reduction of vanadium and titanium bearing sea sand ore in gas-based shaft furnace,the oxidized pellets of the ore were obtained by roasting at 1 250 ℃ for 20 min,with compressive strength of 2 099 N,reduction index（RI） of 77.8%,reduction dusting index（RDI） at low temperatures of 92%,reduction swell index（RSI） of 7.5% and reduction cementation index of 10.4%,respectively.The reduction rate of the pellets at 950 ℃ for 180 min is 89.4% with H₂/CO=1.5,92% with H₂/CO=6 and 96% with pure H₂ as the atmosphere,respectively.All the indexes of the pellets are excellent and can satisfy the requirements of the gas-based shaft furnace.

Influencing Factors and Countermeasures for Vanadium Yield during Ferrovanadium Smelting in Cylinder Furnace

You Benyin

2020, 41(4): 12-17. doi: 10.7513/j.issn.1004-7638.2020.04.003

Abstract(231) PDF(4)

Abstract:
According to the characteristics of ferrovanadium smelting in cylinder furnace and the current state of vanadium recovery for ferrovanadium smelting in the world,the factors influencing the vanadium recovery were systematically analyzed,and the bulk density of vanadium oxides as well as the ramming quality of furnace lining were proposed as the main factors influencing the vanadium recovery for ferrovanadium smelting.From the aspect of process and parameters optimization,the measures for improving vanadium recovery during ferrovanadium smelting were provided which have a guiding significance for technical-economic index improvement for industrial ferrovanadium smelting.And the measures include bulk density of V₂O₃ controlled above 1.0,the mass ratio of V₂O₃ to V₂O₅ kept at 2.0～2.5,more than 60% of magnesia for ramming having 3～8 mm of particle size.Moreover,the roasting process of the furnace is suggested at 500 ℃ for 4 h followed by 900 ℃ for 11 h.The measures also include prolonging the refining time and adopting gradient aluminum addition,etc.After optimization,vanadium recovery rate for ferrovanadium smelting in cylinder furnace increases from 95.5% to 96.4%.

Preparation of Nano-TiO₂ Thin Film by Agar Coating Method and Its Photocatalytic Degradation Performances

Dong Hongxing, Liu Qiuping, Liu Yongfeng

2020, 41(4): 18-23. doi: 10.7513/j.issn.1004-7638.2020.04.004

Abstract(256) PDF(2)

Abstract:
Nano-TiO₂ thin films were prepared by agar coating method,and the photocatalytic properties of the prepared TiO₂ thin films were studied.The thin films were characterized by XRD,BET,FESEM,FTIR,EDX and UV-Vis DRS.The results show that the crystal size of TiO₂ prepared by agar coating can be reduced to 20 nm,while the crystal size of TiO₂ prepared by common sol-gel method is about 30 nm.The surface images show that the nano-TiO₂ thin films prepared by agar coating are uniformly distributed and have uniform morphology without crack.The results of UV-Vis DRS show that the bandgap of TiO₂ is reduced by adding agar,and the removal efficiency of methylene blue by the prepared TiO₂ is 71% in 120 min.The activity of TiO₂ remains at high level after 5 cycles of methylene blue treatment.The formation mechanisms of coating of nano-TiO₂ are also discussed based on the reaction characteristics.

Experimental Study on Sintering of Fine Ilmenite Concentrate

Wang Yujian

2020, 41(4): 24-29. doi: 10.7513/j.issn.1004-7638.2020.04.005

Abstract(326) PDF(6)

Abstract:
In view of the problems of fine particle size and high loss during electric furnace smelting of ilmenite concentrate,the sintering process of fine ilmenite concentrate was studied in this paper.It has the disadvantages of poor granulating,high burnup and low production efficiency for sintering of fine ilmenite concentrate.By physical and chemical detection and phase analysis,the consolidation mechanism of titanium concentrate and the reasons for the poor granulating effect were determined.Experimental results show that by adding flux,optimizing ratio of fuel and water,and grinding the ilmenite concentrates,the granulating effect of the ilmenite concentrates is improved.Through reducing sintering material layer,pelletizing the grinded ilmenite concentrate and adopting fuel divided adding on surface of the material for sintering,the technical and economic indicators of sintering are improved significantly,with the ratio of particles of +1 mm increased from 50.3% to 89.4% and the utilization coefficient enhanced from 0.177 t/（m²·h） to 0.712 t/（m²·h）,respectively.The desulfurization rate of ilmenite concentrate in the sintering process proposed in this paper is about 40%,influencing about 3%～4% of the TiO₂ grade.

