P690QL2 steel plate with ultrahigh die welding and low-temperature performance and manufacturing method of P690QL2 steel plate

Through specific chemical composition and multi-stage rolling combined with tempering heat treatment technology, the problems of high strength, low temperature toughness and easy welding of P690QL2 steel plates for cargo tanks in LCO2 transport ships are solved, and the high mold welding performance and low temperature toughness requirements of steel plates are achieved, meeting the conditions for the use of cargo tanks in LCO2 transport ships are met.

CN120485655APending Publication Date: 2025-08-15ANGANG STEEL CO LTD
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Patent Information

Application Number
CN202510578631.X
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Filing Date
2025-05-07
Publication Date
2025-08-15

AI Technical Summary

Technical Problem

The prior art is difficult to produce P690QL2 steel plates for cargo tanks for LCO2 transport vessels, which meet the requirements of high strength, low temperature toughness and easy welding, especially on thin-spec steel plates. The existing technology is difficult to ensure the uniformity of steel plate structure performance and the plate quality of thin-spec steel plates.

Method used

The specific chemical composition design and multi-stage rolling combined with tempering heat treatment technology are adopted, including converter + LF + VD refining, continuous casting, slow cooling, heating, rolling, quenching and tempering heat treatment, to control the composition and structure of the steel plate, and through the second phase particle precipitation and strengthening of Mo and V and the fine crystallization of Ti, the high mold welding performance and low temperature toughness of the steel plate are ensured.

Benefits of technology

P690QL2 steel plate with a thickness of 5 to 60mm was produced, with yield strength ≥690MPa, tensile strength 770 to 940MPa, elongation ≥17%, V-type impact work ≥150J, and -55℃ CTOD>0.2mm, meeting the use requirements of the cargo tank of the LCO2 transport ship.

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Abstract

The invention relates to a P690QL2 steel plate with ultrahigh die welding and low-temperature performance and a manufacturing method of the P690QL2 steel plate. The P690QL2 steel plate comprises the following chemical components in percentage by weight: 0.04%-0.12% of C, 0.02%-0.08% of Si, 1.0%-1.2% of Mn, 1.5%-2.5% of Ni, 0.3%-0.7% of Cr, 0.7%-0.9% of Mo, 0.07%-0.12% of V, 0.02%-0.04% of Ti, less than or equal to 0.002% of S, less than or equal to 0.002% of P, 0.03%-0.06% of Als and the balance of Fe and inevitable impurity elements. The steel plate is applied to the liquid cargo tank of the LCO2 transport ship, has high strength and low-temperature toughness requirements, is easy to weld and has ultrahigh die welding performance, the V-type impact energy of the steel plate at-60 DEG C is larger than or equal to 150 J, the CTOD at-55 DEG C is larger than 0.2 mm, and the machining and welding use requirements of pressure-bearing equipment are met.
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