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Recovery of Titanium from Spent SCR Catalyst by Sodium Roasting

Jia Xiumin, Chen Tianbao, Huang Yong, Liu Huiwu, Liu Zhongchen, Li Peiyou, Xiang Qiulin

2020, 41(6): 1-5. doi: 10.7513/j.issn.1004-7638.2020.06.001

Abstract(222) PDF(6)

Abstract:
Titanium was recovered from spent SCR catalyst by sodium roasting.The effects of sodium dosage,roasting temperature,roasting time,material particle size and sulfuric acid concentration on titanium leaching rate were studied.From the experimental results,the optimum roasting conditions were selected at the alkali dosage of 1.2 times of the theoretical value,the roasting temperature of 700 ℃,the roasting time of 3 h,and the material particle size of -150 μm.The roasting clinker after washing was leached by sulfuric acid with 45% mass concentration,resulting in more than 89% of the titanium leaching rate.Titanium dioxide was prepared by hydrolysis of the leaching solution,with the titanium precipitation rate and purity of titanium dioxide more than 93% and 93%,respectively.

Leaching Kinetics of Ilmenite in Sulfuric Acid Solution

Wang Haibo, Wu Xiaoping, Gao Jian, Wang Bin, Cheng Xiaozhe

2020, 41(6): 6-10. doi: 10.7513/j.issn.1004-7638.2020.06.002

Abstract(405) PDF(26)

Abstract:
Using Panzhihua ilmenite and sulfuric acid as raw materials,the leaching kinetics of the ilmenite in sulfuric acid was studied,and the ilmenite coupled with the leaching residue was characterized by SEM,mineral analyzer and XRD.The research results show that at the reaction temperature of 83 ～ 111 ℃,the acid concentration of 23.5% ～ 45.8% and the acid-ore ratio of 6.2 ∶ 1,the leaching reaction is under the unreacted shrinking core model,with a mixed control step and 62.2 k J/mol of the activation energy.The ilmenite mainly exists as a separate phase or mixed state with other phases.Except for small part of ilmenite with a smooth surface,most of the ilmenite has a honeycombed surface,after the acid leaching.The ilmenite ore,primarily composed of ilmenite phase,has the limestone and quartz phases exposed after acid leaching.

Study on Reducing the Loss of Titanium Liquid Entrained in Ferrous Sulfate Filter Cake

Zheng Chenggang, Liu Juexin, Ye Shichao

2020, 41(6): 11-15. doi: 10.7513/j.issn.1004-7638.2020.06.003

Abstract(262) PDF(6)

Abstract:
Adopting the technical route of experimental research combined with the industrial production,this paper determined the solubility of ferrous sulfate in water to explore its crystallization kinetics characteristics and investigate the filter cake liquid content with different crystal sizes.Simulation and prediction for the ferrous sulfate crystallization via the current vacuum adiabatic cooling batch crystallization process with seed crystal added were carried out,and the working equations of systematic vacuum degree,crystallization temperature,cooling rate and evaporation rate were obtained.The whole crystallization process does not produce new crystal nuclei,realizing the rapid growth of crystals.The crystal size of controlled crystallization is increased by 3.8 times than that of the current process.The amount of titanium liquid entrained in the filter cake is reduced by 48%,which effectively reduces the loss of titanium liquid.

Deoxidization Technology for Aerospace Grade Vanadium Aluminum Alloy

Chen Haijun, Shi Qihua, Yin Danfeng, Gao Leizhang

2020, 41(6): 16-20. doi: 10.7513/j.issn.1004-7638.2020.06.004

Abstract(263) PDF(16)

Abstract:
The oxygen content in aerospace-grade vanadium aluminum alloy has an important effect on the properties of downstream titanium alloy materials.Aiming at the problem of high oxygen content in vanadium aluminum alloy prepared by aluminothermic smelting,the occurrence state of oxygen in V-Al alloys was confirmed by thermodynamic analyses.The oxygen in Al V85 preferentially combines with Al to generate α-Al₂O₃and then unites with V to form VO.The oxygen in Al V55 will combine with Al in the alloy to form α-Al₂O₃.The optimum conditions of vacuum deoxidation were obtained by orthogonal tests.At superheat of 60℃,vacuum degree of 1 000 Pa,degassing time of 5 min,argon blowing and stirring for 2 min,the oxygen content of vanadium aluminum alloy can be decreased from 0.15%to 0.009 89%,satisfying the Gf E requirements of aerospace-grade vanadium aluminum alloy.

