钢铁钒钛

2017, 38(3): 1-7.

Abstract(47) PDF(14)

Abstract:

2017, 38(3): 163-164.

Abstract(39) PDF(1)

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Experimental Study on Separation of Iron and Titanium from Vanadium-titanium Iron Concentrate by Hydrochloric Acid Leaching at Atmospheric Pressure

Wu Enhui, Hou Jing, Li Jun, Huang Ping

2017, 38(3): 8-12. doi: 10.7513/j.issn.1004-7638.2017.03.001

Abstract(89) PDF(7)

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The elements of vanadium-titanium iron concentrate were selectively leached by hydrochloric acid at atmospheric pressure,and the effects of liquid-solid ratio,leaching temperature and time,and hydrochloric acid concentration on the leaching rate of iron and titanium dioxide （TiO₂） were studied. Furthermore,the microstructure,morphology,size and elements distribution of the leaching residue were also investigated. The results show that the magnetite phase is destroyed by hydrochloric acid leaching and obvious pulverization is discovered on the surface of leaching residue,with Fe entering into the leaching solution. However,the ilmenite phase has not been destroyed and still exists in the leaching residue. The optimal leaching conditions are as follows: 18.6% of hydrochloric acid concentration,leaching at 85 ℃ for 60 min,and 9:1 of liquid-solid ratio.At the optimal conditions,the leaching ratio of Fe and TiO₂ are 85.41% and 7.22%,respectively. The yield of leaching residue is 27% and the grade of TiO₂ in the leaching residue is about 34%.

Preparation of Ammonium Polyvanadate Using High Concentration of Vanadium Solution Containing Sodium

Guo Jike

2017, 38(3): 13-20. doi: 10.7513/j.issn.1004-7638.2017.03.002

Abstract(123) PDF(11)

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In order to resolve the technological problems of precipitation of ammonium polyvanadate （APV） by ammonium salts under acid conditions using high concentration of sodium-containing vanadium solution,the dripping method was adopted to prepare APV under acid conditions with the high concentration of sodium-containing vanadium solution as raw material. The results show that through the dripping method the precipitation rate of vanadium is more than 99% with 50.51% of vanadium,0.089% of Na₂O and 0.074% of sulphur （S） in the obtained APV,under the conditions of 2.30 for reaction pH,90 ℃ of reaction temperature,ammonium addition coefficient K = 1.0 and 10% of addition amount for A seed crystals. After calcination,the quality of obtained vanadium pentoxide （V₂O₅） satisfies the requirements of YB/T5304—2011 standard. This new method can realize the production capacity enhancement and decrease the energy consumption,wastewater treatment burden and production cost significantly.

Hydrothermal Synthesis of Titanium Dioxide and Its Photocatalytic Properties Evaluation

Pu Hong

2017, 38(3): 21-24. doi: 10.7513/j.issn.1004-7638.2017.03.003

Abstract(213) PDF(4)

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Titanium dioxide （TiO₂） photo-catalyst was prepared via hydrothermal route from industrial titanyl sulfate solution. The obtained samples were characterized by SEM,FT-IR,XPS,nitrogen absorption-desorption test and the photocatalytic properties of the photo-catalyst were also evaluated. The results indicate that the prepared TiO₂ possesses relatively higher photocatalytic activity,with an approximate photocatalytic degradation activity as P25 to methylene blue. With increase in temperature,the degradation rate in selective catalytic reaction for NO increases first and then gradually decreases,and the highest degradation rate of 84.14% can be obtained at 450 ℃. The particle size of the catalyst is 0.36~1.08μm,and its specific surface is 90.47 m²/g.

