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Technology Progress in Comprehensive Utilization of Converter Vanadium Slag

Ju Jinwei, Zhang Tingan, Niu Liping, Lü Guozhi, Zhang Weiguang, Chen Yang

2020, 41(5): 1-7. doi: 10.7513/j.issn.1004-7638.2020.05.001

Abstract(445) PDF(21)

Abstract:
Converter vanadium slag is a raw material for direct extraction of vanadium,which contains valuable metals such as vanadium,chromium,titanium and iron.At present,the extraction process of converter vanadium slag is mainly divided into sodium roasting-water leaching and calcification roasting-acid leaching.The process of sodium roasting-water leaching will produce a lot of harmful gases which will pollute the environment.Although no waste gas is generated during the process of calcification roasting-acid leaching,there are many impurities in the acid leaching solution,which affects the quality of vanadium products.Based on the necessity of comprehensive utilization of converter vanadium slag,this paper introduces the latest new technology for vanadium extraction from converter vanadium slag,discusses the advantages and disadvantages of the new process,and proposes some suggestions of comprehensive utilization of converter vanadium slag.

Technology Progress of Vanadium Precipitation in High Concentration Vanadium Liquid

Wang Jun, Zhu Xuejun, Ceng Chenghua, Deng Jun, Yang Tao, Wang Mingyue, Wu Yanting, Xie Bin

2020, 41(5): 8-13. doi: 10.7513/j.issn.1004-7638.2020.05.002

Abstract(324) PDF(22)

Abstract:
The precipitation of vanadium in a high concentration vanadium solution essentially influences the industrialization of vanadium slag sodiumization pelletizing roasting process.In order to provide a benchmark for solving the problem of vanadium precipitation in high concentration vanadium solution,the research on of hydrolyzed vanadium deposition in high concentration vanadium solution and acid ammonium salt deposition in high concentration vanadium solution had been reviewed,and progress of melamine deposition in high concentration vanadium solution was highlighted.Based on the advantages and drawbacks of these processes,the processes of hydrolyzed vanadium and acidic ammonium salt vanadium precipitation are thought not suitable for high concentration vanadium solution.The mechanism of vanadium precipitation with high concentration liquid and the influence of impurity elements on vanadium precipitation and the regulation mechanism should be investigated when taking into account of vanadium precipitation in high-concentration vanadium solution.In addition,it should be noted that melamine precipitation of vanadium can be a novel way of precipitating vanadium in a high-concentration vanadium solution.

Research on New Technology of High-efficiency Comprehensive Utilization of Vanadium-titanium Magnetite

Xie Zhicheng, Hu Bing, Hu Peiwei

2020, 41(5): 14-21. doi: 10.7513/j.issn.1004-7638.2020.05.003

Abstract(447) PDF(14)

Abstract:
In order to achieve low-temperature reduction of vanadium-titanium magnetite,high-value utilization of iron powder,and clean utilization of vanadium-rich titanium materials,a new process which includes grinding and removal of impurities,ore,coal,sodium salt mixed to make agglomerates,direct reduction-grinding,secondary reduction of iron powder,sodium roasting to extract vanadium for efficient and comprehensive utilization of vanadium-titanium magnetite was proposed.The results show that the grinding treatment of vanadium-titanium magnetite concentrate can effectively remove impurities,laying the foundation for the subsequent production of high-quality iron powder and efficient vanadium extraction.The addition of sodium salt can greatly reduce the direct reduction temperature and improve the reduction effect.After grinding and selecting the primary reduced iron powder and secondary reduction,the reduced iron with 98.72% grade can be obtained,and its chemical compositions and process performances reach the industrial first-level iron powder standard.V₂O₅ with 98.12% of purity can be obtained from the vanadium titanium enriched material by sodium oxidation roasting-water leaching-acid ammonium salt vanadium precipitation-calcination and deamination.A titanium-rich material with a TiO₂ grade of 49.61% can be obtained from the leaching residue through dilute sulfuric acid leaching.Under the selected conditions,the total recovery rates of Fe,V₂O₅ and TiO₂ from vanadium-titanium magnetite concentrates to secondary reduced iron powder,V₂O₅ products and titanium-rich materials are 90.75%,82.71% and 89.63%,respectively.

