钢铁钒钛

Experimental Study on Leaching Vanadium by Sub-molten Salt Method

Cao Laizong, Liu Daijun, Gao Lihua, Liu Changhong, Shen Qian

2008, 29(2): 1-4.

Abstract(49) PDF(2)

Abstract:
Considering that the recovering V₂O₅ by roasting leads to some serious problems such as environment pollution,high energy consumption and low conversion efficiency at present,the influencing factors of leaching vanadium from ore with the composite sodium agent are studied in this paper by sub-molten salt method.The investigation involves many hands including analyzing the primary and secondary relations of these factors by orthogonal test,and further researching the effects of liquid-to-solid ratio,the adding content of chloride salts and reaction time on vanadium leaching efficiency.The results show that the leaching efficiency of V₂O₅ is higher than 90% in the condition of agent concentration 70%,liquid-to-solid ratio 5:1,the ratio of chloride salts 45 and reaction time 2.5 h.Taking sub-molten salt method can resolve some problems to recover V₂O₅ caused by roasting,and provide a new way for extracting V₂O₅ from wet process.

Study on Thermochromic Properties of the Mo-doped VO₂ Thin Films on Muscovite Subtrate

Zhang Yue, Yan Jiazhen, Huang Wanxia, Liu Xiaojie, Tu Mingjing

2008, 29(2): 5-8.

Abstract(35) PDF(1)

Abstract:
In this paper,Mo-doped vanadium dioxide thin films were fabricated on muscovite slice using an inorganic sol-gel method.XRD,AFM,XPS and FTIR were used to investigate the microstructure,morphology and phase transition temperature.The results revealed that VO₂ film was(011) preferred orientated on muscovite substrate.When the doped Mo ions concentration enhance 1%,the phase transition temperature decreased 7.82 ℃.The temperature width of hysteresis decreased and the orientated VO₂ films exhibited excellent optical switching property after Mo doping.

Effects of Coiling Temperature on Microstructures and Mechanical Properties of Micro-alloyed Rephosphorized Steel Sheet

ZHENG Zhiwang, GOU Shuyun

2008, 29(2): 9-13.

Abstract(58) PDF(1)

Abstract:
Effects of coiling temperature(600、650 and 700 ℃,respectively) on the microstructures and mechanical properties of micro-alloyed rephosphorized steel sheet were investigated by analyzing its microstructures and mechanical properties in as hot-rolled and as annealed conditions as well as its recrystallization dynamic behaviors during annealing.The results showed that the microstructure and properties of the experimental steel sheet were obviously affected by the hot-rolling coiling temperature and its recrystallization was prohibited significantly,resulting in higher activation energy for recrystallization,when the coiling temperature was decreased from 700 ℃ to 600 ℃.It was also found that the grain sizes at as hot-rolled or as annealed conditions were both little affected by the coiling temperature whereas not only the as hot-rolled strength and as annealed strength were increased as the coiling temperature decreased,but also the mechanical properties at as annealed conditions became more sensitive to annealing temperature.

Influence of Liquid Core Reduction on Mechanical Properties of High Strength Weathering Steels in Thin Slab Casting and Direct Rolling Process

SU Liang, TIAN Naiyuan, MAO Xinping, LIN Zhenyuan

2008, 29(2): 14-17.

Abstract(64) PDF(1)

Abstract:
Ti-microalloyed High Strength Weathering Steel was first produced by CSP process at Zhujiang Steel Co.,Ltd.,Effects of two different processes(with LCR or without LCR) on the mechanical properties and microstructure of the slab and strip were discussed.The results showed that all strips were of very fine microstructure and excellent mechanical property,but mechanical properties of slab by LCR are more homegeneous,properties of strip are slightly better contrast with one of without LCR.And thickness of continuous casting slab just fit with direct rolling.

Influence of Australian Ore on Microstructure of Sinter

LIU Lina, HAN Xiuli, BAI Limei

2008, 29(2): 18-22.