Production Technology of Upscale FeV50 Alloy

Li Dongming, Yu Jiyang, Jia Ligen, Wang Fang, Lu Yongjie, Qin Yunquan

2020, 41(6): 21-25. doi: 10.7513/j.issn.1004-7638.2020.06.005

Abstract(262) PDF(4)

Abstract:
Based on the electro-aluminothermic process for FeV50 alloy production,the influencing factors on Al and P content in FeV50 alloy and the causes of the oxidation surface of the alloy were analyzed.The technical parameters for production of upscale FeV50,with w(Al) ≤ 1.0%,w(P) <0.06% and without oxidation surface,were determined.For controlling the P content in the alloy,the P content in iron filings as the raw material,the slagging agent and vanadium pentoxide should be controlled ≤ 0. 7%,<0.06% and <0. 015%,respectively. The aluminum addition coefficient of 0. 505~0. 510 is benificial to Al control in the alloy.A natural cooling of 36 h after smelting can avoid oxidation surface of the alloy.Production practice shows that the implementation of the above process parameters can achieve the stable production of upscale FeV50 alloy meeting the needs of users.

Preparation of NH₄VO₃ by Carbonation Leaching of Calcium Vanadate

Fu Zibi

2020, 41(6): 26-29,34. doi: 10.7513/j.issn.1004-7638.2020.06.006

Abstract(331) PDF(17)

Abstract:
In view of the problems of high Na/V ratio and low vanadium concentration of carbonation leaching solution of calcium vanadate,a new method of preparing ammonium metavanadate by mixed leaching of sodium bicarbonate and ammonium bicarbonate was proposed.The effects of the leaching agent compositions,CO₃^2-/Ca²⁺,leaching temperature and liquid-solid ratio on the leaching effect were studied.The results show that under the conditions of Na HCO₃∶NH₄HCO₃=1∶1,CO₃^2-/Ca²⁺=1.1,leaching temperature of 90℃and liquid-solid ratio of （4～5）:1,the leaching solution with 43.87～54.57 g/L of vanadium concentration and the vanadium leaching rate of 97.80%～98.01% can be obtained.Ammonium metavanadate is precipitated by ammonium bicarbonate in the leaching solution,and the vanadium precipitation rate is 91.31%.The vanadium product meets the quality control index requirements.

Effect of Zn on Catalytic Performances of Industrial V-Mo/Ti De-NO_x Catalyst

Zong Yuhao, Huang Li, Chang Zhengfeng, Wang Hu, Zhou Jun, Li Jinke

2020, 41(6): 30-34. doi: 10.7513/j.issn.1004-7638.2020.06.007

Abstract(260) PDF(4)

Abstract:
Different contents of Zn was loaded on V-Mo/Ti catalyst by impregnation method,and the activity of selective catalytic reduction of NO by NH₃ was evaluated.The catalysts were characterized by XRD,N₂ adsorption-desorption,NH₃-TPD,H₂-TPR and NO-TPD.The results show that Zn loading does not change the crystal structure of V-Mo/Ti catalyst,but reduces the specific surface area and reduction performances of V-Mo/Ti catalyst.Furthermore,Zn loading reduces the acid content as well as the NO adsorption performance of the catalyst,decreasing the catalytic denitration performances of the catalyst.With 0.5 mol/L H₂SO₄ solution for washing the Zn poisoned catalyst,the Zn loaded on the catalyst can be effectively removed.

Preparation of Non-stoichiometric Titanium Dioxide/Carbon Nanofiber Electrode and Its Performance for Supercapacitor

Ren Yaqi, Lü Yiying, Li Xi, Wang Rui

2020, 41(6): 35-39. doi: 10.7513/j.issn.1004-7638.2020.06.008

Abstract(236) PDF(3)

Abstract:
An integrated non-stoichiometric titanium dioxide/carbon nanofiber electrode was prepared by electrospinning-impregnating-calcination method and used for supercapacitor.Fine TiO₂ nanoparticles were anchored onto the surface of carbon nanofiber substrate with the diameter of 80～100 nm.And non-stoichiometric TiO₂nanoparticles were obtained by calcination at high temperature in inert atmosphere.The sample calcined at 900℃exhibits the highest capacitance with 222.81 F/g discharge capacitance at 0.2 A/g current density,and good cycle stability with 92%retention rate at 2 A/g current density after 6 000 cycles.

