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Process on China titanium industry in 2019

Jia Hong, Lu Fusheng, Hao Bin

2020, 41(3): 1-7.

Abstract(226) PDF(39)

Abstract:

Structure-activity Relationship of Organic Amine Extractants and Their Solvent Extraction of Vanadium

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

2020, 41(3): 8-15. doi: 10.7513/j.issn.1004-7638.2020.03.001

Abstract(416) PDF(17)

Abstract:
The structure-activity relationship of organic amine extractants and their mechanism of solvent extraction of vanadium were analyzed.The results show that,organic amines,characterized by anion exchange and N atom as extraction functional group,belong to the alkaline extractants.Primary and tertiary amines are usually protonated in an acidic solution system to form the ammonium salts,while the quaternary ammonium salt does not require protonation.Primary amine,commonly used to extract vanadium from leaching solution of vanadium-chromium slag,can form a complex with hydrogen bonds to selectively extract vanadium preferentially,and the optimal extraction pH with a primary amine is generally less than 4.Tertiary amine can form an association with the vanadium-containing anion to extract vanadium,and the better extraction performance can be achieved at lower pH values.Especially,it shows excellent properties for extracting vanadium from leaching solution with high content of iron.However,tertiary amine also has disadvantages of small saturation capacity,large consumption and being liable to produce the third phase.The quaternary ammonium salt,the strong alkaline,can extract vanadium by ion exchange between vanadium anion and Cl^-,but quaternary ammonium salt has some disadvantages such as low saturation capacity and long phase separation time.The research progress of solvent extraction of vanadium by organic amine extractants was reviewed.Meanwhile,the future research directions including exploring of optimum extraction pH value,improving the performance of modifier,synergistic extraction with other extractants,optimizing the process before solvent extraction,strengthening mechanism research on solvent extraction of vanadium by amines,and developing new types of efficient and adaptable amine extractants,were proposed.

Experimental Study on Direct Acid Leaching of Vanadium-containing Steel Slag Using New Sulfuric Acid and Titanium White Waste Acid

Li Jun, Wu Enhui, Hou Jing, Xu Zhong, Huang Ping, Liu Qianshu, Jiang Yan

2020, 41(3): 16-22. doi: 10.7513/j.issn.1004-7638.2020.03.002

Abstract(241) PDF(5)

Abstract:
Direct acid leaching of vanadium-containing steel slag with new sulfuric acid and titanium white waste acid was carried out.The compositions and structure of the vanadium-containing steel slag were analyzed firstly.The results show that the vanadium-containing steel slag is mainly composed of Ca₂SiO₄,（MgO）_0.593（FeO）_0.407,Ca₃Fe₂（SiO₄）₃,Ca₃（V,Ti）₂O₇.Vanadium is dispersed in a variety of minerals in vanadium-containing steel slag.Relatively dense and large particle of vanadium titanium calcium oxide（Ca₃（V,Ti）₂O₇） is the main vanadium-enriched phase.It is hard to damage the structure of Ca₃（V,Ti）₂O₇ by direct acid leaching.To improve the leaching rate of vanadium,ball milling of the vanadium-containing steel slag is required.A lower content of vanadium is dispersed in dicalcium silicate,while V in the phase can be easily leached directly by the acid.79% of V is extracted by new acid direct leaching at optimum conditions of 200 r/min of stirring speed,30% of sulfuric acid concentration,65% of particles smaller than 124 μm,7∶1 of liquid-solid ratio and 1 h of leaching time.At the same conditions mentioned above,74% of V can be leached at 5∶1 of liquid-solid ratio using titanium white waste acid.Due to the high content of CaO and FeO,new sulfuric acid leaching of the slag will lead to a high cost.Titanium dioxide waste acid is a waste and cannot be directly discharged.Neutralizing the titanium white waste acid by vanadium-containing steel slag can greatly reduce the consumption of calcium carbonate for treating the waste acid.Simultaneously,vanadium can be extracted from the slag,realizing the high value utilization of the vanadium-containing steel slag.

Efficient Recovery of Ilmenite from Vanadium Bearing Titanomagnetite in Panxi Area

Wang Hongbin, Li Jin, Zhang Guohua

2020, 41(3): 23-29. doi: 10.7513/j.issn.1004-7638.2020.03.003

Abstract(328) PDF(10)

Abstract:
Aiming to solve the problems of low recovery rate,high cost and smaller particle size of products in recovering ilmenite from tailings of a vanadium bearing titanomagnetite in Panxi area via conventional process of strong magnetic separation-strong magnetic separation-flotation,an efficient process that recover ilmenite from coarse and fine tailings of vanadium bearing titanomagnetite separately by procedures of strong magnetic separation-gravity separation-electric separation and strong magnetic separation-strong magnetic separation-flotation was investigated.The results show that the ilmenite concentrate with 47.40% of TiO₂ content and 61.84% of recovery rate can be obtained.Compared with the conventional process of strong magnetic separation-strong magnetic separation-flotation,the ilmenite recovery rate of the tailings by the proposed process increases by about 14 percentage points and the cost per unit ilmenite concentrate as well as the content of particles less than 0.074 mm is respectively decreased by 50 RMB and 20 percentage points.The obtained products are more suitable for preparation of titanium white pigment by sulphate process and production of acid-soluble high titanium slag.