Selection of Fatty Acids as Reagent for Vanadium Removal from Crude Titanium Tetrachloride

Du Ming

2017, 38(3): 25-29. doi: 10.7513/j.issn.1004-7638.2017.03.004

Abstract(72) PDF(3)

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The experiments of refining titanium tetrachloride using different fatty acids were carried out,and the samples of purified titanium tetrachloride and tailing slag for vanadium removal were analyzed.The results show that with saturated fatty acids as reagent the vanadium removal efficiency is lower and the tailing slag has an excellent dispersibility. In addition,the length of carbon chain of saturated fatty acids scarcely affects the vanadium removal efficiency. The efficiency of vanadium removal by unsaturated fatty acids owning the same carbon chain length with saturated fatty acids,is more higher than that of saturated fatty acids,while the slurry for vanadium removal is more viscous and prone to agglomeration. Using mixed fatty acids as the reagent can not only guarantee the vanadium removal efficiency but also obtain the tailing slag with excellent dispersibility.

Study on Particles Residence Time Distribution in Low-temperature Chlorinator

Li Dongqin

2017, 38(3): 30-33. doi: 10.7513/j.issn.1004-7638.2017.03.005

Abstract(62) PDF(3)

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Based on the cold model of low-temperature chlorination furnace for Pangang titanium-bearing blast furnace slag,the conductivity method was employed to research the pulse tracer particles,and the effects of internal baffles,feed rate and apparent gas velocity on the particles Residence Time Distribution （RTD） in the low-temperature chlorination furnace were investigated. The results show that the baffles lengthwise separate the internal space of the furnace to eliminate short circuits,which is beneficial to efficiently mixing between the particles and fluidized gas. The RTD of carbonized slag in the furnace is more concentrated with double baffles （variance σ_t² reduces to 0.50 from 0.67）. When the feed rate decreases from 1.9 to 1.1 g/s the average residence time of the material doubles and the reaction time of carbonized slag increases. With the apparent gas velocity increased to 0.15 m/s,the concentricity of RTD for carbonized slag is weaken to some extent,but the contact and reaction between the particles and gas is enhanced by back-mixing which insures the fluidization conditions of the materials and is in favor of improving the chlorination efficiency of carbonized slag.

Effect of Sand Milling Times on the Quality of TiO₂ Initial Product

Wang Haibo, Chen Xinhong, Wu Xiaoping, Wang Bin, Luo Zhiqiang

2017, 38(3): 34-37. doi: 10.7513/j.issn.1004-7638.2017.03.006

Abstract(65) PDF(4)

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The influence of sand milling times on the quality of titanium dioxide （TiO₂） initial product was investigated by horizontal sand mill,using roll milling TiO₂ product as raw material and zirconia beads with different sizes as grinding media. The results show that with increase of sand milling times the pH and viscosity of the slurry are not changed substantially,particle size D₅₀ decreases and the ratio of particles with size ≤1 μm increases gradually. Meanwhile,the length-diameter value of particles in the slurry decreases slowly with the degree of sphericity gradually improved,the quantity and size of the aggregates decreased,and the value of whiteness L and brightness for the obtained TiO₂ increased step by step. TiO₂ initial product with more uniform size distribution,higher value of whiteness and brightness can be obtained using 0.4mm zirconia beads,compared with those of the product prepared by 0.6 mm and 1.8 mm zirconia beads.

Study on H₂TiO₃-lithium Exchanger Synthesized by Precipitation-peptization Method

Yao Qianqian, Zhou Jiabei, Zhang Liyuan, Yang Shuang, Zhou Dali

2017, 38(3): 38-44. doi: 10.7513/j.issn.1004-7638.2017.03.007

Abstract(133) PDF(6)

