2015年, 第22卷, 第8期　刊出日期：2015-08-15

  

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Review
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  Progress in the Research and Manufacture of GH4169 Alloy

  Jin-hui DU,Xu-dong LU,Qun DENG,Zhong-nan BI

  中国钢铁期刊网. 2015, 22(8): 657-663.

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  GH4169 alloy has been widely used in fields such as aviation,aerospace,and petrochemical,because of its excellent combination of mechanical and processing properties. These properties include good high-temperature strength,excellent creep and fatigue resistance,and good processing and welding performance. The requirement for high performance,high reliability,and long service life of modern engines has led to the incentive to develop GH4169 alloys with improved performance,such as increased temperature-bearing capacity,improved creep endurance,and better fatigue resistance. Advances during the past thirty years in ba-sic research and industrial technology related to GH4169 alloy were systematically summarized,including advances in alloy modi-fication,melting process optimization,and hot deformation technology.
Metallurgy and Metal Working
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  A 2.5-dimensional Analytical Model of Cold Leveling for Plates with Transverse Wave Defects

  Wei-hua CHEN,Juan LIU,Zhen-shan CUI,Ying-jie WANG,Ying-rui WANG

  中国钢铁期刊网. 2015, 22(8): 664-671.

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  Waves occurring in cold-rolled plates or sheets can be divided into longitudinal and transverse waves. Classical leveling theories merely solve the problem of longitudinal waves,while no well accepted method can be employed for transverse waves. In order to investigate the essential deformation law of leveling for plates with transverse waves,a 2.5-dimensional (2.5-D) analytical approach was proposed. In this model,the plate was transversely divided into some strips with equal width; the strips are consid-ered to be in the state of plane strain and every group of adjacent strips are assumed to be deformation compatible under stress. After calculating,the bending deformation of each strip and the leveling effect of overall plate were obtained by comprehensive consideration of various strips along with the width. Bending of roller is a main approach to eliminate the transverse waves,which is widely accepted by the industry,but the essential effect of bending of roller on the deformation of plates and the calculation of bending of roller are unknown. According to the 2.5-D analytical model,it can be found that,for plates,it is neutral plane offsetting and middle plane elongation or contraction under inner stress that can effectively improve plate shape. Taking double side waves as an example,the appropriate values of bending of roller were obtained by the 2.5-D analytical model related to different initial unevenness,which was applicable to the current on-line adjusting of bending of roller in rolling industry.
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  Comprehensive Utilization of Ludwigite Ore Based on Metallizing Reduction and Magnetic Separation

  Xiao-jiao FU,Jia-qi ZHAO,Shuang-yin CHEN,Zheng-gen LIU,Tong-lai GUO,Man-sheng CHU

  中国钢铁期刊网. 2015, 22(8): 672-680.

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  With the aim of high-efficiency utilization of Dandong ludwigite ore,a new process of metallizing reduction and mag-netic separation was proposed,and the effects of reduction temperature,reduction time,carbon ratio,ore size and coal size on the efficiency of the process were investigated in details,and relevant mechanisms were elucidated by SEM and EDS. The optimum technological parameters for metallizing reduction and magnetic separation on ludwigite ore were obtained as reduction tempera-ture of 1 250 °C,reduction time of 60 min,carbon ratio of 1.4,ore size of 0.5?.0 mm,and coal size of 0.5?.5 mm. After adopting the optimum parameters,the iron content and recovery ratio of iron in magnetic substance are 87.78% and 88.02%,respectively,while the recovery ratios of boron,magnesium and silicon in non-magnetic substance are 88.86%,94.60% and 98.66%,respec-tively. After metallizing reduction and magnetic separation,valuable elements of ludwigite ore could be separated and utilized in subsequent steelmaking process and hydrometallurgy process.
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  A Green Mixed Integer Linear Programming Model for Optimization of Byproduct Gases in Iron and Steel Industry

  Hai-ning KONG

  中国钢铁期刊网. 2015, 22(8): 681-685.

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  Byproduct gas is an important secondary energy in iron and steel industry,and its optimization is vital to cost reduction. With the development of iron and steel industry to be more eco-friendly,it is necessary to construct an integrated optimized system,taking economics,energy consumption and environment into consideration. Therefore,the environmental cost caused by pollutants discharge should be factored in total cost when optimizing byproduct gas distribution. A green mixed integer linear programming (MILP) model for the optimization of byproduct gases was established to reduce total cost,including both operation cost and en-vironmental cost. The operation cost included penalty for gas deviation,costs of fuel and water consumption,holder booster trip penalty,and so forth; while the environmental cost consists of penalties for both direct and indirect pollutants discharge. Case study showed that,compared with previous model,the proposed one brought an optimum solution and 2.2% of the total cost could be reduced.
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  Orthogonal Experiments on Direct Reduction of Carbon-bearing Pellets of Bayer Red Mud

  Dun-cheng FAN,Wen NI,Ai-yun YAN,Jian-yue WANG,Wei-hua CUI

  中国钢铁期刊网. 2015, 22(8): 686-693.

