2019 Vol. 40, No. 4

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Technical Review
Status and Development of Titanium Dioxide Industry in 2019
Bi Sheng
2019, 40(4): 1-3. doi: 10.7513/j.issn.1004-7638.2019.04.001
Abstract(22) PDF(3)
Abstract:
This paper listed all kinds of industry data in 2018,analyzed the recent situation and development in 2019.It is considered that titanium dioxide industry has entered a period medium and low speed development,capacity concentration increased,titanium dioxide products are developing towards high quality,importance to environmental protection and clean production.
Separating and Extracting of Vanadium and Titanium
Thermodynamic Calculation and Experimental Study on Pre-reduction of Vanadium-titanium Iron Concentrate in Shaft Furnace
Cheng Xiangkui, Xiang Qinqin, Zhao Yingtao, Wang Jun
2019, 40(4): 4-10. doi: 10.7513/j.issn.1004-7638.2019.04.002
Abstract(35) PDF(2)
Abstract:
The equilibrium compositions,metallization rate and reduction degree of carbon-added pellets of Panzhihua vanadium-titanium iron concentrate pre-reduced in shaft furnace were calculated by HSC software.The metallization rate and reduction degree of the carbon-added pellets at different pre-reduction processes were studied experimentally.The experimental results show that with the increase of reaction temperature the metallization rate and reduction degree of the pellets increase,and the maximum metallization rate of 99.2% can be obtained at 800 ℃.The maximum reduction degree reaches 87.2% when the temperature rises to 1 000 ℃.The variation of metallization rate and reduction degree coincides well with the theory predictions.The maximum metallization rate and reduction degree are respectively 85.23% and 80.15% at 1 200 ℃.With the reduction atmosphere of 10% N2+30% H2+60% CO introduced from the bottom,the maximum metallization rate and reduction degree of 88.43% and 90.42% can be respectively gained at 1 200 ℃.Therefore,the reduction process can be reinforced obviously in circumstance of introducing reduction gas into the system.
Influence of Residue Recycle on Sodium Roasting of Vanadium Slag
Liu Dong, Xue Xiangxin, Yang He
2019, 40(4): 11-16. doi: 10.7513/j.issn.1004-7638.2019.04.003
Abstract(17) PDF(1)
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The roasting experiments were carried out with vanadium slag and the residue after vanadium extraction as raw materials,sodium carbonate and sodium chloride as sodium reagents,which aims to reduce the loss of vanadium resources and alleviate the environmental pollution.The effects of roasting temperature,holding time,alkali ratio and alkali-salt ratio on leaching rate of vanadium for samples with different vanadium contents were investigated by ammonium ferrous sulfate titration.The results show that proper addition of the residue can promote the conversion of vanadium.When the content of residue is 16.376%,the optimum calcination temperature is 800 ℃,holding time is 60 min,alkali ratio is 1.5 and alkali-salt ratio is 3.5,the leaching rate of vanadium reaches 98.43%.
Technology Research on Clean Vanadium-extracting from Vanadium Slag by Blank Roasting
Fu Zibi
2019, 40(4): 17-23. doi: 10.7513/j.issn.1004-7638.2019.04.004
Abstract(22) PDF(3)
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Aiming at the problems of high process cost and large amount of solid waste in existing vanadium extraction process from vanadium slag,a new process for preparing vanadium oxide from vanadium slag by blank roasting and carbonation leaching was proposed.The research mainly focused on the conditions of blank roasting and carbonation leaching.The results show that vanadium mainly exists in the form of Mn2V2O7 and Mg2V2O7 after blank roasting of vanadium slag at 860～900 ℃, and 90.49%～92.12% of vanadium leaching rate can be achieved under conditions as follows:concentration of NaHCO3 158 g/L、leaching temperature 95 ℃、leaching time 120 min;and V2O5 which satisfies the YB/T 5304—2017 standard can be obtained by adding sodium aluminate in the leachate for silicon removal and precipitating vanadium with NH4HCO3.The designed process route can realize the recycling of sodium and ammonia media,and has the characteristics of low process cost and less solid waste.