Effect of Stirring Rate on Corrosion Resistance of Ni-Sn/TiO₂ Composite Coating Prepared by Electrodeposition

Cui Pengfei, Zhang Kaiyi, Zhou Zongyi, Li Yungang, Yang Haili

2020, 41(6): 40-44. doi: 10.7513/j.issn.1004-7638.2020.06.009

Abstract(268) PDF(5)

Abstract:
The Ni-Sn/TiO₂ composite coatings were prepared by electrodeposition. The effects of stirring rate on surface morphology,composition and corrosion resistance of Ni-Sn/TiO₂ composite coatings were studied by scanning electron microscopy,energy dispersive spectroscopy,Tafel curve and electrochemical impedance spectroscopy.The results show that with the increase of stirring rate,TiO₂ content in the coating first increases and then decreases.When the stirring rate is 40 r/min,the maximum content of TiO₂ is obtained.Meanwhile,there is no crack on the surface of the coating,and the grains are fine and evenly distributed.According to Tafel curve and electrochemical impedance spectroscopy analysis,with the increase of stirring rate,the corrosion resistance of the coating is improved first and then weakened.When the stirring rate is 40 r/min,the coating possess the most positive corrosion potential,the lowest corrosion current density,the largest charge transfer resistance,and the best corrosion resistance.

Hollow 3D rGO/P-HC/TiO₂ for Photocatalytic Degradation of Ammonia Nitrogen

Wang Min, Xia Lixin, Lin Qingxian

2020, 41(6): 45-51. doi: 10.7513/j.issn.1004-7638.2020.06.010

Abstract(249) PDF(6)

Abstract:
In this work,a series of catalyst were successfully fabricated via hydrothermal method,which were used as efficient UV light photocatalytic degradation of ammonia nitrogen from aqueous solution.The surface properties of the catalysts were characterized by scanning electron microscope（SEM）,X-ray diffraction（XRD）,the Brunauer-Emmett-Teller（BET） method and UV-vis-DRS spectroscopy（DRS） technique.The comparison of photocatalytic performance among HC,P-HC,rGO/P-HC,TiO₂,P-HC/TiO₂,rGO/TiO₂ and rGO/P-HC/TiO₂ was carried out.The influences of the dosage of catalyst,the solution p H and ammonia nitrogen concentration on the degradation process were also investigated.It is shown that the ammonia nitrogen removal rate first increases and then decreases with the increase of catalyst dosage.And the removal rate reaches the highest at p H = 8. The as-prepared rGO/P-HC/TiO₂ catalyst shows a much higher photocatalytic activity for degradation of ammonia nitrogen than other catalysts,with the removal efficiency reached 93.0%.In cycle availability experiments,the rGO/P-HC/TiO₂ exhibits outstanding recycle activity and stability in ammonia nitrogen oxidation reaction under UV and sun light.The prepared catalysts are promising for the degradation of ammonia nitrogen from water resource.

Preparation of High Temperature Sensible Heat Storage Material from Vanadium Extraction Tailings and Graphite

Po Rongxun, Li Xuan, Li Guowei, Zhao Junquan, Luo Weidong, Deng Liyun, Guo Anfen

2020, 41(6): 52-59. doi: 10.7513/j.issn.1004-7638.2020.06.011

Abstract(229) PDF(2)

Abstract:
The high temperature sensible heat storage material was prepared via powder metallurgy method,using the iron extraction tailing obtained by carbothermal reduction of the vanadium extraction tailing as the raw material and graphite as the modifier respectively.XRD results show that the main phases of the thermal storage material include Na_6.65Al_6.24Si_9.76O₃₂,aluminosilicate,ilmenite and graphite.With increase of the graphite content,both of the density and hardness of the thermal storage material decrease,while the thermal conductivity increases.The DSC results show that the specific heat capacity is higher in the medium and high temperature region above 500℃.It is shown that the heat storage density of the sensible heat storage material is 223 k J/kg at 500～750℃,with the heat storage capacity of 0.062 k Wh/kg and the mass required for 1 000 k Wh heat storage of 16 000 kg.The thermal storage material prepared in this study has good thermal storage capacity at temperatures above 500℃,which can be used in high temperature thermal storage system.