Gas-based Reduction Kinetics of Sintered Ilmenite Concentrate

Song Bing, Zhu Fengxiang, Shi Mingchuan, Xiao Jun, Ling Peng, Hu Yuanjin

2020, 41(4): 30-35,40. doi: 10.7513/j.issn.1004-7638.2020.04.006

Abstract(236) PDF(5)

Abstract:
In order to deeply understand the gas-based reduction mechanisms of sintered ilmenite concentrate,the isothermal reduction of the sintered ilmenite concentrate was performed under the reduction atmosphere of 30% CO and 70% N₂ at 800,900 and 1 000 ℃,respectively.And the reduction kinetics was analyzed.The reduction degree of iron oxides in the sintered ilmenite concentrate increased with increase of the reduction temperature and time,with a relatively low reduction degree of about 70%.At 800～1 000 ℃,the reduction was controlled by interface chemical reaction during most of the reaction period（＜140 min） of the sintered ilmenite concentrate with the activation energy of 46.97 kJ/mol,while it was predominated by diffusion in the last reduction period（＞140 min） with the activation energy of 99.27 kJ/mol.The main phase transformations during the reduction process can be described as follows:Fe₂TiO₅→Fe₂TiO₄→FeTiO₃.The particle size of metallic iron in the reduced sample increased from 4.46 μm to 30.13 μm with increase of the temperature under the same reduction time.

Influence of Titanium on the Wear Properties of Graphene Reinforced Copper Matrix Composites

Xian Yong, Chen Deping, Liao Tingting, Ding Yichao, Wang Jing, Liu Yao

2020, 41(4): 36-40. doi: 10.7513/j.issn.1004-7638.2020.04.007

Abstract(285) PDF(2)

Abstract:
Graphene reinforced copper matrix composites were fabricated by titanium alloying and hot press sintering method.The tribological test was performed on a reciprocating tribometer.Phase was identified by X-ray diffraction（XRD） and microstructure and wear surface were determined by optical microscopy,scanning electron microscopy（SEM） and transmission electron microscope（TEM）.The results show that interfacial TiC nanoparticles are beneficial to bonding graphene and copper together efficiently.Copper-graphene composite doped with 0.25% Ti exhibits improved anti-wear performance with a low friction coefficient of 0.25 and a small volume wear rate of 10.5×10^-5 mm³/（N·m）（22% of that of pure copper）.However,excessive titanium causes degradation of friction properties.

Effect of Tungsten on High Temperature Plasticity of High Temperature Titanium Alloy by TiH₂ Powder Metallurgy

Ma Lan, Yang Shaoli, Li Junhan, Zhu Yuling

2020, 41(4): 41-47. doi: 10.7513/j.issn.1004-7638.2020.04.008

Abstract(305) PDF(2)

Abstract:
In this paper,titanium hydride（TiH₂） was used as raw material to prepare high-temperature titanium alloys by powder metallurgy.The effect of tungsten content on high temperature plasticity of the prepared Ti alloy was explored at deformation temperature of 750～900 ℃,deformation amount of 50%,and strain rate of 0.1 s^-1 and 1 s^-1.The results show that the overall structure of the alloy after high-temperature compression is similar to the mesh basket structure with the layer spacing of α phase significantly reduced,and the grain is refined.When the strain rate is low(0.1 s^-1),tungsten can increase the flow stress of the alloy.At the tungsten content of 0.5%,the maximum flow stress of the alloy is 423.1 MPa.When the strain rate is higher(1 s^-1),the flow stress increases first and then decreases as the tungsten content increases.At the tungsten content of 0.5%,the maximum alloy flow stress is 505 MPa.

Preparation and Properties of Porous Ti-Al Alloy

Zhang Meili, Luo Shushu, Dai Weili, Liu Yanfeng, Li Chun, Yang Chaopu

2020, 41(4): 48-53,59. doi: 10.7513/j.issn.1004-7638.2020.04.009

Abstract(319) PDF(4)

Abstract:
The porous Ti-Al alloys were prepared by powder metallurgy technique with elemental powder mixing,partial diffusion and reaction sintering.The effects of Al powder addition on phase structure,pore morphology,porosity,compressive properties and corrosion resistance of the alloy were investigated.The results show that the main equilibrium phase of the porous Ti-Al alloy is α-Ti and a small amount of Ti₃Al at the Al content of 5%～15%,and it has a closed pore structure with different sizes.The main equilibrium phase of the porous Ti-Al alloy is Ti₃Al and a small amount of TiAl at the Al content of 20%～30%,and it has an interpenetrating open-pore structure.As the Al content increases,the porosity of the alloy increases gradually,and the compressive strength decreases gradually,with the corrosion resistance increasing first and then decreasing.At the Al content of 20%,the porosity of the porous Ti-Al alloy is 26.7%,and the compressive strength is 63.9 MPa with the strongest corrosion resistance.

