Surface subsidence has some peculiarities for the mining of the Han jia wan coal mine. Based on the surface movement observation of 2304 working face in Han jia wan coal mine, mining strata movement parameters are analyzed, the main factors which influence the formation of surface cracks in the gob are proposed and the failure mechanism of surface movement and deformation are studied for the mining of shallow coal seam and thick loose bed. Correlative parameters are presented and scientific basis is established for the coal mining under buildings, rail and water and the leaving of the safety pillar in the future.
Molybdenum (Mo) film is deposited by Ion Beam Assisted Deposition (IBAD) on the 316L steel substrate surface in this experiment. The micro structure and nanohardness of the film are tested by Scanning Electronic Microscope (SEM) and nanoindentation tester. The tribological behaviors of Mo film under ZDDP and MoDTC lubrication are evaluated by SRV test machine. The tribo-film formed on the worn surfaces is investigated by X-ray photoelectron spectroscopy (XPS) to find out the tribological mechanisms between the Mo film and the two additional additives. The result shows that Mo film not only has friction reduction property but also has wear assistant property under ZDDP and MoDTC lubrication. As element Mo has advantage on promoting the deposition of these two lubricating additives.
For C-Si-Mn low carbon HSLA(High Strength Low Alloyed) steel, the influence of microstructure and properties were researched on the different annealing processes. The result showed that the microstructure at room temperature of the steel were polygonal ferrite, island martensite and punctate bainite. With the increase of the annealing temperature, the content of martensite and bainiteincreased and the content of ferrite decreased. Accordingly, tensile strengthincreased from 1069MPa to 1498MPa, and the elongation decreased from 13.8% to 5.1%. With the increase of the overaging temperature, tensile strength decreased from 1315MPa to 1152MPa, and the elongationincreased from8.5% to9.8%. Finally, the optimum annealing process obtained that the annealing temperature was 820°C for 80s, slow cooling to 680°C, water quenching to room temperature, the overaging temperature was 280°C for 300s and air cooling to room temperature. The material obtained higher tensile strength and better elongation.
Phase transformation of austenite continuous cooling process in low carbon high strength sheet steel has been researched by DIL805 thermal mechanical simulate. The Austenite continuous cooling transformation (CCT) diagram of steel has been determined by dilatometry and metallography. With the increase of cooling rate, ferritic transformation, perlitic transformation, bainite transformation and martensitic transformation have produced in the organization. Mathematical equations of phase transformation point-cooling rate and phase variable-cooling rate have been established and phase transformation model of high fit degree has been gained by regression calculation. The results show that calculated value and experimental value are nearly similar, so the phase transformation model is feasible.
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