钢铁钒钛

Experimental Study on the Flotation of Ilmenite in the Onkilonite of Vanadium-titanium Magnetite Using MOH as the Collector

Liu Weijun, Wang Weiqing, Yan Wu, Deng Jie, Zhang Shiqiu, Ren Pengkun

2016, 37(1): 1-6. doi: 10.7513/j.issn.1004-7638.2016.01.001

Abstract(16) PDF(0)

Abstract:
The flotation of ilmenite in the onkilonite of vanadium-titanium magnetite using MOH as the collector was investigated.The effects of dosage of MOH,H₂SO₄ and sodium silicate on separation of ilmenite and gangue minerals were studied.The open and closed circuit experiments for ilmenite flotation were carried out on the basis of condition experiments.The results show that through the closed circuit experiment of "one roughing,one scavenging and four cleanings",the ilmenite concentrate with grade of 46.94% and recovery rate of 53.87% for TiO₂ can be obtained.Production quality inspection shows that the MgO content in the ilmenite concentrate is relatively high and it only meets the requirements for 5th grade of ilmenite concentrate.The SEM results show that there exists a certain amount of olivine in the ilmenite concentrate,which is difficult to be separated and leads to increase in MgO content,eventually affecting the flotation index of the ilmenite concentrate.

Effect of Pre-oxidation on Pulverization of Yunnan Titanium Concentrate during Hydrochloric Acid Leaching

Lin Fan, Yang Jian, Chen Kui, Zhao Dong, Liu Songli, Liu Guoqing

2016, 37(1): 7-11. doi: 10.7513/j.issn.1004-7638.2016.01.002

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Abstract:
Synthetic rutile as a good substitute for natural rutile is greatly used for production of titanium dioxide by chlorination process and sponge titanium.According to the physical and chemical properties of Yunnan titanium concentrate,pre-oxidation and hydrochloric acid leaching method was used to prepare synthetic rutile for researching the effect of pre-oxidation treatment on the leaching rate and pulverization.The results show that the structure of titanium concentrate is changed and the pulverization during hydrochloric acid leaching process is resolved by pre-oxidation.With 20% hydrochloric acid and 5:1 of acid/ore ratio,heating to boiling for leaching the titanium concentrate oxidized at 750℃ for 30 min can obtain synthetic rutile with only 3.29% of particles less than 74μm and 77.1% of grade.

Technology Research on Sodium Salt Roasting of Vanadium Slag Pellet

Yin Zhaoqian, Li Qianwen, Fu Zibi, Wang Jun, Gao Guanjin

2016, 37(1): 12-15,20. doi: 10.7513/j.issn.1004-7638.2016.01.003

Abstract(23) PDF(0)

Abstract:
Roasting of vanadium slag pellets containing sodium carbonate were investigated in this paper.This technology can avoid sintering of raw materials during roasting without addition of residual slag of vanadium extraction,and substantially increases calcination efficiency of vanadium slag coupled with decrease in energy consumption.Moreover,the adverse effect of dust on the environment can be effectively relieved.The optimum process parameters are as follows:about 5 mm of pellets diameter,26% of sodium carbonate to vanadium slag and 800℃ of roasting temperature for 60 min.The immersion ratio of vanadium in clinker is more than 94% under the optimum conditions.By roasting of the vanadium slag pellets under simulating temperature program of industrial multi-hearth furnace,the immersion ratio of vanadium in solution can reach 95% and it is 92% with calculation according to vanadium content in residual slag,both of which are higher than that for traditional process.

Technology Research on Dispersity of Titanium Dioxide

Chen Xinhong, Zheng Shaohua, Li Chun

2016, 37(1): 16-20. doi: 10.7513/j.issn.1004-7638.2016.01.004

Abstract(43) PDF(3)

Abstract:
The "dispersing and grinding"combined process was studied for dispersing TiO₂.The dispersity of TiO₂ particles was characterized as viscosity and particle size.The particle size and morphology of TiO₂ before and after dispersing were observed using TEM.Effects of the dispersing agents and their addition amount,the size of grinding medium and grinding time on the dispersion of TiO₂ were discussed.The results show that the optimum process conditions for dispersing TiO₂ are as follows:sodium metasilicate as the dispersing agent with addition amount of 0.2%(mass ratio) for TiO₂,ZrO₂ as grinding medium with size of 0.4 μm and 25 min of the grinding time.The average particle size of TiO₂ obtained under the optimum conditions is 265 nm with uniform particle size distribution and steady dispersing effect.