Existing States of Vanadium in Slag during the Preparation of FeV50 by Aluminum Thermal Reduction
Yu Bin, Yuan Tiechui, Xiao Daihong, Sun Zhaohui, Pan Cheng
2019, 40(4): 24-29. doi: 10.7513/j.issn.1004-7638.2019.04.005
Abstract(25) PDF(1)
Abstract:
The effect of different smelting stages on the occurrence of vanadium in the slag during the aluminum thermal reduction for FeV50 alloy preparation was analyzed,the thermodynamic reduction limit of vanadium in the slag was calculated by the study of V-O and VO-Al equilibrium theory.The actual stable structure of vanadium in the slag was obtained by different means of phase analysis.The results demonstrate that the steady state of vanadium in the slag is VO when the slag and alloy coexist,while the stability of VO and V2O3 is related to the partial pressure of oxygen after slag discharge.VO would be further oxidized under the condition of atmospheric pressure with the equilibrium oxygen partial pressure of 0.41 Pa.The total vanadium in the slag decreases with the increasing of aluminum in alloy,and the theoretical vanadium in the slag is 0.16% and 0.10% when the aluminum content is 8.0% and 20.0%,respectively.During the actual smelting process,the main materials of vanadium in corundum slag are composed of reduced FeV alloy as the primary phase and composite spinel structure of Mg（Al,V）2O4 and（Mn,Fe）V2O4 in the form of isomorphism.
Morphology Control for Ammonium Polyvanadate during Vanadium Precipitation Process by Ammonium Salt
Li Qianwen
2019, 40(4): 30-34. doi: 10.7513/j.issn.1004-7638.2019.04.006
Abstract(30) PDF(2)
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Ammonium polyvanadate was prepared via vanadium precipitation under acid condition using ammonium salt,and the effects of pH value,addition amount of ammonium salt,reaction temperature and time for precipitation on the morphology of the obtained ammonium polyvanadate（APV） were investigated.The results show that the spherical APV products with vanadium precipitation rate more than 99% can be obtained by reaction at temperatures above 70 ℃ for 30 min,pH=2.2 and ammonium addition coefficient K=2.3.Stability test results verify the reliability of the vanadium precipitation conditions.By controlling the morphology,high quality of APV products coupled with high vanadium recovery rate can be gained.
Effect of Potassium Hydroxide on Calcination of Metatitanic Acid
Ma Weiping
2019, 40(4): 35-38. doi: 10.7513/j.issn.1004-7638.2019.04.007
Abstract(17) PDF(3)
Abstract:
Potassium hydroxide was added into metatitanic acid during the calcination process,which aimed to study the effect of potassium salt on the rutile conversion,average particle size,morphology and crystal structure of the samples employing Raman spectroscopy,particle size analyzer and XRD characterizations.Compared with the blank sample,the temperature corresponding to over 99% of rutile conversion rate increased from 850 to 1 000 ℃,indicating a decrease in transition rate for anatase to rutile.The growth of grains during calcination of metatitanic acid was inhibited by potassium hydroxide,resulting in a well adjustment of the products’ crystal structure and avoiding the sintering at high temperature.The cell parameters a,b and c for the samples having more than 99% of rutile content with potassium hydroxide added,keep consistent with those of the standard structure,suggesting that the potassium hydroxide has no influence on the cell parameters of the products.
Application of Vanadium and Titanium
Effect of Hot Isostatic Pressing on the Microstructure and Mechanical Properties of Ti-6Al-4V Alloy Fabricated by Selective Laser Melting
Wang Lei, Ma Chao, Chen Jie
2019, 40(4): 39-44. doi: 10.7513/j.issn.1004-7638.2019.04.008
Abstract(27) PDF(1)
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The effect of hot isostatic pressing（HIP） on the microstructure and mechanical properties of Ti-6 Al-4 V alloy fabricated by selective laser melting（SLM） was studied.The results show the original acicular structure grows up rapidly along the length and width directions.Then the growth is hindered by interlaced α phase in the length direction and continues in the width direction.The structure transforms into short rod-like α phase at last.And α phase inherits the morphologies of destressing in the length direction and the width increases for the samples with destressing and HIP after SLM.The tensile strength and yield strength are lowered and the elongation is increased after HIP.The mechanical properties are not affected obviously with adding process of destressing.
