Abstract Due to the increased use of high strength steels in safety-critical components, the addition of fracture mechanics analyses to the classical stress-based design has gained remarkable importance. Therefore, static and cyclic fracture mechanical properties of high strength steels were determined in addition to the mechanical-technological properties. The following three topics were considered in this work: • Influence of temperature on the mechanical properties of a thermomechanically rolled and accelerated cooled (TMCP) base material. • Comparison of the properties of the heat-affected zones of a TMCP and a quenched and tempered (QT) base material of 620 MPa strength class. • Comparison of a metal active gas (MAG) and submerged-arc (SAW) welding in welded and post welded heat treatment condition. The temperature dependence was determined by impact tests and fracture mechanics tests (KJc-values) on compact tension (CT) and single edge notch bending (SENB) specimens. From the results of the Charpy impact tests, a master curve was determined using the method described in FITNET. The determination of the master curve of the fracture toughness was performed according to ASTM E1921. The comparison of the master curves determined from the impact energy and fracture mechanics tests showed a very good agreement between these two methods of characterization. Furthermore, the cleavage fracture stress was determined for the TMCP material by combining FE-calculation with the experimental results. The comparison between a TMCP- and a QT base material shows that in the heat affected zone the TMCP material has significantly better fracture properties. The hardness measurements and tensile tests at the QT material showed a clear increase in hardness and strength in the fine grain and coarse grain zone. However, the TMCP-base material shows no significant hardening because of its low carbon content. The investigated submerged-arc welding has tendentially led to higher strength values than the MAG welding, at the same time the strains to fracture in the submerged-arc welding were slightly lower. In the static as well as in the cyclic fracture mechanics tests the MAG welds showed a higher crack resistance. The post weld heat treatment resulted in a homogenization of the mechanical properties. In the submerged-arc welding a wider heat affected zone and a lager grain size in the coarse grain zone were found.