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	2018 Vol. 53 No. 12
	Published: 2018-12-15

	1	MA Fu-tao，ZHANG Jian-liang，ZHANG Lei，JIAO Ke-xin，HAO Liang-yuan，LIU Fu-long
		Introduction of development and progress of mathematical modeling technology in iron-making area and discussion on application prospects of big data technology
		The blast furnace expert system is a typical representative of the highly integrated mathematical modeling technology in the iron-making area in recent decades. The development history and the general situation of the iron-making expert system were reviewed， and historical limitations and technical bottlenecks of the expert system technology were analyzed. Furthermore， the inheritance and the progress of the iron-making mathematical modeling technology in recent years were introduced， as well as achieved results. Finally， according to the actual requirement and status of the present steel industry， application prospects and research directions of big data and machine learning technology in the iron-making area were discussed， especially in the blast furnace area.
		2018 Vol. 53 (12): 1-9 [Abstract] ( 301 ) [HTML 1KB] [PDF 2231KB] ( 931 )

	10	GAO Peng，ZHAO Dan-ning，WANG Ping，LI Hua-jun，YU Chang-you，WEI Ru-fei
		Study and application on combustibility of pulverized coal injection at 4 000 m3 BF of Masteel
		Increasing the quantity of powdered coal injection in blast furnace has very important effect on reducing coke ratio. Six kinds of raw coal pulverized coal and four kinds of mixed pulverized coal of blast furnace were taken ，then the experimental materials， the industrial analysis， the coal petrography analysis and the thermal gravimetric analysis were studied in this experiment. Besides， the effects of oxygen enrichment， granularity， air temperature on the combustibility of pulverized coal were studied as well. The results showed that with the increasing of the oxygen enrichment， it has a great effect on the combustibility of bituminous coal and soft coal and has little effect on the combustibility of hard coal. The granularity has a great influence on the combustibility of bituminous coal and soft coal， and the combustibility of hard coal was significantly improved only when the 0.074 mm of coal was more than 65%.With the temperature of the hot air increasing， the combustibility of bituminous coal was increased most. In addition， it also has a certain effect on the soft coal combustibility and small effect on the combustibility of hard coal. In coal blending，the ratio of soft coal should be increased， the ratio of hard coal should be reduced and the ratio of bituminous coal should be stabilize. When the coal rate of the 4 000 m3 blast furnace increased from 140 to 160 kg/t in Masteel， the increase of unburned pulverized coal in the blast furnace dust was only 2.22 kg/t.
		2018 Vol. 53 (12): 10-17 [Abstract] ( 382 ) [HTML 1KB] [PDF 1783KB] ( 763 )

	18	FU Zhong-wang，MO Chao-xing，CHEN Xiao-min，ZHAO Yong，，YUCHI He-peng，WU Keng
		Influence factors of fluidity characteristic number of iron ore powder
		In order to determine the rule of liquid phase fluidity of iron ore fines， the fluidity characteristic number was used to characterize the fluidity of the liquid sintering phase. The characteristic number consists of kinds of important process information， including the actual temperature of the sintering production. Consequently， the characteristic number can be used to distinguish the fluidities among different iron ore powders objectively and accurately. By changing the chemical composition of the iron ore powder， the influence of the non-iron containing oxide on the fluidity characteristic number was investigated. The results show that with the increasing of the mass percent of SiO2， Al2O3 and MgO in iron ore powders， the flow temperature of the liquid increases gradually， the flow rate decreases gradually， and the fluidity characteristics number decreases in different levels. Therefore， the mass percent of the three compositions， SiO2， Al2O3 and MgO， should be controlled within a certain range. The effect of carbon on the fluidity characteristic number of iron ore on the type of the iron oxide in ore powder.
		2018 Vol. 53 (12): 18-23 [Abstract] ( 334 ) [HTML 1KB] [PDF 1561KB] ( 697 )

