bluuebunny/crossref_metadata_2025_split huggingface dataset:
Legierungsentwicklung zur Verschleißreduzierung von Schmiedegesenken – Einfluss von Mangan auf die Absenkung der Ac1b-Temperatur
Authors: Pfahl A. , Puchert A. , Behrens B.-A. , Bach F.-W. 
Published: December 2013

Abstract

For a long time the research and development of tools and tool systems for forging applications play an important role in the field of production technologies. Due to the fact that wear processes are the most common cause for the failure of forging dies, the main goal of the presented work is to achieve a wear reduction and thereby an enhanced durability of these dies by a new alloy concept. Attention was paid to the influence of an increased manganese content on the reduction of the eutectoid-temperature (Ac1b-temperature). In this way, it was possible to take a positive influence on the changes in the microstructure of the edge layer caused by the cyclic heating and cooling during forging. Especially the range of the white layer is enlarged and the influence of the lower layers consisting of cyclic soft-annealed steel is reduced, compared to the standard alloys. This article shows the results for up to 300 forging cycles.
Prozessmöglichkeiten zur gezielten Einstellung des Gasabschreckens*
Authors: Schmidt R. R. , Fritsching U. , Lübben Th. 
Published: December 2013

Kurzfassung

Das Abschrecken von Bauteilen mit Gasen hat gegenüber der Abschreckung in flüssigen Medien wesentliche Vorteile, wie z.B. ein reduziertes Sicherheitsrisiko, eine höhere Umweltverträglichkeit, die Möglichkeit einer direkten Beeinflussung des Härteergebnisses und einen stabileren Abkühlverlauf, was insgesamt zu einem sichereren und einem besser beherrschbaren Abschreckprozess führt.
In diesem Beitrag werden prozesstechnische Varianten des Gasabschreckprozesses vorgestellt, um gezielt das Ergebnis der Hochdruckgasabschreckung beeinflussen zu können. Zum einen werden strömungsbeeinflussende Einbauten in der Abschreckvorrichtung diskutiert, die die Möglichkeit bieten, lokal an den abzuschreckenden Bauteilen den Wärmeübergang zu steuern. Zum anderen wird eine Methode präsentiert, um werkstoffabhängige Abschreckergebnisse beim Hochdruckgasabschrecken vorherzusagen, um so den Abschreckprozess gezielt an die jeweilige Werkstoffzusammensetzung anpassen zu können. Hierbei wird auf wiederholte Abkühlmessungen in den Anlagen und chemische Analysen des verwendeten Stahls verzichtet. Mit Hilfe von zu ermittelnden Korrelationsdiagrammen können geeignete Prozessparameter, insbesondere die Gasart, der Systemdruck und der Volumenstrom, anhand der Härteforderungen gezielt angepasst und eingestellt werden. Auf diese Weise wird die Energieeffizienz des Gasabschreckprozesses weiter erhöht.
Korrosionsbeständige Metall-Matrix-Composite
Authors: Siebert S. , Theisen W. , Hill H. 
Published: December 2013

Kurzfassung

Metall-Matrix-Composite (MMC) auf Eisenbasis verlangen nach speziellen Legierungskonzepten, um eine ausreichende Korrosionsbeständigkeit zu erhalten. MMC auf Nickel- oder Cobaltbasis hingegen besitzen von Hause aus eine gute Beständigkeit gegen Korrosion. Als Nachteil dieser MMC steht dem gegenüber, dass die Festigkeit der Metallmatrix allein durch die Mischkristallbildung begrenzt gesteigert werden kann. Deutlich höher fällt die Festigkeitssteigerung bei einer martensitischen Härtung aus, die in Eisenbasismatrixlegierungen genutzt werden kann.
Die unterschiedlichen Legierungskonzepte zur Verbesserung des Korrosionswiderstandes von MMC auf Eisenbasis sowie deren Wirksamkeit und Grenzen sollen in dieser Veröffentlichung erläutert werden. Dabei liegt ein Augenmerk auf der Auswahl der Hartphasen, deren Aufgabe im Wesentlichen darin besteht, den Verschleißwiderstand anzuheben, jedoch darf ihr Einfluss auf die ablaufenden Korrosionsvorgänge nicht unberücksichtigt bleiben.
Influence of the chemical potential of carbon on the microstructural and compositional evolution of the compound layer developing upon nitrocarburizing of α-iron*
Authors: Woehrle T. , Leineweber A. , Mittemeijer E. J. 
Published: December 2013

