钢铁钒钛

Metallurgical Benefits of Vanadium Microalloying in Producing High Strength Seismic Grade Rebar

David Milbourn, Li Yu

2012, 33(2): 1-9.

Abstract(21) PDF(1)

Abstract:
It is essential to select appropriate materials for reinforcing bars（rebars） in order to assure adequate seismic performance,and there are several international standards defining specifications.The critical properties of seismic resistant rebars have been identified and the pros and cons of the popular manufacturing processes,quenching and self tempering（QST） and microalloying（MA）,have been reviewed.It has been shown that vanadium microalloying provides the best combination of properties,fulfilling all of the essential performance criteria,as well as minimising problems during important fabrication operations and offering ease of use benefits for the steelmaker during casting and rolling.

Study on the Preparation Technology of High-density APV

He Wenyi, Wang Xiaojiang, Peng Yi, Yin Danfeng

2012, 33(2): 10-14.

Abstract(20) PDF(1)

Abstract:
A new process to prepare high-density APV is introduced and the effects of TV concentration,pH value,stirring rate,temperature before adding reagent and acid,ammonium adding coefficient and seed crystal on bulk density and precipitation ratio of APV are investigated.The results show that following adding seed crystal with its mass more than 1/50 time that of TV and（NH₄）₂SO₄ with its mass more than 1.5~2.5 times that of TV to the solution containing 20~30 g/L of vanadium between 60~85 ℃,and adjusting pH value of the solution to 2.1~2.4,the solution is precipitated for 40 min at 350 r/min and 20 min at 200 r/min in boiling water bath under 95 ℃.Precipitation ratio and bulk density of dried APV can reach above 98.5% and 0.95 g/cm³ respectively.As a result,V₂O₅ powder contains more than 98.5% of V₂O₅ and less than 0.10% of Na₂O after APV is roasted.

Experiment on Preoxidation and Hydrogen Reduction of Ilmenite in the Fluidized Bed

Tan Liang, Gu Wu'an, Yuan Xizhi

2012, 33(2): 15-19.

Abstract(21) PDF(1)

Abstract:
Using ilmenite as raw materials to produce titanium slag by hydrogen reduction in the fluidized bed can not only expand sources of raw materials and lower energy consumption,but also realize cleaner production.On the basis of cold test,preoxidation and hydrogen reduction of ilmenite in the fluidized bed was studied and effects of temperature,reduction time,particle size of ilmenite and the pressure of H₂ on metallization of Fe were investigated.The results indicate that metallization of Fe increases markedly with the rise of reduction temperature between 800 ℃ and 950 ℃;metallization of Fe increases rapidly at the beginning and then tends to slow down under the same reduction temperature;metallization of Fe increases remarkably with the decrease of particle size of ilmenite;the concentration of H₂ has so strong an effect on the metallization of Fe that the reduction rate rises dramatically with higher concentration of H₂.

Influence of Magnesium Addition on Preparation of Nano-TiC Powder

Zheng Zhuo, Zhou Dali, Yu Chong, Hu Chi, Zhao Xin

2012, 33(2): 20-25.

Abstract(21) PDF(1)

Abstract:
In the experiment,TiC precursor was produced by sol-gel process using Ti（C₄H₉O）₄ and phenolic resin as titanium source and carbon source respectively.Then the so prepared TiC precursor was mixed with the catalyst of Mg powder to produce nano-TiC powder by carbothermic reduction process.The phase and morphology of samples were characterized by XRD and SEM.Generally,pure TiC powder can only be prepared from TiC precursor at 1 380 ℃ by carbothermic reduction process,but the test results indicate that as Mg powder is added and increased,the temperature of carbothermic reduction process can dramatically be lowered,so pure TiC powder can be produced at 1 200 ℃.The addition of Mg powder also reduces the proportion of carbon source in the reactants and restrains the growth of TiC grain.Thus,granularity of the TiC powder is uniform with the grain diameter around 50~100 nm.

Preparation of Crude Vanadium Alloy by Aluminothermic Process

DENG Bin

2012, 33(2): 26-29.

Abstract(19) PDF(1)

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Vanadium pentoxide and aluminum powder were used as raw materials to prepare crude vanadium alloy for electrorefining by aluminothermic process in the shaft furnace.The influences of unit thermal value of burden and aluminum coefficient on V recovery and Al content in the alloy were studied.Stability test results show that under the conditions of 4 080 kJ/kg of unit thermal value of burden and 100% of aluminum coefficient,the alloy obtained contains 92.65% of V and 2.79% of Al in average,and the average recovery rate of vanadium is 84.34%,which meet the requirements of vanadium metal preparation by electrorefining process.

