A kind of ultra-high-strength tempered eh690 extra-thick steel plate and its manufacturing method

Abstract

The invention discloses an ultra-high-strength tempered EH690 extra-thick steel plate and a manufacturing method thereof. Contained in steel, C: 0.10% ~ 0.17%; Si: 0.25% ~ 0.45%; Mn: 0.80% ~ 1.30%; S≤0.003%; P≤0.010%; V: 0.04% ~ 0.08%; Als: 0.03% ~0.05%; N: 0.003% ~ 0.015%; Ni: 1.40% ~ 1.80%; Cr: 0.60% ~ 1.00%; Mo: 0.30% ~ 0.50%; Nb≤0.05%; Cu: 0.25% ~ 0.50%; Ti ≤0.02%, the balance is iron and unavoidable impurities. The heating temperature is 1160-1180°C, the starting rolling temperature is 1100-1120°C, the controlled rolling temperature is 880-920°C, the final rolling temperature is 780-830°C, and the ratio of casting slab thickness to steel plate thickness is ≥3:1. The heat treatment adopts secondary quenching + tempering, the thickness of the finished steel plate is 60~120mm, the yield strength is ≥690MPa, and the low temperature toughness is good.

Description

technical field [0001] The invention belongs to the field of iron and steel material preparation, in particular to an ultra-high-strength and thick structural steel plate used in ships and marine engineering, in particular to quenched and tempered EH690 extra-thick steel plate and a manufacturing method thereof. Background technique [0002] In recent years, with people's continuous exploration and development of the marine field, the steel required for supporting ships and marine engineering and its research and development and production have become the top priority, because the service life of offshore platforms is 50% longer than that of ships , The changeable and 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 can no...

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Problems solved by technology

[0004] The invention patent of CN201210531442.X proposes a production method of ultra-high-strength steel plates for marine engineering with low compression ratio and thickness specifications. Although the yield strength reaches 690MPa, its maximum thickness is only 80mm, which cannot meet the requirements of ultra-high-strength tempered steel plates for marine engineering steel. needs

[0005] The invention patent of CN102400043 proposes a steel plate for marine engineering and its production method. Although the thickness specification is more than 100mm, it meets the needs of ultra-high-strength steel plates for marine engineering in terms of thickness specifications, but its yield strength is only 460MPa, which is far from meeting the requirements. Requirements for the strength index of large-thickness ultra-high-strength steel plates in modern ocean engineering

[0006] The invention patent of CN201210189994.7 proposes a low-compression-ratio ultra-high-strength steel plate for marine engineering and its production method. It adopts the traditional one-time quenching + tempering heat treatment process. This process cannot make the core of the steel plate obtain good impact toughness, although the yield The strength has reached 690MPa, but its maximum thickness is only 30mm, which cannot meet the demand for ultra-high-strength tempered steel plates for marine engineering steel

[0007] The invention patent of CN201210545542.8 proposes a method of manufacturing extra-thick steel plates for marine engineering with excellent low-temperature brittle fracture resistance. Although it also reaches the low-temperature toughness index of -40°C, the maximum thickness of the product is 80mm, and the Mn content reaches 1.60%. The 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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