钢铁钒钛

Research on Beneficiation Process of Gansu Low-grade Ilmenite

Chen Kaida, Fu Jiangang, Wang Hui

2013, 34(1): 1-6. doi: 10.7513/j.issn.1004-7638.2013.01.001

Abstract(41) PDF(1)

Abstract:
A kind of low-grade ilmenite from Gansu province with Fe grade of 12.23% and TiO₂ grade of 3.80% was studied.In view of the occurrence state and percentage of Fe and Ti in the ore and acute shortage of water in the mining area,a combined technical solution of "pre-concentration for tailing discarding by dry medium-intensity magnetic separation-iron separation by fine grinding and low-intensity magnetic separation-titanium separation by combination of high-intensity magnetic separation with flotation" was designed.The effects of relevant factors(ground particle size and magnetic induction intensity,etc.) on test results were investigated.Based on the optimal technical condition,a full process of closed-circuit test was carried out.The obtained iron concentrate had a Fe grade of 60.57% and titanium concentrate had a TiO₂ grade of 46.15%,and the recovery rates of Fe and Ti reached 35.14% and 66.19% respectively,realizing efficient and comprehensive recovery of iron and titanium resources in the ore.

Analysis on Causes of and Countermeasures for Blockage of Chlorine Feeding Pipe in the Process of Molten Salt Chlorination

Lu Hui, Yang Renmu, Meng Jun, Xie Gang, Yang Wen

2013, 34(1): 7-12. doi: 10.7513/j.issn.1004-7638.2013.01.002

Abstract(22) PDF(1)

Abstract:
The causes of the blockage of chlorine pipe in the process of molten salt chlorination for TiCl₄ production are analyzed in this paper.It has been found that the main factors leading to blockage of chlorine pipe are temperature,raw materials,pressure,molten salt and operation.Some measures can be taken to reduce or avoid the occurrence of blockage,including appropriate control of temperature,pressure,molten salt and operating parameters,reasonable choice of raw materials and optimization of design scheme.

Recovery of Vanadium from Vanadium-bearing Molten Iron in Ladles in a Pilot Plant

Qin Jie

2013, 34(1): 13-17. doi: 10.7513/j.issn.1004-7638.2013.01.003

Abstract(36) PDF(2)

Abstract:
Recovery of vanadium from molten iron in ladles was carried out in a Pangang pilot plant for comprehensive utilization of vanadium and titanium resources,and influencing factors vanadium recovering process,including temperature,oxygen supply,slag skimming and Si content in the molten iron,were analyzed.The results show that in practical production,good results can be achieved with temperatures of molten bath at 1 450~1 500℃,smooth bottom blowing,oxygen supply at 1 400 m³/h and timely addition of adequate coolant.So far,vanadium slag with V₂O₅ content above 7% has been obtained.

Effect of Temperature on Compressive Deformation and Damage Behavior of Commercially Pure Titanium(CP-Ti)

Jiang Qingwei, Jiang Yehua, Zhang Jun, Wang Jixian

2013, 34(1): 18-21. doi: 10.7513/j.issn.1004-7638.2013.01.004

Abstract(33) PDF(1)

Abstract:
The deformation and damage behavior of CP-Ti under unidirectional compression at temperatures ranging from-196℃ to 600℃ was studied by universal materials tester and scanning electron microscopy(SEM) etc.It has been found that the compressive deformation and damage behavior of this material is sensitive to temperature.With the increase of temperature,the yield strength,peak stress and flow stress of the samples gradually decreases.Surface deformation and damage characteristics exhibit corresponding changes.Below 200℃,CP-Ti shows an anomaly that its plastic deformability decreases with rise of temperature.

High-temperature Deformation Behavior of New Near-β Titanium Alloy Ti-7333

Cheng Liang, Chang Hui, Fan Jiangkun, Tang Bin, Kou Hongchao, Li Jinshan

2013, 34(1): 22-25,40. doi: 10.7513/j.issn.1004-7638.2013.01.005

Abstract(36) PDF(1)

Abstract:
Compression tests were conducted under constant temperature to investigate the flow behavior of the new near-β titanium alloy Ti-7333.The results reveal that flow stress of the tested alloy is very sensitive to processing parameters.With the increase of temperatures and decrease of strain rates,the flow stress of Ti-7333 significantly decreases.The flow behavior of the alloy is dominated by dynamic recovery,acompanied by dynamic recrystallization.In addition,based on the evolution model of dislocation density put forward by Mecking and Bergstrom,a constitutive model was constructed to predicate the flow stress of Ti-7333.Due to its relatively limited parameter numbers,this model could be conveniently applied to accurately describe the flow stress during thermal deformation of the alloy.