Main Phase Evolutions and Micro Zone Leaching Rate of Vanadium and Chromium in Sub-molten Salt Process for Vanadium Slag

Shi Zhixin, Gao Jian, Zhong Xiang

2020, 41(3): 30-35. doi: 10.7513/j.issn.1004-7638.2020.03.004

Abstract(246) PDF(4)

Abstract:
Based on the sub-molten salt process that vanadium and chromium in vanadium slag can be efficiently and selectivity converted into soluble salts at low temperatures,the main phase evolutions,occurrence and change laws of vanadium and chromium elements,and micro zone conversion rate of vanadium and chromium for vanadium-chromium slag before and after the sub molten salt reactions were studied.The results show that the vanadium-chromium spinel with lattice defects on the surface is more favorable for the lattice substitution of O^2- than the dense vanadium-chromium spinel,and the decomposition of vanadium-chromium spinel with the defects is accelerated.The recovery rate of Cr element before and after the sub-molten salt reactions is 99.63%,while the recovery rate of V element is 90.01%.The micro zone conversion rate of the main vanadium phases proves that the increase of vanadium content in Fe₂O₃ after the reactions of sub-molten salt is the main reason for the decrease of V recovery rate.

Co-extraction of Vanadium and Aluminum from Ferrovanadium Slag by Sulfuric Acid Roasting

Deng Xiaobo

2020, 41(3): 36-40. doi: 10.7513/j.issn.1004-7638.2020.03.005

Abstract(189) PDF(9)

Abstract:
Ferrovanadium slag generated from ferrovanadium production via electro-aluminothermic method contains high content of aluminum as well as vanadium with high utilization value.Based on the characters of the ferrovanadium slag,sulfuric acid roasting process was selected to extract vanadium and aluminum from the ferrovanadium slag.The effects of sulfuric acid to slag ratio,roasting temperature and time on extraction rates of vanadium and aluminum were investigated.Meanwhile,the sulfuric acid roasting mechanisms were also discussed.The results show that 72.5% of V and 68.3% of Al can be extracted from the slag at sulfuric acid to slag ratio of 1.4 mL/g,roasting temperature of 240 ℃ and roasting time of 90 min.With the advantages of high extraction efficiency and low roasting temperature,the proposed process provides a new utilization method for the ferrovanadium slag.

Experimental Study on Oxidation-reduction of Panzhihua Low Silicon Ilmenite Concentrate

Liu Xianghai

2020, 41(3): 41-46. doi: 10.7513/j.issn.1004-7638.2020.03.006

Abstract(178) PDF(2)

Abstract:
With Panzhihua low silicon ilmenite concentrate as the object,the effects of oxidation temperature and time on the phase structure and reduction properties of ilmenite were studied,and the weight loss rate as well as the metallization rate in reduction of the pre-oxidized ilmenite at different temperatures and time were analyzed.The results show that the oxidation of ilmenite concentrate can be completed in a short time.With the increase of oxidation temperature,the main phase change process of ilmenite concentrate is FeTiO₃→Fe₂O₃+TiO₂→Fe₂TiO₅+Fe₂O₃+TiO₂.The reduction temperature and time have a great influence on the metallization rate of ilmenite,and the effects are not obvious with the reduction temperature and time more than 1 300 ℃ and 8 h,respectively.The microstructure analysis shows that the aggregation of metallic iron occurs at high reduction temperatures,forming spherical and rod-shaped metallic iron particles with a size of about 10 μm.

Preparation and Electrochemical Performances of Vanadium or Nickel Doped Lithium Iron Phosphates

Liu Tiantian, Cui Xumei, Wang Ningjun, Li Nali

2020, 41(3): 47-52. doi: 10.7513/j.issn.1004-7638.2020.03.007

Abstract(394) PDF(7)

Abstract:
In this paper,the vanadium or nickel doped cathode material LiFePO₄ for lithium ion battery was synthesized by solvothermal method,using water/ethanol as the solvent.The crystal phases and microstructures of the samples were characterized by XRD and SEM,respectively.Furthermore,the electrochemical performances of LiFePO₄/carbon composites were studied by the methods of constant AC impedance and cyclic voltammetry.Through the constant current charge and discharge test,the results indicate that the difference between the charge and discharge voltage of the samples doped by vanadium and nickel ions is smaller than that of the undoped sample.The samples with 1% vanadium ion doping and 1% nickel ion doping respectively have an initial discharge specific capacity of 124.9 mAh/g and 113.5 mAh/g at 2.5～4.3 V,0.2 C and room temperature.And the sample with 1% vanadium ion doping has the best cycle performance with 114.4 mAh/g of specific discharge capacity and 91.59% of capacity retention rate after 50 cycles.The sample with 1% nickel ion doping has the highest initial discharge specific capacity of 103.1 mAh/g at 0 ℃.