	24	GAO Qiang-jian，HE Yun-feng，LIU Zhao，YANG Fu-cai
		Fundamental of explosibility of pulverized coal injection and suppressed measures
		The explosibility of pulverized coal injection （PCI） is a main concern for metallurgical industry enterprises. The main factors which affect the explosibility of pulverized coal in PCI process were studied. Additionally，the effective measures for suppressing explosive of PCI were proposed. It has been found that the reasonable blended proportion of bituminous coal and anthracite can be utilized to adjust the explosibility of the coals. With the increasing of the proportion of anthracite，the explosibility of PCI decreases gradually. Therefore，the proper proportion of blended coals between the bituminous coal and anthracite should be determined based on ensuring safe injection and achieving the low-cost of PCI. Physical properties of pulverized coal also play an important role in explosibility. As the volatile matter mass percent increases from 24.63% to 30.65%，the explosibility index（L） of pulverized coal raises nearly three times. Similarly，with the proportion of 0.074 mm for pulverized coal granularity decreases from 100% to 50%，the explosibility also appears decreasingly. Moreover，the explosibility is found to be significantly going up with the increasing of oxygen concentration in atmospher. For instance，a kind of blended coal which has no explosibility in the air shows strong explosibility in the high oxygen concentration atmosphere. Moreover，by adding MgCO3·5H2O in blended coals，the explosibility can be effectively suppressed，the L drops by 61.67% as the portion of additive is 6.0%，which means that MgCO3·5H2O has an advantageous action for suppressed explosibility.
		2018 Vol. 53 (12): 24-29 [Abstract] ( 364 ) [HTML 1KB] [PDF 1168KB] ( 783 )

	30	KOU Ming-yin，WU Sheng-li，ZHOU Heng，YU Ya-guang，GU Kai
		Measurements and application of burden coefficients for DEM simulation in blast furnace
		It is necessary to experimentally measure the coefficients used in the discrete element method （DEM） simulation in order to guarantee the accuracy of the simulation from the source. Therefore， static friction coefficients and restitution coefficients between different burden materials used in the DEM simulation are measured by experiments. The rolling friction coefficients between burden materials are determined by validating the repose angle of the burden. Parameters of burden materials used in the DEM simulation are determined， which provides a database for the accurate DEM simulation.
		2018 Vol. 53 (12): 30-36 [Abstract] ( 405 ) [HTML 1KB] [PDF 904KB] ( 907 )

	37	LOU Wen-tao，LIU Zhuang，WANG Xiao-yu，ZHU Miao-yong
		Numerical simulation of slag-metal reaction and desulfurization behavior in gas-stirred ladle
		In order to improve the desulfurization efficiency of the gas-stirred ladle，a computation fluid dynamics-simultaneous reaction model （CFD-SRM） coupled model was proposed to describe the desulfurization behavior in a gas-stirred ladle. In present model，the effect of liquid-gas two phase flow caused by bottom blowing，and the oxygen absorption and oxidation reactions in slag eyes were considered，and model verification was carried out by 80 t ladle hot experiment. The effects of different blowing conditions on desulfurization efficiency in gas-stirred ladles were investigated. The results show that the gas-liquid two-phase flow has an important influence on the mass transfer rate of components and the desulfurization efficiency，and the predicted sulfur content changing with time in ladle agrees well with the measured data. The desulfurization efficiency of dual blowing is higher than that of single center or eccentric blowing. With the increasing of slag-metal height ratio，the desulfurization efficiency increases. But once the slag-metal height ratio exceeds 0.04，the desulfurization efficiency changes little. As the gas flow rate increases，the desulfurization rate increases first and then decreases. But when the bottom blowing flow exceeds 300 L/min，the desulfurization rate begins to decrease.
		2018 Vol. 53 (12): 37-43 [Abstract] ( 323 ) [HTML 1KB] [PDF 2042KB] ( 1048 )

