1. |
Mixing enthalpy and heat content measurements of liquid binary iron‐niobium alloys |
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Archiv für das Eisenhüttenwesen,
Volume 66,
Issue 5,
2016,
Page 183-187
Klaus Schaefers,
Michael Rösner‐Kuhn,
Jianping Qin,
Martin G. Frohberg,
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摘要:
The mixing enthalpy of the system iron‐niobium has been determined at 1935 and 2035 K for alloys having Nb mass contents of up to 51.5 % by the levitation alloying calorimetry (LAC). Moreover, by means of the combination of an electromagnetic levitation unit with a drop calorimeter the temperature functions of the enthalpies of the eutectic alloys Fe89.4Nb10.6and Fe41Nb59and the congruent melting compound Fe2Nb have been measured in the liquid state and below their melting points. From these values the melting enthalpies and entropies are calculated. The experimental results are compared with literature data. In consideration of the standard formation enthalpy of the alloys their enthalpy values could be connected with the mixing enthalpy.
ISSN:0003-8962
DOI:10.1002/srin.199501109
出版商:Wiley
年代:2016
数据来源: WILEY
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2. |
Kinetics of Zn and Pb evaporation from liquid iron |
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Archiv für das Eisenhüttenwesen,
Volume 66,
Issue 5,
2016,
Page 188-193
Lutao Li,
Shiwei Tu,
Dieter Janke,
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摘要:
The evaporation kinetics of Zn and Pb from liquid iron at 1600°C were studied under argon pressure 0.1 to 50 bar in an induction furnace. It was found that the limiting step of evaporation underpAr<1 bar is diffusion in the melt. Diffusion in the gas phase becomes rate‐determining with increasing argon pressure. The phase boundary reaction has no effect on the evaporation of Zn and Pb. The evaporation of Zn can evidently be reduced by increasing argon pressure above 1 bar, while the evaporation of Pb is not significantly effected by changes of argon pressure.
ISSN:0003-8962
DOI:10.1002/srin.199501110
出版商:Wiley
年代:2016
数据来源: WILEY
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3. |
Investigations on the non‐steady operating behaviour of molten metal in the ladle and its emulsified liquid slag content |
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Archiv für das Eisenhüttenwesen,
Volume 66,
Issue 5,
2016,
Page 194-198
Peter Drögemeier,
Martin Neifer,
Sigurd Rödl,
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摘要:
The separating behaviour of emulsified slag is greatly influenced by the flow conditions prevailing in the ladle. Especially non‐steady flow conditions characterized by a time‐related decrease in flow velocity (decaying flow condition) play an important role in this context. In order to clarify these phenomena, a number of numerical computations and model trials were performed. The computed and measured results obtained show a high degree of coincidence. Specific process engineering recommendations aimed at an improvement in the separation of emulsified slag droplets are presented. A new equation has been developed to calculate the holding time required for the separation of emulsified slag droplets between the ladle filling and casting steps. The results obtained with this equation coincide accurately with the computed and measured data.In addition, model trials and numerical computations of this type may contribute to a quick and economically efficient solution of similar problems in the design and improvement of other metallurgy and process technology systems.
ISSN:0003-8962
DOI:10.1002/srin.199501111
出版商:Wiley
年代:2016
数据来源: WILEY
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4. |
Mathematical modelling of fluid flow, heat transfer and solidification phenomena in continuous casting of steel |
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Archiv für das Eisenhüttenwesen,
Volume 66,
Issue 5,
2016,
Page 199-205
S. K. Choudhary,
Dipak Mazumdar,
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摘要:
A steady state, two‐dimensional mathematical model for continuous billet casting operations has been developed. Towards this, governing equations of fluid flow and heat transfer together with their appropriate set of boundary conditions were derived and solved numerically via a control volume based implicit finite difference procedure (e.g., SIMPLE). The effect of various assumptions and procedures applied to modelling of turbulence phenomena, thermal buoyancy, flow through the mushy zone, free surface conditions etc., on the sensitivity of the computed results was investigated computationally. Of all these, modelling of heat and fluid flow phenomena in the mushy region was found to have relatively more effect on the predicted results. In addition to these, a set of three different billet casting operations reported in literature were simulated mathematically and direct comparisons were made between predicted and observed solidified shell profiles. Such comparisons demonstrated reasonable to excellent agreement between theory and experiments.
ISSN:0003-8962
DOI:10.1002/srin.199501112
出版商:Wiley
年代:2016
数据来源: WILEY
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5. |
Strength and fatigue properties in medium carbon duplex steels |
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Archiv für das Eisenhüttenwesen,
Volume 66,
Issue 5,
2016,
Page 206-212
Fereydun Bahrami,
Rankin Kennedy,
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摘要:
The effect of microstructure on strength and fatigue properties has been investigated in two medium carbon alloy steels (BS 817M40 and BS 835M30) by developing dual‐phase, ferritic‐martensitic microstructures. Hardness‐strength relationships and fatigue resistance at comparatively high strength levels were investigated by producing various microstructures. Conventional quenching and tempering, intercritical annealing and step quenching were used to vary the proportion, morphology and distribution of the ferrite and martensite phases.The results of the present study show that both hardness and strength increase with increasing proportion of martensite and/or hardness of the second phase. The relationship between hardness or strength and martensite percent is not in good agreement with a simple “law of mixtures” but is compatible with a more rapid strength increase at high martensite contents. The dual phase microstructures from the present study show superior near threshold ΔKTHvalues than normal tempered martensite. The results also show a high degree of correlation between Paris equationmvalues and fracture toughnessKIC, showing that for high m valuesKICis low and vice versa. The present experiments show that although crack initiation resistance in dual‐phase steels is excellent crack propagation rates are higher than in quenched and tempered microstructures for a givenΔK.