Microstructure Evolution during Hot Rolling of TA1 Slab Produced by EB Furnace Smelting

Cui Yan, Sun Xinjun, Zhang Zhibo, Yong Qilong

2020, 41(3): 53-58. doi: 10.7513/j.issn.1004-7638.2020.03.008

Abstract(224) PDF(5)

Abstract:
The influences of hot rolling deformation temperature and single pass reduction rate on the microstructure evolution and recrystallization of EB furnace slab during hot rolling were studied by hot rolling experiments and microstructure observation.It is found that the grain size of EB furnace slab is hundreds of times larger than that of VAR forging slab after heating the slab before hot rolling,and the coarse grain structure of EB furnace slab is not conducive to recrystallization during hot rolling.By increasing the rolling temperature（≥ 850 ℃）,reducing the single pass reduction and decreasing the hot rolling deformation speed,the hot rolling structure can be fully recrystallized.The high-temperature start rolling,high-temperature finishing rolling and high-temperature coiling of thin slab were discussed to obtain a large proportion of recrystallization structure of the hot rolling coil,so that the traditional annealing recrystallization process of hot rolling plate can be omitted.It is found that when the hot rolling temperature is 850 ℃,there is a critical reduction rate（43.6%） for refining recrystallized grains.When the reduction rate is lower than 43.6%,increasing the reduction rate can significantly refine recrystallized grains in the hot rolling coil,which exceeds the critical reduction rate,and the recrystallized grain size in the hot rolling coil almost remains unchanged.When the hot rolling temperature is lower than 810 ℃,there is a critical reduction rate to start recrystallization nucleation.With the decrease of the hot rolling temperature,the critical reduction rate increases gradually.

Rolling Process Optimization of Vanadium Microalloyed Automobile Titanium Alloy

Sun Feng, Yin Xiaoli, Zhao Da

2020, 41(3): 59-63. doi: 10.7513/j.issn.1004-7638.2020.03.009

Abstract(291) PDF(4)

Abstract:
Rolling tests of Ti-Al-Mo-Cr-V automobile titanium alloy microalloyed with vanadium were carried out by different processes,and the mechanical properties were tested and compared.The results show that the start-rolling temperature and rolling deformation have obvious effects on the mechanical properties of the tested alloys.The mechanical properties of the tested alloys first increase and then decrease with the increase of starting rolling temperature from 945 ℃ to 1 045 ℃.With the increase of rolling deformation from 59% to 75%,the mechanical properties of the alloys present a sharp increase followed by a slow increase.The optimum start-rolling temperature and rolling deformation of the tested alloy are 1 020 ℃ and 67%,respectively.Compared with those of alloy at the starting rolling temperature of 945 ℃,the tensile strength and yield strength of the tested alloy at 1 020 ℃ respectively increase by 28 MPa and 34 MPa,with the section shrinkage decreased by 2.5%.Compared with those of the alloy at 59% of rolling deformation,the tensile strength and yield strength of the alloy at 67% of deformation increase by 23 MPa and 27 MPa respectively,with the section shrinkage decreased by 1.5%.

Optimization of Mechanical Milling Parameters of Negative Alloy for V-Ti Battery

Zhou Guozhu, Guan Xiaoqing

2020, 41(3): 64-68. doi: 10.7513/j.issn.1004-7638.2020.03.010

Abstract(206) PDF(4)

Abstract:
V-20.5 Ti-14 Ni-6 Co-4 Al battery alloy samples for negative electrode were prepared at different mechanical ball milling process parameters,and the charge-discharge cycle stability as well as the corrosion resistance of the obtained samples were tested and compared.The results show that the ball milling speed and time have a significant effect on the charge-discharge cycle stability and corrosion resistance of the alloys.With the increase of milling speed from 300 r/min to 700 r/min and the milling time from 2 h to 10 h,both of the charge-discharge cycle stability and corrosion resistance of the alloy increase first and then decrease.The ball milling speed and time of the alloy are optimized at 600 r/min and 6 h respectively.Compared with those of the alloy at the ball milling speed of 300 r/min,the decay rate of discharge capacity of the alloy at 600 r/min of ball milling speed decreases by 16% with the corrosion potential shifting positively by 81 mV.Compared with those of the alloy at the milling time of 2 h,the decay rate of discharge capacity of the alloy at the ball milling time of 6 h decreases by 18%,with the corrosion potential shifting positively by 116 mV.

