2010年, 第17卷, 第6期　刊出日期：2010-06-15

  

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工艺
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  Dynamic Soft Reduction Technology for Bloom Casting

  CHEN Yong;et al

  中国钢铁期刊网. 2010, 17(6): 1-1.

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  The dynamic soft reduction technology for 360mm×450mm bloom casting and its application results at PISCO (Panzhihua Iron & Steel Co.) were presented. In order to analyze the influence of the soft reduction on internal defects of bloom, such as center porosity and central segregation, experiment for contrasting process with or without soft reduction for bloom was investigated. The operation shows that after applying the soft reduction of bloom alloy steel, the ratio of center porosity whose defect level is below 1.0 increased from 66.67% to 85.71%, ratio of central segregation whose defect level is below 1.0 increased from 94.44% to 100%, ratio of central shrinkage cavity which is free increased from 88.89% to 96.42%, and central segregation index of carbon decreased from mean value of 1.15 to 1.05. These results have provided important technology supports for PISCO to optimize the steel product structure, and to improve the production of high quality, property, and value added products.
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  Viscosity and Viscosity Estimate Model of Fluoride-free and Titanium-Bearing Mold Fluxes

  QI Xin;et al

  中国钢铁期刊网. 2010, 17(6): 6-6.

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  This work systematically researches the relationship between the binary basicity (CaO/SiO2), TiO2, Na2O, Li2O, MgO, MnO, B2O3 and viscosity in fluoride-free and titanium-bearing mold fluxes. The results of these experiments indicate that Li2O, B2O3 and Na2O play major roles in decreasing viscosity, especially Li2O, which is the most effective flux, while MgO and MnO exert little effect on viscosity. Meanwhile, the conclusion was also reached that, with increased TiO2 content, the viscosity of fluoride-free and titanium-bearing mold fluxes increases at first but then falls when the amount of TiO2 is greater than 6.0 wt%. Based on large amounts of experimental statistics of the viscosity of fluoride-free and titanium-bearing mold fluxes, a predictive model was built from the principles of the Weymann-Frenkel formula. This model can be used to predict the viscosity of fluoride-free and titanium-bearing mold fluxes. In fact, the predicted values approximate the observed values with a ±10.6% average deviation. Compared with the classical models, for which the average deviation is higher, we find that the new model can be applied to estimate the viscosity of fluoride-free and titanium-bearing mold fluxes.
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  Non-linear Vibrations and Stability of Moving Strip with Time-dependent Tension in Rolling Process

  Sun Jian-liang;et al

  中国钢铁期刊网. 2010, 17(6): 11-11.

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  Nonlinear vibrations of the moving strip between two mills of some cold tandem rolling mill in the rolling process were investigated. The strip is moving with a time-dependent tension, namely a harmonically varying tension about a constant initial tension. The transverse parametric vibration model of moving strip in the rolling process was established. Approximate solutions were obtained using the method of multiple scales. Depending on the variation of the tension, three distinct cases arise: frequency away from zero or two times the natural frequency; frequency close to zero; frequency close to two times the natural frequency. For frequency close to zero and away from zero and two times the natural frequency, the system is always stable. For frequency close to two times the natural frequency, the stability is analyzed respectively when the trivial solution is existence and the nontrivial solution is existence. Numerical simulation was made on some 1660mm tandem rolling mill, the stable regions and unstable regions for parametric resonance are determined with different cases. The rolling speed and the thickness of strip have strong influences on the stability of principle parametric resonances. But the distance between two mills has little influence on the stability of principle parametric resonances.
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  Optimization of Short Stroke Control Preset for Automatic Width Control of Hot Rolling Mill

  DU Xiao-zhong;et al

  中国钢铁期刊网. 2010, 17(6): 16-16.

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  Compensation Model For Shape Measuring of Cold Strip Rolling

  YU Bing-qing;et al

  中国钢铁期刊网. 2010, 17(6): 21-26.

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  The shape meter is interfered by some unavoidable factors in the process of cold strip shape measuring, so the measuring results can not reflect the ture shape and the measuring precision is low. In this paper, The influence of the measuring results is detailed analysed, which is influenced by the measuring error of strip edges、the transverse temperature difference of strip、the shape detection roller deflection and the shape of strip coil, The corresponding compensation models are established. And a cold strip mill is calculated as an example, gaines some disciplinarian cognitions.
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  Application of Self-learning to Heating Process Control of Simulated Continuous Annealing

  WANG Yun-hua;et al

  中国钢铁期刊网. 2010, 17(6): 27-31.