Abstract(38) PDF(1)

Abstract:
Ao mine and sinters were observed by optical microscopy.The results showed that the structure of Ao mine is loose,The primary compositions are hematite and limonite,existing as the xenomorphic granular state.While the Ao mine content of sinter increased from 10% to 50%,the content of calcium ferrite increased,the content of magnetite,dicalcium silicate and glassiness decreased, the sintering microstructure changed from porphyritic structure to intertwining melting structure.The microstucture lead to the increasing of sinter intensity.

Effect of Welding Velocity on Properties of Welding Joint of Austenitic Stainless Steel

QIN Bin, WANG Baosen

2008, 29(2): 23-26.

Abstract(53) PDF(1)

Abstract:
The MIG welding research on 304 austenitic stainless steel plates with 3 mm thick was carried out.The results showed,fast welding velocity is benefit to enhancing joint's quality,because faster welding velocity may help to reduce the region of welding seam and heat affect zone.But too fast welding velocity is not good because of the produce of pores,and the joints will suffer from low strength stability and poor anti-corrosion.Appropriate welding velocity will keep 304 austenite stainless steel welding joints having good mechanical properties and corrosion resistance.

Effect of V₂O₃ and Al₂O₃ Addition on Iron Carbide Formation

HE Qiang, LI Guangqiang, WU Shici, MA Jianghua

2008, 29(2): 27-31.

Abstract(45) PDF(1)

Abstract:
Iron carbide was produced by reacting of iron ore with(H₂+CH₄) gas mixture at 1 023 K.The effects of V₂O₃ and Al₂O₃ additives on iron carbide formation were experimentally investigated by thermogravimetry and XRD analysis.It was observed that the addition of V₂O₃ had significantly promoting effect on both iron ore reduction and iron carbide formation.The V₂O₃ addition also increased the conversion yields from iron ore to iron carbide,and improved the stability of iron carbide.When the content of the V₂O₃ was within 1 percent,with the content increasing,the rate of iron ore reduction and carbonization all accelerated notablely.When the content of the V₂O₃ was 2 or 3 percent,the reduction rate and the carbonization rate of the specimen were both smaller appreciably than that when the V₂O₃ content was 1 percent.It was also observed that the addition of Al₂O₃ had promoting effect on reduction of iron ore to some extent,but it has bad effect on the stability of iron carbide.

Analysis on Microstructure of Solidified Film of Casting Powder for Low-carbon Steel

HAN Xiuli, YANG Huiping, LIU Lina

2008, 29(2): 32-36.

Abstract(59) PDF(1)

Abstract:
The microstructures of accidental film and adjusted film for low-carbon steel have been studied,accidental reasons have been analysed,and the way is point out to improve performance of lubricity and heat conductivity of casting powder and quality of slab by controlling the solidified film structure and mineralogical phase.Casting powder for low-carbon steel should possess good heat conductivity and low crystal rate.so,It is necessary to decrease crystal rate and increase glassy tendency of film,and avoid forming some mineral like K-Na-feldspar、Plagioclase、nephelite、cuspidine in solidfied film.All things considered,especially lubricity and heat conductivity,wollastonite、melilite in solidfied film are good.After adding B₂O₃ and LiO₂,crystal size was decreased,glassy tendency was increased,and the quality of slab was improved obviously.

Physical Simulation of MetalSlag Mass Transfer in Gas Stirred Ladles

GAN Lei, HE Ping

2008, 29(2): 37-42.

Abstract(50) PDF(1)

Abstract:
The mass transfer of benzoic acid between water and oil has been performed to simulate the mass transfer processes of metallurgical reactions in gas stirred ladles, and effects of gas flow rate, slag volume, tuyere positions on mass transfer rate have been studied when the rate controlling process is mass transfer in slag.The results show that mass transfer rate increases with the increasing of gas flow rate, and increases abruptly at a critical gas flow rate, for mass transfer of benzoic acid the dependence of kA on Q was kA∝Q^0.20 in low gas flow region and kA∝Q^0.80 in high region, the abrupt rate increase is due to increase of interface area begotten by entrapment of slag;mass transfer rate also increases with increasing of slag volume;centric gas bubbling could reach higher mass transfer rate than off-centric positions, so it is suggested that the determine of optimum tuyere position should based on both mixing time and mass transfer rate.

