钢铁钒钛

Effects of Properties and Structure of Metatitanic Acid on Rutile White Pigment via Short Sulfate Process

Tian Congxue

2019, 40(1): 1-6. doi: 10.7513/j.issn.1004-7638.2019.01.001

Abstract(86) PDF(5)

Abstract:
The properties and structure of metatitanic acid, such as crystal structure, particle size distribution and impurity iron's content, have great effects on the structure and pigment properties of rutile titanium dioxide, and there exists inherent relationship between them. The rutile TiO₂ white pigment was produced via short sulfate process by using unenriched low concentration industrial titanyl sulfate solution as titanium source. In order to produce rutile TiO₂ with good structure and excellent pigment properties, the optimal conditions are as following. Controlling the grain size of metatitanic acid less than 8.9 nm and about 7.9 nm can effectively promote the crystal transformation and grain growth of the rutile pigment, and obtain rutile pigment with good and integrated crystal structure. The appropriate particle size distribution of metatitanic acid has an obvious effect on rutile titanium dioxide with narrow particle size distribution, and rutile pigment of near 0.20 μm in the particle size can obtain higher relative scattering force. The hydrolysis conditions should be controlled to reduce the specific surface area of metatitanic acid, aiming at reduction of the iron impurity adsorption.

Study on the Optically Variable Property of Nano-TiO₂

Wu Jianchun, Lu Ruifang

2019, 40(1): 7-12. doi: 10.7513/j.issn.1004-7638.2019.01.002

Abstract(74) PDF(2)

Abstract:
The morphology and particle size of nano-TiO₂ were analyzed by transmission electron microscopy(TEM),and the optically variable property of the automobile paint made of the nano-TiO₂ was also analyzed by a five-angle colorimeter.The results show that the paint film containing single nano-TiO₂ has no angle-dependent optical effect,showing white phase on the white substrate while blue phase on the black substrate.The automobile paint composed of nano-TiO₂ and aluminum powder has an optically variable property.The particle size of TiO₂ has a great influence on the optically variable property of the paint,where the aluminum paint modified by ordinary titanium white with an average particle size of 280 nm has no angle-dependent optical effect but it shows significant angle-dependent optical effect for the aluminum paint modified the nano-TiO₂ with an average particle size of 35 nm.Furthermore,the color variation from different angles for the paint increases with increase of the nano-TiO₂ addition.The angle-dependent optical effect is originated from Rayleigh scattering occurring on the surface of nano-TiO₂ under illumination,exhibiting a golden yellow phase in the parallel direction with the incident light,blue phase perpendicular to the incident light and blue phase with different degrees in other directions dependent on the angles.

Preparation of TiO₂ by Sol-gel Method and Its Photocatalytic Properties

Zhang Nana, Wang Hongxia, He Youqing, Li Xinxing

2019, 40(1): 13-17. doi: 10.7513/j.issn.1004-7638.2019.01.003

Abstract(61) PDF(1)

Abstract:
As an environment-friendly catalyst,titanium dioxide(TiO₂) plays an important role in photocatalysis.In this paper,TiO₂ powder was prepared by sol-gel method without stirring,using butyl titanate(TBT) as the titanium source.The crystal structure,morphology and absorbance of the samples were analyzed by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM) and ultraviolet-visible spectroscopy(UV-Vis),respectively.The results show that the phase of the samples changes from anatase to rutile with increase in calcination temperature,combined with the morphology variation.The sample roasted at 400℃ shows peanut-like morphology,and the irregular shapes appear at 500℃.The rutile phase begins to appear at 600℃.At the calcination temperature of 700℃,all the phases transfer into rutile with irregular morphology.Using methyl orange as the simulated wastewater,the degradation ability of the samples was investigated under ultraviolet irradiation.The best photocatalytic property can be obtained with the sample calcinated at 400℃,leading to 91% of degradation rate for methyl orange at 80 min of illumination.