Study on Vanadium Precipitation by Hydrolysis of Chromium-vanadium Solution

Wu Zhenxiu, Jiang Lin

2020, 41(5): 22-26. doi: 10.7513/j.issn.1004-7638.2020.05.004

Abstract(447) PDF(22)

Abstract:
With the solution containing 17.86 g/L of vanadium and 15.96 g/L of chromium as the raw material,vanadium precipitation through hydrolysis was carried out in this work.The effects of pH value,temperature,time,chromium and sodium concentrations in the solution on the vanadium precipitation rate were investigated.The results show that a vanadium precipitation rate of 91.61% can be obtained at the pH value of 1.8 and the temperature above 95 ℃ for 60 min.At 1.7～17 g/L of chromium concentration in the solution,the precipitation rate of vanadium increases with increase of the chromium concentration,and 97.5% of vanadium precipitation rate can be achieved at 17 g/L of chromium concentration.However,the vanadium precipitation rate decreases with the chromium concentration exceeding 17 g/L,with the precipitation rate decreased to 95% at 25 g/L of chromium concentration.Furthermore,the rate of vanadium precipitation decreases obviously with increase of the sodium concentration（35.2～90 g/L） in the solution.Hence chromium with a proper concentration in the solution is favor for vanadium precipitation via hydrolysis,while sodium in the solution is adverse to vanadium precipitation.

Discussion on Smelting Technology of a High Chromium Vanadium Titanium Magnetite

Gao Shimin

2020, 41(5): 27-36. doi: 10.7513/j.issn.1004-7638.2020.05.005

Abstract(348) PDF(3)

Abstract:
This paper deals with a process for separation,recovery and extraction of various beneficial metals from high chromium vanadium-titanium magnetite.The main equipment of the process consists of a melting furnace,a chlorination furnace,several separation furnaces and their ancillary equipment.The mineral powder,coal powder,solvent powder and so on are reduced in the smelting furnace at high temperature.The resulting molten titanium-bearing slag flows into the chlorination furnace for high temperature chlorination.The resulting titanium tetrachloride gas is purified for production of titanium tetrachloride.The molten iron in the smelting furnace flows through several separate furnaces in turn.Each furnace bottom is sprayed with different separating agents or gases,which reacts with some beneficial metal in molten iron to form a less dense slag separated from the molten iron and discharged.The slag containing titanium slag,vanadium slag,chromium slag,cobalt slag and nickel slag can be obtained.The molten iron is discharged from the tail of the last separation furnace.A variety of beneficial metals are extracted from slag and flue dust discharged from smelting furnace,chlorination furnace and separation furnace by existing processes.This paper introduces the design idea,technological process,main equipment and its structure,main technical features,advantages and disadvantages,and compares the technology,economy and environmental protection with the current relevant technology,and discusses the feasibility of the technology.The main technical problems in the process are also discussed.

Separation of Vanadium and Chromium from Vanadium-chromium Solution by Calcium Salt Precipitation

Fu Zibi, Jiang Lin, Rao Yuzhong

2020, 41(5): 37-40,50. doi: 10.7513/j.issn.1004-7638.2020.05.006

Abstract(328) PDF(16)

Abstract:
Vanadium and chromium were selectively separated from the vanadium-chromium solution by calcium salt precipitation.The effects of CaO dosage,precipitation temperature and time on vanadium precipitation and the removal of chromium from calcium vanadate were studied.The results show that a precipitation rate of 99.89% and 1.26% respectively for vanadium and chromium can be obtained at 90～95 ℃ for 60～90 min with the ratio of actual amount of CaO to theoretical amount of CaO at 1.17～1.25.After beating and washing at room temperature,the content of chromium in calcium vanadate is about 0.06%,leaving the main phase of Ca₁₀V₆O₂₅.

Preparation of Ti Rich Materials with Low Ca and Mg by Carbothermal Reduction of Ilmenite

Zhang Tao

2020, 41(5): 41-44. doi: 10.7513/j.issn.1004-7638.2020.05.007

Abstract(248) PDF(9)

Abstract:
Using the ilmenite with high calcium and magnesium as the raw material,titanium rich material with low calcium and magnesium was prepared via carbothermal reduction followed by leaching process in the laboratory.XRD analysis of the reduced ilmenite shows that calcium exists in silicate phases of the reduced ilmenite,and magnesium and titanium form a solid solution of anosovite.The leaching test shows that calcium in the reduced ilmenite can be leached efficiently by hydrochloric acid,with the magnesium remaining in the solid solution.The leaching efficiency of magnesium can be improved significantly by adding boric acid in the carbothermal reduction process.Through the proposed process,titanium rich material with 0.13% of CaO and 1.12% of MgO can be obtained.

