JOURNAL OF IRON AND STEEL RESEARCH INTERNATIONAL

钢铁研究学报(英文版)

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	2016 Vol. 23 No. 10
	Published: 2016-10-15

Metallurgy and Metal Working

	997	Guang-sheng WEI,,Rong ZHU,,Ting CHENG,Fei ZHAO
		Numerical Simulation of Jet Behavior and Impingement Characteristics of Preheating Shrouded Supersonic Jets
		As a novel supersonic jet technology, preheating shrouded supersonic jet was developed to deliver oxygen into molten bath efficiently and affordably. However, there has been limited research on the jet behavior and impingement characteristics of preheating shrouded supersonic jets. Computational fluid dynamics (CFD) models were established to investigate the effects of main and shrouding gas temperatures on the characteristics of flow field and impingement of shrouded supersonic jet. The preheating shrouded supersonic jet behavior was simulated and measured by numerical simulation and jet measurement experiment respectively. The influence of preheating shrouded supersonic jet on gas jet penetration and fluid flow in liquid bath was calculated by the CFD model which was validated against water model experiments. The results show that the uptrend of the potential core length of shrouded supersonic jet would be accelerated with increasing the main and shrouding gas temperatures. Also, preheating supersonic jets demonstrated significant advantages in penetrating and stirring the liquid bath.
		2016 Vol. 23 (10): 997-1006 [Abstract] ( 388 ) [HTML 0KB] [PDF 0KB] ( 44 )

	1007	Qiang-jian GAO,Yan-song SHEN,Xin JIANG,Hai-yan ZHENG,Feng-man SHEN,Chang-sheng LIU
		Effect of MgO on Oxidation Process of Fe3O4 in Pellets
		Induration process of oxidized pellets involves the oxidation of Fe3O4 and re-crystallization of Fe2O3. The oxidation process of Fe3O4 is significant for pellets to obtain better ambient strength. Thus, the effect of MgO on oxidation process of Fe3O4 was investigated. The unreacted core model was applied to analyze the oxidizing induration process of pellets. The experimental results show that MgO plays a negative role in the oxidation process of Fe3O4. The oxidation rate of Fe3O4 in MgO-fluxed pellets (95.0% Fe3O4+5.0% MgO) is slower than that in standard acid pellets (100% Fe3O4). The relation between oxidation ratio of Fe3O4 and time was calculated based on the unreacted core model for both MgO-fluxed pellets and standard acid pellets. According to verification experiments, the values calculated by model coincide well with the experimental values. Therefore, the unreacted core model could be applied to describe the oxidizing induration process of pellets.
		2016 Vol. 23 (10): 1007-1011 [Abstract] ( 382 ) [HTML 0KB] [PDF 0KB] ( 22 )

	1012	Jiao LUO,Ying-gang LIU,Miao-quan LI
		Three-dimensional Numerical Simulation and Experimental Analysis of Austenite Grain Growth Behavior in Hot Forging Processes of 300M Steel Large Components
		The microstructure models were integrated into finite element (FE) code, and a three-dimensional (3D) FE analysis on the entire hot forging processes of 300M steel large components was performed to predict the distributions of effective strain, temperature field and austenite grain size. The simulated results show that the finest grains distribute in the maximum effective strain region because large strain induces the occurrence of dynamic recrystallization. However, coarse macro-grains appear in the minimum effective strain region. Then, 300M steel forging test was performed to validate the results of FE simulation, and microstructure observations and quantitative analysis were implemented. The average relative difference between the calculated and experimental austenite grain size is 7.56%, implying that the present microstructure models are reasonable and can be used to analyze the hot forging processes of 300M steel.
		2016 Vol. 23 (10): 1012-1019 [Abstract] ( 565 ) [HTML 0KB] [PDF 0KB] ( 31 )

