Low-carbon-equivalent low-temperature-usable high-thickness toothed rack steel and manufacturing method thereof

Abstract

The invention relates to low-carbon-equivalent low-temperature-usable high-thickness toothed rack steel and a manufacturing method thereof. The toothed rack steel comprises the following chemical components: C, Si, Mn, P, S, Cr, Mo, Ni, Cu, Al, V, N, B and the balance of Fe and impurity elements, wherein the carbon equivalent CEV is less than 0.65. The manufacturing method sequentially comprises the steps of KR molten iron pretreatment, converter smelting, LF and RH refining, continuous casting, continuous casting blank heating, rolling, thermal refining and the like. The thickness of the toothed rack steel plate manufactured by the invention can be up to 152.4mm, the yield strength is above 690Mpa, the tensile strength is 790-930MPa, the elongation percentage is 319%, and the Charpy impact energy at -60 DEG C is more than 100J. Besides, the toothed rack steel is favorable in comprehensive mechanical property, convenient in production process and low in cost.

Description

technical field [0001] The invention relates to a large-thickness rack steel with low carbon equivalent and low-temperature use and a manufacturing method thereof. Background technique [0002] The rack is a key component in the jack-up offshore platform. It is required to have high strength and high low-temperature toughness in the case of large thickness. At the same time, it also has a low carbon equivalent to meet the requirements of easy welding in the manufacturing process of the offshore platform. . Generally, the yield strength of rack steel is required to be 3690MPa, the tensile strength is in the range of 790~930MPa, the elongation is 314%, and the Charpy impact energy at -40°C (or 37°C) at 1 / 4 thickness of the steel plate is 3 69J, and the Charpy impact energy at -27°C at 1 / 2 thickness of the steel plate is 369J. However, with the development of offshore oil and gas exploration and exploitation in cold seas, in addition to the above-mentioned tensile properties ...

AI Technical Summary

Problems solved by technology

However, this technology can only manufacture steel plates with a maximum thickness of 120mm, and cannot manufacture rack steel plates for large-thickness offshore platforms with a thickness of 127mm to 152.4mm, which is in high demand.

In addition, the steel plate for marine engineering disclosed in 103014541A has a high carbon equivalent. Even for a steel plate with a thickness of only 120 mm, its carbon equivalent CEV ( = C + Mn / 6 + (Cr + Mo + V) / 5 + (Cu + Ni) / 15) are about 0.73, which makes the welding difficulty significantly increased and cannot meet the requirements of easy welding

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