Study on the Properties of Ti-Al-Nb Alloy

Liu Shulong, Gao Chao, Guo Minna, Yan Ping

2020, 41(3): 69-73. doi: 10.7513/j.issn.1004-7638.2020.03.011

Abstract(339) PDF(7)

Abstract:
The high temperature oxidation resistance and high temperature wear resistance of Ti-Al-Nb alloy samples with different contents of Al and Nb elements were tested,compared and analyzed.The results show that with the increase of Al content and Nb content,the mass gain per unit area and high temperature wear volume of the sample decrease first and then increase slightly,and the high temperature oxidation resistance and high temperature wear resistance increase first and then decrease slowly.The mass gain per unit area and high temperature wear volume of the sample with 14% Al content respectively decrease by 53.85% and 50% comparing with those of the alloy with 8% Al content.And the mass gain per unit area and high temperature wear volume of the sample with 35% Nb content respectively decrease by 43.75% and 41.38% comparing with those of the alloy with 20% Nb content.The Al content and Nb content of Ti-Al-Nb alloy are optimized at 14% and 35%,respectively.

Effect of Shaft Shoulder Diameter on Properties of Vanadium Titanium Nickel Hydrogen Storage Alloy Modified by Friction Stirring

Wang Donghui, Zhang Yonghong

2020, 41(3): 74-78. doi: 10.7513/j.issn.1004-7638.2020.03.012

Abstract(285) PDF(3)

Abstract:
Friction stirring modification experiments of V₃TiNi_0.56 hydrogen storage alloy with different shoulder diameters were carried out,and the microstructures and charge-discharge cycle stability were tested and compared.The results show that friction stirring modification can refine the grain size and improve the cycle stability of the alloy.When the shoulder diameter is at 8～12 mm,the average grain size and discharge capacity decay rate of the alloy decrease first and then increase,and the charge-discharge cycle stability of the alloy increases first and then decreases.Compared with the specimens without friction stirring modification,the average grain size of the alloy decreases by 48% and the discharge capacity decay rate decreases by 24% when the stirring head with a diameter of 10 mm is used for friction stirring modification.

Experimental Study on Durability of High Titanium Heavy Slag Recycled Concrete

Wang Wei

2020, 41(3): 79-83. doi: 10.7513/j.issn.1004-7638.2020.03.013

Abstract(229) PDF(5)

Abstract:
Replacing coarse and fine aggregates of high-titanium heavy slag with 50%,75%,and 100% replacement rates of coarse and fine aggregates of high-titanium heavy slag to prepare high-titanium heavy-slag recycled concrete with strength classes C20,C25,C30 was carried out,and the 28-day strength was measured.The durability of the samples was studied by resistance to chloride ion penetration test,rapid freeze-thaw test,and resistance to sulfate wet and dry cycle erosion test.The test results show that the measured strength of the recycled concrete decreases with increase of the replacement rate of the recycled aggregate,and the measured strength of each strength grade concrete can reach the design strength,but the strength margin is small.The D_RCM value of the recycled concrete decreases with increase of the replacement rate and strength of the aggregate.The minimum and maximum D_RCM values are 2.3×10^-12 m²/s and 3.3×10^-12 m²/s,respectively.The frost resistance of recycled concrete increases with gradual increase of the replacement rate of recycled bone and the strength grade,but only the C25 recycled concrete with 75% and 100% recycled aggregate and the C30 recycled concrete with 100% replacement reach the freeze-thaw rating of 100 freeze-thaw cycles.The effect of 30 sulfate dry-wet cycle erosions on the strength of recycled concrete is small.At the same strength level,the resistance to sulfate erosion of recycled concrete decreases with the increase of the replacement rate of recycled aggregate.The smaller the strength level,the smaller the decrease amplitude.

Influence of Vanadium-titanium Magnetite Tailings on Autoclaved Aerated Concrete Block

Shi Lei, Song Xiao

2020, 41(3): 84-89. doi: 10.7513/j.issn.1004-7638.2020.03.014

Abstract(203) PDF(3)

Abstract:
Aerated concrete blocks were prepared from vanadium-titanium magnetite tailings after iron separation from Chengde.The fineness and addition effects of tailing on dry density and compressive strength of samples were studied.The phase compositions and microstructures of samples by tailing addition were analyzed by XRD and SEM,and the water absorption and water resistance of the products were tested.The results show that the content of-0.074 μm particles reaches to 90.23% after 20 min of milling.Increasing the tailing fineness enhances the density of samples,and the dry density and compressive strength of samples firstly increase and then decrease with increasing tailing addition.Under the condition of tailing（grinding for 20 min）∶cement∶lime∶gypsum = 60∶20∶15∶5,the obtained aerated concrete block has a compressive strength more than 4.0 MPa and a dry density less than 595 kg·m^-3,which meets requirement of A4.5 grade of GB11968—2006 standard.XRD and SEM analysis show that adding 40%～60% tailing is beneficial to the formation of C-S-H gel and tobermorite,endowing the product with high strength,good water absorption and water resistance.

