Advanced Materials Research Vols. 557-559

Abstract: The effect of rare earth element on structure and mechanical properties of SS400 steel were studied by metallographic examination, scanning electron microscope (SEM), tensile test and impact test. The results show that rare earth can refine microstructure of SS400 steel. Fracture is changed from cleavage to ductile fracture by adding RE to SS400 steel. And the mechanical properties of SS400 are improved. The impact toughness value of SS400 steel (containing 0.02 RE) increases by 39.66% at -40°C, and at 0°C the impact toughness value increases by 31.05%, respectively comparing with that of steel without RE.

Abstract: Fe - 9 to 12%Cr alloys are a material for the thick sections boiler components and steam lines of a power plant. The role Fe - 9 to 12%Cr alloys is becoming more prominent in the development of a new generation of Ultra-Supercritical (USC) Power Plant due to the target operating temperature is reaching 620 °C (893 K), in 100% steam condition as well as pressure in excess of 300 bar (30 × 106 Pa). In such condition, the integrity of Fe - 9 to 12%Cr alloys relies on the oxide scale formed during the time of exposure. However due to the high temperature and water vapor condition, it is a well known fact that, the formation of oxide scale is accelerated thus depleting the structural integrity of the Fe - 9 to 12%Cr alloys over the time. Studies show that not only the formation of protective oxide scale was suppressed but the formation of non-protective oxide scale was accelerated instead. Decades of studies done by various groups around the globe has yet to have consensual on the exact mechanism of this phenomenon. Initial stage oxidation of these alloys plays great roles in hope to understand the formation of oxide scale in water vapor condition at high temperature. This paper reviews previous research works to understand the initial stage oxidation of Fe - 9 to 12%Cr alloys at high temperature in water vapor condition.

Abstract: The oxidation resistance and high temperature mechanical properties of FeCrNi heat-resisting steel are analyzed and studied. The results show that the oxidation resistance of the heat-resisting steel is improved remarkably after adding RE. The value of oxidation rate of Sample 1 (without adding RE) is 1.71 times higher than Sample 2, respectively at 1423K. And the value of oxidation rate of Sample 1 is 1.4 times higher than Sample 2, respectively at 1473K. The fracture mode of heat-resisting stainless steel is typical cleavage fracture, but dimple fracture after adding RE into the steel. The high temperature mechanical properties of heat-resisting steel is improved obviously by RE. In comparison with heat-resisting stainless steel without RE, the reduction of area of heat-resisting stainless steel with RE is increased 26.27% at 1123K.

Abstract: A fire occurring at a building causes severe damages to its structural members and brings unexpected collapse. Therefore, the building regulation of each nation has to define fire resistance to prevent building collapse due to high temperatures. In general, the fire resistance of each structural member can be evaluated by two methods. One is prescriptive method that is guided by a specific building regulation containing fire resistance examples or by the application of new examples tested fire experimental procedures. The other is performance based fire engineering design. Being an engineered and scientific method, it utilizes the results obtained from the calculation of fire severities, temperatures of members and so on. The easiest way to evaluate the fire resistance of a steel member is to compare its limiting temperature and maximum temperature. Therefore, constructing the database of the limiting temperatures of structural elements is very important in performance based fire engineering design. This paper is to derive the fire resistance and limiting temperatures of rectangular hollow sections under loads.

Abstract: Three kinds of shear buckling parameters of corrugated steel web beam under high temperature of fire in different time are analyzed and the high temperature effect on structural steel property is taken into account, the expressions of local buckling parameter, overall buckling parameter and interactive buckling parameter are proposed and their variation trends with the high temperature change are analyzed, a recommendation is proposed in order to provide more accurate predictions for the load-carrying capability status of corrugated steel web beam under high temperature, the buckling parameters variation should be unbiased estimated above all. Numerical results show that high temperature has obvious effect on the buckling parameter changes of the corrugated web steel beam.

Abstract: Based on experimental investigation of precipitates behavior, formation mechanism on hot delivery crack of microalloy steel was analyzed by binding microstructure evolution and thermal stress changing. The results show that different conveied way and different hot charging temperature are effect significantly on precipitates behavior in charging slab. The hot delivery crack of microalloy steel was formed by resultant force of precipitates behavior, microstructure evolution and thermal stress changing. The microstructure evolution that it is the formation of pro-eutectoid ferrite omentum on austenitic grain boundaries in Ar1~Ar3 is the leading role on formation of hot delivery crack. It is supply conditions for precipitated particles distributed along the austenitic grain boundaries and formation of hot delivery crack of microalloy steel.

Abstract: Effects of pH value on the stress corrosion cracking (SCC) of super 13Cr tubing steel were investigated in 3.5% NaCl solution, that mechanics properties and fracture morphology and SCC resistance and stress corrosion cracking susceptibility index (kscc) were analyzed by slow strain rate tensile (SSRT) stress corrosion cracking experiment method and σ-ε curve and SEM. the results Effects of pH value on the stress corrosion cracking (SCC) of super 13Cr tubing steel were investigated in 3.5% NaCl solution, that mechanics properties and fracture morphology and SCC resistance and stress corrosion cracking susceptibility index (kscc) were analyzed by slow strain rate tensile (SSRT) stress corrosion cracking experiment method and σ-ε curve and SEM. the results showed that super 13Cr tubing steel has good properties of resistance stress corrosion cracking in acidic medium, effects of pH value on super13Cr tubing steel resistance stress corrosion was not very obviously in the acidic medium, with pH value decreased, super 13Cr tubing steel tensile strength decreased, elongation rate decreased, fracture area contraction ratio decreased, break time reduced, the tendency of the stress corrosion cracking increased. the stress corrosion cracking susceptibility index kσ and kε were all increasing, that increased degree of kε were obviously than kσ, effects of pH value on the plastic deformation of super 13Cr tubing steel were greater than tensile strength.

Abstract: Application of absorbing material mostly concentrated in the range of hard materials, flexible absorbing fabric made of iron fiber has important research significance in order to meet the special military environment. Morphology, micro-elements element type and content of the iron fibers were tested. The absorbing properties and spinning performance of iron and fiber were discussed. The results show that cross-section of iron fiber made of copper production was jagged and multiple channels exist in longitudinal, which is benefit for spin ability. Its morphology and composition of the fiber have a catalytic effect in absorbing properties.

Abstract: ZnO•SrO composite metal oxides were prepared via solid-state reaction and characterized by XRD. The catalysis of ZnO•SrO to PET depolymerization under microwave irradiation was studied, and the undepolymerized PET was analysed by Gel permeation chromatography(GPC). It is found that the catalytic effect of ZnO•SrO was optimum when the ratio of catalyst was 0.5%, and the rate of hydrolytic depolymerization of PET reached 93.13%. The degree of chain scission of PET depolymerization catalyzed by ZnO•SrO is deep to some extent under microwave irradiation.

Abstract: The corrosion processes and mechanisms of Q235A steel under wet-dry cyclic condition were studied using polarization curve compared with immersion samples, while, the corrosion morphologies and corrosion products of the steel samples were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The cathodic process of wet-dry samples was likely to be controlled not by the oxygen reduction, but rather by the reduction of corrosion products. During the drying process of the wet-dry sample, the electrolyte thickness decreased and chloride concentration increased. Oxygen would be much easier to diffuse into the interface of electrolyte/metal, which improved the cathodic reduction processes. Except for this, the rust itself took part in the reduction processes and hence increased the corrosion rate of the steel samples.