	1020	Dian-tao ZHANG,,Zhen LI,,Yun-xiang TONG,,Yu-feng ZHENG,,Li LI,
		New Formulas of Shear Strain during Equal-channel Angular Pressing Process with Consideration of Influences of Velocity and Motion Trajectory
		The influences of die parameters on shear strain were investigated by using two-dimensional finite element simulation. New formulas of shear strain were proposed. According to the results of formulas, the shear strain showed a linear dependence on the difference between internal and external fillet radius and the slope was determined by the intersection angle. The simulation results indicated that the velocities of the points from different zones were different in the specimen and the motion trajectories of different points did not follow geometrical laws. The influences of the average velocity and the motion trajectory on shear strain were incorporated in the formula to calculate the shear strain produced during equal-channel angular pressing process. The reliability of simulation results has been partially validated by experiments.
		2016 Vol. 23 (10): 1020-1027 [Abstract] ( 299 ) [HTML 0KB] [PDF 0KB] ( 15 )

	1028	Xiao-qing XU,,Xiao-dong HAO,Shi-guang ZHOU,Chang-sheng LIU,Qi-fu ZHANG
		Model Algorithm Research on Cooling Path Control of Hot-rolled Dual-phase Steel
		With the development of advanced high strength steel, especially for dual-phase steel, the model algorithm for cooling control after hot rolling has to achieve the targeted coiling temperature control at the location of downcoiler whilst maintaining the cooling path control based on strip microstructure along the whole cooling section. A cooling path control algorithm was proposed for the laminar cooling process as a solution to practical difficulties associated with the realization of the thermal cycle during cooling process. The heat conduction equation coupled with the carbon diffusion equation with moving boundary was employed in order to simulate temperature change and phase transformation kinetics, making it possible to observe the temperature field and the phase fraction of the strip in real time. On this basis, an optimization method was utilized for valve settings to ensure the minimum deviations between the predicted and actual cooling path of the strip, taking into account the constraints of the cooling equipment’s specific capacity, cooling line length, etc. Results showed that the model algorithm was able to achieve the online cooling path control for dual-phase steel.
		2016 Vol. 23 (10): 1028-1034 [Abstract] ( 341 ) [HTML 0KB] [PDF 0KB] ( 43 )

	1035	K. CHAKRAVARTY
		Improvement in Production Yield of Hot-rolled Coil by Controlling Process Cobbles
		The yield is dependent upon many factors, such as cobbles, total scrap generation, crop loss and scale loss. It appears that the huge quantity of scale is mainly responsible for the yield loss. However, by the correlation study, it reveals that the number of cobbles is the major contributor to the yield loss. The innovation lies in changing the focus of attacking the real problem by analysing the operating data which was not surfaced earlier. The focus shifted from the furnace to the mill and the cobbles studied through the years deeply. All the analysis proved to be helpful for the future prevention of the similar kind of failure. The internal target of bringing down the number of cobbles per month in single digit was taken. This also helped in improving the maintenance practice and reducing the amount of delays significantly. The yield was improved by 0.93%.
		2016 Vol. 23 (10): 1035-1043 [Abstract] ( 351 ) [HTML 0KB] [PDF 0KB] ( 11 )

Material

	1044	Xiang-jun ZHANG,Fei GAO,Zhen-yu LIU
		Effect of Sn on Corrosion Behavior of Ultra-pure 17 mass% Cr Ferritic Stainless Steels in Sulphuric Acid
		The effect of Sn on corrosion behavior of ferritic stainless steels in 20 mass% H2SO4 was investigated by alternating current and direct current electrochemical methods and gravimetric tests at 25 ℃. The results show that Sn can effectively improve general corrosion resistance of ferritic stainless steels in H2SO4, mainly due to highly raised hydrogen evolution overpotential which is in favour of strong suppression of hydrogen evolution reaction, and inhibitive effect of dissolved Sn2+ on elementary anodic reactions. With increasing Sn content, the better corrosion resistance can be reached. The Electrochemical Impedance Spectroscopy (EIS) includes four time constants and can be perfectly fitted by equivalent circuit: Rs(CdlRct)(QadsRads(RL1(L1(RL2L2)))).
		2016 Vol. 23 (10): 1044-1053 [Abstract] ( 497 ) [HTML 0KB] [PDF 0KB] ( 19 )

