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2014 Vol. 49 No. 1
Published: 2014-01-15
Materials
Environmental Protection and Energy
Raw Materials and Ironmaking
22
GE Jun-li,BAI Ming-hua,PIAO Ying-min,WANG Jian，FU Yuan-xiang,XU Kuan
Influencing Factors of DRI Shaft Furnace Flow Field Based on Genetic Algorithm
The gas distribution in direct reduction iron (DRI) shaft furnace has an important influence on DRI production process. Using the fluid analysis software ANSYS, the distribution of reducing gas flow and relative influencing factors in DRI shaft furnace were investigated. In the simulation analysis, pellets were simplified as porous media. The viscous resistance coefficient and inertial resistance coefficient measured in the experiment were used as the basic input parameters of the simulation process. The calculation results by the neural network to find the mapping relationship between the reduction part average pressure, transition part average velocity and the gas-based direct reduction shaft furnace process parameters. Finally, the shaft furnace ideal air distribution influencing factors are obtained through the calculation results by genetic algorithm optimization. The results show that the airflow distribution in the furnace has a direct relationship with the state of the factors which include the furnace top pressure and cooling gas outlet pressure. They impact the reasonability of the flow field in the shaft furnace.
2014 Vol. 49 (1): 22-27 [
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XU Mian-guang,LIU He-ping,XIANG Li,QIU Sheng-tao
Numerical Simulation of Transient Fluid Flow During Casting Start Period in the CSP Funnel-Type Mold With Electromagnetic Brake
A three-dimensional mathematical model was established to investigate the transient flow phenomena of molten steel during the casting start period with electromagnetic brake (EMBr). An algorithm of VOF has been employed to simulate the air/steel interface. Use dynamic mesh to control the movement of dummy bar. The results show that, the electromagnetic field can significantly restrain the turbulent flow of molten steel and the fluctuation of the surface at the time of the dummy bar moving; the EMBr can optimize the flow pattern in the mold; the stabilization of the free surface may come earlier by 10 seconds with EMBr; the EMBr provides a positive effect to reduce the flow deviation of molten steel in the funnel-type mould.
2014 Vol. 49 (1): 28-33 [
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34
YANG Guang-wei，CHU Ren-sheng，WANG Xin-hua，HUANG Fu-xiang，WANG Wan-jun，YIN Yu-qun
Removal Behavior of Inclusion During RH Vacuum Treatment of X70 Pipeline Steel
Inclusion morphology, composition, number and size at various times of the RH vacuum treatment were investigated on X70 pipeline steel with ASPEX. Results suggest that: The inclusions are mainly liquid globular CaO-Al2O3 with a small amount of MgO throughout RH vacuum treatment. Inclusion number decreases with time and decreases by 70% after 28min RH vacuum treatment. Inclusion number after RH treatment can be dramatically reduced by reducing inclusions before RH treatment. The total inclusions and inclusions with size 1-5μm is monotonously decreased in number, while inclusions over 5μm firstly increase then decrease after reaching the maximum. It takes more time for bigger inclusions to reach the maximum. The average diameter of inclusions increases from 2.2-2.5μm before RH to 3.0-3.9μm after RH.
2014 Vol. 49 (1): 34-38 [
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39
YANG Wen-yuan,HOU Chun,CUI Huai-zhou,GAO Wei-tao,WANG Ming-lin
Water Model Test on Duplex Process for Steel Making
The basic parameters of bath flow were simulated by water model under different blowing conditions of oxygen lance nozzle and conditions of duplex process. The results show that the effect of increasing blowing on shortening mixing time is not obvious when the strength of bottom blowing gas of dephosphorization reached 0.30m3/（t·min）. The mixing time is extended 63% when there is 10% scrap. Decarburization with high strength oxygen supply(5m3/（t·min）), the splashing ratio can be greatly improved than with normal strength oxygen supply. The splashing ratio is reduced when the holes arranged interlaced nozzle was adopted and the ratio of converter capacity was increased.
2014 Vol. 49 (1): 39-44 [
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LI Jian-quan ,CHEN Deng-fu, WU Guo-rong, LEI Yang-wei
Secondary Cooling System for 37Mn2 Steel With Round Continuous Caster
Base on the high temperature mechanics performance and metallurgical criterion, heat transfer mathematical model was proposed, and the round billet temperature and thickness of solidified shell were calculated with the model. According to the calculation results, the model was optimized. And on this basis, the reasonable secondary cooling system was proposed. The secondary cooling system for 37Mn2 steel with round continuous caster was studied, and the secondary cooling system which was matched with the continuous casting process and equipments was established and it was applied in industrial production. The results show that there is no difference between the measurement and calculated results in round billet temperature. The surface temperature in straightening zone is above 950℃. The internal quality of round billet is perfect and the level of central crack and porosity is 0, and the level of shrinkage, center porosity and center segregation is below 1.5. The quality of round billet can meet the needs of subsequent production.