	44	LIU Yan-qiang，ZHANG Peng，HE Wen-yuan，YANG Xiao-shan，HUANG Cai-de，ZHAO Chang-liang
		Transformation behavior and control of inclusions in X65 pipelinesteel during whole process
		The cause of nonconformity in flaw detection of X65 pipeline steel was determined by analyzing the process of inclusions transformation. Meanwhile， a reasonable calcium treatment process was proposed to control B type inclusions and reduce the rate of flaw detection. The results show that the transformation process of inclusions in primary process was Al2O3→MgO-Al2O3→MgO-Al2O3-CaO→CaO-Al2O3. And final inclusions were mainly calcium aluminate containing high mass percent of CaO in the low melting point area. Inclusion control target in the pipeline steel was proposed by the thermodynamic calculation and a model of the calcium treatment of the molten steel was established. According to the actual condition of molten steel，the reasonable calcium treatment control window was calculated to guide the practical production under the condition of different S and T[O] mass percent， by optimizing the treatment process， the mass percent of calcium in molten steel was reduced from 0.003 0%-0.004 0% to 0.001 0%-0.002 0% for the original process. The type of inclusions was consist of MgO- Al2O3-（CaO）-CaS including the low melting point and the high melting point phase composites. The first pass percent of severity of B inclusions≤2.0 was enhanced to 97.5% from 96.5%. The rate of nonconformity in the flaw detection was reduced from 10.0% to 1.5% and the quality of pipeline steel was improved remarkably.
		2018 Vol. 53 (12): 44-53 [Abstract] ( 477 ) [HTML 1KB] [PDF 3282KB] ( 898 )

	54	WU Guo-qing，QIU Ming-gang，DAI Zong-ling，CHEN Wei-qiang，ZHANG Wen-yong
		Design features and production practice of modern alloy steel bloom caster
		Capital Engineering and Research Incorporation Limited devotes itself to the independent design and independent innovation of the localization bloom caster. For a long time，breakthroughs have been made in the research of key technologies for improving the quality of bloom. The core technology and the key equipment of the 6-strand bloom caster which independently designed by Capital Engineering and Research Incorporation Limited Company were introduced. The design features of key technologies to ensure the quality of the bloom were systematically described. The application of the electromagnetic stirring，the soft reduction and the hard reduction in the improvement of the inner quality of the bloom were expatiated respectively. The practical metallurgical effect of the typical high carbon grinding ball steel was introduced in detail，and the development trend of continuous casting technologies for the bloom production was pointed out. Production practices showed that： at a given speed，ensuring the reasonable position of the final stirring，the reasonable soft reduction and the reasonable hard reduction，the optimized stirring and reduction process parameters could significantly reduce the center segregation and "V" segregation of high carbon steel，improve the center shrinkage and eliminate the center porosity. During the 310 mm×360 mm typical steel BU（w（C）＝1%） casting process，at the speed of 0.5 m/min，the carbon segregation index along the thickness direction was between 0.93-1.08，and the carbon segregation index along the longitudinal direction was between 0.95-1.09. According to the industry standard （YB/T 4002—2013），the center shrinkage no less than grade 1.
		2018 Vol. 53 (12): 54-61 [Abstract] ( 505 ) [HTML 1KB] [PDF 1540KB] ( 948 )

	62	REN Zhong-kai，WANG Tao，WANG Yue-lin，FAN Wan-wan，FU Wen-shi，GUO Xiong-wei
		Analysis of contact contour and contact pressure in deformation zone of ultra-thin strip rolling
		The accuracy of the rolling force model plays a decisive role in the control of the strip thickness in the rolling process. The conventional rolling theories assumes that the roll is a circular arc. However，as the ultra-thin strip thickness decreases，the contact arc length of the deformation zone is much greater than the strip thickness，resulting in a non-circular contour. For the above problems，Fleck accurately solved the roll contour in the deformed zone based on the Hertzian contact theory，and established a new rolling force model. However，the Fleck’s analytical method is more complex，where different calculation methods have been established for different rolling conditions. To establish a simplified analysis method，not only the expression forms of rolling force and friction force in the entire deformation zone are unified，but also the elastic unloading phenomenon in the neutral zone is ignored. Then，by comparing the results calculated by simplified model with the results calculated by Fleck model and measurements，the accuracy of the simplified analytical model is verified. The influence of different factors on the contact arc profile and contact pressure distribution in the deformation zone is analyzed by the simplified model. The results show that with the decrease of the inlet strip thickness and the elastic modulus of the work roll，and the increase of the reduction，the elastic flattening of the work roll in the deformation zone becomes more and more serious.
		2018 Vol. 53 (12): 62-68 [Abstract] ( 386 ) [HTML 1KB] [PDF 1271KB] ( 756 )