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  On the background of the bright continuous simulative annealing experimental machine, the process control model of heating system is built in the paper. The heating model was simplified and the self-learning parameter was normalized in the paper in order to enhance the precision of the temperature control. By way of dividing temperature layers and exponential smoothing disposal with the data of the annealing experiment, self-learning of heating model was carried out, and at the same time, by way of exponential smoothing with the deviation of self-learning parameter of the heated phase in heating process, dynamic modifying of self-learning parameter was carried out, and so that dynamic modifying of heating electric current was carried out, and so, the precision of temperature control was confirmed. Application indicates that the process control model of heating system can control temperature with high precision, the deviation can be controlled in 8℃,it can offer reference to the research of similar equipments, and the method of self-learning is also adapt to process control of cooling system
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  New Integrated Processes for Treating Cold-Rolling Mill Emulsion Wastewater

  ZHANG Yun-hua;et al

  中国钢铁期刊网. 2010, 17(6): 32-0.

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  A large amount of oily wastewater is discharged during steel rolling in the steel industry, and the emulsion wastewater discharged during the steel cold-rolling mill contain a lot of non-degradable organic pollutants. However, the traditional treatments of oily wastewater can hardly work well to reach the discharge standards. There are two new techniques for emulsification wastewater treatment: the one is the integrated process of gas-energy-flocculation (GEF) and electrochemical catalytic oxidation (ECO) and membrane bioreactor (MBR); the other is the integrated process of ultra-filtration (UF) and ECO and MBR. Both of them are adopted to the continuous pilot test on the scale of 200L/h to 3000L/h. Moreover, every module of the combined techniques is analyzed. The operating parameters of every mould are investigated and the relationships between the operating parameters and CODCr removal efficiencies of the two integrated processes are evaluated. The experimental results have shown that almost all the oil and non-degradable organic substances are effectively removed with the effluent CODCr less than 30mg/L. The ultimate treated water quality could meet the requirement for productive reuse. What’s more, the integrated process of UF and ECO and MBR has a more stable effluent quality. Hence it can be widely used in a variety of industrial fields.
材料
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  Influence of Prior Austenite Deformation and Non-Metallic Inclusions on Ferrite in Low Carbon Steels

  ZHANG Chi;et al

  中国钢铁期刊网. 2010, 17(6): 36-42.

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  Abstract Effects of prior austenite deformation and non-metallic inclusions on the ferrite nucleation and grain refinement of two kinds of low carbon steels have been studied. The ferrites nucleation on MnS and V(C,N) is observed. The combination of thermal-mechanical processes with adequate amounts of non-metallic inclusions formed in low carbon steels could effectively refine the grain size and the microstructure. Ferrite nucleated on the single MnS or V(C,N) inclusions and complex MnS+V(C,N) inclusion. The proper addition of elements S and V could effectively promote the formation of ferrite and further refinement of ferrite grains.
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  Effect of Cryogenic Treatment on Properties of Cr8-Type Cold Work Die Steel

  CHI Hong-Xiao;et al

  中国钢铁期刊网. 2010, 17(6): 43-46.

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  Effect of cryogenic treatment on the properties of Cr8-type cold work die steel was investigated. The results show that cryogenic treatment increases hardness by decreasing retained austenite, but the degree depends on the austenitizing temperature. When quenching at lower austenitizing temperature, the steel can obtain higher toughness by cryogenic treatment substituting conventional treatment process. Cryogenic time has little effect on cryogenic treatment. Conversely, cryogenic temperature has a greatly effect on cryogenic treatment that the effect of cryogenic treatment is more obvious with decreasing cryogenic temperature. In addition, deep cryogenic treatment improves the wear resistance by precipitating more homogeneous MC and M6C-carbides.
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  Microstructure, Texture, and Formability of Nb+Ti Stabilized High-Purity Ferritic Stainless Steel

  DU Wei;et al

  中国钢铁期刊网. 2010, 17(6): 47-52.

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  The microstructure, texture and formability of Nb+Ti stabilized high-purity ferritic stainless steel were investigated. The interstitial elements C and N could be fully stabilized with Nb and Ti, and the precipitates were mainly composed of TiN and NbC. By analyzing texture at the various thermomechanical processes, the intensity of α-fiber obtained during hot rolling was reduced greatly after annealing and a non-uniform γ-fiber was achieved. The favorable γ-fiber was displayed in cold rolled and annealed sheet, whereas the texture maximum located at (554)<225>. The formation of this shifted texture mainly attributed to the influence of “Zener” drag and selective growth. Finally, the obtained mean r-value was notably higher, mean r=1.70, compared with traditional ferritic stainless steels.
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  Microstructure and Transformation Characteristics of Acicular Ferrite in High Niobium-Bearing Microalloyed Steel

  YANG Jing-hong;et al

  中国钢铁期刊网. 2010, 17(6): 53-59.

