bluuebunny/crossref_metadata_2025 huggingface dataset:
Alloying steel with nitrogen from gas phase in high‐pressure plasma reactor
Authors: Tochowicz Stanislaw , Siwka Jerzy , Jowsa Jan
Published: December 2016

The paper presents a study of the possibility of saturating austenitic Cr18%–Mn18% steel with nitrogen from the gas phase by use of “low – temperature” thermal plasma. The experimental work was carried out in a DC plasma reactor of the authors' own design working at a total gas pressure of 0.38 MPa on a 20 kg sample. It was evident that it was possible to obtain a very high level of nitrogen saturation close to the level of nitrogen solubility in the metal by the use of plasmogenic gas containing purified nitrogen. The highest content of nitrogen in steel containing 18wt.% chromium and 16.7wt.% manganese was 0.77wt.% at [C] = 0.054. Refining the metal with CaSi additive turned out to have a stabilizing influence, the total amount of oxygen and sulphur being lower than 200 ppm. The material obtained turned out to be also highly homogeneous chemically after solidification.
Tempering characteristics of a Cr‐Mo dual phase steel
Authors: Jha Bimal K. , Avtar Ram , Dwivedi V. Sagar , Mishra Nirmalendu S.
Published: December 2016

Full potential of dual phase steels in as‐hot rolled condition is not being realized at present because of certain difficulties associated with coiling as well as welding. Autotempering of martensite may lead to anomalous properties at different locations in the coil. An industrially as‐hot rolled Cr‐Mo dual phase steel has been chosen to study its tempering behaviour. The response to tempering by varying temperatures for a fixed time interval of one hour has been monitored through evolution in microstructure, as revealed by transmission electron and light microscopy on the one hand, and measurement of mechanical properties on the other. An attempt has been made to establish structure‐property correlation for different tempering treatments. Two temperature regimes have been identified: the one below 300°C, wherein no significant change in microstructure occurs while the other above 300°C is marked by the precipitation of ∊‐carbide and its subsequent dissolution to give way to the formation of cementite. The observed maximum in the yield stress at ∼300°C is linked with the precipitation of ∊‐carbide. The onset of softening thereafter has been shown to be due to the formation of subcells in ferritic regions and recovery taking place in the martensitic phase together with globularization of cementite. The ductility minimum has been observed at ∼400°C and this has been attributed to the segregation of impurities to the grain boundaries.
On the stability of retained austenite and its role in improvement of the cryogenic toughness for Ni9 steel
Authors: Zhang Futian , Hu Man , Lou Zhifei
Published: December 2016

The relationship between the mechanical stability of retained austenite(γ') and the cryogenic toughness of Ni9 steel has been investigated and the phenomena of γ' → martensite(α') transformation in the process of impact deformation‐fracture have been observed. The results show that the role of γ'‐phase itself is beneficial to cryogenic toughness but rather small, the main reason of good cryogenic toughness in large margin is perhaps γ' → α' transformation performed in process of the impact‐fracture.
Reduction equilibria of the calcium ferrites in the Fe‐Fe2O3‐CaO system as a function of oxygen concentration and temperature
Authors: Schürmann Eberhard , Janhsen Urban
Published: December 2016

The results of isothermally conducted reduction tests on the calcium ferrites CF2+F (= 20 mol. % CaO), CF2 (= 35 mol. % CaO), CF (= 50 mol. % CaO) and C2F (= 66.7 mol. % CaO) with CO/CO2‐bearing gases of changing composition in the temperature range between 700 and 1100°C lead both to a plot of the specimen's weight loss as a function of the test duration with the reduction potential CO'2 of the inlet gases as parameters, and to a preciser determination of the reduction stages by means of a plot of the reduced iron oxide oxygen as a function of the CO'2 concentration of the reducing gas. The weight losses are attributable to the three‐phase equilibria with the ternary compounds CWF and CW3F contained in the Fe‐Fe2O3‐CaO phase diagram. Further evaluation taking account of temperature‐dependent reduction reactions leads, on the one hand, to a complete reduction diagram for iron oxides with lime in the form of log CO2/CO as a function of MT with largely linear equilibrium curves and, on the other hand, to the familiar Baur‐Glaessner diagram, the reduction potential CO'2 as a function of temperature. The main finding compared with previous literature is the existence of the ternary ferrite CW3F extending into the liquid phase, and the fresh determination of the temperatures for the four‐phase equilibria in the Fe‐Fe2O3‐CaO system below 1100°C.
A method for the calculation of temperature during hot rolling of bars and rod
Authors: Braun‐Angott Peter , Rohloff Hans
Published: December 2016