A New Low-temperature Reduction Technology for Vanadium-bearing Titaniferous Magnetite

Pang Jianming, Guo Peimin, Zhao Pei

2012, 33(2): 30-33.

Abstract(16) PDF(2)

Abstract:
A new low-temperature reduction technology for vanadium-bearing titaniferous magnetite was developed based on extensive investigation of its special properties.The new technology is efficient in utilization of resources and energy,as it lowers the reaction temperature and eliminates the subsequent electric smelting process.The new technology has the advantages of low-energy consumption,flexibility in smelting,no pollution,low investment and low prodution cost.

Simulation Experiment on Direct Reduction of Oxidized Pellets of Vanadium and Titanium-bearing Iron Concentrates by Gas-based Shaft Furnace

Wang Zhaocai, Chen Shuangyin, Chu Mansheng, Han Ziwen, Xue Xiangxin

2012, 33(2): 34-39.

Abstract(18) PDF(1)

Abstract:
Vanadium-bearing titaniferous magnetite resources are abundant in China,but most of them are difficult to be utilized efficiently because of current technical problems with industrial practice,so further efforts should be made to innovate existing technologies.The process of direct reduction by gas-based shaft furnace-smelting and separation by electric furnace provides a new way to efficiently and cleanly utilize the resources.In the experiment,oxidized pellets are prepared from vanadium and titanium-bearing iron concentrates.By simulating direct reduction conditions of gas-based shaft furnace,the effects of reducing gas composition and temperature on pellets’ reduction course,swellability and intensity have been investigated.The results shows that the oxidized pellets prepared from vanadium and titanium-bearing iron concentrates（1% of bentonite is added into it） roasted at 1 250 ℃ for 20 min exhibit excellent properties and possess high compressive strength.Under controlled experimental conditions including composition of reducing gas（pure H₂,H₂/CO=2.5,H₂/CO=1,H₂/CO=0.4 and pure CO） and temperature（850 ℃,900 ℃,950 ℃ and 1 000 ℃）,the resulted pellets boast fast reaction rate and small reduction swellability and can meet the requirements of direct reduction in shaft furnace.Thanks to its advantages in energy saving,environment protection,greater single-machine capacity and high product quality,the process of coal gasification-direct reduction by shaft furnace is expected to be developed aiming at efficient and clean utilization of vanadium-bearing titaniferous magnetite.

Technical Analysis on Oxygen Blast Furnace Ironmaking Process

Gao Jianjun, Qi Yuanhong, Zhou Yusheng, Yan Dingliu

2012, 33(2): 40-45.

Abstract(22) PDF(1)

Abstract:
A numerical simulation of the oxygen blast furnace is established in this paper.The results show that fuel consumption can be reduced by 5% when top gas of the oxygen blast furnace is recycled and CO₂ emissions can be reduced by more than 56% when CO₂ in the top gas is stored and utilized.Industrial tests of the oxygen blast furnace indicate that,order to achieve low-cost production,four key problems are to be solved,namely,high injection efficiency,full-process control,recycled gas heating,CO₂ removal from the top gas,CO₂ storage and utilization.Meanwhile,proposals for development of the oxygen blast furnace iron-making process are put forward.

Study on Alloying by Nitrogen Blowing During AISI410 Stainless Steel Refining with LF

Zhou Shucai, Yang Jie, Yang Yongjun

2012, 33(2): 46-49,76.

Abstract(16) PDF(1)

Abstract:
The effects of nitrogen blowing time,nitrogen flow rate and liquid steel temperature under normal atmospheric condition on nitrogen content were tested and studied during AISI410 stainless steel refining with the 40 t LF and the control model of nitrogen alloying during LF refining was established.The experimental results show that with increase in nitrogen blowing time and nitrogen flow rate,the nitrogen content in liquid steel increased;the nitrogen content in liquid steel was more than 0.05% in the case of nitrogen blowing for 10 min under normal atmosphere;with increase in nitrogen flow rate,the time for saturation of nitrogen in liquid steel was shortened and with decrease in liquid steel temperature,the solubility of nitrogen increased.The analysis on nitrogen solubility was carried out by thermodynamic model and the nitrogen content so calculated agrees quite well with the measured one,which provides reference for controlling nitrogen content by blowing nitrogen gas during stainless steel refining with LF.