Removal of Arsenic from Vanadium-chromium Containing Solution by Ferric Salt

Luo Xiang, Wu Zhenxiu, Fu Zibi, Su Yi

2016, 37(1): 21-25. doi: 10.7513/j.issn.1004-7638.2016.01.005

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Abstract:
According to the higher arsenic content in the leaching solution of roasted vanadium slag produced in steel making with vanadium titanium magnetite from Hongge south mining area,ferric salt was used for arsenic removal to prepare high purity V₂O₅.The effects of initial pH,reaction temperature and time,ratio of Fe and As(w_Fe/w_As),and pH for static settlement on the rates of arsenic removal and vanadium loss were investigated.The results show that the optimum process parameters are as follows:initial pH=3,reaction at 40℃ for 40~50 min with w_Fe/w_As=4~5,then the solution pH is adjusted at 6with NaOH,insulating for 10 min and standing for 12 h.Under the optimum conditions,more than 85% arsenic can be removed with less than 5% of vanadium loss.The content of arsenic in solution is less than 0.08 g/L,and the arsenic content in the obtained V₂O₅(98% purity) is less than 0.01% meeting the standard YB/T 5304-2011.

Study on Sulfuric Acid Leaching of Vanadium-containing Clinker by Calcified Roasting

Wang Chunqiong

2016, 37(1): 26-30,36. doi: 10.7513/j.issn.1004-7638.2016.01.006

Abstract(23) PDF(3)

Abstract:
According to the lower leaching rate of vanadium-containing clinker by calcified roasting in industrial production,effects of the clinker particle size,magnetic materials content and temperature on the leaching rate of vanadium were investigated.The results show that the decrease in leaching rate is mainly caused by coarse clinker particles(ratio of +178 μm particles reaches to 20%),high content of magnetic materials(2%) and low leaching temperature.A leaching rate of vanadium more than 92.46% can be obtained by controlling the ratio of -178 μm clinker particles more than 98%,less than 0.2% of magnetic materials and the final leaching temperature more than 50℃.

Controlling on Front End Bending during Hot Finish Rolling Process of Pure Titanium Coil

Li Jun, Yu Hui, Shi Qingnan, Peng Lin

2016, 37(1): 31-36. doi: 10.7513/j.issn.1004-7638.2016.01.007

Abstract(11) PDF(1)

Abstract:
Front end bending is a common phenomenon in the hot rolling process of plate and strip.Aiming at this problem,in this work,the finite element method was used to study the metal flow of the rolling deformation zone for hot rolling pure titanium coil.The results show that the metal flow of pure titanium assumes the "w"shape,which is different from that of 20-steel with "c"shape,indicating that the control technology of front end bending for plain carbon steels is not completely suitable for pure titanium rolling.We also analyzed the effects of diameter difference between top and bottom work rollers,temperature difference between upper and lower workpiece surfaces,reduction rate,oxide scale thickness and friction coefficient on front end bending,and found that the temperature difference of workpiece surfaces and friction coefficient are the two significant factors that influence the front end bending during hot finish rolling process of pure titanium.From the perspective of temperature controlling,the technological measures that avoid the front end bending of pure titanium coil were made,effectively solving the front end bending problem,which is of practical application value for reducing the loss of cutting head and improving the rolling yield.

Effect of Second Annealing on Properties and Microstructures of Commercial Pure Titanium

Jiang Qingwei, Yang Jie

2016, 37(1): 37-40. doi: 10.7513/j.issn.1004-7638.2016.01.008

Abstract(42) PDF(0)

Abstract:
The microstructures and mechanical properties of cold rolled commercial pure titanium after second annealing was studied.The results show that:the second annealing has no effect on grain size of the factory state pure titanium belt,but it plays an important role in improving the commercial pure titanium plastic processing performance.Moreover,the number of twins increases with the increasing annealing temperature.When the second annealing temperature is lower than 650℃,the yield stress/tensile strength remains unchange.When the second annealing temperature is higher than 650℃,the yield strength decreases obviously; 710℃×60 min annealing can obviously reduce the yield strength and improve its elongation without changing the tensile strength of pure titanium,the sample exhibits excellent processing performance.