Abstract:
A novel inorganic precipitation-peptization method was proposed to synthesize Li₂TiO₃ in this work.TiOSO₄ and CH3COOLi were employed as lithium and titanium sources respectively,and H₂O₂ was used as complexing agent resulted in titanium-lithium sol system via precipitation-peptization method,and then H₂TiO₃-lithium adsorbent was obtained by drying,calcining,treating with hydrochloric acid successively. The effects of preparation conditions on the stability of the sol system,the morphology and properties of the xerogel and Li₂TiO₃ were investigated by FTIR,TG-DSC,XRD,SEM,ICP,Zetasizer Nano and rotary viscosimeter. The research results indicated that a stable sol system with viscosity 7.3 m Pa·s and the Zeta potentials（-29.5m V） could be prepared after aged 24 hours under the conditions of using CH₃COOLi as lithium source,the value of pH about 7,Ti₄⁺ concentration 0.2 mol/L. The complex peroxide exist in this system can be proved through analyzing the bonding of the xerogel by infrared spectrum. Better calcining temperature and time of the dry gel was 750 ℃,2 h respectively,and β-Li₂TiO₃ was obtained under this condition. β-Li₂TiO₃ was further treated with hydrochloric acid （0.2 mol/L） to obtain H₂TiO₃-lithium absorbent,and finally the Li+drawn out ratio from β-Li₂TiO₃ reaches 85.31%,the adsorption capacity comes up to 27.15 mg/g.

Experimental Study of Vacuum Electromagnetic Levitation Refining of TiAl Intermetallic Alloy

Ma Lan, Yang Shaoli, Piao Rongxun, Zhong Kaiwen

2017, 38(3): 45-51. doi: 10.7513/j.issn.1004-7638.2017.03.008

Abstract(45) PDF(1)

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Refining of crude Ti Al based alloy which was obtained through aluminothermic reduction of acid-soluble titanium slag in Panzhihua was carried out using vacuum electromagnetic levitation melting furnace. Phase composition,distribution of alloy elements in micro area,microstructure and impurities content of the alloy before and after refining were studied in present study. It is found that when the refining parameters of melting current,holding time and cooling rate were respectively 60 A,5 min and 4 A/min,the lamellar structures,amount of cracks and grain size of the alloy after refining decreased. Si and Fe presented in the phases of TiAl and TiAl₂ etc. by substituting Al element to form substitutional solid solution phases,and eventually formed the phases of Fe₂AlTi,Si₂Ti,Al₂FeSi,AlFe and FeTiSi etc.,close to the double phase structure of Ti-Al binary alloy. The inclusions content in the alloy reduced by 45% and inclusions with size more than 5 μm were removed by refining.

Preparation of Li₄Ti₅O₁₂/C Composite and Its Application to Anode Material of High Rate Lithium-ion Battery

Meng Weiwei

2017, 38(3): 52-56,77. doi: 10.7513/j.issn.1004-7638.2017.03.009

Abstract(85) PDF(4)

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The Li₄Ti₅O₁₂/C （LTO/C） composite with excellent rate performances was synthesized via a facile hydrolysis reaction followed by a low temperature heat treatment. In the hydrolysis process,the introduction of cetyltrimethylammonium bromide （CTAB） as a surfactant can significantly improve the rate performances of Li₄Ti₅O₁₂/C composite as anode material for lithium ion battery （LIB）. The specific capacities of the obtained composite at charge and discharge rates of 0.5,1,2,5 and 10 C were respectively 162,154,121,80 and 60 m Ah/g,which was apparently larger than those of the Li₄Ti₅O₁₂/C by physical mixing processes. The Li₄Ti₅O₁₂/C prepared with CTAB also showed excellent cycling stability at high rate,attributed to its larger diffusion coefficient of lithium ion （8.97 × 10^-13cm²/s）,smaller charge-transfer resistance Rct （35.2 Ω） and volume resistance Rs （6.8 Ω） than those of the composite by physical mixing. Therefore,this study has important theory significance and practical application value.

Effect of WC Powder Size on the Microstructure and Properties of Ti（C,N）-based Cermets

Wu Yuemei, Li Bin, Wang Xinling, Xiong Ji

2017, 38(3): 57-62. doi: 10.7513/j.issn.1004-7638.2017.03.010

Abstract(38) PDF(1)

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Mo₂C is normally added to improve the wettability between Ti （C,N） and Ni in Ti （C,N）-based cermets. Due to the increasing price of Mo₂C,much attention has been paid to Ti （C,N）-based cermets with WC addition. In this paper,the effect of WC powder size on the microstructure and properties of Ti(C_0.7N_0.3)-15% WC-15% Ni cermets free of Mo₂C was studied. The experimental results show that the cermet with smaller size of WC powder addition presents a white core and grey rim structure,and the grains have smaller size （average grain size is below 2 μm） and a uniform size distribution. Furthermore,the ultra-fine WC powder can not only raise its own dissolution rate but also that of Ti （C,N）. Although the ultra-fine WC powder can increase the hardness of the cermet,it makes the fracture toughness of the cermet have a reduction.