Study on Microstructure and Properties of Titanium Alloy for Building by Electromagnetic Pulse Forming

Cui Mengjun, Guo Qing

2020, 41(4): 54-59. doi: 10.7513/j.issn.1004-7638.2020.04.010

Abstract(205) PDF(2)

Abstract:
The electromagnetic pulse forming test of Ti-6Al-4V-0.5Cr,a new titanium alloy for building,was carried out at different processing parameters,and the microstructure and mechanical properties of the alloy were tested and analyzed.The results show that the experimental alloys with better properties can be obtained by electromagnetic pulse forming.The tensile strength,yield strength and elongation after fracture can reach 962 MPa,891 MPa and 14.5% respectively.With the discharge voltage increasing from 10 kV to 20 kV or coil spacing increasing from 4 mm to 10 mm,the structure of the tested alloy is refined first and then coarsened,and the mechanical properties are improved first and then decreased.Compared with the low discharge voltage of 10 kV,the tensile strength and yield strength of the tested alloy respectively increase by 14 MPa,11 MPa and the elongation after breaking decreases by 1.2% when the discharge voltage of 15 kV is used.Compared with the coil spacing of 4 mm,the tensile strength and yield strength of the tested alloy respectively increase by 11 MPa,9 MPa and the elongation after breaking decreases by 0.8% when the coil spacing is 7 mm.

Effect of WC on Microstructure and Mechanical Properties of TiC-based Cermets

Sun Qingzhu, Chen Min, Zhang Xuefeng, Wang Haibo

2020, 41(4): 60-64. doi: 10.7513/j.issn.1004-7638.2020.04.011

Abstract(246) PDF(4)

Abstract:
The effect of WC addition amount on the microstructure and mechanical properties of the TiC-based cermet was investigated using BSE,EDS and XRD.The results show that the hard phase of the cermet with WC added is constituted of white core-grey rim phase and black core-grey rim phase,both of which are face-centered cubic structure.Increase in the WC addition favors the formation of white core–gray rim phase in the cermet,enhancing the mechanical properties of the cermet.However,with increase of the WC addition,the carbides dissolved in the binder phase increase,and grey rim phases which are formed during the cooling process tend to be coarse in the cermet.The coated grey rim phases are brittle and are not conducive to the improvement of mechanical properties of the cermet.TiC-based cermet with the optimum mechanical properties can be obtained with 6% of WC addition.

Preparation and Properties of Vanadium-based Hydrogen Storage Alloy Based on Mechanical Vibration

Sun Chengning, Huang Wei, Zhang Junchao

2020, 41(4): 65-69. doi: 10.7513/j.issn.1004-7638.2020.04.012

Abstract(243) PDF(4)

Abstract:
The mechanical vibration with various vibration frequencies and vibration time were introduced into the pouring process to prepare V₃TiNi_0.56 vanadium-based hydrogen storage alloy for automobile battery,and the corrosion resistance,charge-discharge cycle stability and microstructure of the obtained samples were compared with those of the samples without mechanical vibration.The results show that the mechanical vibration can obviously refine the grain,improve the internal structure and improve the corrosion resistance and charge-discharge cycle stability of the alloy.With the increase of vibration frequency from 20 Hz to 60 Hz and vibration time from 5 s to 35 s,the internal grains of the alloy are refined first and then coarsened,both of the corrosion resistance and charge-discharge cycle stability are improved first and then decreased.Compared with the samples without mechanical vibration,the corrosion potential of the alloy prepared by introducing mechanical vibration with vibration frequency of 40 Hz and vibration time for 20 s in the pouring process positively shifts by 93 mV and the decay rate of discharge capacity decreases by 22%.

