The results of the research works treated in the both dissertations revealed the weak points of the analysed domestic high-strength low-alloy structural steel and the main causes for those weaknesses. We have found a way how to reduce the weaknesses by using either both proper consumables and optimal welding parameters or applying sub resonant vibrating during welding, but unfortunately, this results in higher costs. We have acquired knowledge about the technology how to prepare fatigue cracks of the predestined size and the proper shape on the wide plate WP specimens in fair thick butt-welded joints. We have proven a practical use of the thermal cycle simulator for the investigations in the weld metals of multi-pass welded joints not only in the heat-affected zones as it was common till now. We developed a useful tool for possible simulation of the sub resonant vibrating during welding using oven for quenching or tempering. Positive or negative effects of vibrating during welding are perceived for those regions of welds which temperature is not higher than 500 degrees C during deposition of the next weld runs.