Calculation of the isothermal transformation diagram from measurements with continuous cooling

For the general calculation of the transformation of steels the transformation diagram for isothermal transformation must be known. It is described, how from dilatometric measurements with continuous cooling the transformation at a constant temperature can be calculated. To do this, the simplex method must be used as iteration process to achieve sufficient precision. Even when measuring data are scattered around an ideal value by ±5% the transformation diagram for isothermal transformation can be calculated with considerable accuracy.     

Transformation characteristic of a Cr-Mn steel with austenite

The microstructures of three steels with about 0.35% C, 10% Mn and 13% Cr were investigated. After homogenization treatment, all steels have an austenitic microstructure with some carbide precipitates. During cooling to ?196°C as well as by plastic deformation ε-martensite and α-martensite are formed. The influence of the degree of deformation at different temperatures on microstructure and stability of austenite is described in detail. This information will be used to find a microstructure optimized to have a high cavitation resistance.     

To the reliability of x-ray texture measurements: Important parameters,measuring strategies,scatter bands and comparative measurements with different systems

The dependency of x-ray texture measurements from several important hardware parameters is shown. The consequences of different usual measuring strategies onto the resulting ODF are presented and the efficiency of the used correction method is investigated. A new 2-dimensional correction routine is developed as well as a new selfcorrection test for the quality judgement of the correction method. Scatter bands of one measurement, one goniometer system and in comparison of different goniometer systems are presented. Therefore comparative measurements of a textureless specimen and a specimen with a texture beneficial for deep drawing have been carried out at five different european laboratories. The results show, that some institutes work with correction methods that do not match to the used measuring strategy and that the comparison of measurements at different laboratories is very delicate due to the great differences in the determined textures.     

Measurement and calculation of residual stresses after die forging

For die forgings, fabricated from steels Ck 45, 42 CrMo 4 and 38 MnSiV S 6 3, TTT and CCT diagrams were determined, and after different heat treatments, measurements of mechanical properties, fatigue strength and residual stresses were carried out. The diameter of the specimens after the forging process was 32 and 45mm. The residual stresses after quenching between ?450 and +160N/mm² could be reduced to about 60N/mm² by tempering up to 620°C. The fatigue strength in the range of 300N/mm² depends more on the strength than on the residual stresses. Calculations with the program Antras-Thepla correlate well with the measured microstructures and residual stresses. This shows that the materials and processing data used for the calculation are conform to real processes.     

Einfluß von Restaustenit auf die Korngröße des Austenits nach der Reaustenitisierung von Stählen für schwere Schmiedestücke

Die Korngröße des Austenits nach der Reaustenitisierung von Stählen für schwere Schmiedestücke wurde in Abhängigkeit von der Art des Ausgangsgefüges, den Wiedererwärmungsbedingungen und den chemischen Zusammensetzungen untersucht. Besonders wurde der Einfluß von Restaustenit im Ausgangsgefüge auf die Korngröße des Austenits nach erneuter Austenitisierung betrachtet. Nach den Ergebnissen bleibt das Austenitkorn bei der Reaustenitisierung von Gefügen der Martensitstufe und der unteren Bainitstufe grob, wenn bei der Wiedererwärmung werkstoffabhängige Grenzerwärmungsgeschwindigkeiten unterschritten werden. Maßgeblich für eine mit zunehmender Erwärmungsgeschwindigkeit – in Abhängigkeit auch von den örtlichen chemischen Zusammensetzungen – mögliche Austenitkornverfeinerung ist das zeitabhängige Wachsen von Restaustenitfilmen zwischen den Kristalliten des Ausgangsgefüges in Konkurrenz zu den Anlaufzeiten für Keimbildung und -wachstum an den Grenzflächen Carbid/Ferrit. Ist wenig oder kein Restaustenit vorhanden, wie in einigen Gefügen der Bainit- bzw. der Perlitstufe, so entsteht der Austenit unabhängig von den Wiedererwärmungsbedingungen durch Neubildung und Wachsen von Austenitkeimen an den Grenzflächen Ferrit/Carbid. Unter den gegebenen Versuchsbedingungen entstand dabei immer ein feines Austenitkorn.     

