Baoshan Iron & Steel Co., Ltd.

Zicheng Liu

Xianju Li

Yong Wu

Qing Shi

A steel plate having excellent resistance to fatigue crack growth and manufacturing method thereof, wherein the components of the steel plate in weight percentage are: 0.040-0.070% of C, 0.40-0.70% of Si, 1.30-1.60% of Mn, less than or equal to 0.013% of P, less than or equal to 0.003% of S, less than or equal to 0.30% of Cu, less than or equal to 0.30% of Ni, less than or equal to 0.10% of Mo, 0.008-0.018% of Ti, 0.015-0.030% of Nb, less than or equal to 0.0040% of N, 0.0010-0.0040% of Ca, and the balance being Fe and inevitable impurities. By controlling [% C]&#xd7;[% Si] between 0.022-0.042, {([% C]+3.33[% Nb])&#xd7;[% Si]}&#xd7;V/Tbetween 1.15&#xd7;10&#x2dc;2.2&#xd7;10, carrying out a Ca treatment, and Ca/S=1.0-3.0 and (% Ca)&#xd7;(% S) 0.28&#x2264;1.0&#xd7;10, the optimizing the TMCP process, the finished steel plate has a microstructure which a duplex-phase structure of ferrite+uniformly and dispersedly distributed bainite and has an improved resistance to fatigue crack growth.

Good fatigue- and crack growth-resistant steel plate and manufacturing method therefor

An HT550 steel plate with ultrahigh toughness and excellent weldability and a manufacturing method thereof are disclosed. Based on a component system with ultralow-C, high-Mn, Nb-microalloying, ultramicro Ti treatment, Mn/C is controlled in the range of 15&#x2dc;30, (% Si)&#xd7;(% Ceq) is less than or equal to 0.050, (% C)&#xd7;(% Si) is less than or equal to 0.010, (% Mo)&#xd7;[(% C)+0.13(% Si)] is in the range of 0.003&#x2dc;0.020, the ratio Ti/N is in the range of 2.0&#x2dc;4.0, the steel plate is alloyed with (Cu+Ni+Mo), Ni/Cu is greater than or equal to 1.0, Ca treatment is performed, and Ca/S is in the range of 0.80&#x2dc;3.00; by optimizing TMCP process, the steel plate has microstructures of fine ferrite plus self-tempered bainite with an average grain size being less than or equal to 15 &#x3bc;m, yield strength being 460 MPa or more, tensile strength being 550&#x2dc;700 MPa, yield ratio being 0.85 or less, and &#x2212;60&#xb0; C. Charpy impact energy (single value) being 60 J or more; therefore, the steel plate is capable of bearing large thermal input welding while obtaining uniform and excellent strength, toughness, and strong plasticity matching, and is especially suitable for sea bridge structures, ocean wind tower structures, ocean platform structures and hydroelectric structures.

HT550 steel plate with ultrahigh toughness and excellent weldability and manufacturing method of the same

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&#x2014;(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&#x2265;15, [(% Mn)+0.75(% Mo)]&#xd7;(% C)&#x2264;0.16, Nb/Ti&#x2265;1.8 and Ti/N is between 1.50 and 3.40, CEZ&#x2264;0.44% and the B content is &#x2264;2 ppm, Ni/Cu&#x2265;1.50; a Ca treatment is performed and the Ca/S ratio is controlled between 1.0 and 3.0, with (% Ca)&#xd7;(% S)&#x2264;1.0&#xd7;10; 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 &#x3bc;m, 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.

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Shanghai, China

Zicheng Liu