钢铁钒钛

Current Situation and Development Prospect of Preparation Technologies for Spherical Titanium and Titanium Alloy Powder

Liao Xianjie, Lai Qi, Zhang Shuli

2017, 38(5): 1-8. doi: 10.7513/j.issn.1004-7638.2017.05.001

Abstract(363) PDF(18)

Abstract:
Preparation technologies of spherical titanium and titanium alloy powder,including traditional gas atomization （GA）,ultrasonic atomization,rotating electrode centrifugal atomization （REP）,plasma rotating electrode process （PREP）,plasma atomization （PA）,RF plasma torch atomization （TEKNA）and newly-invented granulation-sintering-deoxygenation （GSD）,were introduced and compared in this paper.It is proposed that the GSD method will be the mainstream for spherical titanium and titanium alloy powder preparation because of its advantages of low cost and non-strict requirements for equipment,which will finally decrease the cost of rapid prototyping for titanium and titanium alloys and promote the popularization and application of manufacturing technologies for additive materials.

Experimental Study on the Flotation of Gabbro Ilmenite with a Novel Collector

Zheng Yu, Wang Weiqing, Cong Jinyao, Wang Hongbin, Cui Yating

2017, 38(5): 9-14. doi: 10.7513/j.issn.1004-7638.2017.05.002

Abstract(58) PDF(2)

Abstract:
The flotation of a gabbro ilmenite from Panxi area using a novel collector SF was investigated.The effects of collector dosage,p H regulator dosage,depressants types and dosage on separation of ilmenite and gangue minerals were studied.Furthermore,the open and closed circuit experiments for ilmenite flotation were carried out.The results show that the ilmenite can be effectively separated from gangue minerals in the ore obtaining the ilmenite concentrate with grade of 48.06% and recovery rate of 86.36% for TiO₂,through the processes of "one roughing,two scavenging and four cleanings" using SF as the collector.The consumption of the novel collector and cost are lower,which can achieve efficient sorting for gabbro ilmenite.

Vanadium Extraction from Vanadium-chromium Solution by Hydrothermal-hydrolysis Precipitation

Gao Guanjin

2017, 38(5): 15-19. doi: 10.7513/j.issn.1004-7638.2017.05.003

Abstract(34) PDF(2)

Abstract:
Efficient extraction and separation of vanadium from vanadium solution containing high concentration of chromium and sodium was investigated by hydrothermal-hydrolysis method to solve the treatment difficulties of wastewater with high concentration of Na⁺ and NH₄⁺ produced in traditional vanadium precipitation by ammonium salts and provide favorable conditions for the following chromium extraction,according to the characteristics of vanadium-chromium solution obtained by process of sodium roasting-water leaching of high-chromium vanadium slag for vanadium and chromium extraction.The relationship between parameters （hydrolysis temperature,p H and reaction time） and rates of vanadium precipitation and chromium loss was studied.The results show that near 90% of vanadium precipitation rate and vanadium pentoxide （V₂O₅） satisfying YB/T 5304—2011 standard which is produced by calcination of the waterwashed hydrolysis product can be obtained with reaction at 120 ℃ for 180 min in p H = 1.8 system.

Research on Dissolution of Vanadium in Acid Leaching Process of Calcified Roasting Clinker of Vanadium Slag

Ye Lu

2017, 38(5): 20-25. doi: 10.7513/j.issn.1004-7638.2017.05.004

Abstract(64) PDF(4)

Abstract:
Using the calcified roasting clinker of vanadium slag from a certain company as raw materials,sulfuric acid leaching experiments were carried out to investigate the influences of p H,temperature and time,liquid-solid ratio and stirring rate of leaching process on extraction rate of vanadium.The occurrence state of vanadium in the clinker and its dissolution during leaching process were further studied by SEM and XRD.The results show that vanadium in clinker exists as vanadates,mainly distributing in calcium vanadate,iron oxides solid solution,pseudobrookite phases etc.In the process of acid leaching,the dissolution sequence of vanadium-containing phases is as follows:calcium vanadate ＞ solid solution of iron oxides ＞＞pseudobrookite.The optimum leaching parameters are pH = 0.75,50 ℃ for 10 min with 10:1 of liquid-solid ratio and 500 r/min of stirring rate,where up to 90.21% of vanadium leaching rate can be achieved.