Abstract

Controlled nitrocarburizing experiments were performed at 823 K and 853 K in order to systematically investigate the influence of the chemical potentials of carbon and nitrogen imposed by NH3/H2/CO/CO2/H2O-containing gas mixtures on the microstructural and compositional evolution of the compound layer formed on pure α-Fe substrates. The morphological evolution of the compound layer was investigated by optical microscopy. The nitrogen and carbon concentration-depth profiles in the layer were determined by electron-probe microanalysis (EPMA). Layer-growth kinetics was analysed on the basis of compound layer-thickness measurements. For a fixed chemical potential of nitrogen it was found that the microstructure and the layer-growth kinetics are strongly dependent on the chemical potential of carbon.
Nitriding response of ferritic Fe-Ti-Cr alloys*
Authors: Jung K. S. , Schacherl R. E. , Bischoff E. , Mittemeijer E. J. 
Published: December 2013

Abstract

Specimens of ferritic iron-based Fe-Ti-Cr alloys, containing a total of 0.30 at.% alloying elements, Ti and Cr with varying Ti/Cr atomic ratio (0.45, 0.87 and 1.90), were nitrided in a NH3/H2 gas atmosphere at 580 °C. The microstructure of the nitrided zone was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Nitride platelets (length ≤ 30 nm and thickness ≤ 1 nm) developed in the nitrided zone. Particularly clear for the larger Ti/Cr atomic ratios, a tetragonally distorted ferrite develops next to the cubic ferrite, as evidenced both by XRD and TEM. The absence of separate TiN and CrN diffraction spots in the selected area electron diffraction patterns suggests the development of mixed TixCr1-xN nitride precipitates. The mixed TixCr1-xN nitride precipitates are of rock-salt crystal structure type and obey a Bain orientation relationship with the ferrite matrix.
Ermüdungsfestigkeit hochlegierter Werkzeugstähle
Authors: Jung I. 
Published: December 2013

Kurzfassung

Die meisten Werkzeuge unterliegen im Einsatz einer komplexen mechanischen Beanspruchung, wie z. B. Schneidstempel, die häufig einer zyklischen schwellenden Zug-,Druck- und Biegebeanspruchung ausgesetzt sind. Da in den letzten Jahren der Wettbewerbsdruck durch zunehmende Billigproduktionen in Niedriglohnländern steigt, ist sowohl im Werkzeugbau als auch in der in Deutschland verbleibenden Produktion ein zunehmender Trend zu qualitativ hochwertigen Werkzeugen mit möglichst langer Lebensdauer und entsprechend hoher Anzahl an Arbeitszyklen zu verzeichnen. Damit gewinnt die Ermüdungs- bzw. Dauerfestigkeit von Werkzeugstählen zunehmend an Bedeutung. Dies gilt vor allem für hochlegierte Werkzeugstähle, die in der Regel mit einer hohen Härte eingesetzt werden und bei denen für eine optimale Leistung ein Kompromiss zwischen Festigkeit und Zähigkeit getroffen werden muss, der auch weitgehend Einfluss auf die Ermüdungsfestigkeit nimmt.
Im Folgenden wird daher ein Überblick über die Ermüdungsfestigkeit hochlegierter Werkzeugstähle gegeben. Daneben werden Methoden vorgestellt, die Ermüdungsfestigkeit positiv zu beeinflussen. Neben geeigneten konstruktiven Maßnahmen, wie z. B. das Anbringen möglichst großer Radien und möglichst fehlerfreier Oberflächen zur Verringerung der Kerbwirkung, kommen Maßnahmen zur Erhöhung der Homogenität und des Reinheitsgrades bei der Erschmelzung der Stähle wie ESU (Elektroschlackeumschmelz)-Verfahren oder PM (pulvermetallurgische) Fertigung zum Einsatz.
Study on nitrogen in martensitic stainless steels
Authors: Krasokha N. , Berns H. 
Published: December 2013

