Steel plates for 355MPa-level easy-to-weld ocean platform and production process of steel plates

Abstract

The invention belongs to the technical field of constructional steel for ships and ocean engineering and in particular relates to steel plates for a 355MPa-level easy-to-weld ocean platform and a production process of the steel plates. Two steel plates of which the thickness specifications are [6-40]mm and [40-60]mm are comprised, wherein the steel plate with the thickness specification of [6-40]mm comprises the following chemical components in percentage by mass: 0.10-0.15 percent of C, 0.20-0.50 percent of Si, 1.20-1.50 percent of Mn, not more than 0.015 percent of P, not more than 0.005 percent of S, 0.020-0.050 percent of Nb, 0.010-0.050 percent of V, 0.008-0.020 percent of Ti, 0.015-0.055 percent of Als, not more than 0.43 percent of Ceq, not more than 0.23 percent of Pcm and the balance of Fe and inevitable impurities; and the steel plate with the thickness specification of [40-60]mm comprises the following chemical components in percentage by mass: 0.10-0.15 percent of C, 0.20-0.50 percent of Si, 1.30-1.60 percent of Mn, not more than 0.015 percent of P, not more than 0.005 percent of S, 0.030-0.060 percent of Nb, 0.020-0.060 percent of V, 0.008-0.020 percent of Ti, 0.015-0.055 percent of Als, not more than 0.12 percent of Nb+V+Ti, not more than 0.43 percent of Ceq, not more than 0.23 percent of Pcm and the balance of Fe and inevitable impurities. According to the production method, the steel plates for the easy-to-weld ocean platform are produced by adopting low Ceq, low Pcm, Nb as well as V and Ti microalloy components and a normalizing heat treatment process and are lower in production cost, even in mechanical property and favorable in welding property.

Description

technical field [0001] The invention belongs to the technical field of structural steel for ships and marine engineering, and in particular relates to a 355MPa grade easy-to-weld steel plate for offshore platforms and a production process thereof. Background technique [0002] With the rapid growth of China's economy for more than 30 years, the domestic shipbuilding and marine engineering equipment manufacturing industry has developed rapidly. Shipbuilding completions, new orders, and orders in hand have all ranked among the top in the world for many years, and the offshore engineering equipment manufacturing industry has also achieved considerable development. With the continuous development of ocean development, offshore oil development is gradually moving towards the deep sea, and the demand for steel for offshore platforms has further increased. In the next few years, the demand for steel plates for offshore platforms is promising. [0003] The technical indicators of ...

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Problems solved by technology

[0005] Therefore, the patent application with application number 201210564686.8 discloses a 355MPa grade low welding crack sensitivity steel plate, its chemical composition mass percentage is: C 0.09 ~ 0.13%, Si 0.25 ~ 0.35%, Mn 1.20 ~ 1.50%, P ≤ 0.015% , S ≤ 0.005%, Al 0.025 ~ 0.04%, Nb 0.02 ~ 0.05%, Ti 0.01 ~ 0.03%, Cu 0.10 ~ 0.3%, Ni 0.10 ~ 0.3%, the rest is Fe and unavoidable impurities; using top-bottom combined blowing converter smelting, and use low-nickel pig iron with nickel; the thickness specification of the continuous casting slab is 400mm, and the width is 1800-2400mm; the steel plate adopts two-stage controlled rolling + controlled cooling + normalizing treatment. Adding Cu to the alloy will easily cause star-shaped cracks on the surface of the slab and the steel plate, while the price of the Ni alloy is more expensive, the cost is higher, and there is no cost advantage

[0006] The patent application with the application number 201110358089.5 discloses a method for manufacturing a 355MPa low-alloy steel plate with a welding crack sensitivity index less than 0.23. The chemical composition weight percentage control range of the steel plate is: C: 0.10-0.13, Mn: 1.45-1.53 , Si: 0.20 ~ 0.30, Nb: 0.030 ~ 0.040, V: 0.060 ~ 0.070, Ti: 0.005 ~ 0.015, Al: 0.020 ~ 0.050, P: ≤ 0.013, S: ≤ 0.003%, the rest is Fe and unavoidable impurities ; and the chemical composition of the steel plate meets the welding crack sensitivity index Pcm=C+Si / 30+Mn / 20+Cu / 20+Ni / 60+Cr / 20+Mo / 15+V / 10+5B by weight percentage ≤ 0.23, but the above-mentioned patent application adds more V, according to the online survey of Fanyu Consulting, the price of V fluctuates at 85,000 yuan / ton, and the cost is relatively high. More, which further increases the cost, which is not conducive to mass production