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2012 Vol. 47 No. 10
Published: 2012-10-15
Technical Reviews
Steelmaking
Metal Forming
Materials
Environmental Protection and Energy
Technical Reviews
1
XU Kuang-di1,XIAO Li-jun2
Deoxidation and Inclusion Control in Special Steel Refining
Special steel is a general designation of certain types of steel with higher cleanness upgraded gradually by steel factories with promotion of process and equipment step by step according to the customer demands on product quality. The total oxygen content in steel is extremely important for its cleanness, the requirements of total oxygen for different steel is different. In the deoxidation refining process, the reactions will take place among the deoxidation elements, dissolved oxygen in the steel, molten steel, slag, inclusions, and refractory and evolve into balance. These reactions have an important impact on the quantity, composition and morphology of inclusions in the steel. So we make comparison of the deoxidation ability with different deoxidation elements by thermodynamic calculation. The deoxidation mechanism and the control of inclusions during the refining process of typical steels (bearing steel, spring steel, cord steel, electrical steel, free cutting steel etc.) were also introduced. The mechanism of interaction among different deoxidation elements, molten steel, slag and refractory was analyzed and discussed.
2012 Vol. 47 (10): 1-13 [
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Raw Materials and Ironmaking
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XIANG Zhong-yong1,OUYANG Biao1,WANG Xiao-liu2
Profile Reasonability of Thin-Walled Blast Furnace
Recent years, the thin-walled blast furnace has undergone considerable development because of its great advantage in maintaining stable operations of blast furnace during single a campaign life. Therefore, a reasonable profile would be one of decisive factors in the design of thin-walled blast furnace. Through discussing the process of rationalization of thick-walled blast furnace, and then based on the empirical analyses on production data of some thin-walled blast furnace, the relationship among various parameters on thin-walled profile were investigated. As a result, some feasible design methods of thin-walled blast furnace with their relevant profile parameters will be proposed.
2012 Vol. 47 (10): 14-19 [
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LI Qiang1,FENG Ming-xia2,ZOU Zong-shu1
Discrete Element Model for Charging Process of COREX 3000 Shaft
The gas distribution in a shaft furnace dominates the temperature profile, gas utilization ratio, metallization degree and is the only means for regulating the gas flow distribution. Through introducing kinematic theory of granular, a numerical simulation model of burden distribution in the shaft furnace of COREX 3000 was developed by means of discrete element method (DEM) based on the Newton second law and soft-sphere contact model. The model can intuitively and visually reproduce the charging process, and quantitatively access the material flow trajectories, landing and forming process of the burden surface shape. Applying the model to further analyze the mixing charging process of two different diameter particle, obtained the charge movement process and the formation of the stockpile and found that size segregation is serious. Therefore, the model provides an important research base established model to find and optimize the charge patterns.
2012 Vol. 47 (10): 20-23 [
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QIAN Hui1,ZHOU Yu-shen2,YANG Jun-he3,ZHANG Zuo4
Experimental Investigation of Cellulose Used as COREX Coal Briquette Binder
With methyl cellulose (MC) or hydroxypropyl methylcellulose (HPMC) as binder, a series of tests were conducted to investigate the properties of coal briquette, such as shatter strength, mechanical strength of char, CO2 reactivity of char and the strength of char after reaction. Comparing with lump coal, coal briquette can form larger char after pyrolysis. But the char strength after reaction from briquette is not as good as from lump coal. Adding primary coking coal can improve coal briquette high-temperature properties obviously so that it can reach the level of lump coal in all aspects, or even better than lump coal. The results of tests demonstrate that coal briquette with MC or HPMC as binder can be used as COREX fuel. And then, a new technical solution to improve COREX fuel conditions and broaden the available resources for COREX process is provided.
2012 Vol. 47 (10): 24-26 [
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Steelmaking
27
WANG Ming-lin1,YANG Chun-zheng2,TAO Hong-biao1,ZHANG Hui1,LIU Jian-hua2,WU Ye-ming1
Formation Mechanism of Transverse Corner Crack on Micro-Alloyed Steel Slab
In order to research the formation mechanism of transverse corner crack on micro-alloyed steel slab, the precipitation behaviors of the second phase particles during the continuous casting process were investigated, and the industrial trial of stagnant slab were carried out. The calculation results show that the beginning precipitation temperature of titanium carbonitride, niobium carbonitride, aluminum nitride in X65 pipeline steel are 1508, 1123, 1165℃ respectively. And the precipitation peak temperatures are 1360, 870, 840℃. Results of stagnant slab test show that no crack appeared in mold and vertical segments. But at 3270mm away from the meniscus, that is 710mm after bending, transverse crack begins to appear at outer arc surface. No crack in inner arc surface appears. The slab corner temperature at bending part is in the steel brittle temperature zone and under the tensile stress at the same time, which is the main cause for the appearance of transverse corner crack at outer arc surface.
