加热速度对T91铁素体耐热钢奥氏体形成的影响

采用高精度差分膨胀仪对不同加热速度(10~6000 K/min)下T91铁素体耐热钢的奥氏体形成动力学规律进行了系统研究.研究表明:加热速度显著影响T91钢的奥氏体形成开始温度Ac1、结束温度Ac3、相变速率及淬火后的组织.加热速度愈大,Ac1和Ac3温度愈高,奥氏体相变速率愈快,奥氏体形成温度区间愈窄;相对较慢和较快的加热速度对淬火后的组织都有不利的影响.     

Phase transition kinetics in iron and steel during heating

Similarity theory is used to analyze phase transformations in iron and steel during heating. A kinetic equation is obtained by assumption of self-similarity of the phase transition. Experimental data are processed and effective kinetic parameters determined. It is concluded from the results obtained that the elementary act of phase transition consists of a cooperate transition into the new phase of regions containing (1–2)·10² atoms.Translated from Inzhenerno-fizicheskii Zhurnal, Vol. 61, No. 4, pp. 669–672, October, 1991.     

Calculating kinetics of oxide film growth during laser heating

The process of oxide film growth on the surface of a copper target in air under the action of CO₂ laser radiation is considered.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 58, No. 3, pp. 385–388, March, 1990.     

Calculation of temperature under heating by an immobile laser beam

We present a concept of solving the problem of heating a semibounded space by an immobile source with Gaussian power distribution via the hypergeometrical function of two variables. The kinetics of thermal saturation is analyzed under heating by an immobile Gaussian heat source. Under the assumption of a three-dimensional heat flow, the formula for temperature of any point of a surface is obtained under heat treatment by a mobile Gaussian source.     

Theoretical study of the kinetics of austenitization in steels with heating by continuous laser radiation

A determination is made of the degree of austenitization taking place with the diffusional displacement of grain boundaries in different regions affected by laser radiation (LRR). The process of the formation of stable austenite is analyzed.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 52, No. 3, pp. 444–449, March, 1987.     

Calculation of residual stresses induced during laser quench-hardening of steel

We present a theoretical and numerical analysis of the quasi-stationary uncoupled problem of thermoelastic-plasticity with the goal of estimating the amount of residual stress in steel after laser quench-hardening.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 61, No. 6, pp. 998–1006, December, 1991.     

Calculation of the heating of layered bodies

An expression is obtained for the temperature nonuniformity parameter for a pack of plates and the conditions for the transition from the pack to a quasiuniform body are analyzed.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 45, No. 2, pp. 316–320, August, 1983.     

Calculation of the heating of polydisperse particles in a gas

The problem of the heating of polydisperse particles in a gas is solved with allowance for the temperature field inside a particle and the variation of the gas temperature.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 38, No. 3, pp. 485–489, March, 1980.     

Temperature measurements in the pulsed laser heating of metals

The results of an investigation of the temperature dynamics of certain metals, measured by a photoemission method with a time resolution of 1 μsec, when they are heated in air and in an argon medium by millisecond laser radiation (λ = 1.06 μm) with energy densities of 75–140 J/cm² are presented.     

Thermal and thermodeformational processes in the forced heating of steel

The dynamics of metal heating in a furnace of pacing- beam type is investigated experimentally and theoretically.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 58, No. 3, pp. 402–405, March, 1990.     

Boriding kinetics of H13 steel

It is known that boriding has been employed to increase the service life of parts such as orifices; ingot molds, and dies for hot forming made of AISI H13 steel. In this study, case properties and kinetics of borided AISI H13 steel have been investigated by conducting a series of experiments in Ekabor-I powders at the process temperature of 1073, 1173 and 1273 K for periods of 1-5 h. The presence of borides FeB and Fe₂B of steel substrate was confirmed by optical microscopy and scanning electron microscopy (SEM). The results of this study indicated that the morphology of the boride layer has a smooth and compact morphology, and its hardness was found to be in the range of 1650-2000 HV. Transition zone observed between the hard boride coating and the matrix was relatively softer than the substrate. The kinetics of boriding shows a parabolic relationship between layer thickness and process time, and the calculated activation energy for the process is 186.2 kJ/mol. Moreover, boriding parameter BOP, which is only a function of boride layer thickness and activation energy, has been suggested for the prediction of layer thickness in boriding of AISI H13. There is a reasonable correlation between the progress of boride layer thickness and proposed time-temperature-compensated parameter. Similar findings have been found when it is applied to another steels including tool and low alloy steels, as well as Armco iron.     

The kinetics of steel corrosion in sea water

The kinetics of corrosion damage accumulation in stainless steels of various systems was studied using samples exposed in a model aqueous NaCl solution and in sea water. The time variation of the degree of corrosion damage corresponds to a reaction of the first order. The values of the corrosion activation energy and a parameter characterizing protective properties of a protective film on the metal surface are determined.     