Performance Optimization of Negative Electrode Material for Vanadium-based Nickel Metal Hydride Battery Based on Neural Network Algorithm

Wang Hong, Wang Qunqun

2020, 41(6): 60-65. doi: 10.7513/j.issn.1004-7638.2020.06.012

Abstract(194) PDF(3)

Abstract:
The neural network model with 6×36×12×1 four-layer topological structure was used to optimize the performances of the negative electrode material of vanadium based hydrogen storage battery.The input layer parameters were titanium content,nickel content,aluminum content,chromium content,holding temperature and holding time.The output layer parameters were charge and discharge cycle stability.The results show that the model has strong prediction ability and high prediction accuracy,with an average relative training error of 4.8%and an average relative prediction error of 4.9%.Compared with the existing V₃Ti Ni_0.56material,the capacity decay rate of V₃Ti Ni_0.56Al_0.3Cr_0.4material optimized by neural network model after 30 charge-discharge cycles is reduced from 61%to 26%.

Beneficiation of a Vanadium-titanium Magnetite in Panxi

Li Jinlin, Li Weiwei, Zhu Yongtao, Wu Xuehong

2020, 41(6): 66-73. doi: 10.7513/j.issn.1004-7638.2020.06.013

Abstract(335) PDF(11)

Abstract:
Taking a vanadium-titanium magnetite in Panxi as the research object,a beneficiation test was carried out for the titanium magnetite and ilmenite.The titanium magnetite was recovered by the process of pre-throwing tailings followed by two-stage grinding and magnetic separation,and the iron concentrate with a yield of 19.78%,a TFe grade of 55.34% and a TFe recovery rate of 51.27% can be obtained finally.The tailings of iron beneficiation contain a large amount of ilmenite,and the TiO₂ grade can be increased from 9.38% to 21.58% by two stages of iron removal and strong magnetic processes.The flotation process was used to further improve the TiO₂ grade. Through the process of floating sulfur-desliming-one rough and three concentration,qualified titanium concentrate with a yield of 9.53%,a TiO₂ grade of 47.45%,and a TiO₂ recovery rate of 47.87% can be obtained.

Mineral Processing Test on Olivine Type of Vanadium-titanium Magnetite in Panxi Hongge Area

Chen Tao, Hu Zhibo, Chen Cheng, Zheng Yu, Ying Hongwei, Deng Hao

2020, 41(6): 74-80. doi: 10.7513/j.issn.1004-7638.2020.06.014

Abstract(242) PDF(6)

Abstract:
In this paper the olivine type of vanadium-titanium magnetite had been analyzed by X-ray fluorescence spectrum and X-ray diffraction spectrum to identify the raw ore mineral compositions. The main valuable metal elements in raw ore are iron and titanium,thus comprehensive utilization of iron and titanium can be considered.The main useful minerals are chlorite（from olivine and feldspar to chlorite）,amphibole and sphenite,and a small amount of pyroxene,quartz and mica present.The iron component in raw ore is mainly magnetic iron,which is concentrated in titanomagnetite,while titanium is concentrated in ilmenite.Crushing results of raw oreshow that the distribution of iron and titanium of each grain grade is relatively uniform,but the TiO₂,TFe and MFe of fine grain grade（-0.038 mm） are relatively low.Based on raw ore nature,the step grinding experiment to separate iron was carried out.The results show that after using the magnetic separation column for selection,the iron concentrate TFe grade can reach to 55.62%,the recovery rate can reach to 50. 12%. The effective recycling of iron in Olivine type of Vanadium-Titanium magnetite in Hongge can be achieved.The two-stage weak magnetic separation tailings are fed as titanium separation,and the titanium concentrate is recovered,which achieve comprehensive utilization of raw ore.

Study on Process Mineralogy of Baima Iron Concentrate

Yang Daoguang

2020, 41(6): 81-87. doi: 10.7513/j.issn.1004-7638.2020.06.015

Abstract(167) PDF(5)

Abstract:
Taking the raw ore,concentrate and tailings from Baima concentrate in Panxi zone as the research object,the chemical elements,mineral compositions and monomer dissociation degree of the samples were analyzed by means of chemical analysis and AMICS.The content of titanomagnetite,ilmenite and gangue,the degree of dissociation of titano-magnetite monomer,the main loss of Fe and change of titanium content were investigated when the grade of Baima iron concentrate was raised to 59%. The main reason for the difficulty in reducing TiO₂ content in the extracted Baima iron concentrate is that the lamellar ilmenite and fine acicular ilmenite spinel present in the form of micro fine inlay.