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  To recycle residual iron efficiently in Bayer red mud,three-factor three-level orthogonal experiments on carbon-bearing pellets of Bayer red mud were conducted on the basis of their characteristics. The influences of CaO dosage,temperature and roast-ing time on total iron content and iron recovery of reduced iron powder were studied. Results showed that these factors slightly influenced iron recovery,but significantly influenced total iron content. The principal factor influencing total iron content was CaO dosage,followed by temperature and roasting time. An increase in CaO dosage could decrease total iron content,whereas an increase in temperature and an extension of roasting time could improve total iron content. The reduced iron powder with total iron content of 88.41% and iron recovery rate of 97.97% can be obtained under the optimal conditions of temperature of 1 275 °C,roasting time of 60 min and CaO dosage of 7.5%. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses of the reduced pellets showed that iron minerals in red mud were almost completely reduced to metallic iron. The principal factor influencing the total iron content of reduced iron powder was the grain size of metallic iron particles. An increase in CaO dosage hindered the growth of metallic iron particles,whereas an increase in temperature and an extension of roasting time could neutralise the effect of CaO dosage. Therefore,CaO dosage should be decreased when iron minerals in red mud can be adequately reduced into metallic iron.
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  Hot Rolled Strip Re-reddening Temperature Changing Law during Ultra-fast Cooling

  Lian-yun JIANG,Chun-jiang ZHAO,Jian-hui SHI,Guo YUAN,Xue-qiang WANG,Qing-xue HUANG

  中国钢铁期刊网. 2015, 22(8): 694-702.

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  Temperature deviation between surface and the center of hot rolled strip is formed during ultra-fast cooling (UFC). Sur-face temperature will rise when temperature deviation goes up to an extent,and strip re-reddening phenomenon will appear. Strip re-reddening affects the stability of strip microstructure,property and temperature control precision. Thus,it is necessary to conduct research on re-reddening temperature changing law to improve strip property and temperature control precision. Strip tempera-ture trends for various strip thicknesses and ultra-fast cooling rates were obtained by numerical calculation method. Re-reddening temperature,temperature deviation between surface and center,and boundary layer position changing law were obtained. By com-parison,some conclusions were obtained: UFC re-reddening temperature and laminar cooling (LC) re-reddening temperature were linear to ultra-fast cooling rate respectively. Ultra-fast cooling rate affected UFC re-reddening temperature greatly,but it had little effect on LC re-reddening temperature. Equations which were used to calculate UFC re-reddening temperature,LC re-reddening temperature and maximum temperature deviation were obtained. The position of boundary layer stayed in 1/4 strip thickness.
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  Numerical Simulation and Vertical Motion Control of Rolls for Variable Gauge Rolling

  Yu ZHANG,Jian TAN

  中国钢铁期刊网. 2015, 22(8): 703-708.

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  The vertical motion control of the roll was studied in order to improve the accuracy in simulation of variable gauge rolling. The discretization was carried out in the transition zone of TRB according to the principle of volume invariance. Based on this assumption,the formula for time step of vertical motion of rolls was proposed and the time-displacement curve of the vertical motion of rolls was established. In the preliminary simulation,the time-displacement curve was used as an initial method to control the vertical motion of rolls. Based on the simulation result,the formula for vertical velocity of roll in variable gauge rolling was derived from the common rolling principle. According to the formula,the reasonable vertical velocity of rolls in the subsequent simulation was determined. It can accurately control the motion of rolls along the vertical direction. The desired thickness and out-line profile of transition zone were acquired and the formula proved effective by the simulation. Further analysis shows that the difference of thickness in the thick zone and the thin zone of TRB,length of the transition zone of TRB,radius of work rolls and rota-tion speed of rolls have a significant effect on the vertical velocity of rolls.
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  Solidification of High Manganese Steels Using Improved Differential Thermal Analysis Method

  Chang-ling ZHUANG,Jian-hua LIU,Christian BERNHARD,Peter PRESOLY

  中国钢铁期刊网. 2015, 22(8): 709-714.

