1. |
A contribution to the theoretical description of metal‐slag reaction kinetics |
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Archiv für das Eisenhüttenwesen,
Volume 66,
Issue 10,
2016,
Page 409-415
Franz Oeters,
Hui Xie,
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摘要:
In this paper the main aspects of a theoretical model of mass transfer through liquid‐liquid interfaces under non‐turbulent flow conditions are described. The model is based on the general boundary layer theory of momentum and mass transfer. Expressions for calculation of the mass transfer coefficients on the metal and slag side of the phase boudary are presented. It is shown that the model comprises as limiting cases the mass transfer through free surfaces and at solid walls.
ISSN:0003-8962
DOI:10.1002/srin.199501146
出版商:Wiley
年代:2016
数据来源: WILEY
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2. |
Modelling of microstructural evolution during accelerated cooling of hot strip on the runout table |
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Archiv für das Eisenhüttenwesen,
Volume 66,
Issue 10,
2016,
Page 416-423
Arun Prasad,
Sudhakar Jha,
Nirmalendu S. Mishra,
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摘要:
Microstructural evolution in the hot strip after finishing and subsequent accelerated cooling on the runout table has been modelled in order to assess their suitability for further processing. Transient heat transfer and kinetics of phase change comprising austenite to ferrite plus pearlite have been coupled to ascertain temperature profile, taking into accout the heat generated during phase change. Johnson‐Mehl‐Avrami relation together with Scheil's rule of additivity have been invoked. Several process parameters such as, coefficient of heat transfer, temperature at the exit of finishing stand, thickness and the speed of strip have been varied to determine their influence on the extent of phases engendered on the runout table. It has been demonstrated that greater spreadout in cooling arrangement with relatively lower heat transfer coefficient ensures homogeneity in microstructure. Cooling from comparatively higher finishing temperatures may result in greater microstructural uniformity. Two grades of steel – namely 0.05C‐0.23Mn‐0.015Si and 0.08C‐0.37Mn‐0.06Si – were chosen to carry out plant trials to validate the model. Special features of the microstructure have been brought out and the mechanical properties have been correlated.
ISSN:0003-8962
DOI:10.1002/srin.199501147
出版商:Wiley
年代:2016
数据来源: WILEY
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3. |
Influence of the lubricant on temperature distribution in the forging dies |
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Archiv für das Eisenhüttenwesen,
Volume 66,
Issue 10,
2016,
Page 424-429
M. Gierzynska‐Dolna,
Maciej Pietrzyk,
Z. Kucharczyk,
P. Lacki,
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摘要:
Experimental and theoretical analysis of the influence of the lubricant on the temperature distribution in the tool during forging is presented. Finite element solution of the general diffusion equation is used to calculate the heat transfer contact between the die and the hot workpiece and during the interpass times. The results of calculations are compared with the results of measurements carried out using thermocouples inserted in the die. Two ways of modelling heat transfer through the contact surface are considered. The first treats a lubricant as a separate layer with the relevant thermal properties. The second assumes a temperature discontinuity at the interface and introduces the heat transfer coefficient. Insulating properties of various lubricants are compared. White‐water lubricant shows the best insulating properties. The values of the heat transfer coefficient obtained from the inverse analysis vary from 2600 (without lubrication) to 1500 W/m2K (white lubricant).
ISSN:0003-8962
DOI:10.1002/srin.199501148
出版商:Wiley
年代:2016
数据来源: WILEY
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4. |
Prestressing of compression springs |
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Archiv für das Eisenhüttenwesen,
Volume 66,
Issue 10,
2016,
Page 430-432
Fryderyk Knap,
Jan W. Pilarczyk,
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摘要:
A scheme of force variation during the compression of a spring in both elastic and elastic‐plastic state is presented. For the elastic state it has been found that equivalent load increments occur with equivalent deflection increments. In the elastic‐plastic state equivalent load increments correspond to higher deflection increments. Prestressing the spring increases the range of the elastic deformation of a spring. Equations for the determination of torsional moment during prestressing and relationships of total non‐dilatational strain versus elastic strain and radii of elastic zone are also presented. The effect of characteristic spring dimensions and non‐dilatational strain on spring deflection has been determined. A nomogram for the determination of the resultant equivalent strain as a function of external load, also considering residual stress distribution, has as well been elaborated.