	69	HU Ke，SHEN Xin-yu，QU Yi-zhen，DAI Xiao-hua，MA Xiao-bao，WANG Dong-cheng，
		Fine control technology of strip profile for 6-high reversible universal crown cold rolling mill
		Aiming at the profile control of the cold rolled strip in the 6-high reversible universal crown mill （UCM），the deformation mechanism of cold rolled strip was revealed by simulation calculation. The control effects of the intermediate roll shifting and bending and the work roll bending on the profile and the flatness were analyzed，and limitations of these control methods were noted. Then，the control effects of the work roll contour on the profile and the flatness were analyzed，and the design principles of work roll contours were obtained. On the basis of this，a technical scheme named "fine optimization of roll contours＋ adjustment of flatness target " was proposed for the reversible UCM，which finally improved the control effect for the strip edge drop. The technical scheme was applied to three sets of 1 420 mm reversible cold rolling UCM，and the transverse thickness difference of the silicon steel was significantly reduced，which provided a useful reference for profile control methods of similar rolling mills.
		2018 Vol. 53 (12): 69-76 [Abstract] ( 395 ) [HTML 1KB] [PDF 1495KB] ( 775 )

	77	GENG Si-yuan，，YANG Mao-sheng，ZHAO Kun-yu
		Influence of temperature on high cycle fatigue properties of high cobalt molybdenum stainless bearing steel
		In order to improve the service life and reliability of aerospace bearings，the high cycle rotating bending fatigue properties and failure modes of high cobalt molybdenum stainless bearing steel at different temperatures were studied. With the increase of temperature，the fatigue limit strength of steel decreased gradually. The fatigue limit strength of the steel was 927，840 and 667 MPa respectively under the condition of 25，300 and 500 ℃. The fatigue limit strength of the steel was reduced by 9.4% and 28.0% respectively at 300 and 500 ℃. At 25 ℃，the crack initiation was caused by surface ravine resulting in stress concentration. When the temperature rised to 300 ℃，the hardness of the fatigue specimen decreased and the persistent slip bands appeared under the action of long time alternating stress. At 300 ℃，carbides precipitate and growth accelerated crack initiation. At 500 ℃，the hardness of the matrix continued to decline，so that the persistent slip bands were more likely to occur. Under the action of thermomechanical coupling，the carbides on the edge of the fatigue specimen precipitated，and the carbides growed when heated for a long time. The carbides interacted with the dislocation and produced tiny cracks on the edge of the carbides in the persistent slip bands. The precipitation and growth of carbides accelerated the propagation of fatigue cracks.
		2018 Vol. 53 (12): 77-85 [Abstract] ( 405 ) [HTML 1KB] [PDF 3247KB] ( 734 )