Effect of Salt Treating Agent on Conversion Rate of Rutile for Titanium Dioxide Hydrate

Ma Weiping, Sun Ke, Cheng Chaoyan, Shi Ruicheng

2020, 41(5): 45-50. doi: 10.7513/j.issn.1004-7638.2020.05.008

Abstract(223) PDF(33)

Abstract:
Potassium hydroxide,phosphoric acid and zinc sulfate were separately or overall added to the titanium dioxide hydrated for calcination,and the rutile conversion rate of the samples after calcination was detected by Raman spectrometer.The results show that with increase in the addition of single potassium hydroxide or phosphoric acid,the inhibition effect on rutile conversion is stronger,and the inhibition is more obvious at lower temperatures.Furthermore,the conversion rate of rutile is more sensitive to the calcination temperature at higher addition amount of potassium hydroxide or phosphoric acid,while it is mainly determined by the temperature at higher calcination temperatures.Using zinc sulfate as the agent,the conversion rate of rutile increases with increase in the addition amount.When it is higher than 820 ℃,the temperature becomes the main factor for promoting the conversion of rutile.The orthogonal test results show that the influence order of the factors on rutile conversion is phosphoric acid＞zinc sulfate＞potassium hydroxide.A relationship between the conversion rate of rutile and addition amount of salt treating agent,calcination temperature,i.e.Y（Y≥97）=90.9+0.09X₁-5.30X₂+0.42X₃+0.009 6X₄,is established via the orthogonal tests.

Influence of Al on Electrochemical Performances of Electrolyte and Battery of Vanadium Redox Battery

Zhang Zhongyu, Zhao Huan, Liu Lei, Zhao Feng, He Hongxiang, Zhao Jinling, Wang Shaoliang, Liu Jianguo, Yan Chuanwei

2020, 41(5): 51-57. doi: 10.7513/j.issn.1004-7638.2020.05.009

Abstract(518) PDF(9)

Abstract:
As the core material for energy storage and conversion of vanadium redox battery,the composition of electrolyte,especially the impurity content in the solution,greatly affects the physicochemical properties of electrolyte,reversibility of electrode reactions and the charge-discharge performance of battery.The influence of Al concentration on the physicochemical properties of electrolyte was studied,and the effect of Al on the electrochemical performances of electrolyte and battery was analyzed by cyclic voltammetry and charge-discharge test.The results indicate that with the increase of Al/V（molar ratio）,both of the viscosity and density of the electrolyte increase,with the conductivity obviously decreased.At the molar ratio of Al to V of 1∶3.0,the viscosity and density of the electrolyte increase by 64% and 2.8% respectively,and the conductivity of the electrolyte decreases by 34%.Furthermore,Al reduces the reversibility of positive and negative electrode reactions.Meanwhile,with increase in the molar ratio of Al to V,coulombic efficiency of the battery increases,with its voltage efficiency and energy efficiency significantly decreased.In addition,the stability of negative electrolyte is decreased due to the existence of Al.

Effect of Chemical Precipitation Process on Particle Size of VO₂ Precursor and Its Hydrothermal Crystallization

Liu Bo, Peng Sui, Chen Yong, Xin Yanan

2020, 41(5): 58-65. doi: 10.7513/j.issn.1004-7638.2020.05.010

Abstract(330) PDF(6)

Abstract:
Nanopowders of VO₂ were prepared by chemical precipitation assisted with hydrothermal crystallization using vanadyl sulfate as the vanadium source and sodium hydroxide as the precipitant.The influences of vanadium concentration,pH value of precipitation,reaction temperature,reaction time,type and dosage of surfactants on the particle size of precursor during chemical precipitation were studied.The crystal form,morphology,the size distribution and phase-transition temperature of products were analyzed by X-ray diffraction,SEM,particle size analysis and thermal analysis,respectively.The results show that the precursor with a minimum size of 210 nm can be obtained at the concentration of vanadium of 0.1 mol/L,the precipitation pH of 3.7,the reaction temperature of 20 ℃ for 5 min and the dosage of CTAB of 0.1%.High purity and homogeneity of M-VO₂ with the average particle size of 205 nm and the phase transition temperature of 65.3 ℃ can be obtained by crystallization of the precursor at 260 ℃ for 4 h in deionized water.

