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2013 Vol. 48 No. 4
Published: 2013-04-15
Technical Reviews
Steelmaking
Metal Forming
Materials
Environmental Protection and Energy
Technology Exchange
Technical Reviews
1
YANG Cai-fu
Recent Development of Vanadium Microalloying Technology
Recent developments of V microalloying technology and its applications in HSLA steels were reviewed. Enhanced-nitrogen in V-containing steel can promote precipitation of fine V(C, N) particles, and improve markedly precipitation strengthening effectiveness of vanadium, therefore, there is a significant saving of V addition in the same strength requirement. Vanadium can be used effectively for ferrite grain refinement by the nucleation of intragranular ferrite promoted by VN precipitates in Austenite. Nanoscale V(C, N) particles can be precipitated in bainitic ferrite matrix over a broad temperature, and the precipitation strengthening might be successfully applied in bainitic steels. V-N process is a cost-effective way for high strength rebars, section steels, forging steels and thin slab direct rolling strips.
2013 Vol. 48 (4): 1-11 [
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Raw Materials and Ironmaking
12
CHEN Chuan,CHENG Shu-sen,GUO Xi-bin
Influencing Factors of Blast Temperature
Two-dimensional mathematical model of checker chamber was developed. Comparison between the calculated results and actual measured data in Xuansteel was done in order to verify the availability and accuracy of the mathematical model. The influence of checker brick design, dome temperature, mixed air operature and operating period on blast temperature was studied. The results show that: for each diameter of checker brick, there should be an optimal relative open area. Blast temperature can be enhanced by optimizing the correspondence between diameter and relative open area. When the preheating temperature of gas and air increase 100℃, the dome temperature and blast temperature will increase 80℃ and 72℃, respectively. Shortening operation period can significantly improve the blast temperature. It should choose reasonable operation period according the combustion burner ability in order to guarantee the gas and air mixing and burning efficiently.
2013 Vol. 48 (4): 12-17 [
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18
LI Qiang
Intelligence Control for Rotation Speed of Sintering Exhaust Fan in TISCO
The relationships among rotation speed of main exhaust fan, air volume, sintering machine speed and FFS (front flame speed) was analyzed and the sinter production process was stabilized by adjusting the rotation speed of new adapted converter controlled main exhaust fan. A FFS-based automatic control system for rotation speed of main exhaust fan was developed. The stability of FFS was remarkably improved and burn-through point (BTP) was stabilized at the penultimate wind box. Under the assistance of this system in the sintering plant of TISCO, the stability rate of BTP in the penultimate wind box is up to 98.1%, which is 35.5% higher than manual control, while the rate of return fine was reduced by 3.46%. The advantage of the converter controlled main fan can be enhanced by the system. The power consumption of the main exhaust fan can be reduced by 28.6%, comparing to power frequency running.
2013 Vol. 48 (4): 18-23 [
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24
ZHAO Hong-bo, ,HUO Shou-feng，,HAO Jing-wei,CHENG Shu-sen
Discussion on Security Early Warning Mechanism of BF Hearth
Lots of blast furnaces (BFs) recently face the problem of hearth severe erosion even burnt out accidents. The campaign life of hearth has become the limiting factor for safe and high efficiency production of modern BFs. However, the early warning mechanism of hearth has not been clear due to the lack of system research. Based on the heat transfer calculations, heat load and erosion monitoring for various BF hearths with different volume, structure and refractory, the features of heat load and erosion for different kind hearth were compared and analyzed. The primary detecting elements, software models, evaluating standards and warning methods were discussed. The early warning mechanism of modern BF hearth was proposed.
2013 Vol. 48 (4): 24-29 [
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Steelmaking
30
WANG Yi-fang,HU Zhi-gang,ZHAO Ying-li,LI Jie
Optimization of Power Supply System and Electric Characteristic for LF
The electric characteristic curves for Hebei Steel 150t LF were analyzed by using electric characteristic optimizing model. The reasonable electric supply systems were proposed according to work point technical parameters of first four levels; the optimization efficiently reduced refining time and improved heating efficiency. The results show that the speed of heating-up of 150t ladle furnace is from 2.46 to 4.25℃/min for the first four levels. Through optimizing power supply system, the heating-up speed can be improved 0.93℃/min and power factor at heating stage is increased from 0.5 to 0.72, heat efficiency is increased from 0.68 to 0.82, and the cost of product is reduced four yuan/t.
