Silicate Island Formation in Gas Metal Arc Welding

Because formation of silicate islands during gas metal arc welding is undesirable due to decreased productivity and decreased quality of welds, it is important to understand the mechanism of the formation of these silicate islands to mitigate their presence in the weld. The effects of welding parameters on the silicate formation rate were studied. Results showed that the applied voltage and oxidizing potential of the shielding gas were the parameters that most strongly influenced the amount of silicates formed on the surface of the weld bead. High-speed video was used to observe the formation of silicate islands during the welding process, which showed that the silicates were present at each stage of the welding process, including the initial melting of the wire electrode, and grew by coalescence. A flow pattern of the silicate islands was also proposed based on video analysis. An electromagnetic levitation system was used to study the growth kinetics of the silicate islands. Silicate coverage rate was found to increase with increasing oxidizing time, increasing oxidizing potential of the atmosphere, and increasing content of alloying elements except for Ti.

Experimental research on latent heat characteristics of binary mixed molten salt

At present, thermal storage is considered as one of the key technologies to alleviate the problem of instability and intermittence for renewable energy. Due to relatively high latent heat, latent heat storage by molten salt is considered to a potential technology. Because of the restriction of different thermophysical parameters, the application of latent heat storage by molten salt has many technical obstacles. So, it is an urgent work to find a better mixed molten salt formula with comprehensive thermophysical properties. In this paper, we selected halogen salts (NaCl, NaF) and alkali (NaOH) to prepare binary mixed molten salts. From the results, for the mixed molten salt of NaCl-NaOH, NaCl:NaOH=1:9 has a maximum latent heat value of 301.2J/g. The initial melting temperature is about 200°C. With the increase of the mass ratio of NaCl, the termination melting temperature increases firstly then decreases. For mixed molten salt of NaF-NaOH, NaF:NaOH=1:9 has a maximum latent heat value of 199.5J/g, the initial and termination melting temperatures are about 265°C and 380°C, repectively. The latent heat value of NaCl-NaOH and NaF-NaOH mixed molten salts decreased with the increase of the mass ratio of halogen salts.

Mathematical Model for the Harmonic Analysis of Electric Arc Currents and Voltages in an Electric Arc Furnace

This paper analyzes how the relative effective total odd and even current and voltage harmonics of an electric arc in a furnace correlate with the thermal time constant of the arc, with the valve effect, and with the asymmetrical operation. The furnace circuit model was used to theorize upon the effectiveness of using even harmonics data to diagnose the charge melting stage during initial melting; and odd harmonics to analyze the late stages. The results of mathematical modeling helped draw guidelines for the design of the charge melting diagnosis unit to be part of the electrical parameters control system; the unit design depends on the furnace type. The results could be of use in research of better control algorithms for electric arc furnaces and lade furnaces with a focus on reducing the energy costs of producing molten steel.

Experimental Study on Freeze-Thaw Cycle Duration of Saturated Tuff

The freeze-thaw duration is one of the important factors affecting the change of rock properties. However, this factor has not formed a unified standard in the freeze-thaw cycle test. This study uses saturated tuff samples taken from eastern Zhejiang, China, as research objects to explore the change law of the time required for the rock to reach a full freeze-thaw cycle. Measured results show that the total duration of the freeze-thaw cycle presents an increasing power function with the increase in the number of freeze-thaw cycles. The freezing process is divided into three phases: initial freezing, water-ice phase transition, and deep freezing. The melting process is also divided into three phases: initial melting, ice-water phase transition, and deep melting. The time required for the ice-water phase change stage of the melting process does not change with the increase in the number of freeze-thaw cycles, while the other stages increase as a power function. The proportion of duration of each stage in the freezing process does not change with the increase in the number of cycles. By contrast, the duration proportion of the initial melting phase in the melting process decreases, and the deep melting phase increases. Experimental results of the freeze-thaw cycles of tuff demonstrate that the freeze-thaw duration of the freeze-thaw cycles within 40 times can be set to 9 h. The freezing and melting processes are 6 and 3 h, respectively.

High-pressure elastic properties of dolomite melt supporting carbonate-induced melting in deep upper mantle

Deeply subducted carbonates likely cause low-degree melting of the upper mantle and thus play an important role in the deep carbon cycle. However, direct seismic detection of carbonate-induced partial melts in the Earth’s interior is hindered by our poor knowledge on the elastic properties of carbonate melts. Here we report the first experimentally determined sound velocity and density data on dolomite melt up to 5.9 GPa and 2046 K by in-situ ultrasonic and sink-float techniques, respectively, as well as first-principles molecular dynamics simulations of dolomite melt up to 16 GPa and 3000 K. Using our new elasticity data, the calculated VP/VSratio of the deep upper mantle (∼180–330 km) with a small amount of carbonate-rich melt provides a natural explanation for the elevated VP/VSratio of the upper mantle from global seismic observations, supporting the pervasive presence of a low-degree carbonate-rich partial melt (∼0.05%) that is consistent with the volatile-induced or redox-regulated initial melting in the upper mantle as argued by petrologic studies. This carbonate-rich partial melt region implies a global average carbon (C) concentration of 80–140 ppm. by weight in the deep upper mantle source region, consistent with the mantle carbon content determined from geochemical studies.