Influence of Transition Metals Ti and Co on Interfacial Microstructure and Strength of Copper-graphene Composites

Xian Yong, Chen Deping, Ding Yichao, Wang Jing, Lu Yanhong

2020, 41(5): 66-70. doi: 10.7513/j.issn.1004-7638.2020.05.011

Abstract(366) PDF(3)

Abstract:
Transition metals Ti and Co were separately introduced into copper-graphene composites by matrix alloying and powder metallurgy methods.The effects of Ti and Co on the strength of copper-graphene composites were compared by tensile test.The microstructure and interface structure of copper/graphene composites were characterized by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）and Raman spectroscopy.With addition of Ti,a large number of nano TiC particles were formed on the interface,which promoted the interface bonding without increasing graphene defects,and the tensile strength increased from 223 MPa to 256 MPa.Nevertheless,amorphous carbon appeared at the interface of Co doped composites.It increased graphene defects and was not conducive to play the role of strengthening phase and transferring interface load,resulting in the strength decreased from 223 MPa to 192 MPa.

Preparation and Properties of Isolating Membrane for Hot Rolled Metallic Composite

Zhang Fengzhen, Du Shunlin, Wang Tingkun, Jiang Qingwei

2020, 41(5): 71-76. doi: 10.7513/j.issn.1004-7638.2020.05.012

Abstract(263) PDF(2)

Abstract:
To solve the problems of isolation agent addition in blocking-hot rolling process for layered metal composites,isolation membrane with high heat resistance used for hot rolling laminated metal composite was prepared using inorganic substance with high temperature resistant as raw material which was modified by polymer.The microstructure,mechanical properties and thermal decomposition characteristics of the isolation membrane were analyzed by scanning electron microscopy（SEM）,the material universal testing machine and thermogravimetric analyzer,respectively.And the actual rolling effects of the membrane were also verified.The results show that the inorganic substance is embedded and dispersed in the framework of organic polymer which can be fully decomposed in the hot rolling process of the composite slab.And the inorganic substance remains in the surface of the metal,isolating the bonding of the unbonded surface of the cladding metal.The isolation membrane with a better toughness can be obtained at 55%～75% of the inorganic substance.The particle size of the inorganic substance has an effect on the surface quality of the laminated metal,and it is optimized at less than E μm.

Study on Titanium Film Deposited on Steel Belt Surface via Evaporation

Li Junhan, Sun Ning, Zou Yu, Lai Qi, Liao Xianjie, Ma Lan, Yang Shaoli

2020, 41(5): 77-80. doi: 10.7513/j.issn.1004-7638.2020.05.013

Abstract(160) PDF(3)

Abstract:
The titanium thin film was deposited via electron beam vacuum evaporation on the surface of steel belt by changing the tape travel speed. The phase composition and structure,cross-sectional morphology and film-base bonding force of the titanium film were studied by XRD,FIB,scratch test and other methods. The results show that the titanium film has a close-packed hexagonal structure,and it presents an intense preferred orientation at (002) lattice plane at different tape travel speeds. With the tape travel speed increased from 1 m/min to 4 m/min,the titanium film thickness increases from 744.7 nm to 855.9 nm,and the bonding force between the Ti-film and substrates decreases rapidly and then tends to be gentle. Within the tentative range,the maximum bonding force is 24.78 N.

Sticking Defects and Its Influence on Shell Tube in Rotary Piercing Process of Large Diameter TA2 Titanium Tube

Feng Qing

2020, 41(5): 81-85. doi: 10.7513/j.issn.1004-7638.2020.05.014

Abstract(183) PDF(2)

Abstract:
Aiming at the problem of the sticking defects in the rotary piercing process of large diameter TA2 titanium tube,the influence of the sticking defects on the surface condition,deformation defect,dimensional accuracy and other macro-quality of the pierced shell tube and the micro-structure distribution were analyzed.The results show that the rolling process time is extended due to the sticking defects and its treatments of the guide plate.The coating has a certain inhibition effect on the sticking defects,but it is basically failed after the single pass piercing rolling.The annealing micro-structure of the tube is equiaxed grains and the grain size is refined to a great extent after the rotary piercing process.The influence of the discs sticking defects and the process extension time on the grain size is not obvious.Therefore,the corresponding measures,e.g.control of the furnace temperature,optimization on feeding mode and adopting guide discs of cast iron,were taken to reduce the titanium sticking degree,which effectively improve the surface quality of the shell tube and reduce the loss of the discs.

