1. |
Kinetics of iron oxide reduction from CaO‐MgO‐FeOn‐SiO2slags by silicon dissolved in liquid iron |
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Archiv für das Eisenhüttenwesen,
Volume 67,
Issue 8,
2016,
Page 307-313
Hui Xie,
Manuela Schulz,
Franz Oeters,
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摘要:
At steelmaking temperatures, the kinetics of slag‐metal reactions is usually determined by mass transfer. This occurs in two ways: normal mass transfer which is induced by stirring, and mass transfer by interfacial convection induced by interfacially active elements like oxygen and sulphur. In the present work, mass transfer during the reduction of iron oxide from a basic slag by silicon dissolved in liquid iron was studied under defined conditions of gas stirring by argon in MgO crucibles with 1500 g iron and 250 g slag. The variations of the FeO content in the slag and the silicon content in the iron during the reaction were measured by sampling. Trials were carried out with stirring gas flow rates between 1 and 20.4 l/h(STP). The experimental data were evaluated with the multi‐component transport model in order to determine the mass transfer coefficients of the reaction components. Simultaneously, the coefficients of normal mass transfer were calculated with the boundary layer theory of liquid‐liquid mass transfer for non‐turbulent flow conditions. The measured mass transfer coefficients were by a factor 2.5 larger than the theoretically calculated. The difference indicates the presence of mass transfer by interfacial convection. Mass transfer by interfacial convection is superimposed to normal mass transfer.
ISSN:0003-8962
DOI:10.1002/srin.199605495
出版商:Wiley
年代:2016
数据来源: WILEY
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2. |
A new procedure for measuring the thermal diffusivity of non‐metallic melts at high temperatures |
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Archiv für das Eisenhüttenwesen,
Volume 67,
Issue 8,
2016,
Page 314-319
Hans Adolf Friedrichs,
Leonid Wladimirowitsch Ronkow,
Yongmao Zhou,
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摘要:
A new procedure for measuring the thermal diffusivity of non‐metallic melts at high temperatures has been developed, and a measuring set up based on thermography and the use of a CO2laser has been constructed. The working efficiency of the measuring procedure, together with the accuracy and reproducibility of the measured values have been checked by measurements on synthetic slags. The thermal diffusivities of synthetic slag (38% CaO – 38% SiO2– 19% Al2O3– 5% Fe2CO3) at temperatures from 1648 to 1740 K lie between 2.6×10−7and 3.0×10−7m2s−1. The mean deviation of measured values is about ±6%. The advantages of this new procedure are compared with usual laser flash methods and possible error sources are discussed.
ISSN:0003-8962
DOI:10.1002/srin.199605496
出版商:Wiley
年代:2016
数据来源: WILEY
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3. |
Dust formation in a BOF converter |
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Archiv für das Eisenhüttenwesen,
Volume 67,
Issue 8,
2016,
Page 320-327
Lotta Nedar,
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摘要:
Minimisation of waste and manipulation of residues to suit succeeding processes today is one of the steel works most important research areas. BOF dust is expensive to depose in landfills and difficult to recycle due to its zinc contents. The simultaneous loss of raw materials and cost increase makes it important to minimise the generation of dust. This can be done by employing better process control systems with regard to the mechanisms governing the generation. Four dust forming mechanisms can be considered in a converter: ejection of metal, ejection of slag, entrainment of charged material and vaporisation.In order to determine the importance of the four dust forming mechanisms and to characterise dust, with special emphasis to zinc, the off‐gas from a 100‐t BOF was sampled during twenty seven heats. The sampling equipment allows the sampling of both solid dust particles and vaporised elements. Samples from the first and the second part of blowing show significant differences both in chemical composition and in the origin of formation. The major dust formation mechanism is the ejection of metal and slag, respectively. Entrainment of solids plays an important role only during the first part of blowing. Vaporisation of elements from the bath is most important during the end of blowing. The formation of dust is influenced by process operation control, especially lance position, silica contents and time of charging of slag formers. Zinc is mostly found on the rim of ejected particles where a gradual transition of zinc oxide to zinc ferrite to iron oxide is found. At sampling temperatures of between 800 and 1000°C most of the zinc had already condensed.
ISSN:0003-8962
DOI:10.1002/srin.199605497
出版商:Wiley
年代:2016
数据来源: WILEY
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4. |
Transformation behaviour of the high temperature martensitic steels with 8 – 14% chromium |
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Archiv für das Eisenhüttenwesen,
Volume 67,
Issue 8,
2016,
Page 328-342
Helmut Finkler,
Manfred Schirra,
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摘要:
Comprehensive development work on martensitic steels belonging to the so‐called 12% Cr steel group were performed at the Institute for Materials Research (IMF) of Forschungszentrum Karlsruhe on martensitic steels, the so‐called 12% Cr steel group, in order to meet the various requirements in nuclear and conventional energy technology. The transformation characteristics of 29 different grades of steel and 38 heats have been determined and continuous cooling transformation (CCT) diagrams have been prepared. The diagrams are first described by groups of subjects in a chronological order because the change in the chemical composition cannot be correlated in all cases with the change in transformation behaviour.The quenching hardness can be satisfactorily described as a function of the C+N content if, taking into account the Nb, Zr, Ta, Hf fractions, a common effectiveness factor is calculated. This effectiveness factor is also integrated in the calculation of the Mspoint by modifying accordingly the equation proposed by Steven and Haynes for low‐alloy steels and supplemented by the summands for V and W. An equation is introduced for the calculation of the critical cooling rate for pearlite transformation which takes into account the special influence exerted by elements Cr, V, Mo, W, Ge. The comparison between calculated and measured values for Ms and Vcrit is satisfactory, except for some steels.
ISSN:0003-8962
DOI:10.1002/srin.199605498
出版商:Wiley
年代:2016
数据来源: WILEY
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5. |
Carbon or nitrogen alloyed quenched and tempered stainless steels ‐ a comparative study |
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Archiv für das Eisenhüttenwesen,
Volume 67,
Issue 8,
2016,
Page 343-349
Hans Berns,
Rüdiger Ehrhardt,
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摘要:
Some conventional stainless quenched and tempered steel grades were modified by substituting nitrogen for carbon and by variing the contents of chromium, molybdenum and nickel. Results of a comparative study of carbon and nitrogen steels are presented in a wide range of tempering temperatures.In nickelmartensitic steels nickel can be partially substituted by nitrogen without harming the properties. Due to their finer microstructure nitrogen steels with 15‐17 %Cr, 2 %Ni and 0.2 %N, at the same strength level, offer higher toughness and better corrosion resistance than the respective conventional steel X20 CrNi 17 2.
ISSN:0003-8962
DOI:10.1002/srin.199605499
出版商:Wiley
年代:2016
数据来源: WILEY
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