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2008年, 第15卷, 第4期 刊出日期:2008-08-15
  

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    Review
  • W F Kladnig
    中国钢铁期刊网. 2008, 15(4): 1-0.
    摘要 ( )   可视化   收藏
    For acid pickling heat treated mild steel and steel products, up to the middle of the last century, sulfuric acid was primarily in use, which has been replaced stepwise by hydrochloric acid since the sixties. During this time, the pickling of high alloyed steel with hydrofluoric acid or mixtures for hydrofluoric acid together with nitric acid has also been applied on industrial scale. The technologies used by several plant contractors hereby show considerable differences in their engineering. The study provides a survey of the progress in the state of art of regeneration technology as well as the use of different pickling media in the form of a review on existing technologies as well as improvements done within the recent years in the area.
  • Metallurgy and Metal Working
  • TANG Ping;XU Chushao;WEN Guanghua;ZHAO Yanhong;QI Xin
    中国钢铁期刊网. 2008, 15(4): 7-0.
    摘要 ( )   可视化   收藏
    An experimental apparatus for simulating copper mold is used to quantify the heat flux through the slag film and to obtain a solid slag for further determining its crystallization behavior. The result indicates that both the chemical composition of the mold powder and the cooling rate have an important influence on the heat flux through the slag film. With increasing the binary basicity, the heat flux of slag film decreases at first, reaches the minimum at the basicity of 14, and then increases, indicating that the maximum binary basicity is about 14 for selecting “mild cooling” mold powder. The heat transfer through the slag film can be specified in terms of the crystalline ratio and the thickness of the slag film. Recrystallization of the solid slag occurs and must be considered as an important factor that may influence the heat transfer through the solid slag layer.
  • HU Changqing;ZHANG Chunxia;HAN Xiaowei;YIN Ruiyu
    中国钢铁期刊网. 2008, 15(4): 12-0.
    摘要 ( )   可视化   收藏
    Sulfur flow for new generation steel manufacturing process is analyzed by the method of material flow analysis, and measures for SO2 emission reduction are put forward as assessment and target intervention of the results. The results of sulfur flow analysis indicate that 90% of sulfur comes from fuels. Sulfur finally discharges from the steel manufacturing route in various steps, and the main point is BF and BOF slag desulfurization. In sintering process, the sulfur is removed by gasification, and sintering process is the main source of SO2 emission. The sulfur content of coke oven gas (COG) is an important factor affecting SO2 emission. Therefore, SO2 emission reduction should be started from the optimization and integration of steel manufacturing route, sulfur burden should be reduced through energy saving and consumption reduction, and the sulfur content of fuel should be controlled. At the same time, BF and BOF slag desulfurization should be optimized further and coke oven gas and sintering exhausted gas desulfurization should be adopted for SO2 emission reduction and reuse of resource, to achieve harmonic coordination of economic, social, and environmental effects for sustainable development.
  • WANG Biao;JI Zhenping;LIU Wenhong;MA Jiaocheng;XIE Zhi
    中国钢铁期刊网. 2008, 15(4): 16-0.
    摘要 ( )   可视化   收藏
    By means of Gleeble1500 dynamic thermomechanical simulator, the continuous casting process for HRB335C steel was simulated using solidifying method and hot ductility and strength of the steel were determined. The test results indicate that there are three temperature regions of brittleness for HRB335C billet in the temperature range from 700 ℃ to solidification point; the first temperature region of brittleness is 1 300 ℃ to solidification point of the billet, the second temperature region of brittleness is 1 200-1 000 ℃, and the third temperature region of brittleness is 700-850 ℃; the steel is plastic at 850-1 000 ℃. The cracking sensitivity was studied in the different temperature zones of the brittleness for steel HRB335C and the target surface temperature curve for the secondary cooling is determined. With optimized process, the mathematical model of the steady temperature field with twodimensional heat transfer for 150 mm×150 mm HRB335C steel billet was established to optimize the secondary cooling process. The conic relation of water distribution between secondary cooling water flux and casting speed is regressed. Keeping the surface temperature of billet before the straightening point above 1 000 ℃, the results of billet test indicate that there is free central shrinkage cavity. The billet defect is decreased greatly, and the quality of billet is obviously improved.