Effect of Temperature Conditions and Additives on Selective Precipitation Process of Perovskite Crystals

Xu Ying, Li Dandan, Yuan Meng, Cai Yanqing

2020, 41(5): 86-95. doi: 10.7513/j.issn.1004-7638.2020.05.015

Abstract(337) PDF(7)

Abstract:
In order to further realize the effective recovery of titanium components from the titanium-containing blast furnace slag,the effect of temperature conditions and additives on the selective precipitation behavior of perovskite crystals were studied in this paper.By analyzing the chemical components and mineral compositions of titanium-bearing blast furnace slag,the selective precipitation technology was used to explore the effects of the Fe₂O₃ addition amount,the temperature holding range,the cooling rate and the additives on the perovskite precipitation and growth.Based on the investigation,the most favorable temperature range for perovskite crystallization was found around 1 350～1 320 ℃.With 3.2% CaO and 0.5% Fe₂O₃ added to the slag,and the temperature decreasing at a temperature reduction rate of 0.5 ℃/min in the range of 1 350 ℃ to 1 320 ℃,the crystal size and volume fraction of the perovskite phase precipitated reached the maximum values at the same time,respectively at 58.83 μm and 20.17%.Adding 4% CaF₂,2% Al₂O₃ or 2% MnO under the same temperature conditions can gradually increase the crystal size and volume fraction of perovskite in the slag,and thus realize the effective enrichment of TiO₂ in the titanium-containing blast furnace slag,which has created favorable conditions for the separation of perovskite phase.

Comparative Study on Preparation of Foam Glass-ceramics from Slow-cooling and Water-quenched High Titanium Blast Furnace Slag

Tian Jian, Feng Keqin, Yan Zidi, Liu Yanfang

2020, 41(5): 96-101. doi: 10.7513/j.issn.1004-7638.2020.05.016

Abstract(252) PDF(3)

Abstract:
High titanium blast furnace slag and waste glass powder were used to prepare foam glass-ceramics by "one-step sintering method",in which the foaming process synchronizes with the crystallization process.It can realize the high value-added overall utilization of high titanium blast furnace slag and is economical and environmentally sustainable.The effects of slow-cooling and water-quenched high titanium blast furnace slag on the preparation of foam glass-ceramics were studied.The results are as follows:the pore diameter and porosity of foam glass-ceramics gradually decrease,while the volum density and compressive strength gradually increase with increase of the addition amount of the two types of high-titanium blast furnace slag.The samples prepared from slow-cooling high titanium blast furnace slag has more irregular connected holes with a poor temperature insulation performance,while they have a noise reduction coefficient of 29% higher than that of the samples from water-quenched high titanium blast furnace slag which can be used as high strength sound absorption materials.The material prepared from water-quenched slag is mostly round closed pores with a lower noise reduction coefficient and better thermal insulation performance,which has a broad prospect for application to lightweight and high-strength thermal insulation materials.

Influence of Steel Slag Beads Substituting Fine Aggregate on Durability of Concrete

Wang Hui, Zhang Wei, Zhang Yuzhu, Guo Chen, Xing Hongwei

2020, 41(5): 102-106. doi: 10.7513/j.issn.1004-7638.2020.05.017

Abstract(197) PDF(3)

Abstract:
Steel slag beads are a by-product of steel slag formed by direct gas quenching of liquid steel slag.In this paper,steel slag beads were used as substitutes for fine aggregate of concrete,and the influences of substitution rates（0%,20%,35%,and 50%） of steel slag beads for the fine aggregate on the durability of concrete were studied.The results show that the corrosion resistance of the concrete is adversely affected by the steel slag beads substituting natural sand.The corrosion resistance coefficient with 50% replacement rate of steel slag beads is lower than 75% after 60 dry and wet cycles.Moreover,the freezing-thawing resistance of steel slag bead concrete is better than that of the ordinary concrete,and it is proportional to the substitution rate of steel slag beads.The steel slag beads can improve the carbonization resistance of the concrete.

Titanium Gypsum Strength Transition Point Model Establishment and Strength Mechanism Analysis

Yang He, Chen Wei, Liang Hezhi, Cai Xinyue, Wang Jun, Jiang Zhongyou

2020, 41(5): 107-112. doi: 10.7513/j.issn.1004-7638.2020.05.018

Abstract(211) PDF(3)

Abstract:
Studying various performance characteristics of titanium gypsum is of great significance for the recovery,resource utilization and re-use of titanium gypsum.In order to maximize the use of titanium gypsum,experiments were performed by replacing part of titanium gypsum with flue gas desulfurization gypsum（FGD）,and moisture content and strength tests were performed on titanium gypsum test blocks at different time points.The experimental results show that under natural curing conditions,with increase of the curing time both of the flexural strength and compressive strength of the titanium gypsum test blocks first decrease and then increase,and the moisture content decreases rapidly and then slowly.Using the Origin software to fit and analyze the experimental data,the Cubic（x,A,B,C,D） model can be used to predict the change in flexural strength and compressive strength of the titanium gypsum test block,and the LangmuirEXT2 function model can better predict the changes in moisture content of gypsum test blocks.The main reason for the decrease followed by increase in strength of titanium gypsum test blocks combined with SEM analysis is that the rapid loss of free water under natural curing conditions with the free water content around the dihydrate gypsum crystals decreased,and most of the water changes from physical adsorption to chemical adsorption which constitutes dihydrate gypsum crystals and forms effective structural strength.

