Study on the effect of different arc welding techniques on the metallurgical and mechanical properties of ramor 500 armour steel

In this study, RAMOR 500 armor steel samples were automatically welded using Hybrid Plasma Arc Welding (HPAW), Gas Metal Arc Welding (GMAW) and Cold Metal Transfer Arc Welding (CMT) methods. In order to investigate the effects of three different fusion welding methods on the metallurgical and mechanical properties of Ramor 500 armor steel, the welded samples were examined with optical microscope, scanning electron microscope (SEM), EDS and subjected to Vickers hardness, tensile test, three point bending test and notch impact tests. The weld metal region of the HPAW and GMAW samples consisted primarily of austenite and small amounts of martensitic and partially δ-ferrite phases. In the CMT welded sample, it was determined that the weld zone consisted mainly of austenite and a minor amount of δ-ferrite. Hardness of both the weld metal and HAZ (Heat Affected Zone) regions were found to be higher than the base metal. Thus, the problem of low hardness in the weld and HAZ zones, which is commonly observed in the arc welding of the armor steels, was eliminated. Although the tensile strengths of the welded samples were lower than the monolithic armor steel, satisfactory tensile strengths were obtained by the HPAW method according to the literature. The tensile strengths obtained by the HPAW, GMAW, and CMT welding methods were obtained as 65%, 50% and 40% of the base metal, respectively. Brittle fractures of cleavage type occurred in the HPAW and GMAW welded samples, while intergranular fractures occurred in samples welded by CMT method. Samples welded by HPAW and GMAW fractured from coarse grained regions, and the sample welded by CMT fractured from the weld metal region in the tensile test and bending tests. When examined in terms of notch toughness, it was determined that CMT welded samples showed better impact resistance than base metal. The HPAW and GMAW welded samples displayed less impact resistance than the base metal, but they did display better impact resistance compared to many studies in the literature. The impact toughness values of both the monolithic Ramor 500 and the welded samples decreased with decreasing temperature. The HPAW method was found to be the most time, energy and cost-efficient method among the three welding methods, and comparisons of the results of the study showed that HPAW produces less deterioration in the microstructure and mechanical properties of the Ramor 500 steel.