Abstract: "Thermomechanically cold processed (TMCP) steels with a high level of strength are actively used in various constructions. The high strength of the TMCP steels is acquired due to the formation of the fine-grained structure. Such steels have relatively low carbon percentage. These greatly simplify the solution of the problem of improving the quality and reliability of metal structures. At the same time this raises new questions in terms of the technology for welding such steels. In the first instance, it is conditioned by the complex behavior of the TMCP structure under the welding thermal cycle effect. The most important property of the welded joint is yield stress (YS) which characterizes the workability of the whole joint. The estimation of the YS while developing the welding technology is a valuable task for design. This current research has made a complex investigation of the modern welding technique's effect on the behavior of the yield stress formation in TMCP steel welded joints. For progressive technology development, pulse arc welding was used."
Abstract: "Reducing the weight of car components has led to more filigree parts over the last decade and the use of stronger materials. Conventional solutions with quenched and tempered steels not always fulfil the demands concerning technical reliability, economics and environmental friendliness. Thermomechanically processed and continuously cooled bainitic steels are clearly better for demanding applications balancing these material's aspects which has led to a successful introduction of new steel grades into car components during the last decade. However, bainitic steels often do not reach the high Charpy impact toughness values of quenched and tempered steels. This is in particular true at sub-zero temperatures and after thermal or thermo-chemical treatments. Applying innovative technologies, the above mentioned handicap of bainitic steels can be reduced or completely eliminated by refinement of the prior austenite grain sizes (not only in flat products but also in long products). In the present work the industrial production technology "XTP" was applied to produce fine-grained low carbon bainitic-martensitic steel bars. In comparison with conventionally hot rolled bars the Charpy transition temperature then was decreased by ~60°C. The influence of a tempering treatment on mechanical characteristics was investigated in detail and will be discussed. Results demonstrate significant improvements in comparison with conventionally produced bars. The unique property combinations found in these new products open new perspectives for them in challenging applications."
"Test method for the determination of flow curves and benchmark characteristic values for tensile testing by means of minor destructive indentation, 3D measurement and finite-element material models"