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	2015 Vol. 50 No. 7
	Published: 2015-07-15

	1	ZHANG Jian-liang，，WANG Cui，，ZUO Hai-bin，，JIAO Ke-xin，WANG Zhi-yu
		Future prospects and research progress of chlorine in blast furnace system
		In order to clarify the influences of chlorine on smelting process of BF dry dedusting technology， the occurrence， behavior and effect of chlorine carried in by raw materials are summarized. Further， the source of chlorine in Guofeng No.1 1 780 m3 BF dry dedusting technology were investigated by ion chromatography， with the consequence of 45.4 % chlorine from coke and 29.48 % from pulverized coal， while the main chlorine source in three other BFs dry dedusting technology from Baosteel， Tangsteel and Qian’ansteel is sinter， accounting for 47.12 %， 43.59% and 44.89%， respectively， which mainly derives from the difference in species， quantity and chlorine content of raw materials， so it should be given concrete BF to analyze the chlorine source. The chlorides in raw materials react into HCl in BF through thermodynamic analysis. Based on previous research， measures for decreasing chlorine in BF system are put up forward， as well as related directions for future research.
		2015 Vol. 50 (7): 1-7 [Abstract] ( 1095 ) [HTML 0KB] [PDF 0KB] ( 57 )

	8	ZHU De-qing，LI Xiao-bo，PAN Jian，SHI Ben-jing
		Investigation of granulation behaviors of specularite fines in ferrous sinter mixture
		The granulation behaviors of specularite fines in ferrous sinter mixture were studied. The results showed that the moisture had a great effect on granulation， and the optimal moisture content decreased with the increasing specularite fines ratio in the mixture. The dynamic results with different specularite fines ratio showed that the adhering load of specularite fines increases rapidly within 3 min and then levels off. With an increase of specularite fines ratio， the duration needs longer time to reach adhering balance. Therefore it’s an effective way to improve the granulation by extending granulating time at high specularite fines ratio. The microstructures of the layer showed that particles of specularite fines scatter all over the layer without combination which infers that the particles of limonite fines act as a binder between specularite fines and improve the strength of the adhering layer. Granulation and specularite fines ratio could be improved by using specularite fines and limonite fines in the mixture properly.
		2015 Vol. 50 (7): 8-14 [Abstract] ( 1190 ) [HTML 0KB] [PDF 0KB] ( 41 )

	15	SHI Shi-zhuang，LU Shuai，BI Xue-gong，LI Peng，MAO Yan-gao，ZHENG Qi
		Decreasing of reaction beginning temperature of iron coke and its mechanism
		At the ratio of iron ore powder of 10%， the influence of Canadian iron ore powder， Australian iron ore powder and E-Xi iron ore powder on reactivity， reaction beginning temperature and activation energy， etc. of iron cokes are researched systematically. The results show that， the reaction beginning temperatures of iron cokes decrease obviously， the decreasing extent depends on the type and property of iron ore powder； the mechanism should lie in the iron ore powders which make the activation energy of the iron cokes decreases and lead to reactivity of iron cokes increase； and the correlation among reaction beginning temperature， activation energy and reactivity is very well.
		2015 Vol. 50 (7): 15-19 [Abstract] ( 1053 ) [HTML 0KB] [PDF 0KB] ( 75 )