Study on Process Mineralogy of a Titanium Magnetite in Ankang Area

Hui Bo, Yang Yaohui, Chen Wei, Deng Bing

2020, 41(6): 88-93,123. doi: 10.7513/j.issn.1004-7638.2020.06.016

Abstract(161) PDF(4)

Abstract:
The process mineralogy characteristics of a titanomagnetite in Ankang region were studied by means of X-ray fluorescence spectrometry（XRF）,optical microscope,scanning electron microscope（SEM）,X-ray energy spectrum probe（EDS）,etc.The chemical analysis results of the crude ore show that the main elements available for beneficiation and recovery in the ore are titanium and iron,with grade of 20.9% and 7.67% respectively. Mineral identification results show that the mineral types are mainly titanomagnetite（16.8%）,ilmenite（8.81%）,sulfide（1.10%）,gangue minerals（73.29%）. The particle size characteristics of mineral technology show that the particle sizes of useful minerals titanomagnetite,ilmenite and sulfide are mainly in the range of 500 ～ 100 μm,which are closely linked in different forms.Equilibrium of? elements show that the theoretical grade of iron and titanium are 52. 44% and 47. 83%,respectively,and the distribution rates of iron and titanium are 41.65% and 54.30%,respectively. The factors affecting the beneficiation indexes are clarified,which provides a theoretical basis for the formulation of a reasonable beneficiation and metallurgy process.

Experimental Study on Decarburization of Iron-carbon Alloy Sheet under CO-CO₂ Atmosphere

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

2020, 41(6): 94-98. doi: 10.7513/j.issn.1004-7638.2020.06.017

Abstract(158) PDF(2)

Abstract:
In order to study the effect of temperature,holding time and thickness of steel sheet on decarburization of Fe-C alloy sheet in CO-CO₂ atmosphere,the experiments were carried out in a weak oxidation atmosphere of Ar-CO-CO₂ on 2 mm,1.5 mm and 1 mm thick Fe-C alloy sheet with initial carbon content of 4.2%. As decarburization temperature increases,both decarbonization amount and decarburization rate increase. When decarburization time extends,the decarburization amount increases. Decarburization rate is faster in the early stage of decarburization.The decarbonization rate of thin sheet with 1 mm thickness can reach 92% at 1 413 K for 60 min.The thickness of strip had a significant effect on decarburization.Given the same holding time,The decarburization effect of 1 mm strip is better than those of 1.5 mm strip and 2 mm sheet. As the decarburization time prolongs,the thickness of ferrite region increases,and the mass fraction of carbon near the reaction interface decreases.

Industrial Test of Titanium Powder and Pulverized Coal Co-injection

Dong Yafeng, Guo Peimin, Liu Keming, Zhai Dan

2020, 41(6): 99-106. doi: 10.7513/j.issn.1004-7638.2020.06.018

Abstract(213) PDF(2)

Abstract:
Titanium powder and pulverized coal co-injection is the process in which rich titanium powder is mixed with raw coal and injected into blast furnace through tuyeres.The industrial test of titanium powder and pulverized coal co-injection was carried out in a 2 500 m³ blast furnace to verify the practical effect.The experimental result showed that the process can be carried out by the existing PCI system.The [Ti] in hot metal reached 0.13% when the injection TiO₂ was 3.7 kg/t,while the same percent of [Ti]in hot metal needed 7.7 kg/t TiO₂ being added from the top of the furnace as titanium ore.The reduction utilization rate of TiO₂ from titanium-coal mixture was obviously higher than that of the titanium ore.The temperature difference of the cooling water in the second section of the hearth remained stable during the test.The maintenance of the lower part and the bottom of the hearth needs more integrated measures.

Strengthening Mechanism and Mechanical Behavior of Low Carbon Microalloyed Steel Containing Ti

Guan Jianhui, Zhang Jiming, Sun Lin, Qu Jinbo, Yang Guanlin

2020, 41(6): 107-111. doi: 10.7513/j.issn.1004-7638.2020.06.019

Abstract(394) PDF(7)

Abstract:
Microstructure and strengthening mechanism of low carbon micro-alloyed steel with different contents of titanium were characterized by OM and SEM analysis and tensile and impact testing.With the increase of titanium content,the strength and yield ratio of the tested steel increased,while the elongation decreased.When the titanium content increased from 0.016% to 0.137%,the yield strength increased from 327 to 710 MPa,increasing by 383 MPa,while the tensile strength increased from 418 to 773 MPa,increasing by 355 MPa.When the effective titanium content in the ranges of 0 ～ 0.052% and 0.052% ～ 0.107%,the increments of yield strength for each 0.01% of effective titanium content are roughly 44 MPa and 21 MPa,respectively.