Microstructure and Properties of the New-typed TiNi-based Shape Memory Alloy for Micro Electro Mechanical System

Shi Zengfang

2016, 37(1): 41-45. doi: 10.7513/j.issn.1004-7638.2016.01.009

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Abstract:
The new-typed TiNi-based shape memory alloy TiNi45V8In0.2 for micro electro mechanical system was successfully prepared by the method of two-step.The alloy was analyzed by XRD,SEM and so on.And the mechanical properties,stress relaxation resistance and corrosion resistance were tested and analyzed.The results show that the new-typed alloy was composed of the mesh TiNi base phase and dispersive distributed V3Ni phase,which is with better mechanical properties,stress relaxation resistance and corrosion resistance.Compared with common TiNi alloy,the tensile strength of the new-typed alloy at the temperature of -40℃,25℃ and 150℃ could increase by 47.1%,39.4% and 123.9%,respectively.The yield strength of the new-typed alloy at the temperature of -40℃,25℃ and 150℃ could increase by 110.3%、92.5%、263.8%,respectively.Moreover,the corrosion potential of the new-typed alloy could shift positively by 267 mV.The stress relaxation of the new-typed alloy after 50 h could decrease from 16% to 0.5%.

Preparation of Fe-Ti(C,N) Composites from Titanomagnetite Concentrate by Carbothermal Reduction in Air Atmosphere

Wu Enhui, Zhu Rong, Yang Shaoli, Li Hong, Li Jun, Hou Jing

2016, 37(1): 46-50. doi: 10.7513/j.issn.1004-7638.2016.01.010

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Abstract:
Fe-TiC_1-xN_xcomposites were successfully prepared directly from titanomagnetite concentrate by carbothermal reduction in air atmosphere.The influences of reduction temperature and carbon content on the reaction process and phase evolution during carbothermal reduction of titanomagnetite concentrate were mainly investigated using X-ray diffraction(XRD).The results show that,with the reduction temperature increasing,the phase evolution sequences in the reaction process are as follows:Fe₃O₄→Fe and FeTiO₃→FeTi₂O₅→Ti₄O₇→Ti₂O₃→Ti(C,N).The carbon content is the key factor for gas phase equilibrium in the reaction system.When the carbon content is less than 25%,the partial pressure of CO,CO₂ and N₂ could not reach equilibrium or stays at equilibrium for a short time,and the vanadium titanomagnetite concentrate cannot or partially be reduced to Ti(C,N).At reduction temperature of 1 500℃ for 30 min with 30% carbon content,the TiC_1-xN_xhaving about 3 μm of particle size can be obtained with 0.491 5 of C/N ratio and x=0.67,and the obtained particles are obviously agglomerated.

Studying the Electrochemical Deposition of Manganese on the Surface of TiO₂ Nanotube Array by Orthogonal Test

Xiong Zhongping, Si Yujun, Li Minjiao, Feng Juping

2016, 37(1): 51-55. doi: 10.7513/j.issn.1004-7638.2016.01.011

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TiO₂ nanotube array(TNA) was prepared by electrochemically anodizing titanium sheet.Metal manganese was deposited on the surface of TNA by electrochemical reduction to enhance its photoelectrochemical response to visible light.The influences of deposition voltage,time and concentration of Mn(II) ion were investigated by orthogonal test.The results show that the surface modification of manganese on TNA can increase its visible light response,and the photoelectrochemical current is obviously enhanced at a biasing voltage of 0.5 V(vs.SCE).The results from orthogonal test indicate that the deposition time and voltage are the key factors to influence the performance of manganese modified TNA.The optimal conditions for manganese deposition can be summarized as follows:deposition time is 30 s,voltage is -2 V,and the concentration of Mn(II) ion is 10 mmol/L.