2012 Vol. 47 (10): 27-33 [
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BAI Rui-guo1,2,L Ming1,ZHU Rong1,BAO Xiang1,ZHANG Xing-li1,2,GAO Hai1,2
Water Simulation on Vanadium Extraction by Powder Injection in 150 t Converter
Through water simulation experiment, gas and powder mixture were thought as a larger density of gas phase flow in powder injection vanadium extraction process. The electrical conductivity were measured to compare mixing time of different powder injection flow and position experiments for studying stirring effect and impacting characteristics of injecting powder in the 150t vanadium extraction converter. It is found that it is easy to block the injection nozzle by bottom injecting powder. When the nozzle is in the side part of 30 degrees and 300mm lower than pool surface, the mixing time is only 54.5 seconds. So the position which is symmetric with side blowing place in 30 degrees about axis A should be the best powder injection position. It is beneficial to strengthen stirring ability of vanadium extraction molten pool and promote vanadium extraction reaction, which will provide the theoretical support for the realization of high efficiency vanadium extraction by powder injection in converter.
2012 Vol. 47 (10): 34-39 [
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CHEN Hong1,L Yong-kang2,ZHANG Ji-bin2,YANG Jin-wen2
Optimization Practice of Steel Ladle Running Cycle
The stationary period of ladle in all processes was detailedly investigated using the running cycle method, the law of temperature drop was researched and the problems of ladle running were found. The results show that the cycle period and reasonable number of ladle can be calculated through the time statistic; there are some unnecessary running ladles; for empty ladle, the running time is longer and online baking time is shorter. Through optimizing the ladle running cycle, not only ladle running cycle is shorten so that the reasonable number of running ladle is ensured, but also the running cycle for empty ladle is speeded up and the running time for ladle is shorten about 10 minutes. Hot ladle turn round can basically be achieved. Control strategy optimization for ladle running is helpful to energy-saving, decrease in ladle number, stabilization and reduction of casting temperature, promotion of continuous casting and improvement of slab quality.
2012 Vol. 47 (10): 40-44 [
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CHENG Zi-jian 1,2,GUO Jing1,CHENG Shu-sen1
Slag-Steel Equilibrium and Optimization of Refining Slag Composition in LF for SPCC During CSP Process in JISCO
The reasonable content of MgO in refining slag calculated by the thermodynamic calculation software FactSage ranges from 4% to 8%, in which 6% is the best. In addition, slag-steel equilibrium at 1873K between SiO2-CaO-Al2O3-6%MgO quasi-ternary slag and liquid steel were analyzed on the basis of results of industrial sampling combined that calculated by FactSage both in liquid region and solid-liquid coexisting region with CaO saturation. It indicates that the refining slag with high basicity and high w(CaO)/w(Al2O3) (C/A) is favorable for control of low oxygen, low sulfur and low silicon. However, slag with too much CaO is disadvantageous of deoxidation and desiliconization that suggests refining slag is not the whiter the better as the supersaturated CaO do not take part in the slag-steel reaction and even worsen its kinetic conditions. Furthermore, the optimized compositions of refining slag in LF for SPCC in Jiuquan Iron and Steel Corporation (JISCO) are: CaO 50%-55%, Al2O3 30%-36%, SiO2 1%-6%, MgO 4%-8% and 6% is best, basicity 9.0-14.0 and w(CaO)/w(Al2O3) is 1.5-1.8. Finally, both slag-steel equilibrium experiments in laboratory scale and industrial trials in plant scale verified that optimized slag has a better ability for deoxidation, desulfurization and control of silicon content, and could better control inclusion composition as well as its removal.