Study on Reducing Soluble Vanadium Content in the Residue after Sulfuric Acid Leaching of Vanadium Slag Roasted with Calcium Oxide

Wang Chunqiong, Yang Bing, Liu Xuezhi, Xiong Kaiwei, Yan Yong, Sun Yuzhong

2017, 38(5): 26-30. doi: 10.7513/j.issn.1004-7638.2017.05.005

Abstract(43) PDF(1)

Abstract:
Effects of liquid-solid ratio and time of leaching,residence time of slurry,washing times,elution water volume and filtration rate on the soluble vanadium （SV） content of the residue after acid-leaching of vanadium slag roasted with calcium oxide in the industrial production of vanadium oxides were investigated.It is indicated that the soluble vanadium content in the residual is higher with liquid-solid ratio of leaching lower than 3.6,leaching time more than 240 min,slurry residence time more than 90 min,washing times less than once,elution water volume below 19 m³ and filtration rate exceeding 0. 42 m³/min.A more superior leaching and filtration efficiency can be obtained and the soluble vanadium content in the residual is decreased,with liquid-solid ratio of leaching higher than 3.8,60~150 min of leaching time,3 times of washing,20~22 m³ of elution water volume and 0.25 m³/min of filtration rate.

Semi-quantitative Analysis of Phase Conversion of Vanadium Slag in Sodium Calcination Process

Wang Minghua, Zhao Hui, Liu Yan, Kong Chuiyu, Liu Zhenhui, Lou Taiping, Sun Zhaohui, Jing Han, Tang Hongjian, Yu Bin

2017, 38(5): 31-36. doi: 10.7513/j.issn.1004-7638.2017.05.006

Abstract(53) PDF(2)

Abstract:
Using sodium carbonate as additive,experimental studies of oxidation roasting of vanadium slag were conducted.The content of sodium vanadate was detected through XRD semi quantitative method and the factors influencing the formation of sodium vanadate were investigated.The phase transitions and their corresponding temperatures of vanadium slag during the roasting process with sodium carbonate（Na₂CO₃） presence were studied by some assistant methods （e.g.SEM and TG）.Experimental results show that the oxidation roasting process mainly consists of the decomposition of olivine and spinel phases,as well as the formation of vanadates,chromates,silicates,sodium titanate,sodium aluminate and sodium ferrite.The mass fraction of sodium vanadate in products increases with the increase of V₂O₅ and Na₂CO₃ content with 730 ℃ of the optimal reaction temperature and 80 min of optimal reaction time when the content of sodium vanadate （Na₄V₂O₇） in vanadium phases is up to 98.09% and other vanadium phases are mainly CrVO₃ and CrVO₄ and FeVO₄.

Study on Carbon Content Control for FeV80 Alloy

Yu Bin, Sun Zhaohui, Pan Cheng, Chen Haijun, Tang Hongjian

2017, 38(5): 37-41. doi: 10.7513/j.issn.1004.7638.2017.05.007

Abstract(98) PDF(1)

Abstract:
The occurrence states and decarburization thermodynamic conditions of carbon in FeV80 alloy were analyzed,and the effects of carbon content of lime,C/V ratio,conduction time and content of decarbonizer on vanadium content in slag and carbon content in alloy were tested.Theoretical analysis results show that the main occurrence states of carbon in the alloy are VC and Fe₃C under atmospheric pressure,and the complete oxidation of carbon and reduction of vanadium can be implemented only when the system P_CO is lower than 3.2 Pa and 127.7 Pa of the equilibrium CO partial pressure of V-C-O and V-Fe-C-O system,respectively.Increasing the free oxygen activity of metal-slag interface as the dynamic hot area of carbon-oxygen reaction is beneficial for the oxidation removal of carbon in the alloy.The experimental results show that reducing the carbon content of lime and C/V ratio are conductive to decrease the carbon in alloy.The conduction time does not obviously influence the reduction of the carbon content in alloy,but decreasing the conduction time tends to prevent the subsidence of molten alloy.FeO has a certain effect on reducing the carbon content in alloy,but it is also easy to cause reoxidation of vanadium.The average carbon content of the alloy can be reduced to 0.10%,and the average vanadium content in the slag is about 1.32% at the optimum conditions.

