690MPa-level low weld crack sensitive steel and production method thereof

Abstract

The invention provides 690MPa-level low weld crack sensitive steel and a production method thereof. The steel comprises the following chemical components by weight percent: 0.06-0.08% of C, 0.25-0.30% of Si, 1.60-1.80% of Mn, less than or equal to 0.010% of P, less than or equal to 0.008% of S, 0.010-0.020% of T, 0.30-0.35% of Ni, 0.31-0.35% of Cr, 0.15-0.25% of Mo, 0.020-0.040% of Al, 0.015-0.025% of Nb, less than or equal to 0.02% of V and the balance of Fe and inevitable impurities. Through reasonable component design, Pcm can be ensured to be less than or equal to 0.20; and by adopting two-stage controlled rolling and controlled cooling and a reasonable thermal treatment process are adopted, the tensile strength of the produced steel plate is larger than or equal to 690MPa. The steel provided by the invention is high in strength, and excellent in low-temperature toughness and welding property, and can be used for building construction members such as large-size spherical tanks, hydropower station pressure penstocks and hydroelectric generating sets.

Description

technical field [0001] The invention particularly relates to a high-strength grade steel for pressure vessels, in particular to a 690MPa grade low welding crack sensitivity steel and a manufacturing method thereof. Background technique [0002] With the development of large-scale and high-parameterization of gas storage tanks and pressure steel pipes, the demand for steel for high-strength pressure vessels is increasing year by year, and the research and development of higher-strength grade steel is becoming increasingly urgent. Domestically produced and widely used 610MPa-grade quenched and tempered high-strength steel for spherical tanks can no longer meet the needs of development. At present, many units have begun to develop low-welding crack-sensitivity steel with a tensile strength of 690MPa for the construction of 10,000m 3 The above-mentioned large-scale natural gas spherical tanks, pressure steel pipes of hydropower stations, volutes of hydropower units and other co...

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Problems solved by technology

[0004] (1) Patent Publication No. CN 101096378A "Steel Plate with Low Welding Crack Sensitivity and Its Production Method", using a three-stage controlled rolling process, the rolling process is complicated, and the tensile strength is low. The tensile strength of the example is 665MPa;

[0005] (2) Patents CN 1932063A "High Strength Low Welding Crack Sensitivity Steel Thick Plate and Its Production Method", CN 1932064A "Large Input Energy Low Welding Crack Sensitivity Thick Steel Plate and Its Production Method", CN101476080A "A Low Welding Crack Sensitivity Tempered and tempered high-strength steel plates and their manufacturing methods", all of which are low-weld crack-sensitive steel plates with a tensile strength of 610MPa, and their strength is low;

[0006] (3) Patent No. CN 101418418A "Steel Plate with Yield Strength 690MPa and Low Crack Sensitivity and Its Manufacturing Method" involves high-strength structural steel, using ultra-low C (0.03-0.06%), high Mn (1.30-2.00%), high Nb (0.03~0.08%) and high V (0.04~0.12%), and added a certain amount of B, the steel plate produced by the controlled rolling and controlled cooling process has high strength and low welding crack sensitivity, but the steel rolling process Complicated, and the cooling rate after rolling is relatively high, which requires high cooling equipment

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