2012 Vol. 47 (10): 45-51 [
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Metal Forming
52
YIN Yuan-de1,2,LI Sheng-zhi2,KANG Yong-lin1,WANG Peng-zhan3,WANG Xiang-dong3,LI Guo-tao3
Tendency of Lamination Defect of Thick-Walled P92 Pipe With Large Diameter Elongated by 2-Roll Rotary Rolling Process
To investigate the influence of different technological parameters such as roll rotational speed, feed angle and roll entrance cone angle on tendency of lamination defect of seamless P92 steel pipe thick-walled with large diameter elongated by 2-Roll rotary rolling process, with the aid of commercial FE code MSC.SuperForm, 3D thermo-mechanical simulations were presented. The damage field of the rolling piece during the elongating process, and the tendency of lamination defect of steel pipes were analyzed using Oyane ductile fracture criterion. It is found from the simulation that a high dangerous crack band exists in the internal surface layer of the rolling piece, adjacent to the contact zone with the plug. Furthermore the influence of roll rotational speed, feed angle and roll entrance cone angle on the damage filed were investigated. The result shows that the maximum characteristic value of ductile fracture of rolling piece decreases with the decrease of roll rotational speed, the increase of feed angle and roll entrance cone angle, and the tendency of lamination defect reduces. The scientific basis can be provided for revealing formation mechanisms of lamination defects of rolled seamless steel tubes with high Cr, determining the sensitive working conditions caused defects, and making the effective measures to prevent or reduce lamination defects.
2012 Vol. 47 (10): 52-56 [
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YUAN Peng-ju1,2,WU Di1,FU Chang-wei2,ZHAO Xian-ming1,HUO Xi-wei2
Effect of Ultra-Fast Cooling on Steel Strength
The ultra-fast cooling mechanism of rolled stock was investigated. The experiment was carried out on H-beam by using ultra-fast cooling device of Northeastern University. The effects of different cooling rates and cooling methods on structure and properties of Q235B and Q345B rolled stocks after rolling were analyzed. The results show that the strength is improved by 205MPa at 444.4℃/s of cooling rate by using single-stage cooling. The strength is improved by 230MPa by using two-stage cooling, when the cooling rate reaches to 385 and 297℃/s. Two types of cooling methods can both dramatically improve the strength of rolled stocks. Where as the cooling effect of two-stage cooling is apparently higher than single-stage cooling. It will provide technical supports for realizing low cost industrial production of H-beam and production of higher level steel.
2012 Vol. 47 (10): 57-60 [
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LIU Guo-liang1,NI You-jin2,JI Chen-xi1,CUI Yang1,CHEN Jin2,BAO Chun-lin1
Reason and Control on Edge Cracks of J55 Hot Rolled Strip
The edge crack was investigated through optical microscope and SEM, and the reasons of edge crack were analyzed. Results show that transversal corner cracks of slabs are the origin of the edge cracks of hot rolled strips, and AlN, Nb(N, C) precipitates around the prior austenite grain boundaries due to intensive cooling rate rendered the slabs more susceptible to cracks. After rolling stands, the transverse cracks of the slabs will propagate to serrated edge cracks．
2012 Vol. 47 (10): 61-65 [
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Materials
66
ZHANG Jing-wu1，2,NIU Jian-ping1,LIU Wen-chang1，2,YUAN Hui1，2,CHEN Yun-bo3,LI Yong-bing3
Study on Hydrogen-Induce Ductility Loss in YB70 Steel
Hydrogen-induce ductility loss in YB70 steel was investigated by measurements of tensile properties as well as TEM and SEM analyses of deformation and fracture. The result shows that the hydrogen-induce ductility loss in YB70 steel exceeds 80% when tensile specimens were hydrogen-charged for more than 2h. Some transgranular cracking along slip planes can be observed on the tensile fracture surface of specimens hydrogen-charged. Hydrogen segregation near the interface between the matrix and carbide precipitates promotes the dislocation movement in tensile deformation, leading to a high density of tangled dislocations to be located at approximately 15nm from the interface. The cracking is formed at the position with the high density of tangled dislocations and propagated along slip planes, which results in the ductility loss of YB70 steel.
2012 Vol. 47 (10): 66-69 [
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ZHOU Cui-lan1,LIU Hong-mei2,BAI Jin-gang3,NIE Zhi-shui1,ZHOU He-feng1,QIAO Jun-wei1
Effects of the Cold-Rolled Reduction on the Mechanical Properties of 304 Austenitic Stainless Steel Sheets
To provide a guidance to the industrial production of the austenitic stainless steel sheets, the changing of the cold rolled hardness with the cold rolling reduction of the 304 austenitic stainless steel sheets was investigated. The effect of different thickness reductions by cold rolling on the microstructure and mechanical properties of 304 stainless steels were investigated. The annealed stainless steel sheets were subjected to the cold rolling at room temperature from 10% to 52% thickness reduction. The results indicate that strain-induced martensite transformation clearly results in a significant strengthening of the steel. The hardness and strength of the 304 austenitic stainless steels are improved distinctly. After 40% cold rolling, the Vickers hardness is 2.2 times higher than that of the primary one, the yielding strength and tensile strength are greatly increased to about 880MPa and 1312MPa, respectively, which are nearly 4.2 times and 1.8 times higher than those of the primary one.