  • CHEN Shuying;CHANG Guowei;YUE Xudong;WU Chunjing
    中国钢铁期刊网. 2008, 15(4): 21-0.
    摘要 ( )   可视化   收藏
    The expression of the solute distribution in columnar crystal zone was deduced when the solidliquid interface bended periodically, and the quantitative calculations of macrosegregation were also made in the process of the continuous casting. The solute distribution along the thickness direction of the slabs was obtained, which verified the theoretical calculation. The effect of the bulge size, solidification speed, and solidification shrinkage speed on macrosegregation of the slabs was calculated. It can be concluded that normal segregation and negative segregation alternatively appear as a result of the bulge. The normal segregation exponentially depends on the bulge size, and the negative segregation linearly depends on the bulge size. The extent of the normal segregation is greater than that of the negative segregation when the bulge size is the same. The macrosegregation of the same position along the thickness direction of the slabs changes in a sine wave with increasing the solidification rate, and the amplitude is larger at the casting blank center. The normal segregation linearly decreases with increasing the solidification shrinkage speed, and when the solidification shrinkage speed exceeds a critical value, the segregation appears negatively and increases linearly.
  • WANG Jun;ZHU Miaoyong;ZHOU Haibing;WANG Ying
    中国钢铁期刊网. 2008, 15(4): 26-0.
    摘要 ( )   可视化   收藏
    The fluid flow and the interfacial phenomenon of slag and metal in tundish with gas blowing were studied with mathematical and physical modeling, and the effects of gas flowrate, the placement of porous beam for the generation of bubbles, and the combination of flow control devices on the flow and slagmetal interface were investigated. The results show that the position of gas bubbling has a significant effect on the flow in tundish, and the placement of porous beam and gas flowrate are the two main factors affecting the entrapment of slag in tundish. The closer the porous beam to the weir, the more reasonable is the flow, which is in favor of the control of slag entrapment in tundish.
  • WEN Guanghua;LIU Hui;TANG Ping
    中国钢铁期刊网. 2008, 15(4): 32-0.
    摘要 ( )   可视化   收藏
    The isothermal and nonisothermal experiments were performed to construct the continuous cooling transformation (CCT) and temperature time transformation (TTT) diagrams of four industrial mold fluxes through visual observations in an experimental apparatus based on the single hot thermocouple technique (SHTT). The results of the CCT diagrams indicate that ① the crystallization temperature of mold fluxes lowers as the cooling rate increases, ② the mold fluxes have larger critical cooling rate, higher crystallization temperature, and less onset time of crystallization when the basicity increases or the viscosity decreases, ③ the influences of the melting points of the mold fluxes on their crystallization tendency are not significant. Isothermal tests show that the onset time of crystallization decreases at first, and then increases, and finally represents a “C” shape with increasing isothermal temperature. The TTT diagrams of four industrial mold fluxes were divided into two separate “C” shape regions. The crystal phase of C20A selected was analyzed by Xray diffraction, which is cuspidine (Ca4Si2O7F2) over 1 100 ℃ and calcium silicon oxide fluoride (Ca2SiO2F2) below 1 100 ℃. When compared with the TTT diagram, the CCT diagram can provide a more realistic estimate of the critical cooling rate of the mold fluxes. Thus, both the CCT and TTT diagrams can unambiguously describe the crystallization phenomena of the mold fluxes.
  • SUN Binyu;YUAN Shijian
    中国钢铁期刊网. 2008, 15(4): 38-0.
    摘要 ( )   可视化   收藏
    According to the deformation characteristics of threeroll tube rolling, the existent disadvantages of traditional A Geleiyi and A Tselikov′s formulas were objectively analyzed. An assumption approximate to actual situation was put forward. After suitable simplification, the energy method was adopted to establish velocity fields for permissive movement in deformed areas, and the calculation formula of average unit pressure for threeroll tube rolling was deduced. The values of theoretical calculation are basically consistent with the measured values of largescale aluminum tube during onsite rolling process. The results proved that the formula is reasonable.
  • LI Xuetong;WANG Minting;DU Fengshan
    中国钢铁期刊网. 2008, 15(4): 42-0.
