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	2014 Vol. 49 No. 10
	Published: 2014-10-15

	1	ZENG Jia-qing, PAN Yi-fang, WANG Li-ping, LIANG Mei, LI Shu-qing
		Further Understanding of Theories and Practice for Low-Cost and High-Efficient Clean Steel Production by Combined Blowing Converter
		Based on review of development about the processes of clean steel production at home and abroad, the technical principles and their necessities of low-cost and high-efficient clean steel production by combined blowing converter were analyzed, including low-temperature dephosphorization by combined blowing converter, the coordination of top and bottom blowing, the continuous implementation of the new process, the high-efficient oxygen blowing in decarburization period, and the reutilization method of slag been rich in P2O5, and so on. In order to obtain good implementation effect of the new process, the comprehensive and objective technical key points of the new process must be known well, and also the solid foundation of technical and management would be needed. According to related problems occurred in practice, the improved proposals were put forward.
		2014 Vol. 49 (10): 1-6 [Abstract] ( 1361 ) [HTML 0KB] [PDF 0KB] ( 47 )

	7	LIU Cheng-song, LI Jing-she, YANG Shu-feng, GAO Xiang-zhou, MA Bo
		Experimental and Mechanism on Pellet-Making of Magnetic Iron Ore Concentrate in Han-Xing Area
		Based on the experiment for pelletizing in production, influence of bentonite proportion, water proportion and damp milling time on green ball properties in pellet-making of a magnetic iron ore concentrate in Han-xing area were investigated, which the optimum conditions were 2.0%, 8.5%-9.0% and 6 min respectively. Moreover, the effect of pre-heating temperature, pre-heating time, roasting temperature and roasting time on consolidation properties of the pellet was studied based on experiments in laboratory and the microstructure of pellet and consolidation mechanism were analyzed by optical microscope. Results show that the suitable pre-heating temperature and time were 880－920 ℃ and 20 min; the suitable roasting temperature and time were 1250 ℃ and 20 min.
		2014 Vol. 49 (10): 7-12 [Abstract] ( 1372 ) [HTML 0KB] [PDF 0KB] ( 67 )

	13	GUO De-yong, ZHANG Jie, LU De-chang, BAI Chen-guang, LIU Xiang-hui, Lü Xue-wei
		Effect of [R] on Viscosity of CaO-SiO2-Al2O3-MgO-TiO2 in Blast Furnace Slags
		More and more Australian iron ore had been consumed in Chongqing Iron and Steel Group Co., Ltd. in recent years and consequently the slag property had been changed, especially the increased value of Al2O3 in slag has defect on slag fluidity.The viscosity in CaO-SiO2-Al2O3-MgO-TiO2 slag that add chemical agents to industrial slags has been measured at different [R] and the mass percent of Al2O3, MgO, TiO2 were fixed at 12%, 8%, 5% respectively. In addition the slags viscosity at different cotent of TiO2 has been measured. The results show that moderate content of TiO2 can reduce viscosity, and viscosity decreasing with basicity increasing at current scope, the viscosity decreasing trend flattens when basicity exceed 1.35.
		2014 Vol. 49 (10): 13-17 [Abstract] ( 2025 ) [HTML 0KB] [PDF 0KB] ( 57 )

	18	WANG Xiao-feng, TANG Fu-ping, LI Zhen, LIN Yang, ZHANG Yue, WANG Jun
		Technology of Inducing Dispersed In-Situ Phase by Composite Ball Explosion Reaction
		Decreasing the total oxygen content and the inclusion removal is the key technique to produce the high purity steel.A novel cleanness steel production technology due to the dispersed in-situ phase induced by the composite ball explosion reaction has been put forward. A composite ball with this function has been designed and prepared using a laboratory model batch type balling disc and the industrial experimental investigations have also been carried out. The results indicate that this novel technique is a low-cost and high efficiency cleanness steel production method, which can realize quick slag forming, fast dephosphorization and fine inclusion removal. Temperature drop during transferring is small. The heat-up rate during LF has been increased for more than 2 ℃/min and the refining period has been shorten for 3－8 min. Average total oxygen in the as-cast slab can be decreased from 14.2×10-6 to 9.69×10-6. The lowest phosphorous in the casting bland can approach to 30×10-6 after its treatment.
		2014 Vol. 49 (10): 18-23 [Abstract] ( 1228 ) [HTML 0KB] [PDF 0KB] ( 58 )