Experimental Study on Acid Leaching Purification of Titanium Gypsum

Shao Guoqing

2020, 41(3): 90-94. doi: 10.7513/j.issn.1004-7638.2020.03.015

Abstract(225) PDF(5)

Abstract:
The physicochemical properties of titanium gypsum were analyzed and a single factor experimental study on acid leaching purification was carried out.The effects of liquid-solid ratio,leaching time,concentration of leaching solution,leaching temperature and system pressure on the purification of titanium gypsum were studied.The results show that the optimum reaction conditions under normal pressure is determined as the following:liquid-solid ratio of 4,leaching time of 45 min,concentration of leaching solution at 15%,and leaching temperature of 65 ℃,and the removal rate of iron,aluminum,and magnesium is about 85%,56% and 91%,respectively.When the pressure of the reaction system increases to 2.0 MPa,the removal rate is further improved.It is found by analyzing the mineral micro-morphology,that the crystal form of calcium sulfate in the titanium gypsum after purification is not changed significantly,and that the iron hydroxide attached to the surface of the calcium sulfate crystal is removed effectively.Meanwhile,the content of iron,aluminum,and magnesium in titanium gypsum is decreased significantly after pressurized purification.

Application of Advanced Treatment of Coking Wastewater by Ozone Catalytic Oxidation

Zhou Mei

2020, 41(3): 95-98. doi: 10.7513/j.issn.1004-7638.2020.03.016

Abstract(255) PDF(7)

Abstract:
In order to meet the new environmental protection requirements and further improve the treatment level of coking wastewater,the coking wastewater treatment system of a plant in Panzhihua has been upgraded and optimized.The advanced purification treatment of wastewater has been strengthened by using ozone catalytic oxidation technology.Through the optimization of influent suspended solids,thiocyanate and hydraulic retention time,the operation and treatment capacity of the system has been greatly improved.The water quality is better than that of the direct discharge standard in Table 2 of GB16171—2012,with the amount of ammonia and nitrogen ≤ 1 mg/L,COD ≤ 70 mg/L.It presents an obvious effect in removal of polycyclic aromatic hydrocarbons and benzopyrene,with the color of the water obviously improved,indicating a well industrial operation effect.

Study on the Optimization of Fluidization Reduction Conditions of Brazilian Iron Ore Powder

Xu Qiyan, Li Zhiping, Gu Zhanghan, Yin Zhihong

2020, 41(3): 99-104. doi: 10.7513/j.issn.1004-7638.2020.03.017

Abstract(155) PDF(3)

Abstract:
The reduction behavior of Brazilian iron ore powder was studied in a pressurized visible fluidized bed.It was found out that the metallization rate was increased by increasing the pressure properly,and the fluidization state improved by adding carbon powder.In order to further optimize the effects of reduction time,reduction pressure,linear velocity of reduction gas,reduction temperature,carbon content and particle size on the reduction of Brazilian mineral powder,six factors and three levels orthogonal experiment method were used to test the bond ratio and metallization rate of Brazilian mineral powder samples after reduction.Experiments resultsindicated that different reduction conditions had different effects on the reduction of Brazilian mineral powder.Optimum reduction temperature of Brazilian ore powder by pure hydrogen was 923～1 023 K,the linear velocity of reduction gas was 0.6 m/s,the reduction time was 30～50 min,the reduction pressure was 0.25 MPa,the content of carbon powder was 2%～6%（accounting for the quality of ore powder） and the particle size of carbon powder was 4～7 μm.

Experimental of Gas-solid Decarbonization Process of Fe-C Alloy Ribbon in Medium Carbon Region

Chen Pengfei, Ai Liqun

2020, 41(3): 105-109. doi: 10.7513/j.issn.1004-7638.2020.03.018

Abstract(220) PDF(2)

Abstract:
In order to study the decarbonization development of iron-carbon alloy in carbon domain,an initial carbon fraction of 1.2% and 1.5 mm thick Fe-C alloy thin strip was used for this purpose.Decarbonization of the strip had been conducted in the form of interface gas-solid reaction.The P_H₂O/P_H₂ of the atmosphere in the furnace was controlled at 0.61 by adjusting the flow ratio Ar-H₂-H₂O.The experimental temperatures were set to 1 353 K,1 413 K and 1 453 K.And the decarburization time was set to 10～40 minutes.The results show that the decarbonization reaction of the strip is similar to that of the order reaction,and the activation energy is 68.85 kJ/mol.The limiting factor of the reaction is the diffusion of carbon in the thin strip.Tthe empirical formula for the average carbon content in the strip had been fitted and expressed as w_t=1.2e^{((0.148 82-1.28×10^-4T)t}.Increasing the decarbonization temperature can not only increase the decarbonization rate but also increase the limit decarbonization amount.With the increase of decarbonization time,the gradient difference of carbon concentration decreases and the diffusion stroke increases.The rate of decarbonization decreases gradually and appears obvious nodes.