A semi‐analytical finite element method is presented which enables the calculation of temperature distribution over the cross‐section of the rolling stock as it passes through the individual stands and cooling zones of a wire rod mill. Conformal mapping techniques have been used to subdivide the numerous cross‐sectional areas that occur during rolling into suitable macro‐elements. The system of ordinary differential equations resulting from the application of Galerkin's method to the diffusion‐convection equation is solved by means of the eigenvalue method. The accuracy of the developed mathematical method was checked by means of comparison with numerical results obtained from the conventional finite element method. The method is an integral part of a complete process model predicting the temperature distribution of wire rod and bars during hot rolling to be dealt with later.
The mechanism of hot straining embrittlement of mild steel
Authors: Lei Weisheng , Yan Xiangqiao , Yao Mei , Tian Xitang
Published: December 2016

Cleavage‐characteristic stress, Sco, a new parameter relating to resistance of cleavage fracture, was introduced to study the mechanism of hot‐straining embrittlement (HSE) of mild steel. It was concluded that with hot strain aging, cleavage‐characteristic stress Sco remains unaffected and thus, the mechanism of hot‐straining embrittlement lies in the increase of yield strength due to hot strain aging effect.
Thermodynamics of oxygen, nitrogen and sulfur in liquid iron equilibrated with CaO‐TiOx and CaO‐Al2O3‐TiOx melts
Authors: Kishi Mikine , Suito Hideaki
Published: December 2016

Equilibria between CaO‐TiOx or CaO‐Al2O3‐TiOx melts and liquid iron with respect to O, N and S were studied at 1873 K as a function of Ti (or Al) content in metal, using a CaO or an Al2O3 crucible. The Al‐O and Ti‐O relations in liquid iron were studied, and nitride and sulfide capacities defined by and , respectively, were obtained from nitrogen and sulfur distribution ratios, coupled with the analyzed oxygen content in liquid iron or the PO2 determined by Ti/TiO2 equilibrium. Based on these results, activities of Al2O3 and activity coefficients of TiO2 and TiO1.5 were evaluated.
CaO‐activities and structure of CaO‐Al2O3‐melts
Authors: Nowack Norbert
Published: December 2016

By using structure chemical results taken from IR‐spectroscopic analyses, the CaO‐activity was calculated. In liquid state the aluminates dissociate into Ca2+ and into the complexes and . By application of the Temkin‐theory the CaO‐acitivity can be calculated and compared with measured values.
Numerical results of temperature distribution and solidification behaviour during spray forming
Authors: Fritsching Udo , Zhang Hong , Bauckhage Klaus
Published: December 2016

Based on a grid transformation method, the temperature and solidification behaviour in the substrate and deposit for the spray forming process of metals has been simulated. Numerical results will be compared with experimental data of temperature measurements in the deposit and substrate. Some limitations of this model will be outlined.
Solubility of nitrogen in austenitic FeCrMn alloys
Authors: Kunze Joachim , Rothe Ines
Published: December 2016

The equilibrium solubility of nitrogen in austenitic iron‐chromium, iron‐manganese, and iron‐chromium‐manganese alloys with mass up to 20 % Cr and 18 % Mn was measured in the temperature range 1273 to 1473 K. The following interaction parameters were obtained:

urn:x-wiley:01774832:srin01081:equation:srin01081-math-0001

Describing the effect of chromium and/or manganese on the nitrogen solubility by the excess term , the present measurements correspond satisfactorily to those of Hertzmann and Jarl and of Zheng in the system Fe‐Cr‐N, but they differ somewhat from values calculated by means of parameters published by Frisk. For the system Fe‐Mn‐N the present measurements correspond to measurements by Grabke et al. and to values calculated with parameters published by Qiu. Using parameters deduced from the present measurements in the austenitic Fe‐Cr‐Mn‐N system similar nitrogen solubilities were calculated as Zheng had measured, but small deviations were found between the analysis by Qiu and this investigation.
Genetic adaptive search model of hot metal desulphurization
Authors: Rastogi Ravi , Deb Kalyanmoy , Deo Brahma , Boom Rob
Published: December 2016

Genetic adaptive search (GAS) techniques, based on the mechanics of natural genetics, are used in this paper to find an optimal model of desulphurization process of iron‐melt by powder injection. Industrial data on 400 t torpedo are used to evaluate contributions of transitory and permanent contact reactions to the overall desulphurization process during calcium carbide powder injection. The results obtained with GAS agree more closely with the plant data than the theoretical model. GAS solutions are also found to be better than regression models. These results suggest immediate application of GAS in similar metallurgical problems.
Application of fuzzy sets and neural network theory to the numerical pattern recognition of bubble flow and jet flow
Authors: Franzen Andreas , Pluschkell Wolfgang
Published: December 2016