Research on Absorption Properties of Ti-doped Short Carbon Fiber/epoxy Resin Composites by Terahertz Time Domain Spectroscopy

Deng Chaoyue, Hu Chengyao, Huo Jichuan

2016, 37(1): 56-60. doi: 10.7513/j.issn.1004-7638.2016.01.012

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Terahertz is the last researched band of the electromagnetic waves,which occupies an important position in the field of stealth and anti-stealth research in the future.TiO₂,Fe-TiO₂ and Ba TiO₃ nanoparticles were prepared by sol-gel method,and then they were doped into short carbon fiber/epoxy resin composites.Research on the absorption properties of Ti-doped short carbon fiber/epoxy resin composites was carried out,and the mathematical model was established by XRD and THz-TDS.The results show that the mixed nanoparticles have optimum absorption properties at 1.12 THz,with 78.1 of absorption index.

Vanadium-titanium Composite Infiltration Process on the Surface of Cold Working Die Steel

Liu Weidong, Lin Cuiqing

2016, 37(1): 61-64. doi: 10.7513/j.issn.1004-7638.2016.01.013

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Vanadium-titanium composite infiltration coating was produced on the surface of Cr12MoV cold working die steel for different time respectively with V₂O₅ and TiO₂ as vanadium and titanium donor,and the microstructure,phase structure,corrosion and wear resistance were tested and analyzed.The results show that vanadium-titanium composite infiltration coating can be successfully produced on the surface of Cr12MoV cold working die steel at 890℃,and the composite infiltration coating is composed of VC、TiC and a spot of V₈C₇.To improve the corrosion resistance and wear resistance of cold working die steel,the composite infiltrating time was optimized at 7 h.

Computer Simulation for Thermo- mechanical Coupling of Friction Stir Welding of Titanium Alloy with High Melting Point

Hu Yu, Kong Jian

2016, 37(1): 65-71. doi: 10.7513/j.issn.1004-7638.2016.01.014

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Based on models for heat transfer and solid mechanics of linear elastic materials with consideration of characteristics that the thermal physical properties of the titanium alloy change with temperature,the thermo-mechanical coupling model for friction stir welding(FSW) of high melting point alloy which is related to process parameters was established.The effect of welding speed on the temperature field,stress and strain of friction stir welding was investigated according to the established FSW model.The results show that with feed direction of stir head as the reference coordinate,the temperature field of FSW is oval-like distributed and large temperature gradient exists in front of the heat source.The transverse distribution of equivalent stress presents a characteristic of symmetry and bimodality,and the equivalent welding stress shows a Miller effect in lateral direction.The welding stress of FSW can be effectively decreased by decreasing the feed speed properly.It is important for understanding the FSW mechanism of high melting point materials by establishing the FSW thermo-mechanical coupling model of titanium alloy with high melting point.

System Design and Preparation of Glass-ceramics Using Titanium Blast Furnace Slag

Li Yaohui, Yang Zhiyuan, Wang Jinzhen, Huang Yourong

2016, 37(1): 72-78. doi: 10.7513/j.issn.1004-7638.2016.01.015

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A new CaO-Al₂O₃-SiO₂ glass-ceramics were prepared using natural cooling titanium blast furnace slag,and the effects of different systems of nucleating agents on the crystallization,microstructure and properties of the glass-ceramics were also studied by DSC,XRD,SEM,etc.The results indicate that highperformance glass-ceramics could be obtained by adding a large amount of titanium blast furnace slag(> 60%),and the moderate concentration of CaO and higher TiO₂ content in this slag serve as effective constitution in terms of promoting the stabilization of glass structure.By introducing Fe/Cr and Ti/Zr nucleating agents,the crystallization of base glass can be promoted and a higher crystallinity can be obtained.The nucleation and crystallization are poor with F/S agents.The major crystalline phases are Diopside and sphene,and the microstructure slightly varies with different nucleating agents.The obtained glass-ceramics have excellent properties with 90 MPa of flexural strength,and chemical durability far superior to that of other common glass-ceramics.

