FRACTURE MANIFESTATIONS OF LOW-ALLOYED 2. 6CRMOV STEELS UNDER TENSILETEST CONDITIONS IN SUBTRANSITION TEMPERATURE-RANGE

The work deals with investigation of influence of alloying elements (M o, V), impurities (P), and hydrogen on sharp-notch strength and the fa ilure characteristics of low-alloyed 2.6CrMoV steels at the temperatur e of -80 degrees C. After embrittling treatment, tile steels show vari ous failure modes, in dependence on both the P content and the content of the alloying elements. The sharp-notch strength of tile steels inc reases and the area reduction decreases with alloying elements (Mo, V) (.) addition. Phosphorus does not affect the sharp-notch strength esse ntially, but it affects the area reduction. The prior austenite grain boundary P-segregation causes an increase of the intergranular fractur e portion (IFP). It was confirmed that the Mo (up to 0.7%) influences beneficially the intergranular fracture resistance uf the steels and t he carbide particles formation at the Drier austenite grain boundaries during tempering is caused by its increase up to (0.95%) during tempe ring. The vanadium influence on the failure mode of the investigated s teels was manifested by the decrease of the inclination to hydrogen em brittlement. Both the carbides formation and impurity segregation lead s to an intergranular fracture portion increase. The hydrogen absorbed by the samples causes an increase in the fractured stress, decrease o f the material area reduction and increase of the intergranular fractu re portion.