Preparation of AlV55 Alloy by Aluminothermic Reduction

Yin Danfeng, Sun Zhaohui, Chen Haijun, Wang Yonggang, Du Guangchao

2017, 38(5): 42-45. doi: 10.7513/j.issn.1004.7638.2017.05.008

Abstract(116) PDF(4)

Abstract:
The thermodynamics for preparation of AlV55 by aluminothermic process was analyzed by Fact Sage software and differential thermal analyzer.The results show that the reaction occurs spontaneously with 3 276.61 K of adiabatic combustion temperature and 4 567.06 J·g^-1 of unit thermal effect,attributed to a liquid-liquid reaction.The effect of V content on yield rate of products and influence of unit thermal effect on vanadium yield rate were also studied.It is indicated that for AlV55 alloy the elevated V content can reduce the effect of Al8V5 brittle phase and increase the yield rate of products in air atmosphere.The unit thermal effect has a significant effect on vanadium yield rate,with about 96.5% of the maximum vanadium yield rate at 3 367 J·g^-1 of the unit thermal effect.

Theoretical and Experimental Research on Preparation of Ti-Al Alloy by Electric Aluminothermic Reduction

Li Jun, Lu Xionggang, Yang Shaoli, Wu Enhui, Hou Jing, Li Chonghe, Lai Qi, Ma Lan

2017, 38(5): 46-52. doi: 10.7513/j.issn.1004-7638.2017.05.009

Abstract(59) PDF(2)

Abstract:
Ti-Al alloy was prepared using electric aluminothermic reduction method with titanium white as raw materials.The influence of temperature and aluminum addition on the alloy-slag separation,phase of slag,microstructure,composition and phase of alloy were researched.Through theoretical analysis it shows that the elevated roasting temperature can lower the viscosity of slag in favor of the alloy-slag separation.A better separation of alloy and slag can be obtained at 1 550 ℃ according to the experiments.Addition amount of aluminium has significant influence on the compositions of alloy and slag.The melting point and viscosity of slag increase with presence of massive low-valence titanium oxides in the slag caused by insufficient aluminium addition,and the slag-alloy separation is favorable with Al/TiO₂＞0.7.Increasing the aluminum addition can enhance the yield rate of alloy and titanium.Meanwhile,the aluminium content in Ti-Al alloy increases and the alloy phases convert.The main phases of alloy are TiAl and Ti₃Al as Al/TiO₂= 0.7 while TiAl and TiAl₃ as Al/TiO₂= 0.9.SEM,XRD and EDS analysis show that the slag included in alloy exists as CaAl₄O₇.

Preparation of Nano-titanium Dioxide/Graphene Composites and the Enhanced Photocatalytic Performance

Luo Jinhua

2017, 38(5): 53-59. doi: 10.7513/j.issn.1004-7638.2017.05.010

Abstract(51) PDF(2)

Abstract:
Nano-titanium dioxide/graphene composites were prepared by a facile hydrothermal method for the enhanced photocatalytic applications.The samples were characterized and analyzed by means of XRD,UV-Vis SEM and EDS.With methylene blue （MB） as the target degradation material,the photocatalytic effect of nano-TiO₂/graphene composites was evaluated.It was shown that the composite material was well crystallized,the band gap was small,and had a good photocatalytic performance under visible light.The results showed that hydrothermal time,hydrothermal temperature,and content of graphene oxide had influence on the photocatalytic properties of the composite. The photocatalytic activity of the sample increased with the increase of hydrothermal time and content of graphene oxide,and increased first and then decreased with the increase of water temperature.The nano-TiO₂/graphene composites showed the best photocatalytic activity with the hydrothermal time of 10 h,temperature of 120 ℃ and graphene content of 5%,and the degradation rate of composite powder for methylene blue was up to 86.99% within 5 h.

