Papers by Keyword: Melt

Abstract: The structure of multi-component metallic melts is presented. Typically, the phase composition of commercial melts is complex and these melts are nonequilibrium systems. The correlation between liquid and solid metallic states is shown. The principles of time-temperature treatment of steels and alloys are described. In all technologies investigated, the preparation of a melt by its temperature-time treatment leads not only to improvement but also to stabilization of the structure and properties of the metal from melt to melt.

Abstract: All the technologies of the melt quenching preparation ensure its time-temperature treatment to not only improve but also stabilize the metal structure and properties with every melt. The influence of annealing temperature of nanocrystalline alloy Fe_72.5Cu₁Nb₂Mo_1.5Si₁₄B₉ on the structure and magnetic properties has been investigated. The relation between numerical values of the coercive force, the initial magnetic permeability and the magnetic hysteresis loop rectangularity factor allows optimizing a mode of nanocrystalline alloy heat treatment.

Abstract: Based on the phase diagrams analysis, the activity model of Fe-C-B ternary system was established with the ion and molecule coexistence theory. The activities of Fe, C, B, Fe3C, FeB, FeB2 and B4C in melt were calculated by analyzing the model. We have researched the thermodynamic condition of boron oxide reducing with carbothermic method and analyzed the effects of CO partial pressure, B2O3 content and slag type for the lowest smelting temperature. In normal pressure, the carbon content is high in melt, so it needs 2000°C for decarbonizing and chrome remaining. When CO partial pressure is 0.1 kPa and CaO content is less 60%, the lowest temperature of smelting ferro boron could be below 1600°C.

Abstract: In this paper, melting process in a co-rotating twin screw extruder was studied based on two dimensional melting model of flow field cross section. Positive displacement conveying characteristic in the melting section was assumed and melting process of each section was regarded as the result of time evolution. Procedure of melting was analyzed according to experiments and numerical simulations, both indicating that solid materials in the flight zones would melt firstly and carcass wrapped in the middle of melt would be molten finally. Liquid fraction contours showed that flow of hot melt played an important role in the melting process of cross section. Four types of melting mechanisms were summarized, in which viscous dissipation heat was discussed in detail, showing that viscous dissipation contributed about 10%-30% to the total energy needed during melting. Screw speed affected viscous dissipation significantly, while heating flux of barrel had little influence on it.

Abstract: Based on the SrO-Fe2O3-FeO-SiO2-B2O3 system, the M-type strontium hexaferrites glass ceramics has been prepared through heat treating the melted glass. Using the aqueous solution solvent evaporation and melt method, we obtained the glass precursor of molecular-scale homogenously mixed compound. The precursor was completely melted in a lidded platinum crucible placed in an electric furnace at 1480°C for 1h and then annealed in a furnace at 550°C for 40min. The crystallization of the glass systems with different component has been systematically investigated by using X-ray diffraction (XRD), Transmission Electron Micrographs (TEM) as well as Vibrating Sample Magnetometer (VSM). It is found that Fe3O4 crystal precipitated during naturally cooling the melt from 1480°C to anneal temperature. Moreover, the hexaferrite glass ceramics with the main crystal phase of SrFe12O19 was obtained after heat-treated at 860°C for 2 hours. The magnetic properties of the obtained hexaferrite glass ceramics indicated that the saturation magnetization and the coercivity were 8.1A•m2/kg and 114KA/m, respectively.

Abstract: Problems of reactive diffusion at the solid phase and melt contact are studied theoretically. The rate constant is a fundamental parameter characterizing the dissolving rate at a certain configuration of experiment. Relationships between the solid phase dissolving rate, i.e. the solid phase interface boundary movement in the melt, and rates of growth of intermetallic phases in the metal (Cu) are observed. This procedure enables the creation of surface and subsurface layers of regulated thickness in metallic materials by means of reactive diffusion. The main intention was an experimental study of copper dissolving in melts of various solder alloys and the related reactive diffusion. We used Sn, SnCu, SnAgCu, SnZn and SnIn alloys as a solder material. The problems that need to be solved preferentially are emphasized. It concerns especially the determination of the rate constant of dissolving and verifying whether the proposed model equations can be used for this constant determination in cases of cylindrical and planar dissolving. Rapid growth of phases in the metal (Cu) and determination of the thickness of layers with these phases pose considerable time demands to X-ray microanalyses (WDX, EDX, BSE, SEM) of specimens after their long-time heating.

