Nastajanje niobij karbonitridnog eutektika u konstrukcijskom čeliku

The reduction of area in the through thickness direction is an essential mechanical property of thick steel heavy plates. By a routine control, a very small through thickness reduction of area was found for tensile specimen of a 90 mm plate. Careful investigations of the fracture and section of specimens cut from the as solidified continuously cast 250mmthick slab showed that the cause was the presence of coarse particles of niobium carbonitride as constituent of the quasi eutectic Fe-Nb(C, N) that form because of the centerline segregation of niobium.Kontrakcija u smjeru debljine je vrlo važno mehaničko svojstvo debelih limova od konstrukcijskih čelika. Pri rutinskoj kontroli svojstava čelika utvrđena je ispitivanjem na razvlačenje na uzorku lima debljine 90 mm, vrlo mala kontrakcija u smjeru debljine lima. Ispitivanja prijelomne površine i presjeka uzoraka izrezanih iz kontinuirano odlivenog 250 mm debelog slaba pokazala su da je uzrok tome prisutnost grubih čestica niobijevih karbonitrida u kvazieutektiku Fe-Nb(C, N) koji je nastao zbog središnjih segregacija niobija

Centreline formation of Nb(C, N) eutectic in structural steel

The reduction of area in the through thickness direction is an essential mechanical property of thick steel heavy plates. By a routine control, a very small through thickness reduction of area was found for tensile specimen of a 90 mm plate. Careful investigations of the fracture and section of specimens cut from the as solidified continuously cast 250mmthick slab showed that the cause was the presence of coarse particles of niobium carbonitride as constituent of the quasi eutectic Fe-Nb(C, N) that form because of the centerline segregation of niobium