Melting Point Of Iron Research Articles

Thermodynamics of the second order transitions in alpha and epsilon iron

The presence of a second order transition in epsilon iron, the hexagonal closest packed form, is demonstrated. Two functions of the form T *(Θ −1/2 + A + BΘ) are proposed to model the extra heat capacity beyond what can be represented in a polynomial model in the regions 50 K below and 30 K above a lambda point. With A and B chosen so that Δ C p/T is zero with a zero first derivative at the end points, these functions can provide an accurate and convenient representation for the thermodynamic properties of a material at temperatures and pressures near the lambda point for a second order transition. Calculations of the T/P phase diagram of iron provide a good test of the usefulness of this model since two second order transitions are present in the region of interest. This model for the thermodynamic properties of iron reconciles the static and shock wave studies on the melting point of iron at high pressures. Other forms of solid iron may be stable at the melting point above 100 GPa, but the melting point of pure iron at the inner core boundary of the Earth, 328.9 GPa, is probably within 500 K of the calculated melting point for ε′ iron at this pressure, 4 680 K.

Equilibrium distribution coefficient of phosphorus in iron alloys.

In this work, the equilibrium distribution coefficients of phosphorus kP0 in Fe-P binary and Fe-C-P ternary systems were obtained experimentally and the carbon content dependence of the equilibrium distribution of P was discussed using Distribution Interaction Coefficient. Temperature dependence of kP, α0 for α phase is given bykP, α0=NsP/NlP=0.715-3.2O×10-4T.From the above equation, kP, α0 at infinite dilution of P, that is to say, at the melting point of iron, is 0.136, kP, γ0 for γ phase at high carbon concentration is about 0.09. kP, γ0 increases with the concentration of carbon and kP, γ0 at infinite dilution is 0.06. Also, the relation between kX0 of various elements for α phase and that for γ one was derived thermodynamically.

Melting and adiabatic temperature distributions in the outer earth core

The Ross-Lindemann melting criterion is employed to derive a theoretical melting curve for iron in the pressure range of the outer core of the Earth. The intermolecular potential used is a rydberg function. The agreement with the available experimental data is guaranteed fairly well. The melting point of iron at the mantle-core boundary results to be 3950 K, and 5650 K at the outer-core-inner-core, boundary with an average gradient of about 0.76 deg/km in the outer core. Taking into account recent results on the thermodynamical Gruneisen gamma, the adiabatic temperature distribution through the outer core is also given. No overlapping of the two curves is found which leaves open the possibility of explaining the thermodynamics of the core and the origin of the geomagnetic field in the classical way, by definitely avoiding the so-called core paradox.

Plastic deformation of delta-ferritic iron at intermediate strain rates

The plastic deformation of delta-ferritic iron, represented by an electrolytic iron and Fe-0.028 C, Fe-0.044 C and Fe-3.0 Si alloys, has been measured for the temperature range 1200 to 1525‡C and the strain rate range 2.8 x 10-5 to 2.3 x 10-2 s-1. For the bamboo-like tension specimens the plastic flow behavior is approximately nonlinear viscous. Delta-ferrite is more than four times weaker than austenite, and does not exhibit dynamic recrystallization. At the melting point of iron the extrapolated steady-state flow stress increases from 0.31 to 1.86 MN/m2 (45 to 370 psi) over the range of strain rate examined.

The Anelasticity of the Inner Core

Summary Spectral ratios of short-period core phases with common source and receiver and with nearly the same ray paths in the mantle have been formed to derive a Q-structure for 1 Hz compressional waves in the inner core. Data from one large array (NORSAR) have been used to extract the relevant phases, including the pairs (PKIKP, PKiKP), (PKIKP, PKP(BC)), (PKIIKP, PKiKP), (PKIIKP, PKKP(BC)). An array is needed in particular to separate PKIKP and PKiKP and to identify PKIIKP. In forming the spectral ratios, techniques like spectraforming and instantaneous spectral analysis have been employed. The data have been inverted using a number of different velocity models. The essential features of the resulting Q-models are the same: Q rises from a value of about 200 near the inner core boundary to about 600 at 400 km depth penetration. Below 450 km depth the Q-structure is not well constrained, but probably is below a value of 2000. It is suggested that the temperature at the inner core boundary is close to the melting point of iron and that partial melting occurs in at least part of the inner core. The low Q-structure greatly affects the amplitudes of phases like PKIIKP and PKJKP. It is verified that PKIIKP is observable only in exceptional cases and arguments are presented that PKJKP is too small to be observed.

Lithoidal fracture of high-carbon steels

1. The effect of carbon on the susceptibility of steel to the formation of primary and resistant lithoidal fracture is not the same in all cases. The directional effect and the intensity of the effect depend on the quantity and composition of the carbide phase and its solubility in austenite. Increasing amounts of carbon in the steel favor local melting during overheating, especially in the grain boundaries, intersections of grains, and in places rich in low-melting impurities (phosphorus) and elements lowering the melting point of iron, and also around nonmetallic inclusions of the MS type. With satisfactory fracture (fine crystalline, cryptolithoidal) of such steel the most important properties are irreversibly low. 2. It was found that the large enrichment in phosphorus (50–60 times) of energetically weak zones of the matrix (boundaries and joints of grains, boundaries between the matrix and nonmetallic inclusions) occurs only with their melting. 3. Overheating of alloy steel Kh2N4V to temperatures leading to the first portions of liquid steel induces substantial enrichment in phosphorus, chromium, and tungsten. Cooling leads to precipitation of excess phase of complex composition (white phase). The precipitation of this phase predetermines the resistance of the pseudograins to rectification. 4. Stable lithoidal fracture is due to precipitation in boundary areas on the surface of prior austenite grains of compounds difficult to dissolve in ordinary heat treatments that include nitrides, special carbides, carbonitrides, intermetallic compounds, and other excess phases.

