HT550 steel plate with ultrahigh toughness and excellent weldability and manufacture method thereof

Abstract

The invention provides an HT550 steel plate with ultrahigh toughness and excellent weldability and a manufacturing method thereof. Based on a component system which is subjected to ultralow C-high Mn-Nb microalloying-ultramicro Ti treatment, Mn/C is controlled in the range from 15 to 30, (%Si)*(%Ceq) is less than or equal to 0.050, (%C)*(%Si) is less than or equal to 0.010, (%Mo)*[(%C)+0.13(%Si)] is in the range from 0.003 to 0.020, Ti/N is in the range from 2.0 to 4.0, (Cu+Ni+Mo) is alloyed, Ni/Cu is greater than or equal to 1.0, Ca treatment is performed, and the ratio of Ca/S is within the range from 0.80 to 3.00; TMCP (Thermo-Mechanical Control Process) is optimized, so that the microscopic structure of the steel plate comprises fine ferrites and self-tempered bainite; and the steel plate has an average grain size below 15 microns, yield strength greater than or equal to 460 MPa, tensile strength in the range from 550 MPa to 700 MPa, a yield ratio less than or equal to 0.85, and -60 DEG C Charpy ballistic work (single value) greater than or equal to 60 J; therefore, the steel plate is capable of bearing large thermal input welding while having even and excellent match of strong obdurability and strong plasticity; and as a result, the steel plate is especially suitable for a sea bridge structure, an ocean wind tower structure, an ocean platform structure and a hydroelectric structure.

Description

Technical field [0001] The invention relates to an ultra-high toughness, excellent weldability HT550 steel plate and a manufacturing method thereof. The Charpy impact energy with a yield strength of ≥460MPa, a tensile strength of between 550MPa and 700MPa, and a yield ratio of ≤0.85 at -60°C is obtained through a TMCP process. (Single value) ≥60J, excellent weldability steel plate, the microstructure of the steel plate is fine ferrite + self-tempered bainite, and the average grain size is below 15μm. Background technique [0002] As we all know, low-carbon (high-strength) low-alloy steel is one of the most important engineering structural materials, widely used in oil and gas pipelines, offshore platforms, shipbuilding, bridge structures, boiler vessels, building structures, automobile industry, railway transportation and machinery manufacturing. in. [0003] The performance of low-carbon (high-strength) low-alloy steel depends on its chemical composition and the process system of...

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Problems solved by technology

In this way, the alloy content of the steel plate is high, which not only leads to high manufacturing cost of the steel plate, but also high carbon equivalent Ceq and welding cold crack sensitivity index Pcm, which brings great difficulties to on-site welding. Preheating is required before welding. After heat treatment is required, the welding cost increases, the welding efficiency decreases, and the working environment of the welding site deteriorates; the existing large number of patent documents only explain how to realize the strength and low-temperature toughness of the base metal steel plate, so as to improve

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