Effect of Preparation Method on the Electrochemical Performances of Vanadium-titanium Hydrogen Storage Alloy

Wang Yanli

2017, 38(5): 60-63. doi: 10.7513/j.issn.1004-7638.2017.05.011

Abstract(51) PDF(2)

Abstract:
For improving the electrochemical performances of vanadium-titanium hydrogen storage alloy,vanadium-titanium hydrogen storage alloys were prepared by various casting processes,and the electrochemical corrosion resistance and electrochemical cycling stability were tested and analyzed. The results show that compared with the optimized process of conventional casting,ultrasonic casting process can make the corrosion potential of the sample positively shift by 0. 125 V and the discharge capacity decay rate decrease by 29 %,respectively.Both the electrochemical corrosion resistance and electrochemical cycling stability of the alloy were greatly improved. The vanadium-titanium hydrogen storage alloy was optimized by ultrasonic casting process.

Microstructure of （TiB+TiC）/TC18 Titanium Matrix Composite Undergoing Heat Treatment

Tang Menghan, Lu Jie, Chu Shiyi, Sun Shuyu

2017, 38(5): 64-67,72. doi: 10.7513/j.issn.1004.7638.2017.05.012

Abstract(85) PDF(4)

Abstract:
Three kinds of Ti-5Al-5Mo-5V-1Fe-1Cr titanium matrix composites reinforced with trace amount of TiB and TiC were fabricated via a consumable vacuum arc-remelting furnace in this work.The reinforcements were produced during solidification by the chemical reactions between B₄C and Ti.The mass fractions of B₄C were 0.1%,0.2% and 0.4%,respectively. The as-cast ingots were subjected to thermomechanical processing and heat treatment.The β phase in the composites was significantly refined.However,with increase of the B₄C content,the refining extent of β grains was not linearly related but increased more and more slowly.It was suggested that this should be related to the accelerating effects of the reinforcements on the merging of β grains.

Effect of Coating Preparation Process on Properties of Vanadium-titanium Modified Cold Working Die Steel

Wang Xiaofeng, Zhao Ruishan

2017, 38(5): 68-72. doi: 10.7513/j.issn.1004-7638.2017.05.013

Abstract(31) PDF(1)

Abstract:
The vanadium-titanium modified cold working die steels were surface treated by various coating preparation processes.The wear resistance at room temperature of 25 ℃ and high temperature of 300 ℃,and impact property at room temperature of 25 ℃ were tested and analyzed. The results show that when the composite process of flame spraying followed by laser cladding was used,the wear volume of the die steel at room temperature decreased by 23% and 27%,its wear volume at high temperature decreased by 46% and 50%,and the impact absorption energy increased by 29% and 18%,compared with those of the steels separately by coating preparation process of flame spraying and laser cladding,respectively.

Analysis of Factors Affecting the Production of PAHs in Coking Process

Gao Jianxin, Shi Yan, Zhao Xin, Song Jinying

2017, 38(5): 73-77. doi: 10.7513/j.issn.1004-7638.2017.05.014

Abstract(40) PDF(1)

Abstract:
In this study simulation preparation of coke had been performed in a laboratory oven with single coal,and coal blending as raw material,respectively,and then collect and detect PAHs produced during the coking process,in order to investigate the effects of coking temperature,coking process and coal adhesion,ash and moisture on the emission of polycyclic aromatic hydrocarbons （PAHs） during coking.The results show that Coking temperature of 700~920 ℃ can generate the highest PAHs emissions.It is found out that coking characteristics,coal tar and pyrolysis products and other factors have great impact on the initial production of polycyclic aromatic hydrocarbons i,and low-emission PAHs produce more emissions.The PAHs emissions increase with the increase of coal adhesion and ash content,while they decrease firstly and then increase with the increase in water content.