The injection of gas into a liquid is associated with two characteristic flow regimes: bubble flow and jet flow. In metallurgy, these flow regimes are of interest with respect to refractory lifetime and mass transfer. The flow regimes were investigated in the systems water‐air and ethanol‐air by monitoring the bottom vibrations of a cold model. The vibrations were analyzed by numerical pattern recognition. The nominal Mach number of 1.1 is the criterion for the transition from bubble flow to jet flow. A numerical pattern recognition system which is able to distinguish between the flow regime below and above the nominal Mach number of 1.1, just by analyzing the vibration signal, is presented. This task can be accomplished in spite of the use of different liquids, nozzle diameters and liquid heights. As a classificator, both a fuzzy k nearest neighbour algorithm and a neural network were employed successfully. Fuzzy logic was found to be especially useful for describing the different flow regimes.
Control of the manganese‐oxygen reaction in pure iron melts
Authors: Dimitrov Stefan , Weyl Axel , Janke Dieter
Published: December 2016

EMF sensor measurements using ZrO2(CaO) or ThO2(Y2O3) plug‐type sensors with a Cr‐Cr2O3 reference were performed to redetermine the Mn‐O equilibrium reaction. In these experiments a strong effect of deoxidation of manganese was ascertained at saturation with solid deoxidation products. The measuring interval of the sensors at MnO saturation was limited to about 12 min due to chemical corrosion of the used Al2O3 sheaths. In the case of double saturation with solid MnO · Al2O3 (MA) and Al2O3 (A) the sensors could be used as long as desirable. Moreover, the combined deoxidation of the iron melt with Mn and Al was investigated. An auxiliary electrode at the tip of the sensor ensured rapid saturation of the iron melt with solid MnO or MnO · Al2O3 + Al2O3.
Morphology of hematite to magnetite reduction zone
Authors: Janowski Jan , Wyderko‐Delekta Marta , Sadowski Andrzej , Delekta Jerzy
Published: December 2016

The reduction process of hematite to magnetite results in distinct changes in morphology of magnetite. These changes depend on structural properties of parent hematite and reduction conditions. The reduction experiments were performed in 3% CO and 97% CO2 gas mixture at 450 and 850°C on selected crystals of natural hematite. The phase composition and morphological characteristics of the reduced layer were determined on the basis of microscopic analysis. Singular blasts or blastoidal colonies of magnetite were formed in 450°C on the boundaries of the hematite grains. They began to grow and joined the layer. Magnetite formed at 450°C is distinctly microporous. Cracks and desintegration of hematite grains appear together with reduction of hematite. At 850°C nucleation of the magnetite is quite different then at 450°C. The formation of singular magnetite lamellae or a palisade of crystallographically oriented magnetite lamellae were observed. Their growth results in the formation of the magnetite layer. Tunnel‐shaped pores in magnetite layer show the same direction as lamellar front of reduction.
Solubility of Zn and Pb in liquid iron and their partition between liquid iron and selected steelmaking slag systems
Authors: Li Lutao , Weyl Axel , Janke Dieter
Published: December 2016

The use of Zn‐ and Pb‐contaminated scrap in steelmaking has led to a significant increase of the zinc and lead contents in dusts and sludges, especially produced in the electric arc furnace melting shops. To understand the behaviour of Zn and Pb, fundamental research on the thermodynamics and kinetics of zinc and lead reactions under steelmaking conditions is helpful. In the first part of the present work, the solubilities of lead and zinc in iron are discussed. Furthermore, the influence of several alloying elements, such as carbon, oxygen, sulfur and chromium on the dissolution behaviour of Zn and Pb was examined and compared with former studies. Measurements of the solubility of lead in liquid iron were made at elevated temperatures in the systems Fe‐Pb‐O, Fe‐Pb‐C and Fe‐Pb‐Cr under argon in a gas‐tight Tammann furnace. An increase of lead solubility was found with increasing temperature and increasing oxygen content. On the other hand, higher contents of carbon and chromium led to lower solubilities of lead in liquid iron. In the second part, the partition ratios of zinc and lead between liquid iron and various selected slag compositions were investigated. It is shown that zinc partition is determined by oxygen activity and slag basicity. In SiO2‐saturated slags, the partition ratio of zinc is considerably higher than in CaO‐saturated slags. In comparison, the partition ratio of lead is significantly lower under the same experimental conditions.
Tracking of cracks in sheet steel specimens under cyclic loading
Authors: Biswas Kalyan , Drewes Ernst‐Jürgen , Schulte Manfred
Published: December 2016

In this report a non‐contact gauging system based on eddy current technology is presented which permits unproblematic detection and tracking of cracks initiated by cyclic loading in sheet steel specimens. In comparison with other measuring methods the automatic pilot unit developed displays distinct advantages thanks to its highly accurate measuring results. This measuring unit is suitable for the examination of thin sheet steels (< 2 mm) and has been successfully used for studying ductile materials. Some results of such investigations are therefore illustrated.
Classification of blast furnace probe temperatures using neural networks
Authors: Bulsari Abhay , Saxén Henrik
Published: December 2016