	1054	Qiu-han LI,Chi ZHANG,Hu CHEN,Hao CHEN,Zhi-gang YANG
		Microstructural Evolution of a Hypoeutectoid Pearlite Steel under Rolling-sliding Contact Loading
		To study the microstructural evolution of pearlite steel subjected to pure rolling and rolling-sliding contact loading, a hypoeutectoid pearlite steel with composition and microstructure similar to BS11 was designed and twin-disc tests of this pearlite steel were performed to simulate the wheel/rail system. After a series of twin-disc tests, optical microscope (OM) observation, scanning electron microscope (SEM) observation, X-ray diffraction (XRD), and micro-hardness tests were conducted to characterize the microstructure. Under the pure rolling contact condition, a large amount of reticular cracks emerged within 60 μm below the contact surface of the samples after 120000 revolutions. The largest deformation was approximately 200 μm below the contact surface. Under the rolling-sliding contact condition, the nodularization of pearlite within 100 μm below the contact surface was obvious. The microstructure and stress-strain distribution of the area within 2 mm below the contact surface were investigated. The distribution of micro-hardness under the contact surface varied with contact conditions. Finite element method (FEM) was used to simulate the stress-strain distribution. The results of SEM, FEM, and micro-hardness tests indicated that under the pure rolling contact condition, the maximum plastic strain was approximately 200-400 μm below the contact surface. Conversely, under the rolling-sliding contact condition, the maximum plastic strain emerged on the contact surface. Under the pure rolling contact condition, the distribution of micro-hardness was almost identical to that of the equivalent plastic strain. Under the rolling-sliding contact condition, the distribution of micro-hardness was affected by the equivalent plastic strain and tangential stress.
		2016 Vol. 23 (10): 1054-1060 [Abstract] ( 335 ) [HTML 0KB] [PDF 0KB] ( 42 )

	1061	Qiang YU,Chao-fang DONG,Yue-hua FANG,Kui XIAO,Chun-yun GUO,Gang HE,Xiao-gang LI
		Atmospheric Corrosion of Q235 Carbon Steel and Q450 Weathering Steel in Turpan, China
		Q235 carbon steel and Q450 weathering steel were exposed to the hot and dry environment of Turpan, China for three years. The corrosion rates of both steels were calculated and compared. The morphologies of the rust layer products were observed by optical microscopy and scanning electron microscopy. Analyses of the rust layers were performed by X-ray photoelectron spectroscopy, X-ray powder diffraction, and Raman spectroscopy, and analysis results indicate that the compositions of rust are main iron rich oxide such as FeOOH, Fe3O4, and Fe2O3. The iron oxide layer content proportion was calculated through a semi-quantitative algorithm. The resistance elements (Cr, Ni, and Cu) enhanced the resistance properties of the Q450 weathering steel matrix. Moreover, the resistance elements increased the proportion of goethite crystals in the corroded rust layer.
		2016 Vol. 23 (10): 1061-1070 [Abstract] ( 370 ) [HTML 0KB] [PDF 0KB] ( 17 )

	1071	Qi SUN,,Jian WANG,,Hua-bing LI,Yue LI,,Ya-di HU,,Jin-gang BAI,Pei-de HAN,
		Chi Phase after Short-term Aging and Corrosion Behavior in 2205 Duplex Stainless Steel
		Correlation between pitting corrosion behavior and chi (χ) phase formed after a short-term aging (5, 10 and 15 min) at 850 ℃ of 2205 duplex stainless steel (DSS) was investigated using potentiodynamic polarization tests, optical microscopy, and scanning electron microscopy equipped with energy-dispersive spectrum system. Results showed that after aging for 5 min, the χ phase initially precipitated at ferrite grain boundaries, developed and then became linked with prolonging aging time. The χ phase was rich in Cr and Mo, resulting in formation of depleted zones nearby. The χ phase could reduce corrosion resistance of DSS and slightly influence its stability, but the specimens still displayed the capacity for repassivation. Some lines of evidence showed that stable pitting corrosion initiated at the boundaries of precipitates. The χ phase was selectively corroded during the first stage of corrosion and then the depleted zones nearby were attacked. In addition, the grain size and volume of precipitates also affected pit nucleation and progress, and suitable size and distribution of χ phase could aggravate pit initiation at precipitate boundaries. The χ phase with considerably low volume fraction and small size was not sensitive position for pit initiation.
		2016 Vol. 23 (10): 1071-1079 [Abstract] ( 344 ) [HTML 0KB] [PDF 0KB] ( 15 )

