Ultralow-temperature, large-diameter and WPHY80-level steel plate special for three-way pipe fitting and production method of steel plate

Abstract

The invention belongs to the technical field of low-alloy and high-strength pipeline steel and particularly relates to an ultralow-temperature, large-diameter and WPHY80-level steel plate special for a three-way pipe fitting and a production method of the steel plate. The steel plate comprises, by weight percentage, 0.04-0.06% of C, 0.50-0.80% of Si, 1.40-1.80% of Mn, not more than 0.008% of P, not more than 0.002% of S, 0.08-0.12% of Nb, 0.04-0.06% of Ti, 0.30-0.40% of Mo, 0.12-0.20% of Cu, 0.30-0.40% of Ni, not more than 0.50% of Cr, 0.050-0.060% of V, not more than 0.0005% of B, and the balance of iron and inevitable impurities. Under the premise that field production efficiency is increased, the produced steel plate is stable in performance, the steel plate has excellent low-temperature drop weight tear test performance: -25 DEG C SA%>=90% and excellent Charpy impact performance: -60 DEG C Charpy impact energy>=260J, -80 DEG C Charpy impact energy>=210J.

Description

technical field [0001] The invention belongs to the technical field of low-alloy high-strength pipeline steel, and in particular relates to a special steel plate for ultra-low temperature large-diameter WPHY80 grade tee pipe fittings and a preparation method thereof. Background technique [0002] With the development of pipelines towards high transmission efficiency, low energy consumption, low cost, large diameter, large thickness and high strength and toughness, the geological environment of pipeline steel service is becoming more and more complex, and the quality requirements for pipeline steel are also getting higher and higher. In order to transport liquid or gas resources such as oil and natural gas smoothly and completely, various pipelines must be used. In addition to steel pipes for straight pipelines, a large number of accessories for straight pipes are also used in pipeline laying. Tee pipelines are important as oil and gas transmission pipelines. The components a...

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Problems solved by technology

[0011] The composition and welding process of a submerged arc welding wire for X80 pipe fittings in the prior art aims to provide a high-toughness submerged arc welding wire suitable for welding the parent pipe of X80 pipe fittings, which is conducive to efficient production in industry, but its carbon content is 0.10 -0.14%, the high carbon content will promote the formation of bainite or even martensite in the weld, resulting in a decrease in the crack resistance and toughness of the weld; in the prior art, a low-temperature resistant steel pipe of X80 steel And the welding wire for pipe fittings is mainly aimed at a kind of X80 steel pipe submerged arc automatic welding wire, which does not involve ultra-low P treatment and low carbon treatment, nor does it involve steel plate smelting from pure steel, high-pressure water phosphorus removal and two-stage rolling cooling It is difficult to meet the toughness and on-site welding requirements of ultra-low temperature steel plates without involving the overall system control method of steel plates.

[0012] In the prior art, there is an X80 steel and the manufacturing method of the low-temperature-resistant pipe fittings and pipe fittings; after the pipe fittings are formed, the quenching and tempering process is finally adopted, the quenching temperature is 900-1050°C, the tempering temperature is 520-650°C, and the cooling If the speed is greater than 15°C / s, the quenching temperature and tempering temperature are high, which will easily lead to a sharp deterioration of the weldability of the steel plate after heat treatment, and there is no slow cooling after heat treatment, which will easily generate residual stress inside the steel plate, and it is difficult to ensure that the steel plate is in an ultra-low temperature state. Excellent welding toughness; the tempering time of 2 to 3 hours is too long, which is not suitable for efficient industrial production