Research on the Molding of Sulfur Cobalt Concentrate Pellets Containing Carbon

Li Junhan

2017, 38(5): 78-83. doi: 10.7513/j.issn.1004-7638.2017.05.015

Abstract(40) PDF(1)

Abstract:
Using Panzhihua sulfur cobalt concentrate as raw materials and polyvinyl alcohol as binding agent,the influences of moisture content,molding pressure,particle size of sulfur cobalt concentrate and content of binding agent on the compression strength and drop strength of the sulfur cobalt concentrate pellets containing carbon were studied by single factor experiments. The results show that the strength of the pellets fluctuates slightly and then increases rapidly with increase of the moisture content,and it increases firstly and then decreases with increase of the binding agent content.Besides,with increase of the pressure and refinement of the grains,the trend of strength of the pellets presents N-type. The optimized technology parameters obtained are 5:1 for mass ratio of mineral to coal,12% of moisture content,6 MPa of the molding pressure,0.6% of binding agent content and 75% of sulfur cobalt concentrate with particle size lower than 74 μm.Under these conditions mentioned above,the compression strength and drop times are separately 192.6 N/pellet and 28.4 times/pellet for the wet pellets,348.2 N/pellet and 57.2 times/pellet for the dried pellets,respectively.

Properties of BOF dust and its effect on combustion of pulverized coal

Wu Hao, Zou Chong, Zhao Junxue, Li Xiaoming

2017, 38(5): 84-89. doi: 10.7513/j.issn.1004-7638.2017.05.016

Abstract(88) PDF(2)

Abstract:
The physical and chemical properties of four kinds of BOF dust and their effects on the combustion performance of pulverized coal were studied by using a variety of detection methods. The results show that there are Fe₃O₄,Fe₂O₃,CaO and CaCO₃ in the phase composition,and the microstructures of the samples are obviously different.The pores with size below 10 nm contribute to the main surface area,while the pores above 10 nm contribute to the main pore volume.The pulverized coal combustion reactivity has been improved by reducing the ignition,burnout and corresponding temperature of reaction peak due to dust addition,,nervetheless too high carbonate content will inhibit its enhanced combustion effect.

Optimal Matching of Thermodynamics Behavior of Iron Tailings during BF molten slag conditioning Process

Xing Hongwei, Liu Zhenchao, Liang Wei, Zhang Yuzhu, Ren Chengran, Zhang Huiqi

2017, 38(5): 90-95,100. doi: 10.7513/j.issn.1004-7638.2017.05.017

Abstract(57) PDF(2)

Abstract:
In order to study and optimize the matching relationship between different iron tailings and blast furnace slag during conditioning process,the effect of iron tailings in different proportions on the thermodynamic system of blast furnace slag had been predicated by using the software Fact Sage 7.0 based on the heat balance principle and mathematical model,and the melting temperature of the blast furnace slag with iron tailings as conditioning agent had been calculated through three spline interpolation algorithm.Meanwhile,the temperature drop of blast furnace slag system in different acidity at different temperature had been determined.The optimal matching between different ratio of modifying agent of iron tailings and thermal compensation had been simulated and predicated by using genetic optimization of grey neural network algorithm.

Determination of Titanium Content in Ferrosilicon Nitride by Diantipyrylmethane Spectrophotometry

Li Jie, Yu Lujun, Zhang Suizhong

2017, 38(5): 96-100. doi: 10.7513/j.issn.1004-7638.2017.05.018

Abstract(37) PDF(1)

Abstract:
A method for determination of titanium content in ferrosilicon nitride by diantipyrylmethane（DAPM） spectrophotometry was investigated.Some condition experiments were done,which includes decomposition of samples,smoking of sulfuric acid,coloring,interference and eliminating method,and the optimal conditions were obtained.The sample was fused and decomposed with 3 g sodium hydroxide in an iron crucible at 650 ℃.The sintered mass was dissolved with 50 mL hot water,and then the solution was acidified with 10 mL hydrochloric acid and 5 mL hydrofluoric acid. The silicon and residual hydrofluoric acid in the solution was removed by total 7 mL sulfuric acid for two times of smoking.The Fe （Ⅲ） ion was reduced by ascorbic acid to eliminate the interference of iron in the solution.After the reaction with diantipyrylmethane in 2 mol/L hydrochloric acid medium at room temperature,the solution was measured at absorption wavelength of 390 nm by photometer.A detection limit of 0.02% for this method was also obtained by experiments.At last,this method was applied to the determination of some ferrosilicon nitride standard samples,good accuracy and precision were evidenced with 0.05%~2.00% of titanium content.