Influence of Welding Parameters on Microstructure and Mechanical Performance of Gr1 Titanium Plate

Zang Wei, Zhang Hangyong, Yuan Xueting, Guo Longchuang, Guo Xinhu

2017, 38(3): 63-66. doi: 10.7513/j.issn.1004-7638.2017.03.011

Abstract(35) PDF(1)

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Gr1 titanium plate is commonly used for explosion metal clad plates. Great area plate needs to be tailor-welded. In order to ensure plasticity of Gr1 titanium plate satisfy requirements for subsequent explosive cladding process,different welding parameters and wire-feed modes are chosen for tailor-welding 5.5 mm Gr1 titanium plate. Through the comparative analysis of metallography,hardness,tension and bend,influence of different process parameters on the weld structure and mechanical properties are investigated. The results show that self-fusion tailor-welding without welding wire under the welding conditions of I = 90 A,U = 10 V,v = 4.8 mm/s can achieve significant fraction of fine α grains and good comprehensive mechanical performance at the weld. Tailor-welding Gr1 titanium plate can meet the requirements for explosion metal clad plate.

Effects of Solidification Mode on Electrochemical and Hydrogen Storage Properties of Vanadium-based Alloy

Wu Ling

2017, 38(3): 67-70. doi: 10.7513/j.issn.1004-7638.2017.03.012

Abstract(49) PDF(1)

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The vanadium-based hydrogen storage alloy V₃TiNi_0.56Cr_0.4 was respectively prepared by solidification modes of air cooling,water cooling and liquid nitrogen cooling,and the electrochemical and hydrogen storage properties of the obtained alloy were tested and analyzed. The results show that solidification mode has evident effects on the electrochemical and hydrogen storage properties of the alloy. Respectively using air cooling,water cooling and liquid nitrogen cooling,the discharge capacity of the alloy after charge-discharge cycles for 20 times is decayed by 84%,73% and 38%,while the maximum hydrogen uptake at room temperature can reach to 1.467%,1.514% and 1.832%,respectively.

Study on the Flotation Separation of Modified Ti-bearing Blast Furnace Slag

Zhang Shiqiu, Wang Weiqing, Zheng Yu, Ren Pengkun, Yan Wu, Deng Jie

2017, 38(3): 71-77. doi: 10.7513/j.issn.1004-7638.2017.03.013

Abstract(60) PDF(4)

Abstract:
In order to achieve the high-efficiency recovery of titanium component in the titanium-blast furnace slag,the slag had been modified in terms of its chemical compositions and treated through the process of high temperature selective precipitation. The maximum crystal size and quantity of the resulted pervoskte was 63.17 μm and 30.62%,respectively. Based on the previous results,the study on the flotation of the modified slag had been carried out,including the effect of OHA dosage and sodium silicate dosage. It is found out that the OHA dosage and sodium silicate dosage do not affect the flotation obviously.SEM and EDX analysis show that the CaSO₄ micro-precipitate covers the surfaces of the minerals,which decreases the effect of OHA and sodium silicate. Therefore,the effective surface treatment agents should be developed to preprocess the modified slag prior to flotation separation.