ISSN:0003-8962
DOI:10.1002/srin.199501113
出版商:Wiley
年代:2016
数据来源: WILEY
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6. |
Dislocation creep controlled superplasticity in the high carbon steel 140NiCr16‐6 |
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Archiv für das Eisenhüttenwesen,
Volume 66,
Issue 5,
2016,
Page 213-216
Harald Hofmann,
Georg Frommeyer,
Maik Bogatsch,
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摘要:
Superplasticity in the alloyed high carbon‐steel 140NiCr16‐6 with phosphorus additions and a fine grained microdupiex structure – containing cementite in volume fractions of 22 % (Fe,Cr,Ni)3C, particle size of about 1 μm and with a medium ferrite grain size of about 2 μm – has been investigated in the temperature regime of 550 to 675°C and in the strain rate range of 10−5to 5 · 10−2s−1. Maximum strain rate exponents ofm= 0,45 at 675°C with strain rates of the order of 10−4s−1have been determined. Maximum superplastic elongations of about 700 % were detected. At higher strain rates of 10−3s−1superplastic elongations of about 570 % were achieved. At relatively low test temperatures of 550°C elongations up to 230 % were recorded.The activation analysis in the temperature regime of 550 to 650°C show an activation energy for superplastic flow of 250 ± 20 kJ/mol. This is in agreement with the activation energy for lattice self diffusion of iron in α‐iron. Above 650°C the activation energy decreases to 70 kJ/mol. This is due to a stress induced decrease in the eutectoid α‐γ‐transformation temperature from 685°C to somewhat lower temperatures during superplastic deformation.The superplastic deformability (m>0.3) of this steel in a wide strain rate range at relatively low temperatures above 550°C allows near net shape forming of complex parts applying low flow stresses.
ISSN:0003-8962
DOI:10.1002/srin.199501114
出版商:Wiley
年代:2016
数据来源: WILEY
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7. |
Microprocesses of metal dusting on iron |
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Archiv für das Eisenhüttenwesen,
Volume 66,
Issue 5,
2016,
Page 217-221
Eckhard Pippel,
Jörg Woltersdorf,
Hans Jürgen Grabke,
Silke Strauß,
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摘要:
In strongly carburizing atmospheres iron and steels are subject to ‘metal dusting’, a catastrophic carburization, leading to disintegration into a dust of carbon and metal particles. TEM investigations of iron foils in different states of this corrosion process have clearly shown now that unstable cementite is an intermediate in the reaction. The carbide is formed at the iron surface after supersaturation (aC>1), its disintegration is started by graphite deposition on its surface (aC= 1). The carbon atoms from Fe3C disintegration are attached to the graphite planes which are vertically oriented to the cementite surface, the iron atoms diffuse through the graphite and agglomerate to small particles (∼ 20 nm) which act as catalysts for further carbon deposition from the atmosphere, till they are densely covered with graphite. The TEM investigations are in good agreement with preceding studies concerning kinetics and mechanisms of metal dusting.
ISSN:0003-8962
DOI:10.1002/srin.199501115
出版商:Wiley
年代:2016
数据来源: WILEY
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8. |
Investigation of the orientation dependence of recovery in low‐carbon steel by use of single orientation determination |
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Archiv für das Eisenhüttenwesen,
Volume 66,
Issue 5,
2016,
Page 222-229
Dierk Raabe,
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摘要:
Iron poly‐ and oligocrystals with a carbon mass content of 0.02 % were cold rolled to a technical strain () of 90 % and annealed at 1000 K in a salt bath furnace for 1 to 300 s. The polycrystals had an initial grain size of about 20 μm. The oligocrystals consisted of 20–40 grains with a longitudinal extension of 10–20 mm and a transverse extension of 2–6 mm. The microstructure of both types of specimens was investigated by use of optical and scanning electron microscopy. The crystallographic texture was examined by use of X‐ray and electron back scattering diffraction. It is shown that both primary recrystallization and recovery considerably depend on the crystal orientation. In the 90 % cold rolled oligocrystals {111}uvwand {112}oriented grains recrystallized during annealing. In crystals with {001 }orientation, however, primary recrystallization was suppressed. In the polycrystals the latter phenomenon was less pronounced. In these samples it was observed that {001 }oriented grains are consumed by growing nuclei stemming from neighbouring crystals.
ISSN:0003-8962
DOI:10.1002/srin.199501116
出版商:Wiley
年代:2016
数据来源: WILEY
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