Graphite melting under laser pulse heating

For a long time, the solid/liquid/vapor triple point of graphite has been a subject of debate, and despite the progress in the experimental techniques adopted, the uncertainties became even greater in recent years. In the experiments described in this paper spherical graphite specimens were heated by four tetrahedrally oriented laser beams to produce a fairly uniform temperature on the surface. A sufficiently large amount of molten graphite was produced to make it possible to identify the liquid/solid transition by a conventional thermoanalytical method. The temperature was measured by multichannel pyrometry, which enabled a detailed analysis of the perturbations and errors to be carried out. The triple point of graphite was determined to be T _t=4100±50 K and p _t=110±10 bar.Paper presented at the Second Workshop on Subsecond Thermophysics, September 20–21, 1990, Torino, Italy.     

The kinetics of softening of materials in nonstationary regime of heating

Equations for determining the working life of a plate subjected to a longitudinal force in the presence of symmetric heating are derived taking into account the change of the modulus of elasticity and the ultimate strength of the material with temperature.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 17, No. 3, pp. 479–485, September, 1969.     

Picosecond laser heating and melting of graphite

Ultrashort laser pulses impinging onto solid, strongly absorbing surface deposit their energy within an absorption depth from the surface. This localized energy deposition may result in rapid and very efficient heating of the surface to temperatures far exceeding the melting or boiling point. Temperature evolution at the surface of samples and their electronic structure may be studied with nonperturbing, time-resolved optical diagnostic techniques. Picosecond laser pulses provide the fastest means for heating matter at high temperature, since the characteristic energy transfer times from photoexcited electrons to the lattice occur in this time scale. Surface evaporation is not affecting the observations in this time scale, simply because there is no time for the surface atoms to escape. As an illustration, measurements on graphite are presented here. The complex index of refraction of highly oriented pyrolytic graphite (HOPG) during picosecond laser irradiation has been measured at 1.06 m via time-resolved ellipsometry at angles of incidence up to 80. In particular, a value of the complex index of refraction for the liquid phase has been derived.Paper presented at the First Workshop on Subsecond Thermophysics, June 20–21, 1988, Gaithersburg, Maryland, U.S.A.     

Age-hardening kinetics and microstructure of PH 15−5 stainless steel after laser melting and solution treating

Microstructural characterization and the kinetics of ageing of 15 PH stainless steel is studied in the fusion zone and in solution-treated and quenched (as-quenched) samples. Fusion zone had a finer structure than the as-quenched samples due to melting and subsequent solidification. This had a major effect on the amount of the hardness received in the fusion zone. The ageing structure of both samples was essentially the same, except for the smaller solidification cell size of the fusion zone. Strengthening was achieved by the formation of coherent precipitation of copper in the b c c martensite. Copper precipitates were found to be related to the parent martensite with a Kurdjumov-Sachs orientation relationship in both samples. Precipitates were spherical in shape and they nucleate and grow both on the dislocations and in the matrix. No incubation period was observed in the hardening curves. Kinetics of precipitation was studied from an Arrhenius type equation for both samples. It was found that, at high ageing temperatures, the activation energy for precipitation hardening was approximately the same as that of the activation energy for substitutional diffusion in b c c ferrite. At lower ageing temperatures, the calculated activation energy was consistent with the activation energy for short circuit diffusion of substitutionals in b c c structure. Microstructural characterization and the activation energy calculations showed that precipitation of copper in both samples was controlled by the diffusion of copper in b c c martensite. At high ageing temperatures, mass transport of copper was through the lattice. At low temperatures, the contribution of high dislocation density to the apparent diffusivity was large.     

Calculation of the reliability of steel underground pipelines

We present basic principles of reliability calculations for steel underground pipelines resting on stochastic elastic foundation that based on the strength and stiffness criteria using the absolute maxima of arbitrary functions. Specific numerical examples illustrating a general calculation procedure are presented.     

Effect of high-temperature heating of bimetallic steel billets

A mathematical model of high-temperature induction heating of a two-layer bimetallic cylindrical specimen with an allowance for the effect of thermoelastoplastic loading has been developed on the basis of the inverse problem method. The results of a mathematical experiment on determining the optimum heating conditions connected with abrupt changes in the inductor's dynamic parameters are provided.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 58. No. 3, pp. 392–401, March, 1990.     

Interferometric measurement of laser heating in praseodymium-doped YAG crystal

Temperature measurement is required for many applications but can be difficult in some cases. Laser heating or cooling studies demand accurate measurements of temperature changes. A Michelson interferometer configuration has been used to investigate laser heating in solids. An analytical formula was derived to estimate the temperature change from the fringe count by taking into account the temperature dependence of the sample length and refractive index. When 115?mW of a focused Ar+ laser beam (488?nm) passes through a Pr(3+)-doped YAG sample, its temperature increased by 11.7±1.0?K along the beam path due to nonradiative relaxation. The power dependence of the fringe count/movement was recorded. The temperature change was estimated by the interferometric method and is in agreement with that measured by a thermocouple.