Experimental Study on the Preparation of Porous Ceramic with Vanadium Tailings by Casting Method

Li Liang, Peng Fuchang

2017, 38(3): 78-82. doi: 10.7513/j.issn.1004-7638.2017.03.014

Abstract(43) PDF(1)

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Vanadium slag can be utilized as the main raw material,binder,clay,water reducing agent and pore forming agent has been added for,preparing vanadium slag porous ceramics via injection molding process. The obtainedporous ceramic filter can be used in chemical industry,furnace insulation and building decoration industry. In this paper the effect of the calcination temperature,the binder content,the heat preservation time,the clay content,the pore forming agent content,and the effect of pore forming agent on the properties of porous ceramics were investigated. It is found out that combined selection of aluminate cement as binder with~6% addition,calcination temperature of 1 050 ℃,and holding period of 4~6 h,10% clay and 100 mL/150 g raw material of pore forming agent,the satisfied porous ceramic can be obtained.

Parameters Optimization of Composite Sintering Titanium Magnetite Concentrate

Rao Jiating, Hu Peng, Qin Xingguo, Lin Wenkang

2017, 38(3): 83-87. doi: 10.7513/j.issn.1004-7638.2017.03.015

Abstract(42) PDF(1)

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Composite sintering process had been investigated on the high titanium magnetite concentrate in order to address the issues of low-strength,high-return-rate and low-yield of sinter,adopted. It is found out that mix moisture has the greatest effect on the integrated index,followed by height of material layer. Compared with that of referenced sintering process,utilization coefficient with optimal sintering increases by more than 20%,and sinter strength and product rate increase by 3% and 5%,respectively.The volume fraction of ferrite in sinter increases by 4%~5% and metallurgical properties of sinter is improved at the different degrees.

Study on the Influence of Basicity and Roasting Temperature on the Strength of the Pellets

Pan Xiangyang, Long Yue, Xu Chenguang, Ma Baoliang, Dou Guanxiong, Zhao Bo

2017, 38(3): 88-93. doi: 10.7513/j.issn.1004-7638.2017.03.016

Abstract(117) PDF(2)

Abstract:
The Tangshan local magnetite and high calcium powder mixing and balling,thermodynamic simulation with X-ray diffraction analysis,high temperature thermal analysis instrument,while the use of Fact Sage,studying on laws of basicity and temperature effects on the strength of the pellets. The results showed that with the increase of basicity,the strength of the pellets was increased and then decreased trend changes,and when the basicity is 1,calcination temperature controlled at 1250 ℃ of pellet roasting ball strength reaches the maximum. Appropriate amount of liquid phase contributes to Fe³⁺ migration,hematite crystallized the strength of the pellets is larger; the excess phase blocking Fe³⁺ migration,hematite recrystallization is restricted,reduce the strength of the pellets.

Forecast for Low Temperature Reduction Disintegration Properties of Vanadium-titanium Sinter Based on BP Neural Network

Xin Zicheng, Li Jie, Liu Weixing, Yang Aimin, Zhang Yuzhu, Wang Lili

2017, 38(3): 94-99. doi: 10.7513/j.issn.1004-7638.2017.03.017

Abstract(51) PDF(1)

Abstract:
In order to improve the RDI_+3.15 of vanadium-titanium sinter,BP neural network algorithm was applied to the prediction of low temperature reduction degradation of vanadium-titanium sinter. The samples of the indicator data were divided into input samples and output samples,the input samples includes carbon,basicity,w （Mg O） and FMG ore,and the output sample was low temperature reduction degradation of vanadium-titanium sinter. The relationship between input samples and output samples was explored by using BP neural network algorithm. The results show that BP neural network model is suitable for studying on the low temperature reduction disintegration properties of sinter. It can predict the output samples effectively according to the input samples,and the average relative error is 5.7%,meeting the requirement of prediction precision in engineering practice,which provides guidance for the production of vanadium-titanium sinter.