2014 Vol. 49 (1): 45-51 [
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52
YANG Li-po,YU Bing-qiang,LI Rong-min,,DU Chang-zheng
Effect of Strip Edge Offset on Original Shape Signal of Cold Rolling Strip
In the shape detection process of the cold rolling strip, the strip edges on both sides often couldnt completely just cover a complete shape detection channel, so the edge shape error compensation model was established for this phenomenon. Using the model, channel coverage of the edge portion can be calculated according to the lateral shift amount of the strip automatically. Combined with two methods of the proportional compensation and the slope compensation, the shape signal error can be compensated based on its reasonable edge portion of the cold rolling strip. Physical testing and industrial datum show the method is reliable and effective.
2014 Vol. 49 (1): 52-56 [
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CHEN Liang,ZHANG Chao,ZHU Shuai,KANG Yong-lin
Rolling Process and Microstructure and Properties of Thin Gauge Ultra-High Strength Strip Manufactured by CSP Line
The process and technology characteristics of CSP line were introduced. Through optimizing continuous casting and slab quality controlling, using 1180 ℃ tapping temperature and 850-920 ℃ finishing rolling temperature, the mechanical properties of thin gauge ultra-high strength strip were analyzed based on different cooling modes and coiling temperatures. The production results show that the head continuous cooling mode is helpful to grain refinement, higher coiling temperature is beneficial to the sufficient dispersed precipitate fine TiC particles, 70% of the TiC particle size is below 20nm causing significant precipitation strengthening. The machnanical properties of thin gauge strength were affected both by fine grain strengthening caused by and cooling rate and thinner gauge and precipitation strengthening caused by coiling temperature. By optimizing cooling mode and coiling temperature, 500, 600 and 700MPa strength grade strips with 1.2-6.0mm thickness were developed successfully.
2014 Vol. 49 (1): 57-61 [
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Optimization of 580mm Hot Strip MillGUO Wei,WANG Feng-qin,SUN Meng,ZHU Qi-jian,LI Bin,LI Jin-bao
Research and Application on Thinner Strip Crown
Aiming at the problems of the low crown controlling precision of thinner strip on 1580mm hot strip mill, the obvious problems of the target profile reset were found through the analysis of lots of production data and through the research of the shape model of L2 on the 1580 mm hot strip mill, which affected the crown precision. By contrasting and analyzing lots of the shape data, the reasons for these problems were that the model calculation has the miscarriage of justice for the crown adjustable capabilities of the first three mills for the irrationality of some parameters, such as the flatness factors and thermal expansion factors. The optimized plans such as the optimization of the flatness dead band factor and the thermal expansion parameters for the improvement of the thin strip crown control precision were implemented on this hot strip mill. These optimized plans could resolve the problem of the target crown reset of this line, and the strip crown control precision was increased.
2014 Vol. 49 (1): 62-65 [
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Materials
66
SUN Yong-qing,LIANG Jian-xiong,SUN Guo-qiang, YANG Zhi-yong,LI Wen-hui,ZHANG Li-na
Effect of Composition and Heat Treatment on Microstructure and Mechanical and Magnetic Property of 403 Steel for Rotator
Hot!
Three 403 steel bars of different compositions were searched, which were produced by 200kg VIM furnace and forged into 120mm. Mechanical and magnetic properties were tested after heat treatment 950-1000℃×1h OC+720-750℃×3h OC. The results show that, 403 steel bar with higher Ni or N has higher strength, magnetoconductivity and toughness especially. Compared with test steel bar with higer Ni, bar with higher N has higher magnetic induction in lower magnetic field intensity, while lower magnetic induction in higher magnetic field intensity. Strengthening mechanism was searched and the conclusion can be made to guide the production of this type steel for rotator.
