STEEL PLATE RESISTANT TO ZINC-INDUCED CRACK AND MANUFACTURING METHOD THEREFOR

摘要

The invention discloses a steel plate resistant to zinc-induced crack and a manufacturing method therefor. A low-alloy steel subjected to low C-ultra low Si-high Mn-low Al—(Ti+Nb) microalloying treatment is taken as a basis; the Al content in the steel is appropriately reduced; the conditions are controlled so that Mn/C≧15, [(% Mn)+0.75(% Mo)]×(% C)≦0.16, Nb/Ti≧1.8 and Ti/N is between 1.50 and 3.40, CEZ≦0.44% and the B content is ≦2 ppm, Ni/Cu≧1.50; a Ca treatment is performed and the Ca/S ratio is controlled between 1.0 and 3.0, with (% Ca)×(% S)0.28≦1.0×10−3; and a TMCP process is optimized, so that a finished steel plate has a micro-structure of ferrite+bainite colonies which are tiny and dispersedly distributed, with an average grain size of not greater than 10 μm, has homogeneous and excellent mechanical properties, excellent weldability and zinc-induced crack resistance, and is thus especially suitable as a zinc-spray coated corrosion-resistant steel plate for marine structures, a zinc-spray corrosion-resistant steel plate for extra-high voltage power transmission structures, a zinc-spray coated corrosion-resistant steel plate for coast bridge structures, and the like.

主权项

1. A steel plate resistant to zinc-induced crack, the components thereof in weight percentages being:
C: 0.05%-0.090% Si: ≦0.20% Mn: 1.35%-1.65% P: ≦0.013% S: ≦0.003% Cu: 0.10%-0.30% Ni: 0.20%-0.50% Mo: 0.05%-0.20% Nb: 0.015%-0.035% Ti: 0.008%-0.018% N: ≦0.0060% Ca: 0.0010%-0.0040% B: ≦0.0002%, and the balance being Fe and inevitable impurities; and at the same time the contents of the above-mentioned elements must satisfy the relationships as follows: Mn/C≧15; [(% Mn)+0.75(% Mo)]×(% C)≦0.16; CEZ<0.44%, the B content is ≦2 ppm, wherein, CEZ=C+Si/17+Mn/7.5+Cu/13+Ni/17+Cr/4.5+Mo/3+V/1.5+Nb/2+Ti/4.5+420B; Ni/Cu≧1.50; Nb/Ti≧1.8, and Ti/N is between 1.50 and 3.40; Ca/S is between 1.00 and 3.00, and (% Ca)×(% S)0.28≦1.0×10−3; a finished steel plate has a yield strength of ≧460 MPa, a tensile strength of ≧550 MPa, and an impact energy at −60° C. (single value) of ≧47 J, the micro-structure of the finished steel plate is ferrite+bainite colonies which are tiny and dispersedly and homogeneously distributed, with an average grain size controlled at not greater than 10 μm, and the micro-structure of a welding heat-affected zone is tiny and homogeneous ferrite+a small amount of pearlite.