Effect of Grinding Mode on Hematite Pellet Properties

Jiao Guoshuai, Ju Jiantao, Ma Jie, Xing Xiangdong

2017, 38(3): 100-105. doi: 10.7513/j.issn.1004-7638.2017.03.018

Abstract(76) PDF(3)

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The main purpose of this paper is to solve the problem of how to meet the high requirement of hematite pullets process by simulation of the grate-klin process,hematite pullets were researched by different pressed ways. The results showed that it has a poor preheating properties. The compression strength meets requirement with preheating and roasting temperature reachs over 1 075 ℃ and 1 280 ℃. The preheating and roasting temperature decreased obviously by grinding the hernatite,it also show the same affection on roasting and preheating time. During the pullets production,the hernatite being processed by high pressure grinding roller,the roasting and preheating temperature decreased for 60 ℃ and 70 ℃,reduce roasting time for 2 min. With a being grindinghernatite,the roasts process gets a improvement of specific surface and size distribution,which are the main factors affect the microstructure and macro strength of the pullets.

Influence of TiO₂ on Mineral Structure and Metallurgical Properties of Blast Furnace Slag

Han Kaibin, Liu Lei, Li Zhiwei, Han Xiuli

2017, 38(3): 106-110. doi: 10.7513/j.issn.1004-7638.2017.03.019

Abstract(48) PDF(1)

Abstract:
The mineral structure of blast furnace slag with different mass percent of TiO₂ （7%~16%）was studied by means of polarization microscope. The results indicate that the microstructure of blast furnace slag is mainly porphyritic or porphyritic-like texture. Phenocryst minerals mainly consist of the rich titanium diopside and melilite,and its matrix is composed by glass,titanaugite,perovskite,and a small amount of metallic iron,titanium nitride,titanium carbide and their solid solution. As the mass percent of TiO₂ increases,the content of the rich titanium diopside and titanaugite reduces first and then increases,while the content of the melilite increases first and then decreases. When the mass percent of TiO₂ reaches to 12%,the content of titanium nitride,titanium carbide and their solid solution increases. These highmelting point compounds resulted in higher viscosity and melting temperature of blast furnace slag,and the liquidity of blast furnace slag also became worse.

Quantitative Research on Cleanliness of Unsteady Casted IF Steel Slabs

Xiao Pengcheng, Zhu Liguang, Liu Haichun, Tian Fengji, Liu Zengxun, Li Meng

2017, 38(3): 111-117139. doi: 10.7513/j.issn.1004-7638.2017.03.020

Abstract(47) PDF(1)

Abstract:
By means of T[O] and [N]measurement,metallographic observation and sample-electrolyzing,the cleanness of normal slabs and unsteady cast slabs of IF steel produced in a plant had been compared. Normal slabs have very high cleanness,where the w（T[O]） is 11 × 10^-6,w（N） is 18 × 10^-6 and the mean number density of micro inclusions is 4.0 per mm²,the fraction of inclusions over 50 μm is 2.10 mg/kg. But the unsteady continuous cast slabs contain much more inclusions. The cleanness of the first slab is worst because of the serious re-oxidation. The slabs were polluted by the slag or mold powder due to the lever fluctuation in the tudish or the mold while changing ladle or SEN. The last slab of the tudish was polluted both by the air re-oxidation and the slag entrapments. The distribution of micro inclusions shows that the maximum number of inclusion is found at the 1/4 width of the slab,while 1/2 width appears minimum amount of inclusion. Along the thickness direction,the number of inclusion near the inner and outer surfaces of the slab are obviously higher than those of central area.

Simulation Optimization Research of Tundish under Different Pull Speeds

Sun Hua, Sun Yanhui, Huang Bo, Zhang Xichao, Bai Xuefeng

2017, 38(3): 118-123. doi: 10.7513/j.issn.1004-7638.2017.03.021

Abstract(48) PDF(1)

Abstract:
In this paper,asymmetric tundish of three-strand casting construction model for different speeds and the existence of dam had been investigated. In order to further improve the production capacity of the tundish of electric furnace factory,a water simulation and numerical simulation scheme was designed for three-flow asymmetric tundish. Through numerical simulation on velocity field and temperature field and water model at different casting speeds,it can be found that increase casting speed,will lead to decrease the dwell time of the three nozzles,and the time for three nozzles is different After dam installation,the decrease of dwell time with casting speed becomes small. The distribution of flow field and temperature filed do not vary with casting speed,however,increasing casting speed will increase the flow and temperature of liquid steel in tundish.