Classification of spatially distributed measurements in industrial processes is often a difficult task. A typical example is given by the interpretation of the gas temperatures from horizontal probes in blast furnaces. This paper presents a neural network‐based classification of temperature measurements from an above‐burden probe. An expert on blast furnace supervision and control first classified a large set of temperature profiles into six different stereotype patterns. Roughly 40 % of this material was used for training feedforward neural networks, while the remaining profiles were used for evaluation of the networks' performance in order to determine an appropriate network size. In general, consensus was found among the networks in that similar erroneous or inconsistent classifications made by the human expert were detected. However, the network size clearly affected the quality of the classifications. The work demonstrated the merits of a rapid, consistent, and automatic (neural) interpretation, as well as the risk of misclassification and the subjectivity involved when human experts have to evaluate complex patterns.
A new, optical measuring technique for the determination of the vapour film thickness during film boiling
Authors: Weichert Reiner , Jeschar Rudolf , Klemm Walter , Heidt Viktor , Thibor Patrick , Mühlenweg Heike
Published: December 2016

A non‐contact measuring technique was developed and tested to determine the thickness of a vapour film during film boiling. The technique is based on the different optical properties of vapour and water admixed with a fluorescent substance. Pictures were taken of the surroundings of the vapour film using a long‐distance microscope of high resolving power and a TV‐camera; they were recorded with a video recorder. The pictures were evaluated using methods of digital image processing and by application of a model for the intensity distribution of fluorescence‐radiation. The technique was tested on a steel sphere heated to 690°C and subsequently immersed into warm water of 55°C. The thickness of the vapour film directly after immersion was determined at 0.20 mm. The thickness decreased continuously during the cooling process and reached a thickness of 0.11 mm after 20 s, immediately before the collapse of the vapour film. The surface temperature of the steel sphere immediately before the collapse was about 420°C. The thicknesses of the vapour film calculated with a simple theoretical model were found to be about 50 % smaller than those measured.
Component specific influences on the fracture behaviour of high speed steels under static loading
Authors: Lippmann Nils , Spies Heinz‐Joachim
Published: December 2016

This paper presents the first results of a series of investigations into the fracture behaviour of high speed steels with regard to component specific influences. The aim of the investigations was the analysis of the interaction of internal and external notches during the fracture process. Hardened and tempered high speed steel S 6‐5‐2 of various degrees of hot forming, which was produced by electroslag remelting, as well as powder‐metallurgically produced high speed steel ASP 23 were tested to investigate the influence of different carbide sizes and distribution.

In‐situ bend tests showed the role of the carbides as fracture initiating defects, which form subcritical cracks as a result of the higher stiffness and lower failure stress at loads smaller than the global failure load of the specimen. The observed fracture process was simulated by FEM using the observations and results of the in‐situ bend tests.

The interaction of internal flaws and external notches was proven using notched and coated specimens as well as specimens of various surface roughness. The fracture initiating defect is the largest defect in the loaded volume regardless of whether it is an internal flaw (carbide) or an external notch (surface roughness, surface layer). Information can be derived from the investigations allowing the optimisation of the manufacture of high speed steel tools with regard to their fracture behaviour.
Structure forming processes during hot deformation of a C‐Mn‐V‐N steel
Authors: Adamczyk Jan , Carsi Manuel , Kozik Roman , Wusatowski Roman
Published: December 2016

Medium carbon V‐N treated steel grade applied for long products and small drop forged parts investigated in a state of incomplete solution of V(C,N) precipitates. Activation energy changes investigated in the 850–1200°C temperature range and 0.6–30 s−1 strain rate range is revealed to be temperature dependent. Calculated for σp flow stress value this energy in some cases expresses a combination of various processes. It is found that DRX starts well below ∊p. Softening during a short interpass time is caused by dynamic recrystallization DRX during forming and is followed by metadynamic recrystallization MDRX and static recrystallization SRX. At longer interpass times softening progress is hindered by precipitation.
Elimination of copper from the molten steel by NH3 blowing under reduced pressure
Authors: Ono Katsutoshi , Ichise Eiji , Suzuki Ryosuke O. , Hidani Toshitsugu
Published: December 2016

