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Indirect Methods of Detecting and Evaluating Inclusions in Steel—A Review

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Journal of Iron and Steel Research International 2006年第3期13卷 1-8页

作者： zhang li-feng Department of Materials Science and Engineering Norwegian University of Science and TechnologyHogskoleringen 8 7491 Trondheim Norway

Indirect methods to detect and evaluate inclusions in steel are extensively reviewed, which include total oxygen content measurement, nitrogen pickup, steel and slag composition measurement, lining refractory observation, tracer studies of determining exogenous inclusions from slag and lining erosion, SEN clogging and final prod- uct tests. There is no single ideal method of detecting and evaluating inclusions in steel, so it is better to use several methods simultaneously to give a more accurate evaluation. Total oxygen content and nitrogen pickup in low carbon aluminum-killed steel as criterion of clean steel in many plants are summarized.

关键词： inclusion indirect method total oxygen nitrogen pickup

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Tool wear criterion,tool life,and surface roughness during high-speed end milling Ti-6Al-4V alloy

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第8期11卷 587-595页

作者： Song zhang Jian-feng li MOE Key Laboratory of High Efficiency and Clean Mechanical Manufacture School of Mechanical Engineering Shandong University Jinan 250061 China

The objective of the present research is to investigate the relationship among tool wear, surface topography, and surface roughness when high-speed end milling Ti-6Al-4V alloy, and also to define an optimal flank wear criterion for the cutting tool to integrate tool life and the surface roughness requirements of the finish milling process. An annealed Ti-6Al-4V alloy was selected as the workpiece material, undergoing end milling with uncoated carbide inserts. The flank wear of the insert was observed and measured with the toolmaker's microscope. To examine machined surfaces, 3D surface topography was provided by the white light interferometer, and the arithmetical mean roughness (Ra) was calculated with the WYKO Vision32 software. The flank wear increases with cutting time, and the maximal flank wear is set as the flank wear criterion. As the cutting process progresses, tool wear is the predominant factor affecting the variation of surface roughness. According to the plots for the tool wear propagation and surface roughness variation, an optimal flank wear criterion can be defined which integrates the tool life and the surface roughness requirements for the finish milling process.

关键词： Tool wear Surface topography Surface roughness Optimal flank wear criterion

Emergence and Decline of Scientific Paradigms in a Two-Group System

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Chinese Physics Letters 2012年第4期29卷 232-235页

作者： zhang feng-li zhang Mei Department of Physics Beijing Normal UniversityBeijing 100875

Idea spreading is an important process in science and *** this work,we study this spreading process in a population consisting of two groups based on a recent model proposed by Bornholdt et *** consider two types of division in the population:regular and random *** find some interesting phenomena,for example,the exchange of dominant ideas between the two groups in the cases of regular and the random division,and the appearance of a novel stage in which a few ideas interact strongly to seek a balance.

关键词： random exchange regular

EFFECT OF INSTABIliTIES OF FLOW ON MESOSCALE PREDICTABIliTY OF WEATHER SYSTEMS

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Journal of Hydrodynamics 2011年第2期23卷 193-203页

作者： LUO Yu zhang li-feng Institute of Meteorology PLA University of Science and Technology Nanjing 211101

The numerical solution of Boussinesq equations is worked out as an initial-value problem to study the effect of the instabilities of flow on the initial error growth and mesoscale predictability. The development of weather systems depends on different dynamic instability mechanisms according to the spatial scales of the system and the development of mesoscale systems is determined by symmetric instability. Since symmetric instability dominates among the three types of dynamic instability, it makes the prediction of the associated mesoscale systems more sensitive to initial uncertainties. This indicates that the stronger instability leads to faster initial error growth and thus limits the mesoscale predictability. Besides dynamic instability, the impact of thermodynamic instability is also explored. The evolvement of convective instability manifests as dramatic variation in small spatial scale and short temporal scale, and furthermore, it exhibits the upscale growth. Since these features determine the initial error growth, the mesoscale systems arising from convective instability are less predictable and the upscale error growth limits the predictability of larger scales. The latent heating is responsible for changing the stability of flow and subsequently influencing the error growth and the predictability.

关键词： instabilities of flow mesoscale system predictability initial errors

The Ecological Effects of Young Elm Trees Belt-Pumpkin Strip Intercropping System at the Agro-Pastoral Ecotone in Northern China

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Agricultural Sciences in China 2010年第8期9卷 1183-1193页

作者： DU Xiong DOU Tie-ling feng li-xiao zhang Wei-hong zhang li-feng College of Agronomy Agricultural University ofHebei Baoding 071001 P.R.China zhangbei Agricultural Resource and Ecological Environment Key Field Research Station Ministry of Agriculture Zhangjiakou 076450 P. R. China College of Plant Protection Agricultural University of Hebei Baoding 071001 P.R. China

Young elm trees belt-pumpkin strip intercropping was studied to solve the actual problem of resource losses in the large barren area resulted from reconverting cultivated land into forest in the agro-pastoral ecotone in northern China. The final objective was to realize effective utilization of the barren land with both ecological improvement and economic development. Field experiments were conducted together with laboratory analysis. The results indicated that the soil moisture level was remarkably increased in young elm trees belt-pumpkin strip intereropping because the pumpkin vines covered the gap between pumpkin planting-furrow and elm trees belt. The water use efficiency of the intercropping system was increased by 23.7-163.3% as compared with the single cropping. Elm trees belt-pumpkin strip intercropping changed the sequential succession trend of the grasses growing in the gap of the pumpkin planting-furrow. The annual grasses become the dominant vegetation. The nutritive value as fodder and yield of the annual grasses were also increased remarkably. The biomass of pumpkin, elm trees and grasses under intercropping increased by 24.4, 28.4 and 144.4%, respectively, as compared with those under single cropping. The land use efficiency was increased by 132%. It was also indicated that the soil erosion from the intercropping land was not increased due to pumpkin plantation. The differences in the soil erosion among intercropped area, elm trees belt and pumpkin strip with single cropping were not remarkable. Therefore, it was concluded that young elm trees belt-pumpkin strip intercropping is an effective way to utilize the barren land between the young elm trees belt and realize synergistic enhancement of ecological benefit and economic profit.

