Advanced Materials Research Vols. 194-196

Abstract: Based on the equations of mass conservation, energy conservation and chemical reaction rates, a mathematical model of direct reduction for pure zinc oxide pellet containing carbon was built. On the basis of verifying the accuracy of the model by comparing calculated values with experimental results, the effects of furnace temperature, porosity and radius of pellet on the reduction were investigated. The calculated results revealed that the furnace temperature and the radius of pellet have significant effect while porosity has only a little. Thus it can be inferred that the rate-determining step for direct reduction in the pellet containing zinc oxide and carbon is heat transfer.

Abstract: The coke reaction index and solution loss reaction starting temperature were tested by the thermo gravimetric test. According to the relationship between the temperature and the index，a new test method, which evaluates coke high temperature properties by the coke solution loss reaction starting temperature, was put forward. The new method has many merits such as expediently operation and reliable results compared with the method and results of the national standard test.

Abstract: The effect of magnetic field on diffusion behavior of carbon in pure iron was investigated. The results showed that the magnetic field can accelerate the carbon diffusion when the magnetic field direction is perpendicular to the carburized direction, and this effect increases with the enhancement of magnetic field intensity.

Abstract: Dioxins are a kind of extremely toxic and Persistent Organic Pollutants (POPs). Sintering process has become one of the most dominant unintentional discharge sources. The dioxins synthesis pathway and mechanism being described, related research indicate that: in the low temperature sector (200-500ºС), chlorobenzene and chlorphenol are the representation precursors of dioxin’s precursor catalytic reaction, the dioxins formed in this temperature sector cased by the “de novo” under catalyst (like Cu²⁺) on the surface of smoke particles; high-temperature gas phase reaction mechanism of dioxins satisfied the first-order kinetic model, the formation of gas related with suitable precursors, it is the result of chlorinated precursors’ pyrolytic rearrangement like chlorobenzene and chlorophenol in the temperature sector 500-800ºС in the gas.

Abstract: Sheets of cold rolled (76%) IF steel were annealed at 650°C for 30min under a 12-tesla magnetic field. During the magnetic field annealing, they were placed at the center of the applied field respectively, being oriented differently with respect to the magnetic field direction. The results show that the high magnetic field annealing prevents the evolution from deformed {111}<110> texture component to recrystallized {111}<112> texture component at the initial stage of recrystallization. For the field annealed specimens, altering the specimen orientation to the magnetic field direction during annealing does not change the final annealing textures. The intensity of main {111} texture components presents a similar periodic variation with respect to the specimen orientation to the magnetic field.

Abstract: Silicon nitride presents good mechanical properties and thermal stability at high temperature. To investigate the mechanism of this unique feature demands a proper atomistic simulation, as the experiments have limitations in nano-scale characterization of chemical structure and the related properties. In this paper, the melt-quench method was used to generate the amorphous structure of silicon nitride, and then the corresponding mechanical properties were studied. The simulation results consist with the experimental results on radial distribution function and Young’s modulus.

Abstract: Along with the rapid development of the science and technology, the requirements of microstructure and properties for the bearing steel are more and more strict. The recrystallization behavior of hot deformed austenite in GCr15 bearing steel was systematically studied under the different deformation amount, deformation temperature and dwell time after rolling, the changes of microstructure and recrystallization percentage was analyzed. The research results show that the recrystallization behavior of hot deformed austenite in GCr15 bearing steel is more and more obvious as the deformation amount, deformation temperature and dwell time after rolling increase, the microstructure is more uniform, and the recrystallization percentage increases; When the deformation amount is 20%, the deformation temperature is 850°C and the dwell time after rolling is 10s, the recrystallization percentage is 32.09%, when the deformation amount is 45%, the deformation temperature is 950°C and the dwell time after rolling is 60s, the recrystallization percentage is 64.31%, comparing it to 32.09%, it increases 100.4%.

Abstract: The influence of sub-temperature quenching temperature on the strength and hardness of 65Mn steel during austenite inverse phase transformation is studied and the microstructure and property are analyzed. The results showed that in the range of 760~810°C , the strength and hardness of the 65Mn steel second sub-temperature quenched increased with quenching temperature increasing, reached the highest strength and hardness at 790°C quenching and then began to decrease. A small number of ferrite and ferrite dual-phase structure existed in martensite when quenching temperature was low. Fine martensite was obtained by second sub-temperature quenching due to the smaller austenitic crystal grain and austenitic nucleation sites. The mechanical properties of samples second sub-temperature quenched are better than that of conventional samples 830°C once quenched.

Abstract: The kind of ductile Ni-resist cast iron which will be used to exploit the exhaust manifold in First Automotive Works mainly contains up to 29 wt% Nickel, 4.9 wt% silicon and 1.7 wt% chromium. The main part of this study focused on the microstructure characterization of the as-cast condition and mechanical property at the condition of alternative thermal cycles. In the cast state, the alloy consists of the austentic matrix and carbides. The carbides contain M₆C and M₇C₃. And FeNi₃ phase is found in the austentic matrix. After alternative thermal cycles at 900 , the hardness value gradually descends from 203 HV to 170 HV.

Abstract: Fe-1.5Cu-1.5Ni-0.5Mo-0.3C alloy was prepared by powder metallurgy (P/M) warm compaction. Under the conditions of compaction pressures of 600 or 800 MPa and compaction temperature of 100 or 120°C , sintered in cracked ammonia atmosphere at 1120°C for half an hour, the researched alloy samples with higher properties could be prepared. The results show: when formed at a compaction pressure of 800 MPa and compaction temperature of 120°C , the alloy presented a sintered density 7.41g/cm³, hardness 88HRB, ultimate tensile strength 593MPa， yield strength 585MPa, and elongation 3.8%. Their mechanical properties, crack morphology and surface composition weres analyzed.