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2013 Vol. 48 No. 5
Published: 2013-05-15
Steelmaking
Metal Forming
Materials
Technology Exchange
Raw Materials and Ironmaking
11
WU Sheng-li，TUO Bi-yang，ZHANG Li-hua，WU Jian-long，SUN Ying,
Softening-Melting Dropping Behavior of Pre-Reduction Iron-Bearing Burden in Blast Furnace
Softening-melting dropping characteristics of pre-reduction burden with the different degree of metallization, contained certain carbon were investigated. The results show that although the softening temperature interval of the pre-reduction burden is larger than that of the original burden; however charge column pressure drop is less. In the melting and dropping temperature interval, the melting start temperature increases with increasing metallization rate of burden, the dropping temperature reduces with increasing carbon content in molten iron, the maximum pressure drop of the charge column decreases with increasing metallization rate. SD decreases with increasing metallization rate or increasing carbon content. It is speculated that pre-reduction burden included a certain degree carbon content is benefit to increase spaces of soften layer, decrease the thickness of melting layer, and thus improve the permeability of cohesive zone.
2013 Vol. 48 (5): 11-16 [
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17
XIE Hong-en,FU Wei-guo,RAO Jia-ting,WEN Yong-cai
Evaluation Strategy of Intensifying Degree of Blast Furnace
According to the contrast of blast furnaces of Pangang and some others, intensifying degree index was put forward for the judgment of intensifying degree of blast furnace, which included iron-slag index and bosh gas index, eliminated the disadvantage of conventional smelting intensity and bosh gas index, and reflected the essence of blast furnace smelting more clearly. Intensifying degree indexes of different blast furnaces were contrasted. The results showed that slag volume have great influence on the intensifying degree and is the important factor causing the high intensifying degree, the intensifying degree could be enhanced by increasing oxygen enrichment without increasing the volume of blast, high pressure operation is efficient measure for alleviating the contradiction between descending charge and ascending gas and increasing the top pressure is an important measure for enhancing intensifying degree of the blast furnace of Pangang.
2013 Vol. 48 (5): 17-20 [
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Steelmaking
21
HAN Wei-gang,LI Xiu-ping,SHI Yi-xin,WANG Wei-dong,ZHANG Chun-xia
Online Ladle Quantity of “One-Open-Ladle-From-BF-to-BOF” Route by Using Queuing Theory
The operational process of ladles in “one-open-ladle-from-BF-to-BOF” route was analyzed by using queuing theory, and a mathematical model of ladles’ queuing systems was established. The model was verified by Shagang practical production, and it can be a support to ladle operation management and steel plants design.
2013 Vol. 48 (5): 21-24 [
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25
LIN Teng-chang,ZHU Rong,LU Zhi-fang,FANG Yu-rong,WANG Cheng-jie
Optimization of Slag System in Decarburization Converter of Duplex Process With Low Silicon Semi-Steel Smelting
In order to decrease stick lance and reduce the end phosphorus content, the slag system of 120t duplex process decarburization converter was studied by using chemical analysis, melting experiment and Factsage thermodynamic numerical simulation. The effect of slag system on smooth smelting was expounded, and a basic principle and final slag composition of new slag system was established. After the industrial application of new slag system, the phenomenon of stick lance remits to a certain extent. The slag ratio can reduce to 34.7kg/t of decarburization converter, and the end phosphorus content is about 0.006%-0.012%.
2013 Vol. 48 (5): 25-28 [
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29
YANG Chuan-hao，LIU Zhong-li，WANG Gui-quan，LU Zheng-ping
Mathematical Model and Simulation of Electroslag Remelting Process for Large Ingot
Based on heat transfer theory, an electroslag remelting (ESR) process mathematical model for 80t level three phase furnace was established, and was checked by producing 75t 316LN austenitic stainless steel ingot. The large ESR ingot temperature field distribution and the changes of second dendrites space distance were investigated. The results shows that the temperature of slag pool center is 1800℃, center temperature gradually reduces from top to bottom along the direction of heat transfer, and the depth of metal molten pool is 1500mm, which is about 0.8 times of ingot diameter, moreover, a 50mm cylindrical section exists above the metal pool, which can make slag skin thin and homogeneous. At last, the second dendrites space distance is increasing trend by ingot lateral edge to the center position, it coincides well with field production results.
2013 Vol. 48 (5): 29-34 [
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Metal Forming
46
YIN Yu-qun,YU Wei,JIANG Jin-xing,LIN Peng-fei
Yield Stress of High Grade Pipeline Steel at High Temperature and Its Effect on Hot Process
For the purpose of analysis the difference of process performance of high strength pipeline steel in hot rolling process, yield strength of X70, X80 and X100 at high temperature was measured by Gleeble 3500 simulator at 400-800℃. The results show that the high temperature yield strength is affected by temperature, the phase transformation characteristics difference caused by chemical composition, solution and precipitation strengthening. Yield strength and deformation resistance in finishing rolling and pre-leveling is not the limit in hot rolling process of high grade pipeline steels. Thickness of pipeline steel plate is an important factor for leveling force.
2013 Vol. 48 (5): 46-50 [
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51
QI Xiang-dong,DONG Zhi-kui,LIAN Jia-chuang,LOU Liang-liang
Applications of Strip Crown Closed-Loop Control for Hot Strip Mill
The strip crown is an important indicator of the quality for hot strip; the strip crown closed-loop control is an effective means to ensure the strip crown accuracy of hot strip. Under the condition of good flatness, through adjusting bending force as the primary means of the strip crown closed-loop control, the strategy of strip crown closed-loop control and the calculated method of bending force transfer coefficient on the strip crown were present. The model of strip crown closed-loop control was established. The strip crown closed-loop control system was used successfully on finish stands of Ningbo Steel 1780 hot strip mill. Through the actual assessment, the strip crown hit rate reaches above 96% and strip shape is good.
