Advanced Materials Research Vols. 287-290

Abstract: The effects of direct quenching and tempering (DQ-T) process and conventional reheat quenching and tempering (RQ-T) processes on the microstructure and mechanical properties of a high strength low alloy steel were investigated. In the as-quenched DQ steel, prior austenite grains are elongated parallel to the rolling direction, whereas the as-quenched RQ steel mainly consists of equiaxed grains; The DQ process was found to enhance the hardenability of steel effectively. The tensile strength and yield strength of DQ specimen, were higher than that of RQ specimen. In contrast, low temperature toughness of DQ-T specimen was generally inferior to that of RQ-T specimen.

Abstract: Sandwich composite panel is a new developed building material applied in steel residential houses, but the theory and experiment of this panel is still limited. In order to study the influence of the boundary conditions and shear connector patterns on flexural behavior of the panels, two groups of panels were cast and tested. Failure modes of the test panels under the uniformed transverse load, load-deformation response, strains in two concrete wythes, crack loads and ultimate load-bearing capacity were recorded and analysed. Test results showed that different angles and distances of plane truss shear connectors affected the ultimate flexural strengths significantly. The strain curves of two concrete wythes revealed that the plane truss shear connectors of panels worked well to make the two wythes act as a solid slab. It is concluded that the sandwich composite panel is available in steel residential houses because of its economical and high flexural strength.

Abstract: As an important and mature technology of researching material properties, ac impedance spectroscopy has successfully applied in many discipline except for soil research. Based on the experiments using TH2828A wide frequency LCR meter (from 50 to 10⁶ Hz), the ac impedance characteristics with different water content of soil had been discussed. The results fully illustrate that the ac impedance is one of the basic property of soil,and the value of ac impedance parameter can be reflected the water content quantitatively. when using the fixed frequency to measure ac impedance of soil, it is most suitable as the frequency equals 10⁴ Hz.The measure method of ac impedance have no effect to physical properties and internal structure of soil.

Abstract: All Samples of alkaline-earth silicon oxynitride glasses were synthesized by conventional high-temperature melting reaction. The infrared spectra of all glasses were studied. The results show that the band between 800 and 1300 cm^-1 becomes wider and loss intensity with increasing N content. With the same starting N content, glasses prepared of different alkaline-earth oxides show different infrared spectra. The absorption bands of CaO-SiO₂-Si₃N₄, BaO-SiO₂-Si₃N₄ glasses are wider than SrO-SiO₂-Si₃N₄ glass.

Abstract: The use of magnesia-chrome refractories of the cement kiln can generate harmful hexavalent chromium in the environment and be hazardous to your health, so the study on the instead of magnesia-chrome refractories have become urgent issues. The raw material is made up of fused magnesite particles (particle size 0 to 3 mm), fine fused magnesite powder with the size less than 200 meshes and fine fused magnesia-zirconia’s powder with the size less than 320 meshes, polyvinyl alcohol and calcium lignosulfonate liquor being used as the combine. This paper discusses the effect of sinter temperature on sinter character of products.

Abstract: Pre-reduction shaft furnace is a typical gas solid countercurrent reactor, in which complex transport phenomenon exists between gas-solid phases. In the present paper, a mathematical model has been developed to simulate the actual pressure field of the shaft furnace, the gas flow field and the distribution of gas flow backwards. The simulation results of the pressure field indicate that the pressure is distributed uniformly at the same height in the furnace. The results of gas flow field indicate that the velocity of gas flow near the side wall is larger than that in the inner part, and a gas dead zone exists at the lower part of the shaft furnace. Comparing the volume of gas flow through the every DRI downcomers, it can be drawn that the gas flow from DRI downcomers near the gas export side is higher than the other side.

Abstract: Rolling friction and abrasion test of high NiCr indefinite chilled iron roll material was developed on Arms Abrasion Tester made in Japan. The results showed that among two groups of samples with laser surface remelted-strengthening, C2 group samples of higher laser power and quicker linear speed had higher wear-resistance, and №6 sample of C2 group has the best with 1.5 mm beam diameter, 240-250W power and 30 mm/s linear speed, its total wear extent of three work conditions was only 16.3mg, and its wear-resistance increased 34.8% compared with №3 sample which had the best wear-resistance in C1 group without laser surface remelted-strengthening,; and for contrast of average wear-resistance of three work conditions, C2 group increased 49.3% compared with C1 group, it was showed that the effect of laser surface remelted-strengthening on high NiCr indefinite chilled iron roll material were very evident.

Abstract: After heat treatment, 60Si2Mn spring steel liner failed before installation. Considering the actual production process, detail analysis of the failed parts by X-ray fluorescence spectrometry analysis, mechanical properties experiments, scanning electron microscopy and metallographic examination. Find the reasons which may lead the failure such as the inhomogeneous composition, uneven hardness distribution, surface decarburization and improper heat treatment process, etc.

Abstract: A water model of 1/4 linear scale for 210t RH has been established. RH circulation flow rate is measured by a velocimeter. The influences of lifting gas flow rate, snorkel inner diameter, injection depth and nozzle inner diameter on circulation rate were discussed. The dimension correlation has been calculated for the prediction of circulation rate. The results showed that the formula of circulation rate is 5.434×10^-6G0.356·D^1.254·d ^-0.106·H ^0.821. The best nozzles inner diameter in terms of circulation rate was 3mm.

Abstract: Experiments were conducted to study fly ash concrete (FAC) attacked by sulphuric acid. The cubes with dimensions of 100 mm were cast and immersed in sulphuric acid solution with different pH values of 2, 3 and 4, and tested at exposure times of 28 d, 56 d, 90 d, 150 d and 365 d respectively. The compressive strengths of concrete were tested, and the SO₄^2- contents of concrete at different depths were measured with powder samples by the chemical titration method. The results show that FAC has certain ability to resist corrosion of sulphuric acid though exposed surfaces were damaged at long-term exposure times, the concrete strength at same exposure time decreases with the increasing density of sulphuric acid solution, the SO₄^2- mainly contains in shallow layer of concrete while the content decreases obviously with the increasing depth of concrete. With the increasing density of sulphuric acid solution, phenomena of surface cement paste peeling off surface of concrete and crystal CaSO₄ separated out of concrete became seriously. The deterioration mechanisms of FAC attacked by sulphuric acid are discussed.