	20	WANG Zhe，ZHANG Jian-liang，ZUO Hai-bin，GAO Bing，LI Feng-guang，WANG Run-bo
		Influence of Al2O3 content on softening-melting property of high basicity sinter
		Softening and melting tests under load of sinter with varying Al2O3 content were carried out. In addition， microstructure and mineral composition of sinter at different temperatures were also analyzed and the mechanism that the effect of Al2O3 content on sinter softening and melting property was elucidated. Results showed that the increase of Al2O3 content in sinter favored the formation of Al2O3-rich slag phase with lower melting point， such as gehlenite (2CaO·Al2O3·SiO2) and the eutectic (2CaO·SiO2-2CaO·Al2O3·SiO2-FeO)， resulting in the blockage of open pore. During melting-dripping process， slag phase of high Al2O3 sinter had a relative higher Al2O3 content. With the increase of Al2O3 content， the liquidus temperature and viscosity of slag phase existing between metallic iron particles was deteriorated. It decreased the concentration of metallic iron and then increased the dripping temperature. Meanwhile， high Al2O3 content sinter was associated with a thicker melting-dripping zone， leading to the deterioration of sinter bed permeability.
		2015 Vol. 50 (7): 20-25 [Abstract] ( 1357 ) [HTML 0KB] [PDF 0KB] ( 52 )

	26	CHU Ren-sheng
		Aggregation of inclusions for calcium aluminate with high-melting point
		The size， area， composition， type and distribution of non-metallic inclusions with high-melting point (CA2 and CA6， which C： CaO， A： Al2O3) in inspection substandard samples were analyzed by aspex explorer automated scanning electron microscope. To analyze the reason that why the center is the concentrated area of the large-size inclusions， three aspects for the causes of calcium aluminate with high-melting point causing the aggregation behavior for flaw substandard is focused on： features of non-metallic inclusions， the characteristics of continuous casting machine and the behavior of nonmetallic inclusions during the process of solidification. The results show that calcium aluminate with high-melting point gathered together， and is easy to aggregate. The casting speed is slow for the curved continuous casting machine compared with the average arc caster. The thickness of slab is thin and the molten steel solidifies rapidly， which makes the solidification end generate early， and form an easy gathering area near the center during the steel solidification. The inclusions are pushed and engulfed in the shell and will aggregate. While the space and time of floatation is reduced， combined with the effect of promoting the capture， the center forms a concentrated area of the large-size inclusions.
		2015 Vol. 50 (7): 26-31 [Abstract] ( 1120 ) [HTML 0KB] [PDF 0KB] ( 81 )

	32	Lü Sha，WU Guang-liang
		Non-metallic inclusion and total oxygen in 50Cr5MoV
		The total amount of oxygen content and the category of inclusions in 50Cr5MoV forged steel roll by the route of EBT→LF→VD were analyzed . The results show the average[w(T[O])]was 0.004 7% after LF refining and 0.001 4% after VD refining，and 0.001 55% in tundish，0.001 8% in billet and 0.001 0% in rolled steel on average. During the initial stage of LF refining， the inclusions in steel mainly are irregular forms of Al2O3. 96.75% of the inclusions have the diameters less than 10 μm.After the LF refining， most of the inclusions are 0-10 μm diameters of compound oxide inclusions， predominantly containing CaO-Al2O3-SiO2.During the transfer of steel from VD treatment to tundish，the protective casting is awful， and the severe reoxidation contributes to the growing amount of inclusions， mainly containing spherical [mCaO·nAl2O3] compound oxide inclusions 99.65% of the inclusions in the steel slab are less than 10 μm. Most of them are spherical calcium-aluminate compound inclusion， with a few spherical calcium aluminosilicate compound inclusion. And 98.77% of the inclusions in rolled steel have diameters less than 10 μm Therefore， the process optimization of every process of iron making， could contribute to the effective control of inclusions and ensure the quality of 50Cr5MoV forged steel roll.
		2015 Vol. 50 (7): 32-37 [Abstract] ( 1088 ) [HTML 0KB] [PDF 0KB] ( 67 )

