The Barkhausen noise technique (BHN) has been used as a non destructive tool for the measurement of the hardness in various types of steel, namely low carbon steel, TRIP steel, Duplex steel and welding in low carbon steel. The steel samples have undergone different mechanical treatment, such as plastic deformation, cold rolling or welding. Hardness and microhardness have been determined in terms of Vickers standards. A remarkably linear dependence of the BHN on the Vickers hardness of the corresponding samples with an uncertainty in the order of 3-5% has been achieved, illustrating that the BHN may be used as a non destructive tool for determining the Vickers hardness in steels. Furthermore, BHN measurements have obtained on the welding area, along the thermally affected zone and the weld itself, illustrating the theoretically expected stress field distribution.