	24	CHEN Yu-xin, XU Dong-li, WANG Li, HUANG Jun, XUE Yong-qiang
		Theoretical Analysis for Splashing in Iron Ladle of Mechanical Stirring Desulphurization Process
		KR processes desulphurization more efficiently and less consumptivey with mechanical stirring. Hot metal splashes from KR ladle without blow-in gases. An example of CO splashing in KR process is involved, trying to find out why and how it happens. It is revealed that the residual iron and ferrite will turn into ferrous oxide after long-term hot baking. Ferrous oxide would be melt or turn into liquid fayalite after reacting with silicon in hot metal. The drops would float up and react with carbon in hot metal at some depth, generating carbon oxide. These reactions would be fastened after stirring, resulting in splashing. Higher temperature, more carbon and less silicon in hot iron, more heavily it splashes. To preventing splashing, time upper limit should be carried out when baking. “Belch” or “surface rolling” is a significant signal before splashing, pay more attention or stop operation.
		2014 Vol. 49 (10): 24-29 [Abstract] ( 1191 ) [HTML 0KB] [PDF 0KB] ( 87 )

	30	JIAO Yu-li
		High Carbon Technology With Single Slag Process in Combined Blowing Converter
		In order to achieve [w(C)＞0.4%] and [w(P)＜0.02%] at tapping, a single-slag decarburization process at the condition of 1 050 kg/t consumed by hot metal and [w(P)=0.15%] was developed. Lower dephosphorization, splashing and difficulty of pulling carbon time is the most difficult point of the process. Therefore, the adjustment test on the converter operation taking place, oxygen pressure, the flow of bottom blowing and the end control are taken. Experimental results indicate that splashing can be efficiently controlled while improving the dephosphorization efficiency with suitable bottom blowing pressure. The carbon percentage increased to more than 90% by establishing high carbon tapping end-point judgment model. After the implementation of the process, BOF end-point free oxygen is maintained at about 100×10-6.
		2014 Vol. 49 (10): 30-33 [Abstract] ( 1032 ) [HTML 0KB] [PDF 0KB] ( 50 )

	34	CHEN Yang,, ZHONG Guang, YAO Jun, NING Shu-guang, LI Zhen, XIE Chang-chuan
		Development and Application of Two-Strand Slab Continuous Caster Mold Taper Dynamic Balance Technology ^Hot!
		Shandong fulun Steel has built the first two-strand slab continuous caster for producing products with different sections. The functions and equipment structure together with the hydraulic and electric control principle of taper dynamic balance technology of the slab continuous caster were presented. The quantitative relationship of pressure reduction on mold broadside, disc spring pre-tightening force and the static pressure of liquid steel in the process of casting was derived. From the application of this technology on October 9, 2013 to November 12, 2013, 41 860 t slab has been cumulatively casted, 14 heats on average were continuously cast for every casting sequence, and the maximum casting speed is 1.4 m/min. In the meantime, no taper change happens and the left and right tapers are always kept in ±0.5 mm. The internal and external qualities of slab are excellent, and actual application effect is satisfactory.
		2014 Vol. 49 (10): 34-39 [Abstract] ( 1584 ) [HTML 0KB] [PDF 0KB] ( 93 )

	41	LIANG Xun-guo
		Preset Model of Bending Force for Six-High Tandem Cold Rolling Mill
		An elastic deformation model for the roll stack of six-high cold rolling mill was built based on the influence function method. The factors affecting the optimum bending force such as specific rolling force and intermediate roll shifting were analyzed theoretically, and a more reasonable bending force preset model was established. Meanwhile, a simplified preset model of intermediate roll bending force was built according to the relationship between the intermediate roll bending force and the work roll bending force, which can reduce the difficulty of commissioning and maintenance. On-site application results show that the preset model has high precision and only 5.25% of the deviation between the preset and the measured bending forces was out of the range of ±20%.
		2014 Vol. 49 (10): 41-43 [Abstract] ( 1427 ) [HTML 0KB] [PDF 0KB] ( 33 )

