The relationship between the strength parameters of historical steels and Brinell hardness, and the determination of its ultimate strength

The paper analyses the relationship between the Brinell hardness of steels produced between 1895 and 1930 and their strength parameters, namely yield strength and ultimate tensile strength. After preparing appropriate specimens from four historical steel structures, the Brinell hardness of unloaded samples was measured using a stationary hardness tester, as well as on samples subjected to axial loading using a portable hardness tester. Subsequently, destructive tensile tests were performed, allowing both yield strength and ultimate tensile strength to be determined. The obtained results were subjected to statistical analysis, which led to the derivation of relationships between Brinell hardness and strength parameters for a dataset consisting of four subsets of historical steels from the years 1895–1930. The investigations were supplemented by analyses of chemical composition and microstructure. Due to the atypical nature of the identified relationships, it was necessary to extend the analyzed dataset to include historical bridge steels produced between 1873 and 1938. Based on the established relationships between Brinell hardness and strength parameters of historical steels, an algorithm for estimating the strength parameters of historical steels using Brinell hardness was developed for design purposes. The paper also presents examples of historical structures for which the steel strength parameters were determined. These parameters are required by both the current Polish standard and standards harmonized with European regulations. The paper concludes with practical recommendations. • Non-destructive testing of steel Brinell hardness. • Destructive tensile tests of the steel. • Chemical and microstructure testing. • Statistical analysis of the research results. • Estimation of historical steel strength parameters based on Brinell hardness.