	38	WANG Wei，ZHOU Lü-min，XIONG Li，XUE Zheng-liang
		High temperature mechanical property of SS400 B-bearing steel slab
		In order to avoid and reduce surface cracks of SS400 B-bearing steel slab， the high temperature mechanical properties of SS400 B-bearing steel slab have been investigated in the temperature range of 650-1 350 ℃ by the hot tensile test technique with Gleeble-1500 system. The results showed that its yield strength and tensile strength in the temperature range were relatively small；in general，which decreased with increased tested temperature. Only in the range of 1000-1 100 ℃，SS400 B-bearing steel slab has good hot ductility and the reductions of area were higher than 90%. The third brittle zone of the SS400 B-bearing steel is between 700-950 ℃. The low plasticity temperature range is relatively wide，because of boron segregation in grain boundaries and precipitation of BN leading to the grain boundary embrittlement. Because of the remelting phenomenon of B-bearing steel，the plasticity can be reduced when the temperature lies between 1 150-1 250 ℃.
		2015 Vol. 50 (7): 38-42 [Abstract] ( 1439 ) [HTML 0KB] [PDF 0KB] ( 73 )

	43	ZHAO Jing，ZHEN Xin-gang，ZHU Zhi-yuan，WANG Yu-long，ZHANG Hu-cheng，ZHAO Xin-yu
		Formation mechanism and control method of longitudinal corner crack on slab with chamfering mold
		Chamfering mold is one of the effective methods for controlling the transverse corner cracking of slab. However the longitudinal corner cracking will occur in slab with chamfering mold， which is the most critical hinder for wide usage of chamfering mold. The effects on longitudinal corner cracking of chamfered slab of process parameters and equipment accuracy as well as spray nozzle blocking are analyzed. The formation mechanism of longitudinal corner cracking has been found. Research shows that， the main causes of longitudinal corner cracking are the inconsequence taper of narrow face， the deviation of 0 and 1 section connection and spray nozzle clogging. Through effective measures，chamfering mold can be extensively applied to industry manufacture as the percentage of occurrence for longitudinal corner cracking of CC slab is reduced below 0.6%.
		2015 Vol. 50 (7): 43-47 [Abstract] ( 1153 ) [HTML 0KB] [PDF 0KB] ( 70 )

	48	LI Xue-tong，LI Dong-ying，WANG Jun-jie，WANG Min-ting，YU Feng-qin，DU Feng-shan
		Optimization of oval-round pass design using multi population genetic algorithm in bar rolling
		Aiming at the pass premature optimization problem based on the current bar rolling，the study proposes multi population genetic algorithm that can solve the premature convergence problem in standard genetic algorithm，and makes optimization analysis on multi population genetic algorithm which was combined with the geometric parameters of elliptical hole in bar rolling from a certain steel mill. The two-pas continuous rolling process before and after optimization has been simulated based on the rigid plastic finite element method. Change of rolling force in the rolling process has been analyzed in detail. Combined with the Matlab curve fitting and symbolic integration method，the rolling energy consumption before and after optimization has been calculated and compared. The continuous rolling experiment of lead has been implemented，which has validated the reliability of simulation results. The results show that the pass after optimization can reduce the rolling force and rolling energy consumption effectively.
		2015 Vol. 50 (7): 48-53 [Abstract] ( 1181 ) [HTML 0KB] [PDF 0KB] ( 62 )

	54	WANG Dong-cheng，，ZHAO Zhang-xian，LIU Hong-min，
		High-efficiency software and its application for shape analysis and presetting of cold rolling strip
		In view of the low calculation speed and poor stability of theory models for shape analysis， high-efficiency shape prediction model and high-efficiency shape presetting model are presented. Based on the high-efficiency models，a set of high-efficiency software is developed for shape analysis and presetting. The software is universal for different four-high and six-high cold rolling mill，and its main feature is the significant high speed and high stability without sacrificing calculation precision. Through two examples，the software is proved to be reliable，and the calculation time of shape analysis and presetting for common cold tandem mill with five stands is less than 1 s. The software can be used to in the fields of mill design，mill selection and optimization roll contour，and its core code can be used to preset the shape on-line directly.
		2015 Vol. 50 (7): 54-60 [Abstract] ( 1102 ) [HTML 0KB] [PDF 0KB] ( 70 )

