Analysis of the Potential for Enhancing Resistance to Dynamic Loads of Welded Joints in Hardox 450 Steel Through Heat Treatment

Abstract Welding procedures in high-hardenability steels often lead to adverse microstructural changes, resulting in a sharp decline in mechanical properties within the weld metal zone and the heat-affected zone. Due to the limited tensile strength Rm of commercially available welding consumables, which in many cases do not exceed 1000 MPa, the reduction in mechanical properties can reach up to 60% in steels with hardness levels of 600 HBW. Martensitic boron steels are among the materials with the highest mechanical strength indices and are used both in components exposed to abrasive wear and in ballistic protection. Consequently, welding techniques often produce joint zones with functional properties (e.g., ballistic resistance or resistance to abrasive wear) that fail to meet the required performance of the base material. Only through advanced welding techniques, the use of high-quality fillers, and subsequent heat treatment can the highest mechanical strength indices be achieved in the weld zone. This article presents the results of tests on the resistance of 450 HBW grade steel welded joints to dynamic loads. The research demonstrated that, when subjected to firing using intermediate 7.62 × 39 mm ammunition (43 model, PS bullet) from a distance of 10 m, a minimum plate thickness of 5 mm ensures material continuity across all characteristic zones of the welded joint.