2014 Vol. 49 (1): 66-69 [
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CHEN Xiang-wei，WEI Jiao，CHEN Jun，TANG Shuai，WANG Guo-dong
Effect of Coiling Temperatures on Microstructure and Mechanical Properties of DQ&P Steel
After hot rolling, the tested steel was firstly cooled to different temperatures ranging from Ms temperature to Mf temperature using ultra fast cooling system, and then cooled room temperature using furnace cooling. The influence of coiling temperature on microstructure and mechanical properties of DQ&P steel was investigated. The results show that the volume fraction of ferrite is slightly increased and the volume fraction of retained austenite is increased from 5.9% to 12.1% as the coiling temperature is increased from 200℃ to 360℃. The volume fraction of retained austenite for the coiling temperature of 200℃ remains unchanged after tensile deformation, however, the volume fraction of retained austenite for the coiling temperature of 360℃ is lowered to 8.5% after tensile deformation. The better mechanical properties with the elongation of 23.9%, product of strength and elongation of 20GPa·% and lower yield ratio of 0.79 can be gained at the coiling temperature of 360℃.
2014 Vol. 49 (1): 70-73 [
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74
L Jia-shun，LI Feng，YANG Hong-gang，ZHOU Fang
Research on Coating Microstructure of Continuous Hot Dip Aluminizing Coated Steel Sheet
Hot dip aluminizing steel sheet exhibits excellent heat resistance, corrosion-resisting property and oxidation resistance. The coating microstructure and property of continuous hot dip aluminizing coated steel sheet was investigated. Aluminized steel sheet was prepared in laboratory by hot dip simulator. By SEM, the surface and cross section microstructure Al-Si coating was analyzed. The distribution of elements in coating includes Fe, Al and Si was observed by EPMA (electron probe micro analyzer). The anti-corrosion capability of Al-Si coating was studied by salt spray test. Coating phase was inspected by X-ray diffraction. It was proved that the Al-Si coating has finer microstructure, and have even more excellent corrosion resistance. The Al-Si coating is made up of aluminum-rich dendrite, interdendritic aluminium-silicon alloy phase, intermetallic layer and lump phase.
2014 Vol. 49 (1): 74-78 [
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79
LIU Shuang，TANG Guang-bo，LI Ji-guang，SUN Hao-yuan，LI Bin,
Microstructure and Mechanical Property of 1800MPa Grade Low Alloyed Ultra-High Strength Steel for Engineering Machinery
A novel 1800MPa grade low alloyed ultra-high strength steel for engineering machinery was designed and its hot rolling was simulated on a pilot hot rolling mill. Effect of different processes, such as process 1 (deformation of 80% + direct-quenching + tempering at 250℃), process 2 (deformation of 90% + laminar cooling to 650℃/1 h + air-cooled + tempering at 250℃) and process 3 (deformation of 90% + air-cooled to 650℃/1 h + air-cooled + tempering at 250℃), on the microstructure and mechanical properties were investigated. The results indicate that the sample of process 1 has a maximum tensile strength of 1816MPa and yield strength of 1473MPa with elongation of 13 percent and reduction of area of 45 percent, the impact energy of room temperature and -40℃(KV2) is 28J and 21J respectively, and the hardness value is 50HRC. It might be from the comprehensive effect of strengthening mechanisms due to the lath martensite+retained austenite, composite micro-alloy carbide and ε-carbide precipitation. Multi-phase microstructure involving lath martensite+upper bainite+retained austenite, lath martensite+acicular ferrite+lamellar pearlite+retained austenite can be obtained by the processes 2 and 3 respectively, and the mechanical properties dramatic decline. The second phase precipitation composite particles are precipitated with Nb,V,Ti.
2014 Vol. 49 (1): 79-84 [
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Environmental Protection and Energy
85
SI Xin-guo,ZHAO Er-min
Experiment on H2-CO Reduction of Titanium Concentrate by Thermogravimetry
It was studied that H2-CO reductive characteristics of titanium concentrate by thermogravimetry. After analysis of TG, phase and micro-topography, the results show that it is similar that TG curve of reduction of titanium concentrate on the basis of hydrogen with adding carbon monoxide. Firstly weight percents decrease with prolonging of time, then keep balanced for some time, finally increase gradually; weight loss ratio increases with adding of hydrogen content in the process of minishing the weight percent; if weight percentage keeps augmentative, rate of live weight growth enhances and maximizes on the condition of 80% carbon monoxide, then decreases gradually with lowing carbon monoxide content; reasonable temperature should be 1150℃ in order to ensure that there is not FexC phase and iron metal phase at a minimum platform; it holds strong diffusivity because hydrogen atomic radius is less; they accelerate the formation of porosity and strengthen vapor transport and reducing capacity in the beginning; reductive reaction happens between FexC and others with gas producing, which make oxidation product cataclastic and specific surface area becomes bigger.
2014 Vol. 49 (1): 85-89 [
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