Research Progress on Precipitation Behavior of Nanoparticles in Ti-Mo Bearing Ferritic Steel

Huang Yao

2020, 41(4): 70-75. doi: 10.7513/j.issn.1004-7638.2020.04.013

Abstract(209) PDF(4)

Abstract:
The research trends of steel composition,process and mechanical properties of nano phase ferrite were introduced.The influence of composition,finishing rolling temperature,cooling rate,coiling temperature and isothermal time of different Ti systems,Ti-Mo systems and Ti-Nb systems on the behaviors and mechanical properties of structure and nano particles in steel were analyzed.The observation and research trends of interphase precipitation behaviors of nano particles in ferritic steel were analyzed.Ledge mechanism,solute drag-depletion mechanism,and super-ledge mechanism of interphase precipitation behavior of nano particles were compared and analyzed,and the advantages and disadvantages of the three models were analyzed.Finally,it is proposed that the design of highly ordered composite precipitated nanoparticles at nanoscale is a new way to develop ultra-high performance and stable nanostructured engineering steel.

Research Progress of Electron Beam Vapor Deposition

Lai Qi, Li Junhan, Wu Enhui, Cui Yan, Li Liang, Liao Xianjie

2020, 41(4): 76-81. doi: 10.7513/j.issn.1004-7638.2020.04.014

Abstract(548) PDF(15)

Abstract:
This paper introduces the control of deposition,composition and structure of materials in the process of high-speed electron beam evaporation under the control of vacuum and technological parameters.The hardware conditions are briefly discussed in order to provide an understanding way for the preparation of steel titanium composites.

Study on Granulation Performance of Blast Furnace Slag by Gas Quenching

Wang Lili, Zhang Yuzhu, Ke Haibin, Long Yue

2020, 41(4): 82-86. doi: 10.7513/j.issn.1004-7638.2020.04.015

Abstract(247) PDF(9)

Abstract:
Gas quenching dry slag granulation process is one of the dry slag treatment processes,and granulation performance mainly includes the average diameter,size distributions and bead forming rate.The effects of different gas velocity and slag viscosity on the granulation properties were experimentally studied.The results indicates that the particle size is mainly distributed between 1～3 mm.With the increase of airflow velocity,average diameter of slag particles decreases,and the proportion of the particles which are smaller than 3 mm increases gradually.Bead formation rate firstly increases and then decreases.With the increase of viscosity,average diameter of slag particles increases,and the proportion of the particles smaller than 3 mm decreases gradually,and bead formation rate decreases.The optimum airflow velocity is 550 m/s and low viscosity is beneficial to improve the granulation performance.With the increase of airflow velocity,the unsteady wave is strengthened and the ligaments are thinner,which is readily to break,so the average diameter of droplets is reduced.But the heat transfer effect is enhanced,which leads to the formation of fibers,so the bead formation increases firstly and then decreases.With the increase of viscosity,the unstable wave decreases,the diameter of the droplet increases,and the bead forming rate decreases.

Experimental Study of Fe Removal from TiC-containing Slag

Wang Dongsheng

2020, 41(4): 87-91. doi: 10.7513/j.issn.1004-7638.2020.04.016

Abstract(210) PDF(2)

Abstract:
The TiC-containing slag,which is produced by carbon reduction of BF slag,containes Fe 1.7% ～ 3.2%.In this paper,the removal of Fe from TiC-containing slag was studied by means of SEM analysis and experimental study.The results of SEM analysis indicated that the particle size of Fe in the TiC-containing slag was large,up to 150 μm,and a small amount of TiC was adhered to the edge of Fe particle.Furthermore,for different sizes of fine and coarse TiC-containing slag,the experiments of magnetic separation and removal of Fe by wet and dry methods were carried out respectively.The results showed that for the fine TiC-containing slag,although the effect of removing Fe by wet method was better than that by dry method,the removal rate of Fe in slag was only 54%.And for the coarse TiC-containing slag,it could be separated effectively by magnetic separation.Under the magnetic strength of 0.06 T,the removal rate of Fe could reach more than 99%,and the recovery of TiC was 86.2%.

Study on the S Content of Titanium Slag Acid Hydrolysis Tail Gas

Wang Haibo, Luo Zhiqiang, Wu Xiaoping, Ma Weiping, Wang Bin, Xing Huijin

2020, 41(4): 92-96. doi: 10.7513/j.issn.1004-7638.2020.04.017

Abstract(190) PDF(6)

Abstract:
To solve the problem of the exceeding S content in tail gas from a titanium dioxide plant,the S content of titanium ore and titanium slag raw materials was compared and analyzed.The S content of the tail gas under different acid hydrolysis conditions was simulated using sulfuric acid.Verification test of the effect of hydrolysis process on the S content of acid hydrolysis tail gas was carried out.The results showed that the S content of titanium slag was 0.10%,lower than the 0.15% S content in titanium ore.The S in titanium slag acid hydrolysis tail gas mainly came from sulfuric acid.During the simulation test,with the increase of sulfuric acid concentration,the content of S in the exhaust gas gradually decreased and the extent of decrease gradually decreased.As the temperature increased,the S content of the exhaust gas gradually increased and the extent of increase decreased.During the titanium slag acid hydrolysis process verification test,as the reaction acid concentration decreased from 92% to 84%,the maximum reaction temperature decreased from 226 ℃ to 186 ℃,the acid hydrolysis rate decreased from 93.19% to 90.78%,and the S content in the tail gas decreased from 0.55 g to 0.09 g.S originated from sulfuric acid decreased from 91.1% to 44.4%.The acid-slag ratio showed almost no visible effect on the S content in the tail gas.