Cause Analysis of Strip Cracks on Surface of TA17 Alloy Cold-rolled Sheet

Huang Deming, Yang Xiongfei, Wei Qingfeng, Chen Yong, Guo Hua, Jiang Rengui

2013, 34(1): 26-30. doi: 10.7513/j.issn.1004-7638.2013.01.006

Abstract(24) PDF(1)

Abstract:
Strip cracks along rolling direction on the surface of TA17 alloy cold-rolled sheet were observed by stereoscope,SEM and EDS.Morphology observation indicated that cracks were dominantly in zigzag shape,with 10~30 mm in length and less than 10 μm in depth,and there was no evidence of crack tips.Chemical composition analysis showed that crack regions were characterizd by high oxygen concentration while the intact surface was at normal oxygen level.Test results suggest that the occurrence of strip cracks were mainly related to residual oxide on the surface of TA17 alloy cold-rolled sheet.

Study on Hot-dip Aluminizing of Ti6Al4V Alloy

Zhu Tao, Wang Shuqi, Mao Yishu, Wang Haishuai, Yu Jianping

2013, 34(1): 31-34. doi: 10.7513/j.issn.1004-7638.2013.01.007

Abstract(24) PDF(1)

Abstract:
A layer of TiAl₃ intermetallic compound coating was prepared on Ti6Al4V alloy by hot-dip aluminizing,and the obtained sample was treated by thermal diffusion.The coating was analyzed by XRD and SEM to probe into its structure and compositions.The formation mechanism of the coating was also discussed.The results show that after hot-dip aluminizing at 750℃ for 5 min,a coating consisting of pure Al and TiAl₃ alloy(with thickness of 1.5 μm) is formed on the surface of Ti6Al4V alloy;after annealing at 550℃ for 5 h,the thickness of dense TiAl₃ increases to 40 μm and Al layer almost disappears;after annealing at 930℃ for 5 h,all the coating is composed of pure TiAl₃,but lots of holes appear in the coating at the same time.From the coating surface to the alloy matrix,the amounts of holes are in gradient variation.

Research on Decarbonizing and Temperature Increasing During Reblowing and End-Point Control of Converter

He Ping, Liu Liu, Zhao Jinxuan

2013, 34(1): 35-40. doi: 10.7513/j.issn.1004-7638.2013.01.008

Abstract(34) PDF(1)

Abstract:
On the basis of previous studies,rules of decarbonizing and temperature increasing close to the end-point of blowing during converter steelmaking were studied.A reblowing model was established,and the linear regression self-adaptive algorithm was used to achieve dynamic correction of the model's parameters.The results show that there is a linear relationship between total oxygen efficiency of decarbonization and carbon content in liquid steel at reblowing stage,and with application of the model,the precision and hit rates of end-point control have been achieved to meet the need of automotive converter steelmaking.

Production Practice of Hydrogen-induced Cracking Resistant High-strength X65 Pipeline Steel

Wang Jian, Cheng Haitao, Chen Yong, Zeng Jianhua, Yi Lianggang, Zhou Yongjian, Chen Lian, Huang Shengquan, Yu Haibing, Chen Kun

2013, 34(1): 41-48. doi: 10.7513/j.issn.1004-7638.2013.01.009

Abstract(16) PDF(1)

Abstract:
With average [S] of 0.033%(in the range of 0.028%~0.039%),and average [P] of 0.133%(in the range of 0.129%~0.138%) in molten iron to be fed into converter,X65 pipeline steel was successfully produced through dephosphorization by double slag process in converter,modification of ladle slag during tapping,application of double-deck high alkalinity covering agent in tundish,control of LF slag composition,and casting protection with argon.The average [N],T and [P] in the strands were controlled at 0.0035%,0.001 4%,0.002 3%,and 0.009 8% respectively.Inclusions in the strand were rated below 0.5 with total amounts of 0.004 4%.These globular inclusions were small in size and number,exhibiting satisfied internal quality.The mechanical properties of the trial-produced steel achieved the desired effect,and could fully meet the requirements of standards and users.