Effect of MgO on the Softening-melting Process of BF Burden

Lu Jianguang, Li Jianpeng, Liu Xiaojie, Liu Kai, Lü Qing

2020, 41(5): 113-118. doi: 10.7513/j.issn.1004-7638.2020.05.019

Abstract(233) PDF(2)

Abstract:
The influences of different MgO contents in the mixed burden on the softening-melting properties of burden by high temperature simulation experiment were studied.The results indicate that with the increase of MgO content in the mixed burden,T_10% and T_40% increase,and the softening temperature range widens.The higher the MgO content,the greater the difference between T_40% and T_s.Besides,T_s,T_d and ΔT_ds all increase with the increase of MgO content in the mixed burden,which leads to the increase of the thickness of the melting zone.Finally,the ΔP_max and S of the softening-melting zone increase with the increase of MgO content in the mixed burden,which is not conducive to the stability of the blast furnace.

Effect of Ca Treatment on TiN Precipitation Behavior in Molten Steel

Huo Lu, Chen Jundong, Li Yongliang, Wang Fuming

2020, 41(5): 119-123. doi: 10.7513/j.issn.1004-7638.2020.05.020

Abstract(198) PDF(5)

Abstract:
The effect of calcium treatment on the precipitation of TiN secondary particles was studied using optical microscope and scanning electron microscope.The results showed that,after calcium treatment,TiN nucleated on the interface of CaS particles,forming composite precipitation.There was a large amount of coarse TiN-CaS particles,and the proportion of composite precipitation particles above 1 μm was up to 63%.Without the calcium treatment,TiN nucleated independently,the size of the precipitation particles decreased significantly,and the second phase particles above 1 μm decreased to 42%.The mechanism of nucleation and precipitation of TiN at CaS interface had been further discussed.CaS came from the reaction of Ca and S or complex reaction of CaO,Al₂O₃ and S in molten steel.The structure of the high melting temperature phases of CaS and TiN were cubic crystal with low lattice mismatch degree and low interface energy,which promoted TiN nucleation at its interface in advance.

Research on Elevated Temperature Mechanical Properties of 12Cr1MoVG Steel Continuous Casting Billet

Dong Kai, Liu Jianhua, Zhang Pei, Zheng Guiyun, Li Yaqiang, He Yang

2020, 41(5): 124-129. doi: 10.7513/j.issn.1004-7638.2020.05.021

Abstract(417) PDF(11)

Abstract:
In order to study the elevated temperature mechanical properties of 12Cr1MoVG steel continuous casting billet,12Cr1MoVG steel was subjected to elevated temperature tensile test at different temperatures by a Gleeble-3500 simulator.The fracture morphology,tensile strength and section shrinkage were analyzed and calculated.Experimental results show that tensile strength of 12Cr1MoVG steel decreases with increasing temperature,and the reduction of area decreases firstly and then increases with the increase of temperature.At 800 ℃ tthe plastic is lowest,and the temperature range of low temperature brittle zone is 738～865 ℃.The temperature range of γ→α phase transition calculated by Thermal-calc thermodynamic software is 747～869 ℃,which is agreement with the experimental results.The samples with tensile temperature higher than 900 ℃ show plastic fractures.When the temperature is lower than the low temperature brittle zone,the presence of inclusions causes the dislocations pile-up and then become the source of cracks and cause transgranular and intergranular fracture.

Effect of Annealing on Microstructure and Hardness of Ultra-high Strength Low Alloy Bainitic Steel

Du Simin

2020, 41(5): 130-135. doi: 10.7513/j.issn.1004-7638.2020.05.022

Abstract(240) PDF(3)

Abstract:
Three different annealing processes regarding forge cooling and isothermal softening were designed for ultra-high strength low alloy bainite steel produced by a domestic steel plant. The microstructure of the samples under different annealing processes was observed by scanning electron microscope,and the hardness was measured by a Brinell hardness tester. The results show that the microstructure of the materials under air cooling +sub-thermal spheroidization annealing is composed of tempered tortolite,where the carbides are intermittent or patchy,and hardness is 270 HB. The microstructure under air cooling +isothermal spheroidization annealing is still composed of tempered tortolite,where the carbides are thick strips,and hardness is 290 HB. The microstructure under furnace cooling +sub-thermal spheroidization annealing is composed of tempered sostenite,where the M-A islands are decomposed,the carbides are spheroidized and aggregated,and the ferrite is recovered. Hardness of steel with the later process is significantly reduced to 245 HB,which is appropriate for cutting performance.