Abstract

Pressure metallurgy is a means of increasing the nitrogen content and thereby the resistance of stainless martensitic steels to pitting corrosion. The present study on their constitution and heat treatment reveals that even at normal pressure more nitrogen is dissolved in the melt if the carbon content increases, because the fraction of ferrite is reduced during solidification. Nitrogen is dissolved more readily during austenitisation than carbon which lowers the C/N ratio at hardening temperature and thus is likely to improve the corrosion resistance of martensite after quenching. As the stability of retained austenite is increased by nitrogen a strain induced transformation by ausforming is discussed.
Increase of fatigue strength and lifetime by deep rolling at elevated temperature of notched specimens made of steel SAE 4140
Authors: Cherif A. , Hochbein H. , Zinn W. , Scholtes B. 
Published: December 2013

Abstract

In comparison with traditional room temperature processes, deep rolling at elevated temperature leads to further increased fatigue strengths and lifetimes. This is demonstrated using notched bending fatigue samples made of quenched and tempered steel SAE 4140, which have been processed at room temperature and at 300 °C resp. near surface properties were analyzed before and after fatigue loading. It is shown that the positive effect of warm deep rolling is due to stabilized residual stress states which relax only slightly in the course of fatigue loading. The underlying microstructural processes are static as well as dynamic strain aging effects.
Tool thermal conditions for tailored material properties
Authors: Oldenburg M. , Lindkvist G. 
Published: December 2013

Abstract

With the press hardening technology it is possible to produce components with tailor- made material properties. The present work is based on a comprehensive thermo-mechanical material model for simulation of press hardening and similar processes. The model accounts for and predicts time dependent and time-independent phase transformations, mechanical and thermal properties as well as transformation plasticity during the complete cooling and deformation process from 900 °C to room temperature. The model predicts the microstructure evolution during the complete process as well as the final fractions. The thermal contact properties and the thermal properties in the tools have influence on the final material state. Solutions for tool heating and cooling for manufacturing of components with soft zones are studied. Based on the results from the press hardening simulations, thermal properties of special tool materials are taken into account in order to optimise the manufacturing thermal cycle.
Cold treatment of tool steels
Authors: Stratton P. 
Published: December 2013

Abstract

It has been suggested that when tool steels are exposed to temperatures around the boiling point of liquid nitrogen (−196°C) for extended periods some properties of the steel, particularly wear, are improved. Dissenters claim that the improvements are due to statistical variation and cannot be reproduced consistently. The most commonly reported experimental results are for AISI D2 and AISI M2. This review examines the available evidence and suggests a way forward for the debate. It has also been suggested that the colder the sub-zero treatment temperature after quenching, the greater the amount of the retained austenite that existed at room temperature that is converted to martensite. The implication being that the true martensite finish temperature (Mf) is almost always close to or below absolute zero. Others suggest that Mf is in the range −80 °C to −120 °C for most steels. Some of the available evidence is reviewed particularly with respect to AISI D2 and AISI M2 and the conclusion drawn that transformation continues until all the austenite is eliminated or absolute zero is reached.
Hot friction and wear behaviour of plasma nitrided and low pressure carburized hot work tool steel sliding against 6082 Al alloy
Authors: Pellizzari M. , Siller I. 
Published: December 2013