The impact of calcination on changes in the physical and mechanical properties of the diatomites of the Leszczawka Member (the Outer Carpathians, Poland)

The work concerned the effects of the thermal treatment of diatomites from the Jawornik deposit (an example of the diatomites of the Leszczawka Member of the Polish Outer Carpathians). Five distinct lithological varieties were subjected to calcination at 600°C in ambient air.The thermal impact induced the following changes to the rocks. Their overall rock porosity increased, most distinctly in the initially softer varieties, and the internal pores of the siliceous frustules themselves usually became larger due to the initial melting of the silica phases. Most of the diatoms, quartz and feldspars cracked as a result of their brittle fracturing under compressive strain resulting from substantial and differing size changes of growing grains. Clay minerals were thermally transferred, changing their volume. The organic matter dispersed through-out the diatomites was partly oxidized and removed. At the same time, the structure of the rocks was strengthened, as confirmed by an increase in their microhardness. The microhardness of soft and porous diatomite varieties increased considerably on heating, but that of the hard and compact variety changed to a smaller degree. The increase is directly related to the content of the clay minerals. The impact of other mineral components was not detected. The calcination of lithologically diversified diatomites provided the mineral with raw material with deicing and antisliding properties. The technology of its production has been determined by the authors and submitted as a patent.

Development of a new method for identifying species affiliation based on forensic hair examination

The aim of the research was to develop a method for determining the species affinity of animal hair by determining its melting temperature. The research material was selected from hair samples of livestock and wild animals. We investigated 170 hairs of 16 animal species and humans. The hair melting point was determined by an automated system for melting temperature determination Opti Melt (MPA100). In the present study, we suggest that species affiliation can be effectively determined by examining physical properties of hair, in particular by determining its melting temperature. The hair melting temperatures for different animal species are in different ranges, but the initial melting points for hair of certain animal species are similar. For example, the initial melting point for cat, sheep, hare, rabbit, and rat hair ranged from 100 to 111 ° C, and the hair of the wolf, bear, and fox began to melt at 139.2 to 141.2 ° C. The results of this research make it possible to determine the species affinity of animals according to their hair melting temperature, which had not been done before. The proposed method yields rapid results and can be used as an auxiliary method in ambiguous cases in which data obtained by microscopic examination are insufficient. It will greatly facilitate the work of forensic specialists, enriching the arsenal of available methods.

Barytová mineralizace v granodioritovém porfyritu z Bělovsi u Náchoda (orlicko-sněžnické krystalinikum, Česká republika)

A new occurrence of baryte mineralization at Běloves near Náchod is bound to a steep NNE-SSW trending fissure in a dyke of granodiorite porphyrite, which cut phyllites of the Nové Město Group (Orlica-Sněžník Crystalline Complex). The mineralization is composed of three generations of baryte differing in Sr contents (~0.10 apfu in the oldest generation, ~0.003 apfu in the youngest generation) and small amount of hematite. The primary fluid inclusions in baryte belong to type L and L+V; the variable phase proportions are probably caused by postdepositional damage of part of the present fluid inclusions. The wide range of temperatures of both initial melting (-40 to -1 °C) and final ice melting (-0.3 to -12.3 °C) suggests involvement of fluids with very variable salt systems and salinities. The δ34S values of baryte range between +5.5 and +7.1 ‰ CDT. The mineral composition, chemical composition of minerals and fluid inclusion data suggest that the studied mineralization is similar to Late Variscan vein baryte and mineralizations of the Bohemian Massif. The source of fluids is interpreted in evaporated fresh waters of Permian lakes, which occurred in the adjacent Krkonoše Piedmont Basin during the Permian.

Two genetic types of pseudotachylytes

The study of two varieties of pseudotachylytes (PST) in granitoids of the Riphean complex on the Barents Sea coast of the Kola Peninsula (Rybachii and Srednii peninsulas) and in metapsammite of the Paleoproterozoic complex in the Northern Ladoga region by a few independent analytical methods has made it possible to establish that they belong to different genetic forms, such as mechanically crushed rocks and melting products, respectively. As for the melting differences, we have given a detailed description of the mineral and material transformations of the original rock into the PST glass matrix and obtained evidence for the initial melting out of the micaceous eutectics with its subsequent shift to the granite type. The conclusion has been made on the most likely formation of molten PST due to frictional rock melting under rapid rise of its blocks from a depth of 12–15 km to the crustal surface (less than 3 km) along the faults of presumably seismogenic nature. It is suggested that crushing and frictional melting can be complementary, rather than mutually exclusive processes, and the formation of molten PST is commonly preceded by the mechanical rock crushing stage.