Diffusion des Kohlenstoffs in flüssigen Eisen-Kohlenstoff-Silizium- und Eisen-Kohlenstoff-Schwefel-Legierungen

Heisterkamp, Friedrich; Löhberg, Karl

doi:10.1002/srin.196604291

Cited by 8 publications

(5 citation statements)

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“…[9][10][11] Reported The calculated carbon diffusion rate in the liquid phase and experimental carburization rates with several partial pressures of CO gas a function of time from 0.3 to 3.6 ks are presented in Fig. 6.…”

Section: Diffusion Rate Of Carbon In the Liquid Fe-cmentioning

confidence: 99%

The Effect of the Liquid Fe-C Phase on the Kinetics in the Carburization of Iron by CO at 1523K.

2001

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In order to evaluate the effect of liquid Fe-C alloy produced during the carburization on the kinetics of iron carburization, the rates of carburization of iron by CO-Ar gas mixtures have been measured gravimetrically at 1 523 K and the growing rates of the liquid Fe-C layer thickness are also measured. The measurements were made under conditions for which the gas phase mass transfer was negligible. It is found that the weight gains due to the carburization reaction are almost proportional to t 2/3 within experimental scatters. For all runs except that of 1% CO, the liquid phase is observed after the carburization time of 300 s. The liquid phase thickness is found to be almost constant for the first 3.6 ks. After 3.6 ks, the liquid phase thickness starts to increase almost linearly with time. The mechanism to maintain the constant thickness is briefly discussed. The carburization reaction rate is calculated based on the well established decarburization rates and is reasonably agreed with the experimental carburization rate. Compared the experimental results with the calculated liquid phase diffusion rates and the chemical reaction rates, it is confirmed that the ratecontrolling step of the carburization reaction of iron with CO gas at 1 523 K is the chemical reaction COϩO ad →CO 2 at the surface after the liquid Fe-C phase is produced.KEY WORDS: carburization; liquid-solid interface; liquid Fe-C phase, melting point; ironmaking. ExperimentalA schematic diagram of the experimental apparatus is shown in Fig. 1. An iron plate (20ϫ20ϫ5 mm) was buried in Al 2 O 3 powder contained in an alumina crucible (30ϫ40 mm) and heated by a SiC furnace. The alumina reaction tube (ID 60 mm) was fitted with water-cooled O-ring sealed brass caps. The reacting CO-Ar gas mixture was jetted onto the surface of the metal. A 4-mm bore alumina tube held 10 mm above the metal surface was used to introduce the reacting gas. The end position of the gas inlet tube was adjusted to keep the center of reacting tube by using the Al 2 O 3 adjusting ring. The Ar-CO gas mixtures were prepared by mixing the high purity gases, after drying, by passing through columns of magnesium percolate and, for CO, by passing ascarite. Flow rates were controlled by mass flow controllers. All the experiments were carried out at 1 523 K. High purity iron was used for specimen preparation. The typical impurity content of this material (in wt pct) is: O, 0.04, C, 0.02, Al, 0.007, S, 0.002. The specimen was prepared by surface grinding and metallographically polishing the upper surface.The pre-weighted (about 20ϫ10 Ϫ3 kg) sample was slowly brought to temperature under flowing purified Ar. The inlet tube was adjusted to the appropriate height and then the reaction gas, which had been preset, was introduced over the sample. Experiments were terminated by switching back to argon and the sample was pulled down to the lower part of the furnace and allowing to cool to room temperature. The weight gain of carbon during an experiment was determined by measuring the total weig...

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Section: Diffusion Rate Of Carbon In the Liquid Fe-cmentioning

confidence: 99%

The Effect of the Liquid Fe-C Phase on the Kinetics in the Carburization of Iron by CO at 1523K.

2001

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“…D i is the diffusivities of migrating species in metal 11 or in gas. The diffusivities in gas as a function of temperature and pressure are estimated by empirical correlation.…”

Section: Mathematical Treatmentmentioning

confidence: 99%

“…The mass transfer coefficients ( k i ) in the boundary layer at the both sides of the bubble surface are estimated by the surface renew model by 20 D i is the diffusivities of migrating species in metal 11 or in gas. The diffusivities in gas as a function of temperature and pressure are estimated by empirical correlation.…”

Section: Mathematical Treatmentmentioning

confidence: 99%

Physical, chemical and thermal histories of an oxygen bubble in bath during bottom blown process

Sun

Liu

2016

Ironmaking & Steelmaking

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A mathematic model has been developed for an oxygen bubble rising in metal during a bottom blown process. The model successfully coupled local reactions and mass transport with heat transport between metal and the bubble surface, and between the latter and the bubble interior. This novel method reveals the physical, chemical and thermal histories of an oxygen bubble during a bottom blown process. An oxygen bubble rising in Fe-3%C metal under conditions of the oxygen bottom blown process was described by the modelling. The results show (1) the heat supplied to the bath is sourced from the secondary combustion in the bubbles rather than from the decarburisation at a bubble surface; (2) the temperature of a bubble surface reached a maximum of few degrees higher than the bath at few centimetres above the nozzle; (3) the maximum heat supplied to the bath by a bubble midway along the bubble trajectory is much more than the total heat supplied by the bubble reaching the bath surface; (4) the energy in the process-off gas is as high as three-fold of that received by the bath; and (5) iron is unlikely to be oxidised in front of the nozzle.

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“…The mass transfer coefficient in slag phase 29) and reaction rate constant for reaction (3) 15) were selected for k s and k r , respectively. Diffusivities of carbon, 30) oxygen, 31) and silicon 32) in molten iron as a function of the temperature were used for D C , D O and D Si , respectively.…”

Section: Thermodynamic and Kinetic Parametersmentioning

confidence: 99%

Reaction Rates and Swelling Phenomenon of Fe–C Droplets in FeO bearing Slag

Sun

2006

ISIJ Int.

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The reduction of FeO in slag by an iron droplet, decarburisation of the droplet and the droplet swelling phenomenon during slag-metal droplet reaction were analyzed by a kinetic model. Diffusions in the slag phase, diffusions throughout the droplet, interfacial reactions, equilibrium relations and homogeneous nucleation of gas bubbles within the droplet were incorporated in the model.During an Fe-C droplet reaction with FeO bearing slag, decarburisation rate increases with increasing FeO in slag, carbon in the droplet and the droplet size, but the rate decreases with increasing silicon in metal and ambient pressure. The decarburisation rate in unit surface area of the droplet increases with increasing the droplet size. Slow decarburisation during the initial stage of the reaction was suggested by the model, and the desiliconisation and oxygen absorption of the droplet were found to be responsible for this initial slow decarburisation. The initial slow decarburisation is pronounced when the droplet contains higher carbon and silicon, or when the reaction occurs under higher pressure and with the slag containing lower FeO. CO bubble generation within the droplet was suggested to cause the swelling of the droplet. The occurrence of swelling is promoted when the droplet contains higher carbon and lower silicon, slag contains higher FeO, or when the droplet is small, and the reaction occurs under lower pressure.

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Diffusion des Kohlenstoffs in flüssigen Eisen-Kohlenstoff-Silizium- und Eisen-Kohlenstoff-Schwefel-Legierungen

Cited by 8 publications

References 0 publications

The Effect of the Liquid Fe-C Phase on the Kinetics in the Carburization of Iron by CO at 1523K.

The Effect of the Liquid Fe-C Phase on the Kinetics in the Carburization of Iron by CO at 1523K.

Physical, chemical and thermal histories of an oxygen bubble in bath during bottom blown process

Reaction Rates and Swelling Phenomenon of Fe–C Droplets in FeO bearing Slag

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