Abstract

High temperature friction and wear behaviour of a hot work tool steel sliding against AA6082 alloy were investigated by means of a customary test configuration, which provides the conformal contact between a die block and an AA-disc. Uninterrupted tests in air were carried out. The friction behaviour is characterized by limited fluctuations just after the beginning of test, finally evidencing a transition to a more unstable contact regime after progressive transfer of Al to the die surface. The tendency towards Al pick up was evaluated by measuring the mass increase of die samples and their capability in delaying the formation of hard Al oxide particles, which are very detrimental for the surface finishing of the extrudate. The efficacy of different surface treatments, i.e. plasma nitriding and low pressure carburizing, was studied. Furthermore, samples with different level of roughness, corresponding to conventional machining (0.7–0.8 μm) and mirror polishing (0.02 μm), respectively, were produced. Finally the influence of hardness was also evaluated by considering two different hardness of the base steel (56 HRC and 44 HRC). In general, surface hardening improves the load bearing capability of the die surface, causing an extended permanence in the stable friction regime. Plasma nitrided samples (1125 HV 0.1) evidenced a better behavior than case hardened (670 HV 0.1) and base steel (56 HRC, 620 HV 0.1), respectively. Overtempered samples (44 HRC, 500 HV 0.1) confirm this trend. In view of the experimental error, a lower surface roughness did not improve the tribological properties.
Effect of the heating rate in the tempering of DIN 100 V1
Authors: Cajner F. , Landek D. , Rafel H. , Kovačić S. 
Published: December 2013

Abstract

In this paper, the effect of the heating rate on the process of tempering and the obtained hardness of the DIN 100 V1 (AISI W2) carbon tool steel has been investigated and determined. Steel specimens in two initial states were investigated: after quenching and after quenching and deep-cryogenic cooling. The specimens were submitted to tempering in a dilatometer, varying the heating rates, temperature of tempering between 200°C and 690°C and duration of keeping the specimens at that temperature. A common effect of these factors on the temperature of the start of particular stages in tempering and the obtained properties was determined using dilatometry. Differential dilatation analysis was carried out, together with hardness tests and XRD (X-ray diffraction) analysis.
Straightening of induction hardened shafts – influence on fatigue strength and residual stress
Authors: Fahlkrans J. , Melander A. , Gårdstam J. , Haglund S. 
Published: December 2013

Abstract

Straightening of distorted components after heat treatment is often a necessary operation. The straightening operation leads to local plastic deformation, which is affecting the residual stress state, the hardness, and ultimately the fatigue strength of the component. The present study evaluates the influence of a straightening operation on fatigue strength and on the residual stress state of induction hardened shafts of steel EN 42CrMo4. A simplified FEM model was formulated. The model showed that the residual stress state was asymmetric along the circumference of a straightened shaft. Fatigue testing was performed in a three point bending and showed that the fatigue strength was reduced by up to some 20 % by heavy straightening. A fracture mechanics model for fatigue crack growth and arrest was developed. The model could be used to predict the fatigue strength of a straightened shaft provided that the residual stress state was known.
Systematische Untersuchung verschiedener Einflussgrößen auf die Maß- und Formänderungen von einsatzgehärteten Stirnrädern
Authors: Steinbacher M. , Surm H. , Clausen B. , Lübben Th. , Hoffmann F. 
Published: December 2013

Abstract

Typically, highly stressed gears are heat treated to satisfy operational demands. Case hardening is a common heat treatment associated with power train components. In the heat treatment process complex distortion takes place, which has been studied in these examinations. Object of the actual investigations were spur wheels with small module. The case hardening was realized utilizing low pressure carburization with subsequent high pressure gas quenching in a heat treatment furnace of industrial proportion. The systematic analysis was guided using design of experiment methods. In strategic focus were the three contributing heat treatment steps heating, carburization and quenching. Heating related factors were the batch design and the preheating temperature. During carburization the temperature, carburization depth and surface carbon content were altered. Finally no quenching related variations were performed. The influences of the different parameters on the size and shape changes of the gear wheels were evaluated statistically. The identified main factors on size as well as on shape changes of the base body and the toothing will be presented and discussed.
Entwicklung eines Al-reduzierten Einsatzstahls für die Hochtemperatur-Aufkohlung∗
Authors: Konovalov S. , Prahl U. , Kohlmann R. , Bleck W. 
Published: December 2013