Temperature Rise Characteristics and Absorption Behaviors of Titanium Slag during Microwave Heating

Pu Jing, Zhang Zhiyun, Liu Qianqian, Duan Liping, Ruan Rongsheng, Chen Guo

2019, 40(1): 18-22. doi: 10.7513/j.issn.1004-7638.2019.01.004

Abstract(66) PDF(2)

Abstract:
Microwave heating of titanium slag to prepare artificial rutile has the outstanding advantages of uniform high efficiency and low energy consumption.Under different conditions,titanium slag exhibits different temperature rise characteristics in the microwave field.Using titanium slag as the research object,the effects of microwave output power,particle size of the titanium slag and material quantity on the microwave absorption performance of the slag were systematically investigated.The results show that increasing the microwave output power is beneficial to increase the heating rate of titanium slag in the microwave field,while the increase of material quantity will cause a decrease in the rate of temperature rise of titanium slag,and the reduction of particle size is also adverse to the temperature rise of titanium slag in the microwave field.

Research on Solvent Extraction for Separation of Vanadium and Chromium

Ying Ziwen, Ren Xiulian, Wei Qifeng

2019, 40(1): 23-28. doi: 10.7513/j.issn.1004-7638.2019.01.005

Abstract(46) PDF(2)

Abstract:
Using the O216 synthesized in laboratory and 3^# inert solvent as the extraction solution and the leaching solution from sodium roasting of V-Cr slag as raw material,the effects of pH of the leaching solution,concentration of the extraction solution,extraction temperature,extraction time and phase ratio on the separation efficiency of V and Cr were studied.The saturation capacity of the extraction solution under the optimum conditions was determined.The optimum conditions are shown as follows:the leaching solution pH of 1.8,the volume concentration of 40% for the extraction solution,the extraction temperature of 30℃,the extraction time of 5 min,and the phase ratio of 1:1.The single stage extraction rate of vanadium and chromium are 98.79% and 36.42% respectively,with the separation factor at 142.90.The saturation capacity of O216 extraction solution for vanadium and chromium is respectively 41.46 g/L of V₂O₅ and 3.62 g/L of Cr₂O₃.It shows an effective separation of vanadium and chromium in the extraction solution of O216-3^# inert solvent.

Refining Process of Vanadium Removal for TiCl₄ with High Content of Vanadium by Fatty Acid

Li Liang, Zhou Li, Hu Yuanjin, Ling Peng, Chen Jiayu

2019, 40(1): 29-32. doi: 10.7513/j.issn.1004-7638.2019.01.006

Abstract(83) PDF(12)

Abstract:
Based on the mechanism studies of vanadium removal from TiCl₄ by fatty acid,the industrial experiments for vanadium removal by the selected fatty acid were carried out according to the independently developed refining process for vanadium removal of TiCl₄.The results show that the independently developed process for vanadium removal can meet the industrial requirements of high vanadium content TiCl₄,with the refined TiCl₄ satisfying the requirements.

Synthesis and Electrochemical Properties of Aluminum Doped Lithium Vanadium Phosphate

Cao Zhiqin, Du Xiaofeng, Zhou Xiaofei, Liu Zhiyue, Du Linyan, Wu Chuanyang, Zhang Xuefeng

2019, 40(1): 33-40. doi: 10.7513/j.issn.1004-7638.2019.01.007

Abstract(104) PDF(3)

Abstract:
To improve the low conductivity of lithium vanadium phosphate,aluminum doped Li₃V₂(PO₄)₃/C powder was prepared by solution combustion synthesis using lithium nitrate,ammonium metavanadate and ammonium dihydrogen phosphate as raw materials,glycine as complexing agent and fuel,glucose as carbon source and aluminum nitrate as aluminum source,respectively.The electrochemical performances of the as-prepared aluminum doped Li₃V₂(PO₄)₃/C powder as cathode material for lithium ion battery were characterized by constant current charge-discharge,cyclic voltammetry(CV) and AC impedance(EIS).The results show that aluminum doping can effectively improve the conductivity of lithium vanadium phosphate.Different aluminum-doped proportions of lithium vanadium phosphate have different electron conductivities and diffusion rates of lithium ion.When the doping content of aluminum is 1%,the lithium vanadium phosphate has the optimum electrochemical performances with the discharge capacity of 104.6 mAh/g at the rate of 10 C after 500 cycles.