Activation of Vanadium-titanium Magnetite Tailing and Its Application as Cement Admixture

Liu Haijun, Zhao Lili

2020, 41(4): 97-102. doi: 10.7513/j.issn.1004-7638.2020.04.018

Abstract(202) PDF(3)

Abstract:
In this study,mechanical activation and chemical activation methods were used to improve the activity of cement mortar.The effects of activation methods on the structure and properties of tailings were studied.The influences of activation conditions and tailings amount on the mechanical strength of cement mortar were analyzed.The results showed that garnet was the main mineral in the tailings and it was characterized by excellent chemical and structural stability,resulting in poor cementation performance.The cementing performance of tailings was significantly improved after ball milling for 5 h or adding lime.The properties of the gel material mixed with 35% tailings（5 h ball milling） could meet the requirements of 42.5 R composite Portland cement specified in GB 175—2007 standard.This study provides a theoretical basis for the use of vanadium titanium magnetite tailings as cement admixtures.

Effect of Dephosphorization Agent on Gasification and Dephosphorization of High Phosphorus Iron Ore Pellets

Guo Yuanzheng, Li Jie, Li Fei, Li Daliang, Liu Wenqiang, Cheng Yang

2020, 41(4): 103-107,114. doi: 10.7513/j.issn.1004-7638.2020.04.019

Abstract(251) PDF(3)

Abstract:
The development and utilization of high-phosphorus iron ore are restricted due to its high content of phosphorus.The occurrence state of phosphorus in high-phosphorous iron ores had been investigated by XRD diffraction.And based on the thermodynamic calculation results of FactSage7.2,the measures of pelletizing and pellet roasting had been carried out to explore the influence of different dephosphorization agents SiO₂ and CaCl₂ on the gasification and dephosphorization of high-phosphorous iron ores.The results showed that the phosphorus in high-phosphorous iron ores was in the form of Ca₅（PO₄）₃.After adding dephosphorization agent,the reaction temperature of gasification and dephosphorization began to decrease to 815 ℃.Under the experimental conditions of 1 250 ℃ and 5% carbon,0.8% SiO₂ and 1.6% CaCl₂ were added as the mixed dephosphorization agent,the optimum gasification dephosphorization performance had been achieved withdephosphorization rate of 22.1%.

Numerical Simulation of Electromagnetic Stirring in Billet Mold

Li Yaoguang, Wang Hongbin, Bai Xuesong, Sun Yanhui, Zhang Minghai, Jia Jianping

2020, 41(4): 108-114. doi: 10.7513/j.issn.1004-7638.2020.04.020

Abstract(306) PDF(4)

Abstract:
In this study a three-dimensional mathematical model of electromagnetic stirring in billet mold was developed by adopting ANSYS finite element analysis software.The effects of different process parameters on magnetic flux density and electromagnetic force in the billet mold were discussed.It is found out that the temperature of mold copper tube has obvious influence on magnetic flux density.On the axis direction of the stirrer center,the distribution of magnetic flux density is higher on both sides and lower in the middle.Nevertheless,the distribution of magnetic flux density and electromagnetic force is weaker in the middle and stronger on both sides,which is on the radial direction of the cross section of the stirrer center.As the frequency keeps constant,the magnetic flux density and the electromagnetic force increase with the increase of the current.When the current keeps constant,the magnetic flux density decreases with the increase of the frequency,while the electromagnetic force increases with the increase of the frequency.