	44	LI You-he, HAO Zhen-yu, ZHANG Long, HUANG Zhen-yi, CAO Yan, ZHANG Xiao-feng
		Surface Quality Control for Hot Rolling SAE4137 Bar Based on Processing Map Method ^Hot!
		Isothermal compression experiments of SAE4137 steel were performed on an MMS-200 thermal-mechanical simulator at the strain rate ranging from 0.1 to 10 s-1, the deformation temperature ranging from 900 to 1 150 ℃ and the maximum height reduction of 70%. On the basis of the experimental results, dynamic material model and Murthy flow instability criterion, the processing maps for SAE4137 steel were constructed at the different true strains. The stable regions, flow instability regions and the recommended processing region were obtained for SAE4137 steel. Based on the analysis of microstructure and the practical condition of making intermediate billet (215 mm×235 mm) into [?]150 mm large bar through 4-pass finishing rolling in Nanjing Steel, the surface defect and its position of SAE4137 bar in production process were predicted.
		2014 Vol. 49 (10): 44-50 [Abstract] ( 1708 ) [HTML 0KB] [PDF 0KB] ( 70 )

	51	ZHANG Peng,,, CHENG Shu-sen,,, CHANG Chong-ming, LI Ji-peng, ZHENG Yue-qiang
		Temperature Field of Hot Rolled Strip During Laminar Cooling Process
		A three-dimensional model was established for CSP hot rolling process to simulate the strip temperature field during laminar cooling from impinging water jets in run-out table (ROT) process. The deviation between simulated and measured coiling temperatures was 9.5 ℃ for 3 mm thick strip, and the relative error was 1.42%, which indicated that the model and assumptions were reasonable. The effect of diameter of upper nozzles on strip temperature was investigated. There were two different cooling regions along the width direction on the upper surface: one was under the nozzle, and the laminar region and impingement region were alternately distributed; the other was the laminar region between nozzles during the laminar cooling process. The results showed that there was an optimum nozzle diameter under the condition of constant cooling water flow rate, making the temperature along the width direction distributed more uniformly.When the water jet speed remained the same, increasing diameter of the nozzle was advantageous to the uniform temperature distribution along the width direction, but increased the water flow rate and reduced the strip coiling temperature.
		2014 Vol. 49 (10): 51-57 [Abstract] ( 1462 ) [HTML 0KB] [PDF 0KB] ( 61 )

	58	LI Yong-hua, SHAO Yuan-jing, HE Li-hong
		Analysis of Pickling Process Mechanism of Hot-Rolled Austenitic Stainless Steel Strip
		The formation mechanism of surface oxide scale, the mechanism of the effect of annealing on surface oxide scale, and the pickling process mechanism of hot-rolled austenitic stainless steel strip were analyzed in details, respectively. The results shows that the outer layer of oxide scale is mainly composed of iron oxide and the inner layer is alternatively distributed Cr2O3 and FeCr2O4. After annealing, the oxide scale becomes loose and porous and is easy to fall off. Meanwhile, the chromium depleted layer becomes thicker. All these make the pickling of strip much more easily. In addition, the surface oxide scale is primarily removed by mechanical stripping during pickling. The analysis of the results has certain theoretical significance for the improvement of hot-rolled austenitic stainless steel strip pickling technology.
		2014 Vol. 49 (10): 58-61 [Abstract] ( 1278 ) [HTML 0KB] [PDF 0KB] ( 68 )

	62	ZHOU Jia-lin， SHI Mi， ZHANG Pei-yi， YANG Guang-yu， YU Ru， DAI Yuan
		Research on Hot Deformation Behavior of 45 Steel in Low Temperature Region ^Hot!
		The effect of different deformation conditions on the deformation behavior of 45 carbon structural steel at low temperatures was studied using Gleeble-1500 thermal-simulation machine. Experimental results show that peak stress increased with the decreasing of deformation temperature and the increasing of strain rate; dynamical recovery occurred when strain rate [ε]≥0.01 s-1, and deformation temperature [t]＜500 ℃; dynamical recrystallization occurred when strain rate [ε]≤1 s-1, and deformation temperature [t]≥500 ℃. The flow stress models at work harding-dynamical recovery stage and dynamical recrystallization stage were both established based on the Sellars-Tegart equation. The parameters in these models were fitted according to the experimental results. The stress-stain curves of both dynamic recovery style and dynamic recrystallization style were successfully predicted. The straightening force at low temperature of 45 steel plates in the industrial trial was predicted, and the results matched well with the measured values.
		2014 Vol. 49 (10): 62-65 [Abstract] ( 1572 ) [HTML 0KB] [PDF 0KB] ( 51 )