Wirkung von Oberflächenschutzmaßnahmen auf hochwarmfeste Gasturbinenwerkstoffe. Teil II: Beeinflussung des Gefüges

Influence of Coating on the Properties of Heat Resistant Gas Turbine Alloys. Part 2. Microstructures Differences in the creep behaviour of some Ni base alloys were interpreted by a metallographic examination of broken specimens of a creep rupture test. If the fructure of uncoated specimens is intiated by an oxidation from the surface, by coating the time until rupture is elongated. If the fracture of uncoated specimens is unsensitive to an oxidation fro the surface, there is no influence of a coating except on melt of the alloy IN-792 coated with RT 22. Improvements or deteriorations in creep resistance of coated specimens compared with uncoated mainly are caused by the heat treatments during or after coating. Different casting techniques influence the orientation of dendrites and size, position and arrangement of pores wich partly have a decisive influence on the creep behaviour. Differences in creep limits up to a factor of 2 in time in general could not be interpreted by the metallographic observations used.     

An improved calculation of the transformation of steels

For the calculation of the transformation of steels during continuous cooling a new method is proposed. For isothermal transformation the temperature dependence of 1% and 99% transformation of austenite is described by a function which can well be fitted to measured values. This function allows an extrapolation beyond the measured values giving good agreement between calculated and measured TTT-diagrams. For continuous cooling it is possible to calculate the transformation below M_s. The agreement between calculated and measured values of the volume fractions of different microstructural constituents at room temperature after continuous cooling is good.     

Einfluß einiger Elemente auf die Kristallisation von Eisen bei der Erstarrung

Beobachtung des Ablaufs der dendritischen Kristallisation an Modellschmelzen aus Benzophenon und Wasser. Kristallseigerung als Indikator für die Kristallausbildung in Legierungen. Einfluß von Legierungselementen auf die Dendritenbildung in Eisenlegierungen.     

Entmischung der Legierungselemente bei der dendritischen Erstarrung von Eisenwerkstoffen

Zeilengefüge und die dendritische Mischkristallseigerung. Verfahren zur Messung der Entmischung von Legierungselementen. Zusammenhang zwischen Seigerungsverhältnis und Verteilungskoeffizient des Gleichgewichtsdiagramms eines Legierungselementes. Vorgänge bei der Entmischung der Legierungselemente.     

Towards a sustainable energy balance: progressive efficiency and the return of energy conservation

We argue that a primary focus on energy efficiency may not be sufficient to slow (and ultimately reverse) the growth in total energy consumption and carbon emissions. Instead, policy makers need to return to an earlier emphasis on “conservation,” with energy efficiency seen as a means rather than an end in itself. We briefly review the concept of “intensive” versus “extensive” variables (i.e., energy efficiency versus energy consumption) and why attention to both consumption and efficiency is essential for effective policy in a carbon- and oil-constrained world with increasingly brittle energy markets. To start, energy indicators and policy evaluation metrics need to reflect energy consumption, as well as efficiency. We introduce the concept of “progressive efficiency,” with the expected or required level of efficiency varying as a function of house size, appliance capacity, or more generally, the scale of energy services. We propose introducing progressive efficiency criteria first in consumer information programs (including appliance labeling categories) and then in voluntary rating and recognition programs such as ENERGY STAR. As acceptance grows, the concept could be extended to utility rebates, tax incentives, and ultimately to mandatory codes and standards. For these and other programs, incorporating criteria for consumption, as well as efficiency, offers a path for energy experts, policymakers, and the public to begin building consensus on energy policies that recognize the limits of resources and global carrying capacity. Ultimately, it is both necessary and, we believe, possible to manage energy consumption, not just efficiency, in order to achieve a sustainable energy balance. Along the way, we may find it possible to shift expectations away from perpetual growth and toward satisfaction with sufficiency.