Determination of the class of steel by small samples

Introduction. The data of the results of the inspection of steel structures are given, based on the analysis of which strength classes of structural steels are established. The goal has been solved by determining the chemical composition of metal structures and full-scale tests of the mechanical characteristics of steel structures, followed by a calculated conversion of the hardness index HB to the value of temporary tensile strength σv. Materials and methods. Strength indicators of metal structures are determined by non-destructive express method by means of a portable hardness tester of the dynamic principle of action. For the calculated determination of the breaking strength σv adopted the average lengthening coefficient kδ. By its value, the indicators of elongation and contraction are established, as well as the yield strength of the metal. Based on the calculated standard indicators of plasticity (δ, ψ) and strength (σv, σt), the complex criterion C equation is compiled. Using it, calculated the uniform elongation δр and the transverse narrowing ψр, which were used to assess the tensile strength (Sv, Sk) and fatigue (σ–1, τ–1). The chemical composition of small-sized samples in the form of metal shavings was determined by x-ray fluorescence. Additionally, the chemical composition of the steel was monitored using a scanning microscope with an attachment for determi­ning the chemical composition by energy dispersive x-ray spectroscopy. Results. The proposed research method makes it possible to conduct full-scale tests of metal structures and reduces the complexity of the selection and delivery of samples for laboratory research. The results obtained by both methods are correlated with the source data (design documentation for the object of the survey). Conclusions. An integrated method of sampling and direct measurement of hardness on site allows one to determine the chemical composition of metal structures, the grade and type of structural steel and its mechanical properties. At the same time, the scientific novelty is the given technique as a whole, which is characterized by a significant reduction in labor costs and minimization of damage to the objects under study.