INFLUENCE OF Ti-B MICRO ALLOYING ADDITIONS ON SUB-ZERO NOTCH-TOUGHNESS OF AWS E7018 ELECTRODE ALL-WELD METAL DEPOSITS

摘要

SMAW electrodes with various coating types deposit weld metal with various combinations of mechanical properties like tensile strength, elongation and notch toughness. In the case of ferritic. weld metals, basic coated low hydrogen electrodes show a lower Charpy-Vee notch impact transition temperature when compared with other type of coatings like rutile coating and cellulose coating. Hence they are used in applications, where a good combination of strength, toughness and freedom from risk of cold cracking are necessary. AWS E 7018 electrodes are tested at minus 30℃ for CVN impact properties. Experimental electrodes were designed and tested through a factorial testing method to understand the influence of simultaneous micro-alloying additions of titanium and boron on the CVN impact properties of all weld metal at, minus 30℃. The results show that Ti and B show a synergistic effect. The results are explained on the basis of nucleation and growth of acicular ferrite.