Issue 37

D. Angelova et alii, Frattura ed Integrità Strutturale, 37 (2016) 265-271; DOI: 10.3221/IGF-ESIS.37.35 266 Standard chemical composition and mechanical properties Steel S355J2+N is low-carbon, low-alloy structural steel with chemical composition shown in Tab. 1 and mechanical properties presented in Tab. 2, both accordingly the standard EN 10025-2:2004 "Hot rolled products of structural steel". C Mn Si P S Cr Ni Cu Mo As Al V Ti 0.16- 0.18 1.10- 1.16 0.20- 0.26 0.008- 0.014 0.002- 0.010 0.040- 0.120 0.060- 0.150 0.180- 0.320 0.009- 0.031 0.008- 0.027 0.025- 0.040 0.031- 0.042 0.022- 0.037 Table 1 : Chemical composition of Steel S355J2+N (weight %) Yield strength, R e , MPa Tensile strength, R m , MPa Total Elongation, А , % Impact test*, К, J 345 - 430 470 - 630 min 20 – 22 % min 27 * * test piece with V-figurative notch; Т= - 20 о С Table 2 : Mechanical Properties of Hot-Rolled Sheet’s Steel S355J2+N with nominal thickness 30 and 40 mm Equipment and technological experiments According to EN 10025-2:2004, 40 experiments have been carried out – two groups of 20 experiments to obtain two different thicknesses of the finished product (final plate/sheet), respectively of 30 mm and 40 mm. Rolling mill used is schematically represented in Fig. 1 as a complex of mechanical components and equipment for hot rolling of heavy plates/sheets, their further processing and transportation. The mill consists of a reverse Roll Mill type "Quarto", and equipment for straightening, cutting and marking of finished products [6-7]. Figure 1: Scheme of Quarto Reversing Rolling Stand for hot-rolled steel plates/sheets in the Bulgarian Metallurgical Plant “STOMANA Industry SA”.