Research on Sulfur Migration with Pulsed Electric Field Imposed on Slag-metal Interface

Wang Haichuan, Chen Kequan, Ge Yunzong, Liao Zhiyou, Chen Pengfei

2013, 34(1): 49-53. doi: 10.7513/j.issn.1004-7638.2013.01.010

Abstract(11) PDF(1)

Abstract:
Pulsed electric field has been imposed on interface between Fe-C-S alloy and CaO-MgO-Al₂O₃ slag for different durations to study sulfur distribution and migration between metal and slag.The experimental result shows that with the extension of imposing time,sulfur in the slag gradually increases,and evenly distributes on the upper and lower surfaces of Fe-C-S metallic matrix;in addition,inclusions on the metal surface are obviously refined at the same time.The sulfur content in the slag is 0.891 percent and △w_S is 0.001 percent when pulsed electric field imposing time is 60 seconds.

Study on Water Modeling for Optimizing Flow Control Device in Tundish for Three-strand Bloom Casting

Yu Zhuoying, Sun Yanhui, Li Shiwei

2013, 34(1): 54-57,68. doi: 10.7513/j.issn.1004-7638.2013.01.011

Abstract(15) PDF(1)

Abstract:
In view of excessive non-metallic inclusion content in a three-strand tundish for 320 mm×480 mm bloom casting,the effect of flow control device on flow characteristics of the tundish has been studied by water modeling with a geometrical similarity ratio 1:2 to optimize the tundish flow field.The results reveal the problems with the prototype tundish such as short residence time,large dead zone and erosion in the front wall of tundish by continuous flow of molten steel.The residence time is increased by 18.05 s while standard deviation of residence time S_tmin between the two nozzles is only at 0.18 and the dead zone is decreased by 30.15% by using the baffle and dam in scheme 3,which greatly improves the flow characteristic of liquid.

Removal of Non-metallic Inclusions in Non-oriented Silicon Steel by CaSi Wire Feeding During the RH Refining

Zong Zhenyu, Zhang Feng

2013, 34(1): 58-63. doi: 10.7513/j.issn.1004-7638.2013.01.012

Abstract(14) PDF(1)

Abstract:
Experimental study on removal of non-metallic inclusions in non-oriented silicon steel obtained from industrial production by CaSi wire feeding during RH refining process was carried out.The thermodynamics of CaS inclusion formation was analyzed,the morphology and the size distribution of inclusions were observed,and the numbers and types of inclusions were also determined for the steel specimens treated under different calcium treatment conditions.Furthermore,the variation of inclusion characteristics after calcium treatment was discussed.The results show that due to calcium treatment,the formation of MnS and AlN inclusions can be restrained,and the aggregation,flotation and removal of micro-inclusions can be efficiently boosted.As a result,the cleanliness of liquid steel is noticeably improved.The main types of inclusions are single phase of CaO,and some complex inclusions are composed of CaO,SiO₂ and MgO,and no CaS inclusion is found after an appropriate calcium treatment.The size of all the inclusions is in the range of 2 μm to 20 μm,and their amount is about 1.8×10⁵/mm³.

An Investigation into Coal Blending and the Addition of Semi-coke

Du Gang, Yang Shuangping

2013, 34(1): 64-68. doi: 10.7513/j.issn.1004-7638.2013.01.013

Abstract(16) PDF(2)

Abstract:
The grindability,explosibility and ignition point of coal and semi-coke to be injected into blast furnace has been tested to determine the appropriate blending scheme,and the effect of coal blending on coal properties has also been discussed.The results show that through coal blending,the grindability of coal is increased while the explosibility and ignition point of coal are lowered,so the mixture consisting of anthracite,bituminous coal and semi-coke can exhibit better metallurgical properties.

Influence of Cooling Speed on Transformation Behavior of V-N Microalloyed Steel

Zhang Jing, Xing Jun, Wang Kaizhong, Sun Wei, Zhang Weibin, Gong Yanhua

2013, 34(1): 69-72. doi: 10.7513/j.issn.1004-7638.2013.01.014

Abstract(7) PDF(1)

Abstract:
The microstructure transformation of V-N microalloyed steel during continuous cooling process was simulated with Gleeble-3500 thermomechanical simulator.The influence of cooling speed on microstructure and properties of the steel was analyzed.The results reveal that during continuous cooling of V-N microalloyed steel,precipitation of ferrite and transformation of pearlite,bainite and martensite take place.The cooling speed affects the grain size and distribution of ferrite.The critical cooling rate at the end of pearlite transformation is 7.0℃/s.The critical cooling rates at the start of bainite and martensite transformation are 3.0℃/s and 15.0℃/s respectively.