Analysis on Microstructure and Strengthening Mechanisms of V-Ti Micro-alloyed HRB600 High Strength Steel Rebar

Yang Xiaowei, Chen Huande, Zhou Yun, Zhang Yu, Zhu Haitao, Xu Xia

2020, 41(3): 110-115. doi: 10.7513/j.issn.1004-7638.2020.03.019

Abstract(231) PDF(3)

Abstract:
Continues cooling phase transformation behavior and strengthening mechanisms of the V-Ti containing rebarsteel were systematically studied by thermal simulation testing machine,HR-TEM and OM.The result showed that the microstructure of used rebar was composed of ferrite and pearlite at 0.5～1.5 ℃/s cooling rate; the bainite transformation occurred and the ratio of bainite increased at 1.5～5 ℃/s cooling rate; the martensite structure appeared and gradually become the main structure at 5～25 ℃/s cooling rate.The strengthening mechanisms of V-Ti containing test steel were mainly precipitation strengthening and fine-grain strengthening,and V（C,N）+TiN mainly precipitated as rounded rectangle fine particles dispersing and its size was 10～60 nm.The V-Ti containing rebar was pilot-manufactured by using cooling rate of 1.0～1.5 ℃/s,which shows yield strength above 630 MPa,tensile strength above 820 MPa,elongation of 20%,maximum gross elongation of 11%,and the ratio of tensile strength and yield strength of 1.25.

Preparation of α-nanometer Iron Oxide by Microwave Hydrolysis

Zhang Yi, Lin Ling, Zhu Xuejun, Wang Jun, Deng Jun, Liao Ni

2020, 41(3): 116-121. doi: 10.7513/j.issn.1004-7638.2020.03.020

Abstract(252) PDF(7)

Abstract:
Herein,nano α-Fe₂O₃ was synthesized through microwave assisted hydrolysis method with FeCl₃ as raw material,triethylenetetramine（TETA） as ligand.The properties of the nano α-Fe₂O₃ products were analyzed and compared through laser particle size analyzer,FT-IR,and UV-Vis spectra.Microwave assisted hydrolysis method has advantages in yielding smaller and uniform nano particles in shorter time and without aging time.In the latter method,microwave heating time of 14 min and n_TETA∶n_FeCl₃=40∶100 are the best conditions,under which smaller and uniform nano α-Fe₂O₃ particles can be achieved.In the FT-IR spectra of nano α-Fe₂O₃,two characteristic absorption peaks at ca.580 and 480 cm^-1 red-shift with the particle size decreasing.Because of quantum size effect,blue shifting in the characteristic absorption peaks at ca.480 nm and ranging 330～350 nm in UV-Vis spectra depend on the decrease of the particle size.

Optimization of CaO/Al₂O₃ Ratio in Refining Slag for 12Mn Steel

Wang Xu, Wei Jun, Chou Shengtao, Li Zhaoling, Li Wei

2020, 41(3): 122-127. doi: 10.7513/j.issn.1004-7638.2020.03.021

Abstract(267) PDF(5)

Abstract:
By adjusting the slag system of 12 Mn steel refining and optimizing the CaO/Al₂O₃ratio,the desulfurization rate of the slag system is increased,the melting temperature is reduced,and the oxygen content in the steel is diminished.The results showed that the CaO/Al₂O₃ ratio decreased from the average value of 3.29 to 1.64,which caused the melting point decrease and the desulfurization rate increase.Finally,the effect of CaO/Al₂O₃ value in the range of 1.4～1.7 was verified by the desulfurization rate and oxygen content in steel.This study is of great significance to the adjustment of refining slag system of 12 Mn steel.

In-situ Observation on the Formation and Aggregation of Al₂O₃ Inclusions in Molten Steel

Shen Chang, Zheng Fuzhou, Chen Jie, Yang Zheng

2020, 41(3): 128-131,142. doi: 10.7513/j.issn.1004-7638.2020.03.022

Abstract(215) PDF(5)

Abstract:
The formation of Al₂O₃ inclusions,aggregation and movement of Al₂O₃ clusters to solid-liquid interface are observed by high temperature laser confocal microscopy.It is found outthat it takes only 1.5 s to form Al₂O₃ granulates and the Al₂O₃ granulates far from 145 μm apart gather into a 78 μm cluster spontaneously.It takes only 0.5 s for the aggregated Al₂O₃ cluster to be absorbed and moved from the suspension position in molten steel to the solid-liquid interface,the subsequently formed single Al₂O₃ particles are rapidly absorbed by the Al₂O₃ cluster,the Al₂O₃ cluster shrink to mass in 1 s.The theoretical analysis shows that the van der Waals force is the main force acting on the aggregation of Al₂O₃ inclusions and Al₂O₃ cluster adsorbed by solid-liquid interface,and the larger the size of inclusions.Greater the van der Waals force,results in faster movement of inclusions.The spontaneous shrinkage of Al₂O₃ clusters is mainly caused by the liquid bridge force.