Preparation and Interface Analysis of Graphene Nanosheets Reinforced Pure Titanium Matrix Composites
Zhang Zaiyu, Liang Yilong
2019, 40(4): 45-50. doi: 10.7513/j.issn.1004-7638.2019.04.009
Abstract(16) PDF(1)
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Graphene nanoplatelets（GNP） reinforced pure titanium lightweight structural materials were prepared by vacuum hot pressing sintering method.The microstructure of the powder and block samples were analyzed by optical microscope,scanning electron microscope and transmission electron microscope.The density test and tensile test were carried out on sintered samples with different content of graphene nanosheets.The research focuses on the dispersion of GNPs in titanium matrix and the interfacial bonding between GNP and titanium matrix.The results show that the interface between GNP and titanium matrix is clearly demarcated,forming a Ti/TiCx/GNP continuous structure.Most GNP still exists in its nanostructure except for a small amount of TiCx generated at the interface.
Effects of Heat Treatment on Microstructure and Mechanical Properties of Ti-6Al-4V Manufactured by Selective Laser Melting
Ma Chao, Wang Lei, Fu Xiaoqiang
2019, 40(4): 51-58. doi: 10.7513/j.issn.1004-7638.2019.04.010
Abstract(19) PDF(1)
Abstract:
The microstructure of Ti-6 Al-4 V alloy fabricated by selective laser melting was studied at different heat treatment conditions to reveal the internal relation during the heat treatment process,microstructure and mechanical properties.The results show that at 600～700 ℃ α′ martensite in the alloy is not completely decomposed to form a mixed microstructure of α′ and α+β,resulting in a high strength and low elongation for the alloy.When the temperature increases to 800～900 ℃,α′ martensite in the alloy can be fully transformed into steady lamellar α+β.After hot isostatic pressure,the metastable α′ martensite is completely converted to lamellar α+β and some local areas in the alloy are coarsened.With increase of the heat treatment temperature,the yield strength and tensile strength of the alloy are gradually decreased coupled with gradual increase of the specific elongation,compared with the deposition state.The optimum annealing temperature and holding time of the as-fabricated samples are determined at 800 ℃ for 2 h in combination with the growth behavior of grains.
Preparation and Properties of New Vanadium-based Battery Alloy for Electric Vehicles
Li Mei, Wang Qiang, Gao Hongwen, Han Quanye, Zhang Keming
2019, 40(4): 59-63. doi: 10.7513/j.issn.1004-7638.2019.04.011
Abstract(9) PDF(1)
Abstract:
Pressure casting tests were carried out for the new vanadium-based battery alloy V3TiNi0.56Ce0.2 used for electric vehicles at different ball milling speeds and time,and the hydrogen absorption and desorption property as well as the corrosion resistance were tested and analyzed.The results show that with increase of the ball milling speed and time,the maximum hydrogen adsorption of the alloy increases first and then decreases,and the corrosion potential presents a positive shift first and negative shift afterwards,meanwhile,the hydrogen absorption and desorption property coupled with the corrosion resistance of the alloy are first increased and then decreased.Compared with those of the alloy by 300 r/min of ball milling speed,the maximum hydrogen absorption and corrosion potential of the alloy obtained at 500 r/min of ball milling speed increases by 18.72% and positively shifts by 72 mV,respectively.Meanwhile,with the ball milling time extending from 0.5 h to 2 h,the maximum hydrogen absorption of the alloy can be increased by 25.52% and the corrosion potential positively shifts by 80 mV.The ball milling speed and time of the new vanadium-based battery alloy V3TiNi0.56Ce0.2 are determined at 500 r/min and 2 h respectively.
Properties Optimization of Alloy for a New Vanadium Based Hydrogen Storage Battery
Huang Minxiong, Li Yuanshi
2019, 40(4): 64-68. doi: 10.7513/j.issn.1004-7638.2019.04.012
Abstract(16) PDF(1)
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In this paper,the effect of Al addition on the microstructure,hydrogen absorption and desorption property,charge and discharge performance of a new vanadium-based hydrogen storage alloy was investigated.The results show that with increase in the addition amount of Al,the grains of the new alloy are refined first and then enlarged,and the maximum hydrogen absorption first increases and then decreases with the charge-discharge performance reduced first and then enhanced.Simultaneously,the microstructure of the alloy is gradually improved coupled with the hydrogen absorption-desorption property increasing first and decreasing afterwards,with increasing the Al addition.Compared with those of the alloy containing 0.1% Al,the average grain size and discharge capacity decay rate for the alloy containing 0.3% Al respectively decrease by 15 μm and 25% with the maximum hydrogen absorption increasing by 91.67%.The optimum Al content for the new vanadium-based hydrogen storage alloy is determined at 0.3%.