	66	GUO Hui-ying, ZHANG Yu, XU Hong-mei, WANG Yin-bai
		Development of Low Alloy Heat Resisting Welding Wire
		The continuous cooling transformation (CCT) kinetics in the designed thermo mechanical processing conditions was investigated for 1.25Cr-0.5Mo steel employing a Gleeble-3800 thermo mechanical simulator, and plant trial of the wire rod was conducted in the high speed wire rod production line. The CCT experimental results suggest that the sample under deformation temperatures of both 950 and 1 000 ℃ both produced a microstructure of ferrite (F) and martensite (M), and the fraction and size of M decreased with the deformation temperature and cooling rate. The optimization of rolling schedule at industrial facilities showed that a combination of finishing rolling temperature at 950 ℃, the spinning temperature at 870-890 ℃ and the cooling rate at 0.3-0.5 ℃/s produced a welding wire with a microstructure of F+M and tensile strength below 830 MPa. Fracture of wire doesn’t occur during the drawing process which was smooth.
		2014 Vol. 49 (10): 66-70 [Abstract] ( 1111 ) [HTML 0KB] [PDF 0KB] ( 42 )

	71	ZHAO Li-ping, QIN Xiang-dou, ZHANG Hui-min, HE Jian-xin
		Corrosion Resistance Research of Low-Nickel Cr-Mn-N Stainless Steel Containing Rare Earth Element La
		Low-nickel Cr-Mn-N stainless steel with different content of rare earth La element was the research object, and the electrochemical behavior was studied by electrochemical impedance spectrum and polarization curve in the cyclic immersion corrosion environment. The experimental result shows that rare earth element La can affect the electrode potential of Low-nickel Cr-Mn-N stainless steel. When the content of La element was in the range of 0-0.014%, the amount of rare earth to be added was more, the substrate electrode potential of the stainless steel was higher. When Low-nickel Cr-Mn-N stainless steel contained the 0.004 9% of La element, the corrosion resistance was best in 3.5% NaCl solution for 48 days of simulation of atmospheric corrosion, but the content of La element exceeded a certain range, the corrosion resistance decreased.
		2014 Vol. 49 (10): 71-75 [Abstract] ( 1225 ) [HTML 0KB] [PDF 0KB] ( 48 )

	76	WANG Meng,, WANG Li-ping, LUO Zhi-jun, TONG Qian, SUN Zu-qing, LI Long-fei
		Influence of Cooling Procedure After Transformation-Temperature-Rising on Microstructure and Property of 82B Wires
		The character of microstructure and property in the segregation of 82B wire with three different stelmor control cooling procedures after tansformation-temperature-rising was researched. between 2-10 ℃/s, the cooling rate decreased to 2 ℃/s after transformation of temperature. And for 82B, the kinetics of eutectoid transformation of segregation through thermal simulation in the range of 400-600 ℃ were researched. The longitudinal section segregation microstructure and composition were analyzed by measures such as OM, SEM and EPMA. The thermal simulation results show that the length of martensite segregation bands decreased as holding time increased, and martensite band in the core of wire where the content of elements such as Mn and Cr was higher than matrix because of segregation. Furthermore, Stelmor control cooling experiments in the high speed wire mill confirms that the core of controlling martensite was slow cooling speed procedure in the post-transformation section of cooling line, while the properties of 82B will be optimized.
		2014 Vol. 49 (10): 76-81 [Abstract] ( 1307 ) [HTML 0KB] [PDF 0KB] ( 84 )