Research on Smelting-separation for Metallized Pellets of Vanadium-titanium Magnetite

Hong Lukuo, Qi Yuanhong, Sun Caijiao, Li Mingduo, Gao Jianjun, Wu Bingqiang

2017, 38(5): 101-107. doi: 10.7513/j.issn.1004-7638.2017.05.019

Abstract(83) PDF(5)

Abstract:
The smelting-separation process for metallized pellets of vanadium-titanium magnetite was studied in the lab.The ternary phase diagram of slag was calculated under various basicity by using Factsage software and the influences of smelting temperature,smelting time and the basicity of the metallized pellet on the results of slag-iron separation,iron recovery ratio and the quality of biggest nugget were investigated.The results demonstrate that increasing smelting temperature at an appropriate extent can improve the iron recovery ratio and is beneficial for slag-iron separation.With the increase of the basicity of the metallized pellet,the iron recovery ratio increases firstly and then descends.The iron recovery ratio increases with the rise of smelting time,but the iron recovery ratio slightly reduces after 40 min.The optimal conditions are 1 550 ℃,R = 1. 0,40 min. Under this conditions,the iron recovery ratio reaches 93. 17% and the quality of biggest nugget reaches 24.16 g with very good slag-iron separation.

Research on Compressive Strength Changes and Mechanism of Magnesium Flux Pellets

Wang Liguang, Cai Shuang, Tian Tielei

2017, 38(5): 108-111. doi: 10.7513/j.issn.1004-7638.2017.05.020

Abstract(73) PDF(1)

Abstract:
The effect of basicity on the compressive strength of the magnesium flux pellets was studied,and based on the pore structure and microscopic morphology,the reasons for the changing the compressive strength were analyzes. The relationship between the porosity and compressive strength were established.The results show that with the increase of basicity,compressive strength of magnesian flux pellets increases firstly and then decreases.Compressive strength achieves the maximum level of 2 598 N when the basicity is 1.0.The main reason causing the compressive strength change is that with the increase of basicity,the pore diameter gradually become larger and homogeneous,and the content of liquid gradually increases.Larger pore diameter and high fraction of liquid phase result in the decrease of compressive strength.Meanwhilethe relationship between porosity and compressive strength of magnesian flux pellets was illuminated based on theory of mciro cracks.

Feasibility Analysis of Simultaneous Dephosphorization and Vanadium Extraction by Converter

Chen Lian

2017, 38(5): 112-117. doi: 10.7513/j.issn.1004.7638.2017.05.021

Abstract(41) PDF(3)

Abstract:
The thermodynamic calculations of element-oxidation in the process of vanadium extraction in converter had been done.The calculated results indicatethat the slag containing calcium can keep P₂O₅ in the slag.The molecular-ion model was established for high calcium vanadium slag system,and the calculations for setted slag shows that effect of the slag on phosphorus-fixation is greatest when P₂O₅ content in the slag is 2% and basicity is 1.9; under the condition of logP_O₂=（-5）,phosphorus is fixed by CaO in the form of 3 CaO.P₂O₅,and the effect was the best.It is proved theoretically that it is feasible for simultaneous dephosphorization and extraction of vanadium in vanadium extraction converter.

Location Method for Relevant Production Process Parameters of Continuous Casting Slab Quality

Cong Junqiang, Xu Xuehua, Peng Shiheng, Mi Jinzhou, Zhang Xingzhong

2017, 38(5): 118-122. doi: 10.7513/j.issn.1004-7638.2017.05.022

Abstract(138) PDF(4)

Abstract:
Real time collection and precise location for production process parameters of continuous casting slab is the basis for the online determination of continuous casting slab quality and the online optimization of production process parameters.On the basis of the actual production experience,a new location method for production process parameters of continuous casting slab has been developed. The method,which based on the casting length modification,can locate the real time production process parameters to section of continuous casting slab and thus overcomes shortages of the traditional location method. In addition,the accurate locate production process parameters can be saved into information group identified by section of continuous casting slab.Based on this,model of continuous casting slab quality determination by LM-BP algorithm has been established and used to analyze information groups of section of continuous casting slab.The experiments demonstrated that the data collect method is of high accuracy and the model is of high accuracy.