Effect of Conductive Agents on Electrochemical Performances of Li₃V₂(PO₄)₃/C Cathode Material for Lithium Ion Batteries

Li Nali, Pu Chunlei, Tong Yanwei, Cui Xumei, Zhang Xuefeng

2019, 40(1): 41-46. doi: 10.7513/j.issn.1004-7638.2019.01.008

Abstract(123) PDF(6)

Abstract:
In this paper,the effects of conductive agents on the electrochemical properties of lithium vanadium phosphate were investigated.The influences of graphene,acetylene black and Super P Li on the electrochemical properties of lithium vanadium phosphate were studied using Li₃V₂(PO₄)₃ as the cathode material.The results of galvanostatic charge/discharge and electrochemical impedance tests show that different conductive agents have a significant effect on the electrochemical properties of the electrodes.The lithium vanadium phosphate cathode material using Super P Li as the conductive agent exhibits the highest discharge specific capacity and the most excellent rate performance,with a small AC impedance value.On basis of the above results,the effect of the content of Super P Li on the electrochemical performances of lithium vanadium phosphate was further investigated.The results show that the battery using 10% Super P Li as conductive agent has a smaller internal resistance and a higher discharge specific capacity,a superior cycle performance and rate performance.

Ni-Fe/TiO₂ Composite Electrode by Electrodeposition and Its Catalytic Performance for Hydrogen Evolution

Qi Haidong, Zhou Zongyi, Wen Linjie, Zhang Linan, Li Yungang, Yang Haili

2019, 40(1): 47-52. doi: 10.7513/j.issn.1004-7638.2019.01.009

Abstract(48) PDF(1)

Abstract:
Ni-Fe/TiO₂ composite electrodes were prepared by electrodeposition.Cathodic polarization curve and electrochemical impedance spectroscopy were used to study the hydrogen catalytic property of electrodes.The results show that the hydrogen evolution property of Ni-Fe/TiO₂ composite electrode is better than Ni-Fe alloy electrode.TiO₂ particles can increase specific surface area of electrode,Ti can form Ti-H_ads hydrogen bond with H,which is favorable for formation and adsorption,a composite desorption effect of H_ads exists between TiO₂ particles and Ni-Fe alloy,enhancing hydrogen catalytic performance of electrode.With the addition of TiO₂ particles in the bath,the catalytic performance for hydrogen evolution of electrode first increases and then weakens.

Hydrogen Storage and Electrochemical Properties of Cast Vanadium Based Alloys for Automotive Batteries

Wang Youfang, Zhao Yue

2019, 40(1): 53-56. doi: 10.7513/j.issn.1004-7638.2019.01.010

Abstract(83) PDF(2)

Abstract:
Casting tests for V₃TiNi_0.56 and V₃TiNi_0.56Y_0.1Co_0.1 alloys used in automobile batteries were carried out,and the hydrogen storage performance,electrochemical property and microstructure of the alloys were tested and analyzed.The results show that compared with V₃TiNi_0.56 alloy,the maximum hydrogen absorption capacity of V₃TiNi_0.56Y_0.1Co_0.1 alloy increases from 3.13% to 3.88%,and the retention rate of discharge capacity of V₃TiNi_0.56Y_0.1Co_0.1 alloy increases from 23% to 91% after 20 times of charge-discharge cycles.The dendritic arm of V₃TiNi_0.56Y_0.1Co_0.1 alloy is refined,and the interval for dendritic crystals of V₃TiNi_0.56Y_0.1Co_0.1 alloy is decreased,with the hydrogen storage and electrochemical properties of the alloy improved significantly.The addition of Y and Co as alloying elements can improve the hydrogen storage and electrochemical cycling stability of V₃TiNi_0.56 alloy applied to automobile batteries.

Influence of Organosilicon on Pigment Characteristics and Application Properties of Titanium Dioxide

Liu Chan

2019, 40(1): 57-61. doi: 10.7513/j.issn.1004-7638.2019.01.011

Abstract(89) PDF(8)

Abstract:
In this study,the organosilicon containing different functional groups was used for surface modification of titanium pigment coated with zirconia and alumina,to investigate the effects of organosilicon on the thermal stability of titanium dioxide by analyzing the whiteness variation of titanium pigment after preservation at the high temperature.Meanwhile,the influences of organosilicon on the pigment and application performances of titanium dioxide were also studied.The results show that the organosilicon with different functional groups corresponds to various pigmental properties such as thermal stability and oil absorption,and multifarious application performances like dispersion and covering power of the pigment.Nevertheless,the different types of organosilicon illustrate little influence on the whiteness and brightness of titanium pigment.