Based on the finding that blowing of NH3 gas onto molten pure copper at atmospheric pressure causes an evaporation of an enormously high rate, attempts have been made to eliminate copper dissolved in molten steel by NH3 gas blowing under reduced pressure. Typical behaviours of molten steel when attacked by NH3 gas are boiling, splashing and, in a violent case, slopping from the crucible. These phenomena are accompanied by an immense increase in the surface area from which volatile species are able to evaporate and may be useful for vacuum metallurgical processes. In this investigation, the decuprization experiments have been conducted to measure the rate at which the copper level in the molten steel is reduced using a vacuum induction furnace and blowing NH3 gas through a vertical water‐cooled copper nozzle. The data were represented in terms of the amount of copper transferred from the melt to the gaseous phase per unit surface area and time. According to these experiments, complete decuprization was attainable confirming selective evaporation of copper from molten steel under reduced pressure. So far as the mechanism of copper elimination by NH3 gas, besides the enhanced vacuum evaporation of metal by the cooling effect of endothermic decomposition of NH3, the formation of volatile copper compound was suggested from the fact that the copper could be removed down to an extra‐low level of several ppm, even under a residual gas pressure of the order of 10 Torr.
3‐D simulation of metal forming processes with automatic mesh generation
Authors: Tekkaya Ahmet Erman , Kavakli Sebahattin
Published: December 2016

The numerical simulation of industrial metal forming processes requires robust and feasible solution methods. In this context, any solution procedure must be able to handle three‐dimensional problems with general contact conditions and severe deformations. The latter condition necessitates automatic mesh‐generation abilities. At the same time, the simulation tool must be economical and user‐friendly. In this paper, a solution procedure is introduced which is able to perform the numerical simulation of complex industrial metal forming processes without any interference. The procedure is based on the rigid‐plastic finite element method and is primarily suited to the analysis of bulk metal‐forming processes. To ensure a real automatic simulation, the numerical procedure is made robust by using Euler time integration, a Newton‐Raphson solver which is coupled with a direct iteration solver, a linear contact algorithm and, finally, a completely automatic hexahedral mesh generation scheme. The method is implemented in the ANSI‐C programming language. To demonstrate the effectiveness of the method an industrial application has been simulated: A spider produced from a cylindrical initial workpiece by cold radial‐extrusion.
A new creep equation for ferritic and martensitic steels
Authors: Bartsch Herbert
Published: December 2016

Creep rupture tests lasting 100 000 h at temperatures between 500 and 650°C were conducted on X22CrMoV12‐1 rods. An equation has been derived from the measured creep data for the primary and the beginning of the secondary creep range of the following form

urn:x-wiley:01774832:srin01142:equation:srin01142-math-0001

A new element in the equation is the description for the dependency on stress f(σ) which was obtained from the stress dependency in the Norton equation

urn:x-wiley:01774832:srin01142:equation:srin01142-math-0002

The new equation allows the description of the creep behaviour up to a strain of 0.5 %. Using the equation, the corresponding stress can be calculated to an accuracy of ±10 % from the strain limits determined in relation to time during creep rupture tests (above 0.1 % strain).
Microstructure and deformation rate during long‐term cyclic creep of the martensitic steel X22CrMoV12‐1
Authors: Straub Stefan , Hennige Thomas , Polcik Peter , Blum Wolfgang
Published: December 2016

The microstructure of three specimens of the martensitic steel X22CrMoV12‐1 which had been subjected to long‐term cyclic creep at 873 K with intermittent phases of unloading (stress ratio R = 0) and compression (R = −1) was quantified by electron microscopy with regard to carbides, dislocations and pores. The laws of time dependent coarsening of carbides and strain controlled growth of subgrains found for monotonic creep hold also for cyclic creep. The longer time it takes cyclic creep to reach a given strain leads to a growth advantage of carbides compared to monotonic creep. The microstructural model of plastic deformation previously developed for monotonic creep on X20(22)CrMoV12‐1 allows to calculate the cyclic creep acceleration due to this advantage in carbide growth.
Retained austenite and mechanical properties in bainite transformed low alloy steels
Authors: Haidemenopoulos Gregory , Papadimitriou Katerina
Published: December 2016

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.
Neural nets – types, configurations and pitfalls
Authors: Schmitter Ernst Dieter
Published: December 2016

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.
Automatic grain size determination and classification of iron carbides with neural nets
Authors: Schmitter Ernst Dieter
Published: December 2016

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.
Improvements in the combustion method for the determination of low carbon contents in steel
Authors: Gruner Wolfgang , Grallath Erhard
Published: December 2016

For the reliable determination of carbon contents of a few μg/g in low and ultra‐low carbon steels by the combustion method with commercially available carbon analyzers special measures as surface cleaning by chemical etching, pre‐treatments of crucible and accelerator materials, or in‐situ desorption of contaminations have to be taken. A new technique including firstly, the pre‐burning of copper for degassing the ceramic crucible and, secondly, the desorption of carbonaceous contaminations from the surface of the sample and the Cu‐accelerator by placing together into the still hot crucible yields a detection limit of about 0.5 μg/g carbon. The technique was checked with granular and compact iron samples, and the results were compared with those of investigations with special devices for fractionated, temperature controlled combustion.
Simulation of austenitic microstructure in rod and wire rolling of quenched and tempered steel grades
Authors: Lehnert Wolfgang , Cuong Nguyen Duc , Wehage Harald
Published: December 2016

