Marine work steel plate with excellent low-temperature toughness and low yield ratio and manufacturing method thereof

Abstract

The invention discloses a maritime work steel plate with excellent low-temperature toughness and low yield ratio and a manufacturing method thereof. The steel contains the following components: 0.06%-0.12% of C, 0.20%-0.40% of Si, 1.45%-1.65% of Mn, less than or equal to 0.01% of P; less than or equal to 0.002% of S, 0.15%-0.25% of Ni, 0.15%-0.30% of Cu, 0.015%-0.04% of Nb, 0.007%-0.025% of Ti, 0.015%-0.045% of Alt, and the balance of iron and inevitable impurities. The casting blank heating temperature is 1150-1180 DEG C, the first-stage rolling temperature is 1100-1150 DEG C, the second-stage rolling temperature is 890-940 DEG C, the single-pass reduction rate is larger than or equal to 9%, the third-stage rolling temperature is 800-840 DEG C, the accumulated reduction rate is 35%-50%, and the finish rolling temperature is 770-810 DEG C; the initial cooling temperature is 710-750 DEG C, the average cooling speed is greater than or equal to 5 DEG C/s, and the self-tempering temperature is 280-350 DEG C; the slow cooling pit is insulated and cooled, and the stacking time is longer than or equal to 24 hours; and the steel plate has excellent toughness at -40 DEG C.

Description

technical field [0001] The invention belongs to the field of iron and steel material preparation, and in particular relates to a marine steel plate with yield strength ≥ 420 MPa, yield strength ratio below 0.80 and excellent low-temperature toughness. Background technique [0002] As a key structural material for offshore engineering equipment, steel is widely used in offshore wind power, production platforms, and submarine pipelines. The service environment of steel plates for offshore structures is harsh, not only to bear gravity loads, but also to bear wind loads, wave loads, ocean current loads, ice loads, and earthquake loads, and the service life of marine engineering equipment is 50% longer than that of ships. The requirements are extremely high, and the steel plates used are gradually developing in the direction of high strength, high toughness, easy weldability, good corrosion resistance, large thickness, and large specifications. [0003] Offshore equipment and of...

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Problems solved by technology

[0004] The invention patent of application number CN201810631503.7 "a low-temperature steel with excellent CTOD characteristics and its manufacturing method" optimizes the TMCP process through the combination design of main alloy elements, the flexible use of microalloy elements and the harmless treatment of inclusion elements. Provides a steel plate manufacturing method with yield strength ≥ 420MPa, tensile strength ≥ 530MPa, CTOD ≥ 0.15mm at -40°C, Akv (-60°C) ≥ 47J, and can be welded with high heat input, but its composition Al≤ 0.010%, while the international standards and relevant classification society regulations for marine engineering steels all require the lower limit of Al element content, which limits the scope of application of this invention patent

[0005] The invention patent of application number 201410626991.4 "420MPa-level large-thickness hot-rolled steel plate for marine engineering and its production method" provides a 420MPa-level large-thickness hot-rolled steel plate for marine engineering and its production method, which optimizes other alloys in the steel plate by adjusting The ratio of elements, combined with the two-stage controlled rolling and controlled cooling process, can produce steel plates with good structure, comprehensive performance and welding performance, but the steel plate produced does not reflect the minimum single value of core toughness, and the maximum thickness of the steel plate invented is 70mm. Restricted scope of use

[0006] The invention patent of application number 201810841006.X "thick gauge 420MPa grade low yield ratio low temperature bridge steel and its production method" discloses a thick gauge 420MPa grade low yield ratio low temperature bridge steel plate and its production method. Appropriate controlled rolling, controlled cooling and tempering heat treatment process for thick steel plates can solve the problem of unstable performance of thick plates for a long time, but its yield ratio is high, and the production process of TMCP + tempering is adopted, which increases the production cycle and cost

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