关键词： ecotone young elm trees belt-pumpkin strip intercropping water use efficiency land use efficiency ecological benefit economic profit

Monoterpene and tetrahydronaphthene derivatives from Senecio argunensis

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Chinese Chemical Letters 2009年第5期20卷 598-600页

作者： Chao feng zhang Ning li lin li Mian zhang Research Department of Pharmacognosy China Pharmaceutical University Nanjing 210038 China

Two new compounds, senarguines A and B, were isolated from Senecio argunensis. They were respectively identified as （Z）-3- ethylidene-9-hydroxyl-9-methyl-6,7-dioxaspiro [4.4] nonane-5,8-dione （1） and 3,6,6-trimeth... 详细信息

关键词： Compositae Senecio argunensis Senarguine A Senarguine B

Production of Nitrogen-Bearing Stainless Steel by Injecting Nitrogen Gas

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Journal of Iron and Steel Research International 2011年第11期18卷 7-11页

作者： SUN li-yuan li Jing-she zhang li-feng YANG Shu-feng School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Beijing 100083 China Department of Materials Science and Engineering Missouri University of Science and Technology Rolla 65401 Missouri USA

To replace nickel-based stainless steel, a nitrogen-bearing stainless steel was produced to lower the production cost stemming from the shortage of nickel recourses. Thermodynamic model to calculate the saturated nitrogen content in the stainless steel was developed and the model was validated by experimental measurements performed with a high temperature induction furnace. Nitrogen gas under constant pressure was injected into the molten steel with a top lance. Thus, the nitrogen was transferred to the molten stainless steel. The effects of chemical composition, temperature, superficial active elements and nitrogen flow rate on the transfer of nitrogen to the steel were investigated and discussed. The results showed that the dissolution rate of nitrogen in the molten steel increases with a higher temperature and larger nitrogen flow rate but decreases significantly with an increase in the content of surface- active elements. Alloying elements such as chromium and manganese having a negative interaction coefficient can increase the dissolution of nitrogen in the molten steel. It was also proposed that the primary factor affecting the final saturated nitrogen content is temperature rather than the dissolved oxygen content.

关键词： nitrogen-bearing stainless steel nitrogen thermodynamic modeling

Microstructure and properties characteristic during interrupted multi-step aging in Al-Cu-Mg-Ag-Zr alloy

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Rare Metals 2011年第4期30卷 419-423页

作者： ZHUBaohong XIONG Baiqing zhang Yong＇an zhang Jianbo WANG feng li Zhihui State Key Laboratory of Nonferrous Metals and Processes General Research Institute for Nonferrous Metals Beijing 100088 China

The effects of interrupted multi-step aging on the microstructure and properties of A1-Cu-Mg-Ag-Zr alloy were studied by tensile, hardness, electrical conductivity tests and transmission electron microscopy （TEM）. Interrupted multi-step aging delayed the peak aging time compared to one-step aging and kept the same levels of hardness, electrical conductivity, ultimate tensile strength （UTS）, yield strength （YS） and elongation as those of the T6 temper alloy while increased the fracture toughness notably. Ω phase and a little θ＇ phase precipitated and grew simultaneously in the process of one-step aging at 160℃. During the second-step aging at 65℃ of interrupted multi-step aging, no TEM characteristic of Ω precipitates could be found. During the third step of interrupted multi-step aging, Ω began to dominate the microstructure like what happened in the process of one-step aging. The difference of properties between the T6 temper and the interrupted multi-step aged alloys might be related to the different precipitation sequences in the process of the two heat treatment technologies.

关键词： aluminum copper alloys heat treatment microstructure fracture toughness aging

Behavior of MgO·Al_2O_3 Based Inclusions in Alloy Steel During Refining Process

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Journal of Iron and Steel Research International 2010年第7期17卷 1-6页

作者： YANG Shu-feng li Jing-she zhang li-feng Kent Peaslee WANG Zai-fei School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Beijing 1000.83 China Department of Materials Science and Engineering Missouri University of Science and Technology Rolla 65401 M. issouri USA

The transformation of MgO· Al2O based inclusions in alloy steel during refining has been studied by in- dustrial trials. Besides Factsage software is used to sttidy the formation and modification of spinel inclusions in alloy steel using calcium treatment during refining process. The results show that the transformation sequence of inclu- sions is：MgO· Al2O→CaO-Al2O3-MgO complex inclusions--→MgO· Al2O, and under present experimental con- dition, in order to avoid forming MgO· Al2O inclusions the content of dissolved Ca in the molten steel has to reach 1 × 10-6. Also the results show that when more calcium was added to molten steel, the content of Alz 03 and MgO will be lower. Besides, increasing the content of CaO in the inclusions will increase even if tlae content of SiO2 changes little.

关键词： alloy steel non-metallic inclusion MgO· Al2O spinel thermodynamics