Effect of Microalloyed Steel Welding Procedure on Fatigue Crack Growth
The application of high strength steel, e.g. NIOMOL 490K, developed for highly loaded welded structures and low temperatures, depends on properties of welded joint critical regions. Strength, toughness and crack resistance of welding joints have to be tested. Fatigue crack growth rate is defined by relation of stress intensity factor range, δK, induced by variable loading and crack extension for one cycle, da/dN. For that precraked specimen has to be tested [1]. Samples for investigation had been prepared by metal manual arc welding (MMAW) and MAG welding. Two plates of 16 mm thick NIOMOL 490K steel of nominal yield stress 490 MPa [2], had been prepared for asymmetric 2/3 X welded joint by edge machiningInitial notch for fatigue crack growth rate testing was machined in weld metal and HAZ [3].