	86	LIU Xin，FENG Guang-hong，ZHANG Hong-liang，QI Yuan-hong
		Effect of billet direct rolling process on difference in microstructure and mechanical properties of rebar
		The billet direct rolling process is the trend of the future development of rod and wire rolling production which refers to a new process in which the high temperature billet is directly fed into the mill for rolling by increasing the casting billet temperature of the caster. The finite element method（FEM） was adopted to simulate the rolling process of billet and to determine the effect of billet direct rolling process on the difference of microstructure and mechanical properties of a HRB400 rebar. The effect of billet direct rolling process on the volume fraction of each phase and grain size distribution of the rebar with a cut-lengths of 9 m was calculated，and the mechanical properties of rebar were predicted with the constitutive equation of mechanical properties. The results showed that the microstructure of rebar produced by billet direct rolling process was mainly composed of ferrite，pearlite and trace bainite，of which the average volume fraction was 61.4%，38.4% and 0.2%，respectively. Compared with the traditional hot rolling process，the billet direct rolling process could increase the volume fraction of pearlite and reduce the ferrite volume fraction. There were some differences in the axial distribution of the grain size of the rebar produced by the billet direct rolling process，the average grain size in the head region，the middle region and the tail region of the rebar were 7.4，7.9 and 8.5 μm，respectively. In addition，the upper limit value of the yield strength of the rebar was 454 MPa，and the lower limit value was 449 MPa，which showed that the yield strength difference between the head region and the tail region of the rebar with a cut-lengths of 9 m produced by direct rolling process was about 5 MPa，and the difference of mechanical properties could not be ignored.
		2018 Vol. 53 (12): 86-93 [Abstract] ( 404 ) [HTML 1KB] [PDF 1608KB] ( 1123 )

	94	FU Gui-qin，LI Dong-liang， ZHU Miao-yong
		Effect of SO2 on corrosion behavior of Cr-containing weathering steel in simulated marine atmosphere
		In order to study the effect of industrial air pollution on the corrosion behavior of Cr-containing weathering steel in marine atmosphere，the alternative wet/dry cyclic accelerated corrosion tests，using NaCl and NaHSO3 solutions as corrosive medium，and XRD，SEM were employed in tested steels with and without Cr which were vacuum induction melted and rolled，comparing the corrosion behavior in simulated marine atmosphere which contains and does not contain SO2. The results showed that the corrosion depth was decreased by the addition of Cr while was increased by the presence of SO2. The rust of two samples was both mainly composed of α-FeOOH，β-FeOOH，γ-FeOOH and Fe3O4. The transformation of Fe3O4 to α-FeOOH was promoted by the addition of Cr. The formation of β-FeOOH was hindered by SO2. Meanwhile，the transformation from γ-FeOOH and Fe3O4 to α-FeOOH in Cr-containing tested steel was promoted by the existence of SO2. Cr enriched in the inner rust layer which could help to increase the weather resistant performance. When there is no Cr in the steel sample，S and Cl enriched in the inner rust layer. However，0.43% Cr had shown the trend of cation selectivity since S enriched in the outer layer and Cl distributed evenly in both Cl? and Cl?＋SO2 containing environment.
		2018 Vol. 53 (12): 94-99 [Abstract] ( 209 ) [HTML 1KB] [PDF 1305KB] ( 700 )

	100	JIANG Bo，CHEN Gang，ZHAO Hai，XIAO Wei-rong，LIU Peng，REN Xue-chong
		Fatigue propagation behavior of mixed mode crack in wheel steel
		In order to accurately assess the safety of wheel rim with defects，fatigue testes of type I crack，type II crack and type I＋II mixed mode crack under different loading conditions were done. The threshold value of fatigue propagation of mixed mode crack of wheel steel was obtained，and a suitable prediction criterion of mixed mode crack fatigue expansion for wheel steel was verified. The results show that the crack propagation direction for the I＋II mixed mode crack is basically consistent with the predicted value of the maximum tangential stress （MTS） criterion in test. The equivalent threshold value of fatigue crack propagation for I＋II mixed mode crack is ΔKth，equ＝3.0-3.8 MPa·m1/2（load ratio R＝0.5）. The microcracks were formed at the tip of prefatigued crack mainly by shear stress. The microcrack at the zone with tensile-shear stress is extended continuously，but microcrack at the zone with compression-shear stress can be formed but it stopped after a few tens of micrometers propagation.
		2018 Vol. 53 (12): 100-104 [Abstract] ( 413 ) [HTML 1KB] [PDF 1071KB] ( 829 )

