Advanced Materials Research Vol. 1088

Abstract: A heat transfer and solidification model of slab continuous casting process was developed, and the nail-shooting experiments were carried out to verify and improve the prediction accuracy. The comparison between the simulation and the measurements results showed that, there exists difference between the model predicted liquid core length and the calculated liquid core length according to the measurement results of the solidification shell thickness. In the present study, the value of constant a in the heat transfer coefficient calculation formula was corrected through back-calculation, results showed that, the suitable value of a is 31.650, 33.468 and 35.126 when the casting speed is 0.8m·min^-1, 0.9m·min^-1 and 1.0m·min^-1 respectively, which can meet the liquid core length of the measurement results. The developed model built a foundation for the application of dynamic secondary cooling, and dynamic soft reduction.

Abstract: With the processes of solution doping and hydrogen reduction process, the raw materials APT powder was converted into the tungsten with calcium additive. Micro-morphology, micro-structure, the existing form of element calcium and their distribution were examined by SEM, HRTEM and EDS. The results show that Element calcium is mainly in the form of CaWO₄ in tungsten oxide powder and has two calcium tungstate forms which are CaWO₄ and Ca_4.26W₁₀O₃₀ in reducing tungsten powder. The Ca-W-O particles are embedding in the tungsten powder particles; the rest distribute between the tungsten powder particles.

Abstract: Hot rolled mild steel was corroded in air, Ar/0.2%SO₂ and N₂/0.4%H₂S gases for 20 and 50 h. The corrosion in air at 800 and 1000°C resulted in the formation of Fe₂O₃/Fe₃O₄/FeO layered scales from the surface. The corrosion in Ar/0.2%SO₂ gases resulted in the formation of (FeS, Fe₂O₃, Fe₃O₄, FeO)-mixed scale at 800°C, and (Fe₂O₃, Fe₃O₄, FeO)/FeS layered scale at 1000°C. The corrosion in N₂/0.4%H₂S gases at 650 and 750°C led to the formation of (Fe₂O₃, Fe₃O₄, FeO)/FeS layered scales.

Abstract: The effects of environmental factors on the electrochemical behaviors of the materials 52M and 316L taken from a dissimilar metal weld exposed to high temperature primary water of pressurized water reactor (PWR) nuclear power plants were studied experimentally, mainly on the effects of impurities chloride and sulfate in water, temperature and dissolved oxygen on the polarization curves, in order to provide fundamental data for relevant research and development. The results showed that doping chloride and sulfate into the water caused the rise of the tendency to pitting and general corrosion tendencies of both materials. With the rise of temperature from 160 °C to 290 °C, the tendencies to corrosion in anodic condition increased. The rise of the dissolved oxygen led to the rises of both the corrosion potentials and also the tendencies to corrosion.

Abstract: Microstructure and mechanical properties of automobile beam used BS700MC low carbon micro-alloy steel welding joint were investigated by cold crack sensitivity, microhardness test, bending, impact, tensile and metallographic analysis. The results showed that the BS700MC steel has better crack resistance, and without heat treatment before welding with the WH80-G welding wires. The microstructure of joint’s weld seam is acicular ferrite, very little bainite and proeutectoid ferrite. The hardness value of weld seam zone is 380 HV and is the same as that of base metal. But the lower of weld joints rigidity has obvious fluctuations, and the HAZ appears softened phenomenon. The welding joint has good impact toughness only between 20 and minus 20 degrees Celsius.The tensile strength of BS700MC welded joint reaches 815 MPa, 97.1% of base metal, fracture position in HAZ. Tensile fracture morphology is mixed type indicating dimple and cleavage steps, and welding joint have good comprehensive mechanical properties.

Abstract: The focus of this study is on development of alternative manufacturing processes for potential high temperature magnesium-aluminium-strontium alloys. The effect of external pressure on tensile properties of squeeze cast Mg-Al-Sr alloy was investigated. Four different applied levels, 0, 30, 60 and 90 MPa, were employed to exert on a Mg-6 wt.% Al – 0.5 wt.% Sr alloy during squeeze casting. The results of tensile testing indicate that the ultimate tensile strength (UTS), yield strength (YS) and elongation (E_f) of the squeeze cast Mg-Al-Sr alloy increase with increasing applied pressure level. The microstructural analysis and porosity measurements suggest that the tensile property enhancement resulting from applied pressure should be attributed to microstructure refinement and porosity reduction of the squeeze cast alloy.

Abstract: The isothermal hot compression tests of Q235 steel over a wide range of temperatures (1023-1123 K), strain (0.7) and strain rates (1、5、10 s⁻¹) were performed on Gleeble-1500 system. The results show that when the deformation temperature is constant, as the strain rate increases, the flow stress also increases; Use the JC model to establish constitutive relation equation with true stress-true strain curve. And compare the prediction value of the constitutive relation equation with the experimental values, the relative error between the two is within the allowable range, indicating that the JC model constitutive relation equation applicable for the thermal deformation of Q235 steel.

Abstract: The semi-solid thixo-extruded process of AZ91D magnesium alloy with 9 % plastic deformation was investigated. The effect of isothermal time on the thixo-extruded formability of AZ91D magnesium alloy was analyzed. The relationship between isothermal time and microstructure, mechanical property was also researched. The results showed that with increasing the isothermal time from zero to 60 min on 575 °C, the filling distance was increased firstly and then decreased, the solid volume fraction was decreased firstly and then increased, the tensile strength and elongation were also increased firstly and then decreased. However, the increasing isothermal time would lead to decrease of shape factor but the coarsening of particle size. When the isothermal time was 30 min, the solid volume fraction was lowest and the filling distance was greatly increased obviously.

Abstract: Successful employment of advanced tool steel in engineering applications is related to its ability in terms of meeting service life requirements and fabrication with proper dimensions. Deep cryogenic treatment may be used to produce advanced tool steel by simultaneously increasing toughness, strength, and hardness. Twelve sets of specimens were tested in this paper, 9 of which were deep cryogenic treated and then tempered. Tensile properties, hardness, X-ray diffraction, and scanning transmission electron microscopy were applied for macroscopic and microscopic investigations. The best results of simultaneous improvement in toughness, hardness, and strength were obtained for 36 h soaking time and 1 h tempering time.

Abstract: In this paper analysed the forms of heavy metals (Zn Pb Cd and As) of the Smelting Slag for Lead and Zinc,using BCR sequential extraction. Different chemical morphological of heavy metals have different activity and harmfulness. Migration and Utilization of heavy metals were decided by the existent form of heavy metals in the soil,which influenced Bioactivity and Toxicity. The results show that the main forms of Zn and Cd are Oxidizable and Residual fraction, and Pb mainly occurred in Oxidizable and Reducible fraction. however, As mainly occurred in Residual fraction, which the percentage of reachs 99.56%. According to the percentage of fractions extracted in total content (As is 0.44%, Zn is 14.7%, Pb is 85.98%, Cd is 48.86%),the latent ecological risk of heavy metals varied in the descending order of,Pb Cd Zn and As.