Study on Dephosphorization Technology In Converter with High Scrap Ratio

Zhou Chaogang, Wang Shuhuan, Wang Wenhui, Ai Liqun, Zhao Dingguo, Xue Yuekai, Hao Huaqiang

2017, 38(5): 123-128. doi: 10.7513/j.issn.1004-7638.2017.05.023

Abstract(41) PDF(1)

Abstract:
In order to solve the problem of too high phosphorus content in end liquid steel of converter with high scrap ratio,the effects of the conditions of hot metal charging and end point on dephosphorization were studied by combing with the theory of dephosphorization thermodynamics.The results show that the optimum conditions for dephosphorization in hot metal charging and end point are as follows:when hot metal temperature and hot metal Si content should be controlled 1 300~1 360 ℃ and 0.55%~0. 65% respectively in hot metal charging;basicity,Fe O and Mn O were reached ≥2.6、16%~22% and 2.5%~4.0% respectively in converter end point,phosphorus content of liquid steel at the end point can be successfully achieved less than 0.015 0%.

Effects of Pre-strain and Baking Process on the Microstructure and Bake-hardening Behavior of 780 MPa Cold Rolled Dual-phase Steel

Wang Minli

2017, 38(5): 129-135. doi: 10.7513/j.issn.1004-7638.2017.05.024

Abstract(61) PDF(1)

Abstract:
In a typical process,C-Mn steel was annealed at 800 ℃ for 60 s,and then cooled rapidly to 300℃ to carry out the over-aging treatment.The ferrite-martensite microstructure was obtained after the simulated continuous annealing process. After pre-straining and baking,the specimens were used to measure the BH₂ values.The influences of pre-strain,baking temperature and baking time on the microstructure evolution and bake-hardening behavior of the 780 MPa cold rolled dual-phase steel were investigated.It was found out that the BH value apparently increased with an increase of pre-strain in the range from 0% to 2%; however,increasing pre-strain from 2% to 8% led to a decrease in the BH₂ value.And the maximum of BH₂ value at the pre-straining of 2% is 51 MPa. Furthermore,the BH₂ value enhanced due to increaseing amount of Cottrell atmosphere in the ferrite grain interior and carbide in both of ferrite and martensite phases with increasing the baking temperature.The BH₂ value reached a maximum of 102 MPa at the baking temperature of 300 ℃.Moreover,with an increase in the baking time from 5 to 240 min,the BH₂ value enhanced gradually due to the Cottrell atmosphere formation and carbide precipitation in the ferrite.

Study on Influence Factors of Intragranular Ferrite Nucleation in Non Quenched and Tempered Medium Carbon Steel

Wu Zhe, Zhang Caijun, Liu Yi, Zhang Yanchao

2017, 38(5): 136-141. doi: 10.7513/j.issn.1004-7638.2017.05.025

Abstract(45) PDF(1)

Abstract:
The acting factors of influencing intragranular ferrite nucleation in non quenched and tempered medium carbon steel were investigated.By means of metallographic microscope and scanning electron microscope,the nucleation and growth of intragranular ferrite were investigated from three aspects of the size,distribution and type of inclusions.It provides a basis for smelting high quality clean steel.Experimental results show that when the composition of inclusions are Al₂O₃,TiN,VN etc.the best size of induced equiaxed ferrite is 2~4 μm; distribution of equiaxed ferrite coated inclusion is most conducive to the growth of ferrite;MnS precipitation on the surface of TiN is very benefit to induce intragranular ferrite.