2013 Vol. 48 (4): 30-34 [
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35
WANG Hai-bao,,ZHANG Jiong-ming,ZHAO Xin-yu,LIU Yang,WANG Wen-jun,ZHEN Xin-gang
Effect of Cooling Pattern on Surface Microstructure of Slab
The samples of diameter 10 mm were made to simulate slab surface. The experiment was made to control the samples cooling at traditional cooling pattern and controlled cooling pattern respectively. Furthermore, the microstructure of transverse section was observed under a metallographic microscope to study the influence on microstructure of slab surface of cooling pattern. The experiment results are as follows: Using traditional cooling pattern, the microstructure is massive ferrite and pearlite by the side of the sample. The grain sizes are between 10-200μm. Moreover the microstructure is strip ferrite, acicular ferrite and pearlite at the center area, the grain sizes are bigger, and the microstructure is uneven. Under controlled cooling conditions, the microstructure is massive ferrite and pearlite. The grain sizes are between 9.36-12.25μm and that the grains are small and the microstructure is even. The controlled cooling pattern can promote refinement grains to increase the hot ductility of slab surface, which will have positive effect on avoiding the occurrence of surface transverse cracks.
2013 Vol. 48 (4): 35-39 [
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Metal Forming
40
YU Bin,WANG Yi-dong,YANG Xu,GUO Bao-an,LIU Hong-min
Research of Work Roll Same Width Rolling Kilometer for Local High Point Control
For the urgent need of meeting market and saving energy, the research of work roll same width rolling kilometer was put forward, and the simulation system of strip profile was established based on coupling the metal deformation model and rolls elastic deformation model etc. Taking local high point of strip as control object, the relationship between same width rolling kilometer and local high point was researched in different rolling mode. The simulated calculation and production experiment shows that work roll rolling kilometer is obviously restricted by same width strip in ordinary rolling mode, compared to ordinary mode, the reasonable shift roll rolling can greatly improve same width rolling kilometer, and local high point of strip is effectively controlled, therefore the research results has the important direction meaning and practical value for organizing production and making change roll system.
2013 Vol. 48 (4): 40-44 [
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45
WANG Yun,LIU Cai,MA Li-dong,WANG Yu-feng,HUANG Qing-xue
Design of Concave Roller Shape for Two-Roll Straightener
The rollers of two-roll straightener in a rolling mill were needed to be imported and very expensive. Based on the study for the change law of residual curvature and roller shape calculation method, and combined with the finite element computing for straightening process, degree of plastic deformation and straightness of bar were analyzed. Then bending curvature was corrected and the corresponding roller shape was computed. At the same time the corresponding finite element model was computed until straightness of bar met the requirement. So the reasonable bending curvature was chosen and then the concave roller shape was obtained. The roller shape was contrasted with real roller and the shapes were basically identical.
2013 Vol. 48 (4): 45-50 [
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51
WANG Hai-yuan
Backup Roll Shape Optimization of 4100mm Wide-Thick Plate Mill Through Simulation Analysis
Contact pressure and its’ distribution mode between backup roll and work roll are critical to flatness and service life of rollers. In order to investigate the pressure distribution law and make it more uniform, a thermal-deformation coupled finite element model was setup for wide-thick plate rolling process in a 4100mm mill based on elastic-plastic nonlinear finite element method, and the deformation of both hot plate and rolls was coupled in this model. From the numerical simulation results, the contact pressure distribution and roll gap shape are presented, by which, the backup roll profile curve is optimized to be quadratic and its’ shoulder form is improved to be parabolic curve. The service life of backup roll and flatness of plate are improved with the new roll profile.
2013 Vol. 48 (4): 51-54 [
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Materials
55
GONG Ming-long,LIU Feng-fang,ZHAO Xiang,ZUO Liang
Effect of Cooling Rates on Abnormal Microstructure in Fe-1.1%C Alloy Under High Magnetic Field
The microstructure features of abnormal microstructure during transformation from austenite and the hardness of specimens heat treated at different cooling rates (1, 2 and 5℃/min) without and with applying a magnetic field (12 T) in the Fe-1.1%C alloy were investigated. The results showed that the area percentage of abnormal microstructure in the specimen heat treated under magnetic field decreases with the cooling rate increasing. The reason is that the diffusion is limited with the cooling rate increasing. At the same cooling rate, the area percentage of abnormal microstructure in the specimen heat treated with magnetic field is more than that in the specimen heat treated without magnetic field and the hardness of the specimen heat treated with magnetic field is lower.