Research on Tempering Performance of Seismic Steel with Yield Strength 550 MPa

Zhang Liqin, Tong Mingwei, Wu Kaiming

2017, 38(3): 124-129. doi: 10.7513/j.issn.1004-7638.2017.03.022

Abstract(54) PDF(1)

Abstract:
Effects of tempering temperature on microstructure,precipitation and mechanical properties of Seismic building steel with yield strength of 550 MPa produced by TMCP,were researched by optical microscope,TEM and mechanical properties test. The results show that with the increase of tempering temperature,both yield strength and tensile strength of the test steel increase,and the ratio of R_p0.2/R_m increases obviously. The changes of mechanical properties before and after tempering are mainly related to the precipitation of fine particles below 25 nm size,the decomposition of M/A islands and the recovery of dislocation substructure after tempering. When the tempering temperature is 450 ℃,the best comprehensive mechanical properties of the tested steel are achieved with tensile strength at 703 MPa,yield strength at 588 MPa,elongation of 17.5% and impact energy at-20 ℃ reaching 240 J,as well as lower R_p0.2/R_m of 0.84.

Effects of Controlled Rolling and Cooling Technology on Microstructure and Performance of 900 MPa Grade Hot-rolled Strip Steel

Li Zhengrong

2017, 38(3): 130-134. doi: 10.7513/j.issn.1004-7638.2017.03.023

Abstract(42) PDF(1)

Abstract:
Through measurement of dynamic CCT curve and experiment of controlled rolling and cooling in laboratory for 900 MPa grade hot-rolled strip steel,phase transformation during continuous cooling process and relationship of microstructure,precipitate and mechanical properties at various coiling temperatures were investigated. CCT measurement show that with the increase of cooling rate,the volume fraction of polygonal ferrite decreases and the fraction of bainite increases,when cooling rate exceeds 15 ℃/s,the microstructure fully consists of bainite. With the increase of coiling temperature,the volume fraction of acicular ferrite decreases and that of polygonal ferrite increases; when coiling temperature reaches 600 ℃,microstructure is composed of ferrite and reduced pearlite,and precipitates are finely dispersed,and the resulting hot-rolled strip steel with 1 000 MPa of tensile strength and 17% of elongation can be achieved.

Effect of Titanium on Austenite Dynamic Recrystallization in Low Carbon Mn-Ⅴ Steel

Ke Xiaotao

2017, 38(3): 135-139. doi: 10.7513/j.issn.1004-7638.2017.03.024

Abstract(45) PDF(1)

Abstract:
The austenite grain growth behavior and dynamic recrystallization behavior of low carbon Mn-Ⅴ steel were studied by Gleeble thermal simulation machine,TEM,SEM and quantitative analysis. The results show that the stable titanium carbonitride in steel containing titanium can prevent the effect of austenite grain growth during reheating process. Titanium added steel shows higher deformation resistance than titanium free steel,and its critical deformation for starting dynamical recrystallization is smaller than the latter. Compared with titanium free steel,titanium added steel is readily for recrystallization,and recrystallized grain growth speed is slower and resulted grain size is relatively finer.

Experimental Study on Inclusions Control of Resulfurized Free Cutting Steel

Yu Zhe, Liu Chengjun, Min Yi, Jiang Maofa

2017, 38(3): 140-144. doi: 10.7513/j.issn.1004-7638.2017.03.025

Abstract(40) PDF(1)

Abstract:
In this paper,the effects of calcium treatment and magnesium treatment on characters of inclusions in resulfurized free cutting steels were studied by high temperature experiments. The results show that the main types of inclusions after calcium treatment are Ca-Al-O + （Ca,Mn）S complex inclusions, （Ca,Mn） S and MnS. Meanwhile,the main types of inclusions after magnesium treatment are MgAl₂O₄⁺ （Mg,Mn） S,Al₂O₃+ MnS complex inclusions, （Mg,Mn）S and MnS. The proportions of complex inclusions after calcium treatment and magnesium treatment are 0.67% and 3.57%,respectively. The amounts of type II MnS inclusions in the steel are obviously reduced after Mg treatment,and 91.7% of the inclusions are smaller than 3 μm in size. Furthermore,the ratio of spindle inclusions reached 72.5%. Therefore,the effect of controlling inclusions by magnesium treatment is superior to calcium treatment.