    摘要 ( )   可视化   收藏
    Using threedimensional rigidviscoplastic finite element method (FEM), a coupling multivariable numerical simulation model for steel plate rolling has been established based on the physical metallurgy microstructural evolution rule and experiential equations. The effects of reduction, deformation temperature, and rolling speed on the deformation parameters and microstructure in plate rolling were investigated using the model. After a typical rolling process of steel plate 16Mn is simulated, the strain, temperature, and microstructure distributions are presented, as well as the ferrite grain transformation during the period of cooling. By comparing the calculated ferrite grain sizes with measured ones, the model is validated.
  • Material
  • LI Baomian;XU Guangming;CUI Jianzhong
    中国钢铁期刊网. 2008, 15(4): 51-0.
    摘要 ( )   可视化   收藏
    The variation law of cladding thickness as well as the structures and properties of H90steel clad strip produced by inversion solidification was studied. The interface bonding mechanisms were approached. It is found that the thickness of H90 cladding goes sequentially through the solidification growth stage, holding stage, and remelting stage, with an increase in immersion time. The higher the preheating temperature of the steel coil, the thicker is the maximum cladding thickness. Observation by using optical microscopy (OM) and the electron probe microanalyzer (EPMA) shows that the microstructure of H90 cladding is composed of equiaxed grains, and that interdiffusion between Cu and Fe at interface occurs but obvious diffusion of Zn and the intermetallic layer are not observed. The diffusion layer is thin and about 4 μm. Multipass small reduction cold rolling and repeated bending tests show that the interface is firmly bonded. Tensile test shows that the mechanical properties of the asclad strips can meet the requirements of GB52132001 for the Fgrade deepdrawing steel plate though there is a slight difference in the mechanical properties among the clad strips with different cladding thickness.
  • XU Jinqiao;LIU Yazheng;ZHOU Shumei
    中国钢铁期刊网. 2008, 15(4): 57-0.
    摘要 ( )   可视化   收藏
    With the investigated subject of 82B rod, the interlamellar spacings of pearlite at different isothermal transformation temperatures and different cooling rates during continuous cooling transformation were measured, and the effect of the isothermal transformation temperature and cooling rate on the interlamellar spacing was analyzed quantitatively. Moreover, the relationship models between undercooling and interlamellar spacing were presented by data regression. The experimental results show that the relationship between undercooling and reciprocal interlamellar spacing remains linear when the undercooling is not very large, or else, the interlamellar spacing tends to be constant and the relationship will deviate from linearity.
  • Shahram Kheirandish;Ahmad Noorian
    中国钢铁期刊网. 2008, 15(4): 61-0.
    摘要 ( )   可视化   收藏
    The effect of niobium addition on the microstructure of cast AISI H13 hot work tool steel was evaluated by using EDX analyzer attached to the scanning electron microscope. The volume percent of eutectic area and eutectic cell size and also volume percent of different carbides of new steel, which is heat treated under different conditions, are also determined. The results show that the a niobium addition modifies the cast structure of Nballoyed hot work tool steel, and reduces the size and volume of eutectic cells, and increases the maximum hardness of the steel.
  • CUI Xianghong;SHAN Jun;YANG Zirun;WEI Minxian;WANG Shuqi;DONG Chuang
    中国钢铁期刊网. 2008, 15(4): 67-0.
    摘要 ( )   可视化   收藏
    The alloying design of cast hotforging die steels was analyzed. The relationship of the life of cast hotforging dies with the failure patterns was studied. The thermal wear resistance was believed to be the key property for the alloying design of cast hotforging die steels. The alloying design parameters were selected and optimized for the cast hotforging die steel with high wear resistance. The wear resistance of the optimized cast die steel was evaluated in comparison with commercial H13 steels and 3Cr2W8V steel. In the new cast hotforging die steel, VC is predominant carbide with Cr and Mo as the main solution elements in αFe. It is found that the cast die steel has significantly lower wear rate than normal H13 steel and 3Cr2W8V steel, almost the same as that of high purity H13 steel. The high wear resistance of the new cast hotforging die steel can be attributed to its reasonable alloying design and nonsensibility to the detrimental function of S and P.
