High-strength and high-toughness steel plate for 630MPa-grade tempered low-temperature spherical tank and manufacture method thereof

Abstract

The invention discloses a high-strength and high-toughness steel plate for a 630MPa-grade tempered low-temperature spherical tank and a manufacture method thereof. The high-strength and high-toughness steel plate comprises the following components by weight percent: 0.07-0.09% of C, 0.15-0.25% of Si, 1.40-1.50% of Mn, less than or equal to 0.008% of P, less than or equal to 0.001% of S, 0.30-0.40% of Ni, 0.16-0.20% of Mo, 0.015-0.025% of Nb, 0.02-0.06% of V, 0.007-0.015% of Ti, less than or equal to 0.0030% of O, less than or equal to 0.0040% of N, 0.020-0.040% of Al, 0.0005-0.0030% of Ca, and the balance of Fe and unavoidable impurities, wherein the welding cold crack sensitivity coefficient Pcm value is 0.16-0.20% and the hot crack sensitivity coefficient Psr is less than or equal to 0.00%. By adopting the high-strength and high-toughness steel plate, the safety of the spherical tank integral structure is guaranteed, the yield strength of the steel plate is greater than or equal to 510 MPa, the tensile strength is greater than or equal to 630 MPa, the ductility is greater than or equal to 18%, the Charpy notch ballistic work average value in the plate thickness 1/4 part at -50 DEG C is greater than or equal to 2000 J, the single value is greater than or equal to 150 J, the Charpy notch ballistic work average value in the plate thickness 1/2 part at -50 DEG C is greater than or equal to 150 J, the single value is greater than or equal to 100 J, and the steel plate nil ductility transition temperature (NDTT) is less than or equal to -50 DEG C.

Description

technical field [0001] The invention relates to steel for low-temperature spherical tanks, in particular to high-strength and high-toughness steel plates for 630MPa-level quenched and tempered low-temperature spherical tanks and a manufacturing method thereof. Background technique [0002] Low-temperature spherical tanks containing ethylene and propylene in the petrochemical industry are generally made of thick steel plates with a tensile strength greater than or equal to 610MPa and low welding crack sensitivity. The steel plate is cut and blanked by flame first, then pressed into ball petals, and then the ball petals are tailor-welded. After welding, the whole spherical tank needs to be heat treated after welding at 570-590 ° C for 2-6 hours to eliminate the heat generated during welding. of stress. Due to the particularity of the manufacture of spherical tanks and the service characteristics of spherical tanks under a certain pressure after being filled with medium, in ad...

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Problems solved by technology

[0011] For example, Chinese patent CN102876999A discloses a steel plate for quenched and tempered low-temperature pressure vessel and its preparation method, its P content is ≤0.015%, which is not low enough, the steel quality is not pure enough, contains Cr and the content of Ni, Mo and Nb is high, The cost is not economical, and the chemical composition has no limit requirements for low crack susceptibility index Pcm

[0012] Chinese patent CN102936695A discloses a high-strength low-temperature pressure vessel steel plate and its production method. The upper limit of the C content is higher than 0.09% to 0.15% and there is no requirement for a low welding crack sensitivity index, which is not a low welding crack sensitivity steel; Cr and the contents of Ni, Mo, and Nb are relatively high, and the cost is uneconomical

[0013] Chinese patent CN1396294A discloses high heat input low welding crack sensitivity series steel and its production method, which involves a 60Kg high heat input low welding crack sensitivity steel, its P and S content is not low enough, and the steel quality is not pure; The content of C element can reach up to 0.13%, which does not meet the requirements of GB19189-2011; B is contained in the composition, which is not good for the weldability of the steel plate

[0014] Chinese patent CN103160747A discloses a low welding crack sensitivity off-line quenched and tempered extra-thick steel plate and its manufacturing method. The upper limit of its C content is higher than 0.09%,...

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