Kurzfassung
Diese Arbeit zielt auf eine Verbesserung des oxidischen Reinheitsgrades in einem Einsatzstahl durch eine Reduktion des Aluminiumgehalts. Auf Basis des mikrolegierten Stahls 25MoCr4 wird ein neues Legierungskonzept vorgestellt, bei dem die Feinkornbeständigkeit auch für eine Hochtemperatur-Aufkohlung bei 1050 °C und höher mittels eines angepassten Niobgehalts sichergestellt werden kann. Das hier vorgestellte Legierungskonzept ist eine Weiterentwicklung von früheren Untersuchungen aus dem Jahr 2002, bei denen die Feinkornbeständigkeit gegenüber Hochtemperatur-Aufkohlung für eine aluminiumreduzierte Variante noch nicht ausreichend war. Das neue Konzept verwendet moderne thermodynamische Simulationsmethoden, um den korrekten Niobgehalt zur Substitution von Aluminium und Titan vorherzusagen. Die experimentelle Validierung des Konzepts erfolgte anhand einer Laborschmelze gegenüber einem Referenzwerkstoff und untersucht Reinheitsgrad und Feinkornbeständigkeit bei Hochtemperatur-Aufkohlung für industrienahe Prozessketten der Großgetriebeherstellung
In-situ sampling method (HSSE-TDS-GC-MS) during MVOC (microbial volatile organic compounds) measurements of metalworking fluids (MWF)
Authors: Weinhold M. X. , Siol A. , Koch T. , Grafe H. , Rabenstein A. , Thöming J. 
Published: December 2013

Abstract

Metalworking fluids (MWF) are used routinely throughout the world as cooling and lubricating agent for metal-cutting processes. They are important components to maintain the quality and precision of the metal-cutting but are slowly consumed within this process. Hence, monitoring of ageing of the MWFs before depletion is important for economical, ecological and security reasons. A method is presented, which enables to estimate the ageing of tools by measuring the microbial volatile outcome (MVOC) of the MWF. Measurements are done by headspace sorptive extraction combined to thermal desorption in a gas chromatography setup with mass selective detector (HSSE-TDS-GCMS). It could be shown that ageing of tools correlates to emission of ketonic and alcoholic MVOCs (namely 2-Heptanone, 2-Octanone, 1-Octanol, 2-Nonanone and 2-Decanone). Analysis of these components can be used as “ageing marker” for the investigated MWF solutions. The obtained information can further be used to calibrate electronic nose sensors for high-throughput and rapid analysis in future projects. Hence, it can be concluded that headspace analysis of volatile microbial metabolites by HSSE in combination with TDS-GC-MS is a suitable monitoring technique for the ageing of metalworking fluids.
Distortion of steel flat ring products during the production cycle∗
Authors: Česnik D. , Bratuš V. , Bizjak M. 
Published: December 2013

Abstract

The distortion of steel flat ring type products after fine-blanking and subsequent carbonitriding was investigated. All the analyzed products were produced from the same coil and under the same conditions of fine-blanking. The fine blanked products were afterwards heat treated by using three different procedures – carbonitriting, stress relief annealing and heat treatment in a neutral atmosphere under the same temperature regime as for carbonitriding. The contribution of fine-blanking, relief of residual stresses, uneven heating and cooling and the formation of carbonitrided cases on the overall distortion were determined. The results were complemented with hardness measurements, residual stresses measurements and observations of microstructure. The presented research work is the first step towards the understanding of the mechanisms and factors that influence the quality of the final products during the production cycle.
The Ideal Quenching Medium? – Characterisation of Ionic Liquids for Heat Treatment of Metallic Components
Authors: Beck M. , Schmidt C. , Ahrenberg M. , Schick C. , Kragl U. , Keßler O. 
Published: December 2013

Abstract

Quenching as a part of heat treatment is an important process in the manufacturing chain of metallic components. One of the most common processes is immersion quenching in vaporising liquids. Unfortunately, this process is affected by the Leidenfrost-phenomenon. This effect can generate inhomogeneous quenching and thus asymmetrical residual stresses and avoidable distortion. In this work, ionic liquids have been investigated as new quenching media, which can be used as baths near room temperature. Aluminium cylinders have been quenched in baths of different ionic liquids with varying water contents and bath temperatures. The time-temperature curves have been recorded and the heat transfer coefficients were determined and compared to quenching in water. Addition of a few percents water to the ionic liquids increases the cooling rate significantly. Even at higher water contents, bubble boiling and convection are predominant and almost no Leidenfrost-effect occurs. This offers a huge potential to accelerate and homogenise immersion quenching.