Study on Thermal Recycling of LF Refining Slag

Li Shujun, Du Xueyan

2020, 41(6): 112-118,134. doi: 10.7513/j.issn.1004-7638.2020.06.020

Abstract(327) PDF(6)

Abstract:
In this paper,ithe thermal recycling of LF furnace refining slag for the production of non-low silicon aluminum killed steel was studied.Slag samples and liquid steel samples were taken from LF refining furnace,and the changes of compositions of liquid steel and quantity density of inclusions in LF refining furnace were analyzed.The research results show that under the condition of adjusting the basicity of LF refining slag without adding lime,the content of S in the molten steel exceeds the requirements of the internal control components when recycling for three times,the CaO content in the refined slag is controlled at more than 43.58%,and the basicity R₂ is controlled at more than 8.58,which can meet the desulfurization requirements of the molten steel by the recycling of LF hot refining slag.With the increase of the recycling times of the refined slag,the adsorption capacity index of the refined slag to the inclusion in the liquid steel decreased obviously,and the adsorption and removal efficiency of the refined slag to the inclusion in the liquid steel decreased.

Experimental Study on the Effect of Rare Earth on Inclusions in High-sulfur Free-cutting Steel

Fan Lei, Li Chen, Jiang Maofa

2020, 41(6): 119-123. doi: 10.7513/j.issn.1004-7638.2020.06.021

Abstract(263) PDF(4)

Abstract:
In order to explore the effect of rare earth on inclusions in high-sulfur free-cutting steel,the high temperature simulation experiments and thermodynamic analysis were carried out in this work.The results showed that the types of inclusions were MnS and CeAlO₃.MnS could precipitate on the surface of CeAlO₃to form complex inclusions,and the proportions of complex inclusions was about 3.01%.When the content of Ce was 0.05%,the main types of inclusions were MnS,Ce₂S₃ and CeAlO₃.MnS could wrap with Ce₂S₃ to form complex inclusions,and its proportions was about 5.11%.With the content of Ce increasing from 0.01%to 0.05%,the typeⅡchain-like MnS in steel significantly reduced,and the size of sulfide decreased.

Study on the Transformation and Precipitation Behavior of Ferrite at Different Positions in High-rise Building Steel

Zheng Feifan, Zhang Caijun, Wu Shaowen, Li Kangkang

2020, 41(6): 124-129. doi: 10.7513/j.issn.1004-7638.2020.06.022

Abstract(199) PDF(3)

Abstract:
The phase transformation and precipitation behavior of acicular ferrite in high-rise construction steel was observed in situ by high temperature laser confocal microscope.According to its nucleation site the ferrite can be classified into crystal interface,grain boundary edge and inclusions.The nucleation position and growth rate of acicular ferrite were analyzed theoretically. The following conclusions are drawn:1) the growth rate of grain boundary ferrite is inhomogeneous and the growth process deflects; 2) Three kinds of nucleation positions of ferrite and the sequence of ferrite precipitation were found; 3) finally,the growth characteristics of ferrite precipitated at different positions were revealed by in-site observation.

Effect of Annealing Temperature on Microstructure,Mechanical Properties and Retained Austenite of 1 000 MPa Q＆P Steel

Lu Qianqian, Gu Hairong, Cui Lei, Xiao Yangyang, Leng Deping

2020, 41(6): 130-134. doi: 10.7513/j.issn.1004-7638.2020.06.023

Abstract(332) PDF(9)

Abstract:
In this work effect of annealing temperature on microstructure,mechanical properties and retained austenite of 1 000 MPa Q＆P Steel were studied by means of SEM,EBSD,XRD and tensile test at room temperature.Results showed that the microstructure at room temperature was mainly composed of ferrite（F） + martensite（M） + retained austenite when the experimented steel was anneal at 800 ～900 ℃.With the increase of annealing temperature,the volume fraction of martensite increased,and the appearance of the internal lath of martensite became clearer.With the increase of annealing temperature,the volume fraction of retained austenite increases. The more grain boundaries,the denser the retained austenite. When anneal at 850 ℃,the best match of strength and plasticity of resulted steel was achieved,with the tensile strength of 991.33 MPa and the elongation of 18.58%,meeting the Q＆P 980 standard requirements.