Optimization of Extrusion Temperature for Vanadium-containing Magnesium Alloy for Automobiles
Zhang Hongtao, Wu Xiaowei, Peng Liangdong
2019, 40(4): 69-73. doi: 10.7513/j.issn.1004-7638.2019.04.013
Abstract(14) PDF(1)
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In this paper,the vanadium-containing magnesium alloy Mg-8 Al-1 Zn-0.5 V used for automobiles was extruded at different temperatures,and the mechanical properties and microstructure of the samples were tested and analyzed.The results show that with the extrusion temperature increasing from 300 ℃ to 425 ℃,both of the tensile strength and yield strength of the alloy samples increase first and then decrease,and the specific elongation coupled with the average grain size of the samples decrease first and then increase,with both of the microstructure and mechanical properties of the samples improved.Compared with those of the sample at 300 ℃ of the extrusion temperature,the tensile strength and yield strength respectively increase by 13.38% and 14.57% with the specific elongation and average grain size separately decreased by 2.3% and 18.11% for the sample extruded at 375 ℃.The optimum extrusion temperature for the vanadium-containing magnesium alloy Mg-8 Al-1 Zn-0.5 V is determined at 375 ℃.
Resources Environment and Energy Saving
Factors Affecting Quality Loss of Sintering Flue Gas Treated by Activated Carbon Irradiated by Microwave
Shi Yan, Kong Zheng, Zhao Ying, Wang Shuai, Zhao Xin
2019, 40(4): 74-78. doi: 10.7513/j.issn.1004-7638.2019.04.014
Abstract(13) PDF(1)
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In this work,taking activated carbon as the research object,by changing the microwave heating temperature,heating time,activated carbon weight,SO2 concentration and NO concentration,the influence law of mass loss during the treatment of sintering flue gas by activated carbon under the condition of microwave irradiation was investigated.The results show that the increase of microwave temperature can accelerate the loss of activated carbon mass.When the microwave temperature is 800 ℃,the loss rate of activated carbon mass reaches 13.75%.The prolonged heating time will increase the mass loss of activated carbon.When the heating time is 15 min,the loss rate reaches the maximum value of 9.7%.Increasing the quality of activated carbon is beneficial to reduce the mass loss of activated carbon.When the mass of activated carbon is 50 g,the minimum loss rate is 4.04%.Increasing the concentration of each component of sintering flue gas can reduce the mass loss of activated carbon.When concentrations of SO2 and NO are 1 200 ×10-6 and 1 000 ×10-6,respectively,the according minimum loss rates are 2.57% and 3.28%,respectively.
Preparation of Autoclaved Bricks from Residue after Vanadium Extraction in Panzhihua
Yang Qingying, Zhong Yantao
2019, 40(4): 79-83,94. doi: 10.7513/j.issn.1004-7638.2019.04.015
Abstract(13) PDF(1)
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Autoclaved bricks were prepared from residue after vanadium extraction in Panzhihua,lime and sand by compaction moulding-autoclaving maintenance method,and the effects of rise and fall speeds of pressure,steam pressure and curing time on the compressive strength of the samples were studied.The compositions and microstructure of samples were analyzed,and the comprehensive performances and radioactivity were tested.The results show that the compressive strength of the samples increases first and then decreases with the increase in pressure-increasing speed and steam pressure,and that of the samples can be improved with appropriate decrease in pressure-reducing speed and increase in curing time.When the mass fractions of the residue,lime and sand are respectively 60%,23% and 17%,the rising and falling pressure speed is 0.7 MPa/h,and the steam pressure as well as the curing time is respectively 2 MPa and 7 h,the mechanical properties and radioactivity of the products meet the relevant industry standards respectively.The XRD and SEM analysis results show that after the autoclaved curing,needle-like tobermorite,slab-like hard calcium silicate and amorphous hydrated calcium silicate are formed in the products.The hydrated products interweave with coarse aggregate to form a compact structure,giving the products higher compressive strength and lower radioactivity index.