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  High manganese steels can damage the differential thermal analysis (DTA) instrument due to the manganese evaporation during high temperature experiments. After analyzing the relationship between residual oxygen and manganese evaporation,tanta-lum metal was employed to modify the crucible of DTA,and zirconium getter together with strict gas purification measures were applied to control the volatilization of manganese. By these modifications,problems of thermocouple damage and DTA instrument contamination were successfully resolved. Cobalt samples were adopted to calibrate the accuracy of DTA instruments under the same trial condition of high manganese steel samples,and the detection error of measurements was confirmed to be less than 1 °C. Liquidus and solidus temperatures of high Mn steels were measured by the improved DTA method. It was found that the liquidus temperatures of samples tested by experiments increased linearly with the heating rates. To eliminate the effects of the heating rate,equilibrium liquidus temperature was determined by fitting the liquidus temperatures at different heating rates,and referred as real liquidus temperature. No clear relationship between solidus temperatures and heating rates was found,and the solidus temperature was finally set as the average value of several experimental data.
Material
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  Influence of Marine Aerobic Biofilms on Corrosion of 316L Stainless Steel

  Feng-ling XU,,Ji-zhou DUAN,Cun-guo LIN,Bao-rong HOU

  中国钢铁期刊网. 2015, 22(8): 715-720.

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  The influence of marine aerobic biofilms on the corrosion of 316L stainless steel (SS) in aerated and deaerated seawater was studied by electrochemical impedance spectroscopy (EIS),potentiodynamic polarisation curves,current-potential curves and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS). EIS and SEM-EDS results showed that the aero-bic biofilms inhibited 316L SS corrosion within the test duration. Comparison of results under aerated and deaerated conditions revealed that O2 enhanced the inhibition efficiency of the aerobic biofilms. This result indicated that living cells were necessary for the aerobic biofilms to inhibit the corrosion of 316L SS. Polarization curves indicated that the biofilms mainly inhibited anode ac-tion. Current-potential curves under deaerated conditions showed that electron transfer processes occurred between microorganisms and electrodes. Moreover,316L SS as an electron acceptor was protected from corrosion.
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  Modified Arrhenius-type Constitutive Model and Artificial Neural Network-based Model for Constitutive Relationship of 316LN Stainless Steel during Hot Deformation1

  An HE,Xi-tao WANG,Gan-lin XIE,Xiao-ya YANG,Hai-long ZHANG

  中国钢铁期刊网. 2015, 22(8): 721-729.

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  Hot compression experiments of 316LN stainless steel were carried out on Gleeble-3?500 thermo-simulator in deforma-tion temperature range of 1?223?1?423 K and strain rate range of 0.001?1 s-1. The flow behavior was investigated to evaluate the workability and optimize the hot forging process of 316LN stainless steel pipes. Constitutive relationship of 316LN stainless steel was comparatively studied by a modified Arrhenius-type analytical constitutive model considering the effect of strain and by an ar-tificial neural network model. The accuracy and effectiveness of two models were respectively quantified by the correlation coeffi-cient and absolute average relative error. The results show that both models have high reliabilities and could meet the requirements of engineering calculation. Compared with the analytical constitutive model,the artificial neural network model has a relatively higher predictability and is easier to work in cooperation with finite element analysis software.
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  Elemental Quantitative Distribution and Statistical Analysis on Cross Section of Stainless Steel Sheet by Laser Ablation Inductively Coupled Plasma Mass Spectrometry

  Qian-hua LUO,Hai-zhou WANG

  中国钢铁期刊网. 2015, 22(8): 730-737.

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  An innovative application of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) technique in illustrating elemental distributions on stainless steel sheets was presented. The technique proved to be a systematic and accurate ap-proach in producing visual images or maps of elemental distributions at cross-sectional surface of a stainless steel sheet. Two stain-less steel sheets served as research objects: 3 mm×1 300 mm stainless steel hot-rolled plate and 1 mm×1 260 mm cold-rolled plate. The cross-sectional surfaces of the two samples at 1/4 position along the width direction were scanned (raster area -44 mm2 and 11 mm2) with a focused laser beam (wavelength 213 nm,diameter of laser crater 100 μ,and laser power 1.6 mJ) in a laser abla-tion chamber. The laser ablation system was coupled to a quadrupole ICP-MS,which made the detection of ion intensities of 27Al+,44Ca+,47Ti+,55Mn+ and 56Fe+ within an area of interest possible. One-dimensional (1D) content line distribution maps and two-dimensional (2D) contour maps for specific positions or areas were plotted to indicate the element distribution of a target area with high accuracy. Statistic method was used to analyze the acquired data by calculating median contents,maximum segregation,sta-tistic segregation and content-frequency distribution.
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  Tensile Behavior of the Second Generation Single Crystal Superalloy DD6

  Zhen-xue SHI,Shi-zhong LIU,Jian YU,Jia-rong LI

  中国钢铁期刊网. 2015, 22(8): 738-742.

