The effects of welding heat input on the usability of high strength steels in welded structures

摘要

High strength steel (HSS) has been in use in workshops since the 1980s. Atthat time, the significance of the term HSS differed from the modern conceptionas the maximum yield strength of HSSs has increased nearly every year. Thereare three different ways to make HSS. The first and oldest method is QT(quenched and tempered) followed by the TMCP (thermomechanical controlledprocess) and DQ (direct quenching) methods.This thesis consists of two parts, the first of which part introduces the researchtopic and discusses welded HSS structures by characterizing the mostimportant variables. In the second part of the thesis, the usability of welded HSSstructures is examined through a set of laboratory tests.The results of this study explain the differences in the usability of the weldedHSSs made by the three different methods. The results additionally indicate thatusage of different HSSs in the welded structures presumes that manufacturersknow what kind of HSS they are welding. As manufacturers use greaterstrength HSSs in welded structures, the demands for welding rise as well. Therefore, during the manufacturing process, factors such as heat input, coolingtime, weld quality, and more must be under careful observation.