Preparation of Cement Mixture from Chromium-containing Steel Slag
Yang Fei, Sun Xiaomin
2019, 40(4): 84-89. doi: 10.7513/j.issn.1004-7638.2019.04.016
Abstract(12) PDF(1)
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Steel slag is an industrial waste,and the efficient utilization of steel slag has important environmental value.In this paper,steel slag was used to treat wastewater containing Cr3+ and then used as cement mixture.The effect of steel slag adsorbing Cr3+ was discussed.The influence of steel slag containing chromium on setting time and fluidity of cement mortar were studied,and the effect of steel slag on strength and hydration performance of cement products was investigated too.The mechanism of cement solidifying Cr3+ was analyzed.The results showed that steel slag could effectively dispose of wastewater containing Cr3+.When the Cr3+ concentration and pH of the wastewater were 40 mg/L and 6,respectively,and the liquid-solid ratio was 10∶1,the adsorption capacity and adsorption rate of Cr3+ on the steel slag reached 5.93 mg/g and 85.63%,respectively.The introduction of chromium-containing steel slag improved the fluidity of cement mortar,but reduced the compressive strength of products.The initial setting time,the final setting time and fluidity of cement mortar were 176 min,286 min and 193.2% respectively,when 32 % chromium-containing steel slag was added.The compressive strengths of cement products could reach 42.5 R grade after curing for 7 days and 28 days.XRD and SEM analysis displayed that the low hydration activity of steel slag and the addition of steel slag were not conducive to hydration products formation such as C-S-H gels and tobermorite.Cr3+ did not react with other components in the raw material,and its cementation by amorphous calcium silicate hydrate was the main reason to inhibit its leaching activity.Under acidic condition,the Cr3+ leaching concentration meet the requirement by GB5085.3—2007 standard.This study provides a new way for the efficient utilization of heavy metal adsorption steel slag.
Experimental Study on Recovery of Manganese from Wastewater of Vanadium Extraction
Chen Yan
2019, 40(4): 90-94. doi: 10.7513/j.issn.1004-7638.2019.04.017
Abstract(22) PDF(1)
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Using the process of chemical removal of impurities-electrolysis,manganese in the wastewater produced from vanadium extraction was successfully recovered.The effects of different factors（ferrisulphas addition,reaction temperature and time,terminal reaction pH） on removal of vanadium from the wastewater were studied,and the optimum vanadium removal parameters of 1.2 for molar ratio of Fe to V,60 ℃ of reaction temperature,40 min of reaction time and 6～7 of terminal reaction pH were determined.The cyclic voltammetry test results show that the wastewater after impurities removal has similar electrochemical properties with standard manganese electrolytic solution.The metallic manganese with a purity of 99.90%,and a current efficiency of 71.8% were obtained by electrolysis of the wastewater after impurities removal.The XRD results show that the obtained metallic manganese is of cubic and α-Mn crystal forms.
Ferrous Metallurgy and Materials
Research on Microstructural Characteristics and Metallurgical Properties of the High Basicity Sinter Made of Magnetite
Han Xiuli, Liu Lei, Chen Qianchong, Zhang Di, Bai Dongdong, Zhao Zhe
2019, 40(4): 95-99. doi: 10.7513/j.issn.1004-7638.2019.04.018
Abstract(18) PDF(1)
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The microstructures of two kinds of high basicity sinters made of magnetite were studied quantitatively by means of polarization microscope,and their metallurgical properties were tested.The influence of microstructure of sinter on its metallurgical properties was discussed.The results show that both sinters（1# and 2#） are mainly composed of magnetite,hematite and calcium ferrite with good compressive strength,thus they have good and similar drum index.The sinter 1# has the uniform microstructure in which interlaced erosion and erosion structure accounts for more than 90%.The sinter 2# has the inhomogeneous microstructure,consisting of 65% interlaced erosion,30% granular structure and 5% skeletal structure.The sinter 2# has obviously lower reduction pulverization index compared with sinter 1#,since the former has large amount of skeletal and granular hematite and the inhomogeneous microstructure.The reducibility of sinter 2# is slightly better than that of sinter 1#,which is related to the macro-porous structure,as its the porosity is as high as 30%.
Effect of MgO/Al2O3 on Metallurgical Properties of Sinter
Pan Xiangyang, Long Yue, Li Shenzi, Ma Baoliang, Du Peipei
2019, 40(4): 100-105. doi: 10.7513/j.issn.1004-7638.2019.04.019
Abstract(13) PDF(1)
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The effect of MgO/Al2O3 on the metallurgical properties of sinter was studied by laboratory sintering cup test device.The effects of MgO/Al2O3 on sinter strength,particle size composition,RDI and RI were studied in the range of 0.8 to 1.2.Microstructure and mineral composition of sinter were analyzed by metallographic microscope and X-ray diffraction.With the increase of MgO/Al2O3,the strength of sinter increases first and then decreases.When MgO/Al2O3 is 1.0,the strength is the best,and the proportion of 10 to 40 mm particle size is 58.85%.With the increase of MgO/Al2O3 from 0.8 to 1.2,the RDI of sinter is improved and the reducibility is worse.When MgO/Al2O3 is in the range of 0.9 to 1.0,the micro-morphology and mineral composition of pellets are better.Within this range,hematite and composite calcium ferrite have more quantity and better strength.When sintering with imported ore and local magnetite,MgO/Al2O3 is controlled in the range of 0.9 to 1.0 in order to obtain better micro-morphology and metallurgical properties.