2013 Vol. 48 (4): 55-58 [
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59
LIU Zhen-tian，ZHOU Jian,MA Dang-shen,QIU Li-peng,LIU Bao-shi
Effect of Smelting Process on Microstructure and Mechanical Property of H13 Steel
Effect of such two different smelting process as “Vacuum Induction Furnace (VIF)+ Electroslag Remelting (ESR), Electric Furnace(EF)+LF+VD” of special steel on microstructure and mechanical property of H13 molds was studied. The results show that the process of VIF+ESR has some effects on increasing of the cleanliness, decrease of S, P and segregation in H13, which can enhance the transversal impact toughness to some extent in the core of H13 steel. The increase of impact toughness is restricted by a large number of primary carbides in microstructure of H13 steel.
2013 Vol. 48 (4): 59-63 [
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64
JIA Shu-jun,GAO Hong-gang,LIU Ming-hui,LIU Qing-you
Composition Optimization of Cold-Rolled TRIP590 Steel
The effects of chemical composition and critical annealing temperature on the microstructure and mechanical properties of TRIP590 steel were investigated by utilizing thermal simulation. The results show that the average grain size and the volume fraction of ferrite both decrease as the annealing temperature increases, while the volume fraction of retained austenite and C concentration in austenite firstly decrease and then increase. At the same annealing temperature, the volume fraction and the average grain size of ferrite both decrease with increasing Nb content. There is maximum volume fraction of retained austenite in the highest Nb and Si content steel, while minimum in Nb-free steel. Industrial trial results show that the microstructure type of the strip is ferrite, bainite and retained austenite, at the same time, the mechanical properties can meet the performance requirements.
2013 Vol. 48 (4): 64-69 [
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ZHAO Yi-han,,ZHAO Cheng-zhi,WANG Jian-nan,JIANG Chen-yu,YUAN Yu-ping
Forming Mechanism of δ-Ferrite and Its Effect on Martensite Heat-Resistant Steel Impact Energy
The effect of chemical compositions and heat treatment normalizing temperature on δ-ferrite content was investigated to analyze the forming mechanism of δ-ferrite through thermo-calc thermodynamic equilibrium phase calculations and quantitative metallographic analysis, mechanical property test, SEM analysis. The effect of content and position distribution of δ-ferrite on impact energy was also analyzed. The results show that chemical compositions and normalizing temperature have obvious effect on δ-ferrite content. δ-ferrite content will decrease with increase in C and N content. The δ-ferrite mainly concentrates in the prior austenite grain boundary, which can decrease impact energy. There are the large aggregations of rich Nb cabide, which can decrease MX phase content.
2013 Vol. 48 (4): 70-75 [
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Environmental Protection and Energy
76
JI Le-le,HE Dong-feng,XU An-jun,WANG Hong-bing,GE Xin-feng
Numerical Simulation on Preheating System of Regenerative Ladle
In order to research the application effect of high temperature air combustion technology in ladle baking process and optimize ladle baking system, numerical simulation and optimization research of gas flow, combustion and heat transfer in ladle during the baking process was carried out, using commercial software fluent, with finite difference and SIMPLE methods. The influence of preheated air temperature was quantitatively analyzed. Results show that raising the preheated air temperature and making technical renovation of the ladle baker are effective measures to obtain the better baking temperature of the ladle and save the energy, which will be of great importance to guide the practical production. The simulation results are basically consistent with the measured.
2013 Vol. 48 (4): 76-81 [
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Technology Exchange
82
WANG Li-feng,ZHOU Yu-li,ZHANG Wei,ZHOU De,DENG Su-huai,DI Quan-kang
Development of Long Steel Products for High-Speed Railway Track Plate
The long steel product for high-speed railway track plate including steel grades and key technologies etc was introduced. Through reasonable optimization of Mn, Cr, B and Ti, the chemical composition of wire rod for CRTS1 plate was originally designed. The steel cleanliness such as total oxygen content at 7×10-6-12×10-6 can be improved without using ferrosilicon powder in refining process and increase the slag alkalinity. In order to solve the problem of decarburization sensitivity in median carbon and high silicon steel，the decarburized layer control technology including heating furnace temperature, heating time, atmosphere and cooling process after controlled rolling was developed. The decarburized depth can be controlled into a thickness less than 1% of steel diamater. The high strength on the basis of high plasticity was realized through using organization strengthening and precipitation strengthening, and simultaneously obtaining fine ferrite and pearlite in core of steel bar to ensure material plasticity.
2013 Vol. 48 (4): 82-87 [
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