Effect of Mo in V-microalloyed Precipitating-strengthen High Strength Steel

Zhu Chenglin, Gao Cairu, Zhu Changyou, Du Linxiu, Yang Xiongfei, Qu Bingbing

2019, 40(1): 62-68. doi: 10.7513/j.issn.1004-7638.2019.01.012

Abstract(46) PDF(1)

Abstract:
The effects of Mo element on the precipitation of low temperature bainite zone in V microalloyed steels were investigated for the V microalloyed steels,by means of isothermal precipitation simulations,TEM,calculation of Thermo-calc software.And the effect of Mo element on the mechanical properties of V microalloyed steel was investigated by hot rolling experiment and mechanical properties test in laboratory.The results show that the addition of Mo can significantly improve the precipitation potential.When the Mo content increases from 0% to 0.6%,the volume fraction of precipitates can be increased from 0.019% to 0.025% for the sample held at 600℃ for 40 min.The addition of Mo element can significantly improve the strength of the V microalloyed steel.The yield strength and tensile strength of the steel with 0.6% Mo element are 667 MPa and 803 MPa,respectively, which are 113 MPa and 119 MPa more than these of the steel without Mo addition.

New Technology of Vanadium Extraction from Vanadium-bearing Steel Slag

Xie Yu, Ye Guohua, Zuo Qi, Hu Yibo, Tong Xiong

2019, 40(1): 69-77. doi: 10.7513/j.issn.1004-7638.2019.01.013

Abstract(164) PDF(9)

Abstract:
Vanadium-bearing steel slag,generated from the steelmaking process of vanadium-titanium magnetite,can be used as the raw material for preparation of V₂O₅.However,it is still very difficult to utilize the slag at present due to the high content of calcium oxide,iron and the low content of vanadium.In view of the problems of the existing vanadium extraction technologies and the characteristics of vanadium-bearing steel slag,a new technology for extracting vanadium from V-bearing steel slag through combined process of beneficiation and metallurgy has been developed,and emphatic study on the pretreatment by beneficiation,selective stage leaching,purification and enrichment was carried out.Finally,better results were achieved.Compared with total vanadium recovery of less than 70% when extracting vanadium from V-bearing solid waste by traditional processes,the index of vanadium extraction for the new technology is greatly improved with total vanadium recovery of 80%.And the new technology would have broad development potential due to the cancellation of the roasting process,which not only increases the leaching index,but also saves a lot of equipment investment and decreases the pollutants discharge.Moreover,raw material used in the new technology is vanadium-bearing steel slag rather than vanadium slag.Thus the new technology is one of the waste utilization technologies,having great significance in the full utilization of vanadium resources.

Research on Removing Sodium from Extracted Vanadium Residue

Zeng Guanwu, Hao Jianzhang

2019, 40(1): 78-82,104. doi: 10.7513/j.issn.1004-7638.2019.01.014

Abstract(32) PDF(4)

Abstract:
The extracted vanadium tailings contain useful iron and vanadium,while they bring risk when it is used for iron-making process due to their high sodium content.To solve the problem,three methods such as leaching,reduction-magnetic separation and sodic reduction-leaching-magnetic separation to remove sodium had been studied.It is found out that pressure leaching with CaO can remove 80.5% of sodium from the tailing.When the tail is reduced at 800℃,iron is reduced into magnetite and hardly to be separated because of its tiny size.While the temperature is increased to 1 200℃,the magnetite is further reduced into metallic iron and then aggregate,leading excellent separation effect.Reducing the extracted vanadium tailing with sodium salt and coal powder can obtain simultaneous transformation of iron and vanadium.Then after leaching and magnetic separating processes,iron,sodium and vanadium are separated efficiently.Besides,sodium salt can be partly replaced by calcium salt.

