THE BEHAVIOUR OF MICRO-ALLOYED STRUCTURAL STEELS OF HIGH-STRENGTH DURING HOT-DIP GALVANIZING

DAS VERHALTEN MIKROLEGIERTER BAUSTAEHLE MIT HOEHERER FESTIGKEIT BEIM FEUERVERZINKEN

THE BEHAVIOUR OF STRUCTURAL STEEL ALLOYED WITH TITANIUM AND VANADIUM, VANADIUM, NIOBIUM AS WELL AS VANADIUM AND NIOBIUM, AND CONTAINING (A) A LITTLE AND (B) NO PERLITE (TENSILE STRENGTH BETWEEN 470 AND 630 N/MM SQ CORRESPONDING APPROXIMATELY TO 48 AND 64 KP/MM SQ) AFTER HOT GALVANISING WAS STUDIED. PARTICULAR CARE WAS GIVEN TO THE EFFECT OF SILICA CONTAINED IN THE STEEL ON THE FORMATION OF THE ZINC COATINGS. IT WAS FOUND THAT THE ALLOYING ELEMENTS TI, V AND NB HARDLY AFFECT THE GALVANIZING BEHAVIOUR AT ALL. ON THE OTHER HAND, THERE IS A CONSIDERABLE EFFECT DUE TO THE SI CONTENT OF THE STEEL IF PRESENT TO AN EXTENT OF ABOUT 0.03 - 0.1 %. A SIGNIFICANTLY INCREASED FE-ZN REACTION WAS OBSERVED HERE (MAXIMUM AT ABOUT 0.065 % SI) WHEREBY EXTREMELY THICK COATINGS ARE FORMED. THIS EFFECT IS INCREASED WITH HIGHER ZINC BATH TEMPERATURES.