Papers by Author: Jun Fei Fan

Abstract: In strip casting process, surface wave and temperature distribution in the molten pool directly affect the process stability and the quality of products. In this paper, physical model and numerical model have been set up and simulated. It has been found that in the corner of the molten pool there is a large wave amplitude on the surface. However, in the middle of molten pool the surface wave is low. The temperature distribution of molten pool showed that the present feeding device need to be optimized.

Abstract: Being examined by tensile tests at 820°C with initial strain rates of 2.5×10-4 s-1, 5.0×10-3 s-1and 1.0×10-1 s-1, the hot-rolled spay formed high speed steel (SF-HSS) had superplastic properties. With έ=2.5×10-4 s-1and 5.0×10-3 s-1, the σ-ε curves indicate that there has occurred dynamic recrystallization at the later stage of deformation.The tensile elongation decreases monotonously with strain rate increasing. The strain rate sensitivity m =dlogσ/dlog έ is about 0.23. In the sub-surface of fractured SF-HSS samples with έ=2.5×10-4 s-1,, most of holes on the subsurface are observed to distribute near the carbides and arranged along the tensile axis direction. The interface between coarse carbides and matrix is very weak sites where the holes are easy to nucleate and connect to cracks during deformation. In the necked region, fine carbide particles on the grain boundary have pinned the slip of dislocations and formed dislocation wall inside the grain. Dynamic recrystallization and some climb of dislocations has occurred. The superplastic deformation mechanism with έ=2.5×10-4 s-1 was dislocation creep mechanism controlled by dynamic recrystallization. During deformation, the role of some carbide in the materials was to retard the grain growth and keep SF-HSS having fine equiaxed grain size and remain stable.

Abstract: The parameters of atomizer were obtained from the experiment. Based on the obtained parameters, a mathematical model was proposed to simulate the growing profile of billet during spray forming. The model included some process parameters which relate to the shape profile such as nozzle data, eccentric distance, rotation speed, withdraw speed and so on. After being compared with the billet shape of experiment, we got good consistent results between the simulation and experiment, it was found that the results of the simulation is in good consistent with that of the experiment.

Abstract: It is commonly considered that the character of atomizing gas-flowing field would affect breaking method of molten metal, liquid droplet size and mass distribution. It is one of the important factors which determine the microstructure and metallurgical quality of products. In this paper, three types of atomizers were designed and Pitot tube was used to investigate the steady state gas flow field generated by a close-coupled spray deposition atomizer. Through the study of atomization gas velocity distribution by simulation and experiment, the construction and gas flow dynamical property were introduced in this paper.

Abstract: The effect of hot rolling parameters on graphitization of a spray formed ultra high carbon steels(UHCSs) was described. The number of graphite stringers and graphite area fractions increased with the increase of rolling reduction. Graphite stringers nucleated at small pores and grew by carbon diffusion from adjacent austenite during hot rolling. Alloy contents, pores and hot deformation atγ+Fe3C phase range are the key factors for graphitization.The graphite stringers of UHCSs have little effect on tensile strength, but reduce the ductility at room temperature.

Abstract: The CuNi15Sn8 alloy has quite potential applications in the field of the electrical appliance industry. However, this alloy is prone to generate the segregation of alloying elements at the grain boundaries because of the high content of Sn element with the low melting point by conventionally processing route. Although the CuNi15Sn8 alloy can be obtained by powder metallurgy or mechanical mixing techniques, it is hard to avoid the formation of oxidation in the alloy. As compared with these techniques, spray forming technique has obvious advantages in preparing the CuNi15Sn8 alloy. The spray formed CuNi15Sn8 alloy has indicated that the elements of Sn and Ni were very uniformly distributed in matrix with the fine equiaxed grains. Influence of aging treatment on the microstructure and properties of spray formed CuNi15Sn8 alloy was studied.

Abstract: Through the probability simulation method, the statistical model of mass metal liquid droplets during metal spray forming process was developed and the ejecting process of molten steel was studied. The distribution of metal liquid droplets, their different initial velocity and the original appear location during spray forming were obtained based on the above computation. After made statistic and analyzed on large number of metal liquid droplets, the forming and motion of liquid drop in whole space were defined in detail, which provided the precondition and reference for further study of liquid droplets deposition process on substrate.

Abstract: The simulation software of compressible gas flow process in spray forming equipment was developed under three-dimensional cylindrical coordinates. When the gas flow strands sprayed from some definite angles into the atomizer chamber, they converged at the definite height in axial line then expanded outside which showed the jet current characteristic. The substrate stagnated the divergence jet strands of gas and then separated the flow strand into two big recycle zones in whole space. One of the recycle flow zone directed downwards, the other recycle flow zone, directed upwards and reached the inlet area, which is the main reason caused the bonding of small liquid drop in the delivery hole.

Abstract: The distribution of velocity field in single outlet tundish has been simulated through numerical solution of turbulent Navier-Stokes equation in conjunction with e − k turbulence model. The theoretical predicted results have compared with experimental ones, and excellent agreement between them has been achieved. Through comparing the computational data using coupled heat and flow method with that of using uncoupled method, it indicated that it’s necessary to utility the coupled heat and flow method in big size tundish since the thermal buoyance should not be ignored in the calculation.

Abstract: In the present paper, applied the experiential correlation, the gas holdup and distribution of two phase zone which formed by argon blown were determined. The flow variables of molten steel and turbulence parameters in the Ladle Furnace were estimated utilizing the results of frontal calculation and through numerically solution momentum Navier-Stokes equation in conjunction with k-εturbulence model. Several different spray styles including blowing through single hole, double holes, top lance were simulated and compared in this project.