High Temperature Mechanical Property of 09CrCuSb Steel Slab

Hu Hailiang, Zhu Liguang, Sun Ligen, Zhou Jingyi

2020, 41(3): 132-136. doi: 10.7513/j.issn.1004-7638.2020.03.023

Abstract(261) PDF(7)

Abstract:
The high temperature mechanical properties of 09CrCuSb steel billet were tested by the hot tensile test technique with Gleeble-3500 system.The stress-strain curve,high temperature strength,thermo-plasticity and plastic modulus with temperature in the range of 650～1 300 ℃were obtained.The results show that in the stress-strain curve,the peak stress decreases with the increase of the test temperature.When the test temperature is higher than 700 ℃,a stress platform appears in the stress-strain curve.The high temperature strength of continuous casting slab sample is poor,and with the increase of temperature,its high temperature strength tends to decrease.At the strain rate of 2.4×10^-3/s,there are two brittle temperature ranges.The range of brittleness temperature Ⅰ is 1 200 ℃～melting point,and he range of brittleness temperature Ⅲ is 700～800 ℃.In the range of 825～1 250 ℃, 09CrCuSb steel billet shows good thermoplasticity,and its section shrinkage rate is more than 80%.The high temperature plastic modulus of 09CrCuSb steel slab is less than 660.099 MPa when temperature is in range of 675～1 300 ℃.

Effect of Aging Treatment on Microstructure and Mechanical Properties of 06Cr15Ni5Cu2Ti Steel

Bai Qingqing

2020, 41(3): 137-142. doi: 10.7513/j.issn.1004-7638.2020.03.024

Abstract(219) PDF(3)

Abstract:
The effects of aging treatment on microstructure and mechanical properties of martensite precipitation hardening stainless steel 06Cr15Ni5Cu2 Ti were studied by means of phase diagram calculation,tension test,optical microscope,scanning electron microscope and transmission electron microscope.After solid solution at 1 000 ℃,the aging treatment was conducted at different temperature varying from 425 ℃ to 650 ℃.The results show that the steel has peak strength but minimum impacttoughness valueat aging temperature of 450 ℃.As the aging temperature increases,the strength of the steel decreases,but the impact toughness gradually increases.At aging temperature of 650 ℃,the lowest strength appears and the impact energy reaches the highest.This is mainly related to the occurrence of copper-rich phase and reverse transformation of austenite in the structure.Considering the strength and toughness,06Cr15Ni5Cu2 Ti steel can achieve a goodcombination of strength and toughness when it is aged at 500 ℃.

Effect of Sulfur Element on Microstructure and Magnetic Properties of the Finished Non-oriented Silicon Steel Sheets

Zhang Feng

2020, 41(3): 143-149. doi: 10.7531/j.issn.1004-7638.2020.03.025

Abstract(318) PDF(5)

Abstract:
Based on the industrial manufactured 0.25%Si non-oriented silicon steel sheets,the effect of sulfur concentration on microstructure and magnetic properties of the finished steel sheets was discussed,in order to find out the mechanism of sulfur element acting in non-oriented silicon steel sheets.The results show that when the sulfur concentration increases from 0.001 9% to 0.010 2%,there is a significant change of the morphology,size and number of the sulfides.The morphology of sulfide will change from capsular to ellipsoidal and then to spherical,and thus its type will change from the single MnS to the complex of MnS and Cu_xS,and then to single Cu_xS,respectively.The Cu_xS particles can pin the grain boundary and reduce the diffusion rate of grain growth effectively.Thus,fine grain segregation and island grain growth appear,which results in the heterogeneous distribution of fine grains.In a word,the magnetic induction of 0.010 2%S sample is superior to the 0.001 9%S sample,but the iron loss of which is inferior to the 0.001 9%S sample.Both of the difference value of eddy loss can keep steady,but the difference value of hysteresis loss will increase with the increasing of annealing temperature.This is the main factor causing the increase of total iron loss for 0.010 2%S sample.

Effect of Heat Treatment Process on Microstructure and Properties of 80 kg Hydropower Station Steel

Feng Lulu, Qiao Wenwei, Lu Xiuyu

2020, 41(3): 150-155. doi: 10.7531/j.issn.1004-7638.2020.03.026

Abstract(243) PDF(4)

Abstract:
The influence of heat treatment process on the microstructure and properties of 80 kg hydropower station steel was studied by optical microscope,tensile testing machine and low-temperature impact toughness testing machine.The microstructure changes of steel at different quenching and tempering temperature were analyzed.The mechanical properties changes of test steel under different heat treatment conditions wer also discussed.The results show that test steels under the low temperature quenching produces granular bainite and under high temperature quenching forms lath bainite.The dislocations formed during quenching merge and recombine and disappear,and the stress in quenching is released when the test steel is tempered at different tempering temperatures.With the increase of tempering temperature,the lamellar structure appeared merging and growing,and the ferrite volume fraction increased,and gradually transformed into polygonal ferrite.The yield strength firstly increases and then decreases and reaching its maximum value at 630 ℃ tempering temperature.Tensile strength decreases unilaterally and fails to meet requirement when the tempering temperature reaches 650 ℃.The percentage elongation and-40 ℃ low temperature impact toughness increases significantly at tempering stage.Thus quenching temperature has been proposed at 900～930 ℃ and tempering temperature at 600～630 ℃ for the best performance.