2012 Vol. 47 (10): 70-75 [
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WU Hong-yan,DU Lin-xiu,LIU Xiang-hua
Microstructure, Mechanical Property and Corrosion Behavior of 09CuPTi Series Weathering Steel
09CuPTi-Nb weathering steel was produced by a two-stage rolling in a hot strip rolling production line. The influence of rolling process parameters on microstructure and mechanical properties were investigated. It shows that microstructure of three test steel is mainly acicular ferrite and bainite. When a final cooling temperature is 530℃ and cooling rate is 25℃/s, microstructure is composed of fine and homogeneous lath bainite. Yield strength and tensile strength is 617MPa and 702MPa, respectively, and ductile-brittle transition temperature is lower. At this condition the tested steel has high strength and toughness. The corrosion evolution of B sample of 09CuPTi-Nb weathering steel and reference steels in a simulated industrial atmosphere environment was studied. It shows that the corrosion rate increases with increasing the wet / dry cycles in the initial stage of the test, however it decreases in the latter stage of the test. Corrosion rate of 09CuPTi-Nb weathering steel is near to SPA-H steel and lower than that of Q345 steel. Rust layer of 09CuPTi-Nb weathering steel is divided into outer and inner layers, and inner rust layer is dense and mainly composed of α-FeOOH and a little of γ-Fe2O3 composition. Rust layer of Q345 steel is composed of α-FeOOH, γ-Fe2O3 and Fe3O4 composition. The electrochemistry test indicates that the corrosion product can promote the cathodic process and restrain the anodic process.
2012 Vol. 47 (10): 76-82 [
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KUANG Shuang,QI Xiu-mei,WEI Dong,LIU Guang-ming
Microstructure Characteristics of Dual Phase Steel With Different Martensite Volume Fraction
The microstructure characteristics of dual phase steels with different martensite volume fraction (MVF) were investigated by optical microscope. The results observed show that martensite shape is island or granular in the case of low MVF. With the increase of MVF, the optical visible lath martensite appears in the microstructure, but the granular martensite islands decrease. When further increasing the MVF, the lath martensite becomes the dominant phase, whereas the granular martensite islands have almost disappeared. Combined with thermodynamic analysis, the reduction of C and Mn contents in martensite due to the increase of MVF is one of the possible reasons for the changing of martensite morphology.
2012 Vol. 47 (10): 83-86 [
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Environmental Protection and Energy
87
DING Yi1,CHEN Guang2,LI Li3,SHI De-ming1,CHEN De-min2,LIU Xian-hui 3
Discussion on Construction of Model and System on Energy Flow in the Steel Plant
Through the analysis of the mass flow and energy flow, the energy flow and mass flow information system was constructed with the information and control technology; and the multi-class, multi-level, multi-view model system was set up for realizing the coupling of energy flow and mass flow, adjusting on line and the orderly optimization of processes. It mainly includes the building of hardware platform for the energy center, the development of energy management software, the construction of kinds of models, including the coupling sub-models of energy flow and mass flow in each individual process, the relationship models between individual processes or different systems, and the mathematical model for the energy consumption optimization. However, with the optimization regrouping and collaborative integration by the ‘energy flow network’ and ‘mass flow network’, the energy lean management and controlling system and decision-making support system were constructed. It can improve the energy efficiency and resource utilization.
2012 Vol. 47 (10): 87-91 [
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WEI Dai-xiu1,XU An-jun1,HE Dong-feng1,TIAN Nai-yuan1,YANG Quan2
Beneficial Reuse of EAF Slag and Its Leaching Behavior of Cr
The structure and properties of EAF slag and it’s leaching behavior of Cr were studied. The results indicate that the main minerals in the EAF slag are Ca2SiO4, Ca3Mg(SiO4)2 and MgCr2O4. The content of Cr2O3 in EAF slag is 2.92%.The slag are suitable for beneficial reuse, but metals in EAF slag are distributed evenly among every particle size. The leaching tests of Cr in slag show that the ratio of Cr leaching rate from slag in deionized water was inversely-proportional to particle size, and directly proportional to leaching time and liquid to solid ratio. Electromagnetic stirring improve the kinetic condition and improve Cr leaching rate. In deionized water, the percentage of Cr(Ⅵ) is higher than 50% in all the Cr leached from EAF slag. In acid solution, the volume of Cr leaching from slag increases but all the Cr are in the form of Cr（Ⅲ）.
2012 Vol. 47 (10): 92-96 [
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