Comprehensive development work on martensitic steels belonging to the so‐called 12% Cr steel group were performed at the Institute for Materials Research (IMF) of Forschungszentrum Karlsruhe on martensitic steels, the so‐called 12% Cr steel group, in order to meet the various requirements in nuclear and conventional energy technology. The transformation characteristics of 29 different grades of steel and 38 heats have been determined and continuous cooling transformation (CCT) diagrams have been prepared. The diagrams are first described by groups of subjects in a chronological order because the change in the chemical composition cannot be correlated in all cases with the change in transformation behaviour. The quenching hardness can be satisfactorily described as a function of the C+N content if, taking into account the Nb, Zr, Ta, Hf fractions, a common effectiveness factor is calculated. This effectiveness factor is also integrated in the calculation of the Ms point by modifying accordingly the equation proposed by Steven and Haynes for low‐alloy steels and supplemented by the summands for V and W. An equation is introduced for the calculation of the critical cooling rate for pearlite transformation which takes into account the special influence exerted by elements Cr, V, Mo, W, Ge. The comparison between calculated and measured values for Ms and Vcrit is satisfactory, except for some steels.

Carbide segregations in tool steels containing about 1% C. On hypereutectoid tools steels containing about 1.0% C and up to6.0% Cr, 1.0% Mo, 0.5% V and 3.3% W theauthors studied the formation of "quasi-ledeburitic" carbides during the solidification of the residual melt. Effect of the chemical composition and solidification rate on the proportion of surface, arrangement and configuration as uell. as number of the carbides and the'ir cristallographic structure. Elimination of the carbides by solution heat treatment. Discussion, on the background of the experimental results, of the oriqim and size of carbide segregations. Segregations de carbnres dans les aciers it ontil avec environ 1% C. Etude de la formation de carbures «quasiledeburitiques» lors de la solidification de la coulee nfsiduelle d'aciers a outilhypereutectoides, tenant environ1,(J% C et jusqu'a 6,0% Cr, 1,0% JIo, 0,5% Vet 3,3% W. Influence de la composition chimique et de la vitesse de solidification sur la quote-part de surface, l'arrangement, la configuration et le nombre des carbures et leurstructure cristallographique. Elimina#on des carbures par un recuit de mise en solution. Discussion, a la base des resuliais d'essai, de la naissance et de la grosseur des segregations de carbures.

An dem Warmarbeitsstahl X 30 WCrV 5 3 mit rd. 0,3% C, 4,3% W, 2,4% Cr und 0,6% V durch Untersuchung des Umwandlungsverhaltens, besonders in der Zwischenstufe, und durch Warmzugversuche Prüfung der Möglichkeit, durch legierungstechnische Maßnahmen (Änderung des Gehaltes an Kohlenstoff, Silizium, Chrom und Vanadin sowie Zusätze an Zirkon) die Bildung von Zwischenstufe und damit die Neigung zu Warmversprödung zu verhindern.

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Einteilung der isothermischen ZTU‐Schaubilder von Stählen nach ihrer durch die relative Temperaturlage von Perlit‐ und Zwischenstufe bzw. von Zwischenstufe und Ms‐Temperatur bestimmten Form. Ableitung dieser Formen aus dem Kohlenstoffgehalt und einem zusammenfassenden Wirkwert für die Legierungselemente. Vergleich experimentell ermittelter ZTU‐Schaubilder mit den auf diese Weise festgelegten Umwandlungsschaubildern.