摘要:

Model experiments on mass transfer in gas‐stirred ladles were carried out in reactors of different geometric dimensions. The model system consists of: water, cyclohexan as model slag, iodium as element to be extracted from water into slag phase, and compressed air as stirring gas.The experimental results show that when using an eccentric bottom nozzle, rate constants of mass transfer are always smaller than with centric gas injection. Centric stirring leads to comparatively larger increases of rate constants if a certain gas flow rate is exceeded. Both results can be explained by different emulsification conditions of slag phase.Theoretical calculations of residence times show that mainly the emulsification of small droplets taken along by the recirculation flow is responsible for accelerations of mass transfer in gas‐stirred ladles.

ISSN:0003-8962    

DOI:10.1002/srin.199101719

出版商:Wiley    

年代:2016

数据来源: WILEY

摘要:

Measurements of slag emulsification in gas‐stirred ladles were carried out in cold‐model systems of different geometric sizes. Detaching of slag droplets – necessary for efficient emulsification – only takes place if the flow velocity at the slag/metal interface exceeds a certain level.The use of a centric nozzle leads at high gas flow rates to considerably larger degrees of emulsification than eccentric stirring. The reason of this phenomenon is that the recirculation flow during centric gas injection transports larger amounts of emulsified droplets into deeper regions of the melt while during eccentric stirring there is more time for reseparation of slag droplets into the top slag.Comparing emulsification results with mass‐transfer measurements, the dependence between rate constants as well as degrees of emulsification and Froude number shows similar behaviour.

ISSN:0003-8962    

DOI:10.1002/srin.199101720

出版商:Wiley    

年代:2016

数据来源: WILEY

摘要:

Quasi‐single‐phase mathematical models as applied to the ladle hydrodynamics have been analysed rigorously. It is shown that choice of convergence criteria, nodal configuration and differencing schemes all influence the computed results significantly and consequently, results independent of these numerical parameters must first be established to draw any useful conclusion. Several quasi‐single‐phase computational procedures reported in the literature to study the gas‐injection‐induced flow phenomena have been critically examined. To this end, experimentally measured bulk flow‐fields, plume‐rise velocity and gas voidages have been compared with those predicted numerically. Such comparisons indicate that the bottom injection phenomena (viz., bulk flow, plume‐rise velocity, and gas volume fraction within the plume etc.) can be adequately represented by assuming bubble slippage and considering a constant rise velocity in the two‐phase region in the numerical solution scheme.

ISSN:0003-8962    

DOI:10.1002/srin.199101721

出版商:Wiley    

年代:2016

数据来源: WILEY

摘要:

For the modelling of strains und stresses arising during solidification data on the mechanical and thermal properties of the steel are needed. Data on density and on related properties of iron and iron‐carbon alloys in the literature were evaluated giving the thermal contraction as a function of temperature and carbon content.

ISSN:0003-8962    

DOI:10.1002/srin.199101722

出版商:Wiley    

年代:2016

数据来源: WILEY

摘要:

Fließkurven beschreiben das Formänderungsvermögen von Werkstoffen. Gleichzeitig liefern sie Informationen über die Wechselwirkung zwischen der Ver‐ und Entfestigung, wobei diese beiden Eigenschaften temperaturabhängig sind.Fließkurven wurden an Stählen aufgenommen, die sich im wesentlichen in ihrem Kohlenstoffgehalt unterscheiden. Die Bestimmung der Formänderungsfähigkeit erfolgte bei Temperaturen, die denen entsprechen, bei denen eine Austenitformhärtung vorgenommen wird. Die mathematische Beschreibung der Fließkurven läßt erkennen, daß zunächst mit steigender Umformtemperatur die Verfestigungsrate abnimmt. Der Kohlenstoffgehalt erhöht dagegen die Verfestigungsrate. Die dynamische Erholung wird mit wachsender Umformtemperatur beschleunigt, ebenso mit steigendem Kohlenstoffgehalt.

ISSN:0003-8962    

DOI:10.1002/srin.199101723

出版商:Wiley    

年代:2016

数据来源: WILEY

ISSN:0003-8962    

DOI:10.1002/srin.199101724

出版商:Wiley    

年代:2016

数据来源: WILEY

摘要:

The features of discontinuous decomposition in high‐nitrogen austentitic steels are considered. Structure and formation kinetics of pearlite‐like colonies of “the austenite‐with‐equilibrium‐nitrogen‐content – Cr(M)2N nitride” are discussed. The discontinuous decomposition of nitrogen supersaturated austenite is shown to effect harmfully the mechanical properties of the steels studied. To suppress the harmful effect of the discontinuous decomposition of the austenite the four methods are proposed as follows: use of vanadium as an alloying element, high‐temperature thermomechanical treatment, production of a “microduplex” type structure and granule technology.

ISSN:0003-8962    

DOI:10.1002/srin.199101725

出版商:Wiley    

年代:2016

数据来源: WILEY

ISSN:0003-8962    

DOI:10.1002/srin.199101726

出版商:Wiley    

年代:2016

数据来源: WILEY

ISSN:0003-8962    

DOI:10.1002/srin.199101715

出版商:Wiley    

年代:2016

数据来源: WILEY