ISSN:0003-8962
DOI:10.1002/srin.199501149
出版商:Wiley
年代:2016
数据来源: WILEY
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5. |
Retained austenite and mechanical properties in bainite transformed low alloy steels |
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Archiv für das Eisenhüttenwesen,
Volume 66,
Issue 10,
2016,
Page 433-438
Gregory Haidemenopoulos,
Katerina Papadimitriou,
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摘要:
Uniform ductility and formability of low alloy steels can be improved by the transformation plasticity effect of metastable retained austenite. In this work, intercritical annealing followed by bainite transformation resulted in the retention of austenite with sufficient stability for transformation plasticity interactions. The effect of retained austenite on mechanical properties was studied in two low‐alloy steels. Bainite transformation was carried out in the range of 400 to 500°C. The strength properties (yield strength and ultimate tensile strength) were more sensitive to bainite isothermal transformation temperature than holding time. Maximum strength properties were obtained for the lower transformation temperatures. On the other hand, high uniform and total elongation values were obtained at lower transformation temperatures but were sensitive to bainite isothermal transformation time. Variations in uniform elongation with holding time were linked to variations in retained austenite stability. Maximum values of uniform elongation occurred at the same holding times as the maximum amount of retained austenite. The same was true for total elongation and ultimate tensile strength. The above results indicate a strong correlation between retained austenite stability and uniform ductility and suggest that further optimisation regarding chemical composition and processing with respect to austenite stabilisation may lead to a new class of triple‐phase high‐strength high‐formability low‐alloy steels.
ISSN:0003-8962
DOI:10.1002/srin.199501150
出版商:Wiley
年代:2016
数据来源: WILEY
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6. |
Localised corrosion behaviour of high and low nitrogen Cr‐Mn steels |
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Archiv für das Eisenhüttenwesen,
Volume 66,
Issue 10,
2016,
Page 439-443
Ahila Srinivasan,
Brigitte Reynders,
Hans Jürgen Grabke,
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摘要:
It is well established that addition of nitrogen to steels improves the pitting corrosion resistance of steels. To elucidate the role of nitrogen, electrochemical and surface analytical studies were carried out on Cr‐Mn steels with low (0.0075 %) and high (0.9 %) nitrogen contents. The incubation time for pitting, measured in sodium sulphate solutions containing different concentrations of chloride was higher for the high nitrogen steel. The pit initiation process was found to be first order with respect to chloride concentration. The passive current density was one order lower than that of nitrogen free steel. The grain broundary attack observed in low nitrogen steel was not present in high nitrogen steel. XPS analysis indicated nitrogen enrichment at the surface in the passive layer. This may be one reason for the higher pitting resistance of nitrogen containing steel besides formation of ammonium ions and rising pH.
ISSN:0003-8962
DOI:10.1002/srin.199501151
出版商:Wiley
年代:2016
数据来源: WILEY
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7. |
Neural nets – types, configurations and pitfalls |
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Archiv für das Eisenhüttenwesen,
Volume 66,
Issue 10,
2016,
Page 444-448
Ernst Dieter Schmitter,
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摘要:
Fuzzy logic, neural nets and genetic algorithms form the core of soft computing methods. They are useful when there is no possibility to compute an exact mathematical model (hard computing). Neural nets have the ability to learn by example. This advantage is exploited by a lot of applications and many software packages make it quite easy to use neural nets. A stage is reached, where some critical remarks should be made in order to avoid disappointments. Some frequently used net types (backpropagation, LVQ, SOM) are discussed together with configuration and training problems. Important topics are the avoidance of under‐ and overfit and the remark that neural nets produce correct outputs only if the inputs lie in the part of the feature space, the net was trained for. Therefore, a detailed analysis of the training data set should be made. In the context of safety relevant applications the missing interpretability of neural net outputs is often criticized. Fuzzy‐neuro‐systems try to improve this situation.
ISSN:0003-8962
DOI:10.1002/srin.199501152
出版商:Wiley
年代:2016
数据来源: WILEY
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8. |
Automatic grain size determination and classification of iron carbides with neural nets |
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Archiv für das Eisenhüttenwesen,
Volume 66,
Issue 10,
2016,
Page 449-453
Ernst Dieter Schmitter,
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摘要:
Under the aspect of quality assurance material testing is getting more and more important. As a consequence there is a strong demand for automation and objective procedures. This article concentrates on the inspection of polished steel specimens using image processing and intelligent software techniques. Nowadays computer aided image processing of microstructures is widely used, but final analysis and quality grading are based on the experience of the testing personnel. Using intelligent software techniques (soft computing), especially neural nets, allows complex decision processes to be done on a computer in a reproducible manner. Of course there are certain premises: suitable restriction of the application domain, careful image preprocessing and feature extraction, critical surveillance of the training process. The article focuses on two neural net applications: grain size determination and classification of iron carbides. To learn the ability to do complex decisions in a reproducible manner from a suitable example data set – at least in a restricted domain – is the main advantage of a neural net solution.
ISSN:0003-8962
DOI:10.1002/srin.199501153
出版商:Wiley
年代:2016
数据来源: WILEY
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