	61	CAI Jun，WANG Hong-bing，TIAN Nai-yuan，XU An-jun，HE Dong-feng
		Calculation model for the turnover number of steel ladles based on furnace-caster matching principle
		In order to optimize the production organization and dynamic-orderly operation in the steel-making plant，a scientifically reasonable calculation model for the number of turnover ladles was proposed. The turnover process of steel ladles was analyzed in Q steel-making plant. Based on furnace-caster matching principle，the relationship between the production rhythm of furnace-caster and the number of turnover ladles was analyzed with Gantt chart. A calculation model for the number of turnover ladles was proposed for some specific modes of furnace-caster matching. The research showed that the number of turnover ladles can be reduced by shortening flexible time of turnover ladles and overlap time between casting heats.
		2015 Vol. 50 (7): 61-68 [Abstract] ( 1131 ) [HTML 0KB] [PDF 0KB] ( 56 )

	69	WANG Qian，PAN Hong-bo，YAN Jun，SUN Wei，GUO Zhan
		Water cooling process for cryogenic rebars
		According to the characteristics of water cooling process of cryogenic rebars， convective heat transfer coefficients of cryogenic rebar with different sizes were achieved by means of measured data and theoretical analysis. Based on the industrial trial results， the water cooling process of cryogenic rebar was investigated using MSC. marc finite element software. The effect of parameters， such as water flow， finishing rolling temperature， water cooling time on temperature field and microstructure transformation of cryogenic rebar were studied. The results show that when the cooling water flow is 120 m3/h， pearlitic transformation doesn’t occur in the center of steel rebar； when the cooling water flow is 400 m3/h， there is no ferrite transformation in the center of steel rebar； when the cooling water flow is 160-200 m3/h， the center of steel rebar has composite microstructure consisting of acicular ferrite and bainite. When the finishing rolling temperature rises by about 50 ℃， the surface temperature of steel rebar rises by about 10 ℃ and self-tempering temperature of steel rebar rises by about 30 ℃. When cooling water flow is 200 m3/h and cooling time is 1.2 s， the microstructure of steel rebar consists of acicular ferrite and fine bainite in the 1 050 ℃ finishing rolling. Under the condition of same water pressure and water flow， with the increase of finishing rolling velocity， the hardening layer depth decreases， and self-tempering temperature increases.
		2015 Vol. 50 (7): 69-76 [Abstract] ( 1807 ) [HTML 0KB] [PDF 0KB] ( 59 )

	77	CHEN Si-lian，ZHAO Xiao-li，HUI Wei-jun，DAI Guan-wen，DONG Han
		Precipitation behavior of medium-carbon steel for fracture splitting connecting rod
		The microstructure characteristics especially the distribution， morphology and particle size of vanadium carbonitride precipitates in hot-forged medium-carbon micro-alloyed steel for fracture splitting connecting rod with two different vanadium contents (0.15 %， 0.28 %) were examined by OP， TEM and XRD， and their precipitation behavior were analyzed. The results reveal that both the volume fraction of ferrite and the amount of V-rich M(C，N) particles increase， the pearlite interlamellar spacing decreases with increased V content. Further the physical-chemical phase analysis shows that about 48 % and 64 % V of the total in the steel are tied up in the M(C，N) precipitates of the two tested steels， respectively. Meanwhile， the mass percent of fine particles (less than 10 nm) in the two steels is about 42.6 % and 56.7 %， respectively， and the corresponding yield strength increments are 140.0 and 232.6 MPa. It’s concluded that medium-carbon steel with higher V content possesses not only has comparable tensile strength and impact energy absorbed with that of conventional steel C70S6 for fracture splitting connecting rod， but also has much higher yield strength and yield strength ratio， and therefore， is more suitable to fabricate high performance fracture splitting connecting rod.
		2015 Vol. 50 (7): 77-83 [Abstract] ( 1110 ) [HTML 0KB] [PDF 0KB] ( 48 )