Mechanism of Recovering Iron and Zinc from BF Gas Slime by Self-reduction

Zhu Kuisong, Liu Songli, Gou Shuyun, Zhou Lanhua, Sun Yan

2016, 37(1): 79-84,89. doi: 10.7513/j.issn.1004-7638.2016.01.016

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Abstract:
The heating self-reduction process of blast furnace(BF) gas slime was studied by non-isothermal thermogravimetric(TG) analysis and isothermal heating in Muffle Furnace.The equilibrium compositions and metallization rate of iron and zinc oxides for BF gas slime in reduction process were calculated by HSC thermodynamic calculation software,and the mechanism for reduction of iron and zinc oxides was also discussed.The results show that the heating self-reduction process of BF gas slime may be divided into five stages:I(22.0~390.1℃),physical adsorption of carbon gasification reaction; II(437.7~758.9℃),reduction of iron oxide with increase in metallization rate; III(758.9~936.1℃),co-reduction of iron and zinc oxides with increase in metallization rate of iron and zinc; IV(936.1~1 031.7℃),iron and zinc oxides are reduced sufficiently,with maximum 70% and 99.7% of metallization rate for iron and zinc,respectively; V(1 031.7~1 255.3℃),iron and zinc oxides are reduced completely,and zinc gas may be oxidized.

Effects of Carbon Content on Sintering Performance of Vanadium Titanium Magnetite

Liu Weixing, Li Xiu, Li Jie, Tian Tielei, Long Yue

2016, 37(1): 85-89. doi: 10.7513/j.issn.1004-7638.2016.01.017

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In order to understand the impact of carbon ratio on metallurgical properties and physical effects of vanadium titanium sinterthe strength,yield and particle size composition and metallurgical properties of resulting vanadium titanium sinter at various carbon ratio of 2.5%,2.75%,3.0%,3.25%,3.0%,3.75% had been researched in this paper.It is found out that increasing carbon ratio leads to increase yield of vanadium titanium magnetite sinter,while the proportion of small size sinter decrease,sinter RDI_+3.15 increase,but the sinter drum strength firstly increased then decrease,reducing RI variation.In order to achieve good drum strength and metallurgical properties for vanadium titanium magnetite sinter,suitable carbon ratio is about 3.00%~3.25% and FeO content is about 10%~11%.

Effects of Low Titanium Sintering Parameters on Softening Properties of Burden Load

Li Yanjiang, Lü Qing, Bai Ruiguo, Cao Lihua, Huang Honghu, Liu Xiaojie

2016, 37(1): 90-94. doi: 10.7513/j.issn.1004-7638.2016.01.018

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In order to provide a more comprehensive guide to sinter production and to determine the appropriate parameters of low sintering titanium sinter in Xuanhua Steel,the impact of basicity,carbon content,MgO content,SiO₂ content,moisture on burden load softening properties had been investigated by RUL test device.The results showed that at a given sintering parameters,the effect of carbon content on the softening temperature is not obvious.As the alkalinity increases,the softening temperature of the sinter increases.When R=2.10,the softening temperature of the sinter reached the maximum; When R > 2.10,softening temperature decreased with R.There is an appropriate alkalinity for optimal load softening properties within a certain range of alkalinity.With the increase of MgO content,the softening temperature range is narrowed,breathability enhanced,softening zone moved downward.From this point,increasing the MgO content of the raw material is favor for smooth operation of blast furnace.With increasing SiO₂ content,RUL performance deteriorated,therefore,it can be appropriate to reduce the load softening SiO₂ content to improve the performance of Xuanhua Steel sinter.With the increase of water content,T_10% and T_40% showed an increasing trend,ΔT substantially increased.

Research of Al₂O₃ Influence on Furnace Burden's Dropping Performance of Vanadium-titanium Magnetite

Wang Fujia, Lü Qing, Chen Shujun

2016, 37(1): 95-99. doi: 10.7513/j.issn.1004-7638.2016.01.019

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Experiments were carried out in the lab to simulate dropping zone of blast furnace by a high temperature oven,and the effect of Al₂O₃ on charge softening temperature range,melting temperature range,maximum pressure and other high temperature physical properties had been investigated.The results showed that with the increase of Al₂O₃ charge,both start softening temperature(T₁₀) and the end softening temperature(T₄₀) increased,but softening interval(ΔT₁) was narrowed; charge renewed pressure temperature(T_s) were decreased but dropping temperature(T_d) were increased,while melting range(ΔT_ds) was widened; the maximum pressure(ΔP_max) and the total characteristic droplet value(S) were also increased,which resulted in worse droplet performance.It can be concluded that increase of Al₂O₃ produce negative effect on the performance of the droplet.

