Melting Point Of Metal Research Articles

High Temperature Furnace for Melting Point Determination

This paper describes a device for determining by optical methods the melting points of metals, alloys, oxides, and other materials at temperatures up to at least 3000°C. The furnace is simple in design and requires only vacuum and electrical connections. There is no water cooling and the heating element is a disposable tungsten conical basket purchased from a commercial supplier.

電子ビーム溶接部の性質に関する二,三の研究

Chemical compositions, porosities and mechanical properties of electron-beam welds were studied of ractive and refractory metals, aluminium alloy, stainless steel and carbon steel by comparing with controlled atmosphere TIG welds and the following conclusions were obtained :(1) The contents of oxygen and nitrogen in titanium and zirconivm were changed neither by electron-beam welding (EBW) nor by TIG.By EBW, contents of carbon and oxygen in sintered niobium sheets, that of carbon in a sintered tantalum sheet and that of nitrogen in a type 304 stainless steel plate were considerably reduced.(2) X-ray radiographs of both EBW and TIG welds in sintered niobium, molybdenum and tungsten sheets showed usually many porosities in weld metal near the fusion line, while porosityfree welds were obtiand in vacuum melted sheets.Repeated electron-beam bead welding in sintered sheets was very effective in eliminating porosities in weld metals.(3) An element of which the partial pressure at melting point of a base metal is higher than about 10-2mmHg is likely to be vaporized during EBW in a vacuum of (1-5) × 10-5mmHg.(4) Subsize V-charpy impact values of commercially pure titanium, zirconium and Zircaloy-2 plates were generally far greater in EBW welds than in TIG welds.(5) Brittle behavior of arc welds of molybdenm sheets was not improved by EBW, probably because of grain coarsening in weld zone.(6) The joint efficiency of EBW, welds of a 1 mm thick 24 S aluminum alloy sheet was about 87% and much greater than 50 to 70% in TIG welds, owing to the very narrow width of weld metal and heat-affected zone.(7) The joint efficiency of EBW weld of a 6 mm thick 17-7 PH plate was 100% and was greater than 95% in TIG weld.

Some aspects of the thermal evolution of the earth

Empirical data relating to the thermal history of the earth are examined. Recent astronomic and geochemical evidence strongly suggests that the earth formed by accretion from an initially low-temperature gas-dust cloud of solar composition. The distribution of U, Pb, Th and K within the earth imply that it passed through a melting or partial melting process about 4.5 × 10 9 years ago. This conclusion is confirmed if the core is assumed to consist dominantly of iron-nickel. Formation of the core, which likewise occurred about 4.5 × 10 9 years ago would liberate sufficient gravitational energy to cause melting. Evidence in favour of melting is also provided by analogy with meteorites. An examination is made of possible causes of this early melting stage and it is concluded that gravitational energy is chiefly responsible. Radioactive heating does not appear to be important. A critical factor in the early heating and chemical evolution is the interaction of accreting dust falling with high velocity into the primitive reducing atmosphere surrounding the earth. Because of this interaction, a metallic phase is produced by reduction. The distribution of temperature within the earth 4.5 × 10 9 years ago will be given by the melting-point gradient. Recent data on the electrical conductivity of the mantle and the melting point of metals under high pressures suggest that the present temperature distribution is much less than the melting point gradient. This implies that the earth has cooled considerably. The inferred cooling is consistent with present data on the abundance of radioactive elements in meteorites and in the earth, and also with possible modes of internal heat transfer—particularly convection and radiation.

The melting point of osmium

In the literature the accepted melting point of osmium metal is reported as 2750°C. It has now been established that this value is low and a redetermination gives 3045 ± 30° C.

MoSi<SUB>2</SUB>サーメットの研究

Some basic properties of MoSi2 Cermet for refractory hard materials have been investigated. MoSi2 powder was prepared of pure molybdenum and silicon mixture by arc-melting in an argon atmosphere and subsequent crushing in a ball-mill. The preparation of MoSi2 Cermet was carried out either by hot-pressing in vacuum or sintering in vacuum subsequent to cold-pressing of mixture of MoSi2 powder and 5∼10% binder metals. Some physical and mechanical properties of the specimens were investigated. The results obtained were as follows: (1) The density and the hot-hardness of the specimens obtained by hot-pressing in vacuum are better than those of the specimens made by cold-pressing. (2) In general, these test indicate that the optimum sintering (hot-pressing) temperature for MoSi2 Cermet is lower than the melting point of the binder metal used. It was 1300∼1400°C for Ni and Co, 1350∼1400°C for Fe, and 1300∼1380°C for binder metal of stainless steel. The maximum density obtained by hot-pressing reached 99.2∼98.0% of the theoretical value. (3) These specimens have shown satisfactory resistance against 10% hydrochloric acid and 10% sulphuric acid, but a worse resistance against 15% nitric acid. (4) In oxidation tests at 1100°C the resistivity against oxidation was found decreased with increase of the amount of binder metals. (5) In general, the hardness in hot state is decreased with increasing the amount of binder metals. For instance, it was 150∼170 (Hv) at 850°C with 10% binder metals. (6) The thermal shock resistance is improved by increasing the amount of binder metals. (7) The moduli of rupture of these specimens average 27∼32 kg/mm2 at 800°C.

