Issue34

G. Lesiuk et alii, Frattura ed Integrità Strutturale, 34 (2015) 290-299; DOI: 10.3221/IGF-ESIS.34.31 292 historic viaduct. The chemical composition has been obtained due to the gravimetric method. The results are included in Tab. 1. chemical element [%, wt] B-steel S-steel W-steel typical puddled steel, [5] C 0.03 0.06 0.08 0.03-0.15 Mn 0.06 0.1 0.25 0.054-0.11 Si 0.03 0.17 0.15 0.03-0.42 P 0.028 0.198 0.245 0.011-0.39 S 0.045 0.025 0.015 0.034-0.018 Table 1 : Chemical composition of the investigated material The chemical compositions of tested materials suggest that they belong to a group of the puddled steel. The results of metallographic observation (Fig. 3-4) confirm this fact. For the puddled steels, the high phosphorus content is very characteristic. Figure 3 : Microstructure of investigated puddled steel (1899-1904) – marked as B and W -steel, in (a) post-operating state (light microscopy) – presented nonmetallic inclusions typical for puddled steel, (b) post-operating state; ferrite grains with numbers of nonmetal inclusions, (c) magnified ferrite grains structure with nonmetallic inclusions – mainly silicates (A) and thick envelope of Fe 3 C III on the grain boundary (B) with numbers of degradation separations brittle phase inside ferrite grains (C), post-operating state SEM, etched 3%HNO 3 , (d) magnified ferrite grains with degradation symptoms; thick enveloper of Fe 3 C III (B) and separations inside ferrite grain (C), post-operating state SEM, etched 3%HNO 3 , (e) the microstructure of the W-steel in post-operating state, high numbers of deformed nonmetallic inclusions – an area of the extreme presence of the non-metallic inclusions, etched 3%HNO 3 , (f) typical ferrite grains structure of the W – steel, based on [2] Static tensile test results and impact resistance examination The basic mechanical properties of delivered steel are collected in Tab. 2. A significant change in the impact strength has been noted. The yield tensile stress and ultimate tensile stress are not always coincident with a level of microstructural degradation processes. It is postulated that the measure of degradation should be the impact strength as a basic (qualitative) measure in engineering practice.