Thermodynamics of liquid Fe-C solutions

The activity of carbon in liquid iron has been determined at low concentrations by means of the CO-CO2 equilibrium and at high concentrations by the solubility of graphite. At intermediate concentrations there is a broad region in which measurements have not been made because of thermal instability of gas mixtures high in CO. Because of this phenomenon it is suggested that the reported activity coefficients at low concentrations may be in error and are only useful in determining a limiting value at infinite dilution. At temperatures below the melting point of iron, activity coefficients at intermediate concentrations along the liquidus line are calculated from recent measurements of the activity in austenite and of the solidus and liquidus lines of the phase diagram. The results agree fairly well with the data of Richardson and Dennis at higher temperatures. Several interpolation formulae are investigated. Equations are presented which describe the thermodynamic properties of the binary liquid solution at all compositions between the eutectic and 1760°C.

アーク溶接時の冶金反応に関する研究(第2報)

The rates of the Si and Si-Mn deoxidations in arc melting were studied in order to investigate their behaviour in deoxidation reactions in arc welding. The temperature of the melting pool ranges between the melting point of iron and about 2000°C. However, according to our previous paper on deoxidation equilibriums in arc melting, it was shown that deoxidation reaction in arc melting could be treated as a reaction at some mean temperature.On this basis, the rates of the Si and Si-Mn deoxidations were measured using the apparatus and melting procedure which were almost identical to the ones reported in the previous paper. The results of the analysis of the experiments were as follows:(1) Rate of deoxidation is shown by the following equation:d[%O]/dt=I/V k0([%O]-[%O]e)where [%O] is oxygen content at time t; [%O]e is oxygen content at apparent equilibrium; I is current; V is volume of molten pool. The rate constant, k0, is independent of the melting condition (pressure of Ar Atmosphere, current and voltage), but depends upon the content of elements (Si, Mn, O) in the specimen and also the appartus used.(2) The above equation was compared with the reaction model, which assumes that the separation process of the deoxidation product is the rate determining step and also that the rate depends upon the strength of the stirring in the pool. Then, it is probable that the strength of the stirring (stirring speed at the place where the deoxidation product is separated) is proportional to the current. However, this conclusion has to be further investigated.(3) In the Si deoxidation process, the rate constant, k0, is constant in low Si range (Si 0.4%). In the Si-Mn deoxidation, k0 increases as the content of Si decreases and the content of Mn increases. In addition, k0 increases as the oxygen content in the specimen increases.

Mineralogy of the oxidation products of the Sputnik 4 fragment and of iron meteorites

The melted and oxidized products on the Sputnik 4 fragment make up 10 to 15 per cent of the total mass and consist of droplets of a iron, coated with the iron oxides wustite (Fe1−xO), magnetite (FeFe2O4), and akaganeite (β FeO(OH)), and the magnesium oxide periclase (MgO). This assemblage of minerals reflects nonequilibrium conditions of rapid cooling from above 1535°C, the melting point of iron, to below 80°C, the temperature region in which akaganeite can form as a rnetastable variety of iron oxy hydroxide. A re-examination of the crust during the fifth month after recovery showed that the akaganeite and some of the wustite had been oxidized to hematite (α Fe2O3). Wustite and akaganeite are metastable at surface temperatures and are therefore virtually unknown in terrestrial rocks and in meteorites. Their discovery on the Sputnik 4 fragment, however, led to the investigation, by X-ray diffraction procedures, of the crusts of numerous iron meteorites. Wustite was identified in association with magnetite in the fusion crust of the Bogou iron that fell in Upper Volta in August 1962, and of several older irons including the Braunau, Czechoslovakia, hexahedrite that fell in 1847. Akaganeite was found among the alteration products of weathered iron meteorites.

The experimental fusion curve of iron to 96,000 atmospheres

The melting point of iron has been determined to 96,000 atmospheres, and the temperature for the α-γ transition to 76,000 atmospheres. Simon's fusion equation, P/a = (T/T0)e - 1, fits the experimental melting points with a = 75,000 atm and c = 8. Extrapolation of the melting points to 1.4×106 atm, the pressure at the boundary of the earth's core, gives 2340±200°C. The temperature for the α-γ transition decreased about 200°C at 76,000 atm.

The Earth's magnetic and electrical moment

There are two outstanding problems. One is to explain the Earth's magnetic moment, and the other is to explain its electrical moment. Together with these, we have to explain the magnetic moments of all the astronomical bodies, such as the Sun and stars.My feeling is that the two problems are connected. The Earth, for example, is very hot inside, and in the interior its temperature is above the melting point of iron. Such a hot body is like a hot filament, and produces an atmosphere of electrons. This atmosphere flows out to infinity and produces a space‐charge.

The optical determination of high metallurgical temperatures - The melting point of iron

The present investigation has been carried out in the Metallurgical Department of the National Physical Laboratory in order to adapt the optical pyrometer to the estimation of the fusion temperatures of materials of high purity and high melting point and of substances of corrosive or volatile nature. Melting points and thermal changes in the solid state at high temperatures are generally determined by means of platinum thermocouples which are protected from the molten metal or its vapour by insertion in a refractory sheath. Contamination of the molten metal is frequently occasioned by chemical attack which takes place between the metal and the refractory crucible or couple sheath. This is particularly marked when the refractories contain siliceous material.