摘要: The stamping process of the tailor welded blank(TWB) was simulated by the software of DYNAFORM. The finite element model of a boxy part was founded, and the forming of different thickness and properties of the material was studied. Meanwhile, the influence of weld seam on forming result was analyzed. The results show that the weld seam model which founded by real properties can describe the plastic deformation and strain distribution more exactly in the forming process.
摘要: Because the dynamic soft reduction of continuous casting process is based on the computation of the solidification end point, using model to simulating the steel solidificating process is more and more interesting. Especially, the influence of the heat flux to the solidification end point is needed to research thoroughly. In this paper the heat transfer model for the simulation of the solidification of steel droplet is established. The simulation reveals that the steel droplet (the radium is 7.2 mm) is solidified quickly in 4.3 seconds on water cooling copper plate, and in 3 seconds there is half of the droplet is frozen to solid. If there are materials resisting heat transfer inserted between cooling plate and liquid steel, the solidification end position would be moved to the deeper place below the shell in obvious extent, and the influence of heat flux to the ratio of mushy zone is weaker than that to solidification end point position.
摘要: Effect of bismuth on the microstructure and performance of Cu-Se-Bi brass were studied. The microstructure analysis and fracture observation indicated that the content of bismuth has obvious effect on the foundry property of Cu-Se-Bi brass. The bismuth distributes on the boundary of α and β phrase and when the content of bismuth is below 1.0wt%,bismuth freezes on the phrase boundary in form of granule; when the content of bismuth amounts to 2.0wt%,bismuth presents in form of blocks; while when the content of bismuth is beyond 2.5wt%,bismuth lies on the phrase boundary in form of continuous films. The solidification mechanism of bismuth in Cu-Se-Bi brass was discussed through the thermodynamics analysis.
摘要: The age hardening process for permanent mold samples of Al-7Si-0.3Mg cast alloy has been investigated by hardness measurement, differential scanning calorimetry (DSC), transmission electron microscope (TEM) and electron probe micro analyzer (EPMA). Age hardening results show that the age hardening response of Al-7Si-0.3Mg alloy is independent on cooling rate. There is a hardness value decrease about 10 HV after T4 treatment. Hardness value after as-cast aging at 150 °C for 20 h is just a little smaller than that after T6 treatment for permanent mold samples. The precipitation behaviors during T6 treatment and as cast aging treatment have been analyzed by DSC analyses. The hardness measurement results have been discussed by analyzing the precipitation behaviors and the Mg and Si concentration in α (Al).
摘要: The numerical simulation model of rapid solidification splat-quenching CuCr25 alloys was built in this paper. The vacuum chamber, cooling cooper plate and sample were taken into account as a holistic heat system. Based on the heat transfer theory and liquid solidification theory, the heat transfer during the rapids solidification process of CuCr25 flakes prepared by splat-quenching can be approximately modeled by one-dimensional heat conduction equation, so that the temperature distribution and the cooling rate of the flake can be determined by the integration of this equation. The simulative results are coincident very well with the experimental results for the microstructure of rapid solidification splat-quenched CuCr25 alloys.
摘要: As an important aeronautical assembly materials, such as aeronautical gas turbine and turbine plate et al, K4169 alloy has enough high ability of resistance to high temperature deformation and a long low-period fatigue life when working, and its grain structure should be equiaxed dendrite as fine as possible in casting. Chemical grain refinement method was used to refine K4169 alloy to satisfy the demands mentioned above. By using new intermetallic compound grain refiners, chemical grain refinement casting technology was carried out to refine K4169 superalloy. The results show that the grain morphology has been transformed from dendrite to granulation, the average principal axis length of the primary dendrites has been shorted and the segregation ratios of main alloy elements mitigate with the decrease of grain size in fine-grained castings, which indicates the remarkable effects of grain refinement. In addition, basing on the model of equiaxed dendrite growth solute diffusion, continuous nucleation model, dendrite tip growth kinetics model and cellular automata (CA) technique to coupled simulate the grain structure formation process of K4169 alloy in chemical grain refinement casting, which agreed very well with experiments results, this will do much contribution to the theoretic base for studying high temperature mechanics performance and performance of resistance to corrosion of K4169 superalloy.
摘要: Based on the Al-O-N phase stable diagram and adopting inverse reaction sintering process, corundum-silicon nitride composite refractories were prepared using corundum, silicon nitride, clay and aluminium powder as the main starting materials. The specimens were sintered at 1600 for 3 hours under air atmosphere with different oxygen partial pressure obtained by addition of different amount of aluminium powder. The effects of aluminium powder additions(0, 4wt.%, 8 wt.% and 12 wt.% respectively) on the hot modulus of rupture were investigated .The phase composition and microstructure were tested by means of XRD, SEM and EDAS.The results showed that aluminium would be oxidized, nitrided and displaced as aluminium powder increased during sintering, which reduced the oxygen partial pressure in the specimen. The hot modulus of rupture (HMOR) increased considerably due to large amounts of fibrous sialon formed.
摘要: The effects of pulsed magnetic field on the solidified structure of pure Mg were investigated. Fine uniform equiaxed grains are acquired in the whole ingot from the PMF treatment, in contrast with the coarse columnar grains observed in conventional casting, and the average grain size is refined to 260 m with a 5Hz PMF treatment. The mould size also affects the grain refinement and the most suitable inner diameter of the cylindrical mould is set at 50mm. Pulsed magnetic field increases melt convection during solidification, and the violent agitation causes warmer liquid to fracture the tip of columnar dendrites or to break off dendrite branches and promote the formation of an equiaxed structure, with the broken pieces transported into the bulk liquid acting as nuclei.
摘要: In recent years, high chromium cast irons have been widely applied in many fields because they have high hardness and abrasion resistance. However, high chromium cast irons are also expensive because much alloying elements, such as chromium, molybdenum and nickel, are added into them. In order to resolve above question, a new abrasion-resistant steel with high boron content was developed in this paper. The new high boron steel, with 0.6%~0.8%B and 0.65% C, was prepared using sand casting method. The microstructure and mechanical properties were researched. The results show that the solidification microstructure of as-cast high boron steel consists of boride (FeB) and matrix composed of pearlite, ferrite, and bainite. And the borides distributes along grain boundary in the form of network. After quenching at 980°C and tempering at 250°C, the FeB transforms to Fe2B, and the matrix transforms lath martensite. The hardness of as-cast high boron steel is 43HRC, and its impact toughness is 5J/cm2. After heat treatment, they increase to 56 HRC and 7J/cm2, respectively, approximating that of high chromium cast irons. The new high boron cast steel have a potential in stead of high chromium cast irons
摘要: Low-chromium cast iron as the matrix, SiC particles as reinforcement, water glass sand in ordinary dry type, no negative pressure conditions, the use made of composite diffusion agent, prepared the surface of SiC particulate reinforced steel matrix composites. The results show that: SiC particles penetrate the surface of the composite material has excellent wear resistance, with the content of SiC particles increase the wear resistance of composite cast layer increased, when the SiC particle content of 20%, the wear resistance to achieve the best good. The hardness of up to 3000HV composite layer above. Smooth casting surface roughness, dimensional accuracy is more accurate, composite layer and substrate is good.