Advanced Materials Research Vols. 415-417

Abstract: The boron is one of the important elements to amorphous alloy. Researched the basic reaction of direct reducing boron oxide, and drawn the thermodynamic status diagram. The reducing reaction is much more relation with composition activity of slag and melt. The boron distribution ratio between slag and iron was calculated and analyzed the main factors of slag basicity, compositions of alloy and reaction temperature for affecting boron distribution ratio.

Abstract: The influence of the coiling temperature, ranging from 550 to 570°C, on the morphology and the phase composition of the oxide scale formed on the microalloyed low carbon steel for automobiles after hot strip rolling was investigated. Physicochemical characteristics of the oxide scales were examined and their formation mechanism was discussed. Thickness of the oxide scale is in the range of 8-11µm and decreases with a decrease of coiling temperature. The microstructure and phase composition, XRD analysis shows a large amount of magnetite (Fe₃O₄) and some sparse hematite (Fe₂O₃) exist on the surface of hot rolled strip when the coiling temperature reduces from 570 to 550°C. The coiling temperature substantially affects the internal microstructure and magnetite phase.

Abstract: The VIPs consist of the glass-fiber core material and two types of envelope film. The glass fiber was fabricated by a centrifugal blowing process. The core material was prepared by the wet method. The thermal conductivities of the materials were measured by the heat flow meter. The microstructure of the envelope film was observed by scanning electron microscopy. The porosity ratio and largest pore size diameters of the core materials are 92.27% and 20μm, respectively. The thermal conductivity of the VIP is about 8-10 times higher than that of the core materials. The thickness of type I and II envelope films are 45μm and 400μm, respectively. The thermal conductivities of the type I and type II envelope films are 0.11W/(m•K) and 0.69W/(m•K), respectively. The thermal conductivity of the VIP with type II envelope is higher than that of the VIP with type I envelope, which is attributed to the different structures and thickness of the envelope film.

Abstract: Abstract. S890 steel is a Mo-Mn alloy system bainitic structual steel which is developed in recent years and its strength is more than 900MPa,this steel is the material of hydraulic support possessing high-performance in coal mine.The continuous cooling curve of S890 steel was determined,microstructure and hardness of this steel in various cooling rate were analysised in the paper.Results have shown that:S890 steel has good quenching degree and quench-hardenability,and it can get steady microstructures which is mainly bainite over a broad range of cooling rate.

Abstract: Dynamic compaction is a widely used method for subgrade treatment due to its merit. This article presented example of dynamic compaction test in a liquid foundation project and investigated the relationship between settlement, ground heave and drop counts, the relationship between horizontal displacement and depth of soil, the relationship between drop counts, depth, horizontal displacement and pore water pressure, and the relation curve of pore water pressure and time during single point impact test. According to the conclusion before and after the testing, some appropriate engineering parameters were obtained and some advices were put forward.

Abstract: The ultra-microduplex structure was fabricated in the high carbon steel with a fully pearlitic structure after severe plastic deformation. The sizes of ferrite grains and cementite particles were about 0.4 μm and 0.1~0.2 μm, respectively. The mechanical properties of the ultra-microduplex structure were investigated using mini-tensile tests and the morphologies of fracture surfaces were observed with scanning electron microscopy (SEM). The results show that the tensile strength of the ultra-microduplex structure and the lamellar pearlite are almost at the same level, but after warm deformation, the yield strength was obviously increased and correspondingly, the elongation and the reduction of area were 19.2%, 32.1%, respectively, which are markedly higher than those of the lamellar pearlite. The tensile fracture of the ultra-microduplex structure is typical ductile fracture, however the fracture of original lamellar pearlite appears a mixture of cleavage fractures and quasi cleavage fractures.

Abstract: Based on the dynamic balance principle and contact fatigue properties of cylindrical gear pair, the influence factors of dynamics are researched and the meshing location for the maximum contact stress is accurately determined. Loading spectrum of contact stress is obtained by transient dynamic analysis. At the same time, the corresponding S-N curve for contact fatigue is described in a double logarithmic coordinate system. Then the finite element analysis on the contact fatigue life is carried out by ANSYS Workbench and safety factor for both gears are obtained. It has great significance for evaluating the reliability of the cylindrical gear pair.

Abstract: Hot rolled high strength Ti-Nb-IF steel sheet was used to study the effect of cold reduction ratio on the microstructures, mechanical properties and textures of experimental steel. The experimental results showed that the recrystallization has finished under different cold reduction ratio. The yield strength, tensile strength, elongation, the plastic strain ratio and strain hardening exponent were approximate 242MPa, 408MPa, 39.5%, 1.8, 0.26. With the cold reduction ratio increase, the textures strength increase, and the α textures have a trend with {111} texture. Therefore, the suggested the optimal cold reduction ratio is 75%, and it obtains optimally match of high strength and punching property.

Abstract: Steel storage rack structures have always been the mainly used type of those cold-formed thin-walled steel elements. Recently, it becomes more important to study its stability and bearing capacity. This paper selects a typical type of rack column-channel column and performs lots of analyzing work about overall buckling, local buckling and distortional buckling of perforated columns with different openings by using the finite element method.

Abstract: The microstructure and creep strength of 403Nb martensitic heat-resistant steel after tempering at 650°C, 680°C and 730°C were analyzed by SEM and TEM. Microstructural observation shows that 403Nb steel tempered at 650°C provides a finer lath structure and a smaller size of precipitates than that tempered at 680°C or 730°C. The dislocation density is also higher in 403Nb steel tempered at 650°C. The creep rupture strength of 403Nb steel tempered at 650°C is the highest among those tempered. The main creep strengthening mechanisms in 403Nb steel usually include precipitates hardening, dislocation hardening and sub-grain boundary hardening.