Effect of Chemical Composition and Structure on Mechanical Properties of High-Strength Welding Steels

Based on the analysis of the Russian-made 4 to 16 mm thick rolled products produced by thermomechanical rolling from high-strength (yield point: 433 to 828 MPa) low-alloyed welding steels obtained as a result of 15 melting runs, the effect of chemical composition and structure on the mechanical properties, such as yield point, impact toughness, and impact toughness anisotropy factor, was studied. It was shown that the yield point of manganese steel (1.62–1.80 wt. % Mn) is mainly caused by microalloying with titanium, and to a lesser degree – with niobium and vanadium. An increase in the yield point of steel in excess of 700 MPa increases its tendency to impact toughness anisotropy. Within the concentration range from 0.001 to 0.08 wt. % Ti, the value of anisotropy factor K_a , which varies from 1.45 to 1.80, does not depend on Ti content, but increases sharply to K_a = 3.19 once the Ti content increases (in excess of 0.08 wt. %). A considerable negative effect of Nb content in steel on impact toughness (KCV^{– 40}), measured on transverse specimens, has been established. A joint negative effect of Ti + Al on KCV^{– 40} is somewhat less pronounced. The presence of Al in the inclusions of complex composition (Ti-Al-Cr) noticeably reduces (by 4.5 times) the negative effect of Ti on KCV^{– 40} of highstrength manganese steel.