	1080	Hai-jun WANG,Bing FU,,Li XIANG,Zhe RONG,Sheng-tao QIU
		Effect of Nitrogen Content on Primary Recrystallization Behavior and Magnetic Property of Hi-B Steel
		The effect of nitrogen content on primary recrystallization microstructure, texture and magnetic property of Hi-B steel was studied by means of optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). When nitrogen content increased gradually from 0.0055% to 0.0310%, the primary grain size and variation coefficient of nitrided sheet reduced from 26.85 μm, 0.590 to 18.87 μm, 0.525-0.565, respectively. Meanwhile, the primary recrystallization texture style of nitrided sheet was nearly identical to the texture style of decarburized sheet before nitriding treatment, but exhibiting a certain change on texture intensity. The variation of average magnetic induction value (B8) and core loss value (P17/50) were manifested to be M-shaped and W-shaped curves, respectively. When nitrogen content reached 0.0160%, the best value of the average magnetic property of the final product was obtained as follows: the B8 and P17/50 were 1.921 T and 0.968 W/kg, respectively. Meanwhile, the best performance, B8 and P17/50, of single sheet was 1.964 T and 0.854 W/kg.
		2016 Vol. 23 (10): 1080-1085 [Abstract] ( 355 ) [HTML 0KB] [PDF 0KB] ( 46 )

	1086	Feng LU,,Guang-ping CHENG,Feng CHAI,Tao PAN,Zhong-ran SHI,Hang SU,Cai-fu YANG
		Effect of Heat Input on Cleavage Crack Initiation of Simulated Coarse Grain Heat-affected Zone in Microalloyed Offshore Platform Steel
		The combined effects of martensite-austenite (MA) constituent and pearlite colony on cleavage crack initiation in the simulated coarse-grained heat-affected zone (CGHAZ) of V-N-Ti microalloyed offshore platform steel under different heat inputs were investigated. The results of welding simulation, instrumented impact test, and quantitative analysis indicated that the size of the MA constituent decreased with the increase in cooling time, and by contrast, the size of the pearlite colony increased. According to Griffith theory, the critical sizes of cleavage microcracks were calculated. With the increase of cooling time, the calculated microcrack size could be characterized by the size of the MA constituent first, and then fitted with the size of the pearlite colony. Moreover, the calculated microcrack size variation was opposite to the microcrack initiation energy. This phenomenon is probably due to the combined effects of the MA constituent and pearlite colony with increasing the cooling time of the specimen’s temperature from 800 to 500 ℃.
		2016 Vol. 23 (10): 1086-1095 [Abstract] ( 363 ) [HTML 0KB] [PDF 0KB] ( 18 )

	1096	Di WU,,Wan-tang FU,Yong LI,Chun-xu WANG,Jing-lin TANG
		Phase Stability, Elastic, Thermo-physical and Electronic Properties of Hexa-(Mo,Cr,W)2C from First-principles Calculations
		Phase stability, elastic properties, thermo-physical properties, as well as electronic properties of hexa-(Mo,Cr,W)2C carbides were investigated by first-principles calculations. The results indicated that the Mo8C4, Mo7Cr1C4, Mo7W1C4, Mo6W2C4, and Mo6W1Cr1C4 are stable and the stability follows the sequence: Mo6W1Cr1C4＞Mo7W1C4＞Mo7Cr1C4＞Mo6W2C4＞Mo8C4. Mo6W1Cr1C4 shows the highest stability, deformation resistance and hardness. G/B (shear modulus/bulk modulus) and Poisson’s ratio of the stable hexa-(Mo,Cr,W)2C are all larger than 1.75 and 0.26, respectively, which indicates that they are all brittle. The anisotropies are mainly due to the different Vogit shear modulus/Reuss shear modulus; the mechanical anisotropy of Mo7Cr1C4 is the largest, and that of Mo8C4 is the smallest. Moreover, the obtained Debye temperature ΘD and heat capacity Cp indicate that Mo6W2C4 possesses the best thermal conductivity (ΘD=497.72 K), while Mo7Cr1C4 and Mo6W2C4 possess the largest heat capacity when the temperature is in the range of 0-10 K and larger than 10 K, respectively. From the electronic property analysis, the doped Cr and W atoms can not only participate in orbitals hybridization themselves but also enhance the orbitals hybridization between Mo and C atoms, which can reinforce the interatomic interactions.
		2016 Vol. 23 (10): 1096-1103 [Abstract] ( 307 ) [HTML 0KB] [PDF 0KB] ( 15 )