	82	WU Nian-chun
		Physical Metallurgical Principles and Mechanical Properties of Fire Induced Strengthening Q420FRE Fire-Resistant Steel
		According to the precipitation characteristics of the nano-sized microalloying second phase during the heating process, a new technical idea of fire induced strengthening fire-resistant steel which was strengthened by precipitation particles at high temperature was proposed. The content of Mo addition can be reduced compared with the traditional fire-resistant steel. The production method to match the fire induced strengthening fire-resistant steel was accelerated cooling following hot rolling, which inhibited the precipitation of microalloying second phase during cooling after hot rolling and obtained low-temperature transformation product. Nb-V-Ti-Mo complex microalloying of fire induced strengthening Q420FRE fire-resistant steel by industrial trial had a microstructure of fine granular bainite. The mechanical properties of industrial trial Q420FRE has reached the requirements of the standard GB/T 28415—2012. Especially, the elongation at room temperature and the low-temperature impact toughness at －40 ℃ were quite excellent. Furthermore, the increment of nano-sized MC phase precipitation hardening between 600～700 ℃ was estimated over 50 MPa in the industrial trial fire induced strengthening Q420FRE fire-resistant steel plates. Simulation tests show that the fire-resistant temperature of industrial trial Q420FRE was close to 650 ℃. After tempering within 3 h at 600 ℃, the industrial trial Q420FRE did not fail. After air cooling, the industrial trial Q420FRE had higher yield strength at room temperature and a secondary fire resistance.
		2014 Vol. 49 (10): 82-88 [Abstract] ( 1101 ) [HTML 0KB] [PDF 0KB] ( 46 )

	89	HU Xiao-xuan,, WANG Rui-zhen, ZHOU Yun, SU Hang
		Influence of Vanadium and Nitrogen Content on Microstructure and Properties of NM400 Wear-Resistant Steel
		The effect of V-N microalloying on microstructure and properties of wear-resistant plate was investigated, with plain low alloy Cr-Mo-B composition and directly quenched (DQ) plus low-temperature tempered process. The results show that the plate without V-N microalloying was with lath martensite microstructure and had the impact energy of 15 J at －20 ℃ and Brinell hardness of 443. Two kinds of V-N microalloying plates with addition of 0.088%V-0.013%N and 0.089%V-0.029%N respectively showed obviously refined lath martensite structure and existing of a small amount of acicular ferrite. Their impact energy at －20 ℃ increased to 30 and 42 J, respectively. Meanwhile, the plate with 0.089%V-0.029%N showed almost the same hardness as the plate without V-N had. During the low temperature deformation in austenite precipitation of fine V (C, N) particles formed could suppress austenite grain growth. The V(N,C) particles precipitated during finish rolling at 860 ℃ and the subsequent relaxation process could promote the formation of acicular ferrites, which played a role in splitting austenite grains and in refinement of martensite microstructure. The plate containing 0.089%V-0.029% N showed the best comprehensive performance.
		2014 Vol. 49 (10): 89-94 [Abstract] ( 1403 ) [HTML 0KB] [PDF 0KB] ( 59 )

	95	LI Kai, WANG Hong, , ZHU Xun, , LIAO Qiang, , WU Jun-jun
		Experiment of Liquid Centrifugal Atomization Properties by Rotary Cup
		Based on the granulation technology for high temperature molten blast furnace slag by rotary cup, visualization experiments were conducted by applying water as the substitute for slag and a rotary cup with diameter of 110mm to investigate the flow mechanism on the rotary cup surface and the formation of liquid ligament at the edge of the rotary cup. The dynamic behaviors of the liquid ligament length and the diameter of ligament head were obtained. The effects of rotary speed, liquid flow rate on diameter distribution of the granulated droplets were discussed. The experimental results indicate that the liquid film on the cup surface formed some heaves along the edge of the cup and formed liquid ligaments along the tangential direction of the rotary cup movement; the ligament length almost linearly increased as time progressed, while the diameter of ligament head approximately kept a constant value. The average diameter of the granulated droplets decreased with the increase of rotary speed and the decrease of the liquid flow rate.
		2014 Vol. 49 (10): 95-99 [Abstract] ( 1490 ) [HTML 0KB] [PDF 0KB] ( 69 )

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