Experimental Study on Flotation of Coarse-grained Ilmenite by New Collector

Yang Daoguang, Han Kexi, Ye Endong, Song Bing

2019, 40(1): 83-87. doi: 10.7513/j.issn.1004-7638.2019.01.015

Abstract(51) PDF(1)

Abstract:
A new collector TM with fatty acid as the main component was synthesized from petrochemical tailings by esterification.The flotation performance of TM was studied by flotation of coarse-grained ilmenite.The results show that both TM and MOH reagents can obtain qualified titanium concentrate with the grade of TiO₂>47% and S < 0.1%.The amount of TM collector is 1 000 g/t higher than that of MOH,but TM does not need diesel as the auxiliary collector.The cost per ton of titanium concentrate with TM collector is 13.91 yuan lower than that using MOH collector.

Process Optimization of Strong Magnetic Separation of Coarse Grain on Midi Titanium Plant

Li Jinlin, Wang Hongbin, Wang Jianping, Zhang Chun, Wu Xuehong

2019, 40(1): 88-93. doi: 10.7513/j.issn.1004-7638.2019.01.016

Abstract(60) PDF(1)

Abstract:
In order to solve the problem of high flotation cost and small particles size of TiO₂, the optimization study of strong magnetic separation technology was carried out for one stage of high magnetic separation concentrate with a grade of 16.94% of TiO₂. The test results showed that:0.125 mm sieve was used for classification, and then, the process of "spiral and electric separation" was adopted on oversize product;and mixing floatation was adopted after strong magnetic separation on spiral middings, electricmiddings and coarse slag, finally, a electroselective titanium concentrate with TiO₂ grade 47.67% and recovery 34.25% and a flotation concentrate with TiO₂ grade 47.18% and recovery 34.83% were obtained, that is, the mixed titanium concentrate with TiO₂ grade of 47.42% and recovery of 69.08%. The process optimization not only reduces the amount of grinding, but also optimizes the final product's particle size, and providing theoretical support for industrial production.

Isothermal Reduction Kinetics of Carbon Coated Iron Ore Powder

Hao Suju, Sun Tianhao, Jiang Wufeng, Lan Jiran, Zhang Yuzhu

2019, 40(1): 94-98. doi: 10.7513/j.issn.1004-7638.2019.01.017

Abstract(32) PDF(1)

Abstract:
In this paper the influence factors achieving optimum carbon coated magnetite isothermal reduction rate had been studied.Bituminous coal and anthracite were used as carbon source,and carbon-coated ore powder with a grinding time of 105 s had been used for test in a modified dynamic reduction reactor.Weight loss state of iron ore powder coated with carbon source at different temperatures for both bituminous and anthracite were measured.The rate equations under three restrictive factors are combined with the multiphase reaction rate equation.The fitting curve and the rate constant k of the equation are obtained by linear fitting.Then the maximum likelihood method is used to obtain the D3 model as the best model.That is,the gas phase is a restrictive link,and the developed model equation is G(α)=[1-(1-α)^1/3]².Based on the developed model he calculated activation energy E_a is 52.317 kJ/mol.

Application Research on Blowing Nitrogen Alloying of SA-182 F92

Zhang Feng

2019, 40(1): 99-104. doi: 10.7513/j.issn.1004-7638.2019.01.018

Abstract(50) PDF(1)

Abstract:
Based on the theoretical analysis of thermodynamics and kinetics of adding nitrogen by blowing nitrogen,application study of F92 blowing nitrogen alloying technology had been carried out by using titanium slag furnace as a byproduct of liquid semisteel smelting,and then blowing nitrogen alloying process control conditions for LF refining,VD treatment,and supplementary blowing nitrogen had been proposed.The purification effect was significant after nitrogen adding by blowing nitrogen during LF refining process,VD continued blowing nitrogen and decompression nitrogen release treatment.The nitrogen content in the F92 steel can be stabilized in the target composition of 380×10^-6~450×10^-6,with high cleanliness and no defect in bloom,which fully meets the requirements of ASME SA-182/SA-182 M-2010.

Influence of Adsorption Rod Material on Removal of Inclusions in the Nozzle

Zhao Dingguo, Zhang Fujun, Wang Yufei, Wang Shuhuan

2019, 40(1): 105-111. doi: 10.7513/j.issn.1004-7638.2019.01.019

Abstract(39) PDF(1)

Abstract:
Through thermal experiments,the adsorption of impurities in molten steel under the condition of aluminum deoxidation was studied on the three kinds of adsorption rods,ie,magnesium-zirconium,magnesium-chromium and magnesium-calcium.The experimental results show that from the aspects of the number of inclusions,area ratio and adsorption rate per unit area,the adsorption capacity of magnesium calcium adsorption rods on inclusions in liquid steel is stronger than that of magnesium zirconium and magnesium chromium adsorption rods.The number of inclusions per unit area at the middle and edge of the sample reduced by 29.66% and 39.26% compared with the original deoxidized steel ingot,and the area ratio reduced by 56.83% and 64.33%.The inclusion absorption velocity was 0.34 μm/s.