	1104	Xiao-pei WANG,Yong-qiang ZHANG,Jian-bin JU,Jian-qiang ZHANG,Jian-wei YANG
		Characteristics of Welding Crack Defects and Failure Mode in Resistance Spot Welding of DP780 Steel
		The mechanical properties of welded joints in resistance spot welding of DP780 steel were tested, and three different types of welding cracks in welded joints were investigated by optical microscopy, scanning electron microscopy and electron back-scattered diffraction. Finally, the failure mode of the welded joints in shear tensile test was discussed. It is found the shear tensile strength of welded joints can be greatly improved by adding preheating current or tempering current. The surface crack in welded joint is intergranular fracture, while the inner crack in welded joint is transgranular fracture, and the surface crack on the edge of the electrode imprint can be improved by adding preheating current or tempering current. The traditional failure mode criterion advised by American Welding Society is no longer suitable for DP780 spot welds and the critical nugget size suggested by Pouranvari is overestimated.
		2016 Vol. 23 (10): 1104-1110 [Abstract] ( 351 ) [HTML 0KB] [PDF 0KB] ( 5 )

	1111	Min LIU,,Wen-jie ZHENG,Jin-zhong XIANG,Zhi-gang SONG,En-xiang PU,,Han FENG
		Grain Growth Behavior of Inconel 625 Superalloy
		The grain growth (GG) behavior of Inconel 625 superalloy was studied in the temperature range of 900-1250 ℃ and holding time range of 10-80 min. Microstructures of the alloy were characterized by optical metallography, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Grains grew obviously with either increasing temperature or extending holding time at temperatures above 1050 ℃. However, at temperatures lower than 1050 ℃, the GG was sluggish due to the pinning effect of carbide particles on grain boundary (GB). Threshold temperature for transition from mixed grain structure to uniform one was considered to be around 1100 ℃. Once the temperatures surpassed 1200 ℃，an instant increase in the grain size occurred showing no dependence on holding time. TEM analysis showed that the dominant second phase formed heterogeneously on the GB was M6C, which significantly impeded grain growth. On the basis of experimental data, the mathematical model of GG was established, which can describe GG behavior of Inconel 625 alloy during solution treatment (ST) at 1100-1250 ℃. The activation energy for GG of Inconel 625 alloy was 207.3 kJ, which suggested that the GG of Inconel 625 alloy was controlled by the process of GB diffusion.
		2016 Vol. 23 (10): 1111-1118 [Abstract] ( 426 ) [HTML 0KB] [PDF 0KB] ( 32 )

	1119	Halil Ibrahim KURT,Murat ODUNCUOGLU,Ramazan ASMATULU
		Wear Behavior of Aluminum Matrix Hybrid Composites Fabricated through Friction Stir Welding Process
		Effects of friction stir processing (FSP) parameters and reinforcements on the wear behavior of 6061-T6 based hybrid composites were investigated. A mathematical formulation was derived to calculate the wear volume loss of the composites. The experimental results were contrasted with the results of the proposed model. The influences of sliding distance, tool traverse and rotational speeds, as well as graphite (Gr) and titanium carbide (TiC) volume fractions on the wear volume loss of the composites were also investigated using the prepared formulation. The results demonstrated that the wear volume loss of the composites significantly increased with increasing sliding distance, tool traverse speed, and rotational speed; while the wear volume loss decreased with increasing volume fraction of the reinforcements. A minimum wear volume loss for the hybrid composites with complex reinforcements was specified at the inclusion ratio of 50% TiC+50% Al2O3 because of improved lubricant ability, as well as resistance to brittleness and wear. New possibilities to develop wear-resistant aluminum-based composites for different industrial applications were proposed.
		2016 Vol. 23 (10): 1119-1126 [Abstract] ( 328 ) [HTML 0KB] [PDF 0KB] ( 19 )

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