Thermodynamic Study on the Precipitation Behavior of Carbonide and Nitride in X80 Pipeline Steel

Feng Qian, Ceng Yanan, Li Junguo, Tang Guozhang

2020, 41(4): 115-120. doi: 10.7513/j.issn.1004-7638.2020.04.021

Abstract(204) PDF(4)

Abstract:
In order to clarify the precipitation rule of precipitated particles in the solidification process of X80 pipeline steel,the Thermo-calc software was used to analyze the austenite and ferrite phase transition temperature,the type of precipitates,the precipitation temperature of the precipitates and the maximum mass fraction of the precipitated phase during the solidification of X80 pipeline steel.The calculation results show that the precipitation phase of X80 pipeline steel solidification process mainly includes MnS phase,AlN phase,ferrite phase and austenite phase,titanium-rich phase carbonitride precipitation phase,cerium-rich phase carbonitride precipitation phase and vanadium carbide precipitation phase.The precipitation temperature of the titanium-rich phase carbonitride precipitation phase is 1 390 ℃,the mass fraction is 1.2×10^-4,and the precipitation phase is inhibited by the increase of the content of C element and Nb element.The increase of N and Ti content promotes the formation of carbonitride precipitation phase in the titanium-rich phase,and the V element mass fraction increment has no obvious effect on the precipitation of titanium-rich phase carbonitride.The carbon-nitrogen precipitation phase of the yttrium-rich phase precipitated at 1 110 ℃,and the mass fraction was 1.3×10^-3.With the increase of the content of C and Nb,the precipitation of carbon and nitrogen in the eutectic phase was promoted.Increasing the content of N element and Ti element inhibits the precipitation of carbon-nitrogen precipitation phase in the enthalpy-rich phase,and V element has no obvious influence on the cerium-rich carbonitride.The precipitation temperature of vanadium carbide precipitation phase is 596 ℃,and the mass fraction of precipitated phase is 4.59×10^-5.Increasing the content of C and V element is beneficial to the precipitation of vanadium carbide phase.The increase of Nb content can inhibit the vanadium carbide phase.

Effect of Mn on Microstructure and Mechanical Properties of ULC Ti Microalloyed SM490A

Qin Xiangzhi, Lü Yuan, Xie Guoqing, Qi Haiquan

2020, 41(4): 121-124. doi: 10.7513/j.issn.1004-7638.2020.04.022

Abstract(287) PDF(2)

Abstract:
In the process of developing ULC SM490 A by Ti microalloying,excessive strength fluctuation was caused by different Mn content. Therefore,the influence of Mn on the microstructure and mechanical properties of ULC Ti microalloy steel has been studied. It is found out that when the Mn content was increased from 0.4% to 0.8% for base chemistry of 0.07%C+0.06%Ti compositions,the mechanical properties of the steel were significantly improved,the yield strength was increased by around 161 MPa,the tensile strength was increased by around 141 MPa,and the elongation after fracture decreased slightly.As the Mn content is increased,the microstructure of the steel has not changed,composed of ferrite and pearlite,but the ferrite grain size number is increased from 9.5 to 11～11.5,and the corresponding strength increment is about 44 MPa and 61 MPa calculated by the Hall-Petch formula.The total strength increment of about 35 MPa by those of Mn decreasing transition point and cause an increase in the dislocation density,plus [Si] and [Mn] substitute solution strengthening.Then it can be assumed that the strength increment due to TiC second phase strengthening by Wagner interaction of Mn element was about 65 to 82 MPa.TEM observation showed that when Mn mass fraction was increased,the TiC volume fraction was significantly improved about 3 times and particle size was about 10 nm,which was coincided with the second phase strengthening calculation.Therefore,it can be inferred that in the actual production process,the strength control of microalloyed steel can be achieved by adjusting Mn content,which undoubtedly has a positive effect on the development of microalloy steel.

Research on Redissolution Behavior of Nb and Ti in the High Strength Pipeline Steel

Ren Yi, Gao Hong, Liu Wenyue, Zhang Shuai, Wang Shuang

2020, 41(4): 125-129. doi: 10.7513/j.issn.1004-7638.2020.04.023

Abstract(196) PDF(3)

Abstract:
In this study,the redissolution and precipitation behaviors of niobium titanium carbonitride（Nb,Ti）（C,N） were researched by electrolytic phase analysis method and calculated by the simplified thermodynamic calculation method,and the dissolution law of Nb and Ti elements in high Nb pipeline steel was studied.The results showed that when the reheating temperature ranged at 1 180～1 280 ℃,the actual redissolution amount of Nb and Ti were lower than those of calculated values.When the reheating temperature was lower than 1 250 ℃,increasing temperature and heating time resulted into the significant solution amount of Nb in steel.When reheated at 1 250 ℃ for about 2.5 h,nearly 90% of niobium comes into solution and 11% of titanium into solution,since the titanium carbonitrides formed by have good stability.

