Steel plate resistant to zinc-induced crack and manufacturing method therefor

Patent metadata

Field	Value
Publication number	US-2016097111-A1
Application number	US-201414782965-A
Country	US
Kind code	A1
Filing date	Mar 5, 2014
Priority date	Jun 19, 2013
Publication date	Apr 7, 2016
Grant date	—

Abstract

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.

First claim

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.

2 . A method for manufacturing the steel plate resistant to zinc-induced crack of claim 1 , comprising the following steps:
smelting and casting: a slab is formed by smelting and continuous casting according to the above-mentioned components and using a light reduction technique, the light reduction rate for continuous casting is controlled between 2% and 5%, the pouring temperature of a tundish is between 1530° C. and 1560° C., and the withdrawal speed is 0.6 m/min-1.0 m/min; heating: the heating temperature of the slab is 1050° C.-1150° C., the slab is descaled with high pressure water after being removed from the furnace, and the descaling can be repeated if it is incomplete; rolling: a first stage is a normal rolling, wherein the maximum capacity of a rolling mill is used for an uninterrupted rolling, the pass reduction rate is ≧10%, the accumulated reduction rate is ≧45%, and the final rolling temperature is ≧980° C.; and a second stage adopts a controlled rolling in an austenite single phase region, wherein the initial rolling temperature of the controlled rolling is 800° C.-850° C., the pass reduction rate of the rolling is ≧8%, the accumulated reduction rate is ≧50%, and the final rolling temperature is 760° C.-800° C.; and cooling: after the controlled rolling is finished, the steel plate is immediately transported to accelerated cooling equipment to perform accelerated cooling on the steel plate, wherein the initial cooling temperature of the steel plate is 750° C.-790° C., the cooling rate is ≧5° C./s, the stop-cooling temperature is 350° C.-550° C., and thereafter the steel plate with a thickness of ≧25 mm is naturally air-cooled to not less than 300° C., and then slow-cooled and dehydrogenated, the slow cooling process consisting in maintaining the steel plate at not less than 300° C. for at least 36 hours; and the steel plate with a thickness of <25 mm is naturally air-cooled to room temperature.

3 . The method for manufacturing a steel plate resistant to zinc-induced crack of claim 2 , characterized by being 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, and a zinc-spray coated corrosion-resistant steel plate for coast bridge structures.

Assignees

• Baoshan Iron & Steel

Inventors

• Liu Zicheng
• Wu Yong
• Li Xianju

Classifications

• C21D8/02

  during manufacturing of plates or strips (C21D8/12 takes precedence) · CPC title

• C21D8/0226

  Hot rolling · CPC title

• C21D6/001

  containing Ni (C21D6/004 takes precedence) · CPC title

• C22C38/002

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title

• B22D11/001

  of specific alloys · CPC title