Industrial trial on Ferrite Rolling of IF Steel in Hansteel 2250 Hot Continuous Rolling Mill

Wang Liangliang, Cao Xiaoen, Yu Xiaofei, Lü Chaojie, Su Zhenjun, Yang Jiankuan

2020, 41(5): 136-141. doi: 10.7513/j.issn.1004-7638.2020.05.023

Abstract(184) PDF(2)

Abstract:
In order to save energy and improve efficiency during hot rolling automobile steel sheet,Handan Company,HBIS Group carried out the industry trial production of ferrite rolling of ultra-low carbon IF steel relying on a production line of 2250 hot continuous rolling.The microstructure,mechanical properties of hot coiled strip,microstructure,mechanical properties and texture of the continuous annealing products were compared and analyzed.The results show that the microstructure of hot strip steel under ferrite rolling did not recrystallize,and the microstructure of hot strip under austenite rolling is composed of typical recrystallized polygonal ferrite.The yield strength R_p0.2 and tensile strength R_m of DC06 steel under ferrite rolling are higher than those of austenite rolling,and the fluctuation range is larger,and the elongation after fracture is reduced by about 10%.The microstructure of DC06 of ferrite rolling process is uniform,and the grain size is finer than that of austenite rolling,and its plastic strain ratio is relatively low and anisotropy is more obvious.The {111} texture of strip under austenite rolling process is stronger than that of ferrite rolling process,which is more favorable for stamping forming.

Influence of Solution Treatment Temperature on Microstructure and Pitting Corrosion Behavior of Heat Rolling 2205 Duplex Stainless Steel

Zhou Peng, Cui Shan, Shi Hongyuan

2020, 41(5): 142-146. doi: 10.7513/j.issn.1004-7638.2020.05.024

Abstract(310) PDF(3)

Abstract:
The effect of solution treatment on microstructure and pitting corrosion property of heat rolling 2205 duplex stainless steel was investigated by means of OM and immersing in a 10%FeCl₃ solution test.The results show that as the solution treatment temperature increase,the fibrous structure morphologies of austenite in hot rolling 2205 duplex stainless steel gradually evolves into equiaxed rod-like and island-like morphology,and evenly distributed in 2205 duplex stainless steel,and the volume fraction ferrite increases.A suitable volume fraction of α/γ-phase is distributed uniformly after solution treatment at 1 100 ℃.In a 10%FeCl₃ solution test,pitting corrosion resistance of 2205 duplex stainless steel increases with increasing the ferrite fraction.When the solution treatment temperature is 1 100 ℃,no obvious corrosion area appeares in the 2205 duplex stainless steel,thus the steel exhibits the best resistance to pitting corrosion.

PAW Welding Procedure and Joint Property of S22053 Duplex-stainless Steel

Du Yongqin, Wang Shuhua, Wang Heng, Zhang Jianxiang

2020, 41(5): 147-153. doi: 10.7513/j.issn.1004-7638.2020.05.025

Abstract(310) PDF(5)

Abstract:
The welding procedure test of S22053 duplex-stainless steel is performed by the keyhole PAW,the keyhole PAW+ auto-GTAW with filler metal for cover pass and the keyhole PAW+ auto-GTAW with filler metal for cover pass+auto-GTAW without filler metal for root pass in order to study service and welding characteristic of duplex-stainless steel as well as PAW suitability.The quality,properties and structure of these joints are analyzed by nondestructive examination,tension,bend,low-temperature impact as well as metallographic tests.These joints made by three welding procedures show higher tension strength than S22053 base metal,and excellent ductility,toughness and corrosion resistance,which meets the requirement of service characteristic for duplex-stainless steel. Compared with the PAW joint,the toughness and corrosion resistance of the joint welded by auto-GTAW with the filler metal after PAW weld decrease to a certain degree.

