Mathematical Modelling for Microstructure Evolution and Development of Ultra Fine Grained Plain Carbon Steel in a Tandem Hot Strip Mill

Society demands high strength and environmental conscious steel and our solution is ultra fine grained steel without any rare earth alloy. We developed mathematical modelling for microstructure evolution and characterized rolling condition for ultra fine grained plain carbon steel in the tandem hot strip mill. We constructed a new tandem hot strip mill rolled at heavy reduction and low temperature in the last 3 stands in the finishing train. We produced ultra fine grained plain carbon strip with grain size of 3 microns. This steel has 30% improved strength and better formability compared to the conventional schedule rolling steel.     

Application of Multiblock Grid and Dual-Level Parallelism in Coastal Ocean Circulation Modeling

Numerical grid generation techniques play an important role in the numerical solution of partial differential equations on arbitrarily shaped regions. For coastal ocean modeling, in particular, a one-block grid covering the region under study is commonly used. Most bodies of water of interest have complicated coastlines; e.g., the Persian Gulf and Mediterranean Sea. Since such one-block grids are not boundary conforming, the number of unused grid points can be a relatively large portion of the entire domain space. Other disadvantages of using a one block grid include large memory requirements and long computer processing time. Multiblock grid generation and dual-level parallel techniques are used to overcome these problems. Message Passing Interface (MPI) is used to parallelize the Multiblock Grid Princeton Ocean Model (MGPOM) such that each grid block is assigned to a unique processor. Since not all grid blocks are of the same size, the workload varies between MPI processes. To alleviate this, OpenMP dynamic threading is used to improve load balance. Performance results from the MGPOM model on a one-block grid, a twenty block grid, and a forty-two block grid after a 90-day simulation for the Persian Gulf demonstrate the efficacy of the dual-level parallel code version.     

普通C-Mn钢超细晶中厚板的带状组织

采用Gleeble2000热模拟试验机研究了普通C-Mn钢的再结晶规律，在实验室轧机上进行了C-Mn钢超细晶中板的轧制，并且在首钢中厚板厂工业轧机上进行了超细晶中厚板的工业试制，研究了工艺条件对中厚板带状组织的影响，分析了带状组织产生的机理。研究结果表明，在靠近静态相变温度Ar3附近的未再结晶区进行大变形量轧制(形变诱导相变)，不仅可以使板材的铁素体晶粒细化甚至获得超细晶组织，而且普通C-Mn钢中厚板中的带状组织减轻1～2级；降低精轧开轧温度有利于减轻板材的带状组织；在未再结晶区控轧有利于减轻板材的带状组织；随着未再结晶区形变量增加，板材的带状组织减弱。     

C-Mn超级钢的工业化生产和应用

以屈服强度为200 MPa级的普碳钢为基本成分,采用成分微调与控轧控冷工艺相结合的技术路线,可将屈服强度提高到400～500MPa,同时保证良好的综合性能.产品应用于汽车、建筑等行业,取得了用户降低成本,生产厂多获效益的双赢效果.介绍了G-Mn钢轧制过程组织变化、超级钢生产和应用等方面取得的研究成果.     

Normal vibration of a plain bearing working under boundary lubrication conditions

During sliding in a plain-bearing system under boundary lubrication conditions, the impact of the existing microasperities causes the system to vibrate. The resulting spectrum depends, among other things, on the type of material and the micro- and macrogeometries of the sliding surfaces. Running-in of plain bearings can be monitored by studying the changes in the respective spectra of vibrations     

Bacterial contamination of Mediterranean coastal seawater as affected by riverine inputs: simulation approach applied to a shellfish breeding area (Thau lagoon,France)

Consequences of short-term changes in thermotolerant coliform loads on their spatio-temporal distribution in a Mediterranean lagoon with large-scale mollusk farming (Thau lagoon, France) were explored using a simulation approach. Simulations were based on bacterial transport and survival coupled models forced by the input of bacterial loads from the two main rivers (Vène and Pallas) that flow into the lagoon. Different flow types (reference, sudden and constant), bringing the same bacterial load, were considered and subsequent spatial and temporal bacterial contamination of lagoon surface water and shellfish was estimated. Simulation results showed that as long as loads were high, hydrodynamical processes governed the distribution of bacterial abundance in receiving areas. As soon as loads decreased or when time supply increased, biological die-off processes became dominant. Bacterial contamination of shellfish induced by the different flow types appeared to depend on the receiving area. In the case of Pallas River area, a sudden input of bacteria led to a high bacterial contamination of shellfish but only during a short period ( approximately 1 day). A constant input of the same amount of bacteria induced a lower but significant contamination during all the simulation period (10 days). On the contrary, bacterial inputs from the Vène River led to shellfish contamination only when bacteria were delivered through a flood event. Exposure time of bacteria to adverse environmental conditions appeared to be the main explanation to the above-mentioned differences. Consequences of our results in terms of environmental management strategy were discussed.     

Surface Ferrite Grain Refinement and Mechanical Properties of Low Carbon Steel Plates

Considering the specialities of the steel plate production, the TMCP study has been carried out with Gleeble 2000 tester to explore the possibility of fine grained ferrite in the low carbon steel plates with the chemical composition of C 0.13--0.18, Si 0.12-0.18, Mn 0.50-0. 65, P 0. 010-0. 025, and S 0. 005-0. 028. The plates with thickness of 8. 7 mm in which the ferrite grain size is smaller than 8μm have been produced by special de- formation process in the laboratory. Furthermore, the trial production of special plain carbon steel plates of 16-25 mm in thickness and 2 000- 2 800 mm in width with fine grained ferrite has been successfully carried out in the Shougang Steel Plate Rolling Plant. The ferrite grain size is 5.5-7μm in the surface layers and 9.5-15μm in the central layer respectively. The yield strength is 320- 360 MPa, tensile strength is 440-520 MPa and the elongation is 25%- 34 %. It is very important for the rolling plants to improve the low carbon steel plates＇ mechanical properties. The results show that the ferrite grains in the surface layer can be refined effectively by the appropriate rolling process, and the strength can be also increased.     

普通碳素钢超细晶微观组织的特征分析

 用Gleeble热模拟实验机对2种不同成分的普通碳素钢进行实验，实验的过程为：以10 ℃/s加热到950 ℃，保温2 min，再以10 ℃/s的冷速降到变形温度(900~600 ℃)，以10 s-1或30 s-1的变形速率进行了变形量为80%的变形，变形后立即水淬。通过光学显微镜和透射电镜观察分析，确定了普通碳素钢利用形变诱导铁素体相变获得的超细晶组织及两相区变形获得的超细晶组织的典型形貌特征。     

我国东南沿海城市地下建筑氡浓度分布

为了解东南沿海城市地下建筑氡浓度的分布，用固体核径迹法(SSNTD’s)，分别在春、夏、冬3季对沿海7城市地下建筑室内氡浓度进行调查。结果表明，福州具有最高的平均氡浓度，上海的平均氡浓度最低。季节的变化对地下建筑室内氡浓度有影响，各城市氡浓度平均值夏季最高、冬季最低。各城市夏季氡浓度与该城市的年均值的比值与城市中各测点氡浓度之间的离散度有一定的相关性。夏季地下建筑室内氡浓度高的城市，它的平均氡浓度受某些具有高氡水平测点的影响大。