The determination of the microstructural and forming parameters of rods and wire from low to medium‐alloy quenched and tempered as well as spring steel grades is a prerequisite for the mathematical modelling and optimization of the technology on the basis of process and material criteria. Using the boundary, heat balance and finite difference methods as well as visioplastic investigations, the most important forming parameters were determined in high‐speed rolling. The rolling of such steel grades allowed to determine the material constants for the dynamic and static equations of recrystallization. Due to the inhibitive effect of the alloying elements (Mo, V) the investigated steel grades display a comparatively pronounced recrystallization inertia. Accordingly, the austenitic post‐recrystallization grain size is very fine and relatively independent of the temperature. Temperature control during rod and wire rolling allows to influence and adjust the austenitic microstructure prior to phase transformation.
Effect of cryoforming of austenitic Cr Ni‐steels at 77 K on martensitic transformation and work‐hardening characteristics
Authors: Weiß Andreas , Fang Xiangfan , Eckstein Hans‐Joachim , Eckstein Christine , Dahl Winfried
Published: December 2016

The effect of cryoforming at 77 K on the flow and work‐hardening characteristics was investigated considering the martensitic transformation behaviour in austenitic Cr Ni steels with different nickel contents. The test steels can be divided into two groups relating to the flow and work‐hardening characteristics and martensitic transformation behaviour at 77 K. The first group comprises steels with less than 16 % nickel, the second group those with more than 16 % nickel. The flow curves of the first‐group steels show two inflection points on the basis of γ → α'‐transformation. αγ'‐martensite is observed and ∊‐ and α∊'‐martensite too. The flow curves of the second‐group steels do not show any inflection points. The γ → α'‐martensitic transformation is not induced, ∊‐ and α∊'‐martensite are provable by light and scanning microscopy. The stress‐strain intervals were determined for the individual martensite transformations at 77 K in the test steels. They are dependent from the nickel content. The stress which specifies the first inflection point on the flow curve and the minimum of the work‐hardening rate, respectively, characterizes the stress for initiating the deformation‐induced αγ'‐martensite formation. Transformation of the austenite to α' martensite will end in achieving a stress of 1200 to 1400 MPa, i.e. in achieving the second inflection point of the flow curve and the maximum of the work‐hardening rate, respectively. The stress interval is not dependent from the nickel content.
Development of a model for the simulation of the transfer of surface structure in the temper‐rolling process
Authors: Steinhoff Kurt , Bünten Rolf , Rasp Wolfgang , Kopp Reiner , Pawelski Oskar
Published: December 2016

In the temper rolling process the effect of transferring the roll‐surface structure to the steel sheet is purposely used to adjust a defined sheet‐surface structure required for further processing. At the moment four different texturing techniques (SBT, EDT, EBT, LT) are available for the production of specified roll‐surface structures; these techniques are based on two fundamental mechanisms; plastic deformation and local melting. The objective of the investigation presented in this paper is to analyze the transfer behaviour specific to the texturing technique used and, in addition to that, to develop a model for the simulation of these transfer characteristics. For this purpose in the first part the results of a comparative study on the basis of rolling tests on an industrial temper mill are presented. These results do not only point out the basic transfer mechanisms – penetration processes and reverse extrusion phenomena – but beyond that also lead to an explanation of the transfer behaviour specific to the texturing systems by the application of similarity numbers (substitute profile model). Possible reasons for the different transfer behaviour are on the one hand wear effects and on the other hand process‐induced characteristics of the structure itself (e.g. isolated lubrication pockets). On the basis of these results in the second part a model is developed to simulate the transfer characteristics by the application of the finite element method (FEM).
Direct creep curve assessment and optimization of creep equations for high temperature alloys
Authors: Kloos Karl Heinz , Granacher Joachim , Pfenning Andreas
Published: December 2016

The conventional use of a time temperature parameter method for the basic assessment of a multi‐heat creep data set facilitates the establishment of a creep equation for a material type. However, the parameter can introduce some distortion to the creep data and hence the creep equation. To avoid this disadvantage, a new method for the direct creep curve assessment of multi‐heat data was developed. Systematic deviations in creep behaviour of individual test materials in respect to the mean behaviour of the multi‐heat data set are reduced and the creep curves for individual stresses are transformed to mid creep curves of a limited number of stress classes. With this method large multi‐heat creep data sets of Alloy 100 and Alloy 738 LC could be reduced to mean creep curves. On this basis, existing parameter based creep equations were examined and optimized, if necessary. Further, the confidence limits of these equations were determined. With a stress modification the creep behaviour of a material similar in structure can be described. In finite element analyses some verification experiments which simulate typical loading conditions of components could be successfully recalculated with the optimized creep equations.
Investigation of the sedimentation of FeNi fine grains entrained in ERF slag
Authors: Diamantopoulos Adamantios S. , Angelopoulos George N. , Papamantellos Demetrios C.
Published: December 2016