Research on Submerged Entry Nozzles Clogging During Non-oriented Silicon Steel Casting by CSP Process

Li Wenguang, Sun Yanhui, Wang Xiaosong, Qiao Zheng, Xiong Huihui, Cai Kaike

2012, 33(2): 50-55.

Abstract(21) PDF(1)

Abstract:
Clogging behavior of submerged entry nozzles during non-oriented silicon steel（with aluminum content of 0.3%~0.4%）casting by BOF-LF-RH-CSP process in a domestic steel mill was investigated.By way of systematical sampling,optical microscope observation,SEM analysis and mineralogical phase analysis,the structure and compositions of the clogging substance were identified and the clogging mechanism was briefly clarified.It was found that the process of Ca treatment,which generated a lot of CaS,was the major factor to clogging.By improving the production process,the sequential heats during non-oriented silicon steel casting by CSP process increased from 5 to 8 or above,resulting in higher production efficiency without sacrificing the requirements of quality.

Effect of M-EMS on Carbon Segregation of Gear Steel Round Bar Rolled from Rectangular Bloom

Xu Ruijun, Yan Huicheng, Wu Qingming, Xu Weiyang, Cao Zhigang, Yang Genchao, Liu Jian, Liu Yonglong, Qiu Shengtao

2012, 33(2): 56-61.

Abstract(14) PDF(1)

Abstract:
Effect of different M-EMS strength on carbon segregation of gear steel round bar rolled from rectangular bloom is investigated by analyzing the carbon distribution and etched macro-structure.The results show that the CET rectangle is enlarged and equiaxed crystal rate rises with M-EMS,but a band of negative carbon segregation appears under the surface of round bar and the carbon segregation rectangle is apparent in macrostructure.An N-shaped carbon segregation appears from surface to center of the bloom and round bar under M-EMS and the segregation becomes more intensified with stronger stirring.The carbon difference is large at 3/4 R circle,1/2 R circle and small at 1/4 R circle in same round bar circumference with M-EMS,but reversal without M-EMS.The bloom and round bar are subject to the same carbon segregation rules,and the carbon distribution is strongly related to the etched macrostructure.There is an inherited relation between bloom and round bar in carbon segregation and macrostructure.

Experimental Research on Use of V-bearing Titaniferous Magnetite for Sintering in Desheng Chuangang Steel

Du Changkun, Mai Jichang, Luo Qingming, Yuan Xiaoli, Wan Xin, Liu Hao

2012, 33(2): 62-66.

Abstract(19) PDF(1)

Abstract:
In view that high proportion of V-bearing titaniferous magnetite is used at the sinter plant of Sichuan Desheng Iron and Steel Co.,effects of proportioning of V-bearing titaniferous magnetite and basicity on sinter performance were investigated in the lab.The results show that in order to meet the requirement of productivity and quality of sinter,save energy and reduce cost based on the existing raw material,fuel and ore matching in Chuanggang,the desirable proportion of V-bearing titaniferous magnetite is 45% and reasonable basicity is 2.3.

Design and Application of Blast Furnace Casthouse Refractory for Smelting Vanadium-bearing Titaniferous Magnetite

YANG Qiang

2012, 33(2): 67-70.

Abstract(14) PDF(1)

Abstract:
Properties of blast furnace slag from vanadium-bearing titaniferous magnetite smelting is investigated.The damage mechanism of the dry-out rammed mixture for iron runner is analyzed and influence of the sintering and anti-adhesion compound additive on the performance of the rammed mixture is probed.The results show that appropriate amount of compound additives can improve the strength and slagging resistance of material.The newly designed dry-out rammed mixture for the runner has efficiently resolved the problems of slag sticking,which prolongs the service life to 7~9 days from 3~5 days.

Effect of Heating Temperature on Precipitation and Property of Ti-Nb Composite Microalloyed High-strength Steel

Gan Xiaolong, Yue Jiangbo, Zhang Qing

2012, 33(2): 71-76.