Study on the Effects of EMS Stirring Intensity on Carbon Homogeneity of 360 mm×450 mm Gear Steel Bloom and Control

Li Hongguang

2019, 40(1): 112-117. doi: 10.7513/j.issn.1004-7638.2019.01.020

Abstract(39) PDF(4)

Abstract:
Application research on 20 CrMnTiH(FQ) gear steel bloom by combined-EMS technology for homogeneity controlling was carried out on a 360 mm×450 mm continuous casting machine..The specific install position of EMS had been determined based on the result of numerical simulation calculate,and 10.0~11.0 m far away from mold liquid steel surface is the suitable position.The EMS process parameters have been researched and the effects of processes on homogeneous control have been compared.Process parameters that suitable for 20 CrMnTiH(FQ) gear steel bloom homogeneity control have been found out based on the actual magnetic intensity,that's M-EMS:(280±5)×10^-4 T,F-EMS:(300±5)×10^-4 T.Effective control for homogeneity of bloom have been realized,the average of standard mean square deviation for the degree of segregate is 0.052,and range is below 0.027.

Thermodynamic Calculation of Ti-containing Second Phase in Ti Microalloyed High Strength Steel

Li Liming, Feng Yunli, Yang Lina

2019, 40(1): 118-122. doi: 10.7513/j.issn.1004-7638.2019.01.021

Abstract(43) PDF(3)

Abstract:
Using thermodynamic Thermo-Calc software the calculation and analysis of high-Ti microalloyed high strength steel with different Ti content and different N content were carried out to study the effect of Ti and N elements on solid solution precipitation of Ti-containing second phase in high-Ti microalloyed high strength steel.The results show that under certain conditions,decreasing N content and increasing Ti content can improve Ti yield and obtain more beneficial phase TiC and reduce the volume fraction of harmful phase TiN.

Study on Hot Ductility of Slab of 1 180 MPa Grade F/M High Strength Dual Phase Steel for Automobile

Li Shouhua, Cao Xiao'en, Zhao Linlin, Su Zhenjun, Hu Yukun

2019, 40(1): 123-128. doi: 10.7513/j.issn.1004-7638.2019.01.022

Abstract(48) PDF(3)

Abstract:
The hot ductility of 1180 MPa F/M high strength dual phase steel for automobile had been investigated in the temperature range of 650℃ to 1300℃ using a Gleeble 3500 thermal simulator. The thermoplastic curve was drawn,and the fracture and microstructure of high temperature tensile specimen were observed. The test results show there is a brittle zone in the test temperature and the brittle temperature zone is in range of 675℃ to 910℃. The minimum shrinkage rate reaches 28.76% at 800℃,and it shows good plasticity in the temperature range of melting point to 910℃ with shrinkage rate above 60%. the high temperature plastic zone is narrow and the Ⅲ brittle zone is a typical "U" curve and wide range,indicating high crack sensitivity. Fracture observationI shows that the fractures at both 650℃ and 950℃ have typical dimple which belong to ductile fractures. Fracture at 800℃ is typical brittle mixing along grain boundary and cleavage fracture. The fracture at 650℃ is mainly caused by precipitation of pro-eutectoid ferrite along original austenite grain boundary. The brittle fracture at 800℃ is mainly caused by grain boundary weakening.The high-temperature strength above 1050℃ is low,because the tensile stress exceeds the maximum strength of the steel. In order to avoid slab cracking during straightening section,the slab straightening temperature should be controlled above 950℃ which fall out of the Ⅲ brittle zone(from 675℃ to 910℃).