2013 Vol. 48 (5): 51-54 [
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Materials
55
PENG Xian,ZHU Ding-yi,HU Zhen-ming,LIU Hai-jun,LIU Long-long,WANG Ming-jie,
Effect of Carbon Content on Microstructure and Mechanical Properties of Fe-Mn-Cu-C TWIP Steels
The ingots of three grades TWIP steels with the different carbon contents, i.e. Fe-20Mn-3.0Cu-0.23C, Fe-20Mn-3.0Cu-0.83C and Fe-20Mn-3.0Cu-1.41C in mass percent (the 0.23C, 0.83C and 1.41C TWIP steel, respectively), were prepared by vacuum induction melting. The effect of carbon content on the microstructures and tensile properties of Fe-20Mn-3.0Cu-XC steels were investigated by X-ray diffraction, OM and TEM, and the deformation mechanism of steels was studied. The results show that the Fe-20Mn-3.0Cu-XC steels prior to and after deformation are fully composed of austenite without martensite. All of yield strength, tensile strength and the elongation at fracture are apparently increasing with carbon content. Fe-20Mn-3.0Cu-1.41C steel exhibits superior tensile properties. the yield strength and tensile strength are 501.62MPa and 1178.4MPa, respectively. The Fe-20Mn-3.0Cu-XC steels have excellent strain hardening ability, the maximal strain hardening exponent can reach up to 0782 with the carbon content increases to 1.41%. During the tensile deformation of Fe-20Mn-3.0Cu-XC steels, TWIP effect is the dominant deformation mechanism, and the increase of strength and plasticity is attributable to large quantity of dislocation pile-up, the generation of deformation twins and the interaction of each other.
2013 Vol. 48 (5): 55-61 [
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62
ZHOU Min,,ZHOU Qiang-guo,YAN Wei,WANG Wei,FAN Xin-min,SHAN Yi-yin
Delta-Ferrite in the Novel High Silicon Ferritic/Martensitic Steels
The microstructures of novel high silicon ferritic/martensitic steels were studied by optical microscope, scanning electron microscope and transmission electron microscope, also the mechanical properties were investigated. It is found that the addition of silicon in the steel can increase the fraction of the delta-ferrite. However, the delta-ferrite will be eliminated by increasing the carbon content to 0.25%. Delta-ferrite will reduce the strength but not decrease the toughness. Meanwhile, the matrix continuity is interrupted by the stripe-like delta-ferrite distributed along the rolling direction, which makes the fractographies of impact specimens show lamination characteristic.
2013 Vol. 48 (5): 62-67 [
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68
SUN Yong-qing,LIANG Jian-xiong,YANG Zhi-yong,LI Wen-hui,ZHANG Li-na
Effect of Composition and Heat Treatment on Microstructure and Mechanical Property of AM355 Steels
In order to raise the strength and hardness of AM355 steel for the demand of aircraft material, three AM355 steel bars with different compositions were investigated, which were prepared by VIM+ESR technique and forged into 80mm. Mechanical properties were tested after different temperatures quenching, same cold treatment and tempering. The results indicate that, under the same w(Creq)/w(Nieq), the AM355 steel bar with higher molybdenum content has higher strength, hardness and certain toughness. Strength and hardness of the bar after best heat treatment (1000℃×1h AC+（-70℃）×8h+450℃×2h AC+200℃×2h AC) can be raised about 100MPa in strength and HRC 5 in hardness. Details of mechanical property are as follows, Rm 1630MPa,ReL 1380MPa,A 16%,Z 59%, and impact energy 51J, HRC50. The types and precipitations of carbides in the AM355 bar were carried out by SEM and TEM, and strengthening mechanism was also searched. In conclusion, w(Mo) and the quenching temperature have main effect on strength and hardness.
2013 Vol. 48 (5): 68-71 [
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72
LI Guo-ping,,,LI Jian-chun,,ZHANG Shou-lu,,QIN Li-yan,,PEI Hai-xiang,
Effect of Hot Treatment on Microstructure and Properties of S32003 Lean Duplex Stainless Steel
The influence of different hot treatments on mechanical properties, metallurgical structure and corrosion resistance of S32003 DSS was investigated. The results show that with the increasing of temperature range from 850℃ to 1100℃, the strength and hardness of S32003 plate were decreased, and elongation increased. During heat treating at 850-900℃, saw-tooth and spotted second phases can be precipitated in the ferrite grain and on the phase boundaries between ferrite and austenite which will be harmful to corrosion resistance. The second phases was solved as heat treating above 950℃. The phase structure analysis by TEM shows that these second phases are Cr2N.
2013 Vol. 48 (5): 72-76 [
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Technology Exchange
81
LI Xin-lei,YANG Chun-wei
Application of Controlled Cooling Process After Normalizing in the Development of Heavy Gauge Ship Plate
The controlled cooling process after normalizing is the combined process of cooling process and normalizing. Because the temperature of austenization is as the same as the normalizing, the finer microstructure of ferrite and pearlite can be obtained after water cooling. Experimental study was performed in the development of 120mm E36 ship plate steel, and the “weak water-cooling” model of quenching experiment was used after normalizing. The final cooling temperature was between 600℃ and 650℃. Compared with the traditional air cooling after normalizing, the plasticity doesn’t decrease, and the strength increases by about 15MPa. Low-temperature toughness is good, especially the -60℃ impact energy in the center is over 100J. The more fine and uniform ferrite-pearlite microstructure can be obtained by experiment. The mechanical properties index can meet the standard requirement of E36 ship plate. The results have important significance in the development of heavy gauge ship plate.
2013 Vol. 48 (5): 81-86 [
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