Modified Morphology of Mn S Inclusions in Tellurium Treated 303Cu Stainless Steel

Li Jie, Zhu Qiangbin, Tian Qianren, Fan Tian, Xie Jianbo, Fu Jianxun

2020, 41(6): 135-141. doi: 10.7513/j.issn.1004-7638.2020.06.024

Abstract(266) PDF(10)

Abstract:
In order to study the influence of tellurium on the morphology of MnS inclusions in 303Cu freecutting stainless steel,various amount of tellurium was added into 303Cu steel,and then the morphology and distribution of MnS inclusions in steels was analyzed by means of OM,SEM and microelectrolysisdding.It was found out that with tellurium addition into 303Cu stainless steel,the number of small-size inclusions in steel decreased,while the number of large-size inclusions increased,and the average equivalent diameter and average area of the inclusions increased. Inclusions modification was achieved the best effect when 0.036 0% tellurium was added.Telluride mainly attached to the surface of MnS inclusions in low-tellurium steel,while MnS inclusions were completely surrounded by telluride in high-tellurium steel.After treated by tellurium,the inclusions in steel were modified from chains and strips into spindles and spheres,which was beneficial to the improvement of mechanical properties and cutting properties.After tellurium was added,the hardness of the inclusion and the matrix firstly increased and then decreased.When the tellurium content was 0.018 0%,the hardness of the matrix and the inclusion reached the maximum values of 209.6 HV10 and 200.3 HV10,respectively.

Ca Treatment Effect on the Evolution and Microstructure of Ti Alloyed Inclusions in HG785 Steel

Zhao Huanling

2020, 41(6): 142-150. doi: 10.7513/j.issn.1004-7638.2020.06.025

Abstract(194) PDF(2)

Abstract:
To reveal the inclusion evolution and its influence on the inner microstructures of high strength steel treated by Ti alloying Ca,we used scanning electron microscope and energy dispersive spectroscopy to characterize the inclusion characteristics and its induction to ferrite behaviors.We compared the effects of different types of inclusions on ferrite-induced microstructure improvement,and combined with thermodynamic calculations,discussed the evolution mechanisms of inclusions during aluminum deoxidation,Ti alloying,and calcium treatment.The experimental results show that with the addition of Al,Ti and Ca alloys,the content of inclusions have changed significantly.With the increase of deoxidation time（5 min,10min,15 min）,the content of dissolved oxygen in the steel decreases.After adding Ti,the content of TiO_x in the inclusion also decreases.Sufficient Ca content can change the high-melting inclusions of Al-Mg-TiO in the steel into the low-melting liquid inclusions of Al-Mg-Ti-O,and the reduced Ti will eventually remain in the inclusions or diffuse into the molten steel.Under the conditions of this study,the appropriate Al-Ti deoxidation time interval of is more than 10 min,which can improve the yield rate of Ti.The thermodynamic calculation shows that Al₂TiO₅ is more easily modified by Ca into low melting calcium aluminate,rather than Al₂O₃.To avoid Ca S and Ti N precipitation in the liquid phase,[S]＜0.002 4%and[N]＜0.005 8%should be made.Compared with other types inclusions in steel,Al-Mg-Ti-Ca-O+Mn S+Ti N is more likely to induce acicular ferrite precipitation.

Effect of Inclusions on High Cycle Fatigue Characteristics of Spring Steel

Liu Yong, Tian Zhiqiang, Ma Chao, Zhao Haitao, Chen Hongwei, Ceng Yanan, Feng Qian

2020, 41(6): 151-157. doi: 10.7513/j.issn.1004-7638.2020.06.026

Abstract(343) PDF(9)

Abstract:
In this paper the size and quantity of inclusions in different parts of spring steel slab and steel was determined by using Aspex inclusion automatic scanning electron microscope,and the fatigue properties of the materials were tested using a rotating bending fatigue tester.The rules of the distribution of inclusions in steel was revealed,and the influence mechanism of different defect forms and distributions of steel on the failure of materials was analyzed.The results show that when the rotation bending fatigue limit is σ_-1= 764 MPa,the ratio of fatigue limit to tensile strength is 0.45.Fatigue failure occurs at a lower cycle（＜10⁶）,when the average size of inclusions is greater than 24.9 μm and is distributed near the surface of the steel.