Effect of N on Mirostructures and Mechanical Properties of Vanadium Containing Q345 Steel

Yang Jichun, Tian Shiyu, Yu Haicun, Zhang Zening, Wang Jun, Yan Ruijun

2019, 40(1): 129-135. doi: 10.7513/j.issn.1004-7638.2019.01.023

Abstract(40) PDF(2)

Abstract:
The test steels in this study had base chemistry of Q345 steel with 0.08%V and various nitrogen contents of 0%, 0.022%,0.034% and 0.042%.Thermo-Calc software was used for the thermodynamic calculation.When steel is free of nitrogen,the calculated V(C,N) precipitation temperature in austeniteis 933℃.When the nitrogen content in the steel is 420×10^-6.the precipitation temperature of V(C,N) is 1 340℃.TEM observation indicates that increasing nitrogen content can result in a large number of V(C,N) which plays the role of precipitation strengthening and refining grain.The mechanical properties of the steel increase significantly with increasing nitrogen content.The steel free of nitrogen has yield strength of 486 MPa,and tensile strength of 686 MPa.When the nitrogen content is 340×10^-6,the yield strength of the test steel is 610 MPa,and the tensile strength is 732 MPa.Fracture observation show that toughness and ductility of Q345 steel has been enhanced with increase of nitrogen content.

Effect of Nb and V on Microstructure and Mechanical Properties in Hot-stamping Steel

Chen Jundong, Hao Ying, Tao Weichun, Li Yongliang

2019, 40(1): 136-141. doi: 10.7513/j.issn.1004-7638.2019.01.024

Abstract(50) PDF(2)

Abstract:
The influence of micro alloy niobium(Nb) and vanadium(V) on microstructure and mechanical properties in hot-forming steel was investigated by optical microscope(OM),scanning electron microscope(SEM) and transmission electron microscope(TEM).The results show that the volume fraction of martensite or bainite in continuous annealing strip increased with the microalloying addition,which would promote the recrystallization nucleation ratio during the reaustenitizing process.therefore,the microstructure would be refined effectively duringthe subsequent heat treatment process.The sizes of martensitic packets and lath lamellar spacing reduce simultaneously with micro-alloying addition for the tested steel.Though both Nb and V addition improve the mechanical properties,the Nb-bearing steel shows poor tempering stability compared with the V-bearing steel.

Effect of P Elements on Mechanical Properties and Corrosion Resistance of High Strength Weathering Steel Used in Transmission Tower

Luo Yihua, Huang Yao, Yang Xuefeng, Chen Guohong, Teng Yue, Liu Weining, Li Feng

2019, 40(1): 142-147. doi: 10.7513/j.issn.1004-7638.2019.01.025

Abstract(305) PDF(4)

Abstract:
The effects of P content(0.20%~0.39%) on the microstructure,mechanical properties and corrosion resistance of the steel were analyzed by means of scanning electron microscopy(SEM),universal testing machine,impact testing machine,wet-dry composite testing machine and diffractometer.The results show that P content in this study has little effect on the microstructure and mechanical properties of steel.,however,increase of P content will increase the D-type spherical oxide.The increase of P content will reduce the low temperature performance of steel,especially when the temperature is below -40℃.When the content of P in steel is 0.028%,the weathering steel of transmission tower has the best corrosion resistance.The rust layer thickness of indoor accelerated corrosion sample approximates 10 μm.

Microstructure and Performance Analysis of Nb Microalloy Steel

Dou Weixue, Guo Dong, Feng Jie, Guo Zhihong, Zhu Miaoyong, Wang Xiaoli

2019, 40(1): 148-152. doi: 10.7513/j.issn.1004-7638.2019.01.026

Abstract(203) PDF(12)

Abstract:
With the development of high speed and heavy load transportation in modern railway,higher demanding requirements have been put forward for performance of high speed rail steel.At present,domestic hot-rolled 980 MPa (U75V) rail cannot meet the requirements. Nb microalloying steel was produced in laboratory in order to develop ultra-high hardness and strength steel for speed rail.When Nb content is 0.028%,mechanical properties of high speed rail test steel reach the maximum value,ie,its tensile strength is 1 229 MPa,yield strength is 716 MPa,hardness is HB343 and elongation rate is 11%. And the microstructure performance of Nb test steel reaches the best state.Space between pearlite lamellar is 0.26 μm,and its grain size grade is ASTM No.8 to 8.5.

