Long bar products with an ultrafine-grained steel microstructure are essential to extend the lifetime of dynamically loaded components and to develop promising innovative products for new markets, including low-temperature applications. Grain sizes of less than 5 µm can be produced by an innovative thermomechanical processing with a high reduction ratio in one single step. The result is an ultrafine special steel that exhibits the normally opposed properties of high strength and excellent toughness. The technology can be applied to many standard grades of steel e.g. carbon steel C35. The thermomechanical processed C35 with ultrafine-grained microstructure was characterised regarding its mechanical-technological properties. Of special interest was the effect of the grain size on the notch impact energy and the fatigue resistance. A beneficial feature is that the modified steel grades exhibit notch impact energy values considerably greater than 27 joules even at temperatures as low as -60ºC.