Effect of Vanadium Content on Properties of Semi-solid Gray Cast Iron Containing Vanadium for Drawing Dies

Cai Qun

2017, 38(3): 145-148. doi: 10.7513/j.issn.1004-7638.2017.03.026

Abstract(48) PDF(2)

Abstract:
The wear resistance and thermal fatigue property of semi-solid gray cast iron samples containing vanadium for drawing dies with different contents of vanadium were tested and analyzed. The results show that with increasing vanadium content from 0 to 1.25%,the wear volume of the sample first decreased and then contained unchanged,the average depth of main crack after thermal fatigue test first decreased and then increased,while the average width of main crack first decreased and then contained unchanged. The optimized content of vanadium in the semi-solid gray cast iron was at 1%. Compared with the sample without vanadium,the wear volume of the sample with vanadium content of 1% decreased by 72%,and the average depth and width of main crack after thermal fatigue test decreased by 68% and 79%,respectively.

Analysis of Cracking Reasons in the Cold Heading Process of Q195 Steel

Jiao Shuai, Sun Yanhui, Zhao Yong, Li Xiaobin

2017, 38(3): 149-155. doi: 10.7513/j.issn.1004-7638.2017.03.027

Abstract(103) PDF(5)

Abstract:
The surface quality,crack morphologies,microstructures,oxygen and nitrogen content and non-metallic inclusions of Q195 cold heading steel were studied by a set of analysis techniques,such as acid washing,optical microscopy,scanning electronic microscope （SEM）,and energy dispersive X-ray spectroscopy （EDS）.The results showed that the total oxygen content in steel was 154 × 10^-6,which indicated that non-metallic inclusions content was higher. Large size inclusions were found at the cracks of the rolled material,and a large number of large-sized inclusions were found near 1/4 width to the edge of rolled material,the composition of the inclusions was similar to that of the continuous casting mold powder. Large inclusions cause stress concentration during cold heading,which leads to and aggravates cold heading cracking. At the same time,improper control of rolling process causing the folding defects on the product surface and further 180 ° symmetrical longitudinal cracks,is the main reason for cold heading cracking.

Study on the Mechanism of Improving the Carbides in H13 Steel by Trace Magnesium

Zhou Defu, Chang Lizhong, Zheng Fuzhou, Chen Jiashun

2017, 38(3): 156-162. doi: 10.7513/j.issn.1004-7638.2017.03.028

Abstract(43) PDF(1)

Abstract:
H13 hot working die steel belongs to medium carbon steel,which have high contents of Cr,Mo and V. Therefore,during solidification these carbide forming elements will be separated into a large number of network carbide,which is difficult to be completely eliminated by subsequent heat treatment. Thusthe performance of steel will be reduced. In this paper the effects of different contents of magnesium on the carbides in H13 steel had been studied. Metallurgical observations show that the shape and distribution of carbides in H13 steel can be improved by trace magnesium. The bulky reticulate carbide in steel is interrupted into tiny carbide. And the carbides distributed in H13 steel become fine and uniform after magnesium treatment. 0.004% magnesium additions can achieve the best result. The main reason for the improvement of carbide is magnesium segregation at grain boundaries. Through theoretical analysis,it is found out that the high degree of magnesium segregation at the grain boundaryduring solidification and cooling hinders the growth of carbides and then achieves the purpose of refining carbides.

2017 Vol. 38, No. 3