Quenched and tempered eh550 extra-thick steel plate for marine engineering and its manufacturing method

Abstract

The invention discloses a modified EH550 super-thick steel plate for marine engineering and a manufacturing method thereof. The steel contains 0.08% to 0.15% of C, 0.20% to 0.55% of Si, 0.80% to 1.35%of Mn, less than or equal to 0.01% of P, less than or equal to 0.03% of S, 0.04% to 0.08% of V, 0.015% to 0.45% of Als, 0.003-0.015% of N, 0.50-0.90% of Ni, 0.20-0.40% of Cr, 0.002-0.03% of Mo, 0.02%to 0.05% of Nb, 0.20-0.40% of Cu, less than or equal to 0.04% of Ti, and the balance of Fe and unavoidable impurities. The method employs two-stage controlled rolling, the first-stage rolling temperature is 1100-1150 DEG C, the one-stage finishing rolling temperature is 990-1130 DEG C, the second-stage rolling temperature is 700-780 DEG C, and the final rolling temperature is 680-750 DEG C. The heat treatment method of quenching before sub-quenching is used, and after quenching, the steel plate is tempered, and the steel plate having a thickness of 80-100 mm is obtained. The impact toughnessof a core is more than 200J, and the comprehensive performance is uniform at different positions.

Description

technical field [0001] The invention belongs to the field of iron and steel material preparation, and relates to an ultra-high-strength, thick structural steel plate used in marine engineering, in particular to quenched and tempered EH550 extra-thick steel plate for marine engineering and a manufacturing method thereof. Background technique [0002] In recent years, with people's continuous exploration and development of the ocean field, the steel required for the matching ocean engineering and its research and development and production have become the top priority. Since the service time of the ocean platform is 50% longer than that of the ship, more The increasingly complex marine service environment determines that steel for marine engineering must have high strength, high toughness, fatigue resistance, lamellar tear resistance, good weldability, seawater corrosion resistance, and good cold workability. The traditional steel plates for offshore platforms below 80mm have ...

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Problems solved by technology

[0004] CN201210387796.1 discloses a quenched and tempered high-strength steel plate for large-thickness marine engineering and its production method. Although the thickness has reached more than 100mm, its yield strength is only 475MPa, which cannot meet the demand for ultra-high-strength tempered steel plates for marine engineering steel , and its composition system adopts high C (0.15% ~ 0.17%), high Mn (1.45% ~ 1.60%) system, which is very unfavorable to the subsequent welding performance

[0005] CN201210189994.7 discloses a low-compression-ratio ultra-high-strength steel plate for marine engineering and its production method. It adopts ultra-high Ni content (0.90% to 1.30%) and has a very high alloy composition. The demand for ultra-high-strength steel plates, but its thickness specification is only 25mm, which is far from meeting the needs of modern marine engineering for large-thickness steel plates

[0006] CN201510321655.3 discloses an extra-thick quenched and tempered EH40 steel for marine engineering and its preparation method, which adopts a quenching + tempering heat treatment process, which cannot make the core of the steel plate obtain good impact toughness, although the thickness of the product is 100- 120mm, but the strength level is only 40, which cannot meet the steel index requirements for higher-level offshore platforms

[0007] CN201210545542.8 discloses a method for manufacturing extra-thick steel plates for marine engineering with excellent low-temperature brittle fracture resistance. Although the low-temperature toughness index of -40°C is also reached, the maximum thickness of the product is 80 mm, but the Mn content in the steel is 1.60%, which is not conducive to Subsequent steel plate welding performance, and the strength level is only 36, which cannot meet the requirements of higher-level steel indicators for offshore platforms in terms of thickness specifications and strength levels

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