Effect of Hot Rolled Deformation on the Microstructure and Mechanical Property of Low Si-Mn-Nb As-hot Dual-Phase Steel

Li Qiuhe, Ying Chuangtao, Li Jiangwei, Ren Junwei

2017, 38(5): 142-146. doi: 10.7513/j.issn.1004-7638.2017.05.026

Abstract(42) PDF(1)

Abstract:
The effect of different deformation on the microstructure and mechanical property of Si-Mn-Nb ashot dual-phase steel were investigated by using TEM,SEM technology and optical microscopy. The results showed that the structure morphology where the island of martensite are dispersed in small ferrite matrix enables hot rolled dual phase steel to obtains comprehensive mechanical properties.With the increase of the deformation,the volume of the second phase increases,but some second-phase particles is serious segregation.The yield strength and tensile strength of hot rolled dual phase steel firstly increase and then drop,yield ratio increased and plasticity decrease.It is found out that the deformation of 92.1% can result in excellent combined mechanical performance with tensile strength achieving an average of 795.66 MPa.

Effect of Bath Temperature on Ni-Sn-Mn Alloy Coating Prepared by Pulse Electrodeposition

Meng Qingbo, Qi Haidong, Lu Shuai, Guo Zhao, Yang Haili

2017, 38(5): 147-151. doi: 10.7513/j.issn.1004-7638.2017.05.027

Abstract(43) PDF(1)

Abstract:
In order to improve the corrosion resistance of mild steel in marine environment,Ni-Sn-Mn alloy coatings were prepared on the surface of Q235 steel by pulse electrodeposition.The effect of bath temperature on coating element content,surface morphology,deposition rate,cathode current efficiency and corrosion resistance was investigated by glow discharge spectroscopy （GDS）,scanning electron microscopy （SEM）,Tafel curve and electrochemical impedance spectroscopy （EIS）.The results showed that with the increasing bath temperature,the content of Ni and Sn decreased at first and then increased,while the content of Mn raised firstly and then dropped; coating deposition rate and cathode current efficiency increased; corrosion resistance of coatings strengthened firstly and then weakened. The coating prepared at the bath temperature of 30 ℃ was uniform and compact,and had the biggest corrosion potential（-0.374 V）,the smallest corrosion current density（4.266×10^-8 A·cm^-2）,the biggest charge transfer resistance（7 459 Ω·cm²） and exhibited the best corrosion resistance in 3.5% NaCl solution.

Research on Spot Welding Process of Hot Galvanizing DP780

Zhou Leilei, Yu Tengyi

2017, 38(5): 152-156. doi: 10.7513/j.issn.1004-7638.2017.05.028

Abstract(39) PDF(1)

Abstract:
In this paper,the spot weldability of hot galvanizing DP780 had been investigated and the spot welding parameters had been optimized.The spot welding performance of hot galvanizing DP780 had been evaluated by measuring the nugget diameter,penetration rate and indentation depth,observing the microstructure,texting the hardness,detecting the shear force and tensile force of welded joints. The result showed that,the spot welding performance of hot galvanizing DP780 was good because of the high alloy content,while the welding process window was narrow.When the electrode pressure was 3.5 kN,and the welding current was 9.5 kA,the welding time could be selected from 300 to 400 ms.When the welding current was 10.5~11. 5 kA,the welding time could be select from 200 to 400 ms. The microstructure of hot galvanizing DP780 weld joint was composed of martensite and ferrite,resulting in a low plasticity ratio of only 10% ~30% and somewhat high hardness.The failure form of welded spot was melt nugget stripping.

Microstructure and Properties of Q420 30^# Large Channel Steel Used for Transmission Towers

Zeng Shangwu, Li Fenghui, Zhang Lei, Xu Delu, Chen Chunsheng, Su Lei

2017, 38(5): 157-162. doi: 10.7513/j.issn.1004-7638.2017.05.029

Abstract(46) PDF(3)

Abstract:
A Q420 grade 30^# large gauge channel steel was developed via vanadium micro-alloying. The microstructure and properties of tested steel were systematically investigated by using optical microscope,tensile test and impact test. The results show that the microstructure of test steel is mainly composed of banded ferrite and pearlite. The microstructures difference at different positions result in difference in properties.Under the low temperature condition,tested steel has stable mechanical properties,and with excellent impact toughness,which meets the E-level regulated by national standards.

2017, 38(5): 163-164.

Abstract(37) PDF(1)

Abstract:

2017 Vol. 38, No. 5