	84	YANG Jin-wen，，ZHOU Wang-song，，LU Jian-sheng，YU Feng，XU Da， CAO Wen-quan
		Influence of α-Cr phase on new kind of austenitic alloy heat treatment organization and performance
		The effects of solid solution and aging treatment on the microstructure and hardness were studied through the combination of TEM， optical microscope and Rockwell hardness. Results indicated that the increase of the solid solution temperature would result in the decrease of the volume fraction of a-Cr phase，refining the grain size and lowering of the hardness and. The solid solution treatment was mainly controlled by the bulk diffusion of Cr in the austenite with a diffusion activation energy of （443±37） kJ/mol. After aging， the a-Cr particle size ranged from 0.5-2.0 μm with average value of about 1.6 μm. The hardness of the alloy after aging was mainly determined by the quantity of α-Cr in the matrix， which could give 61.5HRC in the maximum. Based on the study of the solution and aging treatment， it was proposed that solid solution temperature of GNiCRr40Al3Ti should be higher than 1 150 ℃ to fulfill its high hardness and machining requirement.
		2015 Vol. 50 (7): 84-91 [Abstract] ( 1092 ) [HTML 0KB] [PDF 0KB] ( 65 )

	92	XIANG Li-yang，，CHI Hong-xiao，MA Dang-shen，ZHOU Xiao-ling，ZHOU Jian
		Microstructure and properties of 4Cr13V corrosion resistant plastic mold steel with a large section
		It has been found that the quality of 4Cr13V corrosion resistant plastic mold steel modules with a large section fluctuates fiercely. Defects exist， such as serious osteoporosis， primary carbide residue， segregation and inclusion，which all have negative impact on the subsequent performance. In this study high quality 4Cr13V corrosion resistant plastic mold steel modules with a large section was produced by a domestic steel plant after improving the forging process. Nonmetallic inclusion， microstructure， size of carbides， mechanical properties in different positions were studied by metallographic， scanning electronic microscope (SEM)， hardness and impact toughness tests， while possible factors were analyzed . The results show that large section 4Cr13V plastic mold steel module has high purity； the spheroidization degree of carbides at the edge part is the best， the closer to the center， the larger size carbides can be observed. Moreover， the presence of these large size carbides has some adverse effect on the mechanical properties， which is the main cause of the performance difference between the edge and the center position.
		2015 Vol. 50 (7): 92-99 [Abstract] ( 1058 ) [HTML 0KB] [PDF 0KB] ( 63 )

	100	WU Si，，LI Xiu-cheng，ZHANG Juan，SHANG Cheng-jia
		Influence of Nb micro-alloying on austenite nucleation and growth in high speed railway wheels steel
		In allusion to high speed railway steel wheel， this papaer studied the influence of Nb micro-alloying on reverse transformation of ferrite and pearlite mocro-structure， whose precursor is ferrite and pearlite. The results indicated that the reverse transformation of ferrite and pearlite was controlled by carbon atomic diffusion. The austenite preferentially nucleated at the interface of α/Fe3C in pearlite and grew up faster in parallel with the direction of pearlite lamellae than perpendicular to that. The Nb micro-alloyed medium carbon steel with refined pearlite colonies could increase the nucleation rate of austenite and obtain smaller size austenite grains . The crystal mixture temperature of wheel steel with Nb is 80 ℃ higher than that without Nb. Nb micro-alloying could expand the temperature range of austenite reheat. Thermal-Calc calculation and TEM observation indicated that Nb existed in the form of precipitates in railway wheel steels. Precipitation pinning contributes to refine the austenite grain and postpone crystal mixture is the main mechanism of Nb-alloying in railway wheel steels.
		2015 Vol. 50 (7): 100-104 [Abstract] ( 1111 ) [HTML 0KB] [PDF 0KB] ( 60 )

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