Selection of Alloy Design for Low-temperature Toughness Plates Used for Line Pipes

Kathayat T S, Goyal Rajesh K, Shant Raghu, Khadia Sohanlal

2016, 37(1): 100-103. doi: 10.7513/j.issn.1004-7638.2016.01.020

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The low toughness and poor weldability of the higher carbon steel grades restricted their acceptability for line pipe steel,and therefore,created good demand of low carbon micro-alloyed steels for line pipe steel for both onshore and offshore applications.In low carbon micro-alloyed steels,alloy design plays an important role to achieve the desired mechanical properties with minimum processing and alloy cost.During the alloy design process,though primary focus is given to the hot rolling process starting from slab re-heating to final rolling,but steelmaking and continuous casting cannot be overlooked for cleanliness of the steel.This paper presents a detailed study of alloy design and hot rolling parameters to achieve the optimum mechanical properties including higher toughness measured by drop weight tear test at -25℃.These experiments were carried out with API 5L X70M PSL2 grade slabs,which were rolled into plates of size 25 mm x 3 830 mm.The test results were co-related with microstructure analysis and hot rolling parameters.

Influence of Titanium on Strength of Weldable Wire Rod ER50-G Steel

Chen Tao, Li Hong, Tong Qian, Lü Naibing, Wu Keng

2016, 37(1): 104-109. doi: 10.7513/j.issn.1004-7638.2016.01.021

Abstract(7) PDF(1)

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The chemical compositions,mechanical properties,microstructure and precipitates of the weldable wire rod ER50-G produced by Shougang were detected and analyzed statistically in this study.The influence of titanium on the microstructure and precipitates of ER50-G and therefore the tensile strength wire were analyzed.The results showed that a large number of titanium-containing compounds formed and precipitated in ER50-G wire steel.These particles helped to refine the microstructure of ER50-G wire,and also brought significant precipitation strengthening contribution to ER50-G wire.The increment of tensile strength induced by titanium-containing precipitates could be more than 200 MPa.Well control the precipitation behavior,especially decreasing and stablising the precipitation strengthening effects,had been proved to be beneficial of improving the drawing performance of ER50-G wire.

Effect of Ti on Austenite Grain Growth Behavior in Medium Carbon Manganese Steel

He Yingying, Cao Liqiang, Ma Han

2016, 37(1): 110-115. doi: 10.7513/j.issn.1004-7638.2016.01.022

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Effect of Ti on austenite grain growth behavior in medium carbon manganese steel at different heating temperature and time were studied.The results show that Ti-bearing steel exhibited a much sluggish growth rate of austenite grain compared with Ti-free counterpart at higher heating temperature,which was attributed to the pinning effect of Ti(C,N) nanoparticles within size of 100 nm on austenite grain boundaries.The complete solid solution temperature was 1 450℃ calculated by Thermo-calc,and the amounts of nanoparticles Ti(C,N) were still large even at higher temperature.The austenite grain growth model of Ti-bearing steel was successfully established,ie.$D_B=729.25 t^{0.16} \exp \left(-\frac{71 972.3}{R T}\right)$,figuring the larger activation energy for migration of austenite grain boundary and the smaller grain growth index n,which were 72 kJ/mol and 0.16 respectively.The results predicted by the modified equation are found to be good agreement with the experimental results.The developed model could be employed to predict accurately the austenite grain growth of Ti-bearing medium carbon manganese steel.

