Production method for low carbon equivalent ultra-thick steel plate Q420E

Abstract

The invention discloses aproduction method for a low carbon equivalent ultra-thick steel plate Q420E. Steel is prepared from the chemical components in percentage by mass, 0.04% to 0.07% of C, 0.15% to 0.35% of Si, 1.48% to 1.58% of Mn, less than or equal to 0.015% of P, less than or equal to 0.005% of S, 0.02% to 0.03% of Nb, 0.008 to 0.02% of Ti, 0.015% to 0.05% of Al,0.15% to 0.25% of Ni, 0.10%to 0.18% of Cu, 0.10% to 0.18% of Cr, less than or equal to 0.40% of Ceq, and the balance of Fe and unavoidable impurities.The production method for the low carbon equivalent ultra-thick steel plateQ420E comprises the steps of smelting, heating, rolling, relaxing, and cooling. According to the production method for the low carbon equivalent ultra-thick steel plate Q420E,a continuous casting billet is utilized to produce a high toughness steel plate with a low-temperature impact requirement above minus 40 DEG C, and the maximum thickness can reach 150 mm; and the compression ratio limitationof a traditional TMCP technology of rolling an ultra-thick steel plate by a continuous casting billet is broken through, the structure property of a thick gauge steel plate is improved through a structure adjusting and controlling technology, the heat treatment does not need to be added, the processesare simple, alloy and production cost is lowered, and the production method can be widely appliedin thick plate manufacturing in multiple fields, such as shipbuilding, maritime work, wind electricity, bridges, construction, and engineering machinery.

Description

technical field [0001] The invention belongs to the technical field of metal material smelting, and in particular relates to a production method of a low-carbon-equivalent extra-thick steel plate Q420E. Background technique [0002] Extra-thick steel plates generally refer to steel plates with a thickness of more than 60 mm. In the known technology, the TMCP process can generally only be used for rolling high-toughness steel plates below 60 mm in size and requiring impact at -40°C. Due to the limitation of the compression ratio, if the extra-thick steel plate is produced by the TMCP process, the original austenite grains will not be fully recrystallized and refined during the rolling process, and the structure is generally coarse and the toughness will deteriorate. Especially for the ultra-thick structural steel plate of Q420E level, due to the relatively high strength and toughness requirements, it is generally produced by die-casting technology at present. In order to ens...

AI Technical Summary

Problems solved by technology

Due to the limitation of the compression ratio, if the extra-thick steel plate is produced by the TMCP process, the original austenite grains will not be fully recrystallized and refined during the rolling process, the structure is generally coarse, and the toughness will deteriorate

Especially for the ultra-thick structural steel plate of Q420E level, due to the relatively high strength and toughness requirements, it is generally produced by die-casting technology at present. In order to ensure the strength of the steel plate, high C and high Mn content are used. A large amount of Cr, Mo, Ni, V and other elements are added to ensure the strength and toughness matching of extra-thick plates by improving the hardenability of the steel plate and adding quenching and tempering heat treatment process, which not only increases the production cost and energy consumption, but also prolongs the Production and delivery cycle, while the carbon equivalent Ceq of the steel plate is relatively high, which is not conducive to welding

[0003] Chinese patent CN 104018071 A discloses a "production method of low-carbon equivalent high-toughness Q420E steel plate". This method adopts the traditional TMCP process to produce Q420E steel plate. For the production of extra-thick steel plates

Chinese patent CN 102776443 A discloses "a 420MPa grade low-alloy high-strength extra-thick steel plate and its manufacturing method", which is smelted by electroslag remelting, followed by normalizing heat treatment after rolling to produce Q420D-grade extra-thick steel plate. The production process Complex, long production cycle, high alloy cost, and high carbon equivalent Ceq

Chinese patent CN 103540848 A discloses "A 420MPa normalized steel plate for extra-thick specification structure and its manufacturing method". Higher, Ceq is higher, at the same time, this method cannot get rid of the limitation of compression ratio, and the continuous casting slab with a thickness of 400mm can only produce products with a maximum thickness of 120mm

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