Abstract: Based on the SrO-Al₂O₃-Fe₂O₃-B₂O₃ system, the nano-ferrimagnetic glass ceramics has been prepared through heat treating the melted glass. Using the aqueous solution solvent evaporation and melt method, we firstly obtained the molecular-scale homogenously mixed compound. And thus the glass specimen was produced by naturally cooling the batch melts. The crystallization of the glass systems with diffirent component has been systematically investigated by using X-ray diffraction (XRD), Thermo gravimetric (TG), Differential Thermal Analysis (DTA) as well as Vibrating Sample Magnetometer (VSM). It is found that Fe₃O₄ crystal precipitated during naturally cooling the melt from 1500°C to anneal temperature. Moreover, the nano-ferromagnetic glass ceramics with the main crystal phase of SrFe₁₂O₁₉ was obtained after heat-treated at 865°C for 2 hours. The size of crystal was 20-50nm. The magnetic properties of the obtained ferromagnetic glass ceramics indicated that the saturation magnetization and the intrinsic coercivity were 32A•m²/kg and 236KA/m, respectively.

Abstract: From the rheological theory, the combination of the rheological characteristic of melt spinning and principle of spinning, the paper researches the mathematical model of the velocity distribution and shear rate distribution when the melt flow in composite spinning sheath-core orifices. According to the mathematical model, the melt flow velocity and pressure characteristic of the composite spinning micropore are researched with the software of CFD-Fluent. The results for the design of composite spinning technology and components provide a good theoretical basis.

Abstract: Attapulgite(AT) was modified by grafting with butyl acrylate(BA) via polymerizations initiated by Gamma radiation. The polypropylene(PP)/AT nanocomposites were synthesized via melting extrude in a twin-screw extruder. The thermogravimetry(TG) and scanning electron microscopy (SEM) were used to assess the graft ratio of the hybrid materials and the dispersion of AT, respectively. Step-scan differential scanning calorimetry(SSDSC) was used to study the influence of AT on the crystallization and subsequent melting behavior. The results indicated that PP and PP/AT nanocomposites underwent multiple melting and secondary crystallization processes during heating. The melting behaviours of PP and PP/AT nanocomposites varied with the variation of crystallization temperature and AT content.

Abstract: In this work we give heed especially to the dominating process which is the solid metal A dissolving in the melt B. During the dissolving, the melt B saturates with the metal A and the process is influenced by convections which are characteristic for the given experimental configuration. A theoretical description of the kinetics of the solid phase dissolving in melt will be presented for the case of planar and cylindrical dissolving. The aim is to derive a relation for the interface boundary (t) movement in dependence on time and a time course of growth of the element A concentration in the melt B. There are problems with an accurate determination of the interface boundary movement after certain heating times of specimens, when it is observed experimentally, since intermetallic phases create in the original A metal at both the diffusion and cooling and some phases segregate at the solidifying melt cooling. The rate constant is a fundamental parameter characterizing the dissolving rate at a certain configuration. We present a theoretical description of dissolving of a long metallic cylinder submerged into a melt column and relations for the rate constant determination from the time of the whole metallic cylinder dissolution are derived. In our experiments were performed in which Cu was dissolving in the Sn melt for a Cu cylinder (wire) diameters 0.8÷2.5 mm and the rate constant K (T = 350°C) was determined. Relationships between the solid phase dissolving rate, i.e. the solid phase interface boundary movement (t) in the melt and rates of growth of intermetallic phases in the metal A will be observed. This procedure enables to create surface and subsurface layers of regulated thickness in metallic materials by means of reactive diffusion.