Research on Inclusions in Non-quenched and tempered Sulfur-bearing Steel for Autos

You Dali, Cui Heng, Wu Huajie, Yue Feng, Tian Enhua, Wang Zhenwei

2013, 34(1): 73-78. doi: 10.7513/j.issn.1004-7638.2013.01.015

Abstract(15) PDF(1)

Abstract:
Inclusions in different specimens of non-quenched and tempered sulfur-bearing steel for autos were analyzed with metallographic microscope,scanning electron microscope and energy-dispersive X-ray detector.The result shows that the inclusions in this kind of steel are dominantly in shape of strip,spindle and sphere,distributed dispersedly or in clusters.The inclusions are mainly pure MnS with a small amount of compound inclusions(with core of oxides and nitrides coated with sulfides) and little separate Al₂O₃ and TiN.The compound inclusion are primarily spindle and sphere-shaped(above 90% of them have a length-width ratio of less than 3).Cored or concomitant compound inclusions account for 25% of all the spindled sulfides.High oxygen is ravorable to forming compound sulfides.

Research on Direct Quenching and Tempering Process of High-strength Steel for Engineering Machinery

Lu Feng, Wang Kun, Wang Chao, Wang Zhaodong, Wang Guodong

2013, 34(1): 79-85. doi: 10.7513/j.issn.1004-7638.2013.01.016

Abstract(22) PDF(3)

Abstract:
The microstructure and properties evolution behavior in direct quenching and tempering process of a low-alloy high-strength steel for engineering machinery was studied to provide experimental basis for online production of offline quenched and tempered high-strength steel.Coarse granular bainite structure was obtained under air cooling after rolling and the impact toughness was lowered.All the microstructure obtained was lath martensite when it was fast cooled to below 210℃.The experimental steel exhibited good temper resistance,and the strength was still high enough after high temperature tempering.The comprehensive mechanical properties of the steel under direct quenching and tempering were better than those under offline quenching process.The result shows the advantage of online heat treatment technology under ultra fast cooling condition in the development of low consuming and high performance steel.

Analysis on Appearance and Cause of Scale Defects on the Steel Plate Surface

Chen Liansheng, Lu Junwei, Song Jinying, Tian Yaqiang

2013, 34(1): 86-92. doi: 10.7513/j.issn.1004-7638.2013.01.017

Abstract(18) PDF(2)

Abstract:
The appearance,microstructures and compositions of iron oxide scale on the strip steel surface were studied by means of SEM,EDS and XRD,and the causes of scale defects were analyzed.The results show that there are four main kinds of scale defects on the surface:①primary scale formed during roughing process which has not been removed by high-pressure water descaling box after slab is discharged from the furnace;②press-in of secondary scale remaining from high-pressure water descaling box before finishing process;③press-in of tertiary oxide scale formed on the surface of hot rolled steel coil due to wear of oxide film on roll surface during finishing and the subsequent cooling processes;④formation of red scale especially on the steel with high silicon content due to strong engagement between surface oxides and base metal during slab heating process.

Analysis on Types and Causes of Surface Scab on Steel Plate

Leng Yanhong, Song Jinying, Tian Yaqiang

2013, 34(1): 93-98. doi: 10.7513/j.issn.1004-7638.2013.01.018

Abstract(23) PDF(1)

Abstract:
Main scab defects arising in a hot rolling line were studied through metallographic microscope,scanning electron microscope and energy spectrometer.The results show that the formation of scab defects can be attributed to press-in of welding tumor,entanglement of converter alkaline slag and refining slag into slab,and bubbles in continuously cast strand.After causes and influencing factors of defects were analyzed,countermeasures were put forward,including installing burring device,renovating converter steelmaking and refining process and tundish smelting system,promoting inclusion floating and making reasonable baking mechanism for ladle and tundish,and taking such preventive measure as checking the mold for seepage.

Effect of Austenitizing Time on Spheroidized Microstructure of Bearing Steel GCr15

Guo Lin, Huo Xiangdong, Dong Feng

2013, 34(1): 99-103. doi: 10.7513/j.issn.1004-7638.2013.01.019

Abstract(20) PDF(2)

Abstract:
After hot-rolling and subsequent perforating,austenitizing at 805℃ for different lengths of time and three different spheroidizing annealing processes,the microstructures of bearing steel GCr15 were investigated using optical microscope and SEM.The results show that there are two types of microstructures in the GCr15,including relatively big proeutectoid carbide particles and small carbide particles.As time prolongs at a holding temperature of 805℃,the lamellar pearlite gradually disappears,and small carbide particles are also reduced in number and become smaller in size while the size and distribution pattern of proeutectoid carbide particles remain basically unchanged.The hardness of specimens is similar under three spheroidizing annealing processes.

2013, 34(1): 104-106.

Abstract(24) PDF(1)

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2013 Vol. 34, No. 1