Nickel losses in the slag generated at Larco electric reduction furnaces (ERF) during smelting of Greek laterites account for about 20% of the total nickel of the feed. The recovery of the nickel contained in the slag as well as in its magnetic concentrate was studied under different methods. The experimental results have shown that a nickel recovery in the range of 75‐90% is possible by allowing the slag to settle. Washing by low carbon steel can be performed during the final stages of the settling process as it improves the finally attained nickel recovery up to 94.4%. The simultaneous carbon reduction and settling process do not favour the Ni‐ recovery as the produced carbon monoxide and dioxide cause boiling of the bath which promotes the flotation of the metallic grains. In all cases a reoxidation of nickel was observed after 20min approximately. Settling of the ferronickel grains was described by a mathematical model. The model's results are in good agreement to the experimental ones for the initial 20min of the process. A modified model was elaborated combining the settling of the metallic grains with the nickel reoxidation reaction. This model describes with adequate accuracy the whole Ni‐ recovery process. The developed model can be proven helpful in the design of a slag cleaning step for metal recovery utilizing a slag settling furnace operating on line to the ERF.
Influence of roll geometry and strip width on flattening in flat rolling
Authors: Zhou Shunxin , Funke Paul , Zhong Jue
Published: December 2016

The size of local roll flattening and its distribution along the direction of the roll axis in flat rolling were calculated by means of 3‐dimensional finite element method. For analysis of elastic flattening deformation of the roll stack the well‐known classical and analytical solutions are usually employed which were derived from elastic half space theory or two dimensional contact theory. By comparison of results from both the different methods the validity of the classical formulae was examined. Some of the formulae are more appropriate for calculating local flattening along the work roll/strip interface, however, they may result in a great deviation in calculating the flattening along the work roll/ back‐up roll interface, especially for the back‐up roll. Using the Fe model the influence of roll geometry and strip width under a specific rolling force on the flattening was taken into account, which is difficult to be treated with classical models.
Artificial neural nets for prediction of silicon content of blast furnace hot metal
Authors: Singh Himanshu , Sridhar Nallamali Venkata , Deo Brahma
Published: December 2016

Conventional models for prediction of silicon content of blast furnace hot metal are briefly reviewed. Four different artificial neural net (ANN) models, namely, back propagation algorithm (BPA), dynamic learning rate algorithm, functional link network (FLN) and fuzzy neural network (FNN), are trained and tested on operational data from blast furnace (BF1) at Visakhapatnam Steel Plant. FNN can predict silicon mass content of hot metal with a standard error (actual versus predicted) of 0.09% and correlation coefficient of 0.86; standard back propagation predicts with a standard error of 0.08 % and correlation coefficient of 0.79.
Prediction of metallic materials creep deformation under multiaxial stress state
Authors: Batsoulas Nikolaos D.
Published: December 2016

A simple function of multiaxial creep is presented hereafter. This is derived from a uniaxial creep function with only three fitting parameters. For the derivation of the multiaxial function the only assumption made was the one of material's isotropy. With the additional assumption of constant volume, the function leads to a v. Mises‐type function of multiaxial creep. The equivalent stress employed has a simple form as well and leads to the v. Mises equivalent stress. The derived curves agree with the experiments, not only the ones carried out in the laboratory but also the ones taken from literature.
Influence of strain rate on ductility of metallic materials
Authors: El‐Magd Essam
Published: December 2016

The flow behaviour of iron and steel X 2 CrNiMo 18 10 is studied in impact tension tests with strain rates between 1000 and 7000 s−1 on smooth specimens and on notched bars. The neck formation is discussed on the basis of the theory of imperfections. The temperature increase during the adiabatic process promotes deformation localisation and instability. However, the stabilising effect of the strain rate sensitivity is dominating and leads to an increase in ductility. On the other hand, increased strain rates reduce the local fracture strain leading to an increased dynamic notch sensitivity. Through combination of experiment and simulation, the location of void initiation could be estimated and the influence of strain rate on the local failure strain could be determined.
Grain size effects on flow stress in hot compression test
Authors: Perttula Juha , Karjalainen Pentti
Published: December 2016