Research on Carbide Control of High Speed Steel

Liang Wei, Li Jing, Shi Chengbin, Zhang Jie

2020, 41(4): 130-138. doi: 10.7513/j.issn.1004-7638.2020.04.024

Abstract(433) PDF(11)

Abstract:
The types,production process and development status of high speed steel are summarized.The effects of ESR process,hot processing deformation process,heat treatment process,cryogenic treatment and modification treatment on the carbides in high speed steel production,which are mainly based on smelting technology,are reviewed based on the research status at home and abroad.By summing up the key factors of carbide control in melting high speed steel,it is proposed to reduce the melting speed of ESR appropriately,strictly control the heating temperature and holding time of forging and rolling,optimize the heating temperature range and cooling mode of heat treatment,and add the deep cooling process and modifier in the traditional process to effectively control the large-scale carbide in steel,which will lay a foundation for the production of high-quality and high-performance high-speed steel.

Effects of Heat-treatment Processes on Microstructures and Properties of a 1 000 MPa Grade Vanadium-alloyed High Strength Steel

Zhang Gongting, Tang Di, Zheng Zhiwang, Zhao Zhengzhi

2020, 41(4): 139-144. doi: 10.7513/j.issn.1004-7638.2020.04.025

Abstract(344) PDF(5)

Abstract:
The 0.24%C-1.5%Si-2.0%Mn-0.16%V cold-rolled steel was heat treated at 780 ℃ intercritical annealing for 180 s,then quenching into 350～380 ℃ for 360 s,or quenching into 380 ℃ for holding 60～1 200 s.The microstructures and properties after heat treatments were tested by tension test,OM,SEM and XRD analysis.The results show that the good comprehensive property with tensile strength of 1 029 MPa,product of strength and elongation of 20.1 GPa·%,work hardening index of 0.22,is obtained by quenching into 380 ℃ for 360 s.The higher or lower quenching temperature,the higher tensile strength and the lower elongation are.As the holding time prolongs to 1 200 s,the strength and elongation are not varying much,but the yield platform appears.The volume fraction of retained austenite（RA） can be greatly affected by equal quenching temperature and time.The volume fraction of RA increases from 2.58% to 3.86% as isothermal the temperature increasing from 350 ℃ to 410 ℃,and then rapidly decreases in higher temperatures since martensite transformation is hindered and bainite transformation appears.And the RA maintains about 3.5% as the carbon has been enriched in austenite under isothermal quenching for 180 s.

Effect of Annealing Process on Microstructure and Mechanical Properties of 1 180 MPa Dual Phase Steel

Zhen Weijing, Chen Jundong, Li Yongliang, Wang Fuming

2020, 41(4): 145-149. doi: 10.7513/j.issn.1004-7638.2020.04.026

Abstract(224) PDF(2)

Abstract:
The influence of annealing process on microstructure and mechanical properties of super high strength steel DP1180 was studied by means of thermo-simulator system Gleeble-3500,field emission scanning electron microscopy and transmission electron microscope.The results show that the yield strength declines quickly when the annealing temperature is below 760 ℃ due to the annealing soften effect,but the martensite fraction shows no visible increasing.When the temperature is above 800 ℃, the strength decreases gradually because of the excessive austenitization and banitic transformation which could be attributed to the decreasing carbon concentration in austenite.A perfect match of strength and plastic could obtained when steel is annealed at between 760～800 ℃,at the same time,a refined and homogeneous microstructure could be obtained.

Effects of Pre-strain and Baking Temperature on the Microstructure and Bake-hardening Behavior of Mild Steel and Dual Phase Steel

Kuang Chunfu

2020, 41(4): 150-156. doi: 10.7513/j.issn.1004-7638.2020.04.027

Abstract(416) PDF(3)

Abstract:
In a typical process,mild steel and dual phase steel were respectively annealed at 800 ℃ for 90 s,cooled slowly to 680 ℃ and then cooled rapidly to 300 ℃ to carry out the overaging treatment.As a result,the ferrite-cementite mild steel and ferrite-martensite dual phase steel were obtained after the continuous annealing process.After pre-straining,the specimens were baked to measure the bake-hardening（BH） values.The influences of pre-strain and baking temperature on the microstructure evolution and bake-hardening behavior of mild steel and dual phase steel were investigated.It was found out that the bake-hardening（BH） value gradually increased with an increase in pre-strain from 0% to 8%.The BH value reached a maximum value of 65 MPa at the pre-strain of 8% in the mild steel.In the dual phase steel,the BH value apparently increased with an increase in pre-strain from 0% to 1%; however,increasing pre-strain from 1% to 8% led to a decrease in the BH value.The BH value reached a maximum value of 79 MPa at the pre-strain of 1%.Furthermore,an increase in the baking temperature from 140 ℃ to 300 ℃ favored a gradual improvement in the BH value in both of mild steel and dual phase steel.And the maximum BH values at the baking temperature of 300 ℃ were 71 MPa and 148 MPa in the mild steel and dual phase steel,respectively.The yielding platform appeared in the engineering stress-strain curve in the mild steel after baking.While the yielding platform was not observed in the engineering stress-strain curves of dual phase steel after baking at 140～170 ℃.However,the yielding platform appeared in the engineering stress-strain curve due to the martensite tempering in the dual phase steel baked at 210～300 ℃.