Application of Biomass to the Direct Reduction Process
Ma Yusheng, Hong Lukuo, Zhou Chaogang, Yuan Peng, Ai Liqun
2019, 40(4): 106-109,115. doi: 10.7513/j.issn.1004-7638.2019.04.020
Abstract(15) PDF(1)
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In this paper,charcoal and anthracite were selected as reducing agent to study the influence of reduction temperatures,C/O,reduction time on metallization rate.In addition,the effect of reduction by charcoal and anthracite had been compared by using XRD analysis.The results show that the charcoal has similar reduction effect with anthracite when used for direct reduction process.Under same conditions（temperatures,C/O and time）,the effect of charcoal and anthracite on metallization rate have less difference.It is feasible that using charcoal as reducing agent in the direct reduction process.When temperature is 1 200 ℃,C/O is 0.7,and better reduction time is 20 min,using charcoal as reducing agent can achieve more than 80% metallization rate.
Study on Macro Segregation Control of Continuous Casting Billet in Gear Steel 20CrMnTiH
Chen Liang
2019, 40(4): 110-115. doi: 10.7513/j.issn.1004-7638.2019.04.021
Abstract(14) PDF(1)
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In order to control the macro-segregation of gear steel,the chemical analysis and original position analyzer were applied on carbon distribution of billets in cross section.The superheat,casting speed,electromagnetic stirring and flowrate of secondary cooling testes had been performed and the optimal casting parameters were determined.The test results show that superheat range should be controlled at 20 ℃±5 ℃ and casting speed should beat 1.30 m/min.The current intensity of M-EMS and F-EMS should be 250 A and 50 A respectively.The flowrate of secondary cooling should be 0.41 L/kg.These parameters were benefit to the macro segregation control.The industrial results indicated that carbon segregation indexes of billets in cross section were 0.94 to 1.05 and hardness variation of bar at cross section were at ±10 HV range.
Study on Corrosion Resistance and Wear Resistance of New Vanadium-containing Weather Proof Steel for Building
Ye Zhanchun, Guan Chunlong
2019, 40(4): 116-120. doi: 10.7513/j.issn.1004-7638.2019.04.022
Abstract(17) PDF(1)
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In this paper,a new type of weatherproof steel for building containing vanadium was prepared by adding different content of vanadium in Q450 NQR1 steel,and the microstructure,corrosion resistance and wear resistance of the new steel were tested and analyzed.Vanadium has a significant effect on the corrosion and wear properties of the new steel.Compared with Q450 NQR1 samples without vanadium,best corrosion resistance and wear resistance can be obtained for Q450 NQR1-0.5 V samples with 0.5% of vanadium added making the corrosion rate and wear volume reduced by 45.47% and 34.38%,respectively.From the point of view for optimizing the corrosion resistance and wear resistance of the new vanadium-containing building weatherproof steel,the vanadium content is optimized at 0.5%.
Influence of Vanadium Content on Austenite Recrystallization Rule of Low Carbon Steel
Xiong Xuegang, Zhang Kaihua, Wang Yi, Ye Xiaoyu
2019, 40(4): 121-125. doi: 10.7513/j.issn.1004-7638.2019.04.023
Abstract(8) PDF(1)
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To investigate the dynamic recrystallization rule of vanadium microalloying low carbon steel and its influence factors,flow curves under dynamic recrystallization conditions of 4 kinds of V-N microalloy steels were obtined by experiments so that the relationship of peak stressσp,strain rateεandtemperature T was obtained from the flow curve.The effect of temperature and content of V,N on dynamic recrystallization model was studied.By the way,an Avrami model for V-N microalloy steels was establishedand and the dynamic recrystallization activation energy was obtained by regression.The results show that V has a limit effect on improving the dynamic recrystallization critical temperature,while V combined with N has the significant effect on the critical temperature so as to inhibit the dynamic recrystallization.