  • NI Hongwei;HE Hang;LI Guangqiang;LIU Jing
    中国钢铁期刊网. 2008, 15(4): 73-0.
    摘要 ( )   可视化   收藏
    Preparation of nanocrystalline 430L stainless steel by both highenergy ball milling and spark plasma sintering technique has been investigated. The results have shown that the hardness can be improved markedly with an increase in sintering temperature and holding time. The lower the apparent porosity of nanocrystalline 430L stainless steel, the higher is the Vickershardness. The tensile strength reached a maximum value of 713 MPa when the sample was sintered at 1 173 K for 10 min, and then it evidently decreased with an increase in sintering temperature and holding time because of the growth of crystalline grain.
  • ZHANG Ruiqian;LIU Yaoguang;HUANG Ningkang
    中国钢铁期刊网. 2008, 15(4): 77-0.
    摘要 ( )   可视化   收藏
    Titanium carbide coatings are widely used as various wearresistant material. The hydrogen erosion resistance of TiCC films and the effect of hydrogen participation on TiCC films were studied. Seventyfive percent TiCC films are prepared on stainless steel surface by using ion mixing, where TiCC films are deposited by rf magnetron sputtering followed by argon ion bombardment. The samples are then submitted to hydrogen ion implantation at 12×10-3 Pa. Characterization for the 75% TiCC films was done with SIMS, XRD, AES, and XPS. Secondary ion mass spectroscopy (SIMS) was used to analyze hydrogen concentration variation with depth, XRay diffraction (XRD) was used to identify the phases, and Auger electron spectra (AES) as well as Xray photoelectron spectra (XPS) were used to check the effects of hydrogen on shifts of chemical bonding states of C and Ti in the TiCC films. It is found that TiCC films on stainless steel surface can prevent hydrogen from entering stainless steel.
  • ZHAO Cai;TANG Di;JIANG Haitao;ZHAO Songshan;LI Hui
    中国钢铁期刊网. 2008, 15(4): 82-0.
    摘要 ( )   可视化   收藏
    The quenching and partitioning (Q&P) process was experimentally investigated on the thermomechanical simulator (Gleeble3800). The microstructure and fracture mechanism of the sheets were investigated by means of TEM. It was found that the microstructure of quenched and partitioned steel consists of fine lath martensite and thin interlath austenite films. The optimum quenching temperature of producing the maximum amount of retained austenite after final quenching at room temperature was predicted by Matlab software package. It was found that the calculations by Matlab software can provide guidance for experimental processing design reliably. The volume fraction of retained austenite at room temperature was approximately 8%, which was measured easily by the software VC60++ programming. The results verified that quenched and partitioned steel possesses a good combination of strength and plasticity due to its fine microstructure. This steel exhibited high ultimate tensile strength (exceeding 1 000 MPa) and good elongation of 25%. The results showed that the fracture mechanism of the sheets is typical tough fracture under the condition of tensile failure.
  • A Amirsadeghi;M Heydarzadeh Sohi;S F Kashani Bozorg
    中国钢铁期刊网. 2008, 15(4): 86-0.
    摘要 ( )   可视化   收藏
    Microhardness and wear resistance of different microstructures formed by TIG (tungsten inert gas) surface melting and chromium surface alloying (using ferrochromium) of ADI (austempered ductile iron) were studied. Surface melting resulted in the formation of a ledeburitic structure in the melted zone, and this structure has a hardness up to 896 HV as compared to 360 HV in that of ADI. Moreover, chromium surface alloying resulted in the formation of different structures including: (1) a hypereutectic structure consisting of primary (Fe,Cr)7C3 carbides and a eutectic matrix of transformed austenite (into martensite and retained austenite), as also (Fe,Cr)7C3 carbides, with a hardness of 1 078 HV; (2) a hypoeutectic structure consisting of the same eutectic along with transformed primary austenite, with a hardness of 755 HV; and (3) a ledeburitic structure with an acicular morphology and a hardness of 896 HV. The results also indicated that surface melting reduced the wear rate of the ADI by approximately 37%. Also, chromium surface alloying yielded a superior wear behavior and reduced the wear rate of the treated specimens by about 38% and 70%, depending on the structures formed.