Analysis of TiN Precipitation Behavior during Solidification of Bearing Steel

Zhao Junpu, Liu Liu, Fan Jianwen, Wang Le

2016, 37(1): 116-121. doi: 10.7513/j.issn.1004-7638.2016.01.023

Abstract(8) PDF(0)

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The inclusions in bearing steel continuous casting bloom were observed,and the large size TiN inclusions were found in the bloom.The effects of Ti and N elements segregation at the solidification front on precipitation of TiN inclusion was studied on the basis of thermodynamics and dynamics.The thermodynamics analysis results show that there is no TiN precipitation above liquidus.When the solid fraction is above 0.65~0.75,the TiN could be precipitated at the solidification front because of Ti and N segregation.With the decrease of Ti and N content in steel,the formation of TiN will be delayed and the size and number of TiN will be decreased.The dynamics analysis results show that with the increase of cooling rate,the size of TiN inclusion during solidification is significantly reduced.When the cooling rate is higher than 50 K/s,the calculated size of TiN is 2.4 μm,and this value will be more than 7.6 μm when the cooling rate is less than 5 K/s.The size of TiN is only tens to hundreds of nanometers in the case of TiN precipitating in solid steel.The TiN inclusion with more than equivalent radius of 2.5 μm was not observed in the surface layer of bloom,but the equivalent radius of 6.77 μm and 8.46 μm were found in the 1/4 thickness and the center of bloom,respectively.These results indicate that the large size TiN inclusions precipitate during solidification.

Thermodynamic Analysis of Components Variation on the Inclusions Precipitation in GCr15 Bearing Steel during Solidification

Tang Guozhang, Ceng Yanan, Li Junguo, Fu Guoqiang, Gao Zhiyuan

2016, 37(1): 122-126. doi: 10.7513/j.issn.1004-7638.2016.01.024

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The evolution of non-metallic inclusions in the GCr15 bearing steel during solidification with different content of[Ca],[Al],[O]and[Mg]was investigated by Fact Sage software which is based on minimum Gibbs free energy principle.The results showed that the inclusion types changed from CaO·2MgO·8Al₂O₃,CaO·2Al₂O₃ to 2CaO·SiO₂,Ca S,meanwhile,the total mass fraction of inclusions increased from 0.004 5% to 0.009 4% with the Ca content increased from 0.000 5% to 0.004 5%.With the Mg content increased from0.000 1% to 0.000 9%,inclusion types changed from CaO·Al₂O₃,2CaO·SiO₂ to MgO·Al₂O₃,Ca S and the total mass fraction of inclusions increased from 0.003 2% to 0.004 1%.With the Al content increasing from 0.005% to 0.05%,the inclusions of 2CaO·SiO₂ changed into CaO·Al₂O₃,CaO·2Al₂O₃,while total mass fraction of inclusions unobviously increased from 0.002 8% to about 0.003 3%.In addition,with the O content increasing from 0.000 3% to 0.002 1%,inclusion types changed from Ca S to CaO·Al₂O₃,CaO·2Al₂O₃,and the total mass fraction increased from 0.002 4% to 0.005 1%.

Optimization Research of Annealing Process for Silicone Modified M2 High Speed Steel

Wang Hongxia, Zhao Hui

2016, 37(1): 127-130,136. doi: 10.7513/j.issn.1004-7638.2016.01.025

Abstract(16) PDF(0)

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Different annealing temperature and annealing time were adopted for annealing treatment of M2-1.0Si silicone modified M2 high speed steel.Through the test and analysis of the microstructure and high temperature mechanical properties,it is found that the annealing temperature and annealing time had important influence on the microstructure and mechanical properties of silicone modified M2 high speed steel.Too high annealing temperature and too long annealing time were not suitable.When at a given annealing time of 8hours,with the increase of annealing temperature from 760℃ to 760℃,the average grain size of M2-1.0Si silicone modified M2 high speed steel firstly remained basically unchanged and then increased dramatically.Both the tensile strength and percentage reduction of area first increased then decreased.When at a given annealing temperature of 850℃,with the extension of annealing time from 4 h to 12 h,the average grain size of silicone modified M2 high speed steel increased sharply after slowly increased,tensile strength and percentage reduction of area decreased sharply after basically remained unchanged.Optimum annealing temperature of M2-1.0Si silicone modified M2 high speed steel is 850℃,the annealing time is 8 h.