	105	GONG Xue-ting，WU Zhi-guang，LI Xin，ZHAO Meng-ya，PENG Tao
		Effect of heat treatment process on microstructure and mechanical properties of 20Cr1Mo1VTiB steel
		In order to optimize the heat treatment process of 20Cr1Mo1VTiB steel，the effect of heat treatment process on microstructure and mechanical properties of the steel was investigated experimentally by means of SEM，TEM and mechanical properties tests. The results show that the heat treated microstructure of 20Cr1Mo1VTiB steel is bainite，and the main strengthening phase is VC and needle-like M3C. With elevating the quenching temperature，the room and high temperature tensile strengths increase while the toughness decreases duo to the gradual dissolving of VC into the matrix and the increase of solid solution strengthening effect. When the steel is tempered at low temperature，the dislocation density in bainite laths is very high and the microstructure stress is great. This leads to high strength and low toughness of the steel. While with increasing the tempering temperature，the room and high temperature tensile strengths decrease and the toughness improves significantly as a result of an increase in VC size and the gradual recovery of the microstructure. 20Cr1Mo1VTiB steel shows a good combination of strength and toughness after quenching at 1 030 ℃ and tempering at 720 ℃.
		2018 Vol. 53 (12): 105-111 [Abstract] ( 555 ) [HTML 1KB] [PDF 3518KB] ( 984 )

	112	XIA Tian ，XIANG Zhi-dong，HE Zhu，HU Shou-tian，LUO Zhong-han
		Numerical simulation of vapour diffusion in annular furnace during high temperature annealing
		Since the atmospheric moisture content has a significant influence on the quality control of the oriented silicon steel during the high temperature annealing process，the variation law of the moisture content in the gas entrapped in the gaps between the coil layers in the annular furnace was studied. Relationship between the heating rate and the deposition rate of Mg（OH）2 in the coating of strip was analyzed，and the uniform distribution law of the vapour in the cover during the annealing process was proved by experiments. The model of the vapour diffusion in the annular furnace was built. The results showed that the deposition rate of Mg（OH）2 differed at different parts of the coil because of the different heating rates，and it cost about 28 h to drain the water in the coil completely. The water content of the protective atmosphere and the width of gaps between coil layers have a significant impact on the drainage rate，and the difference of the average water content is more than 20% in some specific conditions. The vapour is entrapped at the bottom of coil due to the insufficient distance between coil and the plate. Furthermore，the application of the hollowed out plate can reduce the average water content between the coil layers significantly.
		2018 Vol. 53 (12): 112-117 [Abstract] ( 345 ) [HTML 1KB] [PDF 1082KB] ( 847 )

	118	WEI Jie-ping，XU Zhi-qiang，SUN Ming-han，ZHU Zhi-wang，WANG Hai-jun，DU Feng-shan
		Experimental research of vibratory cast-rolling strips for 20CrMn alloy steel
		In order to investigate the influence of the mechanical vibration applied in the technology of twin-roll strip cast-rolling on the microstructure and mechanical properties of the cast-rolling strip，a ?500 mm×350 mm micro-amplitude twin-roll strip cast-rolling mill was designed and manufactured. The casting mill was used as an experimental platform for a number of process exploration experiments，and the reasonable process parameters that could achieve stable production of twin-roll vibratory cast-rolling strips were finally determined. Then the microstructure and mechanical properties of the 20CrMn alloy steel cast-rolling strip obtained under vibratory and vibrationless conditions were tested and analyzed. The microstructure observation result shown that the average grain size of the normal surface of the vibratory cast-rolling strip reduced from 70 to 35 μm compared with the vibrationless one，and the grains on the vibratory and the vibrationless side of the longitudinal section of the vibratory cast-rolling strip were also refined to different degrees.The tensile test result shown that the yield strength，tensile strength and elongation of the vibratory cast-rolling strip in the vertical-rolling direction were respectively 21.36%，27.35%，42.86% higher than those of the conventional vibrationless cast-rolling strip. The above research results prove that mechanical vibration can effectively improve the microstructure，refine the grains，and improve the mechanical properties of the strip.
		2018 Vol. 53 (12): 118-121 [Abstract] ( 260 ) [HTML 1KB] [PDF 1268KB] ( 893 )

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