Abstract(20) PDF(1)

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A low-carbon high-strength microalloyed steel was smelted in laboratory.Rolling,redissolving and tensile tests were performed.In addition,microstructure of the rolled steels was observed and the morphology,type and size of precipitates at different reheating temperature were analyzed.The results show that property of the sample heated at the temperature of 1 280 ℃ is superior to that of sample heated at 1 180 ℃;the microstructures of these steels under the two temperature schemes consist of ferrite and pearlite with basically the same grain size;and the（Ti,Nb）（C,N） composite precipitates,but the precipitates of the sample heated at 1 280 ℃ are smaller and more in quantity.The calculation based on precipitation hardening theory indicates that the precipitation hardening of the sample heated at high temperature is 131 MPa higher than that of low temperature-heated specimen.Furthermore,redissolving experiment shows that the precipitates virtually dissolve in steel as the sample is heated to 1 280 ℃ and kept at the temperature for 1.5 hours,while the precipitates cannot fully dissolve in steel as the sample is heated to 1 280 ℃ and kept at the temperature for 1.5 hours,which proves that heating temperature has a strong influence on the precipitation hardening of Ti-Nb composite microalloyed steel.

Analysis on Mechanical Property and Microstructure of Low Carbon Bainite Steel Q550 for Engineering Machinery Use

Liu Nianfu

2012, 33(2): 77-81.

Abstract(19) PDF(1)

Abstract:
The production of the high strength steel plate Q550 with thickness of 30 mm for engineering machinery use in Shaogang is introduced.Using low carbon and microalloyed elements such as Nb,V,Ti,Mo etc.plus TMCP and off-line tempering process,the plate was produced with mechanical properties satisfying the delivery requirements.In addition,the microstructure of the plate is examined by OM,SEM and the precipitated phase analysis by TEM and EDS.The results indicate that the tempered Q550 plate exhibited a microstructure of granular bainite,acicular ferrite and a small amount of polygonal ferrite with fine and uniform grain;The major precipitated phases were carbonitrides of Nb and Ti while V and Cr contribute little to the precipitation strengthening of Q550 plate.

High-temperature Microstructure and Mechanical Performance of As-cast 2205 Duplex Stainless Steel

Li Yan, Du Zhongze, Hu Kuntai

2012, 33(2): 82-86.

Abstract(29) PDF(1)

Abstract:
High-temperature short-time tensile test of as-cast 2205 duplex stainless steel was performed and the variation of tensile strength and percentage reduction in area of the specimen at different temperatures was analyzed.The high-temperature microstructures and fracture morphologies were observed at 1 300 ℃,1 050 ℃,950 ℃ and 850 ℃.The test results showed that duplex stainless steel exhibited good plasticity at 1 150~1 350 ℃.Softening was inhibited due to high strain rate at 1 000~1 100 ℃,resulting in a brittleness temperature range Ⅱ present in the duplex stainless steel.In addition,crack propagated further due to loose and fine precipitation of the specimen.Presence of brittleness temperature range Ⅲ was the result of grain boundary embrittlement mainly caused by the nitride and carbonitride etc.precipitated at austenitic grain boundaries.

Steel Edge Cracking Analysis and Improvement Measures

Song Jinying, Dong Shuangpeng, Chen Yexiong, Zhang Bingqing, Chen Liansheng, Tian Yaqiang

2012, 33(2): 87-92.

Abstract(11) PDF(1)

Abstract:
In order to study the surface quality of the edge-cracking steel sheet and find out the root causes of defects,microscope,scanning electron microscopy,energy dispersive spectroscopy and other related test equipments were employed.The results showed that there were four fundamental casues of steel edge cracking: inclusions,severe decarburization at the steel edge,uneven cooling along transverse direction and accumulation of blowholes.In response to the above-mentioned causes,improvement measures such as optimization of steelmaking process,continuous casting,heating scheme and transverse cooling process at rolling section were taken to decrease the slab defect rate due to edge cracking from 30% to 5.1%,resulting in reduction of side trimming.The results provide helpful reference to production practice and quality disputes resolution.

Analysis on Narrow Side Bulging of Slab and Improvement Measures

Wang Wenxue, Liu Cailing, Yang Chaowu, Zeng Jing, He Yuming, Li Deqing, Wang Haibin

2012, 33(2): 93-95.

Abstract(18) PDF(1)

Abstract:
Bulging of 7~8 mm appeared at the narrow side during casting 300 mm thick 16Mn slabs with 3^# caster of Chongqing Iron and steel Company.Problems during casting were identified,such as weak cooling intensity of mold especially at narrow side,too small taper at the narrow side and taper change of narrow side foot roller.After optimizing the structure of narrow side foot roller,taper of mold,alignment of copper plate and narrow side foot roller and secondary cooling of narrow side foot roller,the mold was brought to normal operation.Operating practice indicated that the greatest taper change of the improved mold was merely 0.5 mm and bulging at narrow side smaller than 2 mm.

2012, 33(2): 96-98.

Abstract(15) PDF(1)

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2012 Vol. 33, No. 2