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  Tensile properties of the second generation single crystal superalloy DD6 were investigated from 20 °C to 100 °C. Microstructure evolution and fracture mechanism were examined by scanning electron microscopy (SEM) and transmission elec-tron microscopy (TEM). The results show that the tensile strength decreases slightly with increasing temperature from 20 °C to 400 °C. The tensile strength of the alloy increases with the increase of temperature from 400 °C to 800 °C. Above 800 °C,the yield strength of the alloy decreases greatly with increasing temperature. The elongation and contraction of area almost present opposite tendency in contrast to changes of the tensile strength. At lower and intermediate temperature (from 20 °C to 850 °C),the tensile fracture mechanism shows quasi-cleavage mode,while at high temperature (980 °C and 1?100 °C),it is dimple mode. The γ′ precipitate morphology still maintains cubic after tensile fracture at lower and intermediate temperature. The γ′ phase changes into rectangular solid at high temperature. The γ′ phase is sheared by anti-phase boundary (APB) or stacking faults at lower and intermediate temperature. At high temperature,dislocations overcome γ′ through by-passing mechanism.
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  Prediction of Nitrogen Diffusivity in α-ferrite Based on Thermodynamics

  Jae-gil JUNG,Seok-jae LEE

  中国钢铁期刊网. 2015, 22(8): 743-745.

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  A thermodynamic based equation to predict the diffusivity of nitrogen in αferrite was investigated in consideration of the equilibrium nitrogen concentration. The temperature-dependent jump distance calculated from the lattice parameter of ferrite was used to derive the frequency factor as a function of temperature. The calculation accuracy for nitrogen diffusivity using the proposed thermodynamic based equation was improved by comparing the calculation results using previous empirical equations based on Arrhenius type relationship with measured diffusivity of nitrogen for αferrite at different temperatures.
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  Electrochemical Behavior and Microstructure of Recyclable Aluminium-magmesium Alloy Hot-dip Coating Deposited on Low Carbon Steel Substrates

  Panomkorn KWAKHONG,pichart ARTNASEAW,haiyaput KRUEHONG

  中国钢铁期刊网. 2015, 22(8): 746-751.

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  With the abundance and good corrosion resistance of aluminium,hot-dip technique was used to prepare the recycled Al with 8.2 mass% Mg alloy coating on low carbon steel substrates. Electrochemical behavior of this coating was investigated by an-odic polarization and open circuit potential measurement. Its microstructure and composition were observed by scanning electron microscope and energy-dispersive X-ray spectrometry,respectively. The long lasting corrosion performance of coated steels was in-vestigated under the salt fog spray test. From anodic polarization curves and open circuit potential,recycled Al with 8.2 mass% Mg coating performed adequate sacrificial ability. At 0.40 V,current density of recycled Al with 8.2 mass% Mg alloy coating was about 200 000 times higher than that of pure recycled Al coating,and was about 0.5 times lower than that of Zn coating. The microstruc-ture of recycled Al with 8.2 mass% Mg alloy coating on the steel substrate consisted of Al3Mg2,Al-Fe intermetallic compound and Al matrix. The results from salt fog spray test showed that recycled Al with 8.2 mass% Mg alloy coated steel had similar corrosion resistance ability to Zn coated steel.
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  Effect of δ Phase on Mechanical Properties of GH4169 Alloy at Room Temperature

  Neng-yong YE,, Ming CHENG,,?Shi-hong ZHANG,?Hong-wu SONG,?Hong-wei ZHOU, Ping-bo WANG

  中国钢铁期刊网. 2015, 22(8): 752-756.

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  Tensile tests of GH4169 alloy were performed at room temperature. Different fractions,distributions and shapes of δ phase were prepared by aging treated at 880 °C,930 °C and 980 °C for 5 h or 10 h. The effects of δ phase on the mechanical pro-perties of GH4169 alloy were investigated. The results show that 0.2% yield strength and ultimate tensile strength of GH4169 alloy increase by 61 MPa and 78 MPa respectively when the fraction of δ phase increases from 2.20% to 5.21%. Then,the ultimate ten-sile strength remains at 1 012 MPa even when the fraction of δ phase reaches 7.56%. The fraction effect of δ phase on the strength improvement of GH4169 alloy is more significant than morphology,and the critical fraction value is 5.21%. In addition,the elon-gation decreases by 14.1% when the fraction of δ phase increases from 2.20% to 7.56%. Excessive needle or short rod shaped δ phase is responsible for the reduction of elongation.