The conditions for ferrite and pearlite banding in strip and plate made of structural steels were investigated. Factors found to influence the formation of banded structures were the cooling rate during the γ/α‐transformation, the former austenite grain size, and the work‐hardened condition of the former austenite. Analyses with the aid of an electron beam microprobe made it possible to demonstrate that the carbon‐rich bands correspond locally with banded manganese enrichments, yet that they do not form before the course of the γ/α‐transformation as a result of secondary segregation. It was possible to explain the mechanism of action of the influencing factors on the basis of this model.

No abstract

Steel sheets frequently exhibit pronounced textures influencing the product properties by causing anisotropies. In the present paper a survey is given of the typical textures in steel sheets in the final and also in the intermediate stages of the manufacturing process. In order to quantify and characterize textures the method of ODF is used, which also allows a simple representation of the main texture features by plotting the pole density along texture fibres. For hot‐rolled strip the textures of mild unalloyed and high‐strength microalloyed steels are considered for different finish‐rolling temperatures including rolling in the γ/α dual phase region. Besides the textures in the middle‐section the surface textures are also dealt with. The cold‐rolling texture is investigated with regard to the influence of hot‐band texture and grain size for unalloyed mild deep‐drawing grades and IF‐steels. The recrystallization texture of different deep‐drawing qualities is presented together with results of the influence of N‐fixation on the texture determined r‐values.

Die Aufnahme von Wasserstoff aus Medien kann bei Stiihen mit ferritischen Gefiigeanteilen zu Schiidigungen fiihren. Die Wechselwirkung von absorbiertem Wasserstoff und Stahl wird einerseits durch die Wasserstoffaktivitiit, andererseits durch belastungs-und gefiigeabhiingige Grenzwerte bestimmt. Die Arten wasserstotkduzierter Korrosion werden anhand von Versuchen mit niedriglegierten Stahlen dargestellt. Oberfliichenblasen und Innenrisse konnen ohne Einwirkung tiuSerer Belastungen auftreten. Bei wasserstoffinduzierter Spannungsdkorrosion werden Korrosionssysteme, bei denen ruhende Belastung bereits unerwiinschte Wirkungen zeigt, von solchen Systemen unterschieden, bei denen die Spannungsdkorrosion an Dehnraten innerhalb eines kritischen Geschwindigkeitsbereiches gebunden ist.The absorption of hydrogen from media can lead to cracking in steels with a ferritic structure. The interaction of absorbed hydrogen and steel is governed by the hydrogen activity and by stress-and structure-dependent threshold values. Different types of hydrogeninduced corrosion are illustrated by means of tests performed on lowalloy structural steels. Surface blistering and internal cracking can occur on the one hand without external stresses. In the case of hydrogen-induced stress corrosion cracking on the other hand a differentiation is made between corrosion systems in which constant loading displays already cracking and systems in which the cracking is tied to slow strain rates within a critical range.

The existing texture measuring device of the research department of Thyssen Stahl AG has been retrofitted and automated to make it possible that ODF analyses may be used more comprehensively in steel development, despite the high efforts required for measuring and evaluation. Now it is possible to automatically measure series of up to 10 samples. All measuring processes are controlled by step motors by a computer, which also collects the measured data. Samples are changed by a robot arm, which replaces the measured sample by a new one taken from a special sample magazine. Both the evaluation and the output of data and graphics are also performed by series and automatically on a second computer. Because of the new investigation device, up to 12 ODF measurements per day are possible, while the costs are reduced to one fifth of the former level. MeBsystem fUr Texturen mit vollautcmatlschem Probenwechsel mit Hille eines Roboterarmes. Die bei der Thyssen Forschung vorhandene TexturmeBeinrichtung wurde umgebaut und automatisiert. Jetzt k6nnen OVF-Analysen in der Stahlentwicklungtrotz des hohen Aufwands, der zur Messung und Auswertung erforderlich ist -besser verwendet werden. Reihen von bis zu 10 Proben k6nnen nun automatisch gemessen werden. Aile MeBverfahren erfolgen computergesteuert; MeBdaten werden im Rechner gesammelt. Die Proben werden von einem Roboterarm ausgewechselt. Auswertung und Datenausgabe -auch in Form von Graphiken -erfolgen ebenfalls serienrnafiiq und automatisch auf einem zweiten Rechner. Mit dieser neuen Untersuchungseinrichtung k6nnen bis zu 12 OVF-Messungen pro Tag durchgefUhrt werden. Die Kosten wurden im Vergleich zurn truheren Verfahren auf ein Funttel gesenkt.