Structural Organization of Steel to Ensure Special Equipment Safety

Abstract

   Introduction. At present, great success has been achieved in the field of creating effective protective materials. Various non-metallic, metal-ceramic, and also composite materials act as armor elements. However, most of the armor elements of vehicles and personal protective equipment (PPE) are steels that, along with high ballistic resistance, have a high mass. In this regard, the relevance of the article is related to the possibility of lightening typical protective elements when using a material that has a structural organization like a natural ferrite-martensite composite (NFMC).   The work objective is to evaluate the prospects of using steel with an oriented structure as an effective protective material when exposed to high-speed concentrated impact of high power in comparison with the steel materials used.   Materials and Methods. The features and disadvantages of effective armor steels are revealed, a comparative analysis is carried out with steel oriented as NFMC. The assessment of 14G2 steel microstructure state with different hardening temperatures (730 °C and 760 °C) was carried out by the method of microstructural analysis. In relation to the topic of the study, the prospects for the use of low-carbon ferritic-martensitic steel were shown based on the laws of fracture mechanics and their comparison with the experimental data obtained on a sample of 14G2 steel with dimensions of 150 × 44 × 7 mm after testing for bullet resistance by cartridges with a steel core and armor-piercing cartridges with a tungsten core made of SVD rifles and AK-74 assault rifles of 7.62 mm and 5.45 mm caliber, respectively.   Results. The possibilities of resistance to fracture of steel with an oriented ferritic-martensitic structure are evaluated in comparison with typical homogeneous and heterogeneous steel materials. The resistance of such steel is related to the nature of the development of fracture, expressed in the deceleration of the crack during delamination at the ferrite-martensite boundaries. When a delamination is formed, a crack expends energy on delamination and changes its direction, which subsequently leads to a complete stop of the fracture process.   Discussion and Conclusion. The disadvantages of armor elements made of homogeneous and heterogeneous steel materials, associated with a high effective thickness of the protective element and the laborious process of obtaining a steel sandwich, respectively, can be solved by using oriented ferritic-martensitic steel. The data presented indicate a higher fracture resistance due to a special crack propagation mechanism, which is relevant in the development of armored vehicles. This makes it possible to reduce the total mass of combat vehicles associated with a decrease in the effective thickness of protective elements while maintaining the required class of resistance to high-speed impact loading, which will increase their mobility and reduce fuel consumption.