Numerical Simulation of Mold Electromagnetic Stirring in 280 mm × 380 mm Bloom Continuous Casting

CHEN Yong, ZHU Miaoyong, CAI Kesen, YANG Xiaodong

2008, 29(2): 43-49.

Abstract(67) PDF(3)

Abstract:
In order to simulate the magnetic induction density and electromagnetic stirring force in 280 mm×380 mm continuous bloom casting mold,a mathematical model was presented according to Maxwell electromagnetic field theory.On this basis,the distribution of the magnetic induction density and electromagnetic stirring force were analyzed.Numerical simulation results show that the rotating magnetic field can generate the electromagnetic force in mold region,which makes molten steel whirl in level section.The magnetic induction density changes linearly with the stirring current intensity,while the effect of lower stirring frequency on the magnetic induction density is slight.

Coupled Numerical Simulation on the Process of Molten Steel Flow and Heat Transfer of Six-strand Tundish

ZHANG Caijun, LI Jiansheng, CHENG Cuihua, BI Na

2008, 29(2): 50-54.

Abstract(52) PDF(2)

Abstract:
The method of coupled numerical was taken on the heavily temperature dropping of six-strand special unsymmetrical tundish.The flow field and temperature field in the tundish were calculated and optimized.The result show that when the special tundish was used without any flow control devices,it had a very short flow route between entry and near outlet,the biggest temperature difference between near outlet and far outlet is 8 ℃;The optimized tundish avoid the short flow route and uniform the molten steel temperature of each nozzle,and the biggest temperature difference reduced to 3.3 ℃.It is better than the original one and meet the requirement of actual operations.

Analysis of Cracking Reasons in the Cold Heading Process of SWRCH35K Steel

LIU Zengxun, PEI Pei, AI Liqun

2008, 29(2): 55-59,66.

Abstract(70) PDF(3)

Abstract:
Cold heading steel is used to make the standard unit.The products tend to crack on the surface due to limited plasticity of materials.To improve properties of cold heading steel and product qualified rate,the cracking reasons of SWRCH35K bolt in the cold-heading process were investigated by acid washing,metallographical detection and energy spectrum analysis.Surface quality,metallurgical structure,crystal grain size and non-metallic inclusion were studied.The results show that surface folding defect of wire rod and segregation in the slab is the cracking reason for cold heading.At the same time the corresponding improving measures are put forward.

Influencing of Temperature on Plating Microstructure of Galvalume Sheet Steel

LI Dadong, LIU Jinyan, CHEN Wenlong

2008, 29(2): 60-66.

Abstract(45) PDF(1)

Abstract:
The change of plating microstructure was investigated by microscope and SEM,when the Galvalume sheet steel was tested in diverse high temperatures.It was showed the color of surface didn't change when temperature was in 300~450℃,but the Galvalume branching crystal cracks expanded larger and larger,as the temperature was higher.The Al-Si-Fe alloy stratum was formed and it's distribution developed from intermittence to continuum,it's thickness was increasing,So that plating cracking and desquamating with base sheet steel,the corrosion resistance decreased.The plating was all alloyed and oxide to change color quickly when temperature was in 500,it complete lost corrosion resistance in the end.

Analysis and Control on the Edge Cracking of Hot-Rolled Strips

CHEN Wei, SU Hezhou

2008, 29(2): 67-72.

Abstract(59) PDF(2)

Abstract:
The cause of edge cracking defect of hot-rolled strips was investigated and analyzed by metallographic microscope,SEM and process investigation.The results showed that bad deoxidization during smelting and the unstable casting operation are the main causes for continuous edge cracking of strips;The overheating and overburning of slab during ready rolling stage are the main causes for non-continuous edge cracking of strips.According to study results,the process was optimized and better results were obtained,the rate of edge cracking defects of slab decreased from 80~85 heats/month to 4~5 heats /month,the continuous edge cracking of hot-rolled strips was almost eliminated and the rate of the noncontinuous edge cracking of hot-rolled strips decreased from 17.6% to 1.2%.

2008 Vol. 29, No. 2