Steel plate with super-low cost, 800MPa-grade high toughness and excellent weldability and manufacture method thereof

Abstract

The invention provides a steel plate with super-low cost, 800MPa-grade high toughness and excellent weldability and a manufacture method thereof. According to the manufacture method, metallurgical technical control methods of selecting super-low C-super-low Si-high Mn-highAls-(low Mo+high Cr) alloying-(Ti+Nb+V+B)microalloying composition system as basis, properly increasing the content of acid solution Als in steel, performing Ca treatment and leading the value of [(%C)+(%Mn) / 6+(%Si) / 24+(%Ni) / 40+(%Cr) / 5+(%Mo) / 4+(%V) / 14+7.3(%B)]*V cooling speed / (T starting cooling temperature-T terminating cooling temperature)*t to be more than or equal to 0.60 and less than or equal to 1.00, and the like are adopted, a specific controlled-rolling and online tempering process is optimized, the tempered steel plate has excellent weldability while the strength, low-temperature toughness, obdurability and plasticity of the tempered steel plate are matched, the problem of the weldability of a nickel-free tempered steel plate can be successfully solved, the welding HAZ has high strength, high toughness and excellent plasticity. The steel plate is especially suitable for hydroelectric pressure pipelines / volute casings / steel bifurcated pipes, marine platforms, large maritime working machinery and other large steel structures and equipment.

Description

technical field [0001] The invention relates to an ultra-low-cost 800MPa steel plate with high toughness and excellent weldability and a manufacturing method thereof. The tensile strength ≥ 780MPa, yield strength ≥ 690MPa, elongation δ 5 ≥18%, Charpy transverse impact energy (single value) at -40°C ≥100J, excellent weldability and plasticity of welded joints, Charpy impact energy (single value) at -40°C in the welding heat-affected zone (HAZ) ≥47J , The tensile elongation of the welded joint is ≥15%. 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 containers, building structures, automobile industry, railway transportation and machinery manufacturing. middle. The properties of low-carbon (high-strength) low-alloy steel depend on its chemical composition and the process syste...

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Problems solved by technology

[0004] In addition, the addition of a large amount of alloying elements to the steel plate leads to a significant decrease in the elongation rate of the steel plate, especially the uniform elongation rate. The lower uniform elongation rate is not only not conducive to the cold workability of the steel plate, but also affects the fatigue fracture resistance, stress concentration resistance and structure of the steel plate. The stability has a great impact, and there are great hidden dangers when used on giant steel structures such as pressure water pipes / volutes and steel bifurcated pipes in hydropower projects, thermal power turbine generator structures, offshore oil production platforms, and floating cranes for offshore ships , especially when natural disasters such as earthquakes and tsunamis occur, the steel structure is in danger of being damaged or even collapsed; therefore, when high-strength steel is used for large-scale fatigue and heavy-duty steel structures, it is generally hoped that the 80 kg high-strength steel has excellent strength, toughness, and strong plasticity. Tensile elongation δ 5 More than 18%, especially the uniform elongation of more than 10%

[0005] A large number of existing patent documents only explain how to realize the strength and low-temperature toughness of the base steel plate, improve the weldability of the steel plate, and obtain excellent low-temperature toughness of the welding heat-affected zone HAZ. , improve the tensile elongation of the steel plate and the uniformity of mechanical properties in the thickness direction, especially the welding heat-affected zone has excellent plasticity and toughness

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