Study on Production Process,Microstructure and Properties of 12MnNiVR Steel for High Heat Input Welding

Feng Lulu, Tang Tao, Shu Xingguo, Qiao Wenwei, Zhou Feng

2020, 41(5): 154-158,165. doi: 10.7513/j.issn.1004-7638.2020.05.026

Abstract(212) PDF(4)

Abstract:
The high heat input welding steel 12MnNiVR was trial-produced by two different production processes.The microstructure and mechanical properties of the tested steel were obtained by optical microscope,tensile testing machine and low-temperature impact toughness testing machine,and the post-welding heat treatment behavior of the test steel was simulated by heat treatment test furnace.The results show that the tested steel produced by on-line quenching and off-line tempering process has a large amount of tempered sorbite and a small amount of tempered bainite,and a large number of carbides are evenly distributed on the ferrite matrix.In the quenched and tempered steel,the microstructure at room temperature changes from as-rolled ferrite and pearlite to more homogeneous tempered sorbite with more dispersed carbide after quenching and tempering.The tested steels produced by the two processes both exhibit excellent comprehensive mechanical properties,and after simulated post-weld heat treatment test,their properties did not decrease significantly.The on-line quenching and off-line tempering process has the advantage of eliminating reheat procedure,then can replace the quenching and tempering process,and has a positive and important role in reducing the production cost.

Effect of V Content and Heat Input on HAZ Softening Zone of Deep-sea Pipeline Steel

Yu Tengyi, Zhou Leilei, Li Ba, Yang Ping

2020, 41(5): 159-165. doi: 10.7513/j.issn.1004-7638.2020.05.027

Abstract(329) PDF(6)

Abstract:
In this paper,the welding thermal cycle process of deep-sea pipeline steel was investigated using welding thermal simulation.The microstructure variation,crystallography characteristic and second-phase precipitation behaviors of the softening zone of heat affected zone（HAZ） were characterized and analyzed by combining with the scanning electron microscope,electron back-scattered diffraction,transmission electron microscopy and hardness testing.The results show that HAZ softening zone appears in the fine-grained zone with a peak temperature of 1 000～900 ℃ for deep-sea pipeline steel whose base metal microstructure is the polygonal ferrite and acicular ferrite.Using V microalloying and low welding heat input can reduce the grain size,increase the proportion of small-angle grain boundaries and the dislocation density effectively.Thus,the softening problem of the HAZ fine-grained region can be effectively improved.

Effect of Vanadium Content on the Properties of 40Cr Die Steel

Yu Shujing, Li Jiming

2020, 41(5): 166-170. doi: 10.7513/j.issn.1004-7638.2020.05.028

Abstract(210) PDF(4)

Abstract:
Various contents of vanadium were added to 40 Cr die steel,and the microstructure,impact property at room temperature and wear resistance of the die steels were tested,compared and analyzed.The results show that proper addition of vanadium can improve the microstructure,increase impact absorption energy,reduce wear volume,improve impact property and wear resistance of 40 Cr die steel samples.Compared with the steel without vanadium,the impact absorption energy is separately increased by 6.25%,16.67% and 12.5%,and the wear volume is respectively decreased by 12.5%,26.92% and 24.04% for the sample with 0.25%,0.5% and 0.75% of vanadium,respectively.When the vanadium content is 0.5%,the impact absorption energy of the sample is the largest,and the wear volume is the smallest,with the best impact performance and wear resistance.The vanadium content in 40 Cr die steel is optimized at 0.5%.

Analysis of Forging Forming Process for High Strength Magnesium Alloys Mg-8Gd-1.5Y-1M Containing Ti

Fan Ruijun, Guan Zhiwei, Sun Cuixiang

2020, 41(5): 171-174. doi: 10.7513/j.issn.1004-7638.2020.05.029

Abstract(158) PDF(3)

Abstract:
The forging tests of Mg-8 Gd-1.5 Y-0.8 Ti high-strength magnesium alloy samples containing Ti were carried out with different initial forging temperature,final forging temperature and forging speed.The mechanical properties of obtained alloys were tested and analyzed.The results show that proper increasing of the initial forging temperature,final forging temperature and forging speed contribute to the improvement of mechanical properties.Mg-8 Gd-1.5 Y-0.8 Ti magnesium alloy containing Ti has the highest tensile strength and yield strength at initial forging temperature of 440 ℃,final forging temperature of 350 ℃ and forging speed of 12 mm/min.The tensile strength and yield strength were respectively increased by 51 MPa and 53 MPa compared with those forged at the initial forging temperature of 380 ℃,increased by 46 MPa and 49 MPa respectively at final forging temperature of 290 ℃,and increased by 39 MPa and 37 MPa compared with those forged at 4 mm/min.Thus it is proposed that the best forging process parameters of the Mg-8 Gd-1.5 Y-0.8 Ti high-strength magnesium alloy samples containing Ti are as following:initial forging temperature of 440 ℃,final forging temperature of 350 ℃,and forging speed of 12 mm/min.

2020 Vol. 41, No. 5