The influence of a low Ti addition (∼0·01%) on the hot ductility of Nb containing HSLA steels has been examined. For conventional cooling conditions in which an average cooling rate from the melting point to the test temperature was used, the ductility decreased markedly with the addition of Ti. However, when cooling conditions after melting were more in accord with the thermal heat treatment undergone by the strand during continuous casting, i.e. cooling is fast to begin with, reaches a minimum and then reheats, after which the temperature falls more slowly to the test temperature, the Ti addition was found to be beneficial.

The precipitation of niobium carbo-nitrides in the austenite phase, interphase and ferrite phase of microalloyed steel was assessed by a criticalliterature review and a round table discussion. This work analyses the contribution of niobium carbide precipitates formed in ferrite in the precipitation hardening of commercially hot rolled strip. Thermodynamics and kinetics of niobium carbo-nitride precipitation as well as the effect of deformation and temperature on the precipitation kinetics are discussed in various examples to determine the amount of niobium in solid solution that will be available for precipitation hardening after thermomechanical rolling in the austenite phase and successive phase transformation.

The precipitation of titanium nitride in undeformed solid carbon-manganese steel has been investigated by means of metallography and electron microscopy at in-situ melted samples the cooling of which was interrupted at different temperatures for a defined time. The deformation-induced precipitation of titanium nitride was studied on samples which were in-situ melted in a torsion plastometer, deformed after solidification, re-deformed after a holding time, and quenched. Additionally, 50 mm slabs were investigated after direct rolling in a pilot plant, partially with a preceding soaking. In the range of delta ferrite fast homogenization of segregated titanium takes place. No TiN nuclei were formed. In undeformed austenite some large precipitates were formed indicating the solidification structure. In the 1200 to 1100 "C range particle sizes between 20 and 70 nm were reached. A high density of deformation-induced particles smaller than 10 nm could be obtained at or below 1050 "C. The density of the particles increased with decreasing deformation temperature. After fast cooling, below 1000 "C also in undeformed material finely dispersed precipitates were formed.Ausscheidung von Titannitrid in niedriglegiertem Stahl wiihrend des AbkOhlens und Umformens. Die Bildung von Titannitrid in unverformtem festem Kohlenstoff-Mangan-Stahl wurde metallographisch und elektronenoptisch an Proben, deren AbkOhlung nach dem Erstarren bei unterschiedlichen Temperaturen fOr vorgegebene Zeiten unterbrochen wurde, untersucht. Eine verformungsinduzierte Ausscheidung von Titannitrid erfolgte an Proben, die in einem Torsionsplastometer in-situ geschmolzen, nach dem Erstarren umgeformt, nach einer Haltezeit nochmals verformt und abgeschreckt wurden. Zusatzllch wurden 50-mm-Platinen nach Direktwalzen in einer Versuchsanlage untersucht, teilweise mit AusgleichsglOhung vor dem Walzen.

On the technical background of elevated coiling temperatures the influence of the precipitated volume fraction and of the dispersion rate of grain boundary cementite on cold‐rolling textures in low carbon steel was investigated. Whilst different dispersion rates with constant cementite volume do not reveal any distinct influence, the rolling texture is lowered by increasing the precipitated volume fraction of cementite.

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