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  The transformation behavior and microstructural characteristics of a low carbon high Nb-bearing microalloyed pipeline steel have been investigated by deformation dilatometry and microstructure observation. The continuous cooling transformation curves (CCT) of the tested steel was constructed. High Nb content and deformation enhancing the formation of acicular ferrite; the microstructures are range from PF, QF to AF with increasing cooling rates from 0.5 to 50℃/s and dominated by acicular ferrite in a broadened cooling rate higher than 5℃/s. The chaotic microstructure consists of non-equiaxed ferrite and interwoven ferrite laths distributed high density dislocations and sununits. The results of isothermal holding show that acicular ferrite microstructure is formed in region of 550-600℃. With the holding time or temperature increased, some low misorientations boundaries change to high misotrentationn as dislocations moving and grain boundaries coarsening.
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  Embrittlement Mechanism due to Slow Cooling During Quenching for M152 Martensitic Heat Resistant Steel

  YANG Gang;et al

  中国钢铁期刊网. 2010, 17(6): 60-66.

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  The brittleness of M152 martensitic heat resistant steel due to slow cooling during quenching was experimentally investigated by means of mechanical property test, TEM and XRD analysis. The results showed that the nonreversal brittleness of M152 steel due to slow cooling during quenching was caused by the continuous precipitation of M23C6 along prior austenite grain boundaries and of M2C along prior residual austenite film. The residual austenite in the steel was unstable and may decompose due to the precipitation of second phase during the process of slow cooling after quenching. The low cooling rate in the temperature range from 820 to 660℃ has a strong effect on the impact toughness of the steel, the precipitation of second phase in the same temperature range results in nonreversal brittle.
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  Effects of High Strain Rate on Properties and Microstructure Evolution of TWIP Steel Subjected to Impact Loading

  LI Da-zhao; et al

  中国钢铁期刊网. 2010, 17(6): 67-73.

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  The mechanical properties of the TWIP steel subjected to impact loading at various strain rates were analyzed by the Split Pressure Hopkinson Bar. Meanwhile the microstructure of the TWIP steel fore-and-after the dynamic deformation were characterized and analyzed by optical microscopy (OM), X-ray diffraction (XRD), and transmission electron microscope (TEM). The result shows that when the TWIP steel was deformed under dynamic station, the stress, microshardness and work hardening rate increase with the increment of strain and strain rate; there exist stress fluctuation and decline of work hardening rate for adiabatic temperature rising softening. There exist many pin-like deformation twins in the microstructure of the TWIP steel subjected to impact loading, the grain size after deformation is bigger than that before; the interaction of twins with dislocation and twins with twins, especial emergence of high order deformation twins are the main strengthening mechanisms of the TWIP steel. The nucleation mechanism of deformation twins will be “rebound mechanism”; the incomplete deformation twins can be observed when the strain rate is low; when strain rate raises, deformation twins unite together; furthermore, deformation twins become denser because the nucleation rating enhancing with strain rate increasing.
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  Thermomechanical Fatigue Behavior of Powder Metallurgical Nickel Base Superalloy FGH96

  GU Yu-li;et al

  中国钢铁期刊网. 2010, 17(6): 74-79.

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  The fracture behavior in the thermo-mechanical fatigue (TMF) of the Nickel-base Powder Metallurgy Superalloy FGH96 was investigated under in-phase (IP) and out-of –phase (OP) loadings at the temperature range from 550℃ to 720℃ and mechanical strain amplitude range from 0.3% to 0.8％. The results show that the FGH96 TMF fracture character is intergranular on the IP samples and transgranular cleavage on the OP samples, at the same strain amplitude, the fatigue life is shorter for the IP than that for the OP samples that is related to crack propagation along grain boundary on the IP samples, the γ′ size is larger in the IP than that in the OP sample, which is related to the bulk diffusion processes accelerated by the tensile strain during the high temperature portion of the IP cycle. Dislocation pairs and stacking faults are main microstructures induced by IP TMF, and they are hindered by the grain boundary, which likely resulted in the crack propagation along the grain boundary in the IP samples.