Investigation of weldability of Miilux Protection 500 armour steels by gas metal arc welding method

Abstract

Miilux Protection 500 (MP 500) steel is a recently developed armour material that has gained prominence in the defence industry due to its high hardness, strength, and resistance to ballistic penetration. The filler wire selection is critical in determining the mechanical performance of welded joints involving such high-performance steels. Since filler wires with properties matching those of MP 500 are not yet commercially available, this study aimed to identify the most suitable alternatives. In this context, Gas Metal Arc Welding (GMAW) was performed using three commercially available filler wires: ER100S-G, ER307, and ER312. The mechanical and microstructural properties of the welded joints were comparatively evaluated. The highest tensile strength was achieved with ER100S-G at an average of 970 MPa, while the lowest was observed with ER312 at 704 MPa. This disparity stems from the wires' differing alloy compositions and design purposes-ER100S-G is formulated for high-strength applications, whereas ER312 is optimised for crack resistance, particularly in dissimilar metal welding, resulting in lower strength. Weld joint efficiency, calculated relative to the base material, was 55% for ER100S-G, 43% for ER312, and 40% for ER307. These findings provide insight into selecting appropriate filler materials for welding armour-grade steels and optimising mechanical performance.