Microstructure and Thermal Properties of Laser Cladding Ni-Cr-Mo Alloy Steel Coating

Ding Jie, Lü You, Zhang Ziyang, Duan Mingwei, Wang Shuqi, Cui Xianghong

2019, 40(1): 153-159. doi: 10.7513/j.issn.1004-7638.2019.01.027

Abstract(184) PDF(7)

Abstract:
in this paper,two kinds of Ni-Mo-Cr coatings were laser-clad on the surface of H13 steel substrate by Nd³⁺:YAG laser.The chemical compositions of applied coatings were Ni₉Mo₂Cr_2.5Al_0.15Ti₁B₄Si₃Fe_78.4 and Ni₂Mo₂Cr_2.5Al_0.1Ti₁B₄Si₃Fe_85.4(mass fraction,w/%)respectively. Surface morphology,microstructure,phase composition,composition and thermal stability of the coating had been investigated by X-ray diffraction(XRD),metallographic microscope,scanning electron microscope(SEM),energy dispersive spectroscopy(EDS) and microhardness tester.The results show that the coatings of two Ni-Mo-Cr powders are metallurgically bonded to the matrix.The surface morphology presents uniform and dense fish scale.The main phases of the coating are γ-(Fe,Ni) solid solution,FeCr,α-Fe and NiCrFe equivalent compounds.Tthe coating region is composed of equiaxed grain,and the bonding region is composed of relatively coarse,columnar dendrites perpendicular to the bonding surface.The average microhardness of Ni-Mo-Cr coatings with 9% and 2% Ni addition are 650 HV_0.2 and 740 HV_0.2,respectively,which is about 2.8 to 3.2 times that of the matrix(230 HV_0.2). The thermal stability of the Ni-Mo-Cr coating is greatly improved compared to the H13 steel,and the coating is better when the Ni addition is 2%.

Analysis and Control of Influencing Factors of Longitudinal Crack on SPHC of Low-carbon-low-silicon-aluminium Killed Steel

Li Zhonghua, Zhou Chaogang, Yang Xiaojiang, Ai Liqun, Wang Shuhuan, Hou Mingshan

2019, 40(1): 160-165. doi: 10.7513/j.issn.1004-7638.2019.01.028

Abstract(47) PDF(1)

Abstract:
For the problem of occurrence rate high of central longitudinal crack on tangsteel hot rolled plate,In order to effectively achieve the purpose of reducing occurrence rate of central longitudinal crack.This paper as relying on the 1 700 mm production line of Tangsteel hot rolling department,The influencing factors of central longitudinal crack for hot rolled plate low-carbon-low-sillicon-aluminium killed steel as SPHC were studyed and analysised by industrial test,numerical simulation and site investigation.The results showed that:There are many factors that affect center crack of SPHC slab,which are mainly reflected in the factors such as immersion depth,Mn/S,casting speed,mold taper,mold type,covering slag type and submersed nozzle type and other factors.After through the above measures to optimize the adjustment,The average incidence rate of central cracks eventually can be achieved that from the original 5.38% to the current less than 0.96%,in order to improve the effective protection for successfully produce high-quality steel products on the 1700 continuous casting production line.

High-temperature Mechanical Properties of 12Mn Steel Round Billet

Wang Xu, Wei Jun, Qiu Shengtao, Li Zhaoling, Li Wei, Liu Xuesen, Zhang Yong

2019, 40(1): 166-170. doi: 10.7513/j.issn.1004-7638.2019.01.029

Abstract(51) PDF(1)

Abstract:
The high-temperature mechanical properties of 12 Mn steel round billet were tested by using a Gleeble-1500 D thermal/force simulation tester.Tensile strength,the reduction of area(ψ) and stress-strain curve in the range of 600~1 300℃ were obtained.The results show that of 12 Mn steel round billet has high strength.The tensile strength at 650℃ is 275 MPa,and it decreases with increasing temperature.The third brittleness temperature zone of the round billet is wide with temperature range at 600~750℃,and the reduction of area(ψ) in the temperature range is less than 60%.The stress of the 12 Mn round billet at different temperatures increases firstly with the strain and then decreases,and finally tends to be stable.Finally,the precipitation phase of the III brittle zone was verified by Thermal-cal software.

2019, 40(1): 171-172.

Abstract(43) PDF(1)

Abstract:

2019 Vol. 40, No. 1