Influence Analysis of A356 Aluminum Alloy Forming Process Based on Ti Element

Zhao Liping

2020, 41(3): 156-160. doi: 10.7531/j.issn.1004-7638.2020.03.027

Abstract(193) PDF(2)

Abstract:
In view of the aluminum alloy is good process performance,based on the research,on the basis of A356 aluminum alloy solid forming for air processing for the A356 aluminum alloy shell of the robot design, adding titanium can effectively reduce the content of iron,to effectively control the number of iron-rich phase,acicular beta iron-rich phase in the composites gradually transformed into Chinese characters shape alpha iron-rich phase,at the same time,the size of the iron-rich phase decreased significantly; Tensile strength,yield strength increased significantly,plastic also increased.The results show that,with the increase of titanium element,the grain size of the alloy is obviously refined,and when it exceeds a certain value,the refining effect is obviously decreased. In the semi-solid isothermal treatment,the width and length of the i- ron-rich phase increase first and then decrease with the increase of temperature.The grain size also decrea- ses first and then increases with the increase of temperature. With the extension of isothermal time,the length and width of the iron-rich phase increase.The spheroidization of the unmelted primary phase showed an obvious trend when the isothermal time was prolonged or the refiner was added.

Research on Resistance Spot Welding Process of SAPH440 Pickled Plate

Yu Tengyi

2020, 41(3): 161-165. doi: 10.7531/j.issn.1004-7638.2020.03.028

Abstract(163) PDF(2)

Abstract:
The research object was SAPH440 pickling plate,the thickness was 2.0 mm.Comprehensively evaluated the mechanical properties of the joint by testing the shear and cross tensile properties,Axio Obersver A1 m optical microscope was used for microstructure and nugget diameter examination,and create spot welding process window.The result showed that,the pickling plate spot welding process window was 8.5 kA to 12 kA with a width of 3.5 kA,the nugget diameter and mechanical properties were positively correlated with welding current,when expulsion appeared,the nugget diameter and mechanical properties of the joint decreased slightly.The microstructure of nugget zone and HAZ were both martensite.Due to the influence of welding heat cycle,the structure morphology of the nugget zone was coarse and columnar,and the structure of HAZ was fine and needle-like.

Analysis and Control of Transverse Crack on Surface of ER70-Ti Welding Wire Steel Billet

Zhu Liguang, Zhang Xiaoshi, Liu Zengxun, Wang Xingjuan, Po Zhanlong, Zhang Mingbo, Kang Aiyuan

2020, 41(3): 166-171. doi: 10.7513/j.issn.1004-7638.2020.03.029

Abstract(203) PDF(2)

Abstract:
In the process of producing ER70-Ti titanium-containing welding wire steel billet in Chengde Iron and Steel Company,serious transverse cracks occurred in the slab.In order to find out the causes of lateral crack defects,the solidification characteristics of ER70-Ti steel were analyzed by FactSage thermodynamic simulation software,and the characteristics of steel itself,mold flux and continuous casting process parameters were analyzed.The measured melting rate of the mold flux is 145 s by using a fully automatic slag melting point melting rate tester.The measured viscosity is 0.71 Pa·s by using a rotational viscometer and the heat flux density is 184 kW/m² measured by an infrared heat transfer system.This kind of slag with slow melting rate and poor heat transfer control effect seriously affects the thickness of slag layer and the uniformity of slag melting.By changing the basicity,carbon content and carbon distribution mode of the mold flux,and the heat flux density of the mold flux is reduced to 118 kW/m²,the speed is increased to 55 s as well.After adjusting the mold flux,U the surface quality of the billet is obviously improved.

Study on Fracture Failure of 40Cr Screw Shaft

Dong Xuejiao, Yang Dawei, Liu Jinyan, Liu Zhaohua, Huang Jie

2020, 41(3): 172-176. doi: 10.7513/j.issn.1004-7638.2020.03.030

Abstract(206) PDF(6)

Abstract:
The early fracture failure of 40 Cr screw shaftoccurred in a water treatment station of a factory after service for 4 years.The fracture causes were analyzed by chemical composition analysis,mechanical properties detection,scanning electron microscope and optical microscope.The results show that the fracture originates from the root of second threads,and the multi pass welding is causing fatigue fracture.The microstructure of core part of the shaft is composed of pearlite+net-like ferrite,which come from original structure without quenching and tempering treatment.Its mechanical properties and fatigue strength cannot meet the requirements.The fatigue source exists hard brittle martensite structure,which is in combination with alternating stress due to eccentric movement of shaft causing the crack to rapidly expand to fracture.

2020 Vol. 41, No. 3