Hydrogen Permeation Behaviors of Microalloyed TRIP-assisted Annealed Martensitic Steels
Yang Xiongfei, Yu Hao
2019, 40(4): 126-131. doi: 10.7513/j.issn.1004-7638.2019.04.024
Abstract(9) PDF(1)
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In this paper a serials of TRIP-assisted annealed martensitic（TAM） steels had been obtained through niobium,vanadium and/or titanium microalloying additions into a base chemistry of 0.2%C-1.5%Si-2.0%Mn,and a complex heat cycles of double quenching+tempering processes.From the hydroden charging curves microalloyed precipitates have significant effects on delaying/retaining the hydrogen diffusion through steel matrixs.Hydrogen charging test results indicates that when microallying additions are at silimar level,Nb microalloying steel has the lowest apparent hydrogen diffusive index Da=0.716×10-7 cm2/s,Ti steel with moderate Da=1.136×10-7 cm2/s,while value is 2.647×10-7 cm2/s for 0.052%V steel.However,all these values are far lower than that of refered steel with its Da=4.215×10-7 cm2/s.For V-microalloyed steels,the SSRT results show that the hydrogen induced ductility loss ID is 76.2% for 0.2%V steel,compared with 86.5% for V-free steel.The trapping mechanism of the steel containing different V contents is analyzed by means of TDS and TEM observation.It is found that the steel containing 0.2%V can create much more traps and higher activationenergy for hydrogen trapping compared with V-free steel,which is due to VC as hydrogen traps capturing hydrogen.The relationship between hydrogen diffusion and hydrogen trapping mechanism is discussed in details.
Effect of Niobium on Microstructure of X80 Grade Pipe Line Steel
Dai Liangliang, Zhu Chenglong, Gu Ye, Zhang Jiming
2019, 40(4): 132-137. doi: 10.7513/j.issn.1004-7638.2019.04.025
Abstract(17) PDF(2)
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Microstructure of high strength X80 pipeline steels which contain different Nb contents was investigated using optical microscopy and transmission electron microscopy.Second phase particles were analyzed by extraction replica method.Results show that microstructure of low Nb content steel comprises granular bainite and Lath-like bainite,and a few of martensite-austenite（M-A） islands.However,microstructure is consisted of fine acicular ferrite and M-A islands in high Nb content steel.Precipitates in low Nb pipeline steel are large scale cubic TiN particles,however,precipitates of high Nb pipelines steel are mainly the large size duplex type（Nb,Ti）C and fine NbC precipitates.
Effect of Niobium on Solid Solution Temperature of Precipitates in Oriented Silicon Steel
Liu Jiamei, Jin Donghao, Jia Yunke, Feng Yunli
2019, 40(4): 138-143. doi: 10.7513/j.issn.1004-7638.2019.04.026
Abstract(18) PDF(1)
Abstract:
Two kinds of billets containing 0.09% niobium and niobium free were used for this study.The billets had been heated up to different temperatures and then quenched after holding for 30 min.The microstructure of the samples was observed by JEM-2011 transmission microscope.At the same time,the morphology of black material in as-cast microstructure was determined by scanning electron microscope（SEM）.By observing the quantity distribution of precipitates obtained at different soaking temperatures,the effect of niobium addition on solid solution temperature of precipitates in Nb and Nb-free steels were compared and analyzed.The results show that:The grain size of niobium containing oriented silicon steel billet is more uniform and smaller than that of niobium-free billet.Niobium element can hinder grain growth.The complete solid solution temperature of precipitates in Nb-containing oriented silicon steel is between 1 250 ℃ and 1 300 ℃,and the total solid solution temperature of precipitates in steel without Nb is above 1 300 ℃,indicating that Nb can obviously reduce the complete solid solution temperature of precipitates.