Effect of FTSR Hot Rolling Process on Microstructure and Mechanical Properties of 65Mn Strip

Li Xiujing, Wang Shuhua, Zhang Xing, Li Hongwei

2020, 41(6): 158-163. doi: 10.7513/j.issn.1004-7638.2020.06.027

Abstract(278) PDF(6)

Abstract:
Microstructure and mechanical properties of FTSR 65Mn steel strips produced by different hot coiling technologies was investigated,and simulated quenching heat-treatment were carried on. The result shows that ferrite reduces in term of its volume fraction and finically disappears with coiling temperature going down from 740 ℃ to 600 ℃,but the pearlite size and space decrease,and strength and hardness of resulted 65Mn strip increase. When the strip is heated at 850 ℃,the coarsing of transformed austenite grain is retarded,and the size of grains is directly affected by primary pearlite. Industrial quenching process based on experiment is suitable for strip production of the required performance,and the hardness of strip surface after quenching is above 53 HRc.

Experimental Research on Microstructure and Properties of a 9%Ni-Fe Alloy Laser Cladding Coating

Liu Xiyan, Jiang Wei, Wang Shuqi, Cui Xianghong

2020, 41(6): 164-169. doi: 10.7513/j.issn.1004-7638.2020.06.028

Abstract(212) PDF(3)

Abstract:
In order to improve the hardness and heat resistance stability of H13 steel surface,a 9% Ni-Fe alloy coating was prepared on the surface of H13 steel by laser cladding technology.Microstructure,phase composition,and micro-hardness of the alloy coating and thermal stability was investigated by X-ray diffraction（XRD）,metallographic microscope,scanning electron microscope（SEM）,energy spectrometer（EDS）,micro-hardness tester and other experimental instruments.The results show that the cladding layer is well bonded to the substrate without presence of defects such as cracks and pores. From the cladding layer to the matrix,the solidified structures arechanging from equiaxed,dendritic,columnar to cellular.The coating phase is mainly composed of α-Fe and some intermetallic compound reinforcing phases,and its content is beyond XRD detection. The micro-hardness of the coating after cladding has reached 1.5 to 2 times of the matrix structure,and the increase in hardness has significantly strengthened the matrix. The coating has good thermal stability and is the most stable at 400 ℃ .The Fe-based alloy coating can significantly improve the hardness and thermal stability of H13 steel and extend its service life.

Study on the Properties of a New Type of Mechanical Die Steel Containing Titanium

Ding Xiangqin, Ji Shijun

2020, 41(6): 170-174. doi: 10.7513/j.issn.1004-7638.2020.06.029

Abstract(166) PDF(3)

Abstract:
In this paper,a new type of mechanical die steel specimens containing titanium with different titanium contents were prepared,and their wear resistance at room temperature,high temperature wear resistance and high temperature oxidation resistance were tested and analyzed.The results show that with the increase of titanium content from 0 to 0.10%,wear volume and weight gain per unit area of mechanical die steel samples at both the room temperature and high temperature decrease firstly and then increase,while wear resistance and high temperature oxidation resistance increase firstly and then decrease slowly.When the content of titanium is 0.06%,the wear volume and weight gain per unit area of the mechanical die steel sample at both room temperature high temperature are the smallest,which are 8×10^-3mm³,13×10^-3mm³ and 3.2 g/cm²,respectively,decreasing by 38.46%,53.57%and 33.33%respectively compared with titanium free steel.The optimal titanium content for the new developed mechanical die steel is at 0.06%.

Analysis on Notch Sensitivity of Low Thermal Expansion Superalloys GH2909

Chen Qi

2020, 41(6): 175-180. doi: 10.7513/j.issn.1004-7638.2020.06.030

Abstract(371) PDF(19)

Abstract:
Superalloy GH2909 bars produced by a Chinese supplier present high notch sensitivity during high temperature creep performance test.In order to understand the reason for this issue,the imported and studied GH2909 alloy bars had been compared in terms of their chemical compositions,microstructures and mechanical properties,and the microstructure development of studied alloy during processes from forging to heat treatment had been investigated as well.Chemical composition analysis results showed there was no apparent difference between imported and studied alloys.However,microstructure observation indicated two alloys present remarkable difference.For the studied alloy,the notch sensitivity is attributed to the random distribution of Laves phase inside the grain,which is expected to be caused by the inappropriate forging process.Based on the research results,an improved forging process was proposed. By increasing the final forging temperature,controlling recrystallization of the alloy and precipitating Laves phase along the grain boundary,a new GH2909 alloy bar with suitable microstructure and excellent properties was successfully prepared,and the problem of notch sensitivity of domestic GH2909 alloy bar was solved.

2020 Vol. 41, No. 6