Study of Low Tempering Temperature on Microstructure and Properties of Cold-drawn Pearlite Steel Wires

Hu Yanan

2020, 41(4): 157-161. doi: 10.7513/j.issn.1004-7638.2020.04.028

Abstract(324) PDF(7)

Abstract:
The properties and structure changes of a cold-drawn pearlite steel wire annealed at 200～300 ℃ were studied,and the strengthening and toughening mechanism during tempering was revealed by means of scanning electron microscopy,transmission electron microscopy,X-ray diffraction and conventional mechanical testing methods in this paper.The results show that the pearlite layer of cold drawn steel wire is not continuous,and the precipitation behavior of cementite nanocrystals exists during drawing and tempering.The strength and ductility of cold-drawn steel wire are improved after annealing.With the increasing of annealing temperature,the strength is increased slightly and the ductility is further improved.The change of strength is mainly due to the dislocation strengthening effect,while the improved ductility is due to the fact that the newly precipitated nanocrystalline particles can reduce the stress concentration during tension by rotation and sliding.

Study on Influencing Factors of Corrosion Resistance of Hot Dip Galvanized Fingerprint Sheet

Hu Huadong, Kang Yefeng, Cha Kai, Dong Lihua

2020, 41(4): 162-167. doi: 10.7513/j.issn.1004-7638.2020.04.029

Abstract(276) PDF(5)

Abstract:
In this study a lot of production verification and test had been conducted to find the factors that influence the corrosion performance of fingerprint resistant sheet. It is found out that the corrosion resistant properties of hot dip galvanized fingerprint resistant mainly relates to drying temperature,film thickness,roughness,PC value and cure time.In the process of inspection and processing stamping and scratch exert effect on the corrosion resistant properties of the skin membrane.Based on the above observations,the corresponding relationship between the corrosion resistance and the drying temperature,film thickness,the roughness of the substrate and the PC value,cure time has been established,at the same time stamping and scratches during the inspection and processing has been avoided.All these measurement help to achieve the sheet meeting the technical requirements for the index of corrosion resistance,and guarantee the stability of hot dip galvanized fingerprint resistant corrosion performance.At present,the steel company is able to supply the hot dip galvanized fingerprint resistant sheet to Belgium and other European countries.

Optimization of Smelting Performance of Oxy-combustion Melting Furnace

Kong Zheng, Zhao Kai, Shi Xuefeng, Zhang Qiaorong, Shi Yan, Zhang Xiaohua

2020, 41(4): 168-176. doi: 10.7513/j.issn.1004-7638.2020.04.030

Abstract(213) PDF(3)

Abstract:
In this paper,the oxy-combustion melting furnace developed by a company had been taken as the research object.Based on the VOF multi-phase flow model and the Realizable k-ε model,the gas-liquid two-phase flow in the molten pool area of the melting furnace had been numerically simulated.Under the standard conditions,the effects of different oxygen immersion depth,oxygen gun diameter and oxygen gun tilt angle on the melting performance of the melting furnace had been investigated by means of single factor variables,matrix analysis and weight calculation,in order to achieve the goal of optimizing the molten pool smelting performance.The average velocity of the molten pool,the average turbulent kinetic energy of the molten pool and the melt gas content are selected as the relevant indexes for judging the melting performance of the molten pool area.According to the experimental results,the optimal structural parameters of the oxygen lance are as follows:oxygen immersion depth 70 mm,oxygen gun diameter 22 mm,oxygen gun tilt angle 22°.The influence degree of each parameter on the smelting performance of the melting furnace is in following order:oxygen lance diameter ＞ Oxygen gun tilt angle ＞ Oxygen gun immersion depth.After optimizing melting furnace condition the average stirring speed is increased by 9.13%,the average turbulent energy of the molten pool is increased by 7.43%,and the molten pool gas content is increased by 8.32%.

2020 Vol. 41, No. 4