Defects Analysis and Control Measures of Continuous Casting Product

Gao Ju, Han Penglong, Gao Chunqun, Ma Yanjie, Ma Lixing

2016, 37(1): 131-136. doi: 10.7513/j.issn.1004-7638.2016.01.026

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Quality defects such as edge crack,roll,strip edge uplift,oxide scale indentation usually occurred in the strip produced in a 1700 hot strip line.In order to eliminate these defects,the main morphology characteristics and causes were analyzed.A series of measures had been taken through adjustment,optimization and transformation for the caster mold taper,work roll gap,laminar cooling side spray and curl side guides machine,phosphorus removal systems and so on.All these efforts effectively reduced the incidence of defects and improved product quality and the product yield.

Influence of F^- on Heat Transfer of Mold Flux and Mineralogical Structure of Flux Film

Zhang Yifei, Han Xiuli, Liu Lei, Liu Lina, Wang Kaiqiang

2016, 37(1): 137-141. doi: 10.7513/j.issn.1004-7638.2016.01.027

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Abstract:
During continuous casting,the mineralogical structure of flux film and heat transfer of mold flux play important roles in strand quality.In this paper,the thermal conductivity and mineralogical structure of flux film with different F^-content were analyzed by the high temperature coefficient of thermal conductivity measuring device and heat flux and viscosity testing device.The results show that with F^-(4.22%~13.22%) increasing,the thermal conductivity of flux film decreases,and the crystallization ratio of corresponding flux film increases.The crystallization ratio of flux films are very high,reaching more than 75%overall.The crystalline minerals of flux films remain same kinds,with dominant cuspidine and wollastonite at different F^- Contents.Meanwhile,with the increase in F^-contents,the cuspidine content continues to increase while wollastonite content decrease significantly.These results have vital guiding significance on improving the strand quality for continuous casting of low fluorine mold flux.

Study on Hot-rolled Steel Wire Rod for Ultra-high Strength PC Steel Wire and Strand

Hu Lei, Wang Lei, Ma Han

2016, 37(1): 142-147. doi: 10.7513/j.issn.1004-7638.2016.01.028

Abstract(27) PDF(0)

Abstract:
In this paper two hot-rolled steel wire rods for ultra-high strength PC steel wire and strand,i.e.,87A and 90A have been studied by the method of gleeble thermal-mechanical simulation,tensile test,metallographic phase and scanning electron microscopy,the microstructure and mechanical properties of the small ingot,wire rod and steel wire.The results show that the tensile strength and drawing performance of the two high carbon steel can meet the requirements of 2 200 and 2 300 MPa PC steel wire and strand.Through comparing the microstructure and mechanical properties of 82B and 87A wire rods produced by the small and industry-scale ingots,it is reasonably expected that the properties of industrial production of 90A steel wire rod was consistent with that of the small ingot.According to the Stelmor cooling practices,the optimization of alloy composition,i.e.,increasing the content of Mn,Cr and V and decreasing Si,was proposed.

Experimental Study on Softening-melting Properties of Xuanhua Steel BF Iron Burden

Zhao Xiaojie, Liu Ran, Li Haojie

2016, 37(1): 148-152. doi: 10.7513/j.issn.1004-7638.2016.01.029

Abstract(18) PDF(1)

Abstract:
In this paper softening-dripping experiment was carried out according to Xuanhua Steel blast furnace structure.Single mine drop test results show that the commonly used two kinds of plant of xuanhua steel sinter have good softening performance but poor drop performance where at 1 520℃ it is still dripping; The soft melting of Xuanhua Steel pellet is the best among three kinds of pellets,but its softening range is longest(313℃).The start softening temperature of PB ore is minimum and its soft melting ranges is longest.In addition,PB ore failed to drip in the test.Menggu ore has good soft melting performance but drop temperature as high as 1 518℃.Through drop tests using 15 kinds of ores,the results show that reducing sinter ratio and increasing the proportion of ore PB can improve the softening-dripping performance.Under the experiment conditions,ore matching scheme is as following "sinter68% + ore pellets16% + PB ore16%",the resulting burden structure can achieve best molten droplet performance.

2016, 37(1): 153-154.

Abstract(14) PDF(0)

Abstract:

2016 Vol. 37, No. 1