The heavy metal content of magmatic vapor at 600 degrees C

In order to test the feasibility of hypotheses of vapor transport as explanations of ore deposition, an attempt is made to calculate the composition of a vapor phase in equilibrium with a cooling intrusive at 600 degrees C. The proportions of the major constituents are estimated from Shepherd's analyses of gases obtained by heating igneous rocks, from Rubey's calculations of the total amount of volatile material given off by the earth, and from requirements of thermodynamic equilibrium with the minerals of intrusive contacts. Concentrations of volatile metals and metallic compounds in the vapor are calculated from thermodynamic data, assuming that the vapor is saturated with each metal and that equilibrium is maintained with the common metallic minerals found in contact-metamorphic zones and high-temperature vein and replacement deposits. For most metals the chlorides are the most abundant compounds in the vapor, but volatilities of the chlorides differ from simple vapor pressures because of equilibrium requirements.Neither sulfides, oxides nor native metals would have sufficient concentrations in the vapor to play a significant role in ore deposition. The lack of correlation between melting points of metals, their vapor pressures, and their maximum possible amounts in the vapor is proof that metallic melting points cannot be correlated with mobilization of the metals.Many common metals are present in magmatic vapor at 600 degrees in sufficient quantity to account for the formation of ore deposits. Differences in calculated volatilities provide a good explanation for the restriction of mercury and antimony to low-temperature deposits, and for the appearance of lead later than zinc in zonal and paragenetic sequences. Nevertheless, simple vapor transport cannot be a complete explanation for the origin of ore deposits. Outstanding difficulties are the very low volatilities of copper, silver, and gold, and the fact that manganese has a lower volatility than lead.

Measuring friction at high speeds

The present paper describes results of plate-impact pressure-shear friction experiments conducted to study time-resolved growth of molten metal films during dry metal-on-metal slip under extreme interfacial conditions. By employing tribo-pairs comprising hard tool-steel against relatively low melt-point metals such as 7075-T6 aluminum alloys, interfacial friction stress ranging from 100 to 400MPa and slip speeds of approximately 100m/s have been generated. These relatively high levels of friction stress combined with high slip-speeds generate conditions conducive for interfacial temperatures to approach the melting point of the lower melt point metal (Al alloy) comprising the tribo-pair.A Lagrangian finite element code is developed to understand the evolution of the thermo-mechanical fields and their relationship to the observed slip response. The code accounts for dynamic effects, heat conduction, contact with friction, and full thermo-mechanical coupling. At temperatures below the melting point the material is described as an isotropic thermally softening elastic-viscoplastic solid. For material elements with temperatures in excess of the melt point a purely Newtonian fluid constitutive model is employed.The results of the hybrid experimental-computational study provides new insights into the thermoelastic–plastic interactions during high speed metal-on-metal slip under extreme interfacial conditions. During the early part of frictional slip the coefficient of kinetic friction is observed to decrease with increasing slip velocity. During the later part transition in interfacial slip occurs from dry metal-on-metal sliding to the formation of molten Al films at the tribo-pair interface. Under these conditions the interfacial resistance approaches the shear strength of the molten aluminum alloy under normal pressures of approximately 1–3GPa and shear strain rates of ∼107s−1. The results of the study indicate that under these extreme conditions molten aluminum films maintain a shearing resistance as high as 100MPa.Scanning electron microscopy of the slip surfaces reveal molten aluminum to be smeared on the tribo-pair interface. Knoop hardness measurements in 7075-T6 Al alloy at various depths from the slip interface indicate that the hardness increases approximately linearly with depth and reaches a plateau at approximately 40μm from the surface.

On the Change of Melting Point of Metals and other Substances by Pressure

On the Change of Melting Point of Metals and other Substances by Pressure

Influence of pressure on the melting points of certain metals

Influence of pressure on the melting points of certain metals

Societies and Academies

Societies and Academies