Thermodynamic Model for Carbonitride Precipitation in Low Carbon Steel with Nb-Ti-V and Verification
He Feiyu, Dong Jian, Sun Yanhui
2019, 40(4): 144-151. doi: 10.7513/j.issn.1004-7638.2019.04.027
Abstract(17) PDF(1)
Abstract:
Carbonitride precipitates influence the microstructure and properties of steel by grain refinement and precipitation strengthening.Based on a two-sub lattice model（metal atom sub lattice and interstitial atom sub lattice） of regular solution,a thermodynamic model for the precipitates of carbonitride,aluminium nitride and manganese sulfide was established and then used to calculate the starting-temperature of precipitates,the equilibrium molar fraction and the evolution of precipitation.The precipitation pattern was verified by Thermo-Calc software,transmission electron microscope（TEM） and energy dispersive spectrometer（EDS）.The calculation results show that starting-temperature of precipitation of MnS and AlN are 1 200 ℃ and 675 ℃,their molar fraction are 1.05×10-4 and 1.21×10-4.The evolution order of precipitation particles is(Nb0.29Ti0.68V0.03)(C0.01N0.99),(NbxTivV1-x-v)(CyN1-y) and(Nb0.29Ti0.45V0.26)(C0.87N0.13).By comparison,the simulation results of the model are in good agreement with the calculation by the Thermo-Calc software and the TEM observation results.
Analysis for Processing Map of Fe-13Cr-4Al Alloy
Zhang Yiyong, Wang Hui, Yang Pan, Zhang Hongzhi, Sun Lin
2019, 40(4): 152-157,163. doi: 10.7513/j.issn.1004-7638.2019.04.028
Abstract(16) PDF(1)
Abstract:
The hot deformation behavior of Fe-13 Cr-4 Al alloy was investigated by compression test on a Gleeble-1500 thermal simulator under the temperatures of 800～1 000 ℃ with strain rates of 0.01～10 s-1.Based on experimental data,the true stress-strain curves of Fe-13 Cr-4 Al alloy were drawn,which showed that dynamic recrystallization occurred at the low strain rates(0.01～0.1 s-1) and dynamic recovery occurred at the high strain rates(1～10 s-1).According to the dynamic material model dissipative structure theory,the processing maps of Fe-13 Cr-4 Al were established at different true strains.The effect of strain on power dissipation rate was complicated.The peak power dissipation rate occurred at the temperature of 1 000 ℃ and strain rate of 0.01 s-1,and it increased with increasing strain.It could be seen from the processing map the optimum hot deforming domain was determined to be temperature of 800～850 ℃,strain rate of 0.01-1 s-1;temperature of 900～1 000 ℃,strain rate of 0.01-0.0.02 s-1 and temperature of 900～1 000 ℃,strain rate of 0.5～10 s-1.
Research on Low-temperature DWTT of 33mm Thick-wall X80 Pipeline Steel Plate
Jiang Changlin, Lin Tao, Zhu Jianyang
2019, 40(4): 158-163. doi: 10.7513/j.issn.1004-7638.2019.04.029
Abstract(11) PDF(1)
Abstract:
The shear area of low-temperature DWTT of thick-wall X80-grade pipeline steel plate is now becoming a high technical challenge.In the paper,based on alloying design, 33 mm thick-wall X80 pipe line steel plates were obtained through different thickness of inter-mediate bar from non-recrystallization austenite region rolling when the other processing parameters of TMCP（thermo mechanical control process） maintained same values.The micro-structures and properties of resulted plates were investigated and analyzed by means of optical microscope.Comparing the microstructures obtained by the two different rolling processes,it is founded out that increasing thickness of intermediate bar from non-recrystallization austenite region（before starting finishing rolling） can enhance the volume fraction of ferrite and obtain smaller ferrite grains,thus can increase the shear area percent（SA%） of low-temperature DWTT and toughness.
Study on High Temperature Oxidation Behavior of Typical Steel during 2250mm Hot Continuous Rolling
Xie Fenghu, Yang Huiping, Cao Xiao'en, Zhao Linlin, Su Zhenjun
2019, 40(4): 164-168. doi: 10.7513/j.issn.1004-7638.2019.04.030
Abstract(5) PDF(1)
Abstract:
The oxidation behavior of typical low alloy high strength steel QStE500 TM and pressure vessel steel Q345 R during 2 250 mm hot continuous rolling was studied by oxidation kinetics experiment.The results show that the growth of iron oxide scale complies with the parabola law.The oxidation activation energy of QStE500 TM steel is 161.766 kJ/mol,and the oxidation activation energy of Q345 R is 179.179 kJ/mol.The iron oxide scale shows a typical three-layer iron oxide scale structure.When the oxidation temperature is in the range of 700～800 ℃,the oxidation rate is very slow and the iron oxide scale is thin.When the temperature is higher than 900 ℃,the oxidation rate and the thickness of iron oxide scale increase sharply.
2019, 40(4): 169-170.
Abstract(21) PDF(1)
Abstract:

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