Flow stress data on fine‐grained material are needed for FEM modelling of the final passes in hot rolling. However, a fine grain size may be difficult to retain in reheated specimens for hot compression tests, and the flow stress usually has to be determined using specimens with rather coarse grain sizes. The results for several steels tested in austenitic condition show that the increase in grain size from about 15 μm to 50 μm causes a decrease of 5 − 25% in the mean flow stress (calculated over the strain range of 0 − 0.15) and further coarsening has hardly any influence. The effect of grain size Variation can be described by respective alterations in the strain‐hardening exponent and it can be accounted for by mathematical correction.
Laser‐beam surface transformation hardening of hypoeutectoid Ck‐60 steel
Authors: Katsamas Anthony I. , Zervaki Anna D. , Haidemenopoulos Gregory N.
Published: December 2016

A carbon dioxide laser with a power of 1.5 KW was employed for surface hardening of a hypoeutectoid Ck‐60 steel. The microstructures and hardness profiles were determined as a function of power density and laser beam travel speed. The microstructure in the laser‐beam hardened zone depended on power density and consisted of plate martensite (for high power density) or autotempered martensite (for low power density). In the transition zone of the laser‐beam treated specimens, martensite and ferrite were observed. Case depth and maximum hardness were found to depend on power density and travel speed. A simple one‐dimensional heat flow model has been used for the selection of process parameters and for the prediction of case depth. Calculated and experimentally determined case depths are in good agreement for medium values of power density.
Material property database for heat treatment simulation of tool materials
Authors: Thuvander Anders , Blom Roland , Jin Lai‐Zhe , Sandström Rolf
Published: December 2016

A materials data base has been set up with mechanical, thermophysical and transformation properties of tool and creep resistant steels. In particular powder metallurgical materials have been covered. The intended use of the data is for numerical simulation of heat treatment with focus on computation of residual stresses and distortion in Compound materials (macro composites).

The main body of the data was generated in new experiments. In this paper data for the powder metallurgical high speed steel ASP 2060 will be presented. The material properties determined include thermophysical data such as thermal conductivity and specific heat, mechanical data such as yield strength and work hardening rate, and thermal expansion data. Most data were determined at different temperatures and after heat treatments to different microstructures. Additional data added to the database include literature data for elastic properties and transformation induced plasticity.

Quenching of a Compound ring consisting of an inner high speed steel and an outer tool steel was simulated numerically using two codes, DistSIMR and Trast7. With the help of a database interface input data adjusted to the formats of the two codes were generated. The results of the simulations showed good agreement between the two models both for the computed residual stresses and distortions, which confirms the reliability of the results.
Microstructural investigation of the sheet metal DC05 for tailored blanking
Authors: Doege Eckart , Dohrmann Hinrich
Published: December 2016

Tailored blanks are being employed more and more in industrial deep drawing processes. For the layout of sheet metal part tooling it is important to predict the feasibility of the forming process. Substantial achievements have been made in this direction by means of the finite element method (FEM). Some basic requirements are correct descriptions of the material behaviour of the welded sheet metal in the base material as well as in the seam and the heat affected zone. It can be observed that the seam itself is considerably hardened. For the crack prediction during forming processes, the weld has to be considered in numerical simulation. Thus, investigations are performed to characterise the change of material properties in DC05 sheet metal. Dilatometric measurements as well as the grain size development are examined closer. It can be summarised that the resulting Widmanstätten structure is responsible for the hardness increase in the laser beam molten area, while the grain size has a greater influence in the heat affected zone.
Pearlite spheroidization by thermomechanical treatment of directly charged thin slabs
Authors: Bruns Hartmut , Kaspar Radko
Published: December 2016

Considering coarse initial austenite grain and the reduced thickness of directly charged thin slabs, a modified thermomechanical treatment was carried out on an unalloyed engineering steel with 0.66% C. For the laboratory simulation to determine the microstructural and mechanical properties a continuous casting simulator linked with the hot deformation simulator (Wumsi) were used. The aim of these tests was to study the process of the strain induced spheroidization of lamellar pearlite in order to improve the cold deformability of the steel, taking account of the particular conditions of direct charging. By the Variation of hot rolling deformation schedules, the influence of austenite grain size, pearlite interlamellar spacing as well as strain and strain temperature were investigated. The spheroidization process was mostly influenced by the strain applied just after finished pearlite transformation. Improving both strength and ductility by increasing fraction of spheroidized pearlite was supported by a smaller pearlite interlamellar spacing before deformation. A coarse austenite grain hardly affects the spheroidization process and brings about no impairment of mechanical properties, which makes this processing particularly attractive for direct charging of thin slabs. Moreover, a finely spheroidized pearlite exerts structural similarities to a tempered martensite, concerning distribution, shape and size of the cementite, accordingly leading to comparable mechanical properties. This justifies such modified hot rolling to be accepted as a potential substitution for the conventional post‐rolling quench and tempering of high carbon steel products.