Ultrahigh toughness steel plate for deep-water pressure resistant shell and manufacture method thereof

Abstract

The invention discloses ultrahigh toughness steel plate for deep-water pressure resistant shell and manufacture method thereof. The steel plate comprises (by wt%) C 0.05-0.09, Si less than or equal to 0.10, Mn 0.45-0.95, P less than or equal to 0.012, S less than or equal to 0.0030, Cr 0.40-0.80, Mo 0.40-0.80, Ni 3.50-5.50, Cu 0.20-0.50, Ti 0.003-0.010, Als 0.010-0.030, V 0.040-0.080, N less than or equal to 0.0060, O less than or equal to 0.0030, Ca 0.001-0.004, and Fe and unavoidable impurity in balance. The method adopts optimized TMCP and offline quenching and tempering (QT) process, endows microscopic structure of product steel plate with fine low carbon tempered martensite and small amount of tempered bainite, with average packet size smaller than 15 Mum, solves the problem of overquenching of ultrahigh strength steel plate surface, and is especially suitable for use in hydroelectric pressure water pipe and steel yoke pipe of ultrahigh water head (greater than or equal to 1,200 m) power station, and polar ocean platform and deep-water pressure resistant shell.

Description

technical field [0001] The present invention relates to an ultra-high-strength steel plate and a manufacturing method thereof, in particular to an ultra-high-strength toughness steel plate for a deep-water pressure-resistant shell and a manufacturing method thereof. Single value) ≥ 100J, elongation at break δ 5 ≥17% and uniform elongation Ag≥7%, excellent weldability. 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. The performance of low-carbon (high-strength) low-alloy steel depends on its chemical composition and manufacturing process, among which strength, toughness, plasticity and weldability are the most important properties of low-carbon (high-strength) low-alloy st...

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Problems solved by technology

[0007] The purpose of the present invention is to provide an ultra-high-strength toughness steel plate for deep-water pressure-resistant shells and its manufacturing method. It adopts the combination of online TMCP+QT and adopts a relatively low-cost alloy combination design to obtain ultra-high strength. At the same time, the plastic toughness of the steel plate , weldability is also excellent, and successfully solved the contradiction between the strength, plasticity, low temperature toughness and weldability of the ultra-high strength steel plate and the problem of over-quenching of the surface (sub) surface of the steel plate, greatly reducing Sensitivity